This 2025 image shows the largest single-dish radio telescope in the world: the Five-hundred-meter Spherical Aperture Telescope, or FAST. Fully completed in 2020, it surpassed the previous record-holder, Arecibo, which collapsed in December of that year. FAST now stands alone as the only radio telescope in its class, and if set to transmit a signal, would be the most powerful radio frequency transmitter on Earth. (Credit: SCJiang/Wikimedia Commons)

Ask Ethan: What should humanity’s message to the Universe be?

While we now actively listen for aliens, we’ve never made an intentional long-term broadcast ourselves. What signal should we ideally send?

Quick take:

• The search for extraterrestrial intelligence, or SETI, began more than 65 years ago with dedicates searches for radio signals with telltale signs of intelligent patterns behind them coming from the sky.
• In the time since, we not only have yet to hear from anyone, but we’ve come to an uncomfortable realization: that if we, with our current technology, were almost anywhere else in the galaxy, we couldn’t even detect ourselves.
• With that in mind, if we actually decided to make an effort towards being found by an intelligent alien civilization within our galaxy, what should we send and how should we send it? The message, the medium, and the method all matter tremendously.

One of the greatest open questions in all of the Universe today is just how abundant intelligent alien life is right at this very moment. We can imagine that extraterrestrial intelligence is common, and that the Milky Way is swarming with civilizations — thousands or even millions of them — just as intellectually advanced or even more…