
Sad Trombone Exoplanet Reality Check - cstross
http://www.antipope.org/charlie/blog-static/2016/08/san-trombone-exoplanet-reality.html
======
deanCommie
When I was a boy in the Soviet Union in the late 80's, I picked up a book on
computers. It was targeted towards children, and talked about a lot of
different components and ideas from bits and bytes to RAM to networking, and
interesting applications like barcodes.

I remember my mind being blown by barcodes. But the idea seemed far-fetched
and unrealistic. To put a barcode on EVERY single item in the grocery store?
That would take decades to implement!

Then we emigrated to Canada and I was shocked to see it was already in place
(and must have been for a while).

Maybe this isn't the best example of tremendous human achievement but it
taught me to not take for granted what is unrealistic and how quickly humanity
could achieve it if we put our minds to it.

With apologies to Cliff Stoll and his magnificent brain, let's not forget a
pretty common perspective on the Internet from 1995:
[http://europe.newsweek.com/clifford-stoll-why-web-wont-be-
ni...](http://europe.newsweek.com/clifford-stoll-why-web-wont-be-
nirvana-185306?rm=eu)

Space exploration and rocketry is not cheap, and requires new innovation. Only
SpaceX is doing anything on that front. But if humanity set getting to Proxima
Centauri as a goal, I have no doubt we could achieve at least kicking off a
single-generation journey within my lifetime (ie sub-80 year journey time in
the next 80 years)

~~~
jwr
Humans are capable of incredible achievements. But it is unlikely we will
achieve interstellar travel any time soon. We are too busy fighting wars
(relicts of the stone age, really), improving our advertising technology, and
just generally slacking around and looking good in the process.

Thinking is hard. It's easier not to think too much.

~~~
carleverett
Humans were busy fighting wars, improving its advertising technology, and just
generally slacking around when the internet was being born as well.

It only takes a very tiny portion of this world's 7 billion people to be smart
and motivated enough to create a breakthrough for the entire planet.

That said, interstellar travel is an order of magnitude more difficult, so I
agree it won't be happening very soon.

~~~
the_duke
I'm surprised that the internet so often comes up in the context of humanities
great technical achievements.

Don't get me wrong, a seamlessly interconnected network of computers has
changed society and our lives tremendously.

Technically speaking, it was not that remarkable of an achievement though. We
already had some forms of remote communication for quite a while (telegraph,
telephone, radio).

With the rise of computers, connecting them was bound to be the next step, and
not that much of a challenge as far as hardware and technology goes.

The actual (technical) achievement was the computer.

------
alanbernstein
> note that 4.25 light years isn't an order-of-magnitude improvement over the
> previous winners for Earthlike proximity, such as Wolf 1061c (13.8 light
> years away) or Kapteyn B* (12.76 light years away). We're talking about the
> difference between 40 arbitrarily-huge-units and 100 arbitrarily-huge-units.
> So how should we contextualize these arbitrarily-huge-units?

This is nonsense. The point is that the exoplanet was (potentially) found
orbiting the nearest star, which means it's as close as it can be.

------
douche
The physics of space travel are harsh, and the distances involved even
harsher. Plus, unless you want to go screaming by on a fly-by mission, you
have to burn all that delta-V you generated to get there in order to slow down
again.

The only real solution will be some kind of essentially magical faster than
light technology - never say never, but it doesn't seem likely without some
staggering breakthroughs in areas of physics we don't even have an inkling
about.

Maybe it's the American exceptionalism and internalization of Manifest Destiny
as the natural order of things, but the idea of being effectively stuck, as a
species, on this one rock for eternity is pretty depressing. Especially if
that is the fate, not just of ourselves, but of all life intelligent enough to
look up at the stars and imagine walking among them. If the best we can hope
for is a Motey-like[1] Malthusian cycle, it's not much to look forward to.

[1][http://amzn.to/2b5I0Ea](http://amzn.to/2b5I0Ea)

