Contra Fermi Paradox is Not Contra UFOs
Sandberg, Ord, and Hanson papers discussed
The Fermi Paradox is the idea that it’s surprising that the universe looks devoid of alien life, because with an estimated 10^25 planets in the universe, you’d expect we’d see something out there.
UFOs are weird things that fly around, possibly aliens.
These are related, but not the same. A paper that refutes the Fermi Paradox does not refute UFOs and sometimes actually supports the likelihood of UFOs.
(Other objections to UFOs you might have are covered in these posts.)
In fact, UFO sightings are contra the Fermi Paradox. The paradox asks, “Where are the Aliens?”, and UFO sightings say, “Right here!”
Here are three commonly cited papers on the topic, and what they say:
1. Dissolving the Fermi Paradox
This paper by Sandberg, Drexler, and Ord was reviewed on Slate Star Codex, and it delivers on the title: the Fermi Paradox largely dissolves. Using a Monte Carlo simulation to map out the scenarios from other papers in the field, they find that 30% of the time, you’d expect less than one civilization per galaxy.
This would be a Poisson distribution, with intelligent life being very rare. Most galaxies have no intelligent life, but occasionally, improbably good conditions allow for one. Almost never would two be in the same galaxy, so most observers wouldn’t see anyone else.1
The math checks out, so does that mean aliens are unlikely?
No. That means the Fermi Paradox is unlikely. In 30% of scenarios, there is no intelligent life in the typical galaxy, so we shouldn’t be surprised if we’re all alone. However, on average, there are multiple intelligences per galaxy in 70% of scenarios. More likely than not, we are not alone. Seeing UFOs is what we should expect.
If you don’t see aliens, don’t be surprised, it’s 30% of scenarios.
If you do see aliens, don’t be surprised, it’s 70% of scenarios.
2. Eternity in six hours
Another paper by Sandberg, plus Armstrong, calculates that just six hours of a star’s energy is enough to send self-replicating probes across the known universe. Combine this with Earth being a relatively young planet, and there’s been plenty of time for earlier-emerging civilizations to reach us.
That means if we haven’t seen any probes, there’s probably no other intelligent life in the universe. The math does check out; they would have gotten to us by now.
The paper claims: If there are no probes, there are no aliens.
The paper does not claim: There are no aliens, so there are no probes.
It’s no aliens, conditional no probes! There is only one condition, and UFOs violate it.
3. Grabby Aliens
Robin Hanson’s grabby aliens paper isn’t an answer to the Fermi Paradox, but rather why intelligent life seems to have appeared on Earth so quickly. He says it’s because “grabby aliens” gobble up all the other planets before life can emerge on them. Earth had life early because that was the only time it was possible; later on, all the planets will already be consumed.
His support for the claim that life was quick to show up on Earth is that most stars are much longer-lived than the Sun:
If stars of all masses were equally habitable, most habitable years should lie in planets at the far-longer-lived small mass stars. After all, 95% of stars last longer than our sun, and some last roughly two thousand times longer.
But there’s a much simpler explanation: stars are not all equally habitable—small mass stars might not support life. Having more years with a star is not useful if those extra years don’t support life. It could be that small stars don’t support rocky planets with an atmosphere, or it could be that their low luminosity (<10% of the Sun’s) won’t support complex life.
We orbit a star in the ~95th percentile for mass. If all stars are equally habitable, why aren’t we on one of the far more numerous, low-mass, and long-lived stars? Our improbably big Sun implies that larger stars are more likely to support life.
Grabby Aliens on the Fermi Paradox
The Grabby Aliens Hypothesis has to address the Fermi Paradox, because if the universe is being grabbed up, we should see this on our telescopes. Hanson answers that if it happens fast enough, i.e., a fraction of the speed of light, we won’t see it coming:
If their expansion speed were within∼25% of lightspeed, a selection effect implies that we are less likely to see than to not see such volumes.
The paper’s position is not only that there are aliens, but they “now control 40-50% of the universe volume.”
Extraterrestrial contact is therefore expected in about half of Grabby Alien scenarios, and the author believes they’re already here.
Of course, this means our own emergence was highly unlikely, but we ask these questions only when it worked out, so we have to take our existence as a given.