[jjk166]

The facts don't change. Apples fell to the ground when we thought newtonian gravity was correct, they still fall to the ground now that general relativity is the accepted explanation. Theories are explanations of factual observations. The observation of the phenomenon we're calling dark matter is as factual as apples falling to the ground. The explanation is subject to change as we learn more, but the facts won't.

[bryanlarsen]

dotnet00 said we should call dark matter an "absolute fact".

[jjk166]

And I concur. It's as absolute a fact as earth having a core.