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.