What's inside the event horizon

In summary, the conversations discusses the concept of a black hole and its event horizon, which marks the point of no return for anything that enters it, including light. The conversation also touches on the idea of a singularity within the black hole and the limitations of observational evidence in studying it. There is also a discussion about the reliability of using math to understand the event horizon and the possibility of exploring it in the future. The conversation concludes with a discussion about potential sensors for a black hole probe.
  • #36
ClamShell said:
Why is that? Are you in fact referring to the unstable orbits that
slow(and stop) BH spin? I like the unstable orbits better than the
stable orbits if we are still referring to non-rotating BH's. Unstable
orbits carry away the energy that is spinning a BH...another reason
for non-rotating BH's to become more common. That stable orbits
for matter are further out than the photon sphere is not clear to me.
Well, matter always travels at lower than the speed of light, so clearly orbits for matter must be beyond the photon sphere. The photon sphere is, after all, just the orbit of matter in the high-energy limit, and it corresponds to unstable orbits. Any lower-energy orbit will be necessarily further away.

As for slowing down the BH spin, well, I wasn't referring to that issue at all. It was my understanding that the primary slowdown of BH spin comes from the generation of relativistic jets due to matter entering the ergosphere and being expelled out the poles.
 
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  • #37
Chalnoth said:
Well, matter always travels at lower than the speed of light, so clearly orbits for matter must be beyond the photon sphere. The photon sphere is, after all, just the orbit of matter in the high-energy limit, and it corresponds to unstable orbits. Any lower-energy orbit will be necessarily further away.

As for slowing down the BH spin, well, I wasn't referring to that issue at all. It was my understanding that the primary slowdown of BH spin comes from the generation of relativistic jets due to matter entering the ergosphere and being expelled out the poles.

Photons are deflected more than matter(twice?) in a spherical g field...therefore
photons need to "orbit" further away or be spiraled into the BH. Does that make
sense? Or is my dyslexia acting up. It was non-intuitive for Bohr to say that
electron orbits are lower in energy when closer to the nucleus, worked for him.
Anybody got concrete facts here. Anyway, 212000 km/s may still be a property
of unstable orbits near(but outside) the event horizon...what we do "know"
is that V_escape >= c, for photons inside the event horizon trying to get out.
Or we don't...since they are behind the event horizon and cannot be observed...
and therefore cannot be described via maths. Remember, the whole point is
not to rule-out the wormhole via untested "pseudo-concepts".
 
  • #38
ClamShell said:
Anybody got concrete facts here.

We're discussing black holes and you want concrete facts? Swinging a miss there.

Anyway, 212000 km/s may still be a property
of unstable orbits near(but outside) the event horizon...what we do "know"
is that V_escape >= c, for photons inside the event horizon trying to get out.
Or we don't...since they are behind the event horizon and cannot be observed...
and therefore cannot be described via maths. Remember, the whole point is
not to rule-out the wormhole via untested "pseudo-concepts".

If we can't detect anything (light etc) leaving the black hole, I'd say it's safe to assume the gravity is strong enough to require an escape velocity >c.
 
  • #39
ClamShell said:
Photons are deflected more than matter(twice?) in a spherical g field...therefore
photons need to "orbit" further away or be spiraled into the BH. Does that make
sense? Or is my dyslexia acting up.
Well, I think we'd need to delve into the math to be certain, which I haven't done in quite a while, but just bear in mind that any matter will gravitate like a photon as long as its kinetic energy is much greater than its mass energy. The orbital radius of a particle must therefore be a continuous function of velocity which limits to the photon sphere at v=c.

Must this function be monotonic? I believe so, but I confess I'm not absolutely certain. And my Google-fu is failing me in finding a more authoritative source at the moment.

ClamShell said:
It was non-intuitive for Bohr to say that
electron orbits are lower in energy when closer to the nucleus, worked for him.
Bear in mind that this is the case with gravitational orbits as well, provided you include both potential and kinetic energy.

ClamShell said:
Or we don't...since they are behind the event horizon and cannot be observed...
and therefore cannot described via maths. Remember, the whole point is
not to rule-out the wormhole via untested "pseudo-concepts".
Since anything that escapes the black hole must first cross the event horizon, and since the escape velocity is the speed of light at the event horizon, nothing can escape a black hole, even without worrying about whatever exotic things might or might not be happening inside.

