# What Dimensions Are There (in Physics) ?

Gold Member
Hello;

I am curious about how many dimensions there are in physics. My physics teacher responded with '10 or 11'.

-1 dimension: ???
0th dimension: Fixed point
1st dimension: Line
2nd dimension: Flat plane
3rd dimension: Object with depth on a flat plane.
4th dimension: 3-dimensional with time
5th dimension: ???
6th dimension: ???
7th dimension: ???
8th dimension: ???
9th dimension: ???
10th dimension: ???
11th dimension: ???

I've tried googling it, but couldn't find any good answers...

Thanks.

James Leighe
I never thought about negative dimensions!

Anyway, you can think about the number of dimensions as how many numbers you need to represent a point in that space uniquely.

So, for a two dimensional space, to specify a point, I would need two numbers (lets say, x and y). You can probably see how this is generalized.

EDIT: As for answering your question... It depends on the physics you are doing. Physicists use anywhere from zero to infinite dimensions.

Gold Member
Okay... so are 0, 1, 2, 3, and 4-dimensional universally accepted by physics? Are those the only dimensions universally accepted?

Gold Member
EDIT: As for answering your question... It depends on the physics you are doing. Physicists use anywhere from zero to infinite dimensions.

I believe he means spatial/time dimensions

James Leighe
I believe he means spatial/time dimensions

In the standard model there are four.

The 10 to 11 dimensions your professor was talking about is from string theory, an (incomplete) contender for the theory of everything.

Superstring
String theory predicts 11 dimensions:

1. Up/Down
2. Forward/Backward
3. Left/Right
4. Time
5-11: Kaluza-Klein "curled up" dimensions.

http://en.wikipedia.org/wiki/Kaluza–Klein_theory

This is the easiest explanation I could find: