If you believe that we are not alone in the universe — or want to believe — then the "Wow!" signal offers thrilling proof that someone, somewhere, is trying to say "hello."
Then there's the bad news. In the more than three decades since Jerry Ehman circled the astonishing "6EQUJ5" on his printout, no SETI radio telescope has recorded anything like the "Wow!" signal. The Big Ear even scanned the same patch of sky 100 more times, but found nothing [source: Gray and Marvel].
Robert Gray, an amateur astronomer and data analyst with a passion for the "Wow!" signal, conducted the most serious attempt to replicate the signal using one of the biggest and baddest radio telescopes on Earth, the Very Large Array (VLA) in New Mexico.
In 1995 and 1996, Gray aimed the VLA at Sagittarius, the first time the telescope was used expressly to search for signs of extraterrestrial life. The VLA — which combines the power of 27 separate radio antennas — is 100 times more sensitive than the Big Ear, which was retired in 1997 [sources: NRAO, Gray and Marvel].
Sadly, Gray found no trace of the "Wow!" signal with the VLA. But that wasn't enough to convince him that the original recording was some kind of glitch [source: Gray and Marvel].
In a 2012 interview published in The Atlantic, Gray argued that our assumptions about extraterrestrial radio transmissions are all wrong. We imagine a constant beacon shining toward Earth from a distant planet. But the energy required to sustain such a broadcast — in all directions, at all times, across millions of light years — is equal to thousands upon thousands of our biggest power plants.
What if the alien civilization isn't a hyper-advanced race with limitless resources, but something more like ourselves? The more economical approach would be to broadcast the signal from a type of radio "lighthouse" that transmits its message in only one direction at a time. If that's the case, then our current system of searching for alien life — focusing on one patch of sky for 20 minutes before moving on to the next — would require tremendous luck to catch the signal as it briefly flashes our way [source: Andersen].
In 2017, a scientist and professor at St. Petersburg College, Florida named Antonio Paris claimed to have solved the mystery of the Wow signal. He believed an undiscovered comet "photobombed" the Big Ear 1977 observatory.
Paris found two comets, 266P/Christensen and 335P/Gibbs, which were discovered in 2006 and 2008 respectively, would have been near to the Chi Sagittarii observing region on Aug. 15, 1977. 266P/Christensen made a return visit to the same patch of sky between 2016 and 2017. After an extensive observing campaign, Paris found that 266P/Christensen emitted a radio signal at 1420.25 MHz. "The results of this investigation, therefore, conclude that cometary spectra are detectable at 1420 MHz and, more importantly, that the 1977 "Wow!" Signal was a natural phenomenon from a solar system body," Paris says.
Case closed? Not every scientist is convinced about this explanation. Some note the 266P/Christensen was not in the right spot on August 15, 1977. The signal was also only detected by one of the 'feed horns,' that are the telescope's detectors. Comets don't move fast enough to have missed being detected by both feed horns [source: Cooper].
So, the Wow Signal mystery continues -- for now.