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Seven earth-sized planets discovered circling a star 39 light years from Earth (nature.com)
2256 points by ngoldbaum on Feb 22, 2017 | hide | past | web | favorite | 704 comments

My favourite part of the press release:

> The planets also are very close to each other. If a person was standing on one of the planet’s surface, they could gaze up and potentially see geological features or clouds of neighboring worlds, which would sometimes appear larger than the moon in Earth's sky.

> In contrast to our sun, the TRAPPIST-1 star – classified as an ultra-cool dwarf – is so cool that liquid water could survive on planets orbiting very close to it, closer than is possible on planets in our solar system. All seven of the TRAPPIST-1 planetary orbits are closer to their host star than Mercury is to our sun.


> The planets also are very close to each other. If a person was standing on one of the planet’s surface, they could gaze up and potentially see geological features or clouds of neighboring worlds, which would sometimes appear larger than the moon in Earth's sky.

this reminds me of one my favorite films ever. it is just four minutes long


Have you seen Reid Gower's Sagan Series?


It similarly combines HD cinematography with Carl Sagan's narration. It's not CG like this, but the overall quality is extremely high (at least after the first chapter).

If you liked this, you'll probably also like MelodySheep's Symphony of Science series.


This brought me to tears, literally... There is a beauty to the words that is hard to describe other than to say it gives "meaning" (for lack of a better word) to life on this rock.

Another good video is Sagan's "Pale Blue Dot" https://www.youtube.com/watch?v=4PN5JJDh78I&feature=youtu.be

It reminded me of the end (spoiled by the poster, of course) of the (somewhat obscure) NZ sci-fi flick "The Quiet Earth":


Wanderers is indeed excellent.

See also: the timelapse footage of the sky from the VLT, Paranal. Just thinking about it gives me vertigo.


I just watched this twice. It made me smile, hopeful, and happy. Thank you.

It reminds me of Land and Overland by Bob Shaw:

"The setting for the trilogy is a pair of planets, Land and Overland, which orbit about a common centre of gravity, close enough to each other that they share a common atmosphere."

They don't share a common atmosphere, but I guess the delta required for interplanetary transfer is really low.

I watched this 10 times in a row. It gave me shivers every time...

Thank you, this is truly amazing. For all the people interested in any way in space - watch this :)

Thank you for this. Awesome.

It actually reminded me of Rick and Morty Season 2 last episode.

That was amazing

Wonderful and inspiring. I loved the narration from Carl Sagan. One of the greatest.

I was very stressed and watching this calm me down. Thanks

I get a little choked up every time I watch this.

I was very skeptical but pleasantly surprised.

Reminds me of the movie Melancholia.

Great film!

So, basically, this is cooler than just about any world that's been depicted in sci-fi.

I guess J.J. Abrams is somewhat forgiven for this, then:

http://vignette4.wikia.nocookie.net/startrek/images/2/29/Vul... [edited for direct .jpg]

I always thought that Firefly's scenario of a bunch of Earth-like worlds in close enough proximity to have regular trading ships flying between them was unrealistic. Now, not so much. This system even fits in with the "Abandon Earth en-mass, move to new set of worlds" backstory.

So, what did J.J. know, and when did he know it? And for that matter, how did he know?

Just making sure, but I hope you know that JJ Abrams had literally absolutely nothing to do with Firefly and wasn't even tangentially related to its creation nor production.

Also, I'm relatively positive that JJ (in the sci-fi works he actually, well, worked on), himself, knew nothing (see Armageddon for sources) and that his script supervisors dealt with any discrepancies with reality JJ had.

Man, I feel dumb. Yeah I meant Joss Whedon. Too many J's in sci-fi I like, I guess.

Corrections aside, it is an interesting observation that Firefly is less outlandish with this discovery (not a criticism, Firefly is optimized for fun, not scientific plausibility). Still, assuming light speed travel, Firefly's inhabited planets are still a heck of a lot closer, since the crew doesn't seem to noticeably age between the half dozen or so star systems that they visit, and don't appear to have any kind of tech to reversibly[1] halt their metabolisms.

[1] the reversibility it the hard part. Tech for halting metabolic processes irreversibly has been around for quite some time ;)

> Still, assuming light speed travel, Firefly's inhabited planets are still a heck of a lot closer, since the crew doesn't seem to noticeably age between the half dozen or so star systems that they visit, and don't appear to have any kind of tech to reversibly[1] halt their metabolisms.

Closer than what? This system is significantly smaller than Firefly's. Or do you mean closer than this system is to Earth? Don't worry about that, since in Firefly it's one super-system with five main stars. http://i.picresize.com/images/2013/02/06/BMhCv.jpg It's about 55 light hours across.

I never realized Firefly was in a super-system. Gravity would rip that thing apart in an instant.

They actually did numeric simulations of that system, and it seems to be stable for several millenia at least (their entire simulation time).

> Firefly's inhabited planets are still a heck of a lot closer, since the crew doesn't seem to noticeably age between the half dozen or so star systems that they visit

The 'systems' in Firefly are really all one star system. The system includes a central star orbited by planets, four other stars, and a host of "protostars" (they really mean brown dwarves). I've tried, and can't imagine a scenario where, even if such a system could form, that it could be configured in this way. The barycenter of the masses of this system can't possibly remain in the central star indefinitely, for starters. And the whole thing sounds hostile to planets - I imagine them being thrown out of the system constantly. But if you accept that, and you accept travel at some fraction of c, then you wouldn't expect them to age much like they would traveling between systems.

Proxima Centauri have a earth mass planet : https://en.wikipedia.org/wiki/Proxima_Centauri_b

The Firefly system is one in which stars are orbiting stars are orbiting stars, and among these stars are many many planets and moons. Presumably the distances involved here can be traveled in a matter of days or weeks at some fraction of c. So, they're fairly close.

In contrast, Proxima Centauri orbits from a distance of about a quarter lightyear, and we've found a single planet orbiting very tightly. We've also found a single planet around Alpha Centauri B, also orbiting very closely. There may be more we haven't found, but probably not nearly as many as in the Firefly system. Firefly seems to use the idea that more stars mean more planets, but more stars and planets during formation means more chaos, more things to swallow up or rip apart planets, and more mass to throw them out of the system.

I don't think the Firefly system is necessarily impossible. You can even construct models such that the white star is at the focus of all other orbits (you know, if you're the Alliance and you need to do that for political reasons). (An Earth-centric model of our solar system needn't necessarily be wrong in terms of its ability to predict the position of bodies in the solar system - It's just needlessly difficult and convoluted.) I just think the Firefly system is highly improbable.

> assuming light speed travel, Firefly's inhabited planets are still a heck of a lot closer, since the crew doesn't seem to noticeably age between the half dozen or so star systems

If you travel at light speed from your own point of view you arrive instantly due to time dilation, so even if it takes years according to an outside observer (because the distance you're travelling is light years) you wouldn't age at all.

From a photons point of view, it is emitted and absorbed by its destination instantly.

Ah, yes. Forgot all about time dilation effects. In my defense, it was a pretty off the cuff response. Also, I would assume they aren't meant to be literally traveling at exactly light speed, but I don't know the relevant equations to figure out how that impacts my comment. Clearly, in this area, I'm a dilettante at best.

>Still, assuming light speed travel, Firefly's inhabited planets are still a heck of a lot closer, since the crew doesn't seem to noticeably age between the half dozen or so star systems that they visit

My understanding is that Firefly does not have FTL travel at all, in fact that makes it rather unique among spaceship sci-fi. Also, they're in a single (though very large with multiple stars) system. They get around quickly because their ships are a lot faster than our slow-ass chemical rockets, but they're still traveling at sublight speeds, which is why it takes days or weeks to get places, instead of mere minutes (for example, at lightspeed, it would take less than 6 hours to get to Pluto). Notice that, in the show, they took paying passengers, and it took a fair amount of time to get between the "outer worlds". It was a lot like cargo ships of yesteryear, rather than modern airplanes, as far as travel time. They don't have tech to halt their metabolisms for the same reason we don't: they haven't invented it yet.

Joss Whedon is the name you're looking for, not JJ Abrams.

The worlds in Firefly were explicitly described as having been terraformed to be Earth-like (masses aside).

Except bigger, with multiple planets in the sky at once.

Firefox tries to download this file

Apologies, sloppy link-copying. Should be pointing to the .jpg now.

It's a webp. Firefox doesn't support those.

What? Worked just fine for me.

In which Firefox version?

51.0.1 32bit. Don't ask me why I'm running 32bit FF, this is news to me as well.

I'd be more inclined to ask why it worked for you in that exact version, but not for me in the very same one. (Mine might be 64-bit, but I can't see that making a difference here.)

I went to investigate for curiosity's sake but OP changed the link on us!

Worked for me in Firefox for Android (53, Aurora build).

Maybe it's a prerelease feature, or maybe Firefox is falling back on a capability that at least some desktop OSes don't have.

works on Arch Linux FF

It doesn't work in Microsoft Edge either (yup I use it).

Is this taboo? I also use Edge and find it great.

I don't see many people using Edge. I mostly don't have any problems now that it has extensions for ad block and lastpass. Sometimes opening a new tab just mysteriously doesn't work (it sits with the tab open doing nothing) or the website barely works without Edge freezing up (CarMax.com).

The battery life is really good though.

Doesn't work on IOS either (chrome specifically).

One of the games I'm working on (a sci-fi mech and space combat action rpg) actually is set in a solar system like this. Cool to see one in reality relatively close by! I think it provides a lot of interesting situations allowing for basically a "space opera in a solar system".

*Hollywood sci-fi

You get a lot more crazy worlds in written sci-fi. You can start with the Culture orbitals, some of the Commonwealth Saga worlds or Alastair Reynolds' inhibitors. If you count a neutron star with life on it, you get dragon's egg which is a must-read.

Sounds like you haven't read The Three Body Problem (which is a shame, you should totally check it out).

I was essentially thinking the same thing. I wonder if an elevator could be built between all of them?

They are still in separate orbits so the straight line between any two varies greatly in length... not to mention intersecting the star regularly.

Regular shuttles for interplanetary travel timed with periodically favorable orbital positions?

At that distance, gravity must be really fun. Tides are not only for water, such tides can also change the height of mountains, the balance of high-rise buildings, infer on volleyball rules, make you fart because of changes in atmospheric pressure, or... be leveraged to generate electricity. Those guys have simili-infinite energy at human scale.

Would they? I mean, we can see geological features on our moon, and our tides are orders of magnitude away from being rock-tearing events. I mean, the moon is small, but... how close do these planets approach, anyway?

The moon is not that small, it is 27% of earth's size. Any other satellite in the solar system is way smaller compared to the planet they orbit. I dare to say that earth and moon are twin planets instead of a planet and a satellite.

Unless you are excluding Pluto deliberately for not being "a planet", its moon Charon has half the diameter of Pluto. They are even both orbiting a common center of gravity outside Pluto.



> The Moon is about 2% of Earth's mass, not 27%.

2% of mass, yes, but also 27% of the diameter.

You are both right.

My first reaction was WTF?

Then 0.27^3 = 0.0197

And then, only 60% as dense (no core) so 0.0119 :)

One of my scale numbers is, everything between Jupiter and the Sun masses less than 2 Earths -- Venus, Mars, Mercury, the Moon, and all the asteroids mass less than the Earth.

And only just barely! You get to around 99% of the Earth's mass with the rest of the inner solar system.

All of the other rocky bodies in the solar system give you another 10% of Earth's mass out to Pluto and another 10% beyond.

>One of my scale numbers is, everything between Jupiter and the Sun masses less than 2 Earths -- Venus, Mars, Mercury, the Moon, and all the asteroids mass less than the Earth.

Is that correct? Venus alone is about 90% the size of Earth, and Mars roughly 33%. It really seems like all those bodies put together should be greater than 1 Earth mass (but less than 2 Earth masses).

That's size, not mass.

Venus is about 81% Earth's mass, and Mars is only a little over 10%. Mercury gets you another 5.5%, the Moon (as above) another 1.2%, and the asteroids are negligible.

In the outer solar system, it's basically all the Galilean Moons + Titan.

ETA: Hmm, or maybe those are surface gravity numbers you're thinking of?

Yep, I was roughly equating mass with surface gravity, which I see now is incorrect.

I do find it really interesting and a little mind-boggling that the Moon, as huge as it is, with a good 1/6 of Earth's gravity, only has 1.2% of Earth's mass. Same with Mars: a good 1/3 of Earth's gravity, but a mere 10% of its mass. I really thought there'd be more direct correlation between mass and gravity than that. Of course, surface gravity is related to mass with both density and radius, but still, I would have assumed that the densities of these bodies would have been rather similar, as they're all small, rocky worlds.

The densities do vary by almost a factor of 2 (~3 g/cc for the Moon, 5.5 g/cc for the Earth), but the larger problem is that surface gravity is a linear function of the radius, and mass is the cube of the radius.

Consequently, the mass of an object with a given surface gravity is inversely proportional to the square of the density. If the Moon were the same density as the Earth, and had the same surface gravity as it does now, it'd actually mass less than it does now -- and Uranus, despite have 15x the mass of Earth, has a lower surface gravity, because its density is so low.

The rule of thumb for space is "any way your intuition can be wrong, it will be wrong". :-)

You just blew my mind ;)

What do we know about the gas giants' cores?

Gas giant cores are weird. Based on models of solar system formation, we're like, pretty sure they started with rocky (or icy) cores that were dozens of times bigger than Earth. But we're not sure they're still there.

Due to the intense conditions inside a gas giant, we're not sure if they still have a rocky core, or if the cores have liquified or even convected away to mix with the gasses.

So the answer could be "there are dozens of times the Earth's mass worth of rocky material inside gas giants" or "there is no rocky material inside gas giants", or anywhere in-between. We need more detailed study of the gas giants before we can answer that question.

Models of solar system formation also suggest the Kuiper belt started with dozens of times Earth's mass, but we only see about 10% there now, and we only have pretty good guesses about what happened. (I mean, it almost certainly got ejected, but the "why" is harder.)

Thanks. I asked because searching seemed to be telling me that we have only theoretical arguments about gas giants' cores. That surprised me at first, but then I realized how little data we probably have. Basically, mass and its distribution, plus spectroscopic data about surface composition, right?

Juno is hopefully going to tell us more :)


Close enough that the perturbations these planets induced in one another's orbits allowed the team to estimate their masses at between 0.4 and 1.4 Earth-masses. In astronomical terms, that's very close.

So it possible to see Avatar like suspended rocks ? Somewhat orbiting some lagrangian point, which is very close to surface.

The Moon is about 2% of Earth's mass, not 27%.

One of the callers (a biologist, so not a crackpot) on TV suggested that given how close the planets were, he wondered if it were possible for there to be cross contamination between the planets given how close they are to each other. He referred to them being part of the same "ecosystem." I'm not sure how feasible that is as a non-astrobiologist, but it is an interesting idea.

Very likely, since this happens between Mars and Earth:


Fascinating! Would vira or bacteria beable to survive travelling from Earth to Mars in or on a rock or vice versa?

Tardigrades do survive in space: https://en.wikipedia.org/wiki/Tardigrade

Roughly quoting Neal de Grasse Tyson: Since so many bacteria survive outer space there is a good chance it's because of - yes - survivor bias. If only because early earth was bombarded so often that fragments of the planet with microbes took of in a meteor strike and returned home after a while in space.

Short answer: almost certainly yes, although i presume this is an improbable event.

It's not that improbable. They've found meteorites on Earth that have been identified as having come from Mars based on their mineral contents.

Sure, I was referring to the part where the microbe survives the initial blast, the passage through space, reentry, and landing, and happens to land in a spot where it can survive.

According to some research, microbes survival in meteorites is very likely (if they exist)


I know enough biology to be skeptical of papers like that (although, I admit I was skeptical when papers from the 50s predicted interplanetary mass transport, and didn't change my mind until we found Martian meteorites). I'd like to see actual evidence of this.

I actually think the rock getting into space with the microbe embedded in it is not that unlikely (many rocks in the earth are laced with bacteria), nor the space transport. I think the excessive heat of rentry, the force of impact, and the difference in target ecosystems are what are going to kill the microbes.

Possible, but cross-section for collision is way way smaller in the Earth-Mars system. Cross-section goes as r^-2 so the closer the bodies, the 'way better' it is.

IIRC, that is a serious hypothesis for how life began on earth, seeded from elsewhere (maybe not Mars).

But certainly someone here knows more than I do about it ...

The theory is called Panspermia


Considering the time scales involved, it wouldn't surprise me if multiple planets around nearby stars happened to be seeded with earth based bacterial/archaea life.

One of the presenters is an old friend from college. Folks were offering him money to mention "Zod, our Galactic Overlord" on the air. I guess that didn't happen?

No unfortunately, I don't think they did. That would have been hilarious.

The survivability of several organisms has been actually tested https://en.wikipedia.org/wiki/List_of_microorganisms_tested_...

There has been and continues to be cross-contamination between Venus, Earth, and Mars, so it seems likely that planets much closer together, and passing each other more frequently would have more 'communication' of materials.

Continues to be...? Outside of human action, what's the vector?

My understanding is that it is mostly due to solar wind, meteorite impacts, and various other infrequent events.

powerful meteor strikes spreading debris out of orbit.

And the debris isn't heated enough to be sterilized.

