August 15, 1977. Jerry Ehman was sitting in a cramped room at Ohio State University, scanning computer printouts from the "Big Ear" radio telescope. It was routine. Boring, honestly. Until it wasn't. He saw a vertical column of letters and numbers—6EQUJ5—that broke every pattern the telescope had ever recorded. He circled it in red ink and scribbled "Wow!" in the margin.
Space is usually quiet. Like, eerily quiet. But for exactly 72 seconds, the universe screamed at us.
We’ve been trying to find that scream again for nearly fifty years. It’s the ultimate "cold case" of astronomy. When people talk about the Wow! signal, they aren't just talking about a weird blip on a chart. They're talking about the one time we might have actually stumbled across something that wasn't us.
What actually happened at the Big Ear?
The Big Ear telescope wasn't some high-tech dish like you see in movies. It was huge, flat, and looked more like a giant metallic parking lot. It didn't "point" at things; it let the Earth's rotation sweep the sky.
When the Wow! signal hit, it came from the direction of the constellation Sagittarius. The signal strength climbed for 36 seconds, peaked, and then faded for another 36 seconds. That's a perfect bell curve. It matches exactly how a fixed point in space would move across the telescope’s field of vision. This wasn't a satellite passing by. It wasn't a bird or a microwave in the breakroom. It was something out there, far beyond our atmosphere.
The frequency was the real kicker: 1420.4056 MHz.
To a physicist, that number is sacred. It’s the electromagnetic signature of neutral hydrogen. Since hydrogen is the most common element in the universe, scientists have long theorized that any intelligent species trying to say "hello" would use that specific frequency as a universal hailing channel. It's the galactic equivalent of 91.1 FM.
Why 6EQUJ5 is weirder than it looks
Most people see that string of characters and think it's a secret code. It's not. It was just the way the IBM 1130 computer translated signal intensity.
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- "1" was basically background noise.
- "9" was getting loud.
- "A" through "U" represented even higher intensities.
That "U" in the middle? That was the peak. It was more than 30 times louder than the deep space background noise. It was focused. Narrowband. It didn't smear across frequencies like a star or a nebula would. It looked manufactured.
Honestly, it looked like a laser beam of radio waves.
The mystery of the second beam
The Big Ear had two "horns" or feed antennas. Because of how they were set up, any real celestial source should have been detected twice—once by the first horn and then, a few minutes later, by the second.
The Wow! signal only showed up once.
This is the part that drives SETI researchers crazy. Did the signal turn off? Did the source move? If it was a continuous beacon from a distant planet, we should have seen it in both horns. The fact that it vanished before the second horn could sweep over it suggests something intermittent. A pulse. A "we are here" that didn't stay long.
Debunking the comet theory and other "rational" explanations
For decades, skeptics tried to pin the Wow! signal on everything from secret military hardware to reflections off space debris. In 2017, a researcher named Antonio Paris suggested that two specific comets (266P/Christensen and 396P/Gibbs) were in the neighborhood at the time. He argued their hydrogen clouds caused the blip.
The astronomy community basically tore that theory apart.
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Jerry Ehman himself pointed out that comets don't emit radio signals that strong or that narrow. Plus, the comets weren't in the exact right spot at the exact right time. It was a nice try, but the math just didn't hold up.
We're left with a few uncomfortable possibilities. It was a one-time glitch in the hardware (unlikely, given the perfect 72-second curve), a highly classified human broadcast we don't know about, or an actual extraterrestrial transmission.
The hunt for Tau Sagittarii
If you look at where the signal came from, there isn't much there. At least, not that we can see clearly. Recent deep-space surveys have identified a Sun-like star, 2MASS 19281982-2640123, in that region. It’s about 1,800 light-years away.
If there's a civilization there, and they sent that signal, they sent it during the decline of the Roman Empire. We're looking at ancient history in real-time.
SETI (Search for Extraterrestrial Intelligence) has gone back to that spot dozens of times. We’ve used the VLA in New Mexico. We’ve used the Green Bank Telescope. Total silence.
It’s like someone knocked on your door once in 1977, and you’ve been staring at the peephole ever since, waiting for them to do it again.
Moving beyond the "Wow!"
We've learned a lot since Ehman's red pen hit the paper. Today’s radio telescopes are infinitely more sensitive. Projects like Breakthrough Listen are scanning millions of frequencies at once, looking for another Wow! signal.
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But there’s a nuance here most people miss. We assume "they" are using radio. In the 70s, radio was our peak technology. Now? We use fiber optics and tight-beam lasers. Maybe the reason the signal never repeated is because it was a relic. An old technology they moved past while our ancestors were still figuring out the steam engine.
There is also the "Great Silence" or the Fermi Paradox. If the universe is teeming with life, why only 72 seconds?
Some researchers suggest the signal was "lensed." Gravity from a star or a black hole could have acted like a magnifying glass, briefly focusing a weak signal from a distant galaxy right onto Earth. If that’s the case, the signal might still be playing out there, but we’re no longer in the focal point. We just got lucky for one minute.
How to track the mystery yourself
You don't need a PhD to engage with this. The data from the Big Ear is public. Amateur radio enthusiasts still debate the signal's modulation patterns in forums every day.
If you're interested in the current state of the search, look into the work of Dr. Alberto Caballero. He’s one of the leading voices trying to narrow down which stars in the Sagittarius constellation are the most likely candidates for habitable planets.
The Wow! signal remains the best "Maybe" we have. It’s the ultimate reminder that we are looking at a very big ocean with a very small straw.
To stay informed on this specific anomaly, start by following the SETI Institute’s annual reports. They often revisit the coordinates with new hardware as it becomes available. You can also use sky-tracking apps to find the "Wow! origin" in the night sky during the summer months. It’s right near the "teapot" asterism in Sagittarius. Looking at that empty patch of dark sky makes the 72-second mystery feel much more real.
Investigate the "Technosignature" papers coming out of NASA’s exoplanet research divisions. They are moving away from just looking for "radio blips" and toward detecting atmospheric pollutants or massive structures around distant stars. The hunt has evolved, but it all started with a handwritten note on a piece of computer paper.
Keep an eye on the upcoming results from the Square Kilometre Array (SKA). When it's fully operational, it will have the sensitivity to pick up a signal like the one from 1977 even if it's much weaker. That’s our best shot at finally closing the case.