Unless you count Hawking radiation. But since Hawking radiation is completely thermalized, well, this implies that escape out of a black hole involves utter destruction.
 
  • #40
Chalnoth said:
Well, I think we'd need to delve into the math to be certain, which I haven't done in quite a while, but just bear in mind that any matter will gravitate like a photon as long as its kinetic energy is much greater than its mass energy. The orbital radius of a particle must therefore be a continuous function of velocity which limits to the photon sphere at v=c.

Must this function be monotonic? I believe so, but I confess I'm not absolutely certain. And my Google-fu is failing me in finding a more authoritative source at the moment.


Bear in mind that this is the case with gravitational orbits as well, provided you include both potential and kinetic energy.


Since anything that escapes the black hole must first cross the event horizon, and since the escape velocity is the speed of light at the event horizon, nothing can escape a black hole, even without worrying about whatever exotic things might or might not be happening inside.

Unless you count Hawking radiation. But since Hawking radiation is completely thermalized, well, this implies that escape out of a black hole involves utter destruction.

I would add that HR doesn't really "escape" the event horizon, but rather the portion that seems to escape was part of pair creation outside of the horizon. This is of course why HR isn't superluminal either, and its origin in a quantum process unrelated to the original infalling matter is precisely why it carries to information about that original matter with it. HR is essentially quantum static originating just beyond the EH, with a component that is left within the EH which we cannot observe.

Your statement that the EH is still an absolute limit for escape of matter, or anything at c still holds.
 
  • #41
nismaratwork said:
I would add that HR doesn't really "escape" the event horizon, but rather the portion that seems to escape was part of pair creation outside of the horizon. This is of course why HR isn't superluminal either, and its origin in a quantum process unrelated to the original infalling matter is precisely why it carries to information about that original matter with it. HR is essentially quantum static originating just beyond the EH, with a component that is left within the EH which we cannot observe.

Your statement that the EH is still an absolute limit for escape of matter, or anything at c still holds.
Well, as I alluded to a bit earlier, the information about what went into the black hole is actually encoded in the Hawking radiation that leaves it, so in a sense, what goes in must come out. It may not literally be particle-for-particle, of course, but somehow the precise quantum-mechanical description of a black hole must allow at least the information regarding the matter that formed the black hole to leave as Hawking radiation.
 
  • #42
Chalnoth said:
Well, as I alluded to a bit earlier, the information about what went into the black hole is actually encoded in the Hawking radiation that leaves it, so in a sense, what goes in must come out. It may not literally be particle-for-particle, of course, but somehow the precise quantum-mechanical description of a black hole must allow at least the information regarding the matter that formed the black hole to leave as Hawking radiation.

Finally, somebody likes Entropy_in = Entropy_out...a BH, wormH, WH construct
satisfies this without a "pasta" machine model. I suggest that what goes in is
exactly what comes out. IE, if Alice goes in, Alice comes out...not Bob.
 
  • #43
ClamShell said:
Finally, somebody likes Entropy_in = Entropy_out...a BH, wormH, WH construct
satisfies this without a "pasta" machine model. I suggest that what goes in is
exactly what comes out. IE, if Alice goes in, Alice comes out...not Bob.

But if Jared goes in past the event horizon, Jared won't be coming out. I may reappear a bit later as a burst of radiation of some form. But I don't think I'd be picking up with my life any time soon.

On a more serious note, if a black hole gives out what it takes in (entropy_in = entropy_out), does this mean that white holes aren't require to 'balance' things?
 
  • #44
ClamShell said:
Finally, somebody likes Entropy_in = Entropy_out...a BH, wormH, WH construct
satisfies this without a "pasta" machine model. I suggest that what goes in is
exactly what comes out. IE, if Alice goes in, Alice comes out...not Bob.
Well, that is a possibility, but I'm actually rather skeptical. We do know that the matter coming out of a black hole has a thermal spectrum, after all. Among other things, that means that you get a different distribution of particle types coming out than went in. So I don't think it's quite as simple as the same thing coming out as went in, but rather that what comes out is a unitary evolution of what went in (meaning that if one had a hypothetical perfect computer and new the underlying physics perfectly, one could calculate every bit of Hawking Radiation coming out of a black hole if one knows everything that falls into it).
 
