Ask Ethan: Could SETI detect a “twin” of Earth? | by Ethan Siegel | Starts With A Bang! | Jan, 2025

Earth is actively broadcasting and actively searching for intelligent civilizations. But could our technology even detect ourselves?

Someday, if nature is kind to us, we’ll make the grandest discovery of all: that we aren’t alone in the Universe. While various observatories and space missions might someday soon find life on other worlds, our ultimate ambition is even grander: to find another intelligent, technologically advanced civilization out there, to receive and listen to their signals, to send our own human-generated signals their way, and to establish two-way communication. If there’s anyone else out there within a reasonable distance to make contact with, it’s only a matter of time, technology, investment, and luck before our searches pay off.

But how far along on the path toward finding extraterrestrial intelligence are we, really? Could we even detect another civilization that’s operating and broadcast at the level that humans are currently at here on Earth? That’s the question of David Dempster, who asks:

“[What is the] distance at which we could detect ourselves? I would love it if you would consider this as a topic for an article.”