# Dispute between Relativity and String Theory?

• Barfield
In summary, "The Elegant Universe" discusses the concept of relativity and the velocity of objects in different dimensions, particularly for light. It then introduces String Theory, which suggests that there are 10 dimensions and that strings require 6 additional dimensions to resonate correctly. However, this raises the question of how a photon can travel at the speed of light if its energy is being expended in the additional dimensions. The conversation also touches on the difference between space and time dimensions and the possibility of objects existing in multiple states at the same time.
Barfield
Regarding "The Elegant Universe", page 48-50:

Relativity says that all objects have a velocity of c. For most objects most of this velocity is in the time dimension. For light, none of this velocity is in the time dimension but one of the other 3 (x,y,z). For an object to give all of this "dimensional energy" to just 1 dimension means the object will have a velocity of c in that dimension.

Now enter String Theory, which says there are 10 dimensions. A string requires the additional 6 dimensions in order to resonate correctly (to output a photon for example).

Here's the problem:

If a string has to vibrate in the additional 6 dimensions, then some of its energy is being expended in those dimensions. Meaning that a photon cannot give all its energy to just 1 dimension (ie, straight forward, the x dimension). That means that a photon cannot travel the speed of light in x, y, or z because of the energy expended in the "other 6" dimensions...

Where am I going wrong here? Light has to move at c!

Yes. But that is because photons are small enough to be inside the 10 dimensions of string theory. Because photons are strings, they vibrate in the 9 espacial dimensions. Photons may not be able to go at the speed of light, but becuase they are actually in a 10 dimensional world and not in a 4 dimensional (3+time) they can go at the speed of light at these higher dimension number.

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Its not the speed you would need to be worried about, but rather the electromagnetic interaction, since the photon mediates this as a gauge boson. Naively you would expect a suppression factor in the Coulomb term if indeed that mode was allowed to resonate in higher dimensions. Of course it could be that there *is* just such a thing, we'd have to be able to measure the constants down to the Planck scale in order to see a deviation. But as far as I know, most models of Stringy physics explicitly prevents such a thing from occurring, only gravity propagates in the compactified dimensions..

<<<GUILLE>>> said:
Yes. But that is because photons are small enough to be inside the 10 dimensions of string theory. Because photons are strings, they vibrate in the 9 espacial dimensions. Photons may not be able to go at the speed of light, but becuase they are actually in a 10 dimensional world and not in a 4 dimensional (3+time) they can go at the speed of light at these higher dimension number.

You say 3 space and 1 time, but there's really nno evidence of them being any different, we just percieve them differently.

yomamma said:
You say 3 space and 1 time, but there's really nno evidence of them being any different, we just percieve them differently.

TRUE, and we probably concieve them diffeently becuase we aren't uosed to traveling in time.

You say 3 space and 1 time, but there's really nno evidence of them being any different, we just percieve them differently.

You are trying to express a sophisticated point; but instead your statement has no meaning. For example; it makes sense to say that an object is at the same place at two different times while it is impossible for something to be in the same time at two different places.

The time dimension is very unlike the spatial dimensions, but the distinction has to do with curvature (cone centered on the time axis). In general, dimensions are not divided into space or time, they just have various curvatures (some of which we interpret as time, or space).

Well put, Crosson. Four dimensional vectors can freely move through 3D space without appearing to move [or even exist] from the perspective of any 3D observer.

Crosson said:
For example; it makes sense to say that an object is at the same place at two different times while it is impossible for something to be in the same time at two different places.

The apparent "same place" is, though, relative to the person who is making the statement (since things continually change). Concerning the impossibility of something to be "in the same time at two different places," doesn't this come up in the Heisenberg uncertainty principle, where things can be in superpositions? This would mean that it is intrinsically possible that an object can be in two places at the same time due to superpositions.

It is logically and semantically impossible for one thing to be in two different distinct places at exactly the exact time. Why? Because it would then be TWO things instead of one thing.

It is possible for one thing to empirically appear to be two places at the same time if it transitions between the two location is fast enough.

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Well, if something isn't observered/measured, can it not be in two or more states at the same time? Because of the lack of information of the observer/measurer of an object, can't the object be said to be at various superposition states at the same time, such as Schrodinger's cat? When the observer/measurer makes an observation/measurement of the object, then do such states collapse into a single state.

Sempiternity said:
Well, if something isn't observered/measured, can it not be in two or more states at the same time? Because of the lack of information of the observer/measurer of an object, can't the object be said to be at various superposition states at the same time, such as Schrodinger's cat? When the observer/measurer makes an observation/measurement of the object, then do such states collapse into a single state.

Sure, something can be into two different places at the same time but it than becomes two different things. 1 never equals 2 (unless you make them variables, but then the concept of 1 as a constant and 2 as a constant have no meaning.)

## 1. What is the main difference between Relativity and String Theory?

The main difference between Relativity and String Theory is their approach to understanding the laws of physics. Relativity is a classical theory that explains the behavior of objects in the macroscopic world, while String Theory is a quantum theory that aims to unify all the fundamental forces of nature.

## 2. Can Relativity and String Theory be reconciled?

There is currently no consensus on whether Relativity and String Theory can be reconciled. Some scientists believe that String Theory can incorporate the principles of Relativity, while others argue that the two theories are fundamentally incompatible.

## 3. What evidence supports Relativity and String Theory?

Relativity has been extensively tested and confirmed through various experiments, including the famous Eddington expedition to observe the bending of light during a solar eclipse. As for String Theory, there is currently no direct experimental evidence, but it offers a potential solution to some of the unresolved problems in physics, such as the unification of gravity with other forces.

## 4. How does String Theory explain the concept of spacetime?

In String Theory, spacetime is seen as a dynamic entity rather than a fixed background. The theory proposes that the fabric of spacetime is made up of tiny, vibrating strings, which give rise to the fundamental particles and forces of nature. This concept is in contrast to Relativity, which describes spacetime as a smooth and continuous four-dimensional space.

## 5. Is one theory more widely accepted than the other?

Relativity is considered one of the most successful theories in modern physics and has been extensively tested and confirmed. On the other hand, String Theory is still a developing and highly debated theory, with some scientists arguing for its potential and others questioning its validity. Therefore, it is difficult to say which theory is more widely accepted at this time.

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