  • #45
jarednjames said:
On a more serious note, if a black hole gives out what it takes in (entropy_in = entropy_out), does this mean that white holes aren't require to 'balance' things?
A white hole is just the time reverse of a black hole. This means that white holes are basically a contradiction in terms, because they indicate a system that decreases in entropy as time goes forward, which contradicts what we mean by time going forward.
 
  • #46
jarednjames said:
But if Jared goes in past the event horizon, Jared won't be coming out. I may reappear a bit later as a burst of radiation of some form. But I don't think I'd be picking up with my life any time soon.

On a more serious note, if a black hole gives out what it takes in (entropy_in = entropy_out), does this mean that white holes aren't require to 'balance' things?

I'm suggesting that the BH horizon is the input node, the wormH is the communication
link, and the WH horizon is the output node. IE, the BH, wormH, WH is a single construct
of which we can only see the BH event horizon...that there is a stage behind the curtain.
 
  • #47
ClamShell said:
I'm suggesting that the BH horizon is the input node, the wormH is the communication
link, and the WH horizon is the output node. IE, the BH, wormH, WH is a single construct
of which we can only see the BH event horizon...that there is a stage behind the curtain.

The entire concept of the WH was really just a (now obsolete) construction to explain Quasars. White Holes are, as Chalnoth said in more technical terms: bunk. You're also describing a traversable wormhole for massive amounts of energy, which would tend to tear our understanding of the universe asunder. Either the universe is far larger (and therefore older) and curved than is currently believed, or your WH exist in another universe, which does nothing to keep this little system Unitary.
 
  • #48
ClamShell said:
I'm suggesting that the BH horizon is the input node, the wormH is the communication
link, and the WH horizon is the output node. IE, the BH, wormH, WH is a single construct
of which we can only see the BH event horizon...that there is a stage behind the curtain.

This is essentially exactly how the maximally extended Kruskal–Szekeres coordinates and the maximally extended schwarzschild solution function. Of note: It is impossible for an observer to travel through the Einstein-Rosen bridge connecting the two separate universes. Also, the "white hole" exists infinitely far in the past, implying that this is an eternal spacetime solution. So not only can we never hope to find this white hole (as it is always infinitely far in the past), but any physical object this solution might represent cannot exist in our universe, since it is only finitely old.
 
  • #49
Why do we assume that objects inside the event horizon do not travel faster than c?
 
  • #50
skeptic2 said:
Why do we assume that objects inside the event horizon do not travel faster than c?

Perhaps the simple answer is that if they went faster than c,
they would(could) escape.

Or perhaps it is closely tied to V_escape = root(GM/R)*root(2) that can
result in V_escape > c, for R < R_eh, and the photons have
petered-out to c when they get to the event horizon. IE, a
misconception that escape velocity > c implies anything
more than a more difficult job for photons going c to get out.
 
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  • #51
ClamShell said:
Perhaps the simple answer is that if they went faster than c,
they would(could) escape.
That's a circular argument.

ClamShell said:
Or perhaps it is closely tied to V_escape = root(GM/R)*root(2) that can result in V_escape > c, for R < R_eh, and the photons have
petered-out to c when they get to the event horizon. IE, a misconception that escape velocity > c implies anything more than a more difficult job for photons going c to get out.
Photons always travel at c so there's no real argument about photons exceeding c. Is there any reason why massive particles cannot travel faster than c inside the EV?
 
  • #52
skeptic2 said:
Photons always travel at c so there's no real argument about photons exceeding c. Is there any reason why massive particles cannot travel faster than c inside the EV?

OK, for particles of matter:

Or perhaps it is closely tied to V_escape = root(GM/R)*root(2) that can result in V_escape > c, for R < R_eh, a misconception that escape velocity > c implies anything more than a more difficult job for matter to get out.

My personal favorite is that the hypothetical structure on the other side
of the horizon is an "independent coordinate system" and obeys
the very same rules that we have here. Circular again?

Or would you prefer the concept that the Schwarzschild Metric
really represents two "independent coordinate systems" with
different rules?
 
