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Something that annoys me is when they say life must be common in the universe, because it happened on Earth so quickly. The Earth is four and a half billion years old, they remind us, and the bacteria that would later be fossilized as stromatolites were there by its 300 millionth birthday. Relatively speaking, that's pretty darn fast! Why, as soon as the conditions are right for life, up it pops!
That is head-shakingly stupid. Abiogenesis, assuming it happened and happened here, is a chemical process. Chemical processes happen on millisecond and finer time scales. 300 million, 3 million years - they make no more difference to the chemistry than 3 minutes would.
When life arose, it arose quickly or slowly in relation to the conditions around it, at that time. All the time that has passed since then, and all the time that will ever pass forever, does not change any event in the past. Not the least little bit. The past happened, and events were quick or slow then. It's absurd to think anything, even the passage of time, can ever change any aspect of what has happened.
So the notion that life must be everywhere because it happened once is equally absurd. I suppose it does have the attraction of aging well, however. Any thing we can attribute to the length of time since life's appearance in the dim past will be even more remarkable tomorrow.
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Discussion (47)
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It is not science. It is speculation. Mind you, it could be easily proven or disproven by getting out to other planets and stellar systems.
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If I understand your argument correctly, then I'm in agreement with you in one particular but generally not on the overall point you're making. If it looks like I misunderstand you, please let me know.
The point on which I agree is this: based on our current knowledge, and despite the view many embrace, there is no sound statistical basis for the argument that "life must be common in the universe."
I don't agree that stupidity is required to think otherwise. If we assume that life is the product of a naturally occurring chemical event, then it follows that there is some probability (let's call it p) that such an event will occur again given similar initial conditions.
It's natural that one would look upon the vastness of the universe in both space and time and conclude that, however unlikely was abiogenesis, surely it must have happened more than once. One needn't be stupid for thinking that, given that, since there are very few meaningful numbers as large as the probable number of chemical reactions in the universe in any given billion years (let's call it r), then surely the probability that life occurred elsewhere must be very high.
But that probability, 1 - (1 - p)^r, is close to one only if p is not very small compared to 1/r. In other words, however large the number of opportunities, if the probability in any single instance is sufficiently minute, then the likelihood of a repeat occurrence remains small.
We can make some wild estimates of the number of opportunities for chemical encounters in the visible universe. Unfortunately, we're on more shaky ground even than that when it comes to guessing how probable abiogenesis was the first time. All we know is that it happened once, and that gives us no basis for an estimate of probability.
That's counter-intuitive even to people who understand large numbers.
If we thought that the universe would go on forever, that it had some kind of steady state quality, then we could reasonably assert that life will recur: however small p gets, (1-p) raised to infinity is going to approach zero, and so the probability of life will approach unity.
But there's little reason to believe that the universe -- the bit we can see, at any rate -- will remain entropically interesting forever. We expect heat death, and with it a practical limit to r.
And so we have no basis for optimism or pessimism regarding life in the universe, and won't have until we learn more.
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I think you get it. My point is that it is stupid to think that abiogenesis is common because it happened a very long time ago, and that the longer ago it happened the more likely it is to have happened elsewhere.
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We have a lot of excellent engineers today working with not so excellent scientists.
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Yes, I agree that that is a mistaken perspective. I just think it's an intuitively natural perspective, in that it's natural for very large sample spaces to make the probability of any possible outcome to seem likely. It's simply an unfounded assumption when the probability is truly unknown and the sample space is finite.
Of course, if it had happened twice a long time ago, it would be reasonable to suspect that it has probably happened many times since then (all other things being roughly equal).
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