In the search for extraterrestrial intelligence, there’s truly just one big question: Where is everyone? This question has actually haunted alien hunters ever since the Nobel-winning physicist Enrico Fermi positioned it to some coworkers over lunch 70 years earlier. There are billions of sun-like stars in our galaxy, and we now know that most of them host planets. After years of searching, astronomers haven’t found any that appear to host life. This is the so-called Fermi paradox: Our galaxy looks like it should be bursting with alien civilizations, but we can’t discover a single one.
Researchers dealing with the search for extraterrestrial intelligence, or SETI, have proposed a variety of services to the Fermi paradox over the years. The most persuasive response is also the most apparent: Perhaps smart life is simply far more uncommon than we thought.
How rare? Lots of researchers have tried to answer this notoriously tricky concern. Based upon their conclusions, there are between no and 100 million extraterrestrial civilizations in the Milky Way. That is not a specifically handy series of price quotes, so a pair of physicists in the UK just recently took another stab at it and came to a remarkably specific conclusion. As detailed in a new paper released this week in the Astrophysical Journal, the duo computed there need to be at least 36 communicating extraterrestrial civilizations in our galaxy.
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That is … not a lot, certainly, and it has some dismaying ramifications. According to the paper, this would mean we’ll likely have to spend centuries looking for an extraterrestrial civilization prior to we find one, and it likewise suggests that our closest next-door neighbors might be up to 17,000 light-years away. “We’ve gone from being rather bullish on there being life in deep space to being a bit more cynical as time goes on,” says Christopher Conselice, an astrophysicist at the University of Nottingham and one of the authors of the paper. “I think that’s natural, today we have the type of details we need to make some genuine quotes based upon affordable presumptions about how life could form on other worlds.”
Attempts to approximate the frequency of intelligent life in the galaxy go back to the very start of modern SETI. In 1961, just a few months after concluding the world’s first radio search for ET, the planetary astronomer Frank Drake convened a small conference of leading American researchers to go over the future of SETI– or whether it needs to have any future at all. To arrange the conference, Drake made a list of concerns that he considered important to figuring out the chances that the search would succeed.
A few of these questions– like figuring out the typical rate of star formation in the galaxy and the number of stars host planets– were possible for scientists to respond to before first contact. Others– like what fraction of worlds produce intelligent life and how long that
