Wow! Signal
The 1977 narrowband radio signal detected by the Big Ear radio telescope at Ohio State University, considered the strongest candidate for extraterrestrial communication ever detected.
OVERVIEW
The Wow! Signal was a 72-second narrowband radio signal detected on August 15, 1977, by Dr. Jerry Ehman at Ohio State University's Big Ear radio telescope. The signal was so striking that Ehman circled the computer printout and wrote 'Wow!' next to it. The signal came from the constellation Sagittarius and exhibited all the characteristics expected of an extraterrestrial communication: narrow bandwidth (10 kHz), transmission at the hydrogen line frequency (1420 MHz), and signal strength 30x above background. Despite extensive searches for it, the signal was never detected again. Explanations include natural astrophysical sources, terrestrial interference, and extraterrestrial intelligence.
KNOWN FACTS
The signal's 30x above-background strength makes it unlike any known natural phenomenon
The 1420 MHz hydrogen line frequency is a 'magic frequency' that ET researchers would logically use
The signal was only detected on one of the two receiver horns, consistent with a distant point source
No known natural astrophysical source produces such a narrowband signal at that intensity
The signal was not from Earth technology (no satellites transmitted at that frequency in 1977)
CLAIMS
The Wow! Signal was a transmission from an extraterrestrial intelligence
The signal's characteristics (narrowband, hydrogen line frequency) suggest intentional design
Multiple subsequent searches could not find the signal, consistent with a deliberate beacon
The signal originated from outside the solar system (based on Doppler shift analysis)
The signal was stronger than any natural radio source in the galaxy
EVIDENCE FOR
The signal's 30x above-background strength makes it unlike any known natural phenomenon
The 1420 MHz hydrogen line frequency is a 'magic frequency' that ET researchers would logically use
The signal was only detected on one of the two receiver horns, consistent with a distant point source
No known natural astrophysical source produces such a narrowband signal at that intensity
The signal was not from Earth technology (no satellites transmitted at that frequency in 1977)
EVIDENCE AGAINST
The signal was never detected again despite decades of searching, suggesting it was not a repeatable beacon
A passing comet (266P/Christensen) was proposed as a potential source (2017 hypothesis, still debated)
The signal could have been terrestrial interference from a military satellite or aircraft
The lack of modulation or information content suggests it was not a communication signal
SETI protocols require repeatability before classifying a signal as confirmed extraterrestrial
OPEN QUESTIONS
No open questions recorded.
SOURCES
TIMELINE
Wow! Signal detected by Big Ear telescope
Ehman discovers the signal on printout
Comet hypothesis proposed (contested)
Ongoing analysis; no definitive explanation