E.T. isn't phoning home, but sailing aliens might have generated bursts of radio activity.
Researchers at Harvard and the Harvard-Smithsonian Center for Astrophysics are investigating whether fast radio bursts — radio emissions from unidentified sources in space that are very strong and last less than five milliseconds — emanate from "extragalactic civilizations."
So if there are in fact aliens generating spurts of radio activity from a structure with twice the diameter of the Earth, as the research proposes, the question remains: Why?
The researchers first note that there is a possibility they are broadcasting beacons to inform of their presence, whether it's a cry for help or a way to tout their technological achievements. But this explanation is "rather implausible" due to how much energy needs to be expended to send the fast radio bursts, so the researchers explore an alternate explanation — that these extragalactic beings are using FRBs to power light sails.
As fascinating as the prospect of aliens sending blasts of radio activity to power spaceships is, the researchers note that this possibility is "more speculative than an astrophysical origin." But they still think it's important to collect quantifiable data for, "at the very least, the important purpose of enabling astronomers to rule it out with future data."