White hole

Honorable_Death

If a black hole creates a dent in spactime, would a whitehole creat a lump, and if it did would it be in the future?

JesseM

You're taking the "rubber sheet" analogy too literally. You shouldn't imagine things being pulled "down" on the rubber sheet, all that matters is that they take the shortest path between two points, known as a geodesic. For example, the shortest path between two points on the curved 2D surface of a sphere would be the section of the great circle that passed through those points. In general relativity geodesics are not actually the shortest paths through curved 3D space, they are the paths through curved 4D spacetime with the largest proper time (proper time is the amount of time registered on a clock that that follows a given path through spacetime). So the rubber sheet analogy only gives a vague idea of how general relativity explains things, you shouldn't take it too seriously.

PeteSF

I think that a white-hole is a solution to the GRT field equations that is the same as a black-hole solution but with the time reversed.

Both have a singularity in the middle, cloaked by an Event Horizon.
Anything can enter a black hole, but nothing can escape.
Anything could escape a white hole, but nothing could enter.
A black hole is formed when enough mass-energy is concentrated in a small enough space.
A white hole might "die" if enough mass-energy escaped at once? (I'm speculating on this - I wouldn't have a clue how to begin to approach the maths)

A black hole "dies" when the event horizon evaporates with a huge burst of radiation.
I don't know if there is any mechanism postulated for the formation of a white-hole event-horizon.

One kooky idea that I came up with (then promptly found that it wasn't original after all) is that the view from inside a large enough white hole could conceivably look much like our Universe...

ohwilleke

PeteSF. You're not far off. Loop Quantum Gravity people like Smolin would argue that the Big Bang is THE white hole in our universe and that every black hole creates a new "baby universe" with its own white hole/big bang which is the interior of the black hole.

JesseM

The "black holes create baby universes" is a hypothesis favored by Lee Smolin, but can it be shown to be a consequence of loop quantum gravity?

Honorable_Death

when i used the hole dent and lump analogy i wasnt literally talking bout a dent and lump in our universe, im talking about how a black hole is going "back in time" because its so massice, or the dent, well what im really asking is would a white hole go froward in time

neurocomp2003

if i remmeber correctly A white hole isn't stable...people coming outta the singular are trapped.

JesseM

What do you mean when you say a black hole is going "back in time"? Time slows down close to a black hole (or any other object), meaning that if you spend some time near a black hole and then return to earth you'll have aged less than everyone else, but you can't go backwards in time by hanging out near a black hole. Time wouldn't speed up near a white hole, if that's what you're asking.

Honorable_Death

y wouldnt time speed up next to a white hole?

JesseM

A white hole is just a time-reversed version of a black hole--if you filmed a black hole and played the film backwards, that's pretty much what a white hole should look like. If you see a clock ticking slower near a black hole in your movie, then playing it backwards, the clock will still be ticking slower.

PeteSF

That's interesting... so a white hole is still a deep gravity well?


Thinking...

What would happen to an object that fell toward a white hole from some distance?

Spin_Network

So..a Star collapse that create's a Blackhole, is the Time-reversed of a White hole?..thus Stars 'ARE' white holes?..so I look out into the night sky I am seeing White Holes embedded in universal a Dark Hole?..are you sure about those time-reversed implications?

If I film a Star collapsing in a 'forward' time, and a Blackhole appears..the event-horizon is external to the Blackhole singularity..it is the last remaining remnant signiture, but then if I Rewind 'backwards' in time, "from the event-horizon" to the 'COMPLETE', uncollapsed star which is the time-reversed scenario that you imply, then the 'locked-up' information that was lost to the Blackhole would have to be EXTRACTED in order to complete the construction of the physical Star!

I think you should try to understand the dynamical implications of what your stating?..the time ordering of Whitehole<>Blackhole and Blackhole><Whitehole is where the problems lay, the TIME horizon is not connected to the Singularity Horizon, events of Time in one collapse (Stellar collapse) for instance, do not allow EVENTS to be frozen, the ticks you are talking about "follow=through" and cannot be observed from an external observation reference frame, thus from an observational point of view the Star dissapears and a Blackhole appears, they cannot..I repeat..cannot be reconstructed without ALL the paramiters one started from, thus the TIME-PARAMITER cannot be re-constituted from "Stellar" created Blackholes, its a one-way dynamical operation.

