22 thoughts on “Why Would You Go?”

  1. This particular article is a problem I’d like the human race to have. But my take is that someone or something would mess it up. Just like how Europe was in the 18th through 19th centuries, the height of human civilization yet many Europeans still moved elsewhere.

  2. I would think that would be the easier part. Once you’re used to living in a space colony, it’s not much different to be on an interstellar spacecraft. There’s also the exponential growth issue, which means you don’t have to persuade any significant fraction of the population to go, just a few thousand. If the system population is tens or hundreds of billions, I can’t see the problem. You’d be able to find 1000 people for just about anything you can think of (I mean, we’ve had volunteer cannibal victims).

  3. The ‘are we alone?’ question always seems to run afoul of the ‘reverse Copernicus/Galileo problem’. That is: Making the assumption that we’re -completely- normal.

    The local cosmology and solar system development just doesn’t support that.

    1) Local group has -two sigma- higher than normal Fe/H ratio. (Translation: we had abnormally high supernovas, and are several generations ahead of the curve for higher-than-helium. That translates into billions of years ahead of the average of the Milky Way.)

    2) The late moonstrike appears to have concentrated the heavier elements in the crust of Terra as well. The worthless crap ended up as the moon, the pre-strike moon’s core added to our crust.

    3) Large moon (and the strike) -> enhanced tidal, volcanic and tectonic activity.

    All of these enhance the -limiting- reagents of life as we know it. Which are not water, carbon, or amino acids. But the heavier and rarer elements. Iron & copper for oxygen transport in different types of blood for instance. Catalysts are pretty central in a laundry list of ‘crucial’ organic chemistry reactions.

    1. Regarding the probability of a large moon, see http://arxiv.org/abs/1105.4616 for one view.

      Excerpt from the abstract: We find that giant impacts with the required energy and orbital parameters for producing a binary planetary system do occur with more than 1 in 12 terrestrial planets hosting a massive moon, with a low-end estimate of 1 in 45 and a high-end estimate of 1 in 4.

    2. Indeed. Additionally, ours is only a third generation star. In the set of integers from 1 to infinity, that’s a rather low number…

      1. I think you are probably correct to assert that 3 is less than infinity, although I welcome corrections on that and what follows. On the other hand,

        1) Many models of the future of the universe (Big Freeze, Big Crunch, Big Rip, etc) do not predict an infinite number of generations.

        2) In expanding universe models (the most popular kind) the rate of star formation falls off dramatically even if it never quite ceases for a long time.

        3) The majority of third and fourth generation stars in existence are red dwarfs, and while the expected lifetime of our sun is only 10 billion years, the expected lifetime of red dwarfs is around 10 trillion years. The potential habitability of red dwarf systems is discussed constantly, but just now, prospects look pretty good.

        But from the point of view of SETI, I think it is more worthwhile to consider the absolute number of Population 1 stars close enough that we can imagine noticing some indication of intelligence from their vicinity – and as long as we are only contemplating one way communication, that’s a pretty enormous number.

  5. Interesting article, but he starts off with a false assumption, that space settlement will be the function of and managed by government. It won’t and this assumption basically renders the article of little value.

    The majority of major human migrations, including the Polynesian and the European settlement of the New World were driven by economics and individual decision making. Government mostly provides a favorable political environment and a bit of funding for initial exploration, as with the Christopher Columbus, but its not a necessary condition and the actual settlement itself is driven by entrepreneurs and adventurers. And the numbers of individuals involved were never in these migrations are never very large, usually a few percentage points of the source population, with the new pioneer populations increasing mainly by an increased birth and survival rate.

    And as a side note, this is similar to how territory expansion occurs in other vertebrate species. While the majority try to fight it out over finite resources a few just leave and expand the range, either by being pushed out or by accident during the dispersal period proceeding reaching adulthood.

