How Does Matter Leave a White Hole?

[Pittman]

Now this is my first post here but I've been a reader for some time. Now I have a basic understanding of physics and GR and love to read about cosmology and debate it with different people but I've come up with a few questions that I've been having a hard time to find the answer or understand and I hope someone here can help me.

Now the question is about white holes, now I know that it is supposed to be a reversal of a black hole and more than likely do not exist. Now the debate that I'm in is about Humphreys's White Hole cosmology, now my question is this? Who does matter leave the event horizon of a white hole? Now as I understand it a white hole will still have gravity that will pull things towards it and will have an event horizon that will require an escape velocity of greater than C. Now as far as I've read the white hole doesn't have a reverse of gravity where it pushes instead of pulls, so if the white hole still has normal gravity then how does matter escape the matter sphere of the white hole?

I hope I have made myself clear on the question and thank you for any help.

 

[Chalnoth]

Now this is my first post here but I've been a reader for some time. Now I have a basic understanding of physics and GR and love to read about cosmology and debate it with different people but I've come up with a few questions that I've been having a hard time to find the answer or understand and I hope someone here can help me.

Now the question is about white holes, now I know that it is supposed to be a reversal of a black hole and more than likely do not exist. Now the debate that I'm in is about Humphreys's White Hole cosmology, now my question is this? Who does matter leave the event horizon of a white hole? Now as I understand it a white hole will still have gravity that will pull things towards it and will have an event horizon that will require an escape velocity of greater than C. Now as far as I've read the white hole doesn't have a reverse of gravity where it pushes instead of pulls, so if the white hole still has normal gravity then how does matter escape the matter sphere of the white hole?

I hope I have made myself clear on the question and thank you for any help.

General Relativity is time-invariant. That is, any system you can produce can be described accurately by General Relativity working forward in time or backward in time.

A black hole is an object which forms from the collapse of a dead star, grows by steady accumulation of matter, typically from an accretion disk that forms around it, and then slowly evaporates into radiation until nothing remains.

So a white hole would be the time inverse: a bunch of radiation that all collects in a single point, forming the white hole, which, after a great deal of time has passed, starts spitting out a bunch of light and matter until it is no more.

A white hole, basically, is a contradiction in terms: the process of a black hole's evolution is a continual increase in entropy. A white hole's evolution is a continual decrease in entropy. So a white hole is what happens when somebody got the arrow of time wrong in their equations.

 

[Pittman]

General Relativity is time-invariant. That is, any system you can produce can be described accurately by General Relativity working forward in time or backward in time.

A black hole is an object which forms from the collapse of a dead star, grows by steady accumulation of matter, typically from an accretion disk that forms around it, and then slowly evaporates into radiation until nothing remains.

So a white hole would be the time inverse: a bunch of radiation that all collects in a single point, forming the white hole, which, after a great deal of time has passed, starts spitting out a bunch of light and matter until it is no more.

A white hole, basically, is a contradiction in terms: the process of a black hole's evolution is a continual increase in entropy. A white hole's evolution is a continual decrease in entropy. So a white hole is what happens when somebody got the arrow of time wrong in their equations.

Thank you for your post.

So by changing the value of time to go backward instead of forward would this change how the event horizon of the white hole would work? What I mean is that, as I understand it, the event horizon is caused by the gravitational pull of the black hole so by switching the value of time would that mean that gravity is working "backwards" as well?

 

[Chalnoth]

Thank you for your post.

So by changing the value of time to go backward instead of forward would this change how the event horizon of the white hole would work? What I mean is that, as I understand it, the event horizon is caused by the gravitational pull of the black hole so by switching the value of time would that mean that gravity is working "backwards" as well?

Well, it'd mean just as much to do that as it would to switch the time coordinate so that we see eggs unscramble, or trees turn back into seeds. It's not something that we can physically do, it just means we got the direction of time wrong.

 

[Pittman]

So if Earth was to get sucked into a black hole thus crushed then you switch the time the Earth would then "pop" out of the white hole or just the matter?

So if I understand this correctly that the event horizon is still there, there still is a gravity well but since time is going backward nothing is falling toward the white hole? It would be just like playing a video backwards, that the white hole is actually not something new but just a black hole on rewind?

 

[Chalnoth]

So if Earth was to get sucked into a black hole thus crushed then you switch the time the Earth would then "pop" out of the white hole or just the matter?

So if I understand this correctly that the event horizon is still there, there still is a gravity well but since time is going backward nothing is falling toward the white hole? It would be just like playing a video backwards, that the white hole is actually not something new but just a black hole on rewind?

Yes, exactly, it's playing the video backwards. This is why I say a white hole is unphysical: it means you got the time coordinate wrong, which is akin to playing a video backwards.

 

[petm1]

I would think matter leaves a white hole as energy, and in our "now" I would think that the white and black whole associated with big bang are the horizons we exist between.

 

[financeguy]

Not sure if the backwards running movie is a good analogy. Consider a video of a ball thrown in a parabolic arc. One would see the same trajectory whether the video were run forwards or backwards; gravity points in the same direction whether one is going forwards or backwards in time.

If there is a ER Bridge, I cannot help but think it would connect two black holes.

But if on the outside chance that there were white holes, I wonder what the implications are for Hawking Radiation. Would we have Hawking Condensation? (Please don't pounce too hard on that; it's just a musing. I still put a low probability on the existence of WHs).

 

[Pittman]

Not sure if the backwards running movie is a good analogy. Consider a video of a ball thrown in a parabolic arc. One would see the same trajectory whether the video were run forwards or backwards; gravity points in the same direction whether one is going forwards or backwards in time.

If there is a ER Bridge, I cannot help but think it would connect two black holes.

But if on the outside chance that there were white holes, I wonder what the implications are for Hawking Radiation. Would we have Hawking Condensation? (Please don't pounce too hard on that; it's just a musing. I still put a low probability on the existence of WHs).

From my understanding the Hawking radiation would make it so that a white hole doesn't form.

 

[Chalnoth]

From my understanding the Hawking radiation would make it so that a white hole doesn't form.

No, actually, the Hawking radiation itself forms the white hole.

 

[Chalnoth]

Not sure if the backwards running movie is a good analogy. Consider a video of a ball thrown in a parabolic arc. One would see the same trajectory whether the video were run forwards or backwards; gravity points in the same direction whether one is going forwards or backwards in time.

If there is a ER Bridge, I cannot help but think it would connect two black holes.

But if on the outside chance that there were white holes, I wonder what the implications are for Hawking Radiation. Would we have Hawking Condensation? (Please don't pounce too hard on that; it's just a musing. I still put a low probability on the existence of WHs).

The video analogy absolutely correct. This is precisely what a white hole is: it is a black hole with the time coordinate reversed. It is a valid solution to the equations of General Relativity (since those equations are time-invariant), but it has the problem of, unlike a black hole, ever-decreasing entropy.

The difference with respect to the thrown ball is that the thrown ball is a system with very little change in entropy (there is a bit of energy loss due to air friction, but not that much). It is more akin to, say, a person jumping off of a diving board into a pool. In forward motion, the person leaps off the diving board, lands in the water, where they are slowed dramatically by the water molecules being pushed out of the way.

The reverse is all of those water molecules hitting his body just right so that he is propelled out of the water and onto the diving board, where he stops his motion with his legs.

By the way, the fact of time reversal invariance is a fact of all of the fundamental laws of nature of which we are aware. The irreversibility of the macroscopic world doesn't stem from those fundamental laws, but instead from a low-entropy boundary condition in the early universe.