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Can you rip the space time fabric?

by Gravitons
Tags: fabric, space, time
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Gravitons
#1
Apr1-10, 06:24 PM
P: 16
if there is a fabric of space, the four dimension you could call it, space time, is it possible to rip it or open it up, for example do black holes do that, if not what, what would happen?
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chroot
#2
Apr1-10, 06:27 PM
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There is no 'fabric' in any modern physical theory, so there is no 'fabric' to be ripped.

Phrases like "ripping a hole in the space-time continuum" are abuses of notation typically used in science fiction.

- Warren
Gravitons
#3
Apr1-10, 06:32 PM
P: 16
Einsteins general relativity describes a fourth dimension regarding up down, left right, back and forth, the fourth is space time, aka a "fabric of space".
Check it out genius: http://en.wikipedia.org/wiki/Spacetime

chroot
#4
Apr1-10, 06:34 PM
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Can you rip the space time fabric?

Excuse me? You've only been here for a half hour, and you're already insulting one of the site administrators?

Your link does not include the word 'fabric,' by the way. Think hard.

- Warren
Naty1
#5
Apr1-10, 07:01 PM
P: 5,632
No one really knows the answer to your question...we can't even find it nor "sew" it....we have only incomplete hints. I think this is likely because we do not know what space nor time are...nor mass,energy,either for example. And we have no theory (quantum nor relativistic nor informational nor string ) that works at singularities....(big bang, black holes) where ripping seems mostly likely....it could be the "quantum foam" (high energy oscillations) at Planck scale activity "ruins" spacetime and makes distinction between say, space and mass impossible...String theory also hints at this possibility.

There is no 'fabric' in any modern physical theory, so there is no 'fabric' to be ripped.
This is an exaggeration...I think, but not incorrect....had it said "none proven in classical relativity" I'd say "ok" that might be about right. we don't have an agreed upon definiton of "fabric" for one thing....

Anyway, one perspective of spacetime rips can be found here:
http://en.wikipedia.org/wiki/Cosmic_...hip_hypothesis

but these are hypothetical, not experimentally proven.

We have had long discussions in the forums about "what is space-time" and of course no one really knows...but quantum mechanics, and quantum field theory in particular, I believe, posits space time is discrete rather than continuous as in classical relativity. That suggests it to possibly be something....but there is no agreement here either: continuous or discrete?.

You can also look up causal dynamic triangulation as to how spacetime might form, and spin foam is another variety. A recent discussion on the forums from a paper by Verlinde hypothesisizes that space time forms from entropy and while unproven offers I think fascinating possibilities. And of course one can utilize incomplete theories about the universe being formed of information, a relative of entropy....

And a case can be made that the holographic principle offers yet another insight into spacetime, and everything else that we perceive as being three dimensionally space enclosed...maybe everything we know is really area rather than volume based...information content and flow sure seems to be that way.

Another hint at an answer, might be contained in the big bang versus black hole singularities. Apparently Weyl curvature in the former approach zero, or is at least finite, while Weyl Curvature in the latter diverges...so the low entropy of the big bang might be markedly different than the exceedingly high entropy (information) of the latter....
I posted asking about the implications some time ago and never got an answer.

Roger Penrose discusses naked singularities in THE ROAD TO REALITY SECTION 28.8 AND YOU MIGHT GET FURTHER HINTS FROM THE Hawking-Hartle no boundary proposal which Penrose discussesd in 28.9.
however, all the above simply offer tangential insights..not answers because no one has the real solution....yet...
atyy
#6
Apr1-10, 07:12 PM
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Gross et al, Instability of Flat Space at Finite Temperature, Physical Review D, 1982
"In the general theory of relativity, .... the spacetime manifold is warped by the presence of matter. Gravitational collapse can give rise to singularities in the fabric of spacetime"

http://arxiv.org/abs/astro-ph/0012345
"spacetime fabric"

http://arxiv.org/abs/gr-qc/0508121
"fabric of spacetime"
JesseM
#7
Apr1-10, 10:02 PM
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P: 8,470
I remember from Brian Greene's The Elegant Universe that string theory does allow for spacetime topology changes, which can be thought of in terms of ripping /sewing spacetime (like turning a sphere into a doughnut by punching a hole through the middle). No ragged holes that things can fall into and disappear though.
atyy
#8
Apr1-10, 10:28 PM
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Quote Quote by JesseM View Post
I remember from Brian Greene's The Elegant Universe that string theory does allow for spacetime topology changes, which can be thought of in terms of ripping /sewing spacetime (like turning a sphere into a doughnut by punching a hole through the middle). No ragged holes that things can fall into and disappear though.
Interesting! I googled "topology change" and apparently it can even happen in a slightly extended form of classical GR.

