Is there really a Fermi paradox? Why scientists disagree about the silent sky
September 29, 2026 · 14 min read
Adam Frank argues there is no Fermi paradox because we have barely looked, Sean Carroll weighs why we don't see aliens, and Sara Walker suggests a perceptual filter may keep us from recognizing them. Comparing their answers shows how much of the paradox rests on assumptions rather than data.
The rules, numbers and steps worth keeping in front of you.
- Fermi's 1950 question: where is everybody, if even slower-than-light travelers could settle the galaxy?
- Adam Frank: two versions. Indirect: we hear no signals. Direct: why are they not here?
- Frank, citing Jason Wright: SETI has searched a hot tub's worth of an ocean.
- Frank's simulation: one expansion wave crosses the galaxy quickly, but finite lifetimes leave empty bubbles lasting millions of years.
- Frank and Gavin Schmidt: a 10,000-year industrial civilization would leave no obvious trace after 100 million years.
- Frank: every star has planets, and about one in five has one in the habitable zone.
- Frank's pessimism line: we are the only civilization ever only if the odds per planet are below one in 10 to the 22.
- The pessimism line covers all cosmic history; it does not mean anyone is nearby.
- Sean Carroll: the simplest explanation for the silence is that they are not there.
- Carroll: a great filter would have to work every single time, so he gives it low credence.
- Carroll: a parked probe in our solar system is a better bet than a radio message.
- Sara Walker: a great perceptual filter might hide advanced life, as microbes were hidden before microscopes; she holds the idea loosely.
- Frank: we have one example of life; a second would change everything.
- None of this supports claims that aliens are visiting now.
This is the short form. The full insight has every expert's reasoning, their own words and the sources.