Gene Wolfe mined this idea for some of his science fiction works, except it was alien life making the jump ... Fifth Head of Cerberus & Blue's Waters/Green's Jungles.

Even if bacterial material were being transferred all the time, I think it'd be a stretch to call them the same "ecosystem" unless they were actually reliant on each other. But I'm not an biologist either.

I imagine their relative distances change frequently, so probably not.

Check out "Rocheworld."

Uh, Mongo when it flew by Earth?

edit: Mongo from Flash Gordon

Anyone else immediately think that we'd discovered Krypton when they read "red sun?"

As these planets are most probably TIDALLY LOCKED, making it hard for LIFE to thrive.

> All seven of TRAPPIST-1's planets orbit much closer than Earth orbits the Sun. A year on the closest planet passes in only 1.5 Earth days, while the sixth planet's year passes in only 12.3 days

>Tidally locked planets likely have very large differences in temperature between their permanently lit day sides and their permanently dark night sides, which could produce very strong winds circling the planets, while making the best places for life close to the mild twilight regions between the two sides.

> Another important consideration is that red dwarf stars are subject to frequent, intense flares that are likely to have stripped away the atmospheres of any planets in such close orbits.


On the other hand, tidal locking can stir the pot, possibly creating more opportunities for the chemistry of life to form.

One of the astronomers, Triaud has been quoted saying this is a relatively calm red dwarf that doesn't produce a lot of flares.

> If a person was standing on one of the planet’s surface, they could gaze up and potentially see geological features or clouds of neighboring worlds...

Makes me think of the film Another Earth


Melancholia by Lars von Trier is another great movie about the earth colliding with another planet.


An excellent, incredibly beautiful film, beyond the topical plot point.

Beautiful, but super, super, boring -- with an extra helping of boring on top.

> Beautiful, but super, super, boring

Let's just say that it's definitely an art-house film. Some find that sort of thing boring, but not everyone.

The challenging thing about Melancholia isn't "boredom" but the shaky camera work in the first half of the movie. I turned it off in disgust after 30 minutes or so. No idea why I went back and watched the rest of it, but I'm glad I did. One of those films that sticks with you.

You obviously haven't seen The Turin Horse. Melancholia was action packed compared to that.

Yeah, but Another Earth's main character is fascinated by astronomy and gets accepted to MIT

Which is on Netflix for streaming. Thanks for the tip.

Except with multiple planets?

I was gonna say this.

Other awesome facts, the closest star in the habitable zone might have a "year" of a day and a half, and the furthest out in the zone, a "year" of 20 days.

Well, in Lexx, there was Fire[0] and Water[1], which shared an atmosphere[2] which could be traversed with balloons.[3]

0) http://lexx.wikia.com/wiki/Fire

1) http://lexx.wikia.com/wiki/Water

2) https://goo.gl/images/xmxoJ9

3) https://goo.gl/images/oyVNF0

> the TRAPPIST-1 star – classified as an ultra-cool dwarf

I propose we name it "Dinklage."

Out of interest , although dimmer, are there any potential hazards simply due to the proximity of a dim star?

> are there...hazards simply due to the proximity of a dim star

Tidal locking [1]. Similar to how our moon shines at us ass first all the time, the planets around TRAPIST-1 would be expected to have one face locked to their star. Instead of an equatorial belt bookended with loops of temperate zones, as we have on Earth, we should expect, climatically, an "equatorial" face and a "polar" face separated by a tropic-to-temperate transition area.

[1] https://en.wikipedia.org/wiki/Tidal_locking

Of course, #askNasa didn't win me a question, but could any astrobiologists comment on this question: Tidal locking means the planets would always have a side facing the star, leading to very different thermodynamics in terms of climate and weather on the planet, not to mention radiation. Doesn't that very much hurt the chances for life on those planets?

The debate rages. The problem is that one side of the planet is essentially exposed to space and thus tends to be at cosmic background temperature, and the other side exposed to the star. It is thought by a lot of people that anything volatile enough to be a gas, ever (so, including water), would rapidly end up migrating over to the frozen side, so even if the planet started with the right mix of water and whatever other volatiles are needed it would shortly not have any in the temperate range. Some have objected that the planet could wobble and periodically unfreeze some of that stuff, and maybe life could exist in a resulting narrow temperate zone. My personal feeling is that it would still far-too-rapidly simply freeze out again, this time out of reach of the wobble, so the parched zone would simply grow to include everything ever touched by the sun rather than forming a stable temperate zone.

But we won't really know until we go look at a planet like this, because we don't have one locally to look at. (Plenty of tidally-locked bodies, plenty of bodies with volatiles and enough energy to keep them moving, I'm pretty sure nothing in the Solar system with both.)

Oceans can move a lot of heat around a planet, so the cold side could stay well above freezing. Remember it's T^4 so cold areas radiate far less heat.

That said, if there where minimal atmosphere then the effects your talking about become a larger issue. Atmosphere is largely a function of solar wind and volcanic activity which relates to the isotopes in a planets core making this hard to predict.

But the planets are close enough to interact gravitationally. Perhaps that would accomplish more than just a slight wobble.

If water freezes on the dark side, moisture in the atmosphere would probably move from warm to dark side and fall down permanently as a snow gradually removing liquid water.

If the oxygen and nitrogen freezes and snows down in the dark side (-220 C or so), the warm side can't have atmosphere either.

Unless there is some way tidally locked planet can have stable air or sea convection between the sides. I don't think they have.

If there is enough gravitational pull, the planet itself might be warmed by geologic flexing like Io.

I think one idea is large mountains on the dark side and the water slides back down as a glacier that melts, and eventually vaporizes, and back in a circle.

You have to watch out though - make your mountains too high, and you shift your center of gravity, and now your mountains are no longer elevated.

So if the water and gasses migrate to the cold side, I wonder if that would eventually make the cold side heavy enough to be rotated towards the star, causing the planet to periodically(probably over several millenia) reverse the side facing the star.

You're thinking of Earth, where the polar ice builds up perpendicular to the sun, causing tidal effects to wobble our axis a bit.

In this case, the ice is building up in such a way to make the planet even longer in the direction that tidal locking already had elongated it. The effect of which is that tidal locking would get stronger; not weaker.

I don't think it matters too much that it'd be icy on one side and rocky on the other; I think it matters more that it's oblong. But even supposing it does matter, if your intuition is that the more-dense end would want to fall towards the star, then that'd be the rocky end; not the icy end. Yes, the icy end got heavier supposing you measure from the rocky planet's center. But if you shift your frame of reference to be the planet's center of mass, then both halves of course kept exactly 50% of the mass; the densities are what shifted.

What about tidal and geological heating? or a greenhouse effect similar to Venus?

Any heat source exposed to space has the basic problem of its volatiles running away and not coming back. On geological time frames, this effect is probably nearly instant, so it isn't very helpful that maybe a new volcano could pop up somewhere and melt lots of stuff or something, because all that does is put a hole in the permanently frozen layer. Any heat source not exposed to space might harbor life, but that's not particularly true of these planets; we already have things like Europa locally with the same possibility.

The issues with valuable resources running away and not coming back is a serious one even for Earth, which I think might surprise some people. The geological carbon cycle [1] in particular is one that may surprise people who have not encountered it before, or not thought about it in terms of extraterrestrial life. On geological time scales it's surprisingly easy for entire important elements to go find themselves a low-energy configuration they like and disappear from any putative biosphere. The issues with a tidally-locked planet providing such solutions to "all gasses liquids" is merely an extreme example of the case, and really makes one wonder how it would be possible for such a planet to stay "stirred" enough for life to have access to what it needs to develop.

[1]: https://en.wikipedia.org/wiki/Carbon_cycle#Geological_carbon...

The link you provided suggests that one of the main ways for carbon to enter the atmosphere or ocean is through volcanic eruptions and geological hot spots. Isn't increased geological activity one of the results of orbital resonance?

If the 'central' planet has 6 close neighbours of equivalent size in resonant orbits would this not provide a very large amount of 'stirring'? These planets are also much more massive than Europa which is only 0.008 times the mass of the Earth compared to ~.6 and ~1.3 Earth masses for the ones in the habitable zone. They may have a more substantial mantle and core, possibly global magnetic fields and definitely more gravity to hold on to any fugitive gasses.

Considering geological timescales, this system is also billions of years younger than our own, potentially only a little over 500 million years old. The processes you draw concern to may simply not have had time to play out yet.

I'm also not convinced that the atmosphere would be cold enough to freeze out gasses on the night side if there were significant oceans or enough atmospheric circulation to transfer heat from the day side.

That sounds like a fun simulation to run

I know people have tried. I believe you can get both results if you put the right numbers in. Personally I consider this one of the canonical examples of where a simulation is a waste of time; with absolutely no ability to validate the model against reality, the model is in my humble-but-strong opinion utterly useless, which I mean in the strongest metaphysical sense possible. There's more ways to be wrong than to detect that you're wrong. (That's not just a flippant cute turn of phrase; I mean that as a rather fundamental issue with the entire idea.)

Apparently what would hurt the chance of life in a tidally locked planet the most is that due to being tidally locked the planet would have a reduced magnetic field to protect the atmosphere, and therefore there is a good chance that the planet would lose it's atmosphere over time.


Agreed, but there are other variables involved, including strength of stellar wind, density of atmosphere, whether a magnetic field is induced by the stellar wind, the mass of the planet (strength of its gravity), etc.

Does atmosphere include the ocean? Because life developed in the oceans first here, and some has never left.

Without an atmosphere you can't maintain a surface ocean, because liquid water can't exist in a vacuum. It's possible for the ocean to exist under a crust of ice though. See Europa for an example. So it's still theoretically possible for life to exist in a subsurface ocean, but I think it's a lot less likely compared to a planet with an atmosphere and temperatures that would support liquid water on the surface.

> It's possible for the ocean to exist under a crust of ice though. See Europa for an example.

That's exactly what I was thinking of. :)

> I think it's a lot less likely compared to a planet with an atmosphere and temperatures that would support liquid water on the surface.

Sure, but we have little information on how common life is. We're not even sure there's no life on Europa. If Europa supports life, it may be that (basic) life is somewhat common given certain criteria, and while I agree it's probably more common on planets with atmosphere and your statements were not incorrect, it may be that life is actually fairly likely on a planet like that (which is what I, possibly incorrectly, interpreted your statement as ultimately trying to convey).

I remember reading about 55 Cancri e (1), another tidally locked planet (2) featured in NASA's Galaxy of Horrors as "The Twilight Zone" (3), where life in the boundary seems unlikely.

1. https://exoplanets.nasa.gov/custom_planets/2

2. https://exoplanets.nasa.gov/resources/149

3. https://exoplanets.nasa.gov/alien-worlds/galaxy-of-horrors

I don't see why. If anything, life might be even easier if you're constantly getting energy from above, rather than intermittently. In any case, "different climate and weather" doesn't seem to me to imply "hurt the chances for life."

If they're in the habitable zone, then they're getting similar radiation as an organism at the far north latitudes of Earth are getting during the summer. I don't know if it makes that much difference to a short-lived bacteria whether it's full sunlight for several weeks at a time, vs full sunlight forever.

I'm not a biologist, but here's a fascinating article on the subject: http://m.nautil.us/blog/forget-earth_likewell-first-find-ali...

TL;DR is that there may exist a band around the planet where the two zones meet that is habitable. I think it's a reasonable supposition that most of the rest of the planet would be uninhabitable.

I'm not an astro-biologist, but I assume that it wouldn't be conducive to life as we know it, but that doesn't rule out all life.

I would be very interested in seeing comparative weather simulations for a fictional tidal locked planet to Earth and the other Sol planets.

Maybe but I like to think there are creatures living in the temperate rim of a tidally locked planet somewhere debating whether life could possibly evolve on a rotating planet.

"I mean, there'd be temperature fluctuations of tens of degrees every day! It would be dark half the time! How could life survive in such an unstable environment?"

And don't forget: there will be long-term cyclical trends of dozens of degrees due to geometric properties of the orbit and hypothesized tilts!

It's not a given, though. We used to think Mercury is tidal locked, but that turns out not to be the case. These planets, as I understand it, are in similar orbits, so they may not be locked either.

Well, Mercury is in a tidally locked orbit of sorts. Its rotation is resonant with its orbit -- it experiences two days every three years, and this isn't a coincidence, it's a relatively stable outcome of its tidal forces with the sun.

Fascinating! Also – off topic, but – this description reminded me of Twinsun[1], the planet in the game Little Big Adventure. It remains one of my fondest game memories of that era, despite all its weird bugs. I've thought about finding a copy and playing it again at some point, but I fear it might spoil my good memories of it..

[1]: http://lba.wikia.com/wiki/Twinsun

Dammit, why did you have to remind me... Both LBA and LBA2 stand out as extremely memorable from my childhood. It does look like there's a revival of game-styles from that era, given Thimbleweed Park[0], Pathway[1], and apparently 2Dark[2] from (one of?) the authors of LBA. Any more?

[0] https://thimbleweedpark.com [1] http://www.pathway-game.com [2] http://www.2dark.cc

Wow, those look amazing! Thanks for the tips!

You can pick up Relentless on GOG :] https://www.gog.com/game/little_big_adventure

And apparently there's a macOS version too – SOLD! Thanks buddy! :o)

For what it's worth I did this a few years ago and was not disappointed - great to hear other people grew up with this game too!

Great to hear! I just bought LBA and LBA2 from GOG, from the sibling commenter's tip. Now I just need to find a few free hours!

This would be my first thought as well, but the original article says that they are near-orbitally resonant. It seems possible to me that the regularly passing nearby planets could apply enough of a torque to counteract the tidal locking---though I don't have a good sense of the order of magnitude of the forces, so maybe not.

Fascinating thank you

Depending on the spectrum of the star, I would be concerned about non-visible radiation doses when in close proximity to the star.

IANA astrophysicist, though.

Actually, adding onto that, I'm wondering whether orbits this tight would result in a noticeable centripetal force -- that is, that you'd feel lighter on the night side of the planet than on the day side.

Good point, this is in TFA:

"Although at least some fraction of each planet could harbor liquid water, it doesn't necessarily follow that they are habitable. TRAPPIST-1 emits about the same amount of X-ray and ultraviolet radiation as the Sun does, which could chew away at any protective atmospheres the planets might have."

But it's complicated. For example, apparently the energetic radiation can help by stripping away the H/He atmosphere. For more, see:


Michael Okuda has raised the question on his Twitter feed of whether the planets would be close enough to the star that tidal force could be an issue---hard to say at this point (in the sense that they're not loose clouds of rocks, so tidal forces haven't sheared them apart, but I'd assume it's unclear whether they might have interesting geological activity, such as frequent earthquakes or unexpected extra heat due to internal friction).

Like others have pointed out, the combination of the planets being tidally locked so only one side gets sunlight and the strong X-ray radiation and flaring from the host star make it considerably un-Earth-like, and harder for life as we know it to develop.

Actually they are fewer. A dim star has less high energy radiation and a lower probability of harmful solar flares.

That's backwards. Red dwarfs have extremely powerful flares relative to their luminosity. So much so that it's unlikely that life would survive on the surface of an orbiting planet. (Though life would probably survive underwater.)



That's not quite true. These planets are very close to the star and can receive large doses of the little bit of harmful radiation that the star puts out. Additionally, these planets put out a lot of infrared, but not a lot of higher energy photons, and life-as-we-know-it needs those higher energy photons. That infrared is also absorbed by water in any atmospheres or oceans that are present, leaving even less for life. Finally, these types of stars tend to have rather variable output in their spectrums, which may make it difficult for life to adapt.

But the danger of both of those things surely decreases with the square of the distance to the star?

More radiation = more mutations = healthier/faster evolution!

Life is more than capable of evolving mechanisms to increase or decrease it's mutation rate. On Earth Eurkaryotic cells with large genomes have developed nuclei to reduce their mutation rate and bacteria are more of a mixed bag with some even deliberately uping their mutation rate above what would be cause by radiation, etc. So in the long run eukaryotic life would just have to waste more resources on mechanisms to resist the effects of the radiation.

That doesn't follow, at all. If we're talking about Earth-like life, then any such life would need protection from radiation to be able to live long enough to reproduce. If such protection wasn't provided by the planet's atmosphere, then life there wouldn't move out of the water. In any case, the mutation rate would need to be extremely low, as it is with Earth life.

Then the surface of stars ought to have more life than planets.

Just as interesting is a recent news story about a plan to build an interstellar space ship, propelled by giant solar sails to travel about .2c (20% of the speed of light).

In other words, we could get to the Trappist-1 star system in about 145 years.. practically in the blink of an eye.


Nuclear pulse propolsion... Project Orion... if only we could figure out the darn problem with the fallout and treaties/bans.

Tsiolkovsky is unforgiving. You'd need an amazing amount of fuel.

And they all seem to rotate around their sun in 1.5-20 days.


Revolve around. Sorry, had to.

They're more-than-likely tidally locked, so... you're both right.

Importantly, that means there is basically no way that a civilization that developed on such a planet would not at some point endeavor to travel to those other planets.

> no way that a civilization that developed on such a planet would not at some point endeavor to travel to those other planets.

That seems like a very human statement.

One could argue for a civilization to succeed it must be content with living on its home planet. And as a result, it would take good care of it.

You must be new here [on planet Earth].

