On the night of August 15, 1977, a radio telescope at Ohio State University was pointed at a quiet patch of sky in the constellation Sagittarius. It picked up a signal so strong and so strange that the astronomer reviewing the printout a few days later circled it in red pen and wrote one word in the margin: Wow! Nearly fifty years on, nobody has a clean explanation for what it was.
The telescope was called Big Ear, and it was a goofy-looking thing — a flat metal field roughly the size of three football fields. It wasn't scanning, it was sitting still, letting the Earth's rotation drag the sky past it. Any real signal from space would rise, peak, and fall in about 72 seconds as it swept thorugh the beam. That's exactly what the Wow signal did. It was narrow-band (which natural sources rarely are), about thirty times louder than the background noise, and it was sitting almost exactly on the hydrogen line at 1420 MHz — the frequency a lot of scientists had argued any alien civilization would use to say hello, because hydrogen is the most common thing in the universe and everyone would know to listen there.
The astronomer, Jerry Ehman, spent the rest of his career being careful not to overclaim. He didn't say it was aliens. He said it was unexplained, and that's still where things stand. Big Ear pointed back at that same patch of sky dozens of times in the following years. Other telescopes have looked too. Nothing has ever come back. A 2017 paper tried to pin it on a passing comet, but other astronomers ran the numbers and the comet theory mostly fell apart — comets don't emit that strongly at that frequency. Satellites have been ruled out because the frequency sits inside a protected radio-quiet band reserved for astronomy. Earthly interference doesn't fit the rise-and-fall pattern of a fixed sky source.
It's a 72-second mystery from a piece of cornfield Ohio engineering, and it's outlasted the telescope itself (Big Ear was demolished in 1998 to make room for a golf course, which feels like a very American ending). The signal might have been a one-off natural burst we don't yet understand. It might have been somebody else, deciding once and never again to say hi. We'll probably never know, and there's something quietly great about a question that just sits there, unsolved, while we all get on with our Fridays.
If you've got a favorite unsolved-mystery fact you think we should write about on a future Friday, send it our way — we collect these.
— Alexander & Amanda @ SBATC
