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According to Brian Greene's book, The Elegant Universe, page 329, "... a three-dimensional sphere inside a Calabi-Yah space can collapse without an ensuring disaster, because a three-brane wrapped around it provides a perfect protective shield." Then on page 324, he writes: "... the three-brane can wrap around and completely cover a three-dimensional sphere. ... a three-brane has three extended dimensions." Then, on his CDs, he ask the question: could our universe be a three-brane?

So, is a three-brane small like the Planck distant or somehow large like our universe? And, what would cause space to rip or tear in the first place?

2007-08-26 13:13:11 · 1 answers · asked by Bob D1 7 in Science & Mathematics Physics

If String/M-theory ... math allows for ... either very, very small ... or very, very large branes, might this suggest some sort of "duality"? Kind of like, if you take a handlens and focus the light from the sun onto the surface of an object, no information is lost. If a sun-spot suddenly occurs on the sun's surface, it will also appear vise the handlens in the focused spot, only greatly reduced in size. It is a kind of duality, the same information in the large reflected in the very small. Maybe something like that happens with branes. After all, the duality between classical physics and quantum mechanics can be observed everywhere in nature, I think.

2007-08-27 01:46:32 · update #1

1 answers

So, is a three-brane small like the Planck distant or somehow large like our universe? And, what would cause space to rip or tear in the first place?

The answer is...yes.

String/M theory has not resolved this issue. Popular belief is that the branes are very very tiny (Plank size). But the math also allows for the possibility that they are very very large. Our universe may be one for example.

Very big or very small hinges on a constant of proportionality that, unfortunately, no one has figured a value for. So they plug in a number. If the number is one value, the Plank world pops out of the equations. If the number is another value, the mega-universe world pops out for the branes.

It's been a while since I read "Elegant Universe," but I vaguely recall Greene went into this. Go back and read about branes again; I think you will find a detailed answer to your question.

As to what might cause a tear in space, consider this...Suppose there are parallel universes made up of the fabric of the universe (See Greene's "Fabric of the Cosmos.") Suppose they are separated by a Plank length and Plank time. Suppose their fabric is made up of strings.

Somehow, that Plank length and time between two parallel universes is crossed. Then they collide. Their momenta change, releasing unimaginable energy as the force of collision rebounds the colliding universes.

I think that might rip the fabric and, further, I think that rip would pour unimaginable energy into both universes. We would see that as two big bangs, one in each universe. This is consistent with what we suspect of our own big bang. That is, it was unimagineably hot indicating very high energy and, like strings, that initial energy existed in dimensions higher than the four dimensions we now have in our extended universe.

2007-08-26 13:53:37 · answer #1 · answered by oldprof 7 · 1 0

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