    Its also why its a waste of time for space settlement advocates to keep so focused on the NASA budget. The only value I see NASA providing is marginally in the form of information/technology spinoffs from NASA planetary science missions. Beyond this NASA could disappear tomorrow without impacting space settlement.

  6. I doubt the entire universe will be explored within the next 20 generations. Space is a lot bigger than the author believes.

    After more than 20 generations, Europeans continue to come to America — sometimes permanently, sometimes only to visit.

  7. I’d think just building a large, self-sustaining, internally powered space colony capable of operations in the outer solar system would get you most of the way there. By that point our space-based telescopes would be huge and we’d be able to gather quite a lot of data on other viable solar systems. It’s part of our nature to want to go somewhere else, and gathering up several thousand like-minded individuals to embark on a generational journey shouldn’t prove too difficult, especially if the only significant change to their lifestyle is slower e-mail delivery.

  8. Al – You are committing a common fallacy about the requirements for life. Life evolved to use mid-to-heavy elements because they were available; although I don’t know whether any work has been done, I suspect very strongly that the sort of catalysis carried out by enzymes with things like copper and zinc in them could have been carried out otherwise.

    Similarly, although water is a good solvent for life-bearing purposes it is far from being the only one; as an example, liquid anhydrous ammonia (boiling at around -15 C IIRC) is an excellent polar solvent often used as such in various chemical manipulations carried out by chemists in labs.

    We don’t even know that it isn’t possible to use even more exotic liquids such as liquid methane (available in large amounts on Titan, for example) as a solvent for life processes. We are of course biased because most chemists are water-based and doing chemical experiments in liquid methane is difficult and dangerous.

    Hypothetical Titanian exobiologist to another one: “Ridiculous. How could there be life on the third planet, never mind intelligent life? They’d have to breathe poison gas and drink molten lava!” (Titanian volcanoes emit water, and oxygen is extremely destructive to most organic chemicals.)

    1. I have considered that Fletcher, I just don’t buy it. In primordial astrophysics, “heavier elements” means “everything other than hydrogen and sometimes helium.” I really can’t envision either hydrogen- or helium-based life given the chemistry we have explored from about 3K up past the dissolution temperature of hydrogen.

      Thus, first generation stars have exactly squat to work with.
      Second generation stars have more – but even there the ratio of ‘heavier elements’ to hydrogen is pathetic. I don’t doubt that something could arise – but I see it as more likely when you’ve got more of the rarest elements.

      This is a direct combinatorial explosion problem: When you’ve -only- got H, He and perhaps a miniscule amount of Li, the number of vaguely stable compounds or plausible two- or three-body collisions is obviously finite – and just as obviously pathetic. When you’ve finally got (say) beryllium, you’re better off when you can measure it in parts-per-million instead of parts-per-trillion.

      Work has indeed been done on what you might call ‘astrochemisty’. That is, exhaustively exploring plausible gas-phase reactions. Gas phase chemistry is much simpler than anything involving catalysis, and the verdict has pretty much been “No, we don’t get past the simplest molecules without dust/rock surfaces and the resulting more complex chemistry.” Methane, O2, NH4 – yes. Amino acids no. Er, “Hell no” is probably more accurate.

      I’ll freely grant that there are “other choices” for life. There have been “other choices” for key components -here-. There’s the lobster-blood (Cu-based) versus mammal-blood (Fe-based) for one. There’s the existence of the red-leafed plants. And the chemosynthetic life, etc.

      But in chemistry and chemical engineering, everything revolves around the concentration of the least concentrated reagent or the availability of sufficient catalyst. No one cares how much solvent you’ve got really.

      You’re talking about ‘methane-based life’ or ‘ammonia-based life’ or whatever. I’m not discounting that possibility. I’m just saying that -chemically- the plausibility of both of those – as well as any others – would be dominated by availability of trace elements not the more plentiful compounds that the lifeform is “based on”.

