String theory

[steve 9]

I think that brane theory depends on multiple spatial dimensions being real. But it also implies that exploring or proving these spatial dimensions would take more energy than we can cause to come together in a small space such as an accelerator. But it does imply that such a proof may be possible at some point.

 

 

Lets keep this simple, what evidence is there of the first three dimension being physical things?

[Moontanman]

Lets keep this simple, what evidence is there of the first three dimension being physical things?

 

I'm not sure anyone is saying that the spatial dimensions we know of are physical things in the same way that a star or a planet or an atom is a physical thing. Other than taking up space? I'll have to give this some thought.

[jedaisoul]

Lets keep this simple, what evidence is there of the first three dimension being physical things?

The evidence is, literally, all around us...

 

Dimensions, like frames of reference, are abstract concepts. But, material objects have physical size. So, if we accept that material objects exist, it is logical to accept that their size physically exists.

 

From there, it's not a great leap to accept that the distances between material objects physically exist. E.g. If you imagine three rods placed in a line touching at the ends, the distance between the two end rods is defined by the middle rod. Then remove the middle rod. The relationship between the remaining two is unchanged. So the distance between them exists just as much as the rod that formally occupied that position.

 

Both the size of material objects and the distances betwen them are three dimensional, and material objects can freely change the relationships between them (i.e. they can "move in those dimensions"). So we say that space is three dimensional. This does not mean that space, or those dimensions, exist. They are abstract representations of the physical relationships of and between material objects (which do exist).

 

Does that make sense?

[coldcreation]

Why is the number of dimensions in string theory so specific? Does it not seem like scientists are 'making up' the theory of extra dimensions because they cannot explain why the force of gravity is so weak compared to the other fundamental forces. The idea of miniscule undetectable universes present in our own seems to have derived from nowhere.

 

 

The totality of string theory’s separation from nature would hardly be fulfilled had the universe not concealed a key ingredient: additional curled-up spatial dimensions. As it turns out, string theory cannot do without extra space dimensions. Why not, articulates Brian Greene, “so long as they are small enough, nothing rules them out.” The problem with this conjecture is that nothing rules them in either. This is a case where nothing is more real than nothing.

 

Greene spans on to say; “But extra dimensions may strike you as an artifice. Our inability to probe distances smaller than a billionth of a billionth of a meter permits not only extra tiny dimensions but all manner of whimsical possibilities as well—even a microscopic civilization populated by even tinier green people. While the former certainly seems more rationally motivated than the latter, the act of postulating either of these experimentally untested—and, at present, untestable—possibilities might seem equally arbitrary.” (Greene, B. 1999, The Elegant Universe, Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory).

 

 

Clearly string theory is a mathematical oasis, separated from the rest of physics.

 

CC

[steve 9]

I'm not sure anyone is saying that the spatial dimensions we know of are physical things in the same way that a star or a planet or an atom is a physical thing. Other than taking up space? I'll have to give this some thought.

 

I just want to be clear here, are you saying that the first three dimensions take up space?

[steve 9]

The evidence is, literally, all around us...

 

Dimensions, like frames of reference, are abstract concepts. But, material objects have physical size. So, if we accept that material objects exist, it is logical to accept that their size physically exists.

 

From there, it's not a great leap to accept that the distances between material objects physically exist. E.g. If you imagine three rods placed in a line touching at the ends, the distance between the two end rods is defined by the middle rod. Then remove the middle rod. The relationship between the remaining two is unchanged. So the distance between them exists just as much as the rod that formally occupied that position.

 

 

 

So you say distances physically exist. Of course my next question would be, physically exist in what form? Matter or energy?

 

Lets have some fun with what you are suggesting. Like you said, we take three rods and lay them in a line and remove the middle rod. Now you want to suggest that in place of that missing rod a different physical thing is now occupying that area of the missing rod. So I would have to ask how did this new physical thing get there? How fast did it travel to fill the void? Where was this physical thing before the rod was removed? I could go on.

 

Now also in your three rods example, when you put that middle rod back to its original location, are you squishing the space out, pushing it out, how does this space move out of the way? And how hard is this space?