Alternatively the parent considers the human race to either not have succeeded or to be in the process of changing to take good care of it

You could also argue that a civilization has not succeeded until it is able to completely sever ties with its home planet and venture out into the galaxy on its own. Leaving the nest, so to speak.

I'm wondering since these planets are so close to the parent star and to each other would it induce any gravitational instabilities?

maybe them aliens made the system up, so that it doesn't fall apart under its own gravity. Makes sense: just increase the habitable area by bringing in smaller planets into the goldilock zone - that might come out cheaper then to go interstellar.

Maybe lots of planets that circle the same star over the same orbit would be a better indicator of alien activity than a dyson sphere.

Is this an orbitally stable arrangement?

Yeah, they are all resonant.

So this means all the planets are all a volcanic mess because of the tidal forces?

Perhaps some of them, especially the innermost. Considering the orbital periods and resonance it seems like this system might be similar to the Jovian or Saturnian systems.

The planets may be tidally locked but there is also a chance they could have a slow rotation similar to Mercury. That planet has also shown us that a magnetic field is possible without a fast rotation so there's a chance of these exoplanets having one as well.

Tidal forces can be a boon to planets with synchronous rotation since they provide an additional source of heating for the side of the planet that faces away from the star. If there is liquid water or a thick atmosphere they may also drive tidal and weather patterns that could help circulate heat from the warm side to the cold side.

Geological activity also 'stirs the pot' when it comes to precursors for life. All this extra energy in the system could mean that even TRAPPIST-1g (outside the habitable zone) might have an atmosphere and oceans.

Those cool stars are also very durable and will not burn that easily.

Wonder how tidal forces from these planets would affect [possible] oceans on their neighbors. Would imagine it would make for quite a perturbed environment.

My thoughts exactly. The coolest skyscapes ever! On edit: This also reminds me of U. LeGuin's system in the dispossessed.

Sounds like tidal forces would be extreme.

I am wondering how it could affect our psyche if we were able to gaze on a mirror world with our own eyes in broad daylight. This is the first VR application I would think of: display an Earth like planet in the sky and see how it affects us.

That's exactly the premise of the (good) movie Another Earth: http://www.imdb.com/title/tt1549572

I wonder what planets that close together would do to tides on one another.

And the name of the star is shared with Trappist beer!

A colleague of mine has an insider info that the telescope was named after beer on purpose.

Yes, the project was born in Liège University in Belgium.

The name they chose for their programs are quite funny with belgian references: SPECULOOS[0] and TRAPPIST[1].

There are 11 trappist beers in the world (of which 6 are brewed in Belgium). Speculoos is a Dutch/Belgian cookie.

[0]: http://www.speculoos.ulg.ac.be/cms/c_3272698/en/speculoos-po... [1]: http://www.trappist.ulg.ac.be/cms/c_3300885/en/trappist-port...

I'm blown away the planets haven't torn each other apart or all collided by now...

And I was just thinking, if there were ever or ever to be oceans on these planets what kind of brutal tides would be experienced?

I wonder what kind of tidal forces these planets exert one one another.

Kinda like in No Man's Sky game.

To get a spacecraft there it would take:

Accelerating at 1g the 1st half, and decelerating at 1g the 2nd half, the traveler would experience 7.3 years of time. For observers it would take 41.8 years at a max speed of 0.998c

If you had a near perfect hydrogen -> helium fusion engine, it'd take about 6 million tons of fuel (about the mass of the Pyramids of Egypt or 2,000 Saturn V rockets)

It would take 37 days at warp 6 (assuming we're using the new warp factors established in The Next Generation). I have no idea how much dilithium crystal would be required though.

> I have no idea how much dilithium crystal would be required though.

Depends on the plot needs for the ~~episode~~ journey.

Particularly in Voyager. They were either running extremely low early in the show or had a virtually infinite supply later in the show. No explanation given.

Which is particularly troublesome given the plot of the Equinox episodes. Since on that ship they were harvesting creates to extend their dilithium crystal supply allowing them to travel faster/less efficiently.

But even throughout those episodes they never discussed why Voyager rarely had issues with supply after the first couple of seasons. Just hand waved it away with Voyager having a bigger crew, like that magically solves it.

Voyager spent most of the first season looking for deuterium, so that they could keep the ship moving forward.

Presumably, at some point around episode ~15, someone in either engineering, or the writing team realized that it is the third most abundant element in the universe.

Well.... the most abundant element in the universe is "Nothingium." Just because hydrogen is common doesn't mean it's always around when you need it, especially in heavy form.

It's been a long time since I laughed out loud at an HN comment! Well played. Thank you for that.

It doesn't just have to be common, it has to be worth harvesting.

It could be that it took them this long to locate and get to such a supply, or that they had to repair / construct equipment that normally wouldn't be expected to be used.

Their engines don't consume dilithium. Rather, it's a catalyst to the matter-antimatter reaction.

Most likely several hundred quatloos' worth, I'm guessing. :D

Edit: Oh, HN, you are so humor impaired sometimes.

Voting is a mechanism to signal whether the comment adds anything to the discussion. Star Trek references really don't add anything to an actual scientific discovery. I would much rather read actual engineering rather than entertainment driven thought.

I think you've just proven his point.

Yeah, I know, I might be occasionally too cynical.

I took the post as commentary on the engineering feasibility of the parent post.

Simply: this is not reddit. Voting happens based on the content of information added by your comment. Not a joke or a wordplay, unfortunately.

I had to downvote you because we're not supposed to compare HN to reddit. ;)

Edit: Oops, I cancelled my downvote.

That's a misreading of the guidelines:

If your account is less than a year old, please don't submit comments saying that HN is turning into Reddit. It's a common semi-noob illusion, as old as the hills.


That actually sounds... more plausible than I would have expected. Like, doable with technology I can imagine being within reach in the next 50 years even if we don't achieve any currently-unforseen breakthroughs.

Which begs the question, why haven't we at least even tried to have done anything like this already?

Do we really need to repeatedly spend comparable amounts of money on yet another dramatic TV special about humans traveling to Mars, as narrated by a favored celebrity? We really are running out of time. And it almost seems like it's pre-determined to happen. :\

The engineering issues are really tough, though surmountable. Currently, we just can't engineer the parts that will last that long in hard vacuum. Mostly because we can't test in that environment easily. Also, what do you do when all the light bulbs have burned out or gone haywire, what does that fault-tree look like for the billion and one parts on the craft? For a short journey of ~7 years, it's not a very big deal, it's just engineering issues. When you get into generation ship discussions then it becomes a human rights nightmare to trap newborns in a ship for their entire life and the lives of their descendants.

With a round trip parts delivery time OF a generation, and a communications delay of almost a decade (two for duplex), I don't see any reason not to classify such a mission as a short-range 'generation ship' / complete colony effort.

Getting our 'eggs' out of a single cosmic basket is really important, however I think we need to at least take the baby-crawl to establishing an outpost in the asteroid belt. That would be far closer, have far more reasonable communications/parts delays, and if we can actually send up some robots to build things ahead of us, might actually be a good manufacturing base.

I feel that advancements in quantum mechanics will solve the communication problem.

No, it almost certainly won't. Our current understanding of quantum information theory simply doesn't allow transmitting classical information faster than light. There's no room in what we don't understand that could plausibly contain FTL communication. This is a pretty fundamental result of quantum information theory. https://en.m.wikipedia.org/wiki/No-communication_theorem

> it becomes a human rights nightmare to trap newborns in a ship for their entire life and the lives of their descendants.

Which is exactly why we should get some people off this ship, and colonizing others!

Oh, you meant the generation ship, not the Earth; nevermind.

Yeah I'm to be honest just trying to awaken people to the priority being that we need to establish a self-sufficient colony somewhere other than Earth.

Honestly, as long as humans stay stuck to earth, losing all humanity on earth won't hurt anyone. As long as the extinction is instant. If we have colonies, those colonies need to suffer through the knowledge that we lost earth.

Establishing colonies is only imperative if the continuation of the human race is. I'd argue that humans have value only due to other humans. There is nothing inherently valuable about human life from a non-human perspective.

That is not to say I don't support space colonization, just that I don't think its a moral imperative.

"There is nothing inherently valuable about human life from a non-human perspective."

How would you know?

It's a perfectly reasonable assumption until there's some evidence there is. Given the vastness and scale of the universe, it seems quite likely that our disappearance would never be noticed.

Going unnoticed is not the same as inherently not valuable. Imagine aliens finding us extinct, wringing their little tentacles in dispair at the lost probing opportunities. :)

Well, HN is not the most optimal place to do that. There are not many of us on here and we all already know these things. 1600 Pennsylvania Pl. is a better bang for your buck.

I think you probably mean 1600 Pennsylvania Ave. (not Pl.), Washington, D.C.

Though I don't share your assessment that that is a productive place to direct citizen input on this (or any other) issue.


Elon Musk is working on that.


And you're certain enough that he's going to be able to do it in time and that he's doing it properly enough that you don't have to do anything about it. And you'll continue to go about doing the exact same things. Got it.

In no way attempting to deflect from my own regrettable inaction, I'm curious to know what you're doing about it?

Based on his previous achievements I feel like he is likely to move the field forward by big steps. And if not him the people after him. I'm not sure if pushing myself into field I don't understand much would help the progress. Scientists do science, not activists.

Are you a space activist of some sort?

The launch cost of launching the mass of the pyramids of gaza into orbit would bankrupt the richest economies. No your hypothetical engine won't be 100% efficient. This is completely unfeasible.

Low mass spacecraft are our only real options. A nano-sized solar sail craft powered by the sun or lasers from Earth can hit up to 20% lightspeed theoretically and its launch costs would be affordable, if not relatively cheap. We could have a spacecraft at Alpha Centauri in merely 20 years. Or simply launch them by the dozens or hundreds to various locations. Stephen Hawking has proposed this system in the past and we've had trial launches of solar sails via the planetary society and others. Its a solid and most likely doable concept at scale. Yes, your kids or grandkids will hear the results, but not you. Is that such a problem, especially when the alternatives are never launching a probe to those systems?

To be fair, the proposed Centauri mission would be within a person's lifetime. 20 years to get there then another 4 and half to get the data. So if we launch when you're in your 40s or even 50s, you'll still see the data.

We can even use this concept on heavier ships in the solar system to get to Mars quickly. How quickly? Three days quickly for a 100kg craft. This is a bit more pie-in-the-sky of course:


>The launch cost of launching the mass of the pyramids of gaza into orbit would bankrupt the richest economies. No your hypothetical engine won't be 100% efficient. This is completely unfeasible.

Not necessarily. You don't need to launch the mass of the pyramids from Earth, you just need to find a source of fuel somewhere else in the Solar System that's in a shallower gravity well, like on the Moon. This is why a lot of people want to work on mining asteroids, and building mining/refining/manufacturing infrastructure offworld.

You can't really just extrapolate the current cost of launching materials by the kilogram. A project of that magnitude would generate economies of scale and probably some innovations along the way that would bring down the cost. The "nearly perfect" fusion engine is really the hard part.

You are assuming that this mass will be launched using today's chemically powered rockets. But using nuclear propelled rockets will bring down the launch costs by orders of magnitude.

A Russian billionaire is trying: https://breakthroughinitiatives.org/Initiative/3

I'm talking about establishing a self-sufficient colony somewhere other than Earth. We have a major crisis on our hands. And few are even willing to consider let alone research and confirm that we're talking about an extinction event much sooner than we thought, maybe on the order of just a couple years out. Problem is, we don't know. Bigger problem is, we're not doing anything about it.

If its affordable to send people to an off world colony then its affordable to bomb it when war on Earth breaks out. Fleeing isn't going to help in a wartime situation and the idea it will not be targeted by world powers is a little naive.

I said nothing about war..?

There's no other conceivable extinction event that could occur "a couple years out". If you're talking climate change, then I agree that's a major problem, but on the order of at least decades.

Plus climate change would have to get pretty incredibly bad for, say, Mars to start looking easier to live on than Earth.

That's the problem with colonization as an Earth back-up—even Antarctica and the Sahara Desert are more livable than any other body in the Solar System, by a long shot. Another Snowball Earth or a heavily desertified Earth would still be preferable to Mars. Throw in a fair amount of radiation, even—still better.

Cuts down significantly on the sorts of events for which a Martian back-up world is preferable to a shelter-in-place strategy.

But if you could go out now and terraform a planet so that when in future you have problems here you have a place to go to that matches the original environment back on earth. And you learn a lot of things about "geo"engineering, the things you cannot try safely at home, which can come in handy to fix any problem back on earth.

We have no ability to terraform anything, let alone a planet, let alone the economics of it ever being feasible. Life isn't a star trek episode. We can't just go and 'terraform now' as you say. We can barely land anything on Mars without a 50% failrate right now. We're talking technology way, way into the future. Hundreds, perhaps thousands, of years.

This is precisely what we don't know. If you're talking averages, then sure it takes decades to observe a meaningful change. However climate change of the sort we're anticipating now isn't about averages. It's about peaks, it's about records, and possibly major shifts in equilibrium.

Basically what we witness so far and will keep on seeing are spikes in all directions of the spectrums (e.g. record high temps, but also record lows; rain in the Death Valley and droughts in formerly wet areas). More critically, what little we've been able to gather on how fast climate eras shift from one to the next, it appears that whereas in-cycle change happens rather slowly (change within an era, because averages), climate era shifts could happen very quickly (because chain of events). We're talking going from a warm era to a glacial one within a few years, sometimes months even. A high speculation is that some thongs might upset the Gulfstream and you'd observe climate evolve from year to year.

What about a comet impact? That's extinction level and comes with very little warning.

Given our limited sky coverage, we can't really rule out killer meteor on the time scale of "a couple of years", or even a couple of hours, though the probability is extremely low (like, sub-1-in-100 million, for the couple of years time frame.)

Still probably higher than extinction from war in the same time frame.

> There's no other conceivable extinction event that could occur "a couple years out".

Life on earth could end in the next five minutes. :) https://www.youtube.com/watch?v=RLykC1VN7NY

The resources and practically to gently shoving a comet or asteroid out of the way are probably a billion less than building self-sustaining colonies elsewhere. Worse, now we have two planets to defend, not one.

I don't see the "we must migrate now" types saying "lets put migration away for a while so we can better build anti-asteroid solutions and detection systems."

Arguably, we're just a couple launches and deployments of mass drivers away from fixing this issue. This is all known tech that could be deployed relatively quickly. A self-sustaining Martian colony is probably hundreds of years away considering the work it would take to terraform the planet.

The resources involved in preventing a GRB from hitting us, on the other hand, are . . .

. . . actually I have absolutely no idea how you would practically do that at all.

He appeared to be speaking of a known, ongoing crisis, not a minute possibility of a killer meteor.

Haha! My link doesn't go to a video about meteors. Your point is taken, though. I was just being cute and/or hoping you hadn't heard about this.

But I have heard the possibility of a GRB discussed seriously as a motivator for expanding, not just through the solar system, but through the galaxy.

Lots of good reasons to establish a space colony, fleeing the earth is not one of them. By this sort of argument you actually discredit the idea of space exploration.

> fleeing the earth is not one of them

Why not? If a big asteroid is going to hit earth (for example), fleeing is a pretty reasonable response. It's also a reasonable defense against technobiological hazards.

The impact would have to be absolutely massive to cause enough damage to the Earth that it is less liveable than Mars.

To compare, the Triassic–Jurassic extinction event created an Earth still more liveable than Mars. Even if we go way back in time, to when there was no land-life on Earth and a poorly oxygenated atmosphere, the Earth is still better off than Mars for supporting human life.

If the goal is to save the human race, then it'd be better to have a few high orbit or lunar habitats, then if something wipes out the majority of civilisation on Earth, we immediately begin recolonisation of our home planet.

Let me ask you this question: Would you consider the Titanic, oh, I don't know -- a success story?

Because that's basically what this sort of thing comes down to, at the end of it. There's basically nothing that is going to be existentially, immediately threatening to earth on a timescale that Mars is actually a more livable environment.

Where else in the Solar System could we even get the amount of water we would need?

Isn't Mars full of water? Source: I read the Mars trilogy by Kim Stanley Robinson.

The chance that an asteroid hitting Earth that actually matters is extremely low. It is even lower chance that we can detect it on time. It is much higher chance that politicians will start a nuclear war that wipes out most of humanity from the face of Earth.

I'm not certain what you mean by "fleeing", but we sure as hell aren't going to move seven billion people. A bunch of engineers and rich people may be able to get out, but that's about it. To save the rest, we'll need cheaper methods.

Isn't part of the problem that any ship capable of interstellar travel is also capable of being turned into a WMD? I imagine a lot of people would get really nervous if someone for instance parked a bunch of radioactive material in low earth orbit, and even with fusion there would be the fear that someone could turn the ship around.

To be fair kinetic bombardment is stupid easy to do once you can put stuff into orbit. Put a few, 20 foot long tungsten rods into orbit and you can effectively nuke, without radiation, any location that you orbit over [1].

Sure this is a problem but it's one that already exists today, not necessarily only when we start building space craft in orbit.

[1] https://en.wikipedia.org/wiki/Kinetic_bombardment

Contract SpaceX to bring the rods into orbit, then bill per strike. KBaaS, disrupting warfare since 2017.