      So what I’m postulating is that the possibility of life is directly tied to how much ‘supernova stuff’ is floating around in your solar system. And we’re anomalous in that regard. Yes, later generation stars with high Fe/H ratios are around. But later generation stars where their solar system has had ~5 billion years to develop to ‘life’ are not. At least, they’re much more dispersed than the stock Drake Equation discussions account for.

      1. Al,

        Do you have a cite? Thanks!

        You mention the “local group” as being ahead of the rest of the Milky Way, but I’m not sure what you are referring to here. Stars move — Alpha Centauri is thought to have once have been on the other side of the galaxy from the sun, if I recall correctly. (And Alpha Centauri is thought to be much older than our sun too.)

        2. I wonder if you’re just getting at the same notion expressed with this map:
          http://en.wikipedia.org/wiki/File:Starpop.svg
          and you’re arguing that we’ll be most likely to find intelligent life near intermediate population I stars like our sun In which case, the sun doesn’t seem like a particularly atypical case, and it has plenty of company fitting its description.

          Here’s a paper (from 2001 – perhaps out of date) that suggests most earth-like metal-rich planets are older than the Earth:

          http://www.mso.anu.edu.au/~charley/papers/Icarus.pdf

          Here I quantify these effects and obtain the probability, as a function of metallicity, for a stellar system to harbor an Earth-like planet. I combine this probability with current estimates of the star formation rate and of the gradual buildup of metals in the Universe to obtain an estimate of the age distribution of Earth-like planets in the Universe. The analysis done here indicates that three-quarters of the Earth-like planets in the Universe are older than the Earth and that their average age is 1.8 ± 0.9 billion years older than the Earth. If life forms readily on Earth-like planets—as suggested by the rapid appear- ance of life on Earth—this analysis gives us an age distribution for life on such planets and a rare clue about how we compare to other life which may inhabit the Universe.

          Sorry for the multiple posts, but you’ve intrigued me. Any direction toward further reading would be greatly appreciated.

          1. The key citation for “sun & nearby Fe/H” would be from a graduate-level class in the ’90s which was taught without a textbook. The plot had several hundred stars on it, I can easily believe it’s been superseded as well.

            The wiki article ‘Rare Earth Hypothesis’ has links covering most of the other points I made, though I don’t completely agree with the whole article. The lunar strike hypothesis does seem crucial to me.

          2. Ok. Thanks for the reply!

            I read “Rare Earth”, (the book). It is a great read, but of course, its conclusions have been widely disputed. However, note that even Ward and Brownlee (the book’s authors) come to the conclusion that single cell life is exceedingly common in the universe, and it is only complex multicellular lifethat might be rare. Debate about the liklihood of multicellular life (and intelligent life) is outside the confines of this conversation so far — you were making an argument for why the sun might be relatively rare in terms of its suitability for life.

            I think the key objection to your argument is the same one that SF writers frequently forget: stars move . The sun’s current neighbors aren’t its past or future neighbors. Stars here in the galactic disk might be different from halo stars or galactic bulge stars, but there are billions and billions of stars out here that are pretty much like the sun, the same age or older than the sun, with the same or higher metalicity as the sun, with a similarly circular orbit around the galactic center, well distributed around our entire galaxy more or less like the map I posted above.

            It is a great topic – thanks for the interesting comments! Happy New Year!

  9. I rather think the Fermi “paradox” is more a manifestation of the fact that we can’t detect a civilization’s random broadcasts from much further away than a hundred light years, and there just aren’t that many potentially habitable planets within that radius.

    At the rate we’re going, I think it’s more likely that space travel will be forgotten within 20 generations.

    1. Re: the Fermi paradox:
      30 years ago our broadcasts were near all made in fairly narrow band analog techniques that were easily identified as artificial. Today an increasing portion of radio traffic is digital and spread spectrum modulation that looks a lot like noise to anyone not familiar with the technique.

    2. We can’t detect the 20W signals from our own Pioneer spacecraft beyond a certain point. It is a simple calculation to figure out how far away a multi-gigawatt signal would be detectable, and it’s not that far…

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