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Black holes do not exist where space and time do not exist, says new theory

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Re: Black holes do not exist where space and time do not exist, says new theory

#41

Post by tjradcliffe »

givan wrote: post #33

Having so little evidence and information about the phenomena http://en.wikipedia.org/wiki/Black_hole#Observational_eviden... the entire theory around black holes is a mathematical model that probably has nothing to do with the real phenomena.

Absence of information in Wikipedia isn't very good evidence that there isn't very much evidence.

Black holes can be observed in multiple ways:

1) radiation from infalling matter 2) gravitational lensing 3) dynamics of orbiting objects

Remember: we not see the moon by its own light. We see the moon by the light it reflects from the sun. That reflected light is a direct causal consequence of the moon's existence, and we quite properly take it as such... even though the moon emits no light of its own.

No one, to the best of my knowledge, has ever suggested we ought to treat the evidence for the Moon as scanty or inadequate on this basis. So the fact that the radiation we see from black holes originates from the heat of infalling matter, which is a direct causal consequence of the black hole's existence, should constitute similarly strong evidence.

Lensing and dynamical measurements are also quite direct, strong and compelling. There exist compact bodies with more than 1.4 solar masses, which is the limit for nuclear matter (we would have to be wrong about quite a lot of nuclear physics for this to be otherwise.)

The question is: what is the best theory to describe black holes, given we know based on this deep and broad evidence that they exist? Currently we have a rough combination of GR and quantum theory, and while the theory has issues, the claim it "probably has nothing to do with the real phenomenon" is minimally plausible.

Re: Black holes do not exist where space and time do not exist, says new theory

#42

Post by pavel_lishin »

laxatives wrote: post #7
filearts wrote: post #3

"In gravity's rainbow, space does not exist below a certain minimum length, and time does not exist below a certain minimum time interval" Does this imply that neither space nor time can go below the given threshold independently? I.e.: could a situation be imagined where time remains above the minimal interval, but space is below? Also, would those answers be different depending on the observer's time / position?

I'm definitely not an expert, but I was under the impression that both space and time are already thought to be discrete and have minimum quanta, Planck length (10^-36 m) and Planck time (10^-44 s). I guess this new theorem suggests that not only do they have minimum values, they don't exist between these points. Sort of like how pixels aren't really sized objects, but they sort of fill the space between them -- this…

I thought that it was the opposite - you can't draw half a pixel on a screen. (Perhaps a better analogy would be that you can't represent every real number as a floating point integer.)

Re: Black holes do not exist where space and time do not exist, says new theory

#43

Post by gohrt »

Retric wrote: post #35
mrfusion wrote: post #28

Earlier quoted context omitted.

So does discrete space and time also solve zenos paradox? (or was that already solved classically?)

Yes. But Zenos paradox has a simple solution; Time. It takes k(1) * 1/x time to reach k(2) * 1/x location assuming constant velocity. Basically moving an infinitely small distance takes an infinitely small unit of time.

Zeno's paradox assumes less than "constant velocity". It assumes that there is a minimum finite velocity, or that an infinite number of moments in time must be experienced, not skipped over.

Zeno's paradox is about our casual/informal passing between the continuous and the discrete.

If in reality there is some planck-length-like discrete grid structure to the universe, there is no paradox.

Re: Black holes do not exist where space and time do not exist, says new theory

#47

Post by memracom »

Could it be that when space and time get stretched beyond the Planck interval, then the black hole ceases to exist at all beyond that point? In other words, the center of a black hole is non-existence itself.

Looking at it from the time angle, we all blink in and out of existence constantly. But when time and space gets stretched too far, it becomes impossible to blink back into existence, as if the process runs out of gas if the out-of-existence time period is too long.

Re: Black holes do not exist where space and time do not exist, says new theory

#48

Post by Retric »

gohrt wrote: post #43
Retric wrote: post #35

Earlier quoted context omitted.

Yes. But Zenos paradox has a simple solution; Time. It takes k(1) * 1/x time to reach k(2) * 1/x location assuming constant velocity. Basically moving an infinitely small distance takes an infinitely small unit of time.

Zeno's paradox assumes less than "constant velocity". It assumes that there is a minimum finite velocity, or that an infinite number of moments in time must be experienced, not skipped over. Zeno's paradox is about our casual/informal passing between the continuous and the discrete. If in reality there is some planck-length-like discrete grid structure to the universe, there is no paradox.

There are two options that are intuitively acceptable.

Discrete space, or continuous space and time. You can travel through infinite points in finite time iff time is infinitely divisible.

