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What is Time?

People disagree about the nature of time. People might think of time as eternal and some others might think of time as finite – as beginning with the Big Bang. The first words of the Old Testament have had some influence with its "in the beginning." There is also the issue of time being relative to the observer, and there is the issue of sequence.

A guest on Charlie Rose's TV interview program, astrophysicist Neil deGrasse Tyson, mentioned time travel and the impossibility of going back in time, the impossibility of disrupting what has already occurred, including our parents having met and having created us. It appears that time involves a law of sequence. There is an order in developments that psychic power appears unable to undo. Sequence remains crucial in getting things done. We open a door before we attempt to walk through it. In cooking dinner we mess up if we err sequentially.

So what is time? Some of us see an empty void filled with a god that always was and always will be – time as eternal. Infinity or eternity are ideas that have been around since ancient times. But empirical science cannot claim that time is finite or otherwise. Science deals with things it can measure. Infinity by definition is beyond measure, and void cannot be measured.

This takes us back to the philosopher David Hume in the late 1700s. He believed that science should be based on experience and evidence, and he held that time did not exist separately from the movement of objects. Indeed, for science time is the movement of particles, solar objects or atoms, things moving relative to other things, or movement that is rotation. In our minds, connecting things moving relative to each other we can explain sequence: one second moves past the last second, one minute past the last minute, the earth revolves around the sun – time as we understand it.

As for space, if you see two explosions that appear nearly simultaneous, one nearby and the other the explosion of a distant star, they actually happened many years apart. Two people hearing the same event will hear it at different times because they are at different distances from the event. This puts time in the time-space perspective known as relativity – which does not disrupt sequence.

As for a beginning, if the explosion called the Big Bang spoken of by astrophysicists was truly a beginning, and time is matter in motion, there would have been nothing we consider time that preceded it. To be redundant, the Big Bang would have been the beginning of time itself. But again, this is not something for science. Those who want to go beyond science will make assumptions, like the priest-scribe who wrote those first words : "In the beginning." He was working with the understanding of time that existed in his day and perhaps drawing from storytelling. He would have been baffled by what astrophysicists call time dilation.

Time dilation is more about perception. It's about time as measured by one observer, on a rocket ship perhaps, relative to another observer. The faster-moving observer measures time as passing more slowly than does a slower moving observer. Again, it's about perception, not physical fact outside the head of either of the observers. It's a time-space measurement problem that makes the question of time appear more complex than it really is: the measurement of matter in motion.

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