Alien life should be everywhere. The sheer abundance of stars in the universe (the number far outstrips the total number of grains of sand on every beach on Earth) suggests that, somewhere, an intelligent lifeform should be warming itself on a distant planet. Even if life evolves rarely, ET should be phoning.
Yet, by all appearances, humanity seems to be flying solo in our galaxy, and perhaps the universe. Many solutions have been proposed to solve this riddle, known as the Fermi Paradox. The aliens are hiding. They’ve entered suspended animation until more propitious conditions arise. A Great Filter makes the leap from “life “to “intelligent life” improbable, if not impossible. They’ve blown themselves up.
Researchers of Oxford University’s Future of Humanity Institute have another answer. It’s likely intelligent life doesn’t exist at all, outside of Earth.
In a paper submitted to the Proceedings of the Royal Society of London (it appeared online this month on the pre-publication site arXiv), the researchers write that there is “a substantial ex ante probability of there being no other intelligent life in our observable universe,” and we shouldn’t be surprised if we fail to detect any signs of it. In other words, there is no need to speculate about the fate of aliens. It’s likely they’ve never existed, they assert in the paper, titled “Dissolving the Fermi Paradox.”
The Fermi Paradox derives from a question reportedly posed by physicist Enrico Fermi during a 1950 lunch in the Los Alamos National Laboratory in the state of New Mexico. According to Scientific American, a group of scientists were discussing a New Yorker cartoon showing aliens emerging a spaceship, onto the streets of New York City. “Where is everyone?” Fermi asked. While he was likely questioning the possibility of interstellar travel, later accounts suggested he was casting doubt on the existence of extraterrestrials themselves, the magazine reports.
Scientists have been trying to answer Fermi’s question ever since. Many of the most rigorous attempts have built on a postulation known as the Drake equation. There are plenty of unknowns, but the equation suggests it’s plausible thousands of detectable alien civilizations could be roaming the Milky Way based on the probability of seven factors. The equation:
- N: total detectable alien civilizations in the Milky Way
- R∗: rate of star formation per year
- fp: fraction of stars with planets
- ne: Earth-like (or otherwise habitable) planets per system with planets
- fl: fraction of such planets with life
- fi: fraction with life that develop intelligence
- fc: fraction of intelligent civilizations that are detectable/contactable
- L: average longevity of such detectable civilizations
Previous estimates of the Drake equation have assigned a single number to those variables. The recent study sought to make a more informed guess. It relies on our latest knowledge of biology, chemistry, and cosmology, and uses a distribution of probabilities (a range) to capture the most likely scenarios, rather than assign a single value.
When they did, the researchers found that the possibility we’re alone in the galaxy is far higher than presumed given the truly gargantuan number of possible home planets. The authors assert that the chance humanity stands alone among intelligent civilizations in our galaxy is 53%–99.6%, and across the observable universe is 39%–85%.
Since the Fermi “paradox” exists only if we are confident alien civilizations are out there, this uncertainty suggests we may just be the lucky ones—thus, there is no such paradox. “We should not actually be all that surprised to see an empty galaxy,” the authors write. But don’t give up entirely. The Drake equation, at best, merely gives us a way to formalize what is still unknowable. It’s a big universe.