Back of the envelope calculation: rods with length of 6m and radius of 5cm weight little over 900kg. Falcon 9 can bring 22.8 tons to LEO. So we can get up about 24 of these in one go. If we want to use the USAF dimensions of 6.1m and radius of 0.15m, then it's only 2 of them, maybe 3 with some adjustments to the rocket.

I always wondered how to de-orbit those rods. It's not like you can just 'drop' them as they are already in free-fall. You'd need to cancel quite a bit of orbital velocity to get the things to de-orbit. Aiming'd be even more of a bitch.

> ...a 6.1 m × 0.3 m tungsten cylinder impacting at Mach 10 has a kinetic energy equivalent to approximately 11.5 tons of TNT (or 7.2 tons of dynamite).

Well, that's a bit underwhelming. Sounds a bit like Russian polonium tea, that is, less like a matter of efficiency, and more like showing off the sheer extravaganza of killing somebody in the most colorful, expensive way.

Kinetic bombardment is silly and inefficient science fiction. Conventionally armed ballistic missiles can strike any point on Earth almost as quickly at a far lower cost and with greater survivability.

Well today sending a rocket up, putting these things in orbit and then dropping them would probably be a bit obvious and inefficient. But in the near future when we're mining asteroids? As long as they can be captured closed enough to Earth I would imagine kinetic bombardment would be pretty effective. They would be rather difficult to shoot out of the sky as ballistic missiles can be blown up prior to reaching target but kinetic would require an much, much larger amount of energy to destroy enough so as to not hit and damage the target.

Asteroid mining on any sort of commercial scale is far future, not near future. Even with fully reusable rockets, asteroid mining wouldn't be profitable; anything we need can be obtained cheaper on Earth.

Small asteroids are too irregularly shaped to be useful as precision-guided projectiles. As soon as they hit the atmosphere they're going to veer off course.

Kinetic bombardment satellites — whether fully artificial or asteroids guidance and propulsion strapped on — would be in known orbits with limited maneuvering capability and thus highly vulnerable to antisatellite weapons. It takes very little energy to kill a satellite; you don't have to vaporize it, just break any critical part in the communication, propulsion, or guidance systems. Satellites are generally easier targets to hit than ballistic missiles.

> Asteroid mining on any sort of commercial scale is far future, not near future. Even with fully reusable rockets, asteroid mining wouldn't be profitable; anything we need can be obtained cheaper on Earth.

It's certainly in the future, it just all depends on what is far to you. Many companies who want to get in on this are hoping to attempt within the next 10-15 years (obviously commercial mining would come some years later after a successful attempt). If it can be successfully navigated it would have the potential to be crazy profitable!

It's too expensive to bring materials up but if you can mine materials in space and deliver them to the various space companies / government departments is where you'd make your money. Mining water, in theory, should be crazy cheaper as long as you can capture the asteroid efficiently enough. NASA has already said they would love to see more work in this space so they can purchase materials cheaper while in space and they're even hoping to capture an asteroid in the mid 2020s as a type of test for this scenario.

> Satellites are generally easier targets to hit than ballistic missiles.

This misses my entire point: in order to destroy the kinetic projectile you would have to launch a preemptive strike against the satellite. There is no way around it. You won't be able to defend yourself against a large projective being precision dropped onto your location without a lot of energy (so depending on what country you are maybe you can knock several into a few direction or vaporize with a high enough yield but you only get one chance at destroying it). Meanwhile a ballistic missile, while faster, can be destroyed with a hot enough laser.

I understand they're not practical and if you want to use an asteroid itself that's even more awkward. But when we start mining asteroids, in my opinion, it's going to become crazy practical and cheap.

That's not how it would work. Incoming kinetic projectiles are just as vulnerable to defensive systems as ballistic missiles. Hit it hard enough and you can knock out the guidance system. They would need very precise and sensitive guidance systems to hit anything from orbit.

Space enthusiasts constantly underestimate costs and schedules. Just because something is theoretically possible doesn't mean that the engineering problems can be solved in an economical way. If there is large-scale asteroid mining in my lifetime then I'll eat my hat.

> Incoming kinetic projectiles are just as vulnerable to defensive systems as ballistic missiles. Hit it hard enough and you can knock out the guidance system

Not true at all. Kinetic projectiles would have no guidance system. It's just a big, dumb piece of tungsten. That's it. You would have to hit it hard enough to make sure that, when it hits, it won't cause damage. This means near complete vaporization. That's very energy intensive.

Ballistic missiles, however, simply need to have their payload exploded at almost any distance away from the target to reduce its power to near nothingness.

> If there is large-scale asteroid mining in my lifetime then I'll eat my hat.

Not sure how old you are but if you're under 40 and not planning on dying sooner than average then, in my opinion, you should start looking up hat recipes :D. At least I hope but it depends because the primary customer for asteroid mining is going to be space companies and government agencies like NASA. A disruptive political system that prevents said purchases could hamper progress significantly.

You seem to be hilariously ignorant about the realities of aerodynamics, rocketry, and orbital mechanics. Due to atmospheric turbulence and normal thrust variations in the rocket motors that would have to be used for de-orbit burns, any unguided projectiles would have such as huge CEP as to make them militarily useless. Unguided projectiles launched from aircraft today can't reliably hit anything at distances over a few miles; satellites are much farther. A (sensitive and fragile) terminal guidance system would be an absolute necessity. Contrary to what arrogant programmers might think, DARPA isn't run by idiots and they gave up on such nonsense schemes for good reason long ago.

As for asteroid mining, hope doesn't count for anything. There is no shortage of essential raw materials here on Earth. No one is going to commit the hundreds of billion $ necessary to do it on more than a trial basis. There's simply no economic incentive nor is there political will to spend that money. Sorry to burst your bubble.

Well I assume is the USG let alone SpaceX decided to put some 20 foot tungsten rods in orbit a lot of people would start raising objections pretty quickly.

If anyone is interested in kinetic bombardment, read Heinlein's "The Moon is a Harsh Mistress". Much like how the Fosterites in his "Stranger in a Strange Land" were a blueprint for Scientology, TMiaHM is a guide on how to plan and conduct a revolution, although in this case it was the Moon against Earth.

Jet planes can also be used to destroy skyscrapers. People don't seem to get really nervous about them.

We've created a giant security apparatus based on Jet planes. They are not something we just let anyone buy or fly and if you deviate from your flight path these days you stand a good chance of getting shot down. People definitely get nervous about them.

Are you implying that rockets capable of transporting several hundred kg of tungsten to orbit are -not- tightly controlled? I imagine if you assembled anything close to this size without seeking extensive permissions you would be quite severely punished

No, I'm just addressed the analogy of jet airplanes and pointing out those are tightly controlled. I understand that current rocked are very tightly controlled, my point is just that any sort of interstellar rocket would be much more dangerous and thus have to be subject to much higher controls. A ship that was capable of reaching a significant fraction of light speed would be the most dangerous weapon ever created though, and existing controls might not be sufficient.

NASA is not standing still. Europa just went to the next stage for exploration.


It just takes a lot of time to plan and build ships for space travel.

You're completely missing my point.

We've known about climate change for a long time. Since the 60s/70s, no? But nobody has been able to realize what it really is, because scientists do not understand gravity yet. I've been begging people to confirm this for themselves instead of believing what others say about it. If people really knew what global warming was they would have started working on ships decades ago.

My point is, people on stable self-sufficient colony outside of Earth is priority number one. Not sending a probe to Europa. But somehow I get the feeling you have no interest in this reality.

You sound a little unhinged to be honest. If you're really worried that climate change on Earth is going to cause big problems for humans (which is not an unreasonable concern; climate change threatens to cause significant sea level rise which will cause big problems for people living in sea-level coastal cities), building self-sufficient colonies offworld is a rather extreme answer to that. A simpler answer is to simply move inland, and make sure your structures can handle extreme weather. That's a lot easier than trying to build an offworld colony.

The real reason to build an offworld colony is because you're worried about a big asteroid strike. But here again, it's a lot easier to just build observation systems to spot these threats, and weapons systems to handle these threats, than to build an offworld colony that's truly self-sufficient.

Finally, offworld colonies have gigantic problems with them: 1) people don't handle radiation well, and no place in the Solar System protects us from radiation the way the Earth does, so we'd probably have to burrow underground to mitigate it, and 2) we really don't know how well the human body can handle low-gravity conditions, but we do know that the human body does not handle zero-g well and that it causes massive health problems. There's no place in the Solar System with close to Earth-normal gravity, except for Venus which is a hellhole hot enough to melt lead (on the surface). Mars is only 1/3g, and the Moon is only 1/6g, and pretty much everything else is even less except the gas giants which obviously aren't livable.

Now what climate change and offworld colonies (in this system at least) have to do with our lack of understanding of gravity, I have no idea.

So all we have to do about climate change is build structures to handle extreme weather? Climate change is and will continue to affect our whole food chain that supports the some ~7 billion people on earth. It's not just the weather we will be dealing with.

And you think it's easier to just pack up and move to Mars than to deal with the climate change? You think it'd be easier to figure out how to grow food on Mars than to mitigate climate change-caused problems with the food chain here?

There's lots of stuff you can do to grow food here even with climate change: greenhouses, indoor/vertical farming, etc. Good luck with all that on Mars.

Scientists understand gravity very well, pick up any book on general relativity.

> We've known about climate change for a long time. Since the 60s/70s, no? But nobody has been able to realize what it really is, because scientists do not understand gravity yet.

We know exactly what climate change is and it has nothing to do with gravity.

What does gravity have to do with climate change?

If you're curious on more than a surface level, this book is an excellent resource from an ex-astronaught on why things are lagging. "Safe Is Not An Option"


It sounds like you have a startup idea on your hands : )

How would this generate returns on investment? Monetary returns, that is.

I mean if I somehow magically become a billionaire I intend to throw money at the problem with no hope of ever making a return because I believe humanity's last hope is an offworld colony, but I doubt I'll convince any VCs to join in.

You've no idea. But for the first step, I need to find one or two very truthful physics grad students / electrical engineers who feel some responsibility for Earth or saving themselves. You wouldn't happen to know someone?

Why don't you become one?

Don't worry your pretty little head. I went to top schools.

I think you mean "Post-truthful"

Politics, specifically the PTBT[1]. Otherwise Project Orion[2] would be a reality now.

[1] https://en.wikipedia.org/wiki/Partial_Nuclear_Test_Ban_Treat...

[2] https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...

Project Daedalus seems more appropriate for interstellar travel:


EDIT: My math was totally wrong. 10 trillion dollars, 0.1x world GDP. (Still a lot of money though) Leaving the old text below so the replies make sense.


To move 6,000,000 megatons of fuel into low earth orbit would take 111,111 Falcon Heavy launches, at a total cost of $10,000,000,000,000 dollars. (10 quadrillion dollars, 93x world GDP)

Something that takes the total global economic output of the planet a century just to lift the fuel into orbit doesn't read as plausible in the next 50 years to me.

You wouldn't gather that fuel from earth.. you'd gather it from an icy asteroid or comet or moon (Europa).

I'm not sure if your error is in the number or in the words, but the number you wrote down is 10 trillion dollars.

Note to mention that Falcon Launches would get significantly cheaper if we have to do 100,000 of them.


Is it plausible for anything we'd build to travel .998c and survive the journey?

Just going that fast isn't really risky at all (assuming you don't hit anything, which isn't actually a safe assumption). The tough part is making something capable of a constant 1g of acceleration for a 7 year trip. Most of the craft we make only accelerate for the first small percent of a trip. We can do accelerations that high, but not for very long, and we can't even manage acceleration for such a long duration even at a small fraction of 1g.

You have no idea how scary traveling at near-lightspeed actually is. Isaac Arthur has a great video covering it. https://www.youtube.com/watch?v=s6BQSgidbmc

If you go fast enough doesn't any incoming radiation just get blue shifted into gamma rays? Just running into cosmic dust at the speed of light would not be fun.

>Just running into cosmic dust at the speed of light would not be fun.

That's why you need a navigational deflector dish. http://vignette1.wikia.nocookie.net/memoryalpha/images/b/b4/...

Isn't that the whole relativity theory: that if you emit a photon while at celerity 1c, it looks like it goes away at 1c both from you and from a still reference? hence blue is still blue at 1c?

The spectrum of light depends on the frequency of the vibrations in the electromagnetic field, not the velocity of the wave. For both red and blue light the wave is traveling at 1c but the peaks of the wave are at 700 nanometers or 400 nanometers depending on the color. And under Special Relativity distances distort so that you do in fact see light shifted to higher frequencies/shorter wavelengths in the direction you're traveling.

I'm talking about radiation from other stars or what ever. Imagine if every star in the star field in front of you shifted from visible light to gamma.

I'm sure there is a study out there that describes the exact amount of radiation exposure you would receive at reletivistic velocities due to blue shifting.

The speed doesn't change but the wavelength does. That's why we see light from other galaxies redshifted.

> The tough part is making something capable of a constant 1g of acceleration for a 7 year trip.

Isn't that just a building with an engine in the basement? Seems like one of the harder parts would be making sure it can survive freefall at launch, turnaround and arrival.

> Isn't that just a building with an engine in the basement?

No, it turns out that the requirements of generating thrust (which require generating energy and using it to toss something out the back of your ship) end up running into hard limits in the delta-V you can carry based on the available thrust-generating technology. Surviving 1g of constant acceleration in easy (well, I mean, it requires a certain degree of structural strength, which as mass gets large--which it will even with something delivering a minute payload--becomes challenging because of square/cube issues), but building something that can actually generate 1g of constant acceleration for 7 years is a non-trivial engineering challenge.

> Seems like one of the harder parts would be making sure it can survive freefall at launch, turnaround and arrival.

No, surviving free fall is a non-issue. Literally, that means surviving not having external forces acting on it. There's nothing to it.

My layman's reading of physics-for-layman books has taught me that if we were to travel at the speed of light, we'd convert into energy. However, I'm not so sure about 99.999999% the speed of light. That's really OK, as far as we know?

You are technically travelling at 99.99999% of the speed of light right now, relative to something.

You are actually traveling faster than the speed of light relative to some distant galaxies. The "speed limit" in special relativity refers to an inertial reference frame (in general relativity, this would be a reference frame with no/negligible spacetime curvature). As soon as you have significant gravity/acceleration relative to things with mass, the answer becomes much more complicated (and not fixed).

What determines my speed limit? Is it set at 0 here on earth? What if I travel to another galaxy, this one was going at .5c relative to me when I was on earth. Then after trillions of years, inflation causes all of the galaxies to separate beyond sight from me in this new galaxy. Now, the centre of this galaxy appears at rest. Does my velocity get "reset?"

Special relativity says that no matter what your velocity is relative to Earth you can proclaim that you're actually at rest and it's the other guy that's moving. So your velocity is always continuously being "reset". And in each of the frames of reference of everything in existence nothing else is traveling faster than the speed of light.

The 1905 Special Relativity Theory (1905 SRT) version of reciprocity implies that the other guy in a different inertial frame than your own will be the one that is moving. The consequence of this implication is the "Twin Paradox" (i.e. both twins in different inertial frames have been accelerated and are both aging slower than the other twin). A different version of reciprocity that implies that the accelerated twin is moving and the apparent movement of the twin that has remained stationary is only an aberration (or mirage) is axiomatic because movement first requires acceleration.

Assuming spacetime is not expanding, let's say 1 galaxy is moving away from us at .9c. I leave our galaxy and catch it by travelling at .99c. Then a citizen of that galaxy, at rest, accelerates to .9c. So his velocity relative to earth is .89c? I think I need to go watch a youtube video on special relativity. Intertial reference frames are really weird.

inflation/expansion of space is not limited to the speed of light.

I know. That understanding is already illustrated in my question... I don't see what that has to do with answering it?

As far as we know, as long as you don't actually reach light speed (which is currently thought to be impossible anyway) you can pretty much get as close as you want and be fine.

Thanks. It's quite counter intuitive to think about. You'd be going along at 99.99999999999999999999999999999999% and then hit that last bit and poof now I'm photons.

Well, achieving that "last bit" takes an infinite amount of energy, so it's not surprising that that has some effect.

Yes, as long as you don't hit anything or care about the time dilation you will experience.

Also, and I'm not an astrophysicist, but I believe going fast _relative to Earth_ doesn't make it any more or less likely that you're going to hit anything. Moving at .998c relative to Earth and hitting something that is stationary relative to Earth is the same thing as not moving and being hit by something going .998c relative to you.

EDIT: Right, as chris_va pointed out, we're all traveling at .998c relative to something out there.

> Also, and I'm not an astrophysicist, but I believe going fast _relative to Earth_ doesn't make it any more or less likely that you're going to hit anything.

OTOH, given that it is (like most of the stuff around it) orbiting the center of mass of the Milky Way Galaxy, shouldn't Earth be moving relatively close (within a very small fraction of light speed) to the speed of most of the interstellar dust, etc., in its immediate galactic vincinity, such that moving at 0.998c relative to earth is also moving at a very similar fraction of c relative to lots of other things you are going to potentially hit on a journey from earth to a nearby star system?

Of course. Thanks. This is why they don't put me in charge of our next interstellar trip.

>doesn't make it any more or less likely that you're going to hit anything.

I believe that would be wrong. Also not an astrophysicist but I would guess that most of the stuff in our galaxy is moving at speeds which are, on average, relative to our galaxy, and moving at some average rotational speed around it. Of course there could be stray bits moving quite quickly on through.

