> 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.
this reminds me of one my favorite films ever. it is just four minutes long
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).
See also: the timelapse footage of the sky from the VLT, Paranal. Just thinking about it gives me vertigo.
"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.
http://vignette4.wikia.nocookie.net/startrek/images/2/29/Vul... [edited for direct .jpg]
So, what did J.J. know, and when did he know it? And for that matter, how did he know?
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.
 the reversibility it the hard part. Tech for halting metabolic processes irreversibly has been around for quite some time ;)
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.
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.
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.
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.
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.
The battery life is really good though.
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.
> 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.
Then 0.27^3 = 0.0197
And then, only 60% as dense (no core) so 0.0119 :)
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.
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).
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?
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.
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". :-)
What do we know about the gas giants' cores?
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.)
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.
But certainly someone here knows more than I do about it ...
edit: Mongo from Flash Gordon
> 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.
One of the astronomers, Triaud has been quoted saying this is a relatively calm red dwarf that doesn't produce a lot of flares.
Makes me think of the film Another Earth
Let's just say that it's definitely an art-house film. Some find that sort of thing boring, but not everyone.
I propose we name it "Dinklage."
Tidal locking . 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.
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.)
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.
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.
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.
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.
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  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.
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'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).
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.
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 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?"
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.
"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:
In other words, we could get to the Trappist-1 star system in about 145 years.. practically in the blink of an eye.
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.
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.
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.
The name they chose for their programs are quite funny with belgian references: SPECULOOS and TRAPPIST.
There are 11 trappist beers in the world (of which 6 are brewed in Belgium).
Speculoos is a Dutch/Belgian cookie.
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)
Depends on the plot needs for the ~~episode~~ journey.
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.
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.
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.
Edit: Oh, HN, you are so humor impaired sometimes.
Edit: Oops, I cancelled my downvote.
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.
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. :\
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.
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.
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.
How would you know?
Though I don't share your assessment that that is a productive place to direct citizen input on this (or any other) issue.
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:
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.
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.
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.
Still probably higher than extinction from war in the same time frame.
Life on earth could end in the next five minutes. :) https://www.youtube.com/watch?v=RLykC1VN7NY
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.
. . . actually I have absolutely no idea how you would practically do that at all.
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.
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.
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.
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?
Sure this is a problem but it's one that already exists today, not necessarily only when we start building space craft in orbit.
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.
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.
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.
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.
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.
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.
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.
It just takes a lot of time to plan and build ships for space travel.
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.
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.
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.
We know exactly what climate change is and it has nothing to do with gravity.
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.
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.
That's why you need a navigational deflector dish.
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.
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.
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.
EDIT: Right, as chris_va pointed out, we're all traveling at .998c relative to something out there.
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?
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.
The first half is actually a bigger problem than the second half.
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".
It takes an incredible amount of fuel, and an incredible specific velocity.
Or about 670 BFRs .
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 ; SpaceX plans to launch its Interplanetary Transport System (ITS) in 2022 or 2024 . That's an expected 60 years to triple performance.
Guess something like that with the 100 million C gas doing the propulsion maybe?
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.
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.
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.
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.
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.
(I did not check his math, however.)
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.
Or does space contract as well?
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.
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.
"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."
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.
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.
Comparing our sun with Trappist's star is really interesting. Try to compare it with Jupiter. They are almost exactly the same.
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.
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 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?
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.
I encourage you to read his reply.
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
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.
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.
Hmm, wait we were talking about intelligent species, never-mind.
You write like its all over. Pretty odd.
His comment doesn't even bring up our current situation, but would could have been if we had closer neighboring planets.
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?
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.
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...
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 ...
Too young star for alien life hopes?
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:
What's the upper bound on their estimate for TRAPIST-1's age?
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.
"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."
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.
This is off by several orders of magnitude. Like estimating the age of your neighbor to be somewhere around 400,000 years old.
Stating "trillions" in lieu of "tens of trillions" or "hundreds of billions" might be misleading, but this is not.
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.
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
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.
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?
"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 :)
"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."
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.
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."
"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) , 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 . 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
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.
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.
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.
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.
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.
Even if it weren't doable, who knows what kind of destiny awaits us as our mastery over physics advances.
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.
PS: Note the above systems may have many planets we don't know about.
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.
- Jupiter: ~5.2 AU
- Pluto: ~39.5 AU
- Voyager 1 ~137,75 AU
It'd be amazing if the number was above 1 (or terrible if you believe in the Great Filter hypothesis).
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 :(
I would just hope my emacs session will stay up that long.
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."
Assuming also, of course, that there is not life there already.
> 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 
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?
Also, a good way to remember the density is ~1 Hydrogen atom per cm^3.
(does napkin math)
I mean I feel like an opportunity was missed here...
Although, he had no proof for his intuition, so I cannot entirely cherish him as a martyr for modern cosmology.
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?
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?
And, conversely, many of the people who think climate change is a con are indifferent to extrasolar planets.
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.
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.
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 )
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.
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.
Is this based on anything real like using the energy created from the radiation or just sci-fi speculation?
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.
Relativity makes things even worse.
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.
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.
> 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.
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.
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.
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.
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
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.
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.
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?
We Belgians sure like our beer :)
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.
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.
Difficulty of space travel is one of the possible filters.
> 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).
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.
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.
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.
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. 
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.
Cant help but be reminded of the premise of the Halo games, and the objectives of the alien race.
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.
Apparently they are building a FTL engine.
I thought it'd be nice to know...
Meaning that anything there that we can observe happened 39 years ago. Not 39 billion or billion.
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".
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.
See http://begthequestion.info/ for further info (and a laugh that this site exists).
I have a feeling I'm going to regret asking, but here we go: what "gravity problem"?
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.
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.
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).
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.
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.
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).
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.