Good Math/Bad Math

Monday, May 22, 2006

Probability and Fine Tuning

The ways that creationists play with "big numbers" games never ceases to amaze me. Over the weekend, I came across yet another extremely silly attempt to show that life on earth is so improbable that it must be the result of divine intervention.

The reason that I'm mentioning this one is that it's a different approach to generating the big number. Instead of sticking with the usual argument about the supposed probability of abiogenesis on earth, it tries to use a probabilistic version of the fine-tuning argument: that there are specific properties of the universe as a whole, and of the earth in particular, that make life possible, and that the likelihood of all of those properties having the correct values is so unlikely that they must be the result of deliberate divine intervention to make life on earth possible.

This bugger is just chock-full of problems. The most important one is what I call the fake numbers error: most of the numbers are just made up. For example, they cite the "local abundance and distribution of dark matter" as a property that must have a specific value, and state that the probability that this will fall within the range required for life as "0.1". At present, we don't know precisely what dark matter is, what properties it has (beyond the fact that it has a gravitational influence on bright matter), or how it's distributed. So claiming that it's distribution is a required property of the universe for life is silly, and assigning a meaningful specific probability number for that distribution matching the current unknown value is impossible. Many of their "parameters" for life are like this: they're just numbers pulled at random out of a hat. They've got 322 factors: my estimate is that at least 90% of those are fabricated. What's worse is that many of those aren't just made up numbers; they're utterly silly as parameters for life. I mean, "infall of buckminsterfullerenes from interplanetary and interstellar space upon surface of planet"?

They also make liberal use of the false independence problem. This is where you take two related factors, but treat them as if they were unrelated, in order to inflate your probabilities. A trivial example of this kind of problem is: what's the probability of flipping a coin twice, and getting heads both times? 1/4. What's the probability of flipping a coin three times, and getting heads all three times? 1/8. Good so far. Now, suppose that I've already flipped a coin twice, and gotten heads both times. What's the probability that I'm going to get 4 heads in a row? A false independence would say: 1/16th - because it ignores the fact that flipping heads twice affects the probability of flipping heads four times in a row: I'm already halfway there.

Examples of this from their list: they take "relative abundances of different exotic mass particles", and "decay rates of different exotic mass particles" as independent factors. They're not independent: the abundances of the exotic particles and their decay rates are both dependent on the properties of the universe that allow those particles to exist. Or even more obvious: "proximity to supernova", "timing of supernova", and "supernova rates and timing" as three different parameters. They play this game over and over again, creating lists of factors to inflate their improbabilities, even those those factors are not independent.

What's particularly humorous is the number of times that they include "parameters" for the probability of life on earth that are based on the existence of life on earth! By my count, they have at least 18 factors that explicitly depend on the existence of life on earth in order to argue that life on earth is improbable! (9 parameters specify quanities of certain kinds of bacteria, 1 specifying quantity of fungi, one specifying quantity and timing of vascular plants, 1 specifying quantity and timing of carbonate producing animals, etc.) In all, they argue that the existence of life on earth is responsible for a probability factor of "1/10^42" against the existence of life on earth! Yeah, the existence of life on earth sure does make for a strong case that life on earth is unlikely!

They also mix in a bunch of earth-specific factors ("position and mass of Jupiter relative to earth", "amount of outward migration of Neptune", etc.); but they claim to be computing the probability of life existing around any potential life-supporting body in the universe. Yep, the odds of any other earth-like planet having Jupiter as a neighbor is pretty unlikely all right!

They go on, and on, and on like this - with barely a single valid number in the entire exercise, to conclude:

Thus, less than 1 chance in 10^282(million trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion) exists that even one such life-support body would occur anywhere in the universe without invoking divine miracles.


  • i'm not very familiar with the fine points of statistics, but it seems to me that there is only one answer to the question of the probability of life on earth: 100%. So far, in every Universe we know of, on every Earth we know of, life has occured 100% of the time.

    Real scientists should get their own back by calculating how small the probability is that God created earth, taking into consideration every other thing he could possibly have chosen to do with his day, including making up all the things we can't think of because we aren't gods.

    Oh, well, except they're all busy doing real science, not making stuff up.

    By Blogger moonflake, at 10:54 AM  

  • The fake number error: AKA occult statistics.

    Of course, there's a heaping helping of Texas Sharpshooter involved in this case, since the "goal" is life in the universe, not life specifically like ours on this particular rock under very specific circumstances.

    I guess all the dice I've rolled, coins I flipped, and cards I've drawn where divinely caused, since it's so unlikely they'd come up in the sequence they did.

    By Blogger Bronze Dog, at 1:26 PM  

  • LOL – I see you have been reading Hugh Ross’ made-up statistics that I wrote about here. Glad to see your arguments (with much greater actual understanding of the math) were similar to mine.

    By Anonymous Skeptico, at 3:19 PM  

  • According to their numbers, any planet that has not *exactly* the same quantity of
    "nickel quantity in crust"
    than Earth has only 90% less chance of evolving Life.

    Same for all parameters. Their 10% number is pulled out of a hat.

    By Anonymous _Arthur, at 3:54 PM  

  • You know, that wouldn't look so damn big if they used quintillions instead of those little trillions. Heh. :D

    How many creationists do you think you could confuse if you said that site "proved" the probability was

    "one in a googol, googol, googol, divided by a quintillion"

    Or isn't a septillion equal to 10^24? You could simply say

    "one in a googol, googol, septillion, septillion, septillion, ten thousand"

    It would almost be worth trying just for the hell of it.

    By Blogger sailorman, at 7:29 PM  

  • If you have ANY of the beliefs shown below then there are some very interesting results.

    Belief #1) Our universe has been around forever.
    Belief #2) Our universe has gone through an infinite number of big bang, expansion, contraction, big bang cycles.
    Belief #3) There are an infinite number of universes (common belief among many scientists)

    If you have any of the above beliefs then it is INEVITIBLE that intelligent life WILL come about on its own WITHOUT a creator.

    It simply DOES NOT MATTER in the slightest what odds you assign to the likelihood or unlikelihood of intelligent life coming about.

    If you have an infinite number of chances, then there will be, in fact, an INFINITE number of times that life has come about on its own.

    Similarly, if there are an infinite number of universes, then there will be INFINITELY many universes teeming with life and there will also be INFINITELY many universes totally devoid of life. There will also be infinitely many universes with only one instance of life, etc., etc.

    I don't care if you say the odds of life are 1 out of 10 to 400th power or 1 out of 10 to the trillion times a trillion power, there will STILL be an infinite number of times that life came about by itself.

    Many religious people calculate the odds against life coming about by itself are something like 1 in 10 to the 400th power or something like that. For a single, finite lived universe, that would pretty much guarantee life could not possibly come about on its own.
    However, if yoo have one of the above 3 beliefs, those odds are not any obstacle at all!

    By Anonymous Anonymous, at 4:34 AM  

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