# 3 dimensions

1. Jul 8, 2010

### tanzanos

Why do we call them 3 dimensions when all that they are, are just the ability of movement in space? Physical movement cannot be restrained in any vector. It takes place in a 3 dimensional dimension. Thus 1 dimension is physical movement in space and the second dimension is time. Within the 1st dimension movement can take place in any direction.

If we are to assume that time requires movement and thus change then how is it possible for movement to occur in a timeless void. Which comes first; movement and thus time or time and thus movement. Both cannot be true for: Without change time cannot exist and without time change cannot exist.

In a void, time cannot exist and thus movement is impossible; But a void is needed in order for movement to be possible.

This has me perplexed and somehow I cannot grasp the differentiating time from movement. Since the physical world cannot exist without either time nor movement than is time and the ability of movement one and the same?

2. Jul 8, 2010

### AJ Bentley

You're reading more into a word than is really there.

Dimension is from a latin word meaning measure or extent.
Since it's possible to measure in 3 directions up-down left-right and fore-backwards and that in many situations we can usefully treat them as separate (each independent of the others), we say there are 3 dimensions.

Time came along later. That is, we recognised it as a dimension of it's own later. Initially no-one realised just how much like the other 3 it was - it was just convenient to call it a dimension. (When drawing graphs of timed events for example)

When Einstein pointed out it was exactly the same - well - everyone was gobsmacked!

They're just words.