Recent content by xantox

Yes, but the problem is that it is not even a necessary condition. A countably infinite universe can be exhaustive, too.

I believe the same. Note that you said in your first message "If the Universe is infinite, it may only be "countably" infinite". Anyway, it is possible to map to naturals all permutations of state at finite temperature of any causally connected patch of the universe (observable universe). That...

Yes, but how "exhaustivity" is defined here? The set of all real numbers does contain all real numbers. But it does not contain complex numbers. Is it "exhaustive" then? To define exhaustivity we should also define the space of states. If it is the integers, then the set of all integers is...

An uncountably infinite set is also not necessarily "exhaustive", eg it could also not contain "3". Instead of assuming that physicists don't know about set theory, consider that they may take into account the additional constraints of the full physical theories – this must be the case when...

J. B. Hartle, “Gravity: An Introduction to Einstein’s General Relativity“, Addison Wesley (2002).

It is a speculation at least consistent with general relativity. A well known model of "self-creating" inflationary universe has been proposed by J. R. Gott and L-X. Li, "Can the Universe Create Itself?", Phys. Rev. D 58, (1998).

* E. F. Taylor, J. A. Wheeler, “Spacetime Physics“, W. H. Freeman (2nd edition, 1992). * A. P. French, “Special Relativity“, W. W. Norton & Company (1968). * W. Rindler, “Introduction to Special Relativity“, Oxford University Press (2nd ed. 1991).

It is not known if the universe is finite or infinite. Observations combined to current models allow both cases. If the universe is finite, then it started finite at the big-bang. If the universe is infinite, then it started infinite at the big-bang (meaning infinite 3-dimensional space).

There are various proposals in quantum gravity research considering that quantum effects could replace standard black hole singularities by bounces, causing geodesics to diverge again past the avoided singularity into another region of spacetime and behaving like a cosmological big-bang. In that...

If we talk about the tidal tensor then it's the same for the free-falling and the hovering observers. However if we talk about stresses felt by the body, then we have: free falling observer: weight is zero, tidal forces are small enough for high enough radius. hovering observer: weight...

That is only the case for free-falling bodies crossing the horizon, certainly not for hovering bodies. Since their proper acceleration diverges over a finite distance, the acceleration gradient shall also diverge near the horizon – for black holes of any mass.

It's also the tides, as they also diverge in the limit of the horizon for hovering bodies.

For two identical static black holes, the rigorous theoretical upper limit is the Hawking bound of (2-√2)m (eg 29% of the initial total mass). Numerical simulations typically show much lower amounts of radiation on the order of 0.1..4% (and up to 14% in the scattering regime).

The propagation speed of the signal (which propagates outside the conductor) is practically the speed of light in the material outside the conductor. This is about 0.91c for polystyrene, 0.69c for teflon, and c for air.

If the body undergoing collapse is rotating too fast in the first place (eg above the Kerr limit), then it will not collapse into a black hole. If it collapses, the only externally observable property describing its rotation is the angular momentum, which is a conserved quantity (it can increase...