Exobiology was the original term given to the sciences central to the question of life-in-the-Universe. It’s now been largely replaced by Astrobiology, but I’ll stick with the original. To investigate life-in-the-Universe one need start at the beginning – if there was one – which is the origin and evolution of our Universe. The universal laws and constants of physics are life-friendly (however you care to define life); the universe is however indifferent to whatever life-forms it produces and their ultimate fate.
‘In the beginning’ is a most unsatisfactory phrase as it explains nothing, and ultimately leads to the type of philosophical question ‘if God created the Universe, what being in turn, created God?’ You have to have the concept of infinity-in-time to get around that knotty problem. It’s far easier to come to terms with ‘it has always been and it always will be’ relative to ‘in the beginning’. There as no ‘in the beginning’.
How can you have a Universe (ours) that has always existed when clearly there is observational evidence what our Universe had a beginning – the Big Bang Event – some 13.7 billions years ago? Well, I believe that there are ultimately endless cycles of Big Bangs, expansions, contractions, hence Big Crunches (a contracting universe that comes together at a single point in space and time), before it starts all over again. In other words, I suggest a cyclic or oscillating, finite but unbounded, universe, existing again, and again, within infinite time. By the way, I can’t claim originality for that. And, the laws and constants and relationships of physics will be the same each time for each cycle (otherwise you might get a universe which never contracts again), or, in other words, each cycle will be life-friendly, because this Universe is bio-friendly (in that life can arise and exist in it).
Unfortunately, current observational evidence strongly suggests that our expanding Universe will not slow down, stop, and reverse direction. Even if that observational evidence isn’t contradicted by other more finely tuned observational evidence further on down the track, that doesn’t quite put the kibosh on the Big Crunch.
If the cosmos is infinite in time, it’s also probably infinite in volume. In other words, there’s ample room for more than one universe. If two (or more) expanding universes start to intersect, the stuff of any one universe, diluting with the expansion, now meets stuff from another universe(s) and the density of stuff starts to increase. Gravity does the rest and the intersecting parts of two or more expanding universes now clump together, start contracting, ultimately coming together at one point in time and space (a Big Crunch), the pure momentum resulting in, of course, a Big Bang and the ‘creation’ of a new universe.
Even if my postulated cyclic/oscillating Universe isn’t to be, it doesn’t alter the fact that this Universe, our Universe, and the various physics that are part and parcel of it, permit life to exist in it. Why that should be so has been the subject of much speculation and debate. There probably was no particular reason (‘First Cause’) behind it all. It was just the way the Universe dealt the cards at the very beginning of the game. In any event, were that not the case, were some sort of non-life producing physics cards dealt instead, we wouldn’t be here to have to worry about such a heady question – why things are the way that they are.
However, the idea that there are many universes solves the improbability that our Universe just lucked out against all probability as being a bio-friendly one. If thousands of universes have and do exist, by chance some will be bio-friendly, even if most are not.
Since we can only exist in one of those few bio-friendly ones, well it’s now obvious why our Universe has life in it- terrestrial life at least. However, if our Universe can give rise to life without there being some sort of predetermined life-plan purpose to the Universe, then equally the Universe will go on its merry way without concern if we should all go down the gurgler.
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