~~~
barrkel
It is possible to leave this rock, but we'll need to think in terms of
millennia, not lifetimes. Long term thinking that's also kind of unAmerican.

~~~
wingless
[https://en.wikipedia.org/wiki/Generation_ship](https://en.wikipedia.org/wiki/Generation_ship)

------
Sniffnoy
Note in the comments Peter Erwin points out that Charlie has overestimated the
density in the (relevant portion of the) interstellar medium by several orders
of magnitude: [http://www.antipope.org/charlie/blog-static/2016/08/san-
trom...](http://www.antipope.org/charlie/blog-static/2016/08/san-trombone-
exoplanet-reality.html#comment-2008437)

------
DanBC
> Currently, the most distant visited body in the solar system is Pluto, at
> 7.5 billion kilometers. The New Horizons probe flew past Pluto on July 14,
> 2015. It was launched on January 19th 2006 by a booster and upper stage
> combination that blasted it straight up to solar escape velocity, with a
> speed of 16.26 km/sec (58,536 km/h), making it the fastest human-made
> vehicle ever: it then executed a Jupiter gravity-assist flyby to slingshot
> it out past Pluto, where it arrived nine and a half years after departure.

Lots of people have no clue just how big the solar system is, and how small
the planets are in comparison. (Never mind the distance to exoplanets). Here's
one video that gives a nice demonstration using a soccer ball and pin heads,
from Mark Rober (who worked on a Mars rover at Nasa):
[https://www.youtube.com/watch?v=pR5VJo5ifdE](https://www.youtube.com/watch?v=pR5VJo5ifdE)

~~~
swang
Bill Nye demonstrated it pretty well on his tv show. Very easy for kids
(including me when I first saw this) to comprehend.
[https://m.youtube.com/watch?v=97Ob0xR0Ut8](https://m.youtube.com/watch?v=97Ob0xR0Ut8)

------
lmm
It's disingenuous to talk about Fukushima as a "meltdown", or imply that it
was dangerous (on the scale of space-travel dangers).

The Project Orion design was for 10% of light speed, and didn't assume any
scientific breakthroughs like fusion - it would require a massive amount of
engineering , but the core technology (that used in nuclear weapons) was
mature in the '70s.

We're still talking about a 40+ year journey, for a craft whose cost was
estimated at $367B at the time - about $2.5T now. It's not easy by any means.
But it is doable. We'll get there.

~~~
creshal
> a craft whose cost was estimated at $367B at the time - about $2.5T now.

So we can pay for it with just the money _mismanaged_ by the US armed forces.

~~~
aetherson
No you can't, Jesus, read the actual article. The entire yearly budget for the
US armed forces is around $600 billion.

They had $2.5 trillion in adjustment lines that mostly netted out, they didn't
actually lose track of $2.5 trillion, because they didn't have $2.5 trillion
to lose track of.

~~~
Houshalter
That's a yearly budget though. This craft could be built over many years, so
the comparison makes a bit more sense.

~~~
creshal
It _would_ be built over several years anyway, you can't get a project of that
scale done and ready in a year.

------
Udo
I wasn't aware this reality check was needed, but it's worth noting that we
haven't even left Earth yet (going to the Moon doesn't really count, and we've
since lost that capability again). If we were a solar-system-wide
civilization, I can see how it would make sense to talk about the
feasibilities of interstellar travel, but today we are so far off it's not
even an issue. We also don't have _any_ ambitions to change that, so
extrapolating from today's state of affairs, we'll probably remain thoroughly
Earth-bound until we reach a tech level that enables _individual people_ to
have space programs (if we ever get there).

It's fun to think of probe-based exploration, but apart from
acceleration/energy based problems we haven't even figured out how to make
machines last that long. This is all very, very far off.

~~~
jakub_h
> going to the Moon doesn't really count, and we've since lost that capability
> again

What we've lost is will. The capability is definitely better today, even
though still not affordable enough to fit today's budgets.