 

Both the size of material objects and the distances betwen them are three dimensional, and material objects can freely change the relationships between them (i.e. they can "move in those dimensions"). So we say that space is three dimensional. This does not mean that space, or those dimensions, exist. They are abstract representations of the physical relationships of and between material objects (which do exist).

 

Does that make sense?

 

Before we discuss this any further, I want to be clear, do you think space is a physical thing as you suggested in your post?

[steve 9]

The totality of string theory’s separation from nature would hardly be fulfilled had the universe not concealed a key ingredient: additional curled-up spatial dimensions. As it turns out, string theory cannot do without extra space dimensions. Why not, articulates Brian Greene, “so long as they are small enough, nothing rules them out.” The problem with this conjecture is that nothing rules them in either. This is a case where nothing is more real than nothing.

 

Greene spans on to say; “But extra dimensions may strike you as an artifice. Our inability to probe distances smaller than a billionth of a billionth of a meter permits not only extra tiny dimensions but all manner of whimsical possibilities as well—even a microscopic civilization populated by even tinier green people. While the former certainly seems more rationally motivated than the latter, the act of postulating either of these experimentally untested—and, at present, untestable—possibilities might seem equally arbitrary.” (Greene, B. 1999, The Elegant Universe, Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory).

 

 

Clearly string theory is a mathematical oasis, separated from the rest of physics.

 

CC

 

Thank You. Nicely put.

[freeztar]

Clearly string theory is a mathematical oasis, separated from the rest of physics.

 

How so?

[Moontanman]

I just want to be clear here, are you saying that the first three dimensions take up space?

 

They are space.

[steve 9]

Originally Posted by coldcreation

Clearly string theory is a mathematical oasis, separated from the rest of physics.

 

How so?

 

No one has shown any physical or observational data that provides evidence of extra dimensions. It is all based on numbers on paper and that is as far as it goes.

 

If you have any data or evidence of the existance of extra dimensions please let me know, I am always willing to learn more about this subject.

 

Thank You.

 

Steve 9

[steve 9]

Originally Posted by steve 9

I just want to be clear here, are you saying that the first three dimensions take up space?

 

They are space.

 

O.K. So dimensions are space. If you would not mind, could you tell me a bit more about this, I know that space is that area of nothing between objects, but I thought dimensions were some what different that just plain space. Is there a difference or are they interchangable?

 

Thank You.

 

steve 9

[jedaisoul]

The evidence is, literally, all around us...

 

Dimensions, like frames of reference, are abstract concepts. But, material objects have physical size. So, if we accept that material objects exist, it is logical to accept that their size physically exists.

 

From there, it's not a great leap to accept that the distances between material objects physically exist. E.g. If you imagine three rods placed in a line touching at the ends, the distance between the two end rods is defined by the middle rod. Then remove the middle rod. The relationship between the remaining two is unchanged. So the distance between them exists just as much as the rod that formally occupied that position.

So you say distances physically exist. Of course my next question would be, physically exist in what form? Matter or energy?

Neither. They exist as properties of physical objects. I quote Einstein: "I wish to show that space-time is not something to which one can ascribe a separate existence, independently of tha actual objects of physical reality. Physical objects are not in space, but these objects are spatially extended. In this way, the concept 'empty space' loses it's meaning". A Einstein, Note to the 15th Edition of "Relativity the Special and the General Theory" 1952.

 

Lets have some fun with what you are suggesting. Like you said, we take three rods and lay them in a line and remove the middle rod. Now you want to suggest that in place of that missing rod a different physical thing is now occupying that area of the missing rod.

No I did not say that. I said that the relationship between the two outer rods remains the same. There is no "different physical thing... now occupying that area of the missing rod".

 

So I would have to ask how did this new physical thing get there? How fast did it travel to fill the void? Where was this physical thing before the rod was removed? I could go on.

 

Now also in your three rods example, when you put that middle rod back to its original location, are you squishing the space out, pushing it out, how does this space move out of the way? And how hard is this space?

See above. These qustions are meaningless.

 

Before we discuss this any further, I want to be clear, do you think space is a physical thing as you suggested in your post?

I repeat, space is not a physical entity. It is a property of physical entities. It has no separate existence.