The Arrow Of Time

Why does time only move forward? Time is only known by the relation of one rate of change to another rate of change. It makes sense to say that one clock runs faster than another, but if time itself were to run faster, then all clocks (and ALL physical processes) would run faster together and there would be no way to know that anything was unusual. Time is relative. To say it moves faster or slower is meaningless unless it can run differently in different places. In the same way, saying it moves forward or backward is meaningless unless it can run differently in different places. If time ever did run backwards, we would also run backwards and thus never notice.

We only experience the present. We know the past through our memories, but memories are stored in the arrangement of our synapses in the present. For all we know there might be no past and our memories false. For all we know, time is already moving backwards, we have forgotten the future, and we remember a past that we will soon experience – but by the time we get there we will have forgotten our current present, not being able to remember the future. At every moment, we will have the compelling belief that we are experiencing time forwards. Since there is no way to tell the difference even in principle, it is actually meaningless to think of time “moving” at all. The real question is why we don’t remember both past and future. The real question is why we don’t see some objects evolving backwards relative to other objects. Why don’t we see spilled milk spontaneously leap off the floor back into the glass?

If milk were to spontaneously leap off the floor we still might not interpret this as backwards time if there were no glass there to catch it – and it would have to be the same glass it fell out of in the first place. Otherwise, the milk is just hopping around and changing glasses. This would require someone to be standing there with it, requiring them to be moving backwards, requiring their surroundings to be moving backwards, and so on. If you continue moving forward in time, you will find yourself deeper and deeper in the milk’s past. This gives you the opportunity to interfere and create a paradox. Killing the cow before it has grown old enough to be milked will mean the milk will never exist and you will have indirectly interfered in your own past. There will be chaos.

With different objects experiencing time differently, it will be impossible for any object to experience time in one direction for long. They will interfere with each other. Time can only be experienced by an object when the object’s surroundings experience time in the same direction, whose surroundings must also be moving in the same direction, and so on. In any given set of particles, time either moves forward together or else not at all.

When energy is evenly distributed throughout a system, particles simply bounce around off each other in a way giving no hint which way time is moving. There is no way to measure time in this situation and so it is meaningless to say it exists. Time only exists when there is an unequal distribution of energy. The real question is not why time doesn’t move backwards or why it doesn’t run in different directions, but why we find ourselves in a universe with an unequal distribution of energy for measurable time to exist at all. Of course, one could always say that if there were no time, we wouldn’t be here to be asking the question, but that still doesn’t explain why.

So why do we find ourselves in a universe with an unequal distribution of energy?