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I n 1950 Enrico Fermi, an American physicist of Italian origin, asked a very simple question that has profound implications for one of the most important scientific puzzles: life exists- she beyond the Earth? The story goes that during a lunchtime conversation with colleagues at the Los Alamos National Laboratory in New Mexico, the issue of flying saucers was raised. The conversation was light, and it does not seem like any of the scientists at this gathering believed in extraterrestrials. But Fermi just wanted to know, "Where is everyone?"
His point was that since the age of the universe is so big and its size so vast, with hundreds of billions of stars in the Milky Way only, unless the Earth is Surprisingly special, the universe should be teeming with life. This could include smart species that are advanced enough to have the knowledge and technology to travel in space. They should have colonized the whole galaxy now. So where are they all?
More recently, the late Stephen Hawking made similar arguments. He said, "For my mathematical brain, numbers alone make extraterrestrial thinking perfectly rational." Hawking articulated the same popular argument as Fermi – that the vastness of the universe only guarantees that we have company
. scientists began to take the subject more seriously. One of the most exciting areas of research in astronomy has been the discovery of extra-solar planets, worlds orbiting other stars than our sun. Many of them even seem to look like the Earth in terms of size and climate. Astronomers now believe that there are billions of these other worlds, many of which will have life-appropriate conditions. The probability of life, perhaps even the intelligent life, existing on at least one of them must therefore be overwhelming.
Now scientists at the Institute of the Future of Humanity in Oxford poured cold water on Hawking and other "optimism." They performed a thoughtful statistical badysis dissecting a mathematical relationship known as the Drake equation, which allows us to calculate the probability of extraterrestrial life based on the combined probabilities of all the ingredients for life being in place.
D & # 39; At first, it is clear that Drake's equation is not very scientific, for the sole reason that some of the factors that must be introduced into this equation are purely conjectural at this stage. is not the least: given all the things we believe are necessary for life (source of energy, liquid water and organic molecules), what is the probability that life will appear?
study offer two ideas, a pessimist and l & # 39; The other is that the Fermi paradox is easy to solve. The reason we have not received any message from ET is that, well, there is no ET. They calculate the probability that we are alone in the universe to be between 39% and 85% and the probability that we are alone in our own galaxy between 53% and 99.6%. Basically, do not hold your breath.
Biologists, of course, hate all these stupid speculations. They rightly point out that we still do not understand how life was born here on Earth, so how can we trust to anticipate its existence or its non-existence elsewhere? Some claim that life on Earth appeared fairly quickly after the good conditions emerged almost 4 billion years ago, when our planet had cooled enough for liquid water to exist. Does not that mean that he could easily appear elsewhere too? Actually no. A statistical sample of one tells us nothing. It is quite possible that biology is a bizarre local aberration, the product of a chemical blow so unlikely that it did not occur anywhere else in the observable universe.
So where are we? Well, there is reason to believe that we could have an answer in the next decade or two, one way or the other. Astrobiologists are on the cusp of looking for exoplanets for the gases produced by microbial life using sophisticated next-generation space telescopes. There is also the possibility of finding microbial life closer to home, under the ice of many of the moons of Jupiter and Saturn.
I said that the study also provided joy. Some have claimed that we have not yet found ET because intelligent life (including us) always cancels out before we can successfully develop technology for travel or interstellar communication. But perhaps the silence is simply because there are no such extraterrestrial civilizations. Thus, as the authors say, pessimism about our own future is therefore unfounded. We can be alone, but we can just survive.
• Jim Al-Khalili is a professor of physics and professor of public engagement in science at the University of Surrey
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