# Idea with physics Dimension

1. Oct 26, 2005

### minase

I'm just curious to see what other people in this group have to say about this theory I have. I used to think that time was the fourth
dimension. It seemed pretty logical due to the way dimensions are built up. The zero dimension is a point, the first dimension is an
infinite number of points extended into the first dimension (or a line). The second dimension is an infinite number of lines extended
into the second dimension (or a plane). The third dimension is an infinite number of planes extended into the third dimension (or a cube or any other 3d object). Now if you extend a bunch of 3D spaces into a fourth direction I would have thought that you'd have a timeline (each 3D space would be a single moment on that timeline). Recently, however I have changed my mind. In order for something to qualify as a dimension it seems that you need to be able to move backwards and forwards through it. Now of course we can move forward in time but moving backward is not so obvious. But even if we did have a time machine and tried to move back in time, the time traveler would go back in time too! All the atoms in my body would move backward in time as a result of me moving backwards in the fourth dimension (assuming it's time) which means that moving backwards in time would be the same as age regression so the farthest you could go back would be the time you were born. Thus time can't be the fourth dimension. In the first three dimensions I can go backwards and forwards through them indefinitely (assuming an infinite universe), so if time is the fourth dimension why the limit all of a sudden? I think instead that the fourth dimension is something else. What that something else is though, who knows....possibly something's internal rate of vibration? I have not a clue. Any comments would be appreciated.

Last edited: Oct 26, 2005
2. Oct 26, 2005

### Danger

As far as I know, time is still considered the 4th. I've never seen a law stating that you have to be able to move at all in a dimension. The extra dimensions seem to be thought of as 'curled up' in tiny areas.

3. Oct 26, 2005

### ZapperZ

Staff Emeritus
Have you ever considered that maybe the criteria you are using to consider something as a "dimension" is meaningless in physics?

For example, what exactly is the outcome of such consideration? Does it help us define certain things better? Does it provide a profound insight into certain phenomena? More importantly, does it WORK when applied to the description of the dynamics of a system?

Without those considerations, all we have are just a jumble of words on how things are defined, without connection to anything important.

Zz.