An hour-and-a-half east of Redding, out past the cow pastures, is the tiny town of Hat Creek — population 266. It’s the perfect place to listen for transmissions from space. The mountains surrounding it block interference from human sources, which there aren’t many of out here.

“We are constantly searching the skies in order to find evidence of other life in the universe,” said Dr. Vishal Gajjar, a staff astronomer with the SETI Institute. “This is actually the only site in the world which is dedicated 24/7 to do this research.”
[pullquote size="medium" align="right" citation="Dr. Vishal Gajjar, staff astronomer, SETI Institute"]‘If you want to communicate across large interstellar distances, radio waves are the best possible way to do that.’[/pullquote]Forty-two giant white radio telescopes are positioned across a field. Each one is the size of a three-story building. They’re not like the cylindrical telescopes often used for stargazing. These look more like giant satellite dishes. They rotate together to face new sources in the sky. And when they do, they look almost like meerkats.

An machine that resembles a Christmas tree encased in glass in a room. — There is a log periodic antenna like this one inside each telescope. It converts radio waves into electrical signals. (Katherine Monahan/KQED)

Hidden inside the telescopes are specialized antennas that look like golden Christmas trees. Technically, they’re called log periodic antennas, which work to convert radio waves into electrical signals. Each of their golden branches is the length of the wavelength it is designed to receive.

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“If you want to communicate across large interstellar distances, radio waves are the best possible way to do that,” Gajjar said.

Radio waves have longer wavelengths than visible light, so they don’t get absorbed as easily and can travel farther through space. They’re also observable both day and night.

[aside postID="science_992707,science_1983602" label="Related Stories"]For now, the Allen Telescope Array is all about listening.

“We are not broadcasting,” Gajjar said. “We are a very new kid in this big jungle. So we shouldn’t start shouting; we should first listen to what’s out there.”

The input gathered by the telescopes runs underground through optical cables to a main lab, where it is processed and displayed on screens. Scientists monitor the display for the appearance of a streak running through it, indicating an intense radio signal.

If they have a temperature, all objects in the universe emit radio waves at some level. Stars emit them, and so do humans. But they’re usually pretty weak.

A large telescopic machine in a field. — A decommissioned telescope at the Hat Creek Radio Observatory. (Katherine Monahan/KQED)

Technological sources emit stronger signals. And that’s what Gajjar and his colleagues look for because it could indicate an extraterrestrial life form that’s intelligent enough to build machines.

“If we can detect it, we assume it would be an intentional communication,” said Grayce Brown, an associate researcher and observer at the Allen Telescope Array.

“I mean, when I first heard of it, I was like, ‘Aliens? What? There’s no way we’re doing real science on that,’” Brown said. “But people are seriously looking into it. And it blows my mind just how forward-thinking we can be and how plausible actually some of this stuff is.”

In the last decade, scientists observed thousands of new planets, which has ramped up the search for extraterrestrial intelligence.

“Almost every star you see at night has some planet around it,” Gajjar said. “And half of them have Earth-like planets within the habitable zone. So we are definitely not likely to be alone. There must be other life out there.”

Scientists have yet to find a clear signal of extraterrestrial intelligence, but Gajjar hopes they do within his lifetime.

“One day,” he said, “these telescopes might be contributing to the biggest discovery humanity has ever made.”

The Allen Telescope Array at the Hat Creek Radio Observatory is open to visitors on Thursdays and Fridays.

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