  • #53
ClamShell said:
OK, for particles of matter:

Or perhaps it is closely tied to V_escape = root(GM/R)*root(2) that can result in V_escape > c, for R < R_eh, a misconception that escape velocity > c implies anything more than a more difficult job for matter to get out.

My personal favorite is that the hypothetical structure on the other side
of the horizon is an "independent coordinate system" and obeys
the very same rules that we have here. Circular again?

Or would you prefer the concept that the Schwarzschild Metric
really represents two "independent coordinate systems" with
different rules?

Nothing that crosses the event horizon IS matter anymore, at best you're talking about radiation. Remember, a neutron star, or even a hypothetical quark star isn't dense enough to have an event horizon; by the time you reach that you've already gone beyond the limits of degenerate matter. MASS yes, but what is that in the context of an unobservable region?
 
  • #54
nismaratwork said:
Nothing that crosses the event horizon IS matter anymore, at best you're talking about radiation. Remember, a neutron star, or even a hypothetical quark star isn't dense enough to have an event horizon; by the time you reach that you've already gone beyond the limits of degenerate matter. MASS yes, but what is that in the context of an unobservable region?

I understand that when matter reaches the singularity it may no longer be matter but it's no longer traveling either. Between the EV and the singularity, how fast can massive particles travel and why? Is there some prohibition against exceeding c in that region?
 
  • #55
nismaratwork said:
Nothing that crosses the event horizon IS matter anymore, at best you're talking about radiation. Remember, a neutron star, or even a hypothetical quark star isn't dense enough to have an event horizon; by the time you reach that you've already gone beyond the limits of degenerate matter. MASS yes, but what is that in the context of an unobservable region?

There are some pretty smart posters on this thread; if we let your post
cook for awhile, you should get a decent answer.
 
  • #56
nismaratwork said:
Nothing that crosses the event horizon IS matter anymore, at best you're talking about radiation. Remember, a neutron star, or even a hypothetical quark star isn't dense enough to have an event horizon; by the time you reach that you've already gone beyond the limits of degenerate matter. MASS yes, but what is that in the context of an unobservable region?

Dense mass without a horizon seems to be like a brick wall to falling matter.
Dense mass with a horizon seems to be like a curtained stage with the brick
wall there or not there or both or neither. IE, if we linger long enough just
above the horizon, by the time we finally cross the horizon, the brick wall
will have evaporated.
 
  • #57
ClamShell said:
Dense mass without a horizon seems to be like a brick wall to falling matter.
Dense mass with a horizon seems to be like a curtained stage with the brick
wall there or not there or both or neither. IE, if we linger long enough just
above the horizon, by the time we finally cross the horizon, the brick wall
will have evaporated.

There's no wall, especially since you have to remember that everything falling into a black hole is ripped apart by gravitational tidal forces, and blasted by radiation. The EH has no physical existence, it's just the ever-changing (as long as there is infalling matter or HR) demarcation of the point of no return. Degenerate matter is dense, yes, but even that would be "sphagettified" as it fell into a BH. In a very real sense, anything on OUR side of the EH can never be observed by us to cross the EH, so there is the theoretical notion of a wall. Keep in mind that the infalling mass will not experience any such barrier, and crosses the EH without any resistance. I believe that your understanding of Einstein's view of gravity and spacetime is incomplete, and to grasp just what a black hole is, you need to understand that first.

skeptic2 said:
I understand that when matter reaches the singularity it may no longer be matter but it's no longer traveling either. Between the EV and the singularity, how fast can massive particles travel and why? Is there some prohibition against exceeding c in that region?

I truly have no idea... certainly as Chalnoth has said earlier until you hit the singularity you can work out numbers with GR equations, but there is in my view, plenty of reason not to trust them. I don't think velocity and the notion of individual particles applies beyond the EH, but who knows? Truly, we just can't know anything about what happens past the EH; there is only theory that ceases to be meaningful at the most critical point (the singularity). I think that a theory of quantum-gravity should eliminate the singularity, and then you might have some reasonable predictions, but we're just not there yet.
 