Trying to create 'events' at the limit of collapse is trying to stabilize the collapse into time orderings where past-present-future are overlapping and do not really 'exist', to do this one has to find the Universal Singularity Event.

There are recent implications for "time-reversed" equations that are being reformulated by some of the worlds top-heads, the 'information_paradox' that leads to white-hole, black-hole paradoxes, are being bent..strightened..and un-warped by leading theorists today, there is a growing consensus that Science had taken the wrong road (would not be the first time!)..in not the overall theory, but just the understanding Einsteins Generalized Field Equations.

JesseM

Good question, but I don't know, maybe one of the GR experts here could answer that question. I suppose this must be analogous to the question, "if you see an object near the event horizon of a black hole but flying away from it, what would you 'retrodict' for that object's past history?" Maybe the only way to explain it would be to suppose that it interacted with another object in such a way that its trajectory was altered, like if it was originally riding along with a rocket falling into the black hole but the people on board shot it away before they crossed the horizon. If that's correct, then it seems the answer to the question of what would happen to an object falling into a white hole would be that some object coming out of the white hole will always interact with it in such a way that it is deflected away from the horizon. This seems pretty strange, but then if a white hole is exactly like a time-reversed black hole we should expect the thermodynamic arrow of time to go in reverse in its vicinity, leading to all sorts of strange events. So maybe that means that white holes fall into the same category as phenomena like pieces of broken eggshell spontaneously jumping together and forming an intact egg--allowed by the fundamental laws of physics, but terrifically unlikely due to the second law of thermodynamics.

JesseM

No, a star collapsing would not look like the time-reverse of a black hole forming, a star collapsing is a black hole forming if the mass is large enough. A reversed collapse would look like a black hole spewing out matter until it becomes a star (or some other dense collection of matter/energy). Yes, as I said in my post to PeteSF, I think a white hole would involve a huge violation of the second law of thermodynamics, which is probably why physicists don't think they're likely to exist in spite of being a perfectly valid solution to the time-symmetric equations of GR (this page mentions that "White holes cannot exist, since they violate the second law of thermodynamics.") Similarly, the time-symmetric laws of quantum mechanics do allow for things like pieces of eggshell jumping together and forming an intact egg, but this is also extremely unlikely statistically.

Spin_Network

Great link, especially the pressureless fluid sphere:http://casa.colorado.edu/~ajsh/collapse.html

of course things have been moving quite further from that, the Universe is thought NOT to be a pressureless fluid, its dynamical and this recent paper goea a long way into details:http://arxiv.org/abs/gr-qc/0505032

actually gives a good example of the Hydrogen Atom in a New light?

I may state that the Pressureless fluid is thought to be the 'Negative Space' in some models between Galaxies..far from positive matter.

The recent paper I linked to goes a good way to stating that the Blackhole Singularities created by Stars, is discrete from the Universal Singularities that create Galaxies..and thus Hydrogen?..they take the limit of LQG(loop quantum Gravity), and using LQC,(Loop Quantum Cosmology) find that 'seperation' is th key to understanding.

A uniform Phase Space (pressureless Sphere) has within its substance, an un-unformed Geometry, now this is to say that if one was to be contained within a present GR frame of reference, lets say from within our Galaxies, and one was to Quantizise the Geometry of Space you are contained with, then the solution to Einsteins Field Equations leads down to a LQG structure, generalised to the Hydrogen Atom. Now the same paper is more or less stating, if one starts from the same Ref frame, and extrapolates outwards into the LQC domain,,then there are different solutions..LQG is NOT found in the LQC...open Universe!

P.S there are recent posters who have been advocating this scenario, and at a price of being banned:http://www.physicsforums.com/showthread.php?t=41455

yet if one looks closely..page ten of this:http://arxiv.org/PS_cache/hep-th/pdf/0408/0408220.pdf

then one can clearly see that there is a major shift occurring in some Cosmological theoricians thinking.

As far as I understand that is?

Honorable_Death

I always thought a white hole was the exact opposite of a black hole, a black hole takes in information, a whitel hole extracts information. I also thought that a white hole had antigravity. am i wrong?