MigL

Americans, or about half of them, are their own worst enemies.

In GR, gravity is actually sourced by stress-energy-momentum. And as Studiot said, fields including the gravitational field itself, are a source.

Really ? AI and Quantum Computing have, so far, been worthless, and may never amount to much. Although Chinese strides in Fusion Reactor research is commendable. But when it comes to actual, useful research, like developing a successful mRNA vaccine in less than a year, as the Americans did, how did China and India make out ?

I don't know why you guys think this is funny. We are all old, and showing signs of Classical Testicular Extension.

A 'classical' Black Hole conserves three parameters; mass, angular momentum and charge. A semi-classical treatment ( with some QM considerations ) adds entropy ( see J Bekenstein ), and temperature. These properties are 'encoded' in the size/shape of the Event Horizon ( no other features are evident ), but mass/energy-momentum means it will curve space-time and exhibit gravity just like any other massive energetic body. The extreme conditions go even further and it will actually 'drag' space-time, rotating it with its angular momentum.

Why do all your questions seem like homework questions ? They are not general interest but relate to specific problems such as would be found in homework assignments.

Not a cosmologist, and I don't think you need be to offer an answer 🙂 . Hawking radiation depends on a mechanism facilitated by the Event Horizon. IOW, no Event Horizon >> no Hawking Radiation. Neutron stars have no Event Horizon, have a temperature and so produce regular radiation, and also directed gamma rays, because of the rapid rotation/strong magnetic fields. They are composed mostly of extremely dense, degenerate neutrons, and this degenerate pressure ( Pauli exclusion ) keeps them from further collapse. Electron degeneracy pressure keeps white dwarf stars from further collapse, but more massive stars can overcome this pressure and collapse to neutron stars supported by neutron degeneracy. When a star is massive enough such that even neutron degeneracy pressure cannot prevail against gravity, we know of no other mechanism to prevent further collapse. At the mathematical radius where escape velocity becomes equal to c , an Event Horizon is established by nature, and no further information can reach us regarding to the interior composition. The very equations that predict the gravitational collapse, become non-sensical and predict a singularity; an indication that those equations are no longer applicable in that domain. So, while we can say a neutron star is made of dense matter, we can't really say anything about what is inside the Event Horizon of a Black Hole with any certainty. We know a singularity makes no sense, but we know of no mechanism which will prevent any matter from collapsing to one.

This guy's channel ( Physics Explained - YouTube ) has some very interesting videos. He got his PhD at Queen Mary in London, and lectured at Liverpool, before recently quitting to pursue YT interests. Interestingly ( @studiot ), one of his videos relates to the empty space, or 'nothingness', within the atom, and what the fields of QFT tell us about it.

Geodesics continue through the event horizon. In free fall you are moving along a geodesic and experience no forces. Even partially crossing the EH ( assuming the BH is large enough that tidals are trivial ) you will experience no forces. If you are pulling a rope up against any gravitational field you are doing work and expending energy. In effect, you are keeping the rope from travelling along the geodesic and changing its momentum wrt time; the rope will feel a force.

That seems to be your problem; you don't understand stuff, so you make shit up. Are you following the MO of your President ?

Information, including cause and effect, travels at the finite speed of light. You cannot have the same 'now' as an event 1 light year away, for another year. You can always do the 'back calculation', but that is not the same thing. There is no global now. Even a local now is an approximation. Stop confusing yourself with your thought experiments. ( incidentally, pennies are binary, having two states, so binary notation is 2n, where n is the number of pennies. Anyone who grew up in the early days of computers knows about the address space relation to bit length )

Oh, now I understand what you were getting at ( Markus worded it more clearly 🙂 ). False vacuum states are necessarily unstable, and tend to decay, eventually reaching the ground state. Would it not be these fields that go on to infinity ( Space-Time Geometry or Gravitational field, Higgs Field, and possibly EM Field or Photon field ) ) that provide the global energy density ? The source/sink fields only provide a local energy density.

