Why haven't we found aliens? - Video

Why haven't we found aliens? We've checked about a hot tub's worth of ocean.

That is how Wright, Kanodia and Lubar (2018) pictured radio searches for alien signals so far: about a large hot tub or a small swimming pool of water, out of all of Earth's oceans. Science News puts it at about 7,700 litres. Years earlier Jill Tarter called it one glass of water.

And inside that tiny sample, something turned up. On 15 August 1977 the Big Ear radio telescope in Ohio caught a signal that lasted the full 72 seconds it could watch that spot. Jerry Ehman circled it on the printout and wrote "Wow!" It has never been detected again, and nobody has explained it.

Meanwhile, microlensing suggests our galaxy holds at least one planet per star on average (Cassan and colleagues, 2012), and it has 100 to 400 billion stars. Around 1950, over lunch at Los Alamos, Enrico Fermi reportedly asked the question that still has no agreed answer: where is everybody? We have even sent directions: Frank Drake devised a map showing the Sun's position relative to 14 pulsars, carried on the Pioneer 10 and 11 plaques and on the Voyager Golden Records. Would you have sent it?

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