http://arxiv.org/abs/hep-th/9109030, http://iopscience.iop.org/0264-9381/8/4/007/
"It is clear from these classical solutions that the problem of topology change has been turned around. The question is not whether topology change can occur, but rather how do we stop topology from changing? Why doesn’t the space around us suddenly split into disconnected pieces?"
Naty1
#9
Apr2-10, 12:02 PM
P: 5,632
I remember from Brian Greene's The Elegant Universe that string theory does allow for spacetime topology changes, which can be thought of in terms of ripping /sewing spacetime (like turning a sphere into a doughnut by punching a hole through the middle).
I had forgotten...have to reread again I guess....Greene does go into some detail about how string theory suggests spacetime can "tear" in ways different from black holes and wormholes....Chapter 11, "Tearing the Fabric of Space"

one concept is minimum distances in short distance geometry which obscures any "rips" as we might think in traditional terms.

In a nutshell Greene discusses theoretical pinching of Calabi-Yau spaces and the possibility of flop transitions to a new topologically distinct shape....and Witten showed a string might encircle such a tear shielding the universe from catastrophic consequences.
IttyBittyBit
#10
Apr2-10, 05:42 PM
P: 159
The level of physics misunderstanding in this thread is astonishing. But I'm not a physicist, so I won't comment. I do feel like I have to correct a few math-related comments though.

Quote Quote by JesseM
I remember from Brian Greene's The Elegant Universe that string theory does allow for spacetime topology changes, which can be thought of in terms of ripping /sewing spacetime (like turning a sphere into a doughnut by punching a hole through the middle). No ragged holes that things can fall into and disappear though.
You can't turn a sphere into a torus by punching a hole in the middle.

Quote Quote by Naty1
...we have only incomplete hints. I think this is likely because we do not know what space nor time are...nor mass,energy,either for example. And we have no theory (quantum nor relativistic nor informational nor string ) that works at singularities....(big bang, black holes) where ripping seems mostly likely....
Yes we do.
Naty1
#11
Apr2-10, 06:13 PM
P: 5,632
I remember from Brian Greene's The Elegant Universe that string theory does allow for spacetime topology changes, which can be thought of in terms of ripping /sewing spacetime (like turning a sphere into a doughnut by punching a hole through the middle). No ragged holes that things can fall into and disappear though.

You can't turn a sphere into a torus by punching a hole in the middle.

That seems to me to be an entirely reasonable analogy. At least as good as the rubber membrane analogy for gravity....

If Itty means in doesn't happen in a single step, a single mathematical conifold transition, I can buy that.....
But there IS a series of diagrams in THE ELEGANT UNIVERSE, Figure 13.3, that shows just such a transition. In fact Smolin says "while string physics remains perfectly well behaved."
Naty1
#12
Apr2-10, 06:17 PM
P: 5,632
I think this is likely because we do not know what space nor time are...nor mass,energy,either for example. And we have no theory (quantum nor relativistic nor informational nor string ) that works at singularities....(big bang, black holes) where ripping seems mostly likely....

Yes we do.
Which part don't you like?? and do provide (a) an explanation of exactly what space and time are or (b) a consistent theory that handles singularities or a reference that explains either. Right now I stand by what I posted.
thanks
IttyBittyBit
#13
Apr2-10, 06:55 PM
P: 159
First of all, a sphere is a 2-dimensional manifold and a doughnut is a 3-dimensional one. You can't continuously transform one into the other; that is just absurd.

What you mean could be a torus (which is the surface of a doughnut). It won't work in this case either:
A sphere is a closed 2-dimensional manifold. So is a torus. A sphere with a single point removed is an open 2-dimensional manifold. You can't construct a homeomorphism from an open manifold to a closed one.

