A Breath Of Sense

We all need one now and again. So here’s a young Carl Sagan, in his pre-turtleneck days, talking about aliens visiting us:

A bunch of years ago, I got into a long rolling email conversation with some friends, trying to establish how we felt about the Drake Equation and Fermi’s Paradox. It seemed to me at that time that a low-effort take on the whole thing is to shrug at the Drake Equation and say “sure, it shows there are probably loads of alien civilizations out there.” And the answer to Fermi’s Paradox is also a shrug: it turns out that getting up to relativistic speeds is elusive and all of the alien civilizations, like us, are stuck like flies in amber in their local regions of space. The macguffin of “hyperspace drive” or “wormhole drive” or whatever features prominently in the alien civilizations’ science fiction book sections – just like it does in ours – but it staunchly remains science fiction and every civilization winds up slamming face first into the problems of the high frontier, which cannot be overcome, and they eventually either die struggling or become stoics and die quietly. It’s all very well and good to imagine signalling aliens by banging a couple of black holes together, or whatever, but it just doesn’t happen.

My theory is that civilizations arise, build their equivalent of a Hubble Space Telescope, take a good look around, think about it, refine their theories, and then say “Well, that’s it. We’re stuck here. Phooey.”

Science fiction ideas that there will always be newer, better tech, are for folks like Ray Kurtzweil – who seem to assume that just because humans are pretty clever that we will eventually become infinitely clever. That there is no limit to how far we can evolve our technology. That’s a neat daydream but if you look at the way we’re swirling down the drain of fossil fuels and overpopulation, I don’t see any reason for unbounded optimism. We’re getting to the point where we understand how batteries work and are bumping up against theoretical limits there. We understand how chemical rockets work and we are bumping up against theoretical limits there, too. We understand how to make fusion and are bumping up against limits there. Maybe not all limits can be overcome through enough hard work. What if it’s an actual hard limit? Expanding into our solar system may be too hard for us. Sure, “we’ve got to.” But that doesn’t mean we can.

Charles Stross has a really interesting thread on this stuff over at his blog [stross] and inevitably there’s Kim Stanley Robinson’s Our Generation Ships Will Sink [boing]  We can optimize a bit like leaving the testicles at home[stderr], but we need everything to be vastly better than it is for any of this stuff to become anything like practical.


  1. polishsalami says

    One problem that we keep bumping up against is the inability of the human mind to comprehend the distances involved in space travel. Our brains weren’t built to conceive such vast numbers.

  2. says

    Yeah, I tend to suspect that practical interstellar travel isn’t possible, and that even if technological civilisations are common they simply can’t get here no matter how far ahead of us they might be. I think even such things as the self replicating probes a lot of people hope for are probably far harder to do than people think, and may not be doable at all.

  3. brucegee1962 says

    I agree that we’re probably stuck here. That doesn’t explain why we aren’t at least picking up some signals from elsewhere, though.

    The scariest solution I’ve heard of for the Fermi paradox is that, shortly after a culture announces itself by broadcasting, SOMETHING from a previously evolved society shows up and makes them be quiet. With “shortly” being in astronomical terms, ie. a few centuries.

  4. says

    I think even such things as the self replicating probes a lot of people hope for are probably far harder to do than people think, and may not be doable at all.

    The problem is always power systems and energy density. For the self-replicating probes to ‘work’ you need a portable civilization kit that can build a civilization capable of building a relativistic probe, out of anything. May as well just assume we’re going to figure out teleportation and be able to beam ourselves around.

    I had a conversation about this once with a friend who’s a future-leaning sort, who said that with matter/antimatter reduction as a power source, it could be done. Then you get things like calculating, assuming a perfect transfer of the energy from the matter/antimatter into propulsion, you’d need an antimatter tank the size of a freight train to get to Barnard’s star in a few decades. And the “not in my backyard” types would have a point if someone proposed to make a trainload of antimatter anywhere near a planet with billions of people on it.

    I get the wish fulfillment aspect of it: we are a species that explores and are curious. But, as Sagan points out, there’s a serious suspension of disbelief when people start talking about aliens joy-riding to Earth to visit trailer parks and anal probe people. And, by the same token, we’d have to be an even stupider civilization than we are, to invest our planetary economic output for a decade or two into sending an instagram to the universe, knowing that the odds were vastly on the side of it being unseen by anything.

  5. says

    SOMETHING from a previously evolved society shows up

    If you haven’t read Chixin Liu’s trisolaris series – that’s what it’s all about. Cool stuff.

    I think that extreme distance explains enough. Our civilization is relatively new and only would have been able to understand a signal for at most a couple hundred years (fudging heavily) – so a signaller would have to hit that tiny time-window over a distance of millions or billions of years (given lightspeed propagation delay) And it’s got to be expensive, no civilization would waste their economy to go whacking black holes together to send gravity signals when all they would be sending is an interstellar twitter posting.

