3 ms·

This article predates a decent amount of research into Ultra-Diffuse galaxies: https://en.m.wikipedia.org/wiki/Ultra_diffuse_galaxy https://en.m.wikipedia.org/w

This article predates a decent amount of research into Ultra-Diffuse galaxies: https://en.m.wikipedia.org/wiki/Ultra_diffuse_galaxy https://en.m.wikipedia.org/wiki/Ultra_diffuse_galaxy. These curiously tend to either have way more or less dark matter than normal. And, dark matter just means matter that’s not visually observable, it doesn’t mean all dark matter is the exact same kind of thing, so it seems reasonable that Dyson spheres could present as dark matter. So I like to think that UDG galaxies are candidates for type2 civilizations or evidence of intergalactic resource extraction/technology that distorts the ratio of regular matter to dark matter, though most likely they’re observational quirks. A full list of justifications for them suggesting advanced civilizations: UDG galaxies have low levels of interstellar matter. A type 2 civilization would likely prefer to have all matter either generating/capturing energy or to be used for their own pursuits. UDG galaxies tend to be older. It seems reasonable that type 2 civilizations would be in older galaxies where they had lots of time to develop. Because of how dark matter works, it seems inexplicable for it to not cluster with regular matter at galactic scales/during the formation of a galaxy. Even weirder is that instead of a normal distribution or spectrum of regular matter to dark matter, almost every galaxy has it at a 1:5 ratio, except UDGs which are either at one extreme (~no dark matter) or another (1:90+ for https://en.m.wikipedia.org/wiki/Dragonfly_44 https://en.m.wikipedia.org/wiki/Dragonfly_44). This disequilibrium, similar to disequilibria on Earth, suggests life. But since this is occurring at galactic scale it suggests a galaxy spanning civilization. The existence of UDGs at both extremes could be explained by some process (that discriminates between regular and dark matter) by which matter is transferred between galaxies or even converted between the two forms. Whether this happens seems to be yes/no which at galactic scales seems explainable as “has an advanced civilization”. And perhaps in some cases this is due to a galaxy spanning civilization doing some kind of resource extraction from one to another. Finally, for UDGs with almost all matter being dark, this may represent an almost-complete conversion of the galaxy to a type 2 civilization. As expected, these are very rare because the time to convert a galaxy to this state should be very small compared to the beginning of the transition and end of it. This whole article rests on the notion that Dyson spheres will eliminate waste energy through black body radiation in a way that’s observable to us, but an advanced culture capable of building these things could likely think of workarounds. I mean, I’m sitting on my couch and I think you could probably figure out a way to direct this in a certain direction that would be invisible from most perspectives. And maybe whatever technology helps manipulate dark matter or convert between regular and dark matter would help you radiate dark matter instead of EM.

db48x 3y ago
While it’s true that not all dark matter has to be exactly the same thing, it’s also true that no large portion of it can be ordinary baryonic matter at low temperatures. What we know about dark matter is that it is weakly interacting, which means that it just doesn’t interact with ordinary matter and ordinary energy. This automatically rules out building a machine made of ordinary matter that creates or manipulates dark matter on any large scale. We might conceivably build a giant machine that _detects_ a particle or two of dark matter every year, but so far all our attempts have failed. Thus dark matter cannot just be a waste product of some advanced civilization, and even if it were you cannot just magic up a way to avoid creating waste heat.

db48x 3y ago

While it’s true that not all dark matter has to be exactly the same thing, it’s also true that no large portion of it can be ordinary baryonic matter at low temperatures. What we know about dark matter is that it is weakly interacting, which means that it just doesn’t interact with ordinary matter and ordinary energy. This automatically rules out building a machine made of ordinary matter that creates or manipulates dark matter on any large scale. We might conceivably build a giant machine that _detects_ a particle or two of dark matter every year, but so far all our attempts have failed. Thus dark matter cannot just be a waste product of some advanced civilization, and even if it were you cannot just magic up a way to avoid creating waste heat.