~~~
Houshalter
Well I think he means we couldn't just go to the moon next year, even if we
wanted to. All the engineers and factories and equipment behind Apollo is
scattered or lost. It would basically require starting a whole new moon
program from scratch and designing and building entirely new spacecraft, etc.

~~~
Udo
Indeed, yes, that's what I meant. But Jakub isn't wrong either, we lost the
will too. But I thought I addressed that, but apparently not clearly enough.

------
makmanalp
> This veritable speed racer of an interplanetary probe would thus require a
> mere 31,600 years to reach Proxima Centauri (if indeed it was pointed in the
> right direction, which it isn't).

Holy cow, that's multiple times longer than humanity has even existed as a
civilization, and in all likelihood it might perish before that probe could
even make it there. What a reality check. I don't think incremental
improvements are going to cut it for space travel.

~~~
a3n
So we should send one out now, and hope we're still around when it gets there.

And each time we complete development of something better send one of those.

Can you imagine how pissed we'd be 31,000 years from now, not having sent
whatever we finally determined to be the best we could do, when we could have
done it? It may take N thousand years to get something there, but only four
years to get data back. It's worth it.

~~~
danbruc
Designing a machine that still works in 31,600 years seems a pretty tough
challenge. Even remembering to listen for a signal in 31,600 years is probably
already a hard problem.

~~~
a3n
> Designing a machine that still works in 31,600 years seems a pretty tough
> challenge.

Good point. I'm quite sure we can already point something somewhere and it'll
get there, or close, in 31K years. So the real challenge is what you point
out. And remembering is maybe even more challenging.

So the first one out ought to be very simple. Maybe it just pings home every N
days. That would mean that we'd start out listening for it, and perhaps that
infrastructure would be taken care of.

And maybe that first one would die before it arrives. But if we continue to
send something better each time we're able, I think we'd eventually have
success. And if we do continue to send things, maybe we'd have an
institutional tradition of listening for the original.

~~~
danbruc
Just a ping from four light years away does not seem worth the effort to me,
it seems just slightly above throwing a rock in the direction of Proxima
Centauri. At least take a picture.

By the way, there is also a thing called wait calculation [1] which deals with
this very problem, when should you start an interstellar journey. There is not
much of a point to start today if you can cut the travel time in half in, say,
a hundred years since you would pretty quickly overtake the mission started
today and arrive first despite the fact that you started a hundred years
later.

[1]
[https://en.wikipedia.org/wiki/Wait_Calculation](https://en.wikipedia.org/wiki/Wait_Calculation)

~~~
a3n
> Just a ping from four light years away does not seem worth the effort to me,

That's all Sputnik was, a ping in orbit. But it was worth doing to get
something, anything at all, in orbit. Sputnik itself wasn't important, but the
knowledge and experience gained was.

You don't not throw a Sputnik up because you know that decades later you'll
have the ability to throw up a space station. Sputnik is part of the space
station process.

------
throwawaytire
The title of this article sounds like a password [1].

Whenever one of these articles comes out I like to think of this fun paper:
[2] Are Black Hole Starships Possible?",
[http://arxiv.org/pdf/0908.1803](http://arxiv.org/pdf/0908.1803)

[1] [https://xkcd.com/936/](https://xkcd.com/936/) [2]
[https://en.wikipedia.org/wiki/Black_hole_starship](https://en.wikipedia.org/wiki/Black_hole_starship)

------
sklivvz1971
> 4.25 light years isn't an order-of-magnitude improvement over the previous
> winners for Earthlike proximity, such as Wolf 1061c (13.8 light years away)
> or Kapteyn B* (12.76 light years away).

Wrong. It _is_ , quite literally, just about a order of magnitude better.

~~~
dTal
Maybe in base-3...

~~~
daveguy
He was probably referring to base e (2.718281828).