    To me the scariest hypothesis is that civilizations arise, get bored, and give up faster and farther away, and that humanity will never hear their dying sighs of ennui and nobody will hear ours either. (substitute “ruin their environment or die of overpopulation” for “get bored” if you will)

  6. says

    Our brains weren’t built to conceive such vast numbers

    Yeah. When we’re talking 100,000 years of time, that’s as long as humans have existed in their current form. We can’t contemplate travelling on that scale (even if we could build ships that could do it) because by the time the travellers got somewhere, humanity would be gone, having turned into something else.

    That raises a question, which is – when people talk about saving humanity by going to the stars – unless the trip’s pretty quick the humans that leave will not be humans when they arrive, nor will they remain humans for very long. And the humans they left behind will turn into something different in the meantime. It’s not like “humanity would be saved” because humanity is a pinpoint moving target in time.

  7. says

    I just had a thought:
    What if most civilizations grow, senesce, and die in the time before they could be detected, and signalled. Since detecting a civilization is equal to getting a signal from them, and sending them a signal is approximately the same length of time, you could be looking at a million years or more.

    So, if Kepler-186, which is 500ly away, appeared to be about to evolve a civilization, we’re looking at events there that are 500 years in the past. We might, at tremendous expense, send them a cosmic instagram, only to see the blips of fusion release as they blow themselves up before they are aware we tried to say “hi!”

    Of course you can get around half of that problem by switching to a broadcast, but then you’re going to get contacts trickling in 300,000 years after civilization has collapsed.

    I guess another answer to the Fermi Paradox is, “bad timing.”

    I been in the right place
    But it must have been the wrong time
    I’d of said the right thing
    But I must have used the wrong line
    I been in the right trip
    But I must have used the wrong car
    My head was in a bad place
    And I’m wondering what it’s good for

  8. Rob Grigjanis says

    getting up to relativistic speeds is elusive

    Even if we could attain a reasonable fraction of the speed of light, the density of interstellar matter, and the ubiquitous cosmic rays, would make it like flying through a relativistic hailstorm in the core of a nuclear reactor.

  9. wereatheist says

    I like the bow-shock pictures of Ζ Ophiuchi ploughing through the interstellar gas & dust with fairly non-relativistic speed.

  10. says


    It can take its good old time about getting where it’s going, as far as I am concerned…

    What is the bow shockwave in? What is being displaced forward by the star’s motion? I don’t understand how this works.

  11. says

    Rob Grigjanis@#11:
    Even if we could attain a reasonable fraction of the speed of light, the density of interstellar matter, and the ubiquitous cosmic rays, would make it like flying through a relativistic hailstorm in the core of a nuclear reactor.

    I remember in Pohl’s Tau Zero the ship had a problem because their Bussard rams got better and better the faster they went. I’d always assumed that science-fiction writers use a mcguffin like “space warp” to get around that problem. Space travel would be no fun at all if you periodically winked into a spray of plasma.

    Hey, maybe you’d know… I’ve encountered people who like this fictional Alcubierre drive, which sort of wronkles space-time up in front of it, so you can get through faster: wouldn’t it have a problem that space-time isn’t empty (as you say) and pushing through would result in a brief, bright, flash? I think the Alcubierre drive idea sounds crazy, and the energy requirements are handwaved away, but some people seem to think it might work.

    @#10: That was surreal. Time paradox and Walter Cronkite, with light sabers.

  12. Rob Grigjanis says

    Marcus @14:

    wouldn’t it have a problem that space-time isn’t empty (as you say) and pushing through would result in a brief, bright, flash?

    Yeah, when you “exit” the drive, you basically incinerate everything in front of you. Anyway, apart from apparently requiring negative mass, it suffers the same problem as any FTL; it can violate causality. Under certain circumstances, you could return home before you left.

  13. Rob Grigjanis says

    Also: did you never watch SCTV (where the skit came from)? Best comedy show of the late 70s to early 80s, IMO.

  14. Rob Grigjanis says

    Marcus @7: Re “Right Place Wrong Time”. I just remembered Dr John was a guest on an SCTV episode; he played a role in an extended noir-ish sketch, during which he played, IIRC, “Such a Night”. Other guests at other times included The Tubes (doing “Sushi Girl”), and Joe Walsh. Good times, man.

  15. says

    Rob Grigjanis@#18:
    It’s the same phenomenon as the solar wind meeting the earth’s magnetosphere.

    Aha. Yeah, I understand that. Picture me slapping my forehead – of course!

    I’ll look it up on youtube. I’m a huge fan of the Doctor. If you are, and haven’t heard “Doctor John plays Mack Rebennack” take a look for it. It’s him just jamming the kind of stuff he grew up playing before he became The Night Tripper.