18 January 2013

Are we living in a Young Universe? Some further thoughts on the Fermi Paradox

[Updated]. This post is a follow up to a post I put on here almost three years ago to the day. Here

What if the answer to the Fermi Paradox is simply that, contrary to what we like to think, the Universe is yet young, and no (or very few) Elder Races have yet appeared? 

Here is a (perhaps) plausible scenario. Items noted with ♠ are, to my understanding, "generally accepted as true," although perhaps not widely known. 

♠ The Sun is more than one third the age of the Universe, and is significantly (not to say greatly) anomalous, in the direction of having a higher proportion of elements beyond Helium in the Periodic table (higher metallicity) than is typical for stars of its age. (Some stars older than the Sun have even higher metallicities, such as Alpha Centauri (7 b.y. old, somewhat higher metallicity), but we're talking averages here). Typical 5 billion year old stars in the Galactic Disk formed from the moderately enriched Galactic medium of the time, and are consequently less metal rich than typical stars forming today. (It's also true that star formation has tapered well off, but it may be that of all the life bearing worlds that ever form, a high proportion will be from the later-formed stars, for this reason, and the point below). (How stars form plays a role here; there are at least hints that the Sun formed in a cluster where a chain reaction of supernovas had enriched the medium; this is not unusual, and was probably more common in the past than now, but is not typical). 

♠ Metallicity is thought to be positively correlated with the likelihood of the evolution of life; in the sense that planets forming in systems where the protostellar neblua was initially metal-poor, (the ubiquitous and only gradually diminishing condition of the general population of Stars in the early universe), would not yield the materials necessary to form rocky watery worlds like Earth and the marvelously complex chemical/energetic systems we refer to as "life."

♠  [New from original version of this post] It's perhaps worth noting that when these facts are generalized, i.e., we are talking about "stars of the Galactic Disk" as opposed to "the Sun," the basic facts will apply, more or less, with no great degree of variation, to all spiral galaxies everywhere in the Universe, since they're all more or less similarly formed, and all are roughly the same age, having resulted from an evolutionary process instigated by the Big Bang itself. Other types of galaxies may not have sunlike stars at all, for reasons I won't go into here, but there are such a vast number of galaxies essentially similar to the Milky Way in the wider universe that it really doesn't make any difference for purposes of this discussion. Also, the fact that the Milky Way is a "barred spiral" as opposed to other types of spiral galaxies doesn't appear to make any difference; the populations of disk stars in all galaxies with dust-containing disk regions are all essentially similar. Moreover, it's an accepted principle that all parts of the universe are much like all other parts, so it's generally accepted as true that this will be the case everywhere in the universe, even in regions beyond the "time horizon," i.e., beyond the border of where the universe is theoretically observable (the horizon's distance in light years equal to the age of the universe in years; adjusted for recessional velocities from the expansion of the universe itself. Most of the universe is beyond this horizon). 

From these generally recognized facts, let's posit this: the Earth is a pioneer among worlds. Having formed in an unusually metal rich system, in a typical spiral galaxy at an early age, its complex biosphere is likely to be more typical of those found in star systems that formed later (which will only later come to resemble ours), or which are yet to form, than those that began the process of evolution at approximately the same time as the Solar System. 

Now, of course, in the vastness of all of space, this same "pioneer world" phenomenon has probably occurred innumerable times (and sometimes much earlier than here, no doubt), but let's just posit that it is an explanation for something we might begin to suspect, which is that advanced living worlds are currently rather, or possibly even extremely, rare. This says nothing about their likely future prevalence, which, by this reasoning, could be very much greater than it is now. 

Now, another posit: the evolution of intelligent life on Earth took 5 billion years or so from the origin of the Solar System. Maybe this is typical. Maybe it's an extra-long time. But, from information available to us, we don't know: maybe, on other hand, it's remarkably fortuitous, and atypically efficient and quick. Maybe life sometimes or even usually goes its merry way and does not evolve into beings that use thought as a competitive adaptation to ensure their survival; or that, on average, such evolution usuallytakes longer than it did on Earth. These are not known; we have no real way to evaluate any of these possibilities. Remember that it took complex (i.e., multicellular) life over 4 billion years to emerge on Earth, and it took a further 550 million years before technologically adept creatures (us) evolved (please don't plead for the Whales and Dolphins... they may be smarter than us but they're not building spaceships or intergalactic radios anytime soon). So most of the history of Earth, which, again, is over 1/3 the entire history of the universe, saw life but no "intelligence." So the latter is not necessarily implied, at all, by the former. (Stephen Jay Gould, in reasoning that I found unconvincing, hypothesized in his book Wonderful Life that if you could "play the tape" of evolution over again, given the same starting conditions, it was spectacularly unlikely that intelligent beings would evolve again. I thought, and still think, his rationale was hopelessly parochial, and failed to take into account the power of convergence. Nonetheless, the fact that for hundreds of millions of years there was no intelligent life surely indicates that the chances of its evolution are not 100%). 

So, here's what I think may be happening. Supercivilizations are possible. They may already exist, in some corners of the Vast Universe (although probably not real near here, since we see no signs of their amazingly stupefying technology, which we would, presumably, if they were mucking about on our doorstep). We may evolve into one of these, ourselves, eventually. What that will look like, we can hardly guess. But the Young Universe has yet to produce Supercivilized Elder Races in abundance. Most living worlds, even those which have chanced to evolve intelligent beings, are, in fact, isolates, like ours. 

Someday, that may all change, as the universe matures. 

But in the meantime, this is why, at least for now, we appear to be, and effectively are, "alone."