------
FiatLuxDave
I know Charlie is a writer, not a radiation physicist, nevertheless... major
'units' fail in his radiation calculation. 6 Trillion alpha particles per sq
meter per second is 6 TBq per m^2; not 6 Tbq per m^2 per second. TBq as a unit
already includes the "per second". In other words, you wouldn't get a
Fukushima release every eight days - you'd just get about 1 millionth of a
Fukushima... and that's it (per m^2, of course), as long as you are moving
through an interstellar medium as thick as he posits at that speed.

160 Curies is a dangerous amount of radioactivity, but nothing outrageous. I
often work with gamma sources much larger than that. I use a 1000 Curie source
that easily fits in a sq meter, and it's used the same shielding for over 20
years.

------
JumpCrisscross
Sounds like a riveting to-do list, with lots of big implications for the folks
back home.

> _We 'd need a whole raft of breathroughs, including radiation shielding
> techniques to kick the interstellar medium out of the way of the probe_

Game changer for nuclear power and propulsion, in terms of safety. If we did
this with matter, that means we can get closer to hot things [1]. If we did
this with energy, ha! - we can now start harvesting edge-of-magnetosphere
antimatter and explore mining and terraforming using directed energy.

> _as well as some sort of beam propulsion system_

If we can beam massive amounts of power _out_ that means we (a) have massive
amounts of power up there and (b) can beam (a) home [2].

> _and then some way of getting data back home across interstellar distances_

Either we figured out how to keep lasers (or some other stream of stuff)
columnar over super-long distances or we broke new ground in information
theory. Either way, getting a grainy picture home from Proxima Centauri on an
apple of an energy budget means getting lots more closer to home around faster
and more efficiently.

[1]
[https://en.wikipedia.org/wiki/Star_lifting](https://en.wikipedia.org/wiki/Star_lifting)

[2]
[https://en.wikipedia.org/wiki/Dyson_sphere](https://en.wikipedia.org/wiki/Dyson_sphere)

------
exratione
Focusing on habitability from our perspective seems somewhat parochial.

From the perspective of colonization: by the time future sentients descended
from or created by present humanity get to other planetary systems, we-for-
some-definition-of-we would be capable of living anywhere, and space and
novelty will be things that you get by computing more efficiently, not by
going places.

From the perspective of adding data to the Fermi Paradox: assessing the
possibilities of life being out there by looking for places in which bacteria
of the known varieties could survive probably tells us little about the true
range of life.

From the perspective of resource assessment: by the time descendant entities
get to other systems, it won't much matter how the matter there is
distributed. It will used efficiently whether a gas disk, rock and ice
condensations, or (improbably) somehow all in the star.

------
mjsweet
When I read articles like this, I like to imagine that we are already on a
multi-generational ship (earth) and are on our way to see the wonders of the
Andromeda Galaxy :)

------
mozumder
NASA should over the next 100 years build a hyper-telescope, so that people
can begin to actually see these planets in detail before before a probe can be
sent.

Even with current technology, a hyper-telescope could be self-assembled in
space, built from billions of 3-d printed & smoothened mirror segments, all
aligned to half wavelength of visible light. We need to have a 1000px x 1000px
resolution of earth-like planets out to 100 light years away, which would be
several thousand miles in diameter.

~~~
dredmorbius
That's all but impossible. To optically resolve an Alpha Centauri planet of
Earth size at Hubble resolutions of Pluto (about 680 pixels square) you'd need
a 28 km wide scope (or array).

[https://www.quora.com/How-big-would-a-telescope-have-to-
be-t...](https://www.quora.com/How-big-would-a-telescope-have-to-be-to-see-
Kepler-452b)

Rather than seeing _shapes_ of objects, detecting their _signatures_ \-- light
occlusion, spectroscopy, thermal and radio signatures -- is far more useful.
Several of those would reveal chemistry and radiation indicative of life
and/or intelligence.

Much xenoplanetary analysis isn't done through optical telescopes, per se, but
through spectrographic analysis, which tells us what _compounds_ and
_elements_ are present (or are blocking / reradiating) starlight.

~~~
DenisM
Nothing wrong with a 28 km array though, if we can put it in space.

