The Wow! Signal
A 72-second radio signal from deep space. The astronomer wrote 'Wow!' on the printout. It matched what an alien signal should look like. It never repeated. Forty-plus years later, we still don't know what it was.
The Wow! Signal is the strongest candidate for an extraterrestrial radio transmission ever received. Detected in 1977, it has never been explained or repeated.
The Detection
According to documented records:
On August 15, 1977:
- The Big Ear radio telescope at Ohio State University detected an anomalous signal
- Astronomer Jerry Ehman circled the data on the printout
- He wrote “Wow!” in the margin
- The signal lasted 72 seconds
- It came from the constellation Sagittarius
The Signal Characteristics
What made it remarkable:
- It was 30 times stronger than background noise
- It was at the hydrogen frequency (1420 MHz)—where SETI expects alien signals
- It matched the expected profile of an extraterrestrial signal
- It appeared to come from outside our solar system
- It showed the “signature” expected from a deep-space source
Why 72 Seconds?
The duration was determined by the telescope:
- Big Ear was fixed, scanning as Earth rotated
- A signal from space would be detected for 72 seconds
- The Wow! Signal matched this window exactly
- This suggests an external, fixed-point source
The “Wow!”
Jerry Ehman’s famous annotation:
- He was reviewing data three days later
- The signal was immediately recognizable as unusual
- His exclamation captured the moment perfectly
- The name stuck
The Search for Repetition
Despite extensive efforts:
- No repeat of the signal has been detected
- Big Ear searched the same spot many times
- Other telescopes have looked
- The signal never returned
Theories
Extraterrestrial Intelligence: An alien transmission—the leading theory among hopefuls.
Interstellar Comet: A 2017 theory suggested hydrogen clouds around comets.
Earth Interference: A satellite or ground-based signal reflected back (disputed).
Unknown Natural Phenomenon: Something in space we don’t understand.
Equipment Malfunction: An error in the telescope system (considered unlikely).
The Comet Hypothesis
Professor Antonio Paris proposed in 2017:
- Two comets were in that area in 1977
- Hydrogen clouds around comets could produce the signal
- This theory is controversial
- Many astronomers don’t accept it
Why It Matters
The Wow! Signal represents:
- The best candidate for alien contact
- The challenge of one-time signals
- How we might receive ET communication
- The limits of our detection capabilities
SETI Implications
The signal influenced:
- How we search for extraterrestrial intelligence
- The importance of the hydrogen frequency
- The difficulty of confirmation
- Hope that signals exist
Current Status
The mystery remains:
- No definitive explanation exists
- The original data is preserved
- The site is now a golf course (Big Ear was demolished)
- The search continues elsewhere