The Implications of Cosmic Silence
The universe is incomprehensibly vast, with billions of other planets circling billions of other stars. The potential for intelligent life to exist somewhere in this cosmic soup is enormous.
So, where is everybody?
That’s the Fermi paradox in a nutshell. Named after physicist Enrico Fermi, it takes the Drake equation – a probabilistic estimate of the number of intelligent civilizations in the Milky Way named after astrophysicist Frank Drake – to a philosophical level. There are a handful of explanations for the Fermi paradox, from the idea that we have already been contacted and didn’t realize it to the hypothesis that we are all by ourselves. But the bottom line is that to the best of our knowledge, no one wants to talk to us.
Daniel Whitmire, a retired astrophysicist who teaches mathematics at the University of Arkansas, used to think the cosmic silence indicated that the time-window of opportunity was short or that aliens just weren’t interested.
“I taught astronomy for 37 years,” said Whitmire. “I used to tell my students that by statistics alone we have to be the dumbest guys in the galaxy. After all we have only been technological for about 100 years while other civilizations could be more technologically advanced than us by millions or billions of years.”
Recently, however, he’s changed his mind. By applying a statistical precept called the principle of mediocrity – the idea that in the absence of any evidence to the contrary we should consider ourselves typical, rather than atypical – Whitmire concluded that maybe we’re not the dumbest species in the galaxy after all. That may sound like good news, but it isn’t.
The principle of mediocrity squares with humankind’s evolving view of itself. We used to think we were at the center of the universe, and the heart of our solar system. That would make us special, or atypical. We’ve come to realize we’re not at the center of it all. “Every time it was thought we were special, it turned out to be wrong,” Whitmire said. “We should at least be a little embarrassed.”
In a paper published Aug. 3 in the International Journal of Astrobiology (and available on his personal website), Whitmire argues that if we are typical, it follows that species such as ours go extinct soon after attaining technological knowledge, “and that this event results in the extinction of the planet’s global biosphere.”
“If we are typical,” Whitmire said, in the understated language of science, “then it has implications.”
Whitmire uses two observations in his argument: We are the first technological species to evolve on Earth, and we are early in our technological development. (He defines “technological” as a biological species that has developed electronic devices and can significantly alter the planet.)
The first observation seems obvious, but as Whitmire notes in his paper, researchers believe the Earth should be habitable for animal life at least a billion years into the future. Based on how long it took proto-primates to evolve into a technological species, that leaves enough time for it to happen again up to 23 times. On that time scale, there could have been others before us, but there’s nothing in the geologic record to indicate we weren’t the first. “We’d leave a heck of a fingerprint if we disappeared overnight,” Whitmire noted.
By Whitmire’s definition we’ve been “technological” since the industrial revolution and the invention of radio, roughly 100 years. According to the principle of mediocrity, a bell curve showing the ages of all extant technological civilizations in the universe would put us in the middle 95 percent. In other words, technological civilizations that last millions of years, or longer, would be highly atypical. Since we are also first, this implies that other technological civilizations should typically find that they too are first. The principle of mediocrity allows no second acts. The implication is that once civilizations become technological, they flame out and take the biosphere with them.
How long do we have? Whitmire argues that the principle holds for two standard deviations, or in this case about 200 years. But because the distribution of ages skews older (there is no absolute upper limit, but the age can’t be less than zero), he doubles that figure and comes up with 500 years, give or take. The assumption of a bell-shaped curve is not absolutely necessary, either. Other assumptions give roughly similar results.
Of course, there’s always the possibility that we are atypical and our species’ lifespan will fall in the outlying 5 percent of that bell curve. If that’s the case, we’re back to the nugget of wisdom Whitmire taught his astronomy students for more than three decades.
“If we’re not typical then my initial observation would be correct,” he said. “We would be the dumbest guys in the galaxy by the numbers.”