The Best Way to Find Aliens: Look for Their Solar Power Plants

Let's be realistic. A civilization so advanced as to be able to capture the entire energy of a star, probably also has energy alternatives, and probably wouldn't want to attract the attention of lesser beings (like us) by trapping a star's output in a detectable way.

>A civilization that built a Dyson Sphere would have to go to great lengths to avoid detection, either by getting rid of its waste heat in some novel way, or by building massive radiators that give off heat so cool that it would be undetectable against the cosmic microwave background, the faint afterglow of the Big Bang.

So if a civilization were to completely mask itself in the EM spectrum, the only way to detect them would be to look for gravitational distortions assuming those can't be masked. A civilization might do this either to hide from others or because the maximum efficiency of their energy extraction system would occur when their waste heat matched the background ration. So a really advanced (and paranoid or efficient) civilization would be indistinguishable from dark matter.

This brings up another interesting hypothesis: dark matter is actually the computronium of all of the alien civilizations in the universe that have achieved a technological singularity. Unfortunately, this hypothesis can't be tested until humanity gets to the same level.

It is not clear to me how that is a contradiction. An uploaded civilization may still desire more computational power, and unless there's an infinite computation escape hatch in physics (and there is currently not even a trace of such a thing), that's going to involve getting more energy from the star. On an exponential growth curve, even improving your civilization's energy efficiency by a factor of a hundred quadrillion still only buys you a blip on the scale on cosmic time scales before you start wanting to expand again.

>the sun beams a total of 120,000 terrawatts per day onto our planet. That's 10,000 times the amount that flows through our industrial civilization.

Should be "terrawatts", not "terrawatts per day". (I stopped reading there. There 100s of 1000s of people who know enough physics never to make such a mistake. I'll read one of them instead.)

Sure, they could have their own nuclear fusion reactors or even something more sophisticated, but why let a perfectly good source of energy just go to waste?

I don't think they'd care that anyone could detect them if they're that advanced...