Besides, what about dynamic aperture? I know very little about it, I only
heard that a moving camera effectively expands it aperture by the distance
traveled within the duration of the exposure.

~~~
dredmorbius
You're going to want _both_ light gathering _and_ range.

Keep in mind, a planet is probably going to be moving a lot over the course of
a few hours. A 24 hour time-lapse of the Earth will give you a lot of pretty
colours. But not much by way of a useful image.

You're trying to see something _tiny_ and _dim_ a _very_ long way away, next
to something which whilst also _tiny_ (relative to the Universe) is far, far,
far brighter.

A long-duration moving-apature exposure of a remote planet next to a dim star
seems to me not to be an ideal candidate for high-quality imaging. I'm not
sure a large-baseline, large-collector array would do much better, but at
least it could narrow the time interval somewhat.

(Though I think you're still basically going to end up with a glared-out,
underexposed, blurred pixel.)

------
bogomipz
The title of this blog post is one of the funniest I've read on HN, really
made me laugh.

The author states:

"We might get a small probe up to arbitrarily high velocities if we cheat by
using an engine that stays back home where we can keep it running, but then we
run into other problems."

Does anyone know which rocket propulsion technology he is referring to there?
In the paragraph before he is referring to plasma beam but he doesn't say what
this is.

~~~
TheOtherHobbes
The goto site for discussions about interplanetary and interstellar anything
is Centauri Dreams:

[http://www.centauri-dreams.org/](http://www.centauri-dreams.org/)

------
StreamBright
Excellent read, so much insight. We really need those gates from "The Expanse"
series.

------
Sharlin
Interesting that he doesn't mention the Breakthrough Starshot concept at all.

~~~
Freaky
It's mentioned in the comments:

> As for the Starshot thing, that sounds like a reboot of Robert Forward's
> Starwhisp idea from the 1990s. The real problem with that is, how to get any
> data back from it. (Not to mention how to construct a continuously operating
> gigawatt laser array in space).

------
heisenbit
Just finished reading "The three body problem". A civilization on planet in a
system with 3 suns would have some interesting challenges.

------
bluejekyll
So what you're saying is, "we need a bigger rocket!"

I agree. It's high time we started on near light speed space travel.

~~~
Pxtl
We need cheap matter-energy conversion. Nothing less will provide enough
energy for interstellar travel, and cheap matter-energy conversion may not be
possible _ever_. Whether the engine is here or there, the amount of energy
needed to launch a properly-radiation-shielded craft is simply obscene.

------
intrasight
I don't understand the focus of the article being on sending a physical probe.
Why not just send a radio message? Something like "Is there anybody out
there?"

I've heard the argument that we shouldn't advertise our existence in case
there are hostile beings. But can't we assume that all intelligent life is
constrained by the same rules of physics? And why assume hostile?

~~~
scott_karana
The round trip time for such a message would be 9.0 year, so getting our
signal discovered, _and_ getting it mutually intelligible, could easily never
happen, even if there was life there.

~~~
dredmorbius
Clearly, part of the trick would be to figure out what to send, and to keep
sending it.

Well, that, and figuring out _how_ to send it.

Though when you've got the resources of a habitable planet at your back,
generating strong signals seems more viable.

------
digi_owl
Thermodynamics is a real downer...

~~~
Pxtl
Imho the entropy laws are the real heartbreaker. They're the ones that explain
how the universe doomed.

~~~
dredmorbius
But they're also the reason we're here in the first place.

Shiva the destroyer, Brahma the creator, Vishnu the preserver.

------
mcguire
Bah! That's an engineering problem.

------
Synaesthesia
Same story for colonising Mars, or even sending astronauts there. It's pretty
much unfeasible. Yes maybe we could send some people there but the costs
involved are so astronomical that it really can't be justified. We're stuck on
this planet and we need to make the best of it.

~~~
Joof
And yet, two organizations have plans to do so in the next two decades.

~~~
Synaesthesia
Yeah a handful of astronauts can go there. But everybody else is stuck here.

