In August 1977, a radio telescope nicknamed Big Ear caught a 72-second roar of radio noise so striking that astronomer Jerry Ehman circled it in red pen and wrote 'Wow!' in the margin. Decades later, we have never heard it again. This deep dive goes beyond the alien-phone-call mythos to examine the hard data behind SETI's most famous and frustrating mystery.

We decode what '6EQUJ5' actually means, why 1420 MHz is the cosmic 'water hole,' and how the telescope's design pins the signal to deep space. Then we work through every explanation, from military interference and comets to a naturally occurring hydrogen maser, and confront why a non-repeating event can never be confirmed.

• How the hydrogen line and the 'water hole' shaped where humanity decided to listen
• Why '6EQUJ5' is a standard-deviation intensity scale, peaking at ...