34 upvotes, 3 direct replies (showing 3)
View submission: Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science
I always hear about how black holes have no hair*, just 3 properties, mass, spin and charge. (While also being aware of other theories, like fuzzballs)
3 things about that stand out to me. When two black holes of 13 solar masses merge merge you get a dumbbell shape mass distribution before ringing down. It's not just a black hole of 20 sun's mass (assuming 6 or so lost to gravitational waves). It's different to how it will be in the future, when it will be a nice simple round spinning black hole, at the moment it is a weird construct with two seperate singularities and an entirely different shape? So is shape or mass distrobution a 4th quality? Next, as a black hole evaporates, it should send out higher and higher energy particles as hawking radiation, not just weak ass photons right? Eventually it will also be throwing out Z and W bosons and gluons? So would it not also have other properties relating to the strong and weak force?
And what's the deal with the higgs field not being 'a force'. Its a field that is giving a load of particles their mass right? So is it a field, one that's working inside of black holes? Does the matter in there then not necessarily also have that property, and then so too do black holes?
I keep hearing about how the curvature of the universe is flat (within a certain testable bound). Would increased amounts of matter and gravitational force have meant it was not flat? If so, did the previously higher amounts of radiation (photons and gravitational waves) which in early epochs exerted a greater gravitational influence before being redshifted and losing energy, would these have meant the universe was not in fact flat in earlier times? Did the universe then *become* flat or is the curvature of the universe independent of the matter and energy content of the universe?
What are the options for 'seeing' past the cmb? Neutrinos, gravitational waves, and shapes and patterns in the cmb, looking at how it is flowing towards, and redshifted by, matter beyond it which we cannot see. Any other options, and how much info are we getting from them? Last I heard it was a couple of neutrinos per week or something, nothing to really paint a picture? Are there any options I've missed, ones I am unaware of? And also, just how opaque was it? Is absolutely nothing able to be seen past the gas before recombination? Is there no frequency that was able to make it through a bit better?
Comment by kftrendy at 20/07/2022 at 18:04 UTC
21 upvotes, 1 direct replies
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 Aseyhe at 20/07/2022 at 19:30 UTC
7 upvotes, 0 direct replies
For seeing beyond the last scattering surface, here are some of the methods we already use.
Here are some more prospective methods (but this is a bit of a judgement call -- for all of these methods, absence of a detection can already constrain models of the early universe).
Comment by luckyluke193 at 20/07/2022 at 20:44 UTC
1 upvotes, 0 direct replies
And what's the deal with the higgs field not being 'a force'.
It's a different kind of object compared than typical "forces". The electromagnetic / photon field is a vector field – at each point in space (and time), it has a magnitude and a direction, like an arrow.
The strong and weak force fields are each just multiple vector fields in a trench coat.
The Higgs field isn't a vector field, but a scalar field. It has only magnitude, but not direction. In fluid dynamics, e.g. pressure is a scalar field – there are regions of high pressure or low pressure, but a "direction of pressure" makes no sense.