1. A model that physicists like to use to explain Einstein's theory of spacetime curvature (as a result of the merger of gravity and General Relativity) is the elastic space model. In it, you have an xy coordinate grid made of some elastic substance, such as rubber, and you put ping pong balls on the grid. The ping pong balls sink into the elastic material, and represent planets. Then, you put a bowling ball in the middle, and all the ping pong balls fall into the bowling ball due to gravity. It illustrates that gravity is a result of the curvature of space and time. aka spacetime, rather than a traditional force of attraction such as opposite charges.

However, this illustration is only legitimate because of the third spatial dimension, the z axis. If the two dimensions didn't have a third dimension to "curve" into, this illustration would be meaningless.

So my question: Is this where we enter the seven other spatial dimensions, whereas these seven dimensions provide the space for the other three dimensions to curve?

2.

3. The idea of ten spatial dimensions comes from string theory, or one version of string theory. No one can say for sure if there really are ten such dimensions, or eleven, or some other number. In any case, these extra dimensions, if they exist at all, are down around atomic lengths. You cannot apply them to macroscopic systems, or so I understand.

The rubber sheet model has nothing to do with string theory, or any other true mathematical model. It is merely a crude picture for laymen. It suggests to the non-mathematician how mass can distort spacetime, and that gravity can be thought of as merely a side effect arising from this distortion. It has no relation to reality.

4. Then where did we get these seven spatial dimensions? I understand it was from String Theory, but what was the mathematical logic of the string theorists that they used to justify the conclusion of ten spatial dimensions?

5. Steve F, I would agree with everything you say, except that the rubber sheet analogy has a relationship to reality in that it is a 2-D analogy of 3-D space and demonstrates the concept of gravity as warped spacetime. It does have its limitations as a crude picture for laymen, as you say, but as it seems impossible to imagine 3-D warped space, I think it has its usefulness.

Here's an interesting link to the subject of gravity, about half way down the page are posed further questions about gravity as warped spacetime and the legitimacy or not of the rubber sheet analogy.

http://metaresearch.org/cosmology/speed_of_gravity.asp

6. davidstebbins---

The "extra" dimensions in string theory are a consequence of quantum consistency. If one assumes the fundamental object in a theory is a string, and then quantizes the theory, one finds that to get a theory consistent with quantum mechanics, we must have 9+1 or 10+1 dimensions.

7. Originally Posted by BenTheMan
davidstebbins---

The "extra" dimensions in string theory are a consequence of quantum consistency. If one assumes the fundamental object in a theory is a string, and then quantizes the theory, one finds that to get a theory consistent with quantum mechanics, we must have 9+1 or 10+1 dimensions.
So it's just a matter of the fact that these dimensions are needed for the mathematics of String Theory to fall into place?

8. Originally Posted by davidstebbins
A model that physicists like to use to explain Einstein's theory of spacetime curvature (as a result of the merger of gravity and General Relativity) is the elastic space model. In it, you have an xy coordinate grid made of some elastic substance, such as rubber, and you put ping pong balls on the grid. The ping pong balls sink into the elastic material, and represent planets. Then, you put a bowling ball in the middle, and all the ping pong balls fall into the bowling ball due to gravity. It illustrates that gravity is a result of the curvature of space and time. aka spacetime, rather than a traditional force of attraction such as opposite charges.

However, this illustration is only legitimate because of the third spatial dimension, the z axis. If the two dimensions didn't have a third dimension to "curve" into, this illustration would be meaningless.

So my question: Is this where we enter the seven other spatial dimensions, whereas these seven dimensions provide the space for the other three dimensions to curve?
The rubber sheet analogy is pointless and laughable. They are trying to explain how gravity exists by, erm using gravity ???

Okay....put that rubber sheet floating in space, and stick the same balls on it.

now what ?

If mass did curve space time then the simplist of all experiments in micro-gravity would be to indeed have a bowling ball placed in the vacuum of space on top of a sheet of cling film. If the cling film wrapped itself round the bowling ball, you could bet that indeed space time is curved. If it didnt, youd have to find some other explanation for gravity.

9. Originally Posted by leohopkins
The rubber sheet analogy is pointless and laughable. They are trying to explain how gravity exists by, erm using gravity ???
Its an analogy - so what exactly is your objection?

Dave---More or less, yes. The nice thing is, though, string theory PREDICTS 10 or 11 dimensions. In all other theories we have, people put the number of dimensions in by hand.

11. Originally Posted by davidstebbins
So it's just a matter of the fact that these dimensions are needed for the mathematics of String Theory to fall into place?
So is no one going to answer this?

12. Originally Posted by davidstebbins
Originally Posted by davidstebbins
So it's just a matter of the fact that these dimensions are needed for the mathematics of String Theory to fall into place?
So is no one going to answer this?
It was answered, for string theory to be consistent it demands 9+1 or 10+1 dimensions. Most other theories let you add the dimensions in by hand.

13. Originally Posted by river_rat
Originally Posted by davidstebbins
Originally Posted by davidstebbins
So it's just a matter of the fact that these dimensions are needed for the mathematics of String Theory to fall into place?
So is no one going to answer this?
It was answered, for string theory to be consistent it demands 9+1 or 10+1 dimensions. Most other theories let you add the dimensions in by hand.
I was trying to put it in my own words: String theory uses the unit of m^10, with one s dimension, so these seven extra dimensions are present only in the equations. Is that it?

14. String theory uses the unit of m^10, with one s dimension, so these seven extra dimensions are present only in the equations. Is that it?
I am a bit confused. What do you mean ``contained only in the equations''?

15. Originally Posted by BenTheMan
String theory uses the unit of m^10, with one s dimension, so these seven extra dimensions are present only in the equations. Is that it?
I am a bit confused. What do you mean ``contained only in the equations''?
Perhaps I'm getting a little ahead of myself. Could you give me th five String Theories' equations, because I've never seen them? Perhaps then I can explain to you what I mean.

16. How much math do you know. I don't know how useful it'd be...

17. Plus there's no LaTeX in this forum, so it would be totally ugly to try and write out equations.

18. Well, I just got out of high school, but I know that all the more complicated maths are just build-ups of basic math, so maybe I can figure it out.

Besides, what have either of us got to loose for trying?

19. I'll see if I can find some equations somewhere on-line. If this forum had a TeX builder, I could type them here, but that's not an option.

stand by...

20. I've got all year.

21. Originally Posted by davidstebbins
Originally Posted by river_rat
Originally Posted by davidstebbins
Originally Posted by davidstebbins
So it's just a matter of the fact that these dimensions are needed for the mathematics of String Theory to fall into place?
So is no one going to answer this?
It was answered, for string theory to be consistent it demands 9+1 or 10+1 dimensions. Most other theories let you add the dimensions in by hand.
I was trying to put it in my own words: String theory uses the unit of m^10, with one s dimension, so these seven extra dimensions are present only in the equations. Is that it?
Yes thats it, so far we have nothing more than math to show for these dimensions, BUT experiments might show for them soon, or perhaps never . . .

CERN emm cant wait till she be online. If indeed strings are a great deal larger then the planck length if indeed we are able to create ultra small black holes with the new atom smasher if indeed we do prove supersymmetry then yes we will have good evidence that these Calabi-Yau spaces exist and are apart of our spacetime fabric.

22. X=, are you not a native English-speaker or something?

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