To adress the question of time we must approach it from a perspective external to our physical reality. Our physical reality exists within defined limits of perception that are contained within the five senses that allow us to perceive time as a function. With those senses we determine that time is linear and that time passes at a rate determined by those senses. Without our perception of time, the limited capabilities of our physical brains would be unable to determine what has happened in the past, present or future. Many of us have experienced times in our lives when the day seems to fly by so fast that we wonder where the time went and yet some days seemingly take forever. This perception of the speed at which time passes is directly related to the senses that percieve it. These senses and their ability to perceive time passing are also related to the physical structure which embody them.
Lets look at our sight for a moment which determines how fast an object is moving. If we stand on earth and view a plane passing over head we determine that the plane is moving at a certain rate of speed. We then asses from the speed of it’s movement the amount of time it would take for the plane to get from point x to point y. Lets say we determine that it will take the plane one hour to get from point x to point y under normal conditions. Now lets change those conditions and watch what happens to the definition of the time it takes. Assuming the earth were moving in the same direction as the plane, lets change the condition of how fast the earth is moving to equal that of the plane. Our definition of the amount of time it will take for the plane to reach it’s destination has now increased to infinity. The plane will never reach point y because the earth is moving at the same speed as the plane in the same direction.
Now lets look at time in the same context for our senses. Though the understanding of the planes relative time in context to the earths movement is easy to grasp it does not adress the issue of how long that plane was in the air. Obviously weather the plane is moving or not in a relative sense to the earths movement, it was still in the air for the same amount of time. However just like the plane being relative to the earths movement so also our senses that percieve how long the plane was in the air are relavent to how fast the molecular structure of our senses are moving in context to the world around it. The faster our molecular structure is moving the slower time will appear to be moving in relation to our senses. It’s the same concept on a much smaller scale. This is how one person can feel that the day took forever while another person percieved the day to fly by.
From this understanding we can determine that time is relative to a given space and the matter that is moving within that space. This leads to the conclusion that as we approach the speed of light, time stands still. It is no longer possible to percieve time when we are traveling the speed of light, at least not in the physical world in which we now exist. This is where extra dimensionsal theory begins to take place.
So in conclusion time is a relative function of how fast matter moves within a defined space relative to the speed of matter moving external to that space.