Cobra Effect · Big open questions
Are we alone in the universe?
Why no sign of life beyond Earth has been confirmed, despite planets everywhere.
7 cards, read aloud in 2:59, with a test and sources.
In the summer of 1950, Enrico Fermi raised a puzzle over lunch at Los Alamos.
Talking with colleagues about life elsewhere, he asked, in effect, where everybody was. If intelligent life were common, some sign of it might surely have reached us by now. Accounts of his exact words differ, but the question stuck.
In 1960, Frank Drake pointed a radio telescope at two nearby stars and listened.
Project Ozma listened for about a hundred and fifty hours, near the radio frequency given off by hydrogen. It heard nothing but noise, and one false alarm that turned out to be an aircraft. The next year, Drake wrote down an equation to organise the unknowns.
Drake’s equation lists what decides how many civilisations we might hear.
It asks how many stars form, how many have planets, how many planets suit life, how often life starts, becomes intelligent and sends signals, and how long that lasts. Nobody knows most of those numbers. The small group that first discussed it came up with answers from about a thousand to a hundred million.
In 1977, an Ohio radio telescope picked up a strong, narrow signal.
It lasted seventy two seconds, was close to the frequency of hydrogen, and came from the direction of the constellation Sagittarius. An astronomer checking the printout circled it and wrote Wow beside it. It has never been detected again, and recent ideas that a natural flare caused it are still unconfirmed.
We now know that planets are everywhere.
More than six thousand planets beyond the Solar System have been confirmed. Some orbit where liquid water could exist, though most known planets are nothing like Earth. That makes the silence more puzzling, not less.
Recent claims of signs of life have not held up, or are still unconfirmed.
In 2025, a team reported a hint of a possible sign of life in the air of a planet about a hundred and twenty light years away. Other teams reanalysing the data found no convincing signal. A gas reported on Venus in 2020 is still disputed. On Mars, a rover found spotted rocks that NASA calls a potential sign of life, but chemistry without life has not been ruled out.
So when a headline says signs of alien life were found, ask whether anyone has confirmed them.
As of 2026, there is no confirmed evidence of life anywhere beyond Earth. That may be because life is rare, or because we have searched only a tiny part of the sky. Both possibilities are still open.
Sources
- NASA says Mars rover discovered potential biosignature last year, NASA. The spotted Mars rocks, and why they are not proof.
- Webb discovers methane and carbon dioxide in the atmosphere of K2-18 b, NASA Science. A first look at a distant planet’s air, with its caveats.
- NASA Exoplanet Archive, NASA and Caltech. The live count of confirmed planets beyond the Solar System.
Nearby ideas
- The first planet around a Sun-like star. How a star's tiny wobble revealed a giant planet where none was expected.
- How did life begin?. What is known about how life began, and which parts are still guesses.
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- What is dark matter?. What the evidence says about dark matter, and why nobody knows what it is.
- What is speeding up the universe?. Why the universe's expansion is speeding up, and the rival ideas about why.
- Why is there more matter than antimatter?. Why the universe is made of matter, when the Big Bang should have made equal antimatter.
- Why do we have experiences at all?. Why brain science can track experience, but not yet explain why it exists.