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Van-der-Waals forces and gravitation are the main answer. The main property keeping together bodies smaller than a few $100 {\rm km}$ are their constituents surface forces between the grains (van-der-Waals) and chemical/ molecular bonding within the grains themselves. It's the same mechanic which makes the dust and grease in your flat stick to surfaces and ...

9

The answer is reasonably simple: (nearly) all matter consists of protons, neutrons and electrons, thus of either positively, or negatively charged particles or those with no charge. The next step you need to make is to assume that for some reason whatsoever a black hole accretes more protons than electrons (or vice versa). Such process might be envisionable, ...

7

Why do some call the no-hair conjecture the no-hair theorem? Perhaps they mean something specific, or perhaps they don't know any better... you'd have to examine it on a case-by-case basis. Perhaps a better question is: are there reasons why someone would be motivated to say theorem instead of conjecture? Sometimes people call unproven mathematical ...

6

No. The universe is not a sphere with water ice surrounding it. Asking about "outside the universe" is akin to asking about what a candle flame is made of before it is lit. Just because you can put the words together doesn't mean the question makes sense. The universe is "all that exists". Nothing can exist outside the universe, because then it would ...

5

Formally, black holes are a prediction of Einstein's theory of gravity. They have been observationally confirmed. Regarding theory: The field equations of Einsteinian gravity, the Einstein Field Equations, admit solutions. The first closed form solution of these equations was found in 1916 by Karl Schwarzschild which is the massive non-rotating, uncharged ...

3

ds refers to a distance in spacetime (this includes time). Just as, in classical physics, you see $$ds^2=dx^2+dy^2+dz^2$$ for any given line element, in spacetime you get similar things going on. For flat spacetime, this gives some good intuitive understanding. Depending on your signature, an element in flat (Minkowski) spacetime is ds^2=dt^2-dx^2-dy^2-dz^...

3

From the no-hair theorem, black holes can have only three properties: mass, angular momentum, and electric charge. From this we'll see the original, supermassive black hole gain the mass, angular momentum and electric charge of the ingoing star. The black holes will merge (already merged actually, since one is inside the other). The singularities will merge ...

3

Your scheme of creating energy from the tidal forces in a pair of orbiting planets cannot work because of the law of conservation of energy (aka the 1st law of thermodynamics), which states that energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another. It takes energy to set the 2 planets in ...

2

This diagram from the Wikipedia article on supernovas mostly answers your question I think. There is in fact an interval that is expected to not produce a remnant, but it is not at the lower end of the mass range, interestingly. Instead it's a result of the particular mechanism that triggers the supernova for these heavy stars, which blows the core apart ...

1

tl;dr Size plays a role in this very specific scenario in kind of an indirect way, but generally speaking, variability in its enormous scope depends on a lot of other things more for other kinds of objects, and this is not a relation to be applied outside of maybe pulsars (probably) Let me know if some of these assumptions I’m making here are wrong, but I’m ...

1

As @PeterErwin's comment compassionately points out: "Acceleration" means changing the velocity vector, so an object in a circular orbit is always "accelerating" (because the direction of the velocity changes), even if its speed is constant.

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You answered your question actually. You have said Note that this solution is not valid for domination of the cosmological constant, which corresponds to an w=−1 then you are saying But if 'w' is negative-one then 'a' is proportional to tt The $w=-1$ does not apply to $a(t) \propto t^{2/3(1+w)}$

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It's very difficult to answer a question "Are there any theories ...." in the negative, since if nothing else, the questioner has probably just formulated such a theory. I can say with reasonable confidence that no such theory has any traction or credibility in any of the communities of research and scholarship that consider such things (astronomy, cosmology,...

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