So moving at c relative to the planets and solar systems swirling around our galaxy probably would make you more likely to hit something.

Not a physicist, but wouldn't a spacecraft standing on Earth's surface already feel 1g because of Earth's gravity (https://en.wikipedia.org/wiki/Equivalence_principle)?

You can look up Project Daedalus's report online. They considered all these issues in great detail and came up with an affirmative answer.

> Is it plausible for anything we'd build to travel .998c and survive the journey?

The first half is actually a bigger problem than the second half.

The problem is far easier to state than implement.

All about funding. NASA, for example, is about 35 years behind schedule by my math, solely from funding.

Now whether throwing money at a public agency would have made advancements in lensing, transistor along with propulsion technology happen quicker. Thats a tougher question that leans towards the "unlikely".

Funding is not the only issue. Their planning was also a disaster. The Space Shuttle wasted so much money with very little return. If NASA continued with Project Orion and NERVA a Mars colony would have been well established by now.

The Space Shuttle was fundamentally flawed because NASA compromised with DoD to get it funded. Had NASA been fully funded for space exploration alone they would have made better choices.

The rocket equation is the biggest block. Getting a constant thrust of 1g for 7.3 years is hard.

It takes an incredible amount of fuel, and an incredible specific velocity.

> about...2,000 Saturn V rockets

Or about 670 BFRs [1].

It would take 6 cycles of tripling size and/or performance to get a single system with enough thrust to meet your 7/42 year schedule. The Saturn V first flew in 1967 [1]; SpaceX plans to launch its Interplanetary Transport System (ITS) in 2022 or 2024 [2]. That's an expected 60 years to triple performance.

[1] http://waitbutwhy.com/2016/09/spacexs-big-fking-rocket-the-f...

[2] https://en.wikipedia.org/wiki/Saturn_V

[3] https://en.wikipedia.org/wiki/Interplanetary_Transport_Syste...

Though that kind of performance is probably not going to come about from improvements to chemical rockets but moving to fusion. There are some promising developments on fusion reactors (see Breakthrough in Nuclear Fusion? - Prof. Dennis Whyte https://www.youtube.com/watch?v=KkpqA8yG9T4)

Guess something like that with the 100 million C gas doing the propulsion maybe?

Running a direct output fusion rocket in the atmosphere would be tough-- all the reactors we know how to build, or can vaguely guess how to build, run at small fractions of one atmospheric pressure.

If you have fusion engines, you would just be doing all the construction in orbit anyway, rather than boosting stuff from the surface of the orbit.

There may have to be some clever system where you don't take a lot of fuel with you.

Imagine a type of particle accumulator and aggregator - call it cosmic flypaper. If you're going say 100 km/s, things seemingly insignificant and rare you may be able to collect a lot of pretty quickly.

It sounds like you're talking about the Bussard Ramjet. It collects interstellar hydrogen gas for use in fusion engines. The problem is that it's unlikely there's enough hydrogen floating around for it to really work.

Are there places that would have high concentrations of floating hydrogen? You would just need to "fly" through those.

> Are there places that would have high concentrations of floating hydrogen?

IIRC, a Bussard Ramjet is at least potentially viable at the typical density in the galaxy, but unfortunately for any use by humans to get away from our solar system, or local region of space (to a distance, IIRC, on the order of 1000 light years in any direction) is a pocket of relatively low density.

Sure: stars. I don't think flying through those would work out well.

There's also nebulae. But that's only going to be useful when you're actually in a nebula, which isn't most of the time.

To put that 60 years into perspective: It was 66 years between the first powered airplane flight and landing people on the moon.

These kinds of realizations make me sad that life is so relatively short.

It's also exciting, isn't it? That every generation is likely to experience some unique achievement?

Don't forget about space debris. Hitting anything at the posted max speed is just gonna dril a hole straight through your ship. If it's big enough, it'll add some nice shockwaves to really mess up your ship.

Note that GP was talking about the mass of two thousand Saturn V's, not the payload. It would take 20,000 BFR launches to put 6 million tons in orbit.

For anyone (like me) who wants to adjust the parameters while not having to deal with calculus, this[1] "Space travel calculator" works great.

[1]: http://nathangeffen.webfactional.com/spacetravel/spacetravel...

Honestly that amount of mass seems doable (the hard part being a near perfect fusion engine of course).

Just curious about your calculations though. Did you take into account the fact that you could eject spent helium and therefore lower your mass in transit? Assuming most of the mass is fuel, I would imagine by the time you're arriving there would be very little mass left to decelerate.

Upvote for doing the math, but we're going to have to ditch traditional chemical rockets for this kind of trip. Fortunately, we're making progress on alternatives.


Note that he's not giving a figure for a chemical engine, but a fusion engine (sometimes termed a "torchship" due to the absurd power involved.) That would be strictly more efficient than VASIMR or similar. The figure would be even more ludicrous with a LOX/LH2 engine.

(I did not check his math, however.)

At first I was confused about if the star is 39 light years from earth, how come it would take just 41.8 years from the observer perspective (assuming me looking out of the window). But with pen and paper I see that you would be accelerating the first year up to speed of light, then 40 years at almost speed of light and then one year decelerating. What is the efficiency of some current hydrogen -> helium fusion engine?

What's the math behind your estimations? Doesn't sound so unfeasible.

I didn't get the same result. I used the relativistic rocket equation [1], and the change in rapidity from 0 to 0.998c is about 3.5, which means a total change of rapidity of about 7 (static to full speed and then back to static). Assuming perfect hydrogen->helium fusion engine (specific impulse=0.12c) the ratio between initial mass and final mass is 10^25. For comparison the mass of the earth is about 0.6*10^25, or in other words, if you want to send only 2kg of load to this star, you need fuel as much as the mass of the earth.

[1] https://en.wikipedia.org/wiki/Relativistic_rocket

2000 saturn v rockets sounds possible

That's 2000 chemical rockets. The example talks about a perfect Hydrogen-Helium conversion.

the fusion bit not (yet) so much though

If we had a near-perfect hydrogen -> helium fusion engine, why would we want to stop at 2,000 saturn V rockets of mass? Hydrogen is cheap AF.

Also why would we only want to stop at helium, why not fuse any further?

Also why would you want to stop at 1g acceleration - why not 1.5g or 2g, say? Surely living in 2g environment is okay for that period?

However presumably there is no good reason for us to go there. Just because there are planets doesn't make it worth the trip.

What if we used engines powered by nuclear energy (fission or fusion)? Could we reduce the amount of fuel, since the energy density is so much higher?

The GP already posits a theoretical perfect fusion drive.

Ah, yes. My bad.

This estimation was already assuming a fusion engine.

You still need reaction mass.

I don't understand how it could be less than 39 years for the traveler. Time dilation is a thing, but being less than 39 years would mean the traveler observed the planet approaching faster than the speed of light, which should be impossible.

Or does space contract as well?

That's correct. You wouldn't be able to do the roundrip expedition in less than 78 years from an observer's standpoint so you still can't transmit information faster than the speed of light, however from the explorer's point of view it might take a lot less time to do that as you get closer to c.

If you travel at the speed of light (assuming you're a photon or something) then time stops "existing" altogether and you are simultaneously at the point of origin, destination and everywhere in between. At least that's my understanding of it.

I find it both exciting and depressing at the same time, it means that you could potentially make a rountrip to the center of the milky way and back within a human lifetime but by the time you'll be back everybody that remained on earth would be long dead and nothing would be the same anymore. If those types of travels become common then society would stop existing on a single timeframe. It's pretty mind boggling.

How much fuel would it take to get 6 million tons of fuel off Earth into the interstellar ship?

You have a path from earth to a planet 40 lightyears away. There is a planet every K meters that can house a fuel tank to serve as a checkpoint. Let F be the amount of fuel to take a ship between two adjacent planets. Let 0 be the first and L be the last checkpoint.

Suppose a rocket can hold 3F. Go to A, deposit F, and return 2 times. Next rocket goes to B, stopping at A each way to take F -- do the B trip two times. Now you have two tanks at B and none at A. Repeat like binary addition till you fill L-2 with F, then repeat for L=L-3 to L=0. Now each checkpoint except the last and next-to-last has 1F. A final ship can make the trip to the planet, build a civilization, find a fuel source and return with pics.

Are we willing to use a railgun, with a rocket burn at apogee? (So one-half orbit from the starting point: without the burn, the object will hit the ground when it completes its orbit). If so, a lot less than is needed by pure rocket burns, where you have to carry all of the mass used to accelerate to orbital velocity.

Step one, find an asteroid with ice...

The best way would be to use a space elevator pipe for this. But it's still not feasible.

Better off Enceladus. A ship that size probably would be built in space.

If you make the fuel on Mars it will take less effort to get it into orbit. It's also a bit further up the suns gravity well.

Is there any reason to accelerate to the half way point? Accelerating to .99c is much faster and would use much less fuel. It also wouldn't make the travel time much different, to the outside observers anyway.

If you accelerate beyond the halfway point you're not going to be able to stop in time.

I mean you can stop well before half way. 2 years at 1g will get you to .97c and drastically cut the fuel requirements.

Is that just for the rockets? We would definitely need much more than that considering we would also need to carry at least a city's worth of infrastructure, supplies, settlers, etc.

I'm pretty sure he meant a probe. Not a good idea to send a bunch of people to a planet we don't know is habitable (and probably isn't).

We don't have any spacecraft that can go that fast, do we?

No, but we probably could with enough fuel. The bigger issue is space dust. Hitting it at relativistic speeds would be like flying into a cosmic shotgun for the entire journey.

According to this paper, you can travel around 0.5 c before the radiation caused by colliding with interstellar hydrogen kills you: http://www.scirp.org/journal/PaperInformation.aspx?paperID=2...

"Going slow to avoid severe H irradiation sets an upper speed limit of v ~ 0.5 c. This velocity only gives a time dilation factor of about 15%, which would not substantially assist galaxy-scale voyages. Diffuse interstellar H atoms are the ultimate cosmic space mines and represent a formidable obstacle to interstellar travel."

Couldn't you put some kind of "snowplow" on the front so it pushes the oncoming detritus away to the sides?

Could that cause accidental fusion?

Assuming this [1] is reasonably accurate, very much yes. It proposes fusion occurring at speeds as "slow" as 0.9c.

[1] https://what-if.xkcd.com/1/

A large mass of water ice would make a decent ablative shield.

If I understand our capabilities correctly we can't even escape the solar system without using gravity assist boosts from other planets, let alone sustaining thrust for a long period.


"Capabilities" seems a little ambiguous to me. Is it what we have done or what we could do? Using those boosts is a way to achieve the same results, only cheaper. Yes, it's slower than building a big ass rocket, but it seems people that sign the checks are in no hurry.

Also if I'm not mistaken, Voyager probes were not even intended to live so long or leave the system.

If there were a reason to send a probe to another star as soon as possible and no matter the cost, there would be a way, maybe not fast, maybe very expensive, maybe something weird, but it would be done.

I've read about laser systems for sending unmanned crafts at high speed: http://www.space.com/29950-lasers-power-tiny-interstellar-sp...

I think we do if you look at it in terms of acceleration. As I understand it, In space there is almost 0 friction so "fast" is more about acceleration than "top speed". In this view, 1g isn't that fast.

About as "fast" as a helicopter at a stable altitude, or to fit with the no-atmosphere bit, a stationary jetpack or lunar lander (on Earth).

Doesn't energy required to accelerate keep exponentially increasing, though? ke = mv^2

Energy is relative to a frame of reference, and IIUC 1g acceleration of the space vessel is in The vessel's frame of reference, not earth's.

No. If I'm not mistaken we're in the order of magnitude of 0.0001c.

At 0.125g/cm^3 of density, this amounts to a cube of liquid helium about 350 meters per side (43.5 million cubic meters).

For others who don't know how much an American ton is, 6 mil of them = (5.44 * (10^9)) kilograms.

What do you consider a spacecraft though. What is the payload mass ?

How many Saturn V rockets have we launched in total?

Thirteen: the last was Skylab.

wouldn't it be better to plot a course where pitstops could be made at gas giants?

That actually sounds pretty achievable. Difficult, but all within the boundaries of known physics and existing human lifetimes.

Isn't 0.998c unrealistic?

> you had a near perfect hydrogen -> helium fusion engine, it'd take about 6 million tons of fuel (about the mass of the Pyramids of Egypt or 2,000 Saturn V rockets)

That is assuming constant energy consumption to sustain 1g, but unfortunately that's not the case, the closer you get to the speed of light, the more energy you'd need to sustain 1g, and this becomes unrealistic long before you are anywhere close to the speed of light.

Its probably more clear to say that a constant 1G acceleration in the local reference frame takes constant fuel, but produces a progressively smaller acceleration (asymptotically approaching zero as speed in the fixed frame approaches c) in the fixed reference frame you were launched in (or of the point you are trying to reach, the logic is equivalent) because relativity.

Your speed doesn't affect the laws of physics you experience.

A few months ago, I made a simple WebGL app to compare the sizes of our sun and the planets for my 5 year old daughter who was curious. I updated it today to include the TRAPPIST system and see how it compares to our own solar system.


Thanks for the nice feedback everyone. I had some time tonight after work and made an improved version with better selection UI and allows for multiple bodies at once: http://callumprentice.github.io/apps/celestial_bodies/index....

I love it! The fact that you made it for your daughter is even better!

Comparing our sun with Trappist's star is really interesting. Try to compare it with Jupiter. They are almost exactly the same.

Very informative. Nicely done.

Nice done! I didn't know that earth is so small compared to sun.

Really nice work. Bookmarked!

Apparently finds are close enough to us that we should be able "to follow up, to see, for example with the James Webb Space Telescope that we're going to launch [next] year, the atmospheres and also to look at bio-signatures, if there are any" !

Optically? That's nuts! Anyone know how this would work? Can we really expect Webb to measure light diffraction/refraction through a few miles of atmosphere on a planet 40 ly away?

It'll be in the near-infrared, but the light won't be separated from the star. How they observe the atmosphere is that when the exoplanets transit, they block out different amounts of light at different wavelengths. From that, one can deduce an atmospheric spectrum.

Absolutely right. Here is a recent paper on exoplanet atmosphere characterization by JWST: https://arxiv.org/abs/1511.05528 -- the overview is at https://jwst.nasa.gov/origins.html

As you say, the contrast between seeing (star + planet) during a transit, versus star alone, is enough to identify absorption of infrared light by some chemical species.

The simulations in the above paper basically show they can infer some chemical abundances (carbon, oxygen) and some atmospheric parameters (inversion layers) for Neptunes and Jupiters. But probably not for Earths, so not for the system in the OP. Even for big, thick atmospheres, these spectroscopic characterizations take a lot of observation time (like, days).

The race is indeed on to develop instruments and algorithms for this problem -- e.g., detecting CH4 or CO2 in an exo-Earth atmosphere. There's feverish activity in the Astronomy community around this, and post-JWST missions are being formulated to tackle the problem.

Would using a shield to block out the star be good enough to image the planets?


There are a lot of approaches. The Spitzer results in the OP here, and the JWST concept above, is about characterizing exoplanet atmospheres during a transit using spectroscopy.

The concept you link is a "starshade". It's a sister concept to a "coronagraph" -- both use an occulting disk to block out the light from the host star, so that a non-transiting exoplanet can be observed.

One goal is to image exoplanets directly, and another is to gather spectra for characterization. One of two current mission studies doing studies of the two approaches is HabEx (http://www.jpl.nasa.gov/habex/). Obviously, the starshade is more complex/cumbersome/expensive.

Using one method or another, you have to achieve a contrast of about 1e10 between the star and the exoplanet. For every 1e10 photons that come in from the host star, your starshade/coronagraph has to let at most one get through to the detector.

It will depend on the size of the telescope, but for all practical purposes, these planets are too close to their star to see directly. A starshade will be good for Earth-like planets at Earth-like separations around Sun-like stars though.

Can someone explain to me why we don't replicate some of these key platforms like the Hubble and James Webb ST?

It seems like the major limitation for discovery is getting enough observation time for whatever certain point in the sky that scientists are researching.

Why don't we launch a second copy of James Webb?

It looks like the James Webb cost $8.7B to launch. The Hubble $4.7B at launch and $10B through till 2010. So it seems cost is the limiting factor. Replicas might be cheaper, but they wouldn't be kickstarter cheap.

I'd love to see a breakdown of R&D vs Manufacturing, Launch and ongoing operations.

I'm under the impression that R&D is a significant component of the cost in these sorts of "one off" science projects/devices and consequently, manufacturing, launching and operating a second one might not cost anywhere near as much as the first one.

In an attempt to avoid the appearance of politicking, I'd offer that this is not as significant a sum as it may seem initially, viewed in relative terms to... other governmental expenditures.

You should remember that youre not the only one trying to take and spend tax money.

A Hubble or James Webb is easily a billion dollar effort, making it THE major limitation for discovery. No one is investing that sort of money for no return. Honestly, even if they did, it would be frowned upon considering the more important humanitarian investments at hand.

"In 1970, a Zambia-based nun named Sister Mary Jucunda wrote to Dr. Ernst Stuhlinger, then-associate director of science at NASA's Marshall Space Flight Center, in response to his ongoing research into a piloted mission to Mars. Specifically, she asked how he could suggest spending billions of dollars on such a project at a time when so many children were starving on Earth."

I encourage you to read his reply.


