We've written a couple of posts (here and here) about the chances that there is life in space, besides ourselves. We were stimulated to do this by an article in American Scientist that we referred to in those posts. We said we thought a lot of the astronomical musings in that article were reasonable, and interesting, but that the evolutionary discussion was naive. We explained why. But there are some other issues that may or may not have any bearing on the subject, even if they are at least captivating to think about.
Many cosmological arguments say that the universe is effectively infinite, perhaps including other universes through black holes and things of that sort. Now there are several levels or degrees of infinity. The smallest is the number of integers 0,1,2,3..... But between each of those are infinitely many partway numbers 1.00000....1, 1.00000.....2, 1.00000.....3, and so on (the 'real' numbers, that form essentially a continuum). The number pi, relating diameters to circumferences of circles, for example, is 3.141.... to a never ending sequence of digits. Now, if the universe is discrete--made up of particles such as atoms, photons, gravitons, electrons, and so on, its infinity might be of the 'smaller' kind (we don't know what astronomers would say about this). Still, if it's infinite then so long as there is any non-zero probability of something existing in the vastness of space, it must exist. And for the same reason, it must exist infinitely many times.
If one were to say that space is huge but not really infinite, then as we noted in our previous post, to guess at how many other planets had intelligent life on them, we'd have to know the probabilities of every attribute that was essential for (any form of) intelligent life. Whatever these probabilities are, we can estimate from them how likely it is that they occur for a given space rock. Suppose each probability is on the order of 1 in a million and there are 10 such vital criteria. Then the chance of life existing would be 0.000001^10 (a millionth to the 10th power), an exceedingly small number. If there only a finite number of rocks, even if that's a huge number, the tiny probability could mean that life simply is unlikely to exist anywhere.
Of course, space is not uniform so that multiplying such probabilities as if they had the same meaning everywhere and every-when is undoubtedly not accurate, nor do we have more than crude guesses at what even their average values might be. But the idea holds that the chance of life depends on the size of space in some ways. This does not count the chance that we could actually detect that life. Or that our 'intelligence' and theirs would bear enough resemblance that communicating with each other even made sense. Or that we could communicate even if we thought in the same way and wanted to, given the vastness of space relative to the speed of communication (speed of light), or that we'd be contemporary in any relevant way.
So we should recognize as weird and pure Hollywood all this talk about--and investment in--searches for life in space. A waste of money to treat it as if it's serious science, and much cheaper to do with video graphics in a movie studio. And, of course, we can't even think seriously about interacting with the universes that might exist on the other 'side' (so to speak) of the navel of black holes.
In this sense, the infinity game is a misleading or even stupid one to engage in. But, oddly, there is a kind of infinity game that serious scientists do play, about things right here at home. And many, apparently, take seriously the idea that there are infinitely many universes, almost as similar as but also as different from our own, and in any and every way, that one can specify--literally!
This is the conclusion of the Multiverse theory of physical reality. You can Google this subject or find it on Wikipedia to get a sense of the idea. It is based on decades of experiments with photons shone through slits in barriers, onto flat detectors, in which single photons generate wavelike interference patterns in the detectors. If a single photon is a discrete unit, the only way it can generate such patterns is if it is interacting with other particles that behave just like photons but interact with them, but which we don't detect in any other direct way--because our experiment only released one actual photon, not a sea of them.
The idea, incredible or not, is that these shadow photons are members of parallel universes that in this case are almost identical to our own. We release a photon and they're releasing shadow photons at the same time! The wavelike pattern reflects the different interacting universes of which there must be an infinite number since the waves of interference are essentially continuous.
Advocates of the Multiverse theory, who are apparently mainly sane and taken seriously and considered mainstream physicists, argue that probability is itself a misleading concept. That is, if you flip a coin, there are infinitely many coin-flips occurring in the Multiverses, and in half of them the coin will come up Heads. It is this, rather than any true probability, that gives us the notion that things are actually random.
his affects the space-infinity game, because the infinity game in the Multiverse sense says essentially that every possible universe, including others only infinitesimally different from our own, actually exist. We don't (yet?) know how to communicate with them by exchanging telegrams, but physicists studying 'quantum computing' seem to be doing that in some ways (that we don't understand).
If the Multiverse view is correct, searches for life way out there in space are a bit off the mark (even if it exists), because there are an infinity of universes running directly parallel with our own, right here and now, and close at hand.
In that sense, evolution is not a random process at all. Instead, probabilities such as of mutation, gene transmission, or survival in competition, are illusionary: these things that seem probabilistic are instead what happened in our own fully deterministic universe, out of the infinite distribution of what could happen--and did happen in the infinity of other also fully deterministic universes running along parallel with ours. If Mendelian segregation says (in our benighted understanding) that there is a 50% chance an Aa parent will give a child her A variant, what's really happening is that the transmission of A (or a) is fully deterministic in each universe, but A-transmission happens in half of them. Weird to think about!
Rather than being Alone in the Universe (the title of the article that triggered these thoughts), the Multiverse is infinitely crowded, not just with other life, but with other our-life, too--you're reading a nearly identical blog in those universes, or maybe in some you're not, or in some you already died, or in some of them this word was omitted or mis-spelled, etc.
We, not being astronomers or cosmologists, surely have many concepts and details wrong, and surely this doesn't matter to what we do as evolutionary biologists here on our own Earth. If we could get in touch with them--with their us--what would we do or say? Would that contact itself cause some or all of the universes to change or self destruct? It is interesting to think about anyway, because if it's true, we should feel far less lonely-even if we're not able to contact the other life that exists in the infiintely many versions of our particular universe!