22 upvotes, 1 direct replies (showing 1)
View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
On black holes: the "no-hair" theorem has not been proved generally for all possible black holes. Also, the "dumbbell" structure immediately post-merger is not a *stable* black hole solution - it will decay into a spinning BH, which will satisfy the no-hair theorem.
On the shape of the Universe: Yes, the curvature could be different than what we measure today. However: the trend would be to go *away* from flatness over time. That is, if the universe had just a bit of curvature early on, it should have quite a bit more curvature than that today (about 10^60 times more, I think?). Flipping that problem around, the fact that we measure the Universe to be flat today to within about 1% means the Universe had to be flat to within 10^-61 in the distant past. This is called the flatness problem[1].
1: https://en.wikipedia.org/wiki/Flatness_problem
The CMB: AFAIK those are most of your options. The one thing you're missing is the polarization of the CMB, which a number of experiments have looked at (most recently maybe POLARBEAR?). Other bands are unlikely to help you - the CMB we see is the peak of the spectrum from the Universe at the time, so it's by far the brightest band. Obviously nothing is *completely* opaque but... it's pretty dang opaque. Much easier to look at the ripples.
Comment by Cronerburger at 20/07/2022 at 20:25 UTC
0 upvotes, 1 direct replies
No hair means the black hole must be smooth? E.g. the shape of whatever fell in cannot be reconstructed back after it fell?
I realize the first question now sound dirty but wtv