The voyage to Mars will certainly not be a direct source of food for the hungry. However, it will lead to so many new technologies and capabilities that the spin-offs from this project alone will be worth many times the cost of its implementation.

Supposedly he is right and NASA money is well spent, it still not implies it is efficiently spent. Furthermore, he seems to writes off aids as a net loss in his analogy, without considering the benefits of children not starving (to death). Which is especially weird with the follow up

We need more young men and women who choose science as a career

/devils advocate

I imagine any intelligent life that evolves on a system with so many planets in such close proximity--many within the habitable zone, and each perhaps with atmospheres and organics--will have a much easier time than we do of pushing forward to becoming a multi-planetary species.

We lucked out with Earth being as hospitable and resource rich as it is, but we're stuck in a deep gravity well with not much in our solar system to compel us to leave. That puts us at a relative disadvantage to other alien species that have the benefit of cheap and interesting neighbors to visit.

I'm jealous to dream of what could have been had we evolved in a differently configured solar system.

..and what problems we don't have they might have!

Planets too close, disrupting each other's ecosystems. The usable ice being distributed amongst several planets when the system was formed instead of a single one.. there's no end to catastrophic possibilities.

This is why I still love sci-fi. Anything you can think of, put it on paper, and it could make for a great story.

Not to mention the whole "us" and "them" separation that would eventually arise the same way we have with our arbitrary borders.

Hmm, wait we were talking about intelligent species, never-mind.

Although they'll have a lot more intense x-ray and UV radiation to deal with. Surviving for long enough from under ice or an ocean might be harder than getting out of our gravity well.

> could have been

You write like its all over. Pretty odd.

No, it's written like a thought on how we as a species would have evolved given the possibility of visiting a close planet instead of the moon at the same age of technology. I mean with closer proximity it would have been a race to a neighboring planet rather than touching down on the moon, and where we are now we could have feasibly accomplished interplanetary travel without issue already.

His comment doesn't even bring up our current situation, but would could have been if we had closer neighboring planets.

I frankly disagree.

> Gillon says that the six inner planets probably formed farther away from their star and then migrated inward. Now, they are so close to each other that their gravitational fields interact, nudging one another in ways that enabled the team to estimate each planet's mass. They range from around 0.4 to 1.4 times the mass of the Earth.

Given that these planets are so close to each other, and interacting with each other gravitationally, how likely is it that their orbital arrangement is stable over geological time?

According to the Nature paper (last section of http://www.nature.com/nature/journal/v542/n7642/full/nature2...) --

We computed [via n-body and other simulations] that TRAPPIST-1 has a 25% chance of suffering an instability over 1 Myr, and an 8.1% chance of surviving for 1 billion years (Gyr), in line with our n-body integrations.

And, further,

However, [these lifetimes] do not take into account the proximity of the planets to their host star and the resulting strong tidal effects that might act to stabilize the system. ... The masses and exact eccentricities of the planets remain uncertain, and our results make it likely that only a very small number of orbital configurations lead to stable configurations. ... The system clearly exists, and it is unlikely that we are observing it just before its catastrophic disruption, so it is probably stable over a long timescale. These facts and the results of our dynamical simulations indicate that, given enough data, the very existence of the system should bring strong constraints on its components’ properties...

If we could do large scale engineering we would engineer something like this I suppose to increase the habitable worlds in a system.

The article mentions the star being an ultra-cool dwarf star, but doesn't give an explanation of what that means. Here's some info from Wikipedia that I found useful:

TRAPPIST-1 is an ultracool dwarf star that is approximately 8% the mass of and 11% the radius of the Sun. It has a temperature of 2550 K and is at least 500 million years old. In comparison, the Sun is about 4.6 billion years old and has a temperature of 5778 K.

Due to its mass, the star has the ability to live for up to 4–5 trillion years ...


Wiki says "TRAPPIST-1 is an ultracool dwarf star that is approximately 8% the mass of and 11% the radius of the Sun. It has a temperature of 2550 K and is at least 500 million years old."


Too young star for alien life hopes?

In the Q&A session they said it's difficult to constrain the age of the long-lived ultraviolet dwarf stars once they finish the active early phase, as their lifecycle progresses so slowly. They live for more than a trillion years, compared to stars like our sun which are larger and burn through their fuel in less than 10 billion years.

It's somewhat counterintuitive, but the bigger a star is, the faster it uses up its fuel, despite having much more of it. As size increases, the rate of fusion in the star's core increases such that the extra fuel isn't enough to prevent the lifespan from shortening. In fact, a common type of supernova occurs in stars that are at least 8 times the size of the sun, burn through their fuel in less than 100 million years, and then go out in style.

Crash course astronomy has some great videos on this stuff: https://youtu.be/PWx9DurgPn8

Typo: Ultraviolet should be "ultracool". Darn autocorrect

> it's difficult to constrain the life of the long-lived ultraviolet dwarf stars

What's the upper bound on their estimate for TRAPIST-1's age?

The upper bound is the age of the universe.

This may sound a bit snarky, but it's actually quite a good boundary.

Current estimations for the age of the Universe are around 12 to 14 billion years, which isn't much compared to a trillion year life span of such a star.

Plot twist: It's actually 2 trillion years old. Everything we know of the universe is wrong! (I'd bet I'm not the only one who'd find that a more interesting option.)

Well, it's "at least" 500m, but is probably much more[1]:

  "Determining the ages of such small stars is difficult because they evolve so slowly over their lifetimes of trillions of years but it is estimated to be in excess of a half a billion years and is probably much more."
And abiogenesis occurred on Earth within about 500m years of the Earth's formation, so life can clearly arise pretty quickly. It's complex, multi-cellular life that seems to be hard part. Although this is based on our observations of a single example.

[1] http://www.drewexmachina.com/2016/05/03/habitable-planet-rea...

I'd be surprised if there isn't other microbe-like life in our own solar system. And the path from microbial to "complex" life is just a matter of whether the environment provides enough energy to support it (nearby sun + photosynthesis in our case). This is because cellular communities will always have certain niche advantages (homeostatis etc).

Complex life developed on Earth because it is advantageous in a physics/evolutionary sense, not because the universe accidentally slipped on a banana. Complex life is only an "accident" in that the search algorithm took a while to find the maxima. Otherwise it's just a matter of running the search long enough, and for that all you need is a star.

> trillions of years

This is off by several orders of magnitude. Like estimating the age of your neighbor to be somewhere around 400,000 years old.

Uh? I think it's widely accepted that our best models of small stars are fairly well understood, and predict that they will continue to fuse hydrogen in their cores for more than a trillion years.

Ah, my bad. I thought the model was in reference to the current age of the star, not the expected duration of fusion.

Referring to an average of 1-2 trillion years as "trillions of years" is either misleading, uninformed, lazy, or a combination of the 3. When dealing with hard science it's important to choose your descriptors wisely. Most readers will not follow up.

Uh, "1-2 trillion" IS "trillions". I'm not sure how you can make that out to be misleading.

Stating "trillions" in lieu of "tens of trillions" or "hundreds of billions" might be misleading, but this is not.

It seems the rest of HN disagrees with me, but when I hear "trillions" I think in plurality of trillions, a handful maybe, but afaik these things don't really live past 2 trillion years

That's because that number is a reference to a plurality of years, not a plurality of trillions.

If you say so, I guess I'm just wrong about this. Thank you for trying to clarify for me, instead of just downvoting me into oblivion like everyone else.

I don't think you're "just wrong," there's definitely some ambiguity. You can use "trillions" to denote the scale or magnitude of a value and also to denote a denomination.

I definitely think it's a an interesting case of context, because if you say a quantity "could even be in the hundreds" it is unambiguously stating it could be within the singular hundreds. But change that into "is in the hundreds" and suddenly you aren't so sure.

Even the term "hundreds" alone seems to carry less ambiguity than its superiors, thousands, billions, etc. The higher the quantity, the more imprecision when using the plural form. I guess I was just trying to encourage a little more precision when talking astronomically, though retroactively I see that I could have been less of a dick about it.

That is not talking about the age, but about the possible life span, into the future.

That's "at least"; the age is a lower limit. These stars basically live forever, even in astronomical terms, and evolve extremely slowly, so all you know is that it's not "young".

> Too young star for alien life hopes?

Not necessarily -- life on Earth may have arisen a remarkably short time after accretion, perhaps even in the first few hundred million years. See this old HN discussion: https://news.ycombinator.com/item?id=10415212

Earth is 4.5G years old, and the earliest undisputed microbial life fossils are 3.5G years old, so that gives 1000 million years.

But we can also say that Earth was cool enough for liquid water 4.4G years ago, and there are some findings suggesting microbial life already 4.1G years ago. So only 300 million years, at maximum.

Moore's Law applied to DNA complexity hints that life could be way older than Earth itself: https://www.technologyreview.com/s/513781/moores-law-and-the...

I suspect something's not right, on their graph, mammals are on the top, but this flower has 50 times bigger genome than a human:


Plants often have much larger genomes than animals due to whole chromosome replications. Since they are much simpler phenotypically this isn't nearly fatal.

I think this is why there is no life on any of the planets. The star is just too young. However, the star could have a life span of 5 trillion years, it is safe to say that life could form on the planets and have plenty of time to develop.

Maybe several times over independently. Hopefully we won't have to speculate long. As Jill Tarter says, "we count one, two, infinity." Still waiting for two, and I hope it happens in my lifetime.

So this star is essentially going to live forever from what I understand (ie trillions of years). It's cool and the habitable zone is close to the star.

So I know nothing about this kind of star but I was reading something last year talking about risks to life. There's of course the obvious like being hit by comets and asteroids, gamma ray bursts and so on.

But there's also CMEs (coronal mass ejections). A CME from the Sun directly hitting the Earth would be devastating. The chance of getting hit by a CME is inversely proportional to your distance from the star just because you occupy a smaller arc from the star's perspective.

I wonder if this kind of star and having the worlds so close would pose a huge threat from CMEs. Does this kind of star even have the same number of CMEs as say the Sun?

Now technically, according to the International Astronomical Union, these bodies can't be planets since they don't orbit the sun: https://www.iau.org/static/resolutions/Resolution_GA26-5-6.p...

"1. A planet is a celestial body that (a) is in orbit around the Sun"

Makes me wonder how much this definition of a planet was motivated by the desire to be able to give elementary schoolers a nice small set of things to memorize.

Edit: actually I might be incorrect about this, the resolution is titled "Definition of a Planet in the Solar System", I'm not sure the IAU actually has a definition of what a "planet" would be outside the solar system, but they may be open to the idea that they exist :)

NASA therefore uses the term "exoplanets":




"An exoplanet or extrasolar planet is a planet that orbits a star other than the Sun. The first scientific detection of an exoplanet was in 1988."

Nature did their own clickbaiting with "alien worlds" in the title which was at least here on HN corrected with "planets" whereas the technical term would be "exoplanets."

Are you saying that they don't orbit their star because some of them gravitationally influence each other?

Or are you saying that nothing outside of our solar system can be a planet?

Either way, NASA should schedule another press release about taking celestial pedantry to a new level.

My understanding is that according to the IAU definition, a "planet" must orbit the sun and not any other star. Kind of reminds me of when people thought the solar system was the center of the universe.

The word planet comes from the ancient Greek word for "wanderer" which they used to refer to the wandering stars, the only stars that moved across the sky in relation the all other stars, only five of them visible, assigned to the gods and one goddess: Hermes, Aphrodite, Ares, Zeus and Cronus. Since then, the definition of the planet had to be modified as there are a lot of bodies orbiting the Sun known today. According to the latest precise definition, even Pluto isn't a planet anymore (but a dwarf planet).

In this light, I don't see the problem in making the difference between the planets (orbiting our Sun) and the exoplanets (orbiting other stars, see my other post here).

These guys however would like to remove the International Astronomical Union's definition from 2006 and to introduce the new with which even the moons(!) of the planets would be called "planets":


As the reporter cleverly summarized, their definition could be simpler stated as, "round objects in space that are smaller than stars." Then there would be around 110 such "planets" around the Sun, and the exoplanets would also be, of course, just "planets."

Their reasoning:

"In the mind of the public, the word “planet” carries a significance lacking in other words used to describe planetary bodies. In the decade following the supposed “demotion” of Pluto by the International Astronomical Union (IAU) [1], many members of the public, in our experience, assume that alleged “non-planets” cease to be interesting enough to warrant scientific exploration, though the IAU did not intend this consequence [1]. To wit: a common question we receive is, “Why did you send New Horizons to Pluto if it’s not a planet anymore?” To mitigate this unfortunate perception, we propose a new definition of planet, which has historical precedence [e.g., 2,3]. In keeping with both sound scientific classification and peoples’ intuition, we propose a geophysically-based definition of “planet” that importantly emphasizes a body’s intrinsic physical properties over its extrinsic orbital properties."

Three of those discovered planets are in habitable zone


Are you basing that statement purely on the appearance of the planets in the artist's conception you linked, or was it stated in another article somewhere?

It was stated by the scientists at the NASA press release. They also stated that all seven of the planets have the potential for liquid water depending on (unspecified) circumstances.

Awesome, thank you.

It was said by one of the scientist in live Nasa TV broadcast https://www.nasa.gov/multimedia/nasatv/

Once again, the universe shows that not only is it strange, it's stranger in ways we can't possibly imagine. This is truly a golden age of space science and, as Kay said in M.I.B., "I wonder what we'll know tomorrow.".

Every time I hear such news, I try to imagine how it feels being there, billions of miles away, looking at sky and saying "wow", I don't think we will be able to travel to distant planets in our lifetime, but thinking about it and trying to create that feeling always feels amazing to me.

If we use what we know about it and recreate the system in VR we could technically experience at least the visuals of being there.

At Voyager-I speed (17km/s) we need just 688k years to get there. Not bad considering the humble satelite doesn't accelerate anymore.

I doubt we'll attempt serious inter-stellar travel before we figure out antimatter or black hole-powered engines. So we may have to wait a century or two.

This century we should be more worried about making fusion-powered intra-solar system travel a common thing, and about establishing large colonies on Mars and several moons.

> So we may have to wait a century or two.

It took some thousands of years to be able to circumnavigate the planet, and some centuries after that to do it quickly and safely.

It feels IST in a matter of centuries from now is extremely optimistic.

100 years if probably too optimistic. 200 years probably isn't. Don't forget our technological progress has been exponential. We've had more progress in the past 100 years than in the entire human history.

We're also supposed to create the "singularity" this century, which will give us orders and orders of magnitude higher intelligence than what we have today. Hopefully we can use that intelligence to create those engines.

I don't know about all of that speculation, but you did give me a nice mental image of a barren, battle-scarred solar system littered with battleships containing black holes, ready to cause catastrophe at any moment, much like the nuclear wastelands of the Arctic.

The black hole engines he's referring to glow very hot because they're very small, meaning that the surface of the hole is large compared with its volume. This allows for very bright hawking radiation if I understand correctly. If you stop feeding them they disappear within hours, years, or decades depending on how big they are.

Yeah, black holes scare me, too. But to me it looks like the most "realistic" solution for travelling 10+ light-years. If we learn how to create cheap antimatter, we may be able to use that, too, but I'm not so sure if we could store that much on the ship for the roundtrip. A blackhole could last us a lot longer (I think around 100 light years, last I read about it - I don't remember the space ship's speed, but probably like 30% of light speed).

Is it a good news for human?

we know if cockroach stay at their nest, we don't suppose to kill them. But if they begin to explore their new world, i.e. Human's kitchen, then we want to kill them all.

"Due to its mass, the star has the ability to live for up to 4–5 trillion years"

So when the rest of the universe cools off and stars start to die, Trappist one keeps on shining and shining... We need to get there. But first, let's get rid of our genocidal tendencies.

It's not just that one. The vast majority of stars, by number (but not by light), are stars like these. The universe might dim, but it won't be dark for a long, long time.

Yes, in all bayesian likeness this is a class of star systems that populates the universe. Suddenly the universe does not seem so dark and foreboding anymore.

The optimism in this thread regarding the practical feasibility of long-distance space travel is encouraging. I truly hope it's just another hurdle for us to technologically overcome, rather than an insurmountable barrier.

Even if it weren't doable, who knows what kind of destiny awaits us as our mastery over physics advances.

Don’t worry, in five billion years that will be some other Earthling’s problem.

Link to live stream on YouTube (supports rewinding) https://www.youtube.com/watch?v=UdmHHpAsMVw

This news is very interesting but how is this different than any of the recent planet discoveries? Anyone mind explaining the significance of this discovery over the others?

1. There are a lot of them (seven). 2. They are all Earth sized. 3. There are a lot of them in the habitable zone (three). 4. Even those not in the habitable zone could contain liquid water under certain circumstances. 5. This star is insanely close-by (39 ly).

Basically, if you're looking for a second Earth, this is an incredible gift. Even if we don't find a second Earth among these seven planets, they could tell us a lot about the likelihood of life around red dwarf stars, which is significant, because the vast majority of stars are red dwarfs. That's in addition to the information they can probably provide on planet formation and makeup.

7 is a very high number of planets in an odd system overall.


PS: Note the above systems may have many planets we don't know about.

The number (as mentioned) is one huge difference. Not necessarily for purposes of exploration, but as something else to consider for part of the Drake equation. It's also another avenue of detection because it's such a small star, that means we can use different methods than just detecting the "wobble" to figure out whether there are planets around the star.