Quote Quote by Naty1
Which part don't you like?? and do provide (a) an explanation of exactly what space and time are or (b) a consistent theory that handles singularities or a reference that explains either. Right now I stand by what I posted.
thanks
You did not explain what you mean by 'singularity'. There are many different kinds of singularities in mathematics. One kind is a removable singularity, and most physical theories deal with this kind quite nicely. Singularities also arise in areas outside of fundamental physics (such as continuum mechanics e.g. the Prandtl-Glauert singularity) and they pose no threat to the acceptability or validity of current theories. I'd be glad to elaborate further, but I will only reply if you precisely define your terminology so I know what exactly we are talking about :)
JesseM
#14
Apr2-10, 07:26 PM
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P: 8,470
Quote Quote by IttyBittyBit View Post
You can't turn a sphere into a torus by punching a hole in the middle.
Can't you cut point-size holes in opposite poles of a sphere and then bring the holes together and sew the neighborhoods of each hole together? Not that I'd expect something like this is literally happening in string theory, maybe it's more like a kind of uncertainty in the topology (and I think that topology changes are always 'shielded from view' by branes somehow) Also I wasn't aware "doughnut" was a technical term in mathematics, but from the context I thought it was clear that I meant the 2D surface, just like I used "sphere" to refer to a 2D surface rather than a solid 3D sphere.
IttyBittyBit
#15
Apr2-10, 07:54 PM
P: 159
Can't you cut point-size holes in opposite poles of a sphere and then bring the holes together and sew the neighborhoods of each hole together?
Exactly! the resulting object would be homeomorphic to a torus. But you have the additional 'sew' operation going on here, so it's not the same as just punching a hole in a sphere. The reason I brought this up is because while you and I may know what we are talking about, the OP might not, and thus might get confused about this.

Not that I'd expect something like this is literally happening in string theory, maybe it's more like a kind of uncertainty in the topology (and I think that topology changes are always 'shielded from view' by branes somehow) Also I wasn't aware "doughnut" was a technical term in mathematics, but from the context I thought it was clear that I meant the 2D surface, just like I used "sphere" to refer to a 2D surface rather than a solid 3D sphere.
It wasn't clear from context at all. Maybe I'm just an idiot, but I thought you were talking about solid objects, not surfaces.
Actually, you won't find the term 'doughnut' used much in math books. But still, people in math circles do use the term, and they usually take it to mean a 'filled' torus. Also, you used the word 'sphere' correctly. The solid interior would be called a ball, not a sphere.

About the string-theory part, I won't comment. I don't understand cohomology yet (even though I'm trying to!) so I don't think I'm qualified to express an opinion about string theory.
JesseM
#16
Apr2-10, 08:23 PM
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P: 8,470
Quote Quote by IttyBittyBit View Post
Exactly! the resulting object would be homeomorphic to a torus. But you have the additional 'sew' operation going on here, so it's not the same as just punching a hole in a sphere. The reason I brought this up is because while you and I may know what we are talking about, the OP might not, and thus might get confused about this.
Yeah, I did allude to "ripping /sewing spacetime" but I didn't mention the sewing part of converting a sphere to a torus, was speaking rather informally...appreciate the clarification.
Phrak
#17
Apr3-10, 12:48 AM
P: 4,512
Quote Quote by chroot View Post
There is no 'fabric' in any modern physical theory, so there is no 'fabric' to be ripped.

Phrases like "ripping a hole in the space-time continuum" are abuses of notation typically used in science fiction.

- Warren
The picture in the link clearly depicts a fabric. I believe it is what sailors call a scrim.
Naty1
#18
Apr3-10, 11:46 AM
P: 5,632
was speaking rather informally
yes, and I understood the context...and it was I believe on the plane of the posters apparent question...he/she did not ask for a mathematical description. On the other hand Itty makes some technical statements that I understand to be accurate, some I don't understand, but did not take the earlier posts to assert such a level of technical accuracy.

"ripping a hole in the space-time continuum" are abuses of notation typically used in science fiction.
a bit of an exaggeration, I think, but regardless of one's point of view, these are surely theoretical considerations, not experimantally observed ones so far.

You did not explain what you mean by 'singularity'. There are many different kinds of singularities in mathematics.
I was also posting in an informal way, but I surely do NOT know all types of singularities in mathematics...nor do I care to nor ever claimed to .....on the other hand I was referring to big bang and black holes singularities and posted that explicitly....

So if anyone knows of a paper that addresses these singulairites in a convincing way that relates to the observed physical world,in other words the singularities themselves rather than the nearby environs, I'm willing to read it....if I can understand it.....right now my understnading remains that our current QM and relativity theories fail at big bang and black hole singularities.....I believe they remain fundamentally still a mystery....at least so to me...

The last thing I am interested in on these forums is inserting myself into a mathematicians discussion about interpreting mathematics relevance to the physical world...there are just too many that don't seem to match our physical universe....so far...


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