  • #58
nismaratwork said:
There's no wall, especially since you have to remember that everything falling into a black hole is ripped apart by gravitational tidal forces, and blasted by radiation. The EH has no physical existence, it's just the ever-changing (as long as there is infalling matter or HR) demarcation of the point of no return. Degenerate matter is dense, yes, but even that would be "sphagettified" as it fell into a BH. In a very real sense, anything on OUR side of the EH can never be observed by us to cross the EH, so there is the theoretical notion of a wall. Keep in mind that the infalling mass will not experience any such barrier, and crosses the EH without any resistance. I believe that your understanding of Einstein's view of gravity and spacetime is incomplete, and to grasp just what a black hole is, you need to understand that first.

I would be the first to admit that my understanding of everything is incomplete.
Only fools are so confident as to think they know it all, and there are no fools
here. Not even Einstein would claim to have a complete knowledge of gravity.
I suspect you mean that my knowledge of Einstein is incomplete...yours is?

It is accepted by previous posters, that distant observers will never see a
a test mass cross the horizon. I take this to mean that when it does finally
happen(relative to the test mass), the stage and its contents will have evaporated.
Supposedly by Hawking radiation. And that a distant observer does not have a
long enough duration to observe this. But the test mass(by its own clock)
would experience nothing in particular because (after infinity by distant
observers clocks), the BH will have evaporated. A no show.
 
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  • #59
nismaratwork said:
Nothing that crosses the event horizon IS matter anymore, at best you're talking about radiation.

This isn't true. If a star collapses and forms a black hole, then matter falling towards the star, but above the star, will remain matter far inside the event horizon. Matter that falls into a black hole at the centre of a galaxy won't spaghettified until far inside the event horizon.
skeptic2 said:
I understand that when matter reaches the singularity it may no longer be matter but it's no longer traveling either. Between the EV and the singularity, how fast can massive particles travel and why? Is there some prohibition against exceeding c in that region?

The speed of light is the local speed limit everywhere, even inside black holes.
nismaratwork said:
There's no wall, especially since you have to remember that everything falling into a black hole is ripped apart by gravitational tidal forces, and blasted by radiation.

According to the book Quantum Fields in Curved Space by Birrell and Davies, pages 268-269,
These consideration resolve an apparent paradox concerning the Hawking effect. The proper time for a freely-falling observer to reach the event horizon is finite, yet the free-fall time as measured at infinity is infinite. Ignoring back-reaction, the black hole will emit an infinite amount of radiation during the time that the falling observer is seen, from a distance to reach the event horizon. Hence it would appear that, in the falling frame, the observer should encounter an infinite amount of radiation in a finite time, and so be destroyed. On the other hand, the event horizon is a global construct, and has no local significance, so it is absurd to0 conclude that it acts as physical barrier to the falling observer.

The paradox is resolved when a careful distinction is made between particle number and energy density. When the observer approaches the horizon, the notion of a well-defined particle number loses its meaning at the wavelengths of interest in the Hawking radiation; the observer is 'inside' the particles. We need not, therefore, worry about the observer encountering an infinite number of particles. On the other hand, energy does have a local significance. In this case, however, although the Hawking flux does diverge as the horizon is approached, so does the static vacuum polarization, and the latter is negative. The falling observer cannot distinguish operationally between the energy flux due to oncoming Hawking radiation and that due to the fact that he is sweeping through the cloud of vacuum polarization. The net result is to cancel the divergence on the event horizon, and yield a finite result, ...

This finite amount of radiation is negligible for observers freely falling into a black hole.
ClamShell said:
It is accepted by previous posters, that distant observers will never see a
a test mass cross the horizon. I take this to mean that when it does finally
happen(relative to the test mass), the stage and its contents will have evaporated.
Supposedly by Hawking radiation. And that a distant observer does not have a
long enough duration to observe this. But the test mass(by its own clock)
would experience nothing in particular because (after infinity by distant
observers clocks), the BH will have evaporated. A no show.

Consider two observers, observer A that falls across the the event horizon and observer B that hovers at a finite "distance" above the event horizon, and two types of (uncharged) spherical black holes, a classical black hole that doesn't emit Hawking radiation and a semi-classical black hole that does.

For the classical black hole case, B "sees" A on the event horizon at infinite future time, and B never sees the singularity.

