That's the shit I hate about modern cosmology - we can only observe shit down to specific levels and even then, it's not with complete understanding. Instead of saying we don't know, we get "well here's theory that has been matched to our mathematical abstractions with zero evidence." This also goes light speed in the opposite direction, where for nearly a century, we have "well our observations of galaxy rotations have blown gravity based theory out of the water, so uhhh here's dark matter which by definition can't be observed, to fix the problem. Please send more grants, thanks."