You are considering vibrational modes of 'surfaces'. String theory considers vibrational modes of 'strings', and has come up against a hard stop. Would your idea also require supersymmetry and describe a 'landscape' of universes ?

Current understanding, as per QFT, is that some fields permeate all space, even in the absence of the particles, charges, or energy-momentum, that were once thought to give rise to these fields. Even in totally empty space, these fields endow the vacuum with certain properties and an energy density. The energy of these fields gives rise to two conditions termed off-shell ( virtual particles with less than a quantum of action, that do not satisfy the energy-momentum relation ) and on-shell ( real particles with more than a quantum of action , that adhere to the energy-momentum relation ). The vacuum on either side of the Event Horizon of a Black Hole has some peculiar properties as well; it can turn off-shell particles into real ( Hawking Radiation ) by 'borrowing' mass-energy from the BH just outside the Event Horizon, and, turn off-shell particles into 'exotic matter', with negative energy, just inside the Event Horizon. The Higgs field has also added another scalar component to previous vector and tensor fields, again modifying our understanding of the properties of the vacuum. And these are just some of the properties I can think of, off the top of my head; there may be more. So, you can see the current understanding of the vacuum, what used to be simple empty space, has gotten fairly complex, and some, or all, of these properties need to be considered, depending on what you are attempting to model, or predict

When we had this conversation years ago, you were made to understand why there cannot be a common 'now'. None of us have changed our minds, but you seem to have gone back to your original misunderstanding. Obviously our 'nows' have diverged, and are not common anymore 😄.

Are you suggesting the vacuum has quantized states ? Please elaborate. No reason the ground state has to be in a vacuum, but an appropriate reason why the vacuum will tend to a ground state.

All systems tend to their ground state, and all 'excited' systems tend to decay. Least action principle. Try this video by an actual Physicist

What does that mean ?? You've been here long enough to know that there is no common now.

I'm confused; are CPU68 and CPU29000 the same person ? And, if so, what caused him to lose faith in Motorola processors of 40-50 years ago, in favor of AMD RISC processors of 30 years ago.

The unitarity condition of Quantum theory dictates that the time evolution of a quantum state, as per the Schrodinger equation, is represented by a unitary operator. This implies the total probability of all possible outcomes must always sum to 1, meaning probability is preserved in time, and information is conserved. Everything that goes into a Black hole is/has information; when the BH evaporates through Hawking Radiation, that information is randomized as thermal radiation, and the ability to follow the time evolution of the information vanishes. That is a problem/paradox according to Quantum theory

Space is a 'concept' to which we apply an ever changing ( as our understanding of its properties increases ) definition to. Bold move, re-opening a closed thread. I hope you bring more to the table this time around, or it will quickly follow the same fate.

Anyone can come up with WAGs. Provide a mechanism; then we can talk.

Way to go, INow 👍 Were you out there stumping ?

How do you know space-time curves ??? The model we have, GR, implies that curved space-time geometry ( a mathematical construct ) acts exactly the same as Gravity. If I have a map made of flexible material, and I pull up the area where a mountain is shown, it 'acts' the same as the real mountain. But the real mountain is not made of flexible material, nor is it 2dimensional, nor can you hold it in your hand, nor ...

This has already been answered by several members, myself included; pity you don't read, or understand, replies. At an early time ( before inflation ) the whole universe was in causal contact, which means information could be exchanged by all parts to establish isotropy and homogeneity throughout the universe. Symmetry breaks ( which would also lead to inflation as drops from false zero-point energy ) that resulted in Grand Unified Force breaking up into the current interactions, also established current global and gauge symmetries responsible for the laws we observe. This is current theory. Granted it doesn't explain the absence of magnetic monopoles at the 'edges' of symmetry break domains, nor does it point to insights about dark matter/dark energy, but it explain a lot of observations and makes quite a few valid predictions, so none of us are ready to discard current theory because you don't understand it and think it doesn't provide any 'answers'.