
#1
Apr110, 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?




#2
Apr110, 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 spacetime continuum" are abuses of notation typically used in science fiction.  Warren 



#3
Apr110, 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 



#4
Apr110, 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 



#5
Apr110, 07:01 PM

P: 5,634

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.
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 spacetime" 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 HawkingHartle 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... 



#6
Apr110, 07:12 PM

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P: 8,004

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/astroph/0012345 "spacetime fabric" http://arxiv.org/abs/grqc/0508121 "fabric of spacetime" 



#7
Apr110, 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.




#8
Apr110, 10:28 PM

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P: 8,004

http://arxiv.org/abs/hepth/9109030, http://iopscience.iop.org/02649381/8/4/007/ "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?" 



#9
Apr210, 12:02 PM

P: 5,634

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 CalabiYau 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. 



#10
Apr210, 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 mathrelated comments though.




#11
Apr210, 06:13 PM

P: 5,634

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." 



#12
Apr210, 06:17 PM

P: 5,634

thanks 



#13
Apr210, 06:55 PM

P: 159

First of all, a sphere is a 2dimensional manifold and a doughnut is a 3dimensional 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 2dimensional manifold. So is a torus. A sphere with a single point removed is an open 2dimensional manifold. You can't construct a homeomorphism from an open manifold to a closed one. 



#14
Apr210, 07:26 PM

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#15
Apr210, 07:54 PM

P: 159

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 stringtheory 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. 



#16
Apr210, 08:23 PM

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#17
Apr310, 12:48 AM

P: 4,513





#18
Apr310, 11:46 AM

P: 5,634

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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