Space/Science — HabitableZone

Space/Science » in reply to Keepin' it real

re: Keepin' it real
ER — (archived)

Actually, I understand quite a lot of thought has been given to this issue. The common wisdom seems to be that advanced civilizations would have the technology to keep all their deliberate, non-SETI signals on tight beams, in order to save energy. Broadcasting would never be used except as a hailing signal for SETI purposes. It would be very difficult to eavesdrop on ETI. The only exception would be in something like radar, where you are deliberately broadcasting in order to find something whose location is unknown, like a potential planet-crushing asteroid, or an enemy fleet.

There is another exception to this, massive engineering projects may release huge amounts of collateral energy, sort of like the sound produced by blasting operations at a construction site. The noise does nothing useful, it just is a characteristic result of using explosives. It isn't difficult to conceive of ETI engineering works producing signals detectable at long distances, and those signals would certainly not be optimized in any way for communications efficiency. In fact, they might appear as natural phenomena to our primitive astronomy. For example, some peculiar types of nova events might really be the signature of a black hole manufacturing facility.

This sort of artifact would very likely be visible at much greater distances to observers away from the galactic plane, as you point out. However, there are constraints on how big these events can be, or we would be detecting them in other galaxies.

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