The famous “Wow!” signal was detected by Jerry Ehman in 1977. It was a very strong, narrowband (10-kHz wide) signal that lasted as long as his Big Ear (and our planet) was pointed in its direction. It was in the hydrogen “waterhole” band of 1420 MHz (or precisely 1420.40575177 MHz). In fact, the two estimates of the frequency bracket the waterhole frequency perfectly.
Why was this not declared proof of alien intelligence in space?
- It wasn’t located precisely on a star.
- It wasn’t repeated. The signal was only received once.
What did we do? We sent the Arecibo message.