For the semi-classical black hole case, at some *finite* time B simultaneously "sees": A on the event horizon; the singularity. In other words, the singularity becomes naked, and A winks out of existence at some finite time in the future for B.

In both cases, A crosses the event horizon, remains inside the event horizon, and hits the singularity. In both cases, B, does not see (even at infinite future time) A inside the event horizon, as this view is blocked by the singularity.

These conclusions can be deduced from Penrose diagrams, FIGURE 5.17 and FIGURE 9.3 in Carroll's text, and Fig. 12.2 and Fig, 14.4 in Wald's text, or

http://www.google.ca/imgres?imgurl=...a=X&ei=3pmdTP63FcaAlAexkYntAg&ved=0CBwQ9QEwAA.
 
  • #60
George Jones said:
Consider two observers, observer A that falls across the the event horizon and observer B that hovers at a finite "distance" above the event horizon, and two types of (uncharged) spherical black holes, a classical black hole that doesn't emit Hawking radiation and a semi-classical black hole that does.

For the classical black hole case, B "sees" A on the event horizon at infinite future time, and B never sees the singularity.

For the semi-classical black hole case, at some *finite* time B simultaneously "sees": A on the event horizon; the singularity. In other words, the singularity becomes naked, and A winks out of existence at some finite time in the future for B.

In both cases, A crosses the event horizon, remains inside the event horizon, and hits the singularity. In both cases, B, does not see (even at infinite future time) A inside the event horizon, as this view is blocked by the singularity.

I guess this holds even when B is a distant(but finite) observer. Is it because
A, in the Hawking radiation case, "pairs-up" with A' (a wave), that A can wink
out when A' escapes the grip of the black hole(becomes Hawking radiation) and
heads for infinity as A drops through the event horizon? Does A' come from
additional infalling matter or does A' come from the black hole? IE, does the
black hole in both cases, last forever? Do modern black holes "evaporate"?
 
  • #61
George Jones said:
The speed of light is the local speed limit everywhere, even inside black holes.

Thank you George. I understand why c is the limit outside of black holes but not why those reasons must also apply inside them.
 
  • #62
George Jones said:
This isn't true. If a star collapses and forms a black hole, then matter falling towards the star, but above the star, will remain matter far inside the event horizon. Matter that falls into a black hole at the centre of a galaxy won't spaghettified until far inside the event horizon.

Yes, I realize that, but for the sake of this thread I didn't think that getting into the distinction between stellar mass and AGNs was such a good idea.


George Jones said:
According to the book Quantum Fields in Curved Space by Birrell and Davies, pages 268-269,


This finite amount of radiation is negligible for observers freely falling into a black hole.


Consider two observers, observer A that falls across the the event horizon and observer B that hovers at a finite "distance" above the event horizon, and two types of (uncharged) spherical black holes, a classical black hole that doesn't emit Hawking radiation and a semi-classical black hole that does.

Well there shouldn't be ANY HR emitted if there's anyone around to fall into a black hole (background temps and all). I was thinking again, of a stellar mass black hole with an active accretion disk, not radiation emitted from the BH itself. Specifically a Kerr BH with a rapid rotation and a fairly robust ergoregion, probably with a companion star and constant infalling matter. Again, I didn't see the need to enter into those complexities when the basics seemed to be at issue. Thanks for the clarification however.
 
  • #63
http://en.wikipedia.org/wiki/Wormhole

So here's the wiki page on wormholes.

Now, it describes two wormholes, one which may possibly be present by a black holes:
"The first type of wormhole solution discovered was the Schwarzschild wormhole which would be present in the Schwarzschild metric describing an eternal black hole, but it was found that this type of wormhole would collapse too quickly for anything to cross from one end to the other."

But these cannot be traversed as it explains and as such, I don't understand how particles as the article puts it are able to 'cross between the two universes'.
Wormholes which could actually be crossed, known as traversable wormholes, would only be possible if exotic matter with negative energy density could be used to stabilize them (many physicists such as Stephen Hawking[1], Kip Thorne[2], and others[3][4][5] believe that the Casimir effect is evidence that negative energy densities are possible in nature). Physicists have also not found any natural process which would be predicted to form a wormhole naturally in the context of general relativity, although the quantum foam hypothesis is sometimes used to suggest that tiny wormholes might appear and disappear spontaneously at the Planck scale.

