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An arXiv preprint suggests that evidence of intelligent (or trashy) life could be found by looking for space junk:
Its author, Héctor Socas-Navarro, spends most of his time at the Canary Islands Institute of Astrophysics in Spain studying the sun. But he was struck by a weird side effect of the ring of active and retired satellites circling Earth: it's a little bit opaque. And the more satellites we throw up there, the more opaque it gets. He realized that if we—or any technologically advanced aliens out there—build enough satellites, they'll eventually become dense enough to leave a faint shadow around the planet when it passes in front of a star.
And that's awfully convenient given that one of the best ways we have of spotting alien planets is by staring at their stars and waiting for tiny dips in brightness as planets pass in front of them. Essentially, Socas-Navarro's new paper proposes, if aliens have put enough satellites into orbit around their planet, we'll be able to spot the faintly opaque bubble before and after we spot the brightness dip of the planet itself.
The scale of the endeavor would be a real challenge for the aliens, however, since this idea relies on between 10 billion and one trillion satellites. "It's like building the pyramids," Avi Loeb, an astronomer at Harvard University, told New Scientist. "Each building block is easy, but putting it together is the hard engineering task."
(Score: 4, Insightful) by Grishnakh on Thursday March 08 2018, @11:10PM (1 child)
The radio modulation thing isn't *that* dumb; there's really only a few ways to modulate radio transmissions after all (amplitude and frequency being the main two). The problem is that as radio technology progresses, at least in our experience, it becomes lower-power and the modulation for more complex, making it look essentially like random noise from a distance. In short, if aliens were trying to detect *US* by our radio transmissions, they only had a relatively short window in which to do so, the time from when we first started seriously publicly broadcasting, up until we moved to digital spread-spectrum schemes. If they tried to detect us by our emanations today, they most likely wouldn't notice us. And if our technology progression is typical, that means that we're very unlikely to detect anyone who's at least as advanced as us; we'd only be able to detect them if their earlier signals (from when they were as advanced as us in the 1950s-60s) happen to hit our antennae when we were listening. It doesn't help that even those higher-power transmissions are likely to be very difficult to detect over such a distance, since they weren't meant to be detected by far-away aliens, but only used terrestrially.
Basically, SETI would make more sense if there were some aliens out there intentionally broadcasting very strong radio signals with the goal of being detected by us. That's not a great assumption.
(Score: 2) by Immerman on Friday March 09 2018, @02:31AM
What about polarization - either linear or radial?
But yeah, even that only pushes it up to possible modulations... though I honestly don't know if anyone is seriously looking at polarization at all. Heck, for all I know the interstellar medium might destroy polarization, which could actually be an advantage for a security- or obscurity-minded species.