[AnimalMuppet]

Aliens collecting all the light/electromagnetic radiation from stars would be an interesting way to get dark matter. That's one place it could fit.

And, if our theories are right, we're at 4.9% regular matter and 26.8% dark matter, so dark matter is five times as much as regular matter, so that's a lot of aliens...

[bhickey]

What you're suggesting doesn't make sense.

Dark matter isn't non-luminous matter. It's matter that only interacts gravitationally, but not electromagnetically. This means it doesn't undergo collisions and can't shed angular momentum. It forms a diffuse, largely uniform cloud throughout galaxies. The result is that galaxies are more dense further from the galactic core than we would predict from luminous matter alone.

[bhickey]

> Dark matter isn't non-luminous matter.

What I meant to write is—

> Dark matter isn't merely non-luminous matter.

[bqmjjx0kac]

I'm speaking outside my area, but dark matter is not really confirmed to even exist?

[tsimionescu]

It's clearly confirmed that galaxies don't obey the known laws of quantum electrodynamics (QED) + general relativity (GR) if we assume they are made entirely of Standard Model particles. So, either QED is wrong (extremely unlikely) or GR is wrong (unlikely) or there is some matter that is not in the Standard Model (plausible).

Dark matter corresponds to option 3 - and there are observations that conform some models of dark matter distribution that match quite well between different galaxies. There are other theories as well, such as MOND (modified Newtonian gravity) that explore option 2 (GR is wrong).

Still, whatever the theory, it's clear that what is not happening is "aliens someone consuming all of the EM radiation from some stars". With anything resembling currently known physics, it's impossible to "consume" EM radiation in this way. Electric charge is always conserved, electrons and quarks don't disappear just because they move around, even with something like controlled fusion. A Dyson sphere would be an extremely hot visible object, not some dark point.

[ben_w]

> So, either QED is wrong (extremely unlikely) or GR is wrong (unlikely)

Not my area, but I thought both were known to be incomplete? Q because it presumes a flat spacetime; R because it predicts the formation of singularities that the maths used to develop it assume don't exist?

[tsimionescu]

I think the general belief is that it will turn out that space time is actually approximately flat at small levels, so that QED will be essentially exactly correct, while GR will turn out not to apply past a certain small scale.

[FrustratedMonky]

Wasn't the term 'dark matter' just meant to indicate 'unknown'.

It wasn't meant to be descriptive, just that there is a gap between theories.

And one theory is there is some 'unknown' type of matter, and they called it dark.

[bhickey]

No. 'Dark' comes from 'dunkle' in German. It refers to non-luminous matter.

[throwuwu]

What if they’re really greedy about energy and store everything they can in superconductors?

[tsimionescu]

Superconductors still have an EM signature, they still have magnetic fields around them and are detectable.

[bhickey]

It's consistent with observational evidence. You are correct that no one has detected dark matter particles.

[revscat]

https://youtu.be/nbE8B7zggUg?si=QcBpuxSvXsGGxTKk