Paul Davies 'falou e disse': afirmar que o universo está pululando de biologia é afirmar sem evidência

quinta-feira, maio 26, 2016

Maybe Life in the Cosmos Is Rare After All

The conclusion that the universe is teeming with biology is based on an unproved assumption

By Paul Davies on May 23, 2016

A planet like Kepler 22b could plausibly be habitable—but that doesn't mean it's inhabited Credit: Artists' rendering by NASA/Ames/JPL-Caltech. Public Domain

When I was a student in the 1960s almost all scientists believed we are alone in the universe. The search for intelligent life beyond Earth was ridiculed; one might as well have professed an interest in looking for fairies. The focus of skepticism concerned the origin of life, which was widely assumed to have been a chemical fluke of such incredibly low probability it would never have happened twice. “The origin of life appears at the moment to be almost a miracle,” was the way Francis Crick described it, “so many are the conditions which would have had to have been satisfied to get it going.” Jacques Monod concurred; in his 1976 book Chance and Necessity he wrote, “Man knows at last that he is alone in the indifferent immensity of the universe, whence which he has emerged by chance.”

Today the pendulum has swung decisively the other way. Many distinguished scientists proclaim that the universe is teeming with life, at least some of it intelligent. The biologist Christian de Duve went so far as to call life “a cosmic imperative.” Yet the science has hardly changed. We are almost as much in the dark today about the pathway from non-life to life as Darwin was when he wrote, “It is mere rubbish thinking at present of the origin of life; one might as well think of the origin of matter.”

There is no doubt that SETI – the search for extraterrestrial intelligence – has received a huge fillip from the recent discovery of hundreds of extra-solar planets. Astronomers think there could be billions of earthlike planets in our galaxy alone. Clearly there is no lack of habitable real estate out there. But habitable implies inhabited only if life actually arises.

I am often asked how likely it is that we will find intelligent life beyond Earth. The question is meaningless. Because we don’t know the process that transformed a mish-mash of chemicals into a living cell, with all its staggering complexity, it is impossible to calculate the probability that it will happen. You can’t estimate the odds of an unknown process. Astrobiologists, however, seem more preoccupied with the chances that microbial life will eventually evolve intelligence. Although biologists can’t do the math on that either, at least they understand the process; it is Darwinian evolution. But this is to put the cart before the horse. The biggest uncertainty surrounds the first step—getting the microbes in the first place.

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