"One thing is for sure, we are located on a small planet orbiting around a mid-sized star, in a middling galaxy among millions of other galaxies that have millions of stars in them. It is ridiculous to think that all that universe was placed there merely to provide a decorative backdrop for our night sky. How we fit into all of that is a question worth considering and discussing.
Given the enormity of the universe, it should surprise us more were we not to exist, than to exist. People are astounded by the universe around them and ask why? Why are we here? Why the universe? I say, why not? Given the number of stars, planets, and galaxies, should it surprise us that at least ONE planet in the multitudes of multitudes of planets has life?
The odds of winning the lottery are astronomical, but someone somewhere hits the jackpot every week."
It is popular, especially by those searching for little green men, to speculate about the odds of life on other planets. Such reasoning is usually along the lines of Carl Sagan's "If only one in a million stars has an Earth-like planet, and if only on one in a million of those planet lifes arises, and if only one in a million of those planets produces a technical civilization, there must be a billion technichal civilizations." But such reasoning is a little hazy to say the least because it simply makes a bunch of assumptions about the statistical odds, rather than doing anything to figure out what they actually are.
I will now quote freely from the writings of polymath Marshall T. Savage. (no, I am not making that surname up! Spooky, eh?
) The following method of arriving at a realistic probability of life arising by chance is not merely a wild idea by Savage, nor is Savage a creation science or other fringe type with an ideological axe to grind. The science is accepted as sound. Isaac Asimov I believe crunched the numbers in the same way and made the same conclusion.
[Let us presume that all that is required for the evolution of life is the formation of a single self-replicating DNA chain. (A great deal more than just this chemical accident is of course required to produce single celled organisms, then a complete biosphere, and finally intelligent beings. But for the sake of argument, let's set the chain causality in motion that will eventually evolve you and me out of the mud.) As it turns out, the minimum chain length for self-replicating DNA is around 600 nucleotides. (Nucleotides are the building blocks of DNA, consisting of the base pairs of adenine-thymine or guanine-cytosine that form the rungs and the phosphates which form the backbone of the ladder in the double helix.) Six hundred links is an exceedingly short DNA chain. Consider that a very simple virus contains 170,000 links and a bacterium seven million; Your own DNA chain is six billion links long.
How likely is it that the primordial soup, given enough time, will cook up a strand of "Genesis DNA"? To calculate the odds of such an even occuring at random, we need to turn to "information theory". This is an arcane branch of statistics developed to aid the design of computers and telecommunications networks. Essentially, information-theory reduces the nebulous concept of "information" to exact mathematical quantities relating to message content and length. According to to information theory, a message with meaning can be interpreted as a level of probability. In other words, how likely is it that the message will be generated at random? This probability is dependent on the number of bits required to encode the message. The number of bits is then the exponent (base 2) of the number of random trials it would take to generate that message. In plain English, this means that generating even a relatively short message by trial and error takes an enormous number of tries.
Words, like those you're reading now, contain meaning-at least that's the intent. In theory, the same message content could be generated randomly (perhaps it would make more sense if it was). Using information-theory, we can find out what the odds are of a given message being generated by chance.
Let's use a very simple message, one I'm sure we're all familiar with from our earliest attempts to decode these alphabetic hieroglyphics: "See spot run." This minimal message contains just thirteen elements: ten letters, two spaces, and a punctuation mark. Written English requires only about 50 symbols to convey any message: 26 letters, 10 figures, 13 punctuation marks, and blank spaces. The first position in our message has one chance in fifty of being an "S". The odds of generating a particular message one symbol long are 50 to 1. The second position has the same odds, so the chances of a message two symbols long turning up as "Se" are 50 times 50, or 50 to the 2nd. It is very easy to calculate the odds of any message being generated at random: The number of possible symbols is the base, and the base number is raised one exponential power equal to the number of symbols in the message. The odds of generating "See Spot run." at random are 50 to the 13th. To create this rudimentary message by accident would require six hundred billion trillion trials. If a computer were programmed to generate a 13 character string at random, and created 10 million new strings every second, it would take the computer two billion years to come up with "See Spot run."
Information theory shows why generating a 600 nucleotide chain through random chemistry is-to put it mildly-unlikely. The genetic alphabet is much shorter, containing only four symbols: A-G, G-A, C-T, T-C; But this doesn't help matters very much. The same rules of chance apply. The odds of generating a particular string of nucleotides 600 base pairs long are 4 to the 600th, or 10 to the 360th to one. If these are the odds against the bob-tail nag, you'd better bet on the bay.
To generate a string of Genesis DNA would take 10 to the 360 chemical reactions. This is a completely ridiculous number. Writing such a number is an exercise in futility; it requires hundreds of zeroes. Describing it in words is just about as hopeless; A million billion trillion quadrillion quintilliion sextillion septillion octillion nonillion decillion doesn't even tuch it. The only way to describe it is as ten nonillion nonillion googol googol googol. You can't even talk about such numbers without sounding like your brain has been fused into molten goo. If you persist in thinking about them it certainly will be.
Surely, there must be numbers of equal magnitude available to rescue us from such overwhelming odds. After all, DNA is just a large molecule. So we must be dealing with atomic numbers, and they are always mind boggling-right?
When life arose, the Earth's oceans were, as Carl Sagan suggests, one giant bowl of primordial soup. The number of chemical reactions going on in that stew must have been incredible. Over billions of years, any possible combination of DNA could have been cooked up-couldn't it? Well, let's take a look; the bottom line is always in the numbers.
The oceans of the early Earth contained, at most, 10 to the 44 carbon atoms. This sets the upper limit on the possible number of nucleic acid molecules at 10 to the 43. (Assuming that every atom of carbon in the ocean was locked up in a nucleic acid chain molecule-an unlikely state of affairs.) The oceans would therefore contain no more than about 10 to the 42 nucleotide chains, with an average length of ten base pairs. If all these nucleotides interacted with each other 100 times per second for ten billion years, they would undergo 3 X 10 to the 61 reactions. That would still leave them woefully short of the sample needed to generate a strand of Genesis DNA. To get a self-replicating strand of DNA out of the global ocean, even it was thick with a broth of nucleotides, would take ten billion googol googol googol years. Makes your eyes spin counter-clockwise doesn't it?
But there are billions of stars in the galaxy and billions of galaxies in the universe. Over time, the right combination would come up somewhere-wouldn't it? Assume every star in every galaxy has in the entire universe has an Earth-like planet in orbit around it, and assume every one of those planets is endowed with a global ocean thick with organic gumbo. This would give us 40,000 billion billion oceanic cauldrons in which to brew up the elixir of life. Now we're getting somewhere-aren't we? In such a universe, where conditions for the creation of life are absolutely ideal, it would still take a hundred quadrillion nonillion nonillion googol googol years for the magic strand to appear. Sheesh!]
So, at long last, those are the real odds on life arising folks. Now before any of you say it, I realize that a probability is just that, not a certain predictor. But having a close approximation of the odds of life arising by sheer chance it at least another data point one can consider when you ponder our place in the universe and the possibility of some force in addition to and beyond our own minds.
Edited by: White_Savage