This uses negative energy, enough said.

Now, you keep pointing us to the wikis and to read them, and I have done. I have also done some digging and following links provided in the wikipedia article (the articles I believe you are reading) I found this (http://casa.colorado.edu/~ajsh/schww.html): [Broken]
Do Schwarzschild wormholes really exist?
Schwarzschild wormholes certainly exist as exact solutions of Einstein's equations.
However:
# When a realistic star collapses to a black hole, it does not produce a wormhole;
# The complete Schwarzschild geometry includes a white hole, which violates the second law of thermodynamics;
# Even if a Schwarzschild wormhole were somehow formed, it would be unstable and fly apart.

As the type of wormhole you are referring to is the above Schwarzschild wormhole, everything I have read so far is very clear in what it is saying regarding their existence - they only exist under the 'perfect' conditions of the equations. "when a realistic star collapses to form a black hole, it does not produce a wormhole.". So unless you can cite sources which show these wormholes can exist when a star collapses, this is overly speculative and against PF guidelines. It is pointless us discussing this if it just isn't possible and so far, nothing has shown it is.
 
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  • #64
Dmitry67 said:
Free falling observer does not observe the same Hawking radiation as observer located far from BH because for the falling observer event horizon is in different place. So the amount of hawking radiation he receives is very small. both position of the apparent Horizon and Hawking radiation are observer-dependent.

Time dilation is infinite only for the hovering observer, so true, observer hovering near the horizon would see the Universe accelerated and blue-shifted. However, falling observer would see the Universe red-shifted (surprise!)

I misunderstood this post first time through. Now I'm thinking Dmitry
has a clever way of minimizing the HR by allowing the HR evaporation
to reduce the BH mass and thereby reduce the horizon so the infalling
test mass has an even harder time getting to the horizon and minimizing
the HR for the free-falling test mass. Wait, is this a bit too circular?
Nevermind, whatever makes the HR non-lethal is OK by me.
 
  • #65
jarednjames said:
http://en.wikipedia.org/wiki/Wormhole

So here's the wiki page on wormholes.

Now, it describes two wormholes, one which may possibly be present by a black holes:


But these cannot be traversed as it explains and as such, I don't understand how particles as the article puts it are able to 'cross between the two universes'.


This uses negative energy, enough said.

Now, you keep pointing us to the wikis and to read them, and I have done. I have also done some digging and following links provided in the wikipedia article (the articles I believe you are reading) I found this (http://casa.colorado.edu/~ajsh/schww.html): [Broken]


As the type of wormhole you are referring to is the above Schwarzschild wormhole, everything I have read so far is very clear in what it is saying regarding their existence - they only exist under the 'perfect' conditions of the equations. "when a realistic star collapses to form a black hole, it does not produce a wormhole.". So unless you can cite sources which show these wormholes can exist when a star collapses, this is overly speculative and against PF guidelines. It is pointless us discussing this if it just isn't possible and so far, nothing has shown it is.

Yes, good work...wormholes are in the peer literature, so we can discuss
them. The GR model (guess it's not quantum mechanical) has them doing
such-and-such in GR metrics. QM is bound to be a better framework, but
pretty speculative...lets never mention them again...and let's never mention
quantum gravity either...and the strong force, what's that all about? Don't
mention it. And fringe physics and all the nuts in the basement doing it.
And alpha...who cares if it's changing. etc., etc. Can you add to the list
any more forbidden topics? I don't even like wormholes...I am much more
interested in a BH evaporating before matter can ever fall into it. Are
you going to forbid this too? Seriously, if a concept is only on somebody's
personal webpage, I rather not have it jammed down my throat either.
 
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  • #66
What are you talking about ClamShell? Seriously, I don't want to sound nasty here, but I find your posts to be full of metaphors and riddles and make little sense.

I have nothing against the concept of a wormhole, but so far everything I have read says they cannot be created when a star collapses into a black hole. So discussing it, unless I'm otherwise informed, is pointless.

You don't even like wormholes? A few posts back you were explaining how they were the potential answer to conditions inside the event horizon (something regarding entropy I believe and you not liking the idea of Hawking Radiation).

