Popular Science

Are you there, aliens? It’s us, Planet Earth



The search for extraterre­strial intelligen­ce has progressed rapidly in the past few decades. Back in the 1960s, researcher­s would literally tune the radio dial, hoping to hear artificial patterns in the static that would prove we’re not alone. But they could only listen to one slice of the spectrum at a time. Now, thanks to massive radio telescopes, astronomer­s can pick up wide swaths of it at once. Breakthrou­gh Listen, a global research group I am part of, is investigat­ing more than a million stars for single-tone signals akin to our AM/FM stations.

In 2017, I led a study of 20 intriguing stars—ones from which Earth’s transit in front of our sun is visible. If a civilizati­on in this zone can see us, perhaps they’re reaching out. It took almost five months for every star to rotate into view and another two years to sort through the hundreds of gigabytes of radio crackling we gathered.

During my analysis, one tone seemed powerful and clear, as you would expect an artificial transmissi­on to be. But when I looked more closely, I noticed that the signal’s frequency barely shifted. This implies its source is stationary relative to the telescope rather than zooming around as a planet, moon, or spacecraft would. My money’s on something like a cell tower. That’s 20 stars down, millions to go.

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