Gravitational time dilation would seem to prevent anything from reaching the Schwarzchild radius. It seems to me that the calculation of properties of General Relativity would be similar to the Gausian calculation that asymptotes but never reaches unity (x axis). In other words, time dilation would approach 0 but never reach it. As mass approaches the Schwarzchild radius, spaghettification would stretch and rip apart everything from a human body to cells to molecules to atoms to hadrons and even quarks. Thus as the S surface is approached, matter becomes some sort of essence, nothing like particulate matter. Please, someone tell me if my thought process is somehow wrong in assuming that nothing could ever reach, much less pass, the Schwarzchild radius/surface. Note that although dimensions may change, it seems this view seems to apply to a Kerr, (spinning} black hole as well. An additional thought regarding spinners, it seems the tug of war between centrifugal and centripetal forces would use energy that would shrink the hole, as happens during LIGO events as binary black holes spin down.
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2Does this answer your question? How can classical black holes even exist? – StephenG - Help Ukraine Apr 20 '23 at 20:52
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2it is easily derived that an object takes finite time not just to fall past the event horizon, but onwards into the singularity. And there can be black holes big enough that the spaghettification happens after the event horizon. Finally, coördinates exist whereby the event horizon has no singularity – naturallyInconsistent Apr 20 '23 at 21:17
2 Answers
First, remember that before there was a black hole, there was a star that collapsed into itself. John Wheeler, (who coined the term black hole) said that an imploding star converts its protons and neutrons into radiation during black hole formation. So now we are thinking along the lines of quarks and gluons. We know from the Pauli exclusion principle that spin 1/2 particles such as quarks cannot simultaneously occupy the same quantum state, so if there is a singularity at the centre, it can't be made of quarks. But spin 1 particles such as gluons can occupy the same quantum state without limit, so it is possible that a star's worth of gluons remains at the centre.
Carlo Rovelli (one of the key figures in Loop Quantum Gravity) has speculated that there is a Planck star in the centre of a black hole, so not a singularity but just a really small, compact mass.
However, for your general question about if time dilation prevents anything from penetrating the SR, there are many physicists who believe that there is nothing inside the event horizon; that it is just a hollow shell because time dilation stops any further movement towards the centre.
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How could anything ever pass into, much less through, the SR during star collapse? Matter would have to move backward in time. I imagine the 'vacuum' inside the SR expands as matter in the matter essence surrounding that shell expands. – Cap Munday Apr 20 '23 at 22:26
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Take a look at this link on planck stars https://en.wikipedia.org/wiki/Planck_star#:~:text=Carlo%20Rovelli%20and%20Francesca%20Vidotto,the%20black%20hole%20information%20paradox. In brief, this is what forms during the collapse of the original star. (Sorry that I called it a quark star in my original answer. I've corrected that now.) So his total theory might not be correct, but it supplies an interesting thought on what happens to the original star. – foolishmuse Apr 20 '23 at 22:43
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1@CapMunday Keep in mind that there is no event horizon for a large star. No matter how far we go inside, we can always escape the gravity well (the neutrinos for sure do, this has been measured). While the density of the center increases, there is a point in time when an actual event horizon forms, which traps all the matter that is already within its finite radius. – FlatterMann Apr 20 '23 at 22:44
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The event horizon is the surface at which escape velocity exceeds light speed. Matter (eg. neutrinos) cannot exceed light speed, therefore what ever descends into a 'gravity well'/black hole, cannot escape in the form of matter. However, energy can escape as it does during LIGO events. Stars have no event horizon. Black holes do. – Cap Munday Apr 22 '23 at 13:47
That is why it is called an "Event" horizon: to come back out, you need to travel into your backwards like cone. Increasing your radial coordinate is like traveling to yesterday: the direction is not available.
It's well known that a free falling observer crosses the event horizon....un-eventfully. That a distance observer can never see it happen is not a problem.
Regrading centrifugal force: that is just no going to work in Kerr spacetime. There is a radius at which the force points inward; there are vortex lines forcing you to differentially rotate, and there is frame dragging which entrains you to move with the black hole, just to be "at rest".
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It is not well known that crossing the event horizon is uneventful. The gravitational gradient shrinks as the SR is approached as predicted by General Relativity. Depending on the radius of the event horizon the rate of gradient shrinkage changes. Going from a difference over one meter of 10 g to 1,000 g to 100,000 g will tend to rip things apart. Frame dragging effects mass outside the black hole, not the surface. Black hole mass is related not to volume, but to surface area. – Cap Munday Apr 20 '23 at 22:49