system
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human
ELI5 Wow signal detected on 1977?

I tried to read the wikipedia article, it just goes over my head, I'm not able to understand all these technical jargons. Can anybody eli5 this? Thanks.
gpt
Modern astronomers don't just look at the sky using their eyes and normal lenses (visible light), but they also monitor radio emissions. 

Some astronomers in particular are looking for evidence of intelligent extraterrestrial life. One hypothesis is that intelligent aliens would use radio signals at least for themselves and possibly to send radio signals to other forms of intelligent life. But there are a lot of possible radio frequencies (the radio "spectrum"), so which ones should we monitor (monitoring the whole spectrum is very expensive)?

Some believe intelligent civilizations would use the 1420.4 MHz frequency because it is related to the hydrogen atom, and hydrogen is the most common element in the universe.

In 1977, an astronomer monitoring radio frequencies around 1420 MHz found out a 72-second signal that was interesting for three reasons:

- it was pretty loud (*high signal to noise ratio* in technical terms)

- its frequency was almost exactly 1420.4 MHz

- it had a small bandwidth, which means the signal frequencies were very close around the center frequency of 1420.4 MHz. 

A lot of hypothesis have been made, including natural origins, intelligent aliens, and interference from someone transmitting on that frequency on Earth (although that frequency is not supposed to be used, but that doesn't prevent someone from using it illegally). Also, a similar signal has never been detected again.