Fourth Dimension Explained

There has been question about the 4th dimension, so I will try to explain it.

Spacetime is a model that combines space and time into a single coordinate system called the space-time continuum. In our universe, this continuum has three dimensions of space and one dimension of time. Here, time is expressed in the same units as space by multiplying time measurements by the speed of light. Since the observed speed of light varies based on gravity, so does time vary.

The spacetime in which we live appears to be 5-dimensional with three spatial dimensions (i.e. width times height times depth), one of time, and infinity. From a particular point in space, the basic directions in which we can move are up/down, left/right, and forward/backward. Movement in any other direction can be expressed in terms of just these three. Moving down is the same as moving up a negative amount. Moving diagonally upward and forward is just as the name of the direction implies; i.e., moving in a linear combination of up and forward.

Time is referred to as the fourth dimension. It is how we measure physical change. It is different from the three spatial dimensions in that there is only one of it, and movement seems to be possible in only one direction. However, speed in this direction can very, because of the relation of space and time (the famous twins paradox illustrates this perfectly).

The total number of dimensions that exist has been widely debated. This is because certain obvservable data can only be explained if there are exactly, say, 9 dimensions. Another observed set of data can only be explained if there are, say, 12 dimensions. For instance, the String Theory suggests that our universe consists of at least ten spatial dimensions, of which three are the familiar spatial dimensions, six are compact dimensions curled up too small to be detected, and one (or more) are temporal dimension(s). The desire to create a "unified theory of everything" causes scientists to debate these things, as a unified theory cannot exist until a definite amount of dimensions can be determined.

However, because of obvserved empirical data, there is at least 5 dimesions. My appologies for the parts of this that were copy and pasted :-p