I saw

Back to the Future on TV the other day, and as always when I see

time travel movies, I get thinking about the

metaphysical concepts they unknowingly insert in such things.

My theory is that there are really five dimensions that we, as humans, can perceive. The catch is that our perception of the fourth is limited severely, and we have yet to develop a means of perceiving the fifth as any different from the fourth.

Ok, imagine a straight line. You can travel left and right on it. Dexter and Sinister. Points can occur on any place on the line.

Dimension 2 is if you were to expand the possible locations of the line. To make this jump assuming a lack of 2D perception, think of perceiving space other than the line. Before you do this, you can only perceive points on the line, Now, though, whatever direction you move the point, you now have a second axis. The two axes make basically a cartestian coordinate system. You can now move the point up, down, left, and right. A map, basically. A Super Nintendo RPG.

The third dimension can be obtained in the same method as the second. Perceive space outside the coordinate system. Imagine it on a flat page and then imagine looking at it eye level. Then imagine the point floating above the page. You now have 3 dimensions. The way we see the world.

Now, we come to time, the 4th dimension. Many people will argue that the 4th dimension is spatial, not temporal, but for us, the humans, there is no spatial dimension beyond the third. Much as game developers wish there was, there is not. But another axis can still be added. Try to visualize the 3D cube being again expanded. Difficult? Well, you can't do it, because your brain is not programmed for it. But the concept can be thought of in the same way we expanded the other dimensions. Image the cube as it exists now, in this when. Now imagine it an hour from now. See, time continues linearly, like a line.

To make it easier, image the delta factor, the change. If you move our point along it's 1D axis, you change the possible solution set of all the other axes. If you move it one to the left, the whole set moves over one to the left. You've eliminated an infinite number of past and future possiblities, yet created another infinite number of unique ones.

See how it applies to time? When we time travel, in theory, and meet our mother and cause her not to fall in love with our father, we cease to exist, we no longer fall within the solution set of the plane. So it's possible, using the linear time theory, to figure out (through same insane mathematic equation beyond our comprehension) what the world would be like given the change of a certain factor in the past. Think what use this would be to historians! The Roman empire never fell, what would the world be like? With this equation you could find out.

Now, here's where it gets tough. Expand time again and you have the fifth dimension, real time. Just as spatial figures exist within linear time, linear time exists within real time. When you travel back in time, you have memories of being in your own time. In Chrono Trigger, assuming your characters could talk, they would recall being in 1000 AD, then going back to 600 AD. They would recall the order in which they did it. This is the time that marches on despite the changing of or motion through linear time.

As of yet, we cannot bend linear time into a different shape than real time, so we cannot perceive real time as any different from linear time. We can imagine the perception of it, though, so it is still not a concept out of our reach.

The theory is that you need a higher dimension to effect change on a lower dimension, so the fifth dimension is unchangeable, unlike the other four. Unchangeable for us, since we cannot make use of the sixth or higher dimension.

Whew. Metaphysical rant mode: *Off*