[spookthesunset]

So what is dark matter?

This thing that keeps galaxies bound that we cannot see but can only observe the effects… I think the hunt for it will push us into new territory.

That being said, as you say there has been nothing yet found that violates GR/QFT.

[nwallin]

The leading candidate for dark matter is that it's a soup of particles that interact gravitationally, but not via the electromagnic or strong nuclear force. If we're very, very lucky, it might interact via the weak nuclear force, which means there exists a slim theoretically possibility that we might be able to observe it interacting via the weak nuclear force. That being said, even if it does interact via the weak nuclear force, there's nothing to say it doesn't interact in a way which gives us the power to differentiate it from, say, neutrinos. And if it doesn't interact via the weak nuclear force, then we cannot every make any characterizations of it ever, not even with arbitrarily advanced technology.

If that's true we're hosed. There would be no insights, no way to theory ourselves out of it. Only nerds wailing futilely about dark matter on the internet. And sadness. And we wouldn't know it's because all our theories are correct, but we don't have the complete picture of the extra-Standard Model dark matter particles, or if it's because some variation of MOND is true, (although it's extremely unlikely to be a MOND variation) or if we're as wrong as epicycles vs curved fabric of spacetime.

[ravi-delia]

It seems like I'm more hopeful for a quantum explanation of relativity than you are, but it's still sort of disquieting to think that there could be any number of fields that we just couldn't ever properly interact with. Even with gravity rolled in, there could still be a field that just doesn't interact at all. Hell, there could be hundreds. Creepy.

[samus]

More likely, the symmetries that hide these fields would break down at energies that are way too high to ever reproduce in an accellerator or another lab experiment.

[eternityforest]

Wouldn't arbitrarily advanced technology be able to move it around with gravity or sense collections of it with some kind of LIGO but with gamma rays for even more precision or something?

Arbitrarily advanced is pretty strong in a world where some people think dyson sphere scale stuff could be real.

[ravi-delia]

You could characterize it gravity-wise, but we can already characterize it gravity-wise (sort of). We really only care about a field to the extent it can interact with other fields, and as of now gravity isn't really a quantum field, but a distinct thing. I think most people hope to eventually get relativity under the quantum umbrella, but we're nowhere near that yet. If relativity is just a description of the stage the other fields dance on, then we're just kinda screwed. We could determine the mass of the particle (assuming we could ever be confident in separate particles at all), but no other properties.