Stick to the black hole evaporation from now and and let's forget wormholes were ever brought into this particular topic of "What's inside the event horizon?".
 
  • #67
jarednjames said:
...let's forget wormholes were ever brought into this particular topic of "What's inside the event horizon?".

Agreed, but I might forget every now and then.
And let's not mention Schroedinger's Cat either;
half the time when I open the box it's stiff as a
board. What is it that you said about metaphores
and riddles?

Consider this...a way to transport yourself into an infinitely
distant future, is to hover over the event horizon until the
BH finishes evaporating. Imagine all the cool stuff that would
just be lying around, free for the taking. And it should only
take a couple of minutes.

Somebody just hit on my *Wormholes?* thread...and my
dyslexia started acting up...need to take a Tum; or is it
dyspepsia...doesn't matter.
 
  • #68
ClamShell said:
Consider this...a way to transport yourself into an infinitely
distant future, is to hover over the event horizon until the
BH finishes evaporating. Imagine all the cool stuff that would
just be lying around, free for the taking. And it should only
take a couple of minutes.

I believe this is the plot of the Andromeda TV show. A ship gets stuck in the event horizon of a black hole and experiences 300 years of time dilation.

Again, in reality, the gravity that causes the time dilation would cause your immediate destruction.
 
  • #69
jarednjames said:
I believe this is the plot of the Andromeda TV show. A ship gets stuck in the event horizon of a black hole and experiences 300 years of time dilation.

Again, in reality, the gravity that causes the time dilation would cause your immediate destruction.
Well, the idea here is that the ship was able to hover just above the event horizon (it is powered, after all). So it's not completely nuts (except for the fact that the power requirements would be astronomical). The real problem is that that degree of time dilation doesn't occur until you're just outside the event horizon, which means the ship itself was too large for it to work that way.

For an astrophysical black hole, I don't think the tidal forces outside the event horizon would have been enough to destroy the ship.
 
  • #70
jarednjames said:
I believe this is the plot of the Andromeda TV show. A ship gets stuck in the event horizon of a black hole and experiences 300 years of time dilation.

Again, in reality, the gravity that causes the time dilation would cause your immediate destruction.

Remember, weightless, free-falling into a non-rotating BH, with Hawking
radiation of very low intensity inside the rocket ship. Infinity is much bigger
than 300; they must have only been stuck for a picosecond. This destruction
you speak of is only wishful thinking; plenty of sources disagree with
this. Anyway, what's immediate mean when you are approaching the
horizon? The important thing is what Alice(A) sees, not what Bob(B)
sees. Bob sees Alice wink out, that doesn't mean that Alice has past.
IE, Alice's past does not include the evaporation of the BH. And it's
the Carl Sagan movie 'Contact', not the kids show 'Andromeda'.
 
<h2>What is the event horizon?</h2><p>The event horizon is the boundary around a black hole from which nothing, including light, can escape.</p><h2>What happens inside the event horizon?</h2><p>Inside the event horizon, the gravitational pull of the black hole is so strong that it causes space and time to become infinitely distorted. This is known as the singularity.</p><h2>Can anything survive inside the event horizon?</h2><p>No, it is believed that anything that crosses the event horizon will be pulled into the singularity and destroyed.</p><h2>What is the size of the event horizon?</h2><p>The size of the event horizon depends on the mass of the black hole. The more massive the black hole, the larger the event horizon.</p><h2>Is there any way to see inside the event horizon?</h2><p>No, since nothing can escape the event horizon, it is impossible to see or gather any information about what is happening inside.</p>

What is the event horizon?

The event horizon is the boundary around a black hole from which nothing, including light, can escape.

What happens inside the event horizon?

Inside the event horizon, the gravitational pull of the black hole is so strong that it causes space and time to become infinitely distorted. This is known as the singularity.

Can anything survive inside the event horizon?

No, it is believed that anything that crosses the event horizon will be pulled into the singularity and destroyed.

What is the size of the event horizon?

The size of the event horizon depends on the mass of the black hole. The more massive the black hole, the larger the event horizon.

Is there any way to see inside the event horizon?

No, since nothing can escape the event horizon, it is impossible to see or gather any information about what is happening inside.

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