It seems that this could be an interesting system to be targeted by a FOCAL mission. It is the idea to use the sun as a large telescope by using its gravitational sense. One would have to have a telescope placed about 550 AU or so away from the sun, on the opposite side of the system you want to look at.

The magnification could be large enough to analyze features on exoplanets. My dream would be to build a telescope large enough, so that with the help of the gravitational lens of the sun we'd have a google-earth like view of the exoplanets.


I was having hard time imaging 550 AU, so for context ( distances from the Sun):

- Jupiter: ~5.2 AU

- Pluto: ~39.5 AU

- Voyager 1 ~137,75 AU

It'll be interesting to see this reflected in the Drake equation (average number of planets per star that can potentially support life).

It'd be amazing if the number was above 1 (or terrible if you believe in the Great Filter hypothesis).

Is it me or does it feel like they've extrapolated a bit too much from the light of a star dimming at intervals?

I was reading up about earth alternatives recently, and upon realizing the distance was always going to limit us, no matter how perfect the planet, I realized we need to travel at the speed of light.

I think our "best shot" at that right now, is to digitize humans. If we could store consciousness in binary, we could then transmit it at the speed of light (like we do with data every day!). You'd need a receiver on the distant planet though. So, your first 'payload' would have to be the receiver, and it would need to travel the slow old fashioned way :(

If you're going to assume heavy equipment on the other end (ours or "someone else's"), it's not ridiculously beyond our current capabilities to simply transmit DNA sequences along with enough digital training material to "grow" and raise a human population from scratch.

Not to mention the reliability and throughout requirements of such a data link to another planet so far away.

has a mammalian fetus ever been developed to maturity outside of a natural womb?

40 light years isn't a big deal if humans lived to be thousands of years old. That's another solution.

Or cryogenically freeze yourself with instructions to be brought back in a few millennia near the new star system. From the observer's point of view you could be there Tuesday week or so.

Why not just make that first payload contain actual humans? Seems a helluva lot simpler.

Yup, for several hundred thousand year's journey. No problem. :-)

I would just hope my emacs session will stay up that long.

Interstellar tramp.

There are moments of pure beauty in the universe.

You could, and probably would. But, how would you send everyone else? That 'traditional' method (carbon based fuels to propel a heavy payload) is extremely expensive, and slow. So if you ever wanted to send more than just 1 payload, you'd quickly reach resource limitations (namely cost, and time).

Why would you need to send more? Humans are natural von Neumann machines.

I hate to always post links to Greg Egan, but he's sort of the XKCD of SciFi - if there's an out there concept, he's usually written a book about it. In this case Incandescence:


Top review has the best summary: "Egan's story is set in the galactic core, inhabited by a race known as the Aloof, because they seem almost indifferent to any attempts at communication from the Amalgam, the loose network of civilizations that inhabit the rest of the galaxy. However, they do allow thrill-seeking members of the Amalgam to enter their transportation network, digitizing themselves for transmission at the speed of light across the galactic core, instead of the long way around it."

Why humans? People are concerned about the survivability of human species, and it's certainly a noble goal, but at this point it's outside or technological reach. Preserving life, in the other hand, could be doable. We «just» need to take some prokaryotic cells to one of those planets, assuming they have the right environment, and in some million years you have a complete ecosystem...

Assuming also, of course, that there is not life there already.

The whole idea of digitizing humans is silly. It would lead to spooky action at distance. For example what if when humans are digitized you send it to two different machines? Which one would be the real you?

I think the magic speed is actually 10% the speed of light.

What's magic about it?

It's fast enough to get us places in a reasonable amount of time (40-200 years), but reasonably attainable technologically.

I'm having a hard time finding more data on the density of matter in interstellar space.

Wikipedia says

> The density of matter in the interstellar medium can vary considerably: the average is around 10^6 particles per m3 but cold molecular clouds can hold 10^8–10^12 per m3 [1]

But I imagine that interstellar gas would be easier to fly through than interstellar sand. Do we know the composition of matter in interstellar space?

[1] https://en.wikipedia.org/wiki/Outer_space#Interstellar_space

It's almost all Hydrogen/Helium gas. Other larger atoms and molecules are known to exist in the interstellar medium, but it's primary gas.

Also, a good way to remember the density is ~1 Hydrogen atom per cm^3.

We could catch it and use as a fuel or recoil mass!

(does napkin math)

Nope :-(

How about intergalactic densities?

Don't know the number off the top of my head, but it should be considerably less. It should also be highly varying as some galaxies live in pretty densely packed environments (galaxy clusters), which some live in very open environments like our own galaxy.

Nothing like a little "look it up yo damn self": Looks like it's about 1 hydrogen per m^3 [1] (via SO [2]), about 1 million times less dense. Damn.

  [1]: http://www.universetoday.com/30280/intergalactic-space/
  [2]: http://physics.stackexchange.com/questions/25378/how-vacuous-is-intergalactic-space/25379#25379

So, who do we call to make sure the newly discovered planets are named Chimay, Orval, Westvleteren, Rochefort, Westmalle, Achel, and La Trappe?

40 light years = 12.2 parsecs.

I mean I feel like an opportunity was missed here...

Even though each of the 7 planets are likely tidally locked it seems a habitable zone on each planet is still a possibility [1]

[1] http://nautil.us/blog/forget-earth_likewell-first-find-alien...

I would also like to point out: Giordano Bruno was right. https://en.wikipedia.org/wiki/Giordano_Bruno

Although, he had no proof for his intuition, so I cannot entirely cherish him as a martyr for modern cosmology.

When I looked at the image[1] illustrating size/mass/orbit periods of TRAPPIST-1, I was fascinated by the orbit period:

6.10 days, for example, for planet e! Suppose we were to be able to stand on that planet and stargaze outwards, won't that be extremely dizzy? :)

So what are the immediate (strange) properties brought forward by median of 6 days of orbit period?

[1] http://www.space.com/images/i/000/062/962/original/trappist-...

Earth has a rotation period of 1 day (around itself). When stargazing a 1 day rotation period would be the same as 1 day orbital period whilst being tidally locked (which seem to be the case for these planets)

I don't think anyone is getting dizzy down here so I would assume it would be the same there? or have I missed something?

So how come when NASA tells us there are tiny invisible planets light years away we all applaud, but somehow when they point to the evidence of climate change right here right now it's all a big con?

For one thing, many of the people applauding the discovery of extra-solar planets do not thing climate change is a con.

And, conversely, many of the people who think climate change is a con are indifferent to extrasolar planets.

"It is very hard for a man to believe something when his salary depends on not believing it"

This strikes me as a rather disingenuous question.

why? either you think NASA is good at science or you don't, you can't pick and choose depending on whether or not you like the results

Okay, sure. I can give you a serious answer if you'd like.

First of all, you're attempting to take down some strawman. _Who_ is applauding this discovery, and simultaneously calling NASA's climate change research "all a big con"? It's disingenuous when you just present a (IMHO) off-topic opinion that the majority of the other commenters here have, in the form of an innocent question. If you would like to discuss the view of a public figure or other commenter, that's fine. If you want to discuss how you think that people should accept NASA-related research as a whole or not at all, that's fine.

But don't ask a false question to take down a strawman.

Second, your statement "either you think NASA is good at science or you don't" is a massive trivialization. NASA is a 19 billion dollar organization, with over 17,000 employees (not counting contractors). Beyond the problems of the phrase "good at science" (What does it _mean_ to be "good at science"? That's an incredibly complex topic.), NASA is huge, with many, many different people and departments, opinions and beliefs, cultures, etc. Thinking of NASA as a fixed, singular, cohesive entity is a flawed assumption.

And I guess finally, to get back to your original question, it's quite straightforward. The (economic, political) implications of habitable planets 40 light years away is quite different from the (economic, political) implications of American industrial and economic activity needing to be massively changed, very quickly.

Don't get me wrong, I'm a firm believer that climate change is a human-caused phenomenon. But I don't feel that your original question was presented in the best possible way.

> either you think NASA is good at science or you don't

That's a false dichotomy.

Its quite possible to think (I am not endorsing this belief, only saying that it is not self-contradictory) that a large organization like NASA has people doing good and non-politicized science in certain areas in certain areas and bad and politicized science in others.

In fact, one could quite internally consistently believe that NASA does good, non-politicized science in some domains deliberately as a means of generating credibility so that people accept the bad, politicized science it does in other domains.

Ok Elon, only 39 light years away. When will you take us there?

I wonder if SETI are going to point at it, you know, just incase :)

They're only one Kessel Run away!

Or, maybe our Zyra.

Let's go

It's a Trap ;)

On a serious note, if we can travel close to the speed of light , say 95%, using for example, nuclear rockets, how long would it take to arrive ? ( from the travellers perspective )

At a constant 1g of acceleration, you could travel there, from the traveler's point of view, in ~2-3 years. (And in ~40 years from a stationary observer's point of view.)

Mind you, a constant 1g acceleration (Or accelerating any human-carrying spaceship to relativistic speeds, really,) is about as plausible as a spaceship driven by pixie dust and unicorn farts.

You would just blow by it though. If you wanted to stop there, your ship would have to turn around and aim the unicorn farts forward to decelerate you 1g the second half of the trip, bringing the time to ~7-8y

If pixie dust is plutonium and unicorn farts are tetradeuterium-methane, you could get there in 400 years or so, Earth-time, 398 years shipboard time.

So you really need your pixie dust to be antimatter, and your unicorn farts to be terawatt lasers.

For now, the wait calculation suggests that anyone leaving now will reach their destination after someone who waits to leave until after the next breakthrough in space propulsion technology.

I see "antimatter" and "black hole" being thrown around as a source of propulsion in this thread.

Is this based on anything real like using the energy created from the radiation or just sci-fi speculation?

Positrons cost $25M/mg and antihydrogen costs $62.5B/mg.

An interstellar trip to Alpha Centauri using antihydrogen-hydrogen annihilation reactions would cost more than 50 years of the entire economic output of the planet (as of 2016) just for the fuel. Since we need a large portion of that economic output for basic survival needs, there will be no antimatter rockets built any time soon.

As far as I am aware, we currently lack the capability to create a singularity massive enough to persist long enough to observe as a black hole. But it is possible that we might be able to locate a primordial black hole near enough to build a propulsion system around it, or even trap one as it passes through Earth. This would, of course, require that primordial black holes exist, and that they emit Hawking radiation.

Yes, for now it is purely speculation. Anything beyond chemical-energy rockets is speculation until we actually demo the technology in a real spacecraft. If you launched today, bound for Alpha Centauri, the best you could do is drop fusion bombs behind your vessel until you get to about 0.08c, turn around at some point and throw fusion bombs in your path to decelerate, and be prepared to arrive a long, long time from now.

Not according to public research on theoretical designs that have been about for decades . Unless you consider them unicorn farts! I'm only a coder though so I have no knowledge of this domain tho. I think the problem is simply it's too expensive to build space ships that probably won't work at all :( wasnt NASAs budget slashed ?

It's not money, it's the basic rocket equation: Newtonian acceleration requires fuel and the mass of fuel makes acceleration more costly.

Relativity makes things even worse.

See comment above yours, does your point still apply?


oh ok , you win , thanks for your replies ^_^

> Not according to public research on theoretical designs that have been about for decades.

Which ones? Do you have a link? The only one I remember is https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls... but it's more a general idea that a detailed blueprint that only need some money to get built.

Thats the one I read. It sounds awesome.

Srsly give me 5% of the GDP of the US and I'll put a monkey on Trappist within 5 years. Monkey time.

*Im not being serious, I have no idea how much it would cost or if it would even work.

Project Orion doesn't get you anywhere close to 1G constant acceleration to turnover and constant deceleration the rest of the way; a fairly high performance Orion concept for interstellar use did have 1G acceleration, but only for 10 days on each end of a 133 year trip to Alpha Centauri -- and needed 300,000 nuclear bombs with 1 megaton yield each as fuel.

> Srsly give me 5% of the GDP of the US and I'll put a monkey on Trappist within 5 years.

No, you won't. First, you won't design and build and launch a ship that will ever get to TRAPPIST-1 within 5 years at that (or any) price, and second TRAPPIST-1 is close to 40 light-years away, so even if you had a ship built and ready to launch today, you aren't getting anything there within 5 years.

Thank you for your feedback, however with all due respect, with my limited understand, if the acceleration is achievable, you are wrong.

The monkey would arrive, like I said, in monkey time, within 5 years. This is ofcourse assuming there would be no deceleration phase.

The monkey would unfortunately however, die on impact.

Give me 0.1%, and I'll put a vanOverbruggen "Suzanne" model into a photo-realistic virtual reality imitation of one of the Trappist planets, and I'll throw in reduced head-motion lag in the viewing headgear at no additional charge.

Can I have half of that to design the marketing website?

Well it is approximately 40 light years away from our solar system. So the basic calculation would say about 42 years but this doesn't account for acceleration and deceleration and such.

The answer for an outside observer is: @ 1g of acceleration it would take 11 months to accelerate to the speed of light. A formula you can put in Google is: (285000000/9.8)/(60x60x24).

So 39-(.475x2) = 38, and 38/.95 = 40. So 42 years is your answer.

I have no idea how to calculate the relativistic spaceship's elapsed time.

It's all wishful thinking. The fastest thing man has created, the Juno spacecraft, travels, by some quick calculations, @ 0.00147% of the speed of light.

This isn't how it works. As you approach the speed of light acceleration becomes less effective (i.e. you feel 1g but don't get faster at 10m/s^2).

The interesting thing is that it's actually easier to calculate in the spaceship's reference frame. The two relativistic distortions cancel out and the Newtonian calculation gives the correct answer. So if you accelerate for the first half of your journey it takes you sqrt((28500000040/2)/(365246060*9.81/2)) = 6 years, and the same amount of time to decelerate, meaning 12 years in total.

>you feel 1g but don't get faster at 10m/s^2).

how does this work? it's consistent with what I've read about c requiring infinite energy, and I'm sure it has something to do with relativity, but I don't have an intuitive sense of it

It's 39 light years so no fewer than 39 years from our perspective. The closer to the speed of light the travelers are the less time will appear to have elapsed from their perspective. If you had rockets that could instantaneously accelerate to infinitessimally close to the speed of light, no time at all would appear to have elapsed from the travelers perspective (or no time that they would notice), but this is very unlikely.

Well, it's estimated that it will still be around in 4-5 trillion years, so, if we can get there, and it's habitable, that gives humanity a little longer lease in the universe.

Source on the 'trillions of years' number?

"Common" knowledge; the brighter the star the faster it burns. Sun-like stars last billions of years, dwarf stars last for trillions, the real giants last for millions.


I got you -- The accompanying Nature paper gives a 10 trillion year figure.

Do we know definitively that there are no other planets in this system?

The presence of a large, Jupiter-sized planet in a system is thought to be helpful for deflecting asteroid impacts. Obviously we are talking 'to scale' given TRAPPIST-1 itself is around the size of Jupiter!

The more we learn about this system is going to be fascinating though - the supposed inward migration of these planets may even help us understand more about how our own system formed.

I don't think we know for sure, but it'd be hard to place another star in the system and have it a) not disrupt the planets and b) go unnoticed as the primary star is so faint.

Is it possible there isn't an asteroid belt to be concerned about?

Based on Voyagers current speed it would take approximately 18000 years to reach this system, the referance of a jet airplane taking millions of years seemed a bit misleading, with current technology and using gravitational boosting I would think that the time could be much less. Maybe it would be worth sending a probe? Granted I will never see it in my lifetime but it might be a project I could get behind.

18k years is a very long time, though. There is a project looking at the feasibility of getting very small probes somewhere 10 times closer in perhaps decades rather than millennia:


That is exactly what I meant, thank you for the link. I defiantly would support projects like that.

I suspect you meant definitely and not defiantly.

Probably used jet airplane more of a frame of reference for the general public.

Unless you're talking about a Starshot-type probe, I think it's probably better to wait for improved propulsion technology that would end up arriving before a probe we sent now.

12 parsecs?

No problem, buddy. We've got the best ship in town. If you've got the dough I'm sure me and my buddy Chewy can work something out for ya.

Is this from NASA news conference that was announced for today? I couldn't find it in article? They said they have important announcement.

Yes, the exoplanet discovery was the important announcement.

Therefore it appears as there are plenty of habitable planets out there. Numbers are big enough to conclude that other life is definitely out there somewhere so are the questions:

1. Where are they all?

2. How humanity will react on appearance of one of them? Will we finally stop our fights inside that sandbox and to focus on challenges that we are facing all together?

So, are there any plans to try to "communicate" with this planets? Or we are going to just sit and watch.

Well, we could send a message and then wait 80 years for a reply. So we might want to work on immortality first.

I thought we were already working on immortality. On the other hand, waiting 80 years doesn't seem like much. It's not like we are going to be 'out for lunch' if there is an answer.

Here is another article on it with a bit more info on the planets


Question to HN: If you can go, knowing you cannot get back, would you go to colonize the first planet?

Fun detail, the discoverers are Belgian and Trappist is a name for a monk beer.

We Belgians sure like our beer :)

Depending on how habitable those planets are, if there was an actual entity modeling the universe for humans as some close minded ideologies tend to think, well we would be living there and not in a little blue island in the middle of desolation. Nice blow.

With so much proximity between worlds and seemingly easier access to nearby space and it's resources, I feel that any sentient life in a system like this will have had a massive evolutionary advantage over us.

