# Why dimensions?

1. Feb 7, 2008

### wolram

Why is it that it is thought that separate dimensions exist, as humans we can only exist in
a volume, three so called dimensions, so why do scientists think that these three can be separated when in all probability and experimental AFAIK they can not, length, width and
depth are just words to describe the size of a volume, put some particles in motion in a
volume and you have what you see in the universe.
As for extra dimensions, well time will tell but i think it is all mathematical mumbo jumbo,
but then may be some one can come along and take the width or the length or the depth
out of a volume, that would be a neat demo.

2. Feb 7, 2008

### TVP45

I think a better way is to think of the 3D dimensions as independent rather than separate.

BTW, I have an example of 2D. I own a house lot of approximately 10,000 ft^2. I paid a mortgage on it. I pay taxes on it. It is recorded in the Deeds and Tax Offices. I can do almost anything I like on it, so it is real in an everyday sense. But, I own only a 2D surface. There is no depth.

3. Feb 7, 2008

### wolram

Do you grow 2D veg in this garden?

4. Feb 7, 2008

### TVP45

Mainly flat cabbage and plane trees.

5. Feb 8, 2008

### wysard

Why do you think "seperate" dimensions exist? They are a mechanism to seperate out vector forces but they are far from seperate. Each one interacts with the other through the body under consideration. We develop them to answer questions to resolve questions that cannot be answered any other way but still observe all the rules of physics we know. You should note that all the dimensions obey the same laws of physics, it's not as if there is a magical seperate reality for any dimension. Force is still force, entropy is still entropy, all laws apply equally. Think of it as an advanced application of Occam's Razor. Or, the less sexy side of "And he built a crooked house".

6. Feb 8, 2008

### wolram

Seperate dimensions do not exist in the real world, in a volume lenght width and breadth are inter changable, one can give a prefered direction some value but what ever it is an artificial value in a volume

7. Feb 8, 2008

### sysreset

Wolram I am right with you on this. Describing space as 3- dimensional is arbitrary and based on the mathematical convenience of cartesian or spherical coordinates. This is especially apparent when one considers the vast differences in how space behaves within graviational clusters (where it is not expanding) and outside gravitational clusters (where it is expanding). I think the fundamental flaw is that we describe space itself, and objects with mass within space with the same 3-dimensional paradigm.

Certainly 3 dimensions is an extremely elegant and convenient tool when describing the relative positions of objects within gravitational systems. Length, width, height; or if you prefer, radius, zenith, azimuth. Both are based on the fact that coordinates oriented 90 degrees apart give static positions with the fewest number of elements. But relying on 90 degrees, and relying on the fewest elements, are both artificial selections and other artificial systems can be constructed mathematically. None of these artificial constructs alters the true nature of empty space or space with mass, and all of these constructs falsely blur the distinct characteristics of empty space versus space with mass. And all of these "dimensional" constructs inadvertently leave out motion and acceleration, which have such profound affects.

8. Feb 8, 2008

### CaptainQuasar

Dimension is just shorthand for a (mathematical) degree of freedom.

9. Feb 9, 2008

### f-h

yep. Maximum number of linearly independent vectors. It implies that the relative location of two bodies can always be described by three numbers. That's all, there is nothing separate about the directions as you might tell by the fact that our up is the sideways of somebody a quarter around the globe.

10. Feb 9, 2008

### dx

dimensions are how our minds organize what are called spatial relationships between objects. it turns out that on the large scale, the spatial relationship between two objects always need 3 numbers to specify. it could quite possibly be different on differnt scales.

11. Feb 9, 2008

### wolram

Thank you sysreset, you put the case much better than i could.

12. Feb 9, 2008

### malawi_glenn

depends on what you mean by "real" world..

13. Feb 9, 2008

### wolram

malawi, i mean a world were we exist, not a mathematical world where many things CAN
exist

14. Feb 9, 2008

### malawi_glenn

and how do you KNOW that the real world only have 3spatial dimensions?

15. Feb 9, 2008

### Haelfix

Some of the large extra dimension models currently in vogue in phenomenology are quite physical, in the sense that they are consistent with observation.

16. Feb 9, 2008

### wolram

I am arguing that dimension means very little (three spacial dimensions) is not meaning full
we live in a volume, we can not live in 2D or 1D, so what is the use of extra dimensions, if
they are included in the volume they are not separate entities ,they just emerge from
abstract maths.

17. Feb 9, 2008

### malawi_glenn

But the language of physics is math, not intuitive reasoning.

Elementary particles are point like, they have no internal structure nor volume according to best theories and observations (see many threads in this forum).

The whole quantum physics is full of things that contraditcs our daily life experince, so we can not a priori rule out everything that contradicts our daily life experience as non-physical.

So we cant just say "its only absract math"..

18. Feb 9, 2008

### wolram

Malawi, i agree the world of quantum physics is not intuitive (from what very little i know)
But to try for example to describe gravity as a weak force because it leaks into some other dimension seems a cop out when dimension has no real meaning.

19. Feb 9, 2008

### malawi_glenn

So even tough you have very little knowledge about quantum physics, you have much to say about the very frontline in quantum physics, namley String Theory. That is strange..

20. Feb 9, 2008

### wolram

Quite true i know very little, but i have the right to question, and i notice that no one has yet explained how a dimension can be individual.