In Einstein’s general theory of relativity, a lot of attention is given to the concept of clocks that measure time (not to actual clocks made by people who have families, hopes, fears and dreams mind you, mainly the concept). A clock, to a physicist, is a thing that changes in a regular and predictable manner. A wall clock changes in the kind of regular way anticipated by physics, and is therefore grudgingly accepted as a special case of a clock.
Einstein’s thought experiments by which he supported the theory of relativity have clocks travelling on space ships at various