Close orbit around a relatively cold star. Interesting. I wonder what their 'day' vs 'year' looks like. Also their atmosphere and surface pressure. They could be 7 copies of Venus for all we know.

> Because the planets are so close to Trappist-1, they have quite likely become “gravitationally locked” to the star, always with one side of the planets facing the star, much as it is always the same side of Earth’s moon facing Earth.

Also, during the live stream they said that the furthest planet does a complete orbit around the star in 20 Earth days.

So there are likely no 'days' on any of these planets and a 'year' goes by in less than a month on Earth.

If they are tidally locked as reported, then there will be no day, not really. Just as there is no day on the moon.

The moon rotates once every ~27 days, so its day is ~27 days. It's just in sync with its orbit of the earth, so it appears to us that it doesn't rotate.


Isn't that technically the moon's "year"?

A year generally refers to the time something takes to make one revolution around its closest star.

Uh oh.

The "great filter" hypothesis is essentially that the rarity of intelligent life has to be explained by some parameter of the Drake equation, and that whatever the "small" parameter is is either in our past or in our future.

If the "great filter" is the rarity of habitable worlds, then clearly we don't need to fear it, since we already found one. But if habitable worlds aren't rare, then it's more likely it lies in our future (e.g. global thermonuclear war, plague, difficulty of space travel, etc).

Thus things like discovery of exoplanets, bacteria on mars, etc should make us rather concerned.


The theory as described in your link seems to hand-wave away the difficulties incumbent in the "colonization explosion" step. As it stands, intergalactic space travel (at scale) is utterly inconceivable in practical terms, and to simply assume that it is inevitable seems like a major flaw in the theory.

> then it's more likely it lies in our future (e.g. global thermonuclear war, plague, difficulty of space travel, etc)

Difficulty of space travel is one of the possible filters.

Ah. I guess I was responding to

> the only thing that appears likely to keep us from [colonization explosion] is some sort of catastrophe or resource exhaustion leading to the impossibility of making the step due to consumption of the available resources (like for example highly constrained energy resources).

Actually, the article explicitly calls out that step as one potential "great filter". It also (click the link) lists the theoretical ways it could be accomplished.

It seems to leave out the Von Neumann Probe:


This is not exactly colonization but possibly an easier step. Either way, the point is that if either we or our machines can get to another star system and repeat the process from there, exponential growth means it pretty much doesn't even matter how long it takes. In astronomical time, we'd cover the galaxy in the blink of an eye.

But what if we are the first and no filter exists at all?

That's almost equally depressing. "Really, we're the best the universe has to offer?"

That's not depressing. It gives us a moral imperative to transplant Earth-origin life onto every somewhat concentrated mass that we can reach.

Then we can wait a few billion years, and the universe will likely have generated a superior successor species which can then re-seed over everything we had previously tilled, and then some.

And they'll all be rubber-forehead aliens to one another, because they'll be billionth cousins, a few million times removed.

Who is to say we aren't already transplants just looking to reconnect with our cousins?

That's what I'm saying!! Panspermia

Think about it, in so many sci Fi, the aliens are pretty similar to us. Carbon based, have DNA, etc.

If we seeded the galaxy with our life then a billion years from now we might get a star wars type reality where many species coexist together all because we seeded every corner of the galaxy.

> It gives us a moral imperative to transplant Earth-origin life onto every somewhat concentrated mass that we can reach.

And in the very likely scenario that we are never able to "reach" outside our solar system... Then what?

> And in the very likely scenario that we are never able to "reach" outside our solar system... Then what?

Then we need to prepare for the Gliese 710 arrival over the next million and change years. [0]

[0] https://en.m.wikipedia.org/wiki/Gliese_710

Then we will either be literally extinct or at least economically extinct--permanently unable to recover space-launch technology. Then Earth has to gin up another dominant species capable of reaching the stars with whatever time it may have remaining.

We already have the technology to reach outside the solar system. It launched in 1977.

We will have the capability to transplant microorganisms to extrasolar planets long before moving humans that may have 100kg or more to one. Which is good, because it may take a while for the algae to get established anyway. And if for some reason higher species never show up, that celestial object won't have to overcome the steep initial hurdle of abiogenesis.

I expect the first species that is physically capable of colonising the stars will /only just/ be capable of it.

This is the best Earth has to offer is how I prefer to think about it. Though I am not even sure humans are the best we have to offer anyways.

Isn't that highly unlikely due to the age of the universe vs age of the Solar System?

The "Transcension Hypothesis" is a possible solution to the Fermi Paradox...


Great link, thanks.

Cant help but be reminded of the premise of the Halo games, and the objectives of the alien race.

Just for curiosities sake, using the best technology humanity could get its hands on, what's the best case for the time it would take to reach that solar system?

StarShot [1] is gunning for 20% of the speed of light. At that speed, it would take a couple hundred years.

[1] https://breakthroughinitiatives.org/Initiative/3

4 separate front-page posts about this on H/N so far..

Just curious, how is this related to us considering there are ziga-billion-stars/planets not-yet-be-found in the universe, why is this news important?

While the system itself is nothing extraordinary from a detached, theoretical point of view - we are aware that there are many planetary systems in the universe of all sorts and sizes - what makes this news so impressive in my opinion is the thrill of actually witnessing, almost tangibly, such an alien and wonderful system, excitingly different from our own (read the article in detail, fascinating stuff), amplified by the fact that these planets are relatively quite close.

Basically, the system is so peculiar and close to us, now that we have actually discovered it is difficult not to be fascinated by it, even though we know it's nothing to be perplexed with in the grand scheme.

My fav thing about the universe is the idea that evolution + ingredients in another order could create something totally bizarre and wonderful!!

Let's do this.

James Webb Space Telescope is going to accelerate all of these discoveries by x100...star KIC 8462852 is clearly aliens!!!!

Now we just need a 40,000 generation ship.

Is there information already on how the short distances between planets would affect G-forces felt on surface?

The earth moon distance is tiny, and the G-Forces are hard to directly measure.

That's still soo far away though.

This is an exciting bit of news. 40 LY is relatively near compared to size of our galaxy.

Have we ever detected exo moons? If not when or how might that be possible.

I cant understand what can we possibly achieve from this type of explorations. NASA spends lot of money each year to excite us but nothing really achieved. Personal thought: Isn't worthy to spend this money for alleviation of poverty in this planet?

it's ~65$ per person per year. I am not American but if I were I would gladly give 65 bucks a year for some space related excitement.

Well, lets hope on these guys to take us there ;)

Apparently they are building a FTL engine. http://www.spacewarpdynamicsllc.com/latest-news

Let's change #OccupyMars to #OccupyTrappist ;-)

Let's bring some democracy there again!

See? I told you that seven is a magic number.

could we send a spaceship there as a projectile rather that have (all) the fuel on board?

I wonder how many javascript libraries they're up to already?

That gave me a chuckle. Safe to say they would be post-React by now, but probably still pre-SingularityJS.

it's worth mentioning that the light we receiving took 39 years to arrive to the telescope. So anything we see happened 39 years ago.

I thought it'd be nice to know...

No, it's 39 light-years away.

Meaning that anything there that we can observe happened 39 years ago. Not 39 billion or billion.

Just to make sense of that reply: I remember the post was talking about 39 billion years but seemingly was edited without advice.


I knew it.

raises the question

We detached this subthread from https://news.ycombinator.com/item?id=13707913 and marked it off-topic.

That's essentially what blueprint said. You didn't have any trouble figuring out what blueprint was saying, right?

It's an incorrect and jarring usage of the phrase. Plenty of folks on HN are non-native speakers who benefit from knowing when colloquialisms are used incorrectly.

The transitive form "Begs the question <question>" is long attested, quite common, very clear and readily distinguishable from the intransitive form "Begs the question" [with no direct object], which refers to the petitio principii fallacy, when people prefer a translation into somewhat archaic English to the Latin.

In fact, the attempts I've seen to quantify usages (including those by prescriptivist pedants still trying to pedal the idea that the intransitive usage is the only correct one) find the transitive usage to be the most common, even in publication.

The intransitive use can even be seen as a generalization and rationalization of the transitive use, wherein the transitive use becomes equivalent to the intransitive use with an implied direct object of "the question which the argument was intended to resolve", which (while not the original etymology of the intransitive form) actually makes the intransitive form sensible and has a closer relation to the modern English sense of the words in the phrase than the original etymology of the intransitive usage.

Prescriptivist pedantry on this point is, if this is possible, even more obnoxiously pointless than that directed against the singular usage of "they".


What's wrong with begs the question? It's a regular part of my vocabulary and I'm a southern American.

I think this article sums it up:


tldr: Begs the question is a formal term for when a conclusion is not supported by given arguments. Using it the way most people do is technically incorrect, but has become common enough that it is in the gray area where one can consider it the new correct usage.

"Begs the question" refers to a logical fallacy[1], though in modern language usually it's conflated with "invites the question" (which is what people generally mean when they say "begs the question" outside of a comment thread on Reddit).

[1]: https://en.wikipedia.org/wiki/Begging_the_question

It's true that people use it that way without issue in everyday conversation, but technically "begging the question" is a logical fallacy in which a statement/proposition presupposes its own truth.

See http://begthequestion.info/ for further info (and a laugh that this site exists).

'begging the question' is the name of a specific logical fallacy and is not grammatically correct. You could say 'begs for the question' or as the parent comment suggests...

Physicists have got blinders on. Once we solve the gravity problem everything changes. I've been searching for a decade for scientists who can confirm my info but tbh most everyone seems to have abandoned themselves already.

We detached this subthread from https://news.ycombinator.com/item?id=13708611 and marked it off-topic.

> Once we solve the gravity problem

I have a feeling I'm going to regret asking, but here we go: what "gravity problem"?

You're familiar with the fact that there is no proper, substantial, accepted model or principle of both gravity and EM that unify them, correct? And we don't knowingly have the ability to build technology that manipulates gravity (trivial interpretations aside). And we also don't know how our actions actually affect the dynamic field that is gravity. Cause the stress-energy tensor says it is dynamic. Or perhaps I'm just completely bonkers. Life certainly would be a lot easier if I were.

What exactly are you saying? That once we really figure out gravity, faster-than-light travel will become possible? I've been saying that for years, and I'm no physicist. It's fairly obvious that gravity is not well understood by our physics. All we really know is that it correlates to the presence of mass: lots of mass (like a planet) equals a noticeable amount of gravity. Unlike electromagnetism, where we have the ability to actually create it and manipulate it at will, we have no such ability with gravity (aside from just moving mass around, which has little effect since gravitational force is so weak). So yeah, I've thought for a long time that understanding gravity is the key to warp drive, just because it's such an obvious blind spot. But I'm not sure how this is helpful; merely noticing that our understanding of gravity is poor doesn't actually help us understand it any better.

What we need is to discover a physical effect whereby we can significantly manipulate gravity at will. Figure that out and you'll change everything.

General relativity gives a very solid and accurate understanding of gravity.

It does? Great; please point me to some instructions on how to build an anti-gravity device. I can easily build myself an electromagnet with some wire and a battery, so if our understanding of gravity is so great, I should be able to do the same with gravity, right?

Understanding something doesn't mean you can manipulate it in any way you want.

When it comes to physics, it does in fact mean you can use the principle you discovered in engineering technology. That's kind of the whole point.

By the same 'argument', understanding the laws of thermodynamics (which prohibit perpetual motion) allows us to exploit perpetual motion?

No one's talking about perpetual motion here. Understanding the laws of thermodynamics allows us to build heat engines, which is how many of us got to work this morning. It also allows us to build nuclear reactors (or at least the steam-cycle part of it), which is how many of us get the power to write messages here.

What does our "understanding" of gravity allow us to do technologically? Nothing, because we have zero idea of how to manipulate it. The only thing we can do is understand how it works in the natural world so we can, for instance, navigate space probes accurately and get our GPS satellites to work. That's great and all, but it falls far short of the level of understanding that we have with thermodynamics and electromagnetism.

It's probably futile to argue with you but have you considered maglev trains?

Yes, that's an application of Maxwell's laws of electromagnetism. That's not manipulation of gravity, it's using the MUCH stronger EM force to overcome gravity.

I can overcome gravity all by myself just using my muscles to lift things. That doesn't mean that I've manipulated gravity in any way.

I'm really shocked that I seem to be the only one who groks the difference between observing a natural physical force and actually understanding it well enough to manipulate it and generate it at will. We cannot generate gravity. We can generate EM fields, and we can also generate nuclear energy by splitting or fusing atoms (which means we're manipulating the nuclear strong force, to an extent).

> observing a natural physical force

There's your misunderstanding. Gravity is not a force. The force is merely the effect you observe on your specific instrument. The cause and substance of gravity is not explained solely by its effect (force), and the force is not what generates gravity, et al. And, in fact, mass is not the only thing that generates gravity. It's flux of energy density. So it boggles my mind that no one considers EM energy as a subset of the energy that can produce "stress on space".

Conclusively, you've made some assumptions you don't realize resulting in an uncontrolled thought experiment. When terms are defined incorrectly, questions using those terms become wrong. If the questions are wrong the answers also always come out wrong.

That's a form of name-calling, which we've asked you repeatedly not to do here. If you keep doing it, we will ban you.

FTL etc is a conversation for the future, like a few related topics; but no, the important thing right now I'm saying is that global warming is the first step of a process that we believe has got to be mediated by gravity, and that academia in general doesn't realize what's going on. This needs to be investigated in depth, and this is probably not the venue. You're welcome to contact me.

What the heck are you talking about? Global warming is simple and easily explained by the available evidence: too much carbon in the atmosphere increases the greenhouse effect. All the arguing is how much is "too much" and exactly how much of an effect it'll have. The gravitation of the planet hasn't changed significantly in eons; the atmosphere has because of all the pollution we dump into it.

One sentence in your comment is accurate. I'll let you figure out which one.

It's not like there aren't people working on figuring out how gravity works: https://en.wikipedia.org/wiki/Quantum_gravity

Crackpot alert!

> The launch cost of launching the mass of the pyramids of gaza into orbit would bankrupt the richest economies.

Yeah… cause the way you're thinking about doing that is literally the only way in the world to accomplish the task. Not. It's not my job to qualify whether it HAS to be done to you. And even though I am the one presenting this information and this evidence, it is indeed your job to confirm it. Otherwise, you're not exactly doing science, are you? Nor are you really acting in your own best interest or that of mankind. It's almost as if you're fighting to rationalize doing nothing. You're free to do that. Just be honest about what you're doing, please. Sacrificing yourself is your choice. But you shouldn't deceive others in order to take them with you.

We detached this subthread from https://news.ycombinator.com/item?id=13708568 and marked it off-topic.

I don't think the way you are arguing your points does you any favors.

Well, literallycancer, that begs the question of why nobody helps me with their ability and suggestions to argue better. I have had to do everything on my own. The way this message of mine is treated is perhaps the reason for or the reflection of the fact that mankind's usage of science and technology seem predetermined to lead to destruction. But feel free to ignore me. Everyone does whatever they want regardless of their reason, facts, or personal truths, anyway.

Your posts here have been pretty disparaging toward the scientific community. The scientific community does have problems with groupthink and cognitive biases, but it also has to contend with a flood of people who passionately defend idiosyncratic ideas without appearing to appreciate what counts as a scientific theory or scientific evidence. Every scientist and other technical domain expert has encountered dozens or hundreds of people offering the secret of why science is totally on the wrong track. (I don't work in physics or climate science, but I've experienced this in cryptography and number theory, which do relate to my job.)

In order to be taken seriously, I'd suggest that novel physical theories should accurately use existing technical vocabulary and notation (and define and explain the motivation for any new vocabulary), be expressed in quantitative terms, not pick a fight with the scientific community or impugn its good faith or intelligence, and hopefully make empirical, testable predictions (including better-explaining observations compared to existing theories).

If I were attempting to propose a novel physical theory here, I would do exactly what you say. And in fact papers and apparatuses are being worked on. But here my point that we ought to establish another basket for our eggs stands entirely independently of the validity of such a theory/proposal. And what's interesting is how hard the push-back still is.

Space exploration and colonization have always been extraordinarily contentious issues, regardless of people's take on particular existential risks. I know people who think space colonization is unequivocally the most important thing humanity can possibly do, and people who think it's among the least important or maybe even actively wrongful. I don't think you can expect to find clear consensus on this point right now. But at least an Elon Musk-style "we should be working on permanent human presence in space to mitigate risks to humanity's survival" idea is relatively mainstream on HN.

Elsewhere in the thread you seemed to strongly disagree with other commenters about the expense of space travel, seemingly based on a technical proposal that you want to make, and you were dismayed about other people's reactions to your ideas. But in at least some views, the empirical questions about cost and feasibility must matter a lot, because space colonization doesn't mitigate every problem or risk humanity faces and might not appear as the only or best option for mitigating some of them right now.

Your technical ideas might cause you to weight some of these risks and costs very differently (for example, it sounds like you think human extinction on Earth is relatively likely soon and space travel can be made drastically cheaper than it is today), but that kind of disagreement puts you back in empirical-technical territory.

Why are people so excited about planet which is 39 light years away, when we are living in a society where 8 hours of slavery is required to survive. This is not listed focal.

That attitude is why you are subjecting yourself to 8 hours of slavery!

May be u r right

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