[awinter-py]

> we can map dark matter's location

this has always felt circular to me -- someone drops an astronomy paper like 'we found a galaxy with no dark matter' and I wish someone would rewrite it as 'dear non physicist, here are ten critical takes you just thought of and why we discarded each'

this is mostly a knock on my own knowledge, and slightly a knock on pop science press, but I don't know the steps between 'mass as inferred from light doesn't explain galactic rotation curves' and '80% of mass is ghosts'

[consilient]

> but I don't know the steps between 'mass as inferred from light doesn't explain galactic rotation curves' and '80% of mass is ghosts'

This is the root of the disconnect, I think: dark matter isn't ghosts. Or if you're feeling snarky: all matter is ghosts. Any talk of "substances" or "essences" or "intrinsic properties" is entirely outside the scope of physics: the only things we ever see are interactions, and interactions with light don't have any special epistemic status that interactions with gravity lack. If anything, the opposite is true.

[FreeFull]

There are observations that point towards dark matter which don't have anything to do with rotation curves. In particular, gravitational lensing, and the effects of mass on the cosmic microwave background. https://en.wikipedia.org/wiki/Bullet_Cluster The Bullet Cluster is very hard to explain with any kind of MOND theory.

[awinter-py]

the bullet cluster is like 'two clusters collided in the visual plane, and now the lensing peaks are correlated with the respective centers of luminosity'

unless I'm missing something, this is mysterious in the exact same way as normal galaxies