erse exists in space or space exists in the universe. Does space exist outside the universe or only within the bounds of it? The similar question, does the universe exist only in time or does time only exist in the universe? Was there time before the universe, and will there be time after it ceases to exist? “Einstein’s answer to this is that time and space only exist within the universe. There is no time or space ‘outside’”(Hewitt 213). Einstein said that space and time are two separate parts of a whole called space-time (Hewitt 213). To understand this, consider our present knowledge. We know we move though time at the rate of 24 hours per day. This is only half the story, though. To get the other half we have to convert our thinking from moving though time to moving though space-time (Hewitt 213). When we move, we not only move through space, we move though time (Hewitt 213). This is the idea of space-time. If a person were to stand still, they would be moving only though time. If they moved a little, they would be moving though space a little bit, but still mostly though time. If one were to travel at the speed of light, what changes would they experience in time? The answer is simple; they would be traveling through space, with no travel though time (Hewitt 214). They would be as ageless as light, for light travels though space only (not time) and is timeless. The frame of reference of a photon, a particle of light, a trip across the universe would take no time at all (Hewitt 214). To understand how traveling though time would work, we must first understand how time and space can be stretched. Motion in space affects motion in time. Whenever we move through space, we to some degree alter our rate of motion in time. This is known as time dilation, a stretching of time that occurs ever so slightly for everyday speeds, but significantly for speeds approaching the speed of light. If we were to attempt t...
