Where is everybody?
William Brilliant
‘Where is everybody?’ exclaimed Enrico Fermi to his lunch companions one s ummer’s day in 1950. He wasn’t referring to the empty restaurant. Instead, he was referring to one of the greatest, most perplexing, and — as of yet — still unanswered questions of astronomy, a question that has since been dubbed the Fermi paradox: where are all the aliens? More specifically, where are all the intelligent alien species with whom we could hold a conversation? Despite broadcasting our location into space via radio waves for nearly a century, despite scouring every inch of the night sky with radio telescopes in the hopes of receiving a response, we have not heard a single peep from any galactic neighbours. This essay will attempt to explain why this is so perplexing and offer just a few of the many possible explanations that people have put forward for the paradox. Firstly, it is important to understand why there is a paradox at all. One could reasonably assume that if we haven’t found any intelligent alien life then it is simply because there isn’t any. What’s so hard to understand about that? Enter Frank Drake. In 1961, he developed an equation to estimate the number of intelligent alien civilizations that should exist and be broadcasting their location to us, 1 wittingly or not. The Drake equation is beautifully simple, merely multiplying a series of numbers and probabilities together. The numbers Drake used are: the number of new stars born in our galaxy each year; the fraction of those stars with planets around them; the average number of habitable planets around these stars; the fraction of those habitable planets that end up developing life; the fraction that end up developing intelligent life; the fraction of those intelligent species that create technology that would send out detectable signals; and the length of time for which those signals are being sent out. Unfortunately, Drake didn’t know the exact value of most of his numbers, yet with his best estimations he calculated that there should be anywhere between 1,000 and 100,000,000 alien civilizations which have the technology to communicate with us. Even if we take the lower estimate, that means there should be 1,000 other alien species that we should be able to detect. So why haven’t we found them yet? Many possible answers have been offered for the Fermi paradox, but I shall focus on three. The first is the possibility that there really are no aliens out there. This would suggest that at least one (although probably several) of Drake’s parameters are incorrect. Interestingly, with the advancement of telescopes and astronomical observation, we can now estimate some of those parameters to a higher degree of accuracy. Current estimates from NASA and ESA put the rate of stellar creation at 1.5 to 3 new stars per year, 2 whilst we now know that most stars have planets, with as many as 22% of sun-like stars having habitable Earth-like planets, 3 leading to at least 4 billion planets that should be capable of supporting life. 4
1 Robitzski 2018. 2 Kennicutt and Evans 2012. 3 Petigura 2013: 19273 4 Plait 2013.
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