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Author Topic:   Should We Focus on the Earth Alone?
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Message 1 of 3 (68409)
11-21-2003 4:44 PM

CAVEAT: I did come up with this argument on my own, but I have a strong feeling that someone else has stated it before (on or off site). Nonetheless, I thought it would be a good topic.

I have seen numerous calculations on the odds of life arising due to abiogenesis (chemicals to life). Theses calc's use ocean volumes, land mass, intertidal zones, hydrothermal vents, etc. to calculate odds of this or that. However, should we be focusing on the odds of life occuring on Earth and ignoring the greater question of can life occur in the Universe.

DNAunion posted that for life to arise in an RNA world the amount of RNA needed might equal the mass of the Earth. Whether or not this is correct is not what I am arguing. However, what if there was enough RNA naturally occuring in the Universe to equal the mass of the Earth. Then, according to the theory, life could occur in the Universe somewhere. So, are we actually painting the bulls-eye around the arrow when we devise theories that only take into account the conditions here on Earth?

For analogy only, if we give each planet a lottery ticket with the odds of winning 1 in 50 million and we gave out 50 million tickets, we would expect one of those planets to win. Still, the chances of winning for each planet is still 1 in 50 million. Now, one in 50 million is not that great a number when looking across the vast amount of galaxies in the universe, this might equate to one ticket per galaxy.

So, to say that the chances of life arising on Earth through abiogenesis (chemicals to life) may not be as great if we look at the bigger picture. It might equate better to "what were the chances of me being born in (insert home town)". The chances of you being born where you were to whom you were are 1 in 1, it occurred.

Well, just something I had to post and it really didn't fit anywhere else. Feel free to rip into it, I'm not that attached to this argument.

Replies to this message:
 Message 2 by DNAunion, posted 11-21-2003 6:49 PM Loudmouth has not yet responded
 Message 3 by DNAunion, posted 11-21-2003 7:18 PM Loudmouth has not yet responded

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Message 2 of 3 (68434)
11-21-2003 6:49 PM
Reply to: Message 1 by Loudmouth
11-21-2003 4:44 PM

Richard Dawkins has made that point, I believe in his book "The Blind Watchmaker" (I no longer have my copy, so I can't check). IIRC, he said that we can allow ourselves the luxury of relying on a large degree of luck for our attempts to explain the origin of life, as long as the luck can be paid for the potential number of planets. Roughly speaking, if there are potentially 10^20 planets, then we can consider each one an entry into an OOL lottery.
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 Message 1 by Loudmouth, posted 11-21-2003 4:44 PM Loudmouth has not yet responded

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Message 3 of 3 (68440)
11-21-2003 7:18 PM
Reply to: Message 1 by Loudmouth
11-21-2003 4:44 PM

I remembered enough key words to do a Google search and came across a lengthy quote. If any sees any problems with this quote - words/sentences omitted without ellipses being used, changing of words, etc. - please point them out.

“We can accept a certain amount of luck in our explanations, but not too much. The question is, how much? The immensity of geological time entitles us to postulate more improbable coincidences than a court of law would allow but, even so, there are limits. Cumulative selection is the key to all our modern explanations of life. It strings a series of acceptably lucky events [random mutations] together in a nonrandom sequence so that, at the end of the sequence, the finished product carries the illusion of being very very lucky indeed, far too improbable to have come about by chance alone, even given a timespan millions of times longer than the age of the universe so far. Cumulative selection is the key but it had to get started, and we cannot escape the need to postulate a single-step chance event in the origin of cumulative selection itself....
The more we can get away from miracles, major improbabilities, fantastic coincidences, large chance events, and the more thoroughly we can break large chance events up into a cumulative series of small chance events, the more satisfying to rational minds our explanations will be. But in this chapter we are asking how improbable, how miraculous, a single event we are allowed to postulate. What is the largest single event of sheer naked coincidence, sheer unadulterated miraculous luck, that we are allowed to get away with in our theories, and still say that we have a satisfactory explanation of life?
So, there are some levels of sheer luck, not only too great for puny human imaginations, but too great to be allowed in our hard-headed calculations about the origin of life. But, to repeat the question, how great a level of luck, how much of a miracle, are we allowed to postulate?...The answer to our question - of how much luck we are allowed to postulate - depends upon whether our planet is the only one that has life, or whether life abounds all around the universe. ... There are probably at least 10^20 (i.e. 100 billion billion) roughly suitable planets in the universe.
It is entirely possible that our backwater of a planet is literally the only one that has ever borne life. ... If the origin of life is such an improbable event that it happened on only one planet in the universe, then our planet has to be that planet.
Our question was, how much luck are we allowed to assume in a theory of the origin of life on Earth? ... Begin by giving a name to the probability, however low it is, that life will originate on any randomly designated planet of some particular type. Call this number the spontaneous generation probability or SGP. It is the SGP that we shall arrive at if we sit down with our chemistry textbooks, or strike sparks through plausible mixtures of atmospheric gases in our laboratory, and calculate the odds of replicating molecules springing spontaneously into existence in a typical planetary atmosphere. Suppose that our best guess of the SGP is some very very small number, say one in a billion....if we assume, as we are perfectly entitled to do for the sake of argument, that life has originated only once in the universe, it follows that we are allowed to postulate a very large amount of luck in a theory, because there are so many planets in the universe where life could have originated. If, as one estimate has it, there are 100 billion billion planets, this is 100 billion times greater than even the very low SGP that we postulated. To conclude this argument, the maximum amount of luck that we are allowed to assume, before we reject a particular theory of the origin of life, has odds of one in N, where N is the number of suitable planets in the universe. There is a lot hidden in that word 'suitable', but let us put an upper limit of 1 in 100 billion billion for the maximum amount of luck that this argument entitles us to assume
We go to a chemist and say, .fill your head with formulae, and your flasks with methane and ammonia and hydrogen and carbon dioxide and all the other gases that a primeval nonliving planet can be expected to have; cook them all up together; pass strokes of lightning through your simulated atmospheres, and strokes of inspiration through your brain; bring all your clever chemist's methods to bear, and give us your best chemist's estimate of the probability that a typical planet will spontaneously generate a self-replicating molecule. Or, to put it another way, how long would we have to wait before random chemical events on the planet, random thermal jostling of atoms and molecules, resulted in a self- replicating molecule?...we'd have to wait a long time by the standards of a human lifetime, but perhaps not all that long by the standards of cosmological time....even if the chemist said that we'd have to wait for a 'miracle', have to wait a billion billion years - far longer than the universe has existed, we can still accept this verdict with equanimity. There are probably more than a billion billion available planets in the universe. If each of them lasts as long as Earth, that gives us about a billion billion billion planet-years to play with. That will do nicely! A miracle is translated into practical politics by a multiplication sum." (Richard Dawkins, The Blind Watchmaker, Penguin, 1991, p139-145)

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