Re: Black holes do not exist where space and time do not exist, says new theory

#49

Post by PaulHoule »

Steuard wrote: post #31
PaulHoule wrote: post #27

As a physics PhD I feel like an idiot for accepting the theory of the classical black hole. If you write the equations for the space around a black hole in the straightforward way you see a singularity at the event horizon. You can make a coordinate change that makes this singularity go away, but then you get the classical black hole singularity where there is either an "end of time" or an infinitely dense point or r…

Counterargument to "the Planck scale is blown up to be visible": The expanding universe itself has (or very probably has) stretched by a factor starting to push into "practical infinity" territory since the Big Bang. (As I recall, common models of cosmic inflation require a minimum of 60 "e-foldings" of expansion in the first moments of the universe's existence: a factor of 10^26 or so, not counting the considerable…

Well, any funny business that happened at the Planck scale during the big bang is hidden from us by an ionized cloud of gas. Maybe there is some trace left in the CMB, but there could be other physics in the way.

People have often said that "physics breaks down" at a gravitational singularity, but it is right to say that the theory of GR breaks down. Singularities generally are a sign that your theory is incomplete and aren't something that occurs in nature.

My argument is that the coordinate transformation and analytic continuation of the schwarzchild singularity is invalid, not that anything specific happens because of high curvature. The semiclassical view is that the event horizon is a quantum object, and if that is the case why believe the classical theory of the interior.

There is also the classical story that an outside observer sees it take forever for something to hit the event horizon but that the semiclassical theory says the black hole decays so presumably an outside observer sees the in falling object get burned up by hawking radiation or otherwise destroyed by something that happens at the eh.

Somehow the physics establishment denies there is a contradiction too and it is certainly true that the wall of fire has it's own problems, but that is because our current theories don't entirely work.

Re: Black holes do not exist where space and time do not exist, says new theory

#50

Post by Steuard »

PaulHoule wrote: post #49
Steuard wrote: post #31

Earlier quoted context omitted.

Counterargument to "the Planck scale is blown up to be visible": The expanding universe itself has (or very probably has) stretched by a factor starting to push into "practical infinity" territory since the Big Bang. (As I recall, common models of cosmic inflation require a minimum of 60 "e-foldings" of expansion in the first moments of the universe's existence: a factor of 10^26 or so, not counting the considerable…

Well, any funny business that happened at the Planck scale during the big bang is hidden from us by an ionized cloud of gas. Maybe there is some trace left in the CMB, but there could be other physics in the way. People have often said that "physics breaks down" at a gravitational singularity, but it is right to say that the theory of GR breaks down. Singularities generally are a sign that your theory is incomplete a…

When I'm talking about the Planck scale being "blown up" to observable size during the Big Bang, I'm not talking about any need to look past the CMB, I'm talking about right here, where we're sitting. If there's some issue in which significant "stretching" of spacetime (as via a coordinate transformation) can make Planck scale effects important even in regions of finite curvature, then we ought to be sitting in such a region right now, here on Earth.

Based just on what you've said here, you seem to be conflating the notion of a true curvature singularity (where "physics breaks down") with a mere coordinate singularity (like the event horizon of a Schwarzchild black hole in asymptotically flat spherical coordinates, or the north/south poles of the earth in latitude/longitude coordinates: there's an "infinitely stretched coordinate transformation" required to resolve the latter, too). Specifically, it sounds like you're worried about the coordinate transformation that's necessary to eliminate the infinity that shows up at the event horizon in "normal" spherical coordinates. But why should I think that those coordinates (which are optimized to describe the flat space infinitely far from the black hole) reflect any special physical "truth"? Just for instance, if you set up a local coordinate system based on the proper time and length as measured by a freely-falling infalling observer, there's no trace of any infinity in the coordinates or metric at the event horizon. And there's no coordinate-independent quantity in classical GR that diverges at the event horizon. This is why most physicists aren't worried about the event horizon being a meaningful singularity in classical GR.

Now, bringing in a semiclassical analysis (or presumably a full quantum analysis, if you've got one; also, call Stockholm) does lead to interesting effects related to the event horizon. But that has nothing to do with coordinate singularities in classical GR and everything to do with the causal structure of spacetime. (Personally, I do harbor some significant doubts about whether we should trust the classical description of the black hole interior once we have a full quantum theory, so I've been quite interested to see the recent firewall questions come up. But the arguments casting doubt on those conclusions are pretty strong, too.) But regardless of my hunches about what will be true in a "final" theory, semiclassical theory is really quite clearly in agreement with classical GR that a local observer won't see anything special as they cross the event horizon.

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