The odds of life existing on another planet grow ever longer, argues this piece in the WSJ
Here’s the story: The same year (1966) Time featured the now-famous headline (“Is God Dead?”), the astronomer Carl Sagan announced that there were two important criteria for a planet to support life: The right kind of star, and a planet the right distance from that star. Given the roughly octillion—1 followed by 24 zeros—planets in the universe, there should have been about septillion—1 followed by 21 zeros—planets capable of supporting life.
As our knowledge of the universe increased, it became clear that there were far more factors necessary for life than Sagan supposed. His two parameters grew to 10 and then 20 and then 50, and so the number of potentially life-supporting planets decreased accordingly. The number dropped to a few thousand planets and kept on plummeting.
Even SETI proponents acknowledged the problem. Peter Schenkel wrote in a 2006 piece for Skeptical Inquirer magazine: “In light of new findings and insights, it seems appropriate to put excessive euphoria to rest . . . . We should quietly admit that the early estimates . . . may no longer be tenable.”
As factors continued to be discovered, the number of possible planets hit zero, and kept going. In other words, the odds turned against any planet in the universe supporting life, including this one. Probability said that even we shouldn’t be here.
Today there are more than 200 known parameters necessary for a planet to support life—every single one of which must be perfectly met, or the whole thing falls apart.
But wait, there’s more:
The fine-tuning necessary for life to exist on a planet is nothing compared with the fine-tuning required for the universe to exist at all. For example, astrophysicists now know that the values of the four fundamental forces—gravity, the electromagnetic force, and the “strong” and “weak” nuclear forces—were determined less than one millionth of a second after the big bang. Alter any one value and the universe could not exist. For instance, if the ratio between the nuclear strong force and the electromagnetic force had been off by the tiniest fraction of the tiniest fraction—by even one part in 100,000,000,000,000,000—then no stars could have ever formed at all. Feel free to gulp.
Multiply that single parameter by all the other necessary conditions, and the odds against the universe existing are so heart-stoppingly astronomical that the notion that it all “just happened” defies common sense. It would be like tossing a coin and having it come up heads 10 quintillion times in a row. Really?
Fred Hoyle, the astronomer who coined the term “big bang,” said that his atheism was “greatly shaken” at these developments. He later wrote that “a common-sense interpretation of the facts suggests that a super-intellect has monkeyed with the physics, as well as with chemistry and biology . . . . The numbers one calculates from the facts seem to me so overwhelming as to put this conclusion almost beyond question.”
I think Monty Python nailed it back in ’83:
So remember, when you’re feeling very small and insecure
How amazingly unlikely is your birth
And pray that there’s intelligent life somewhere up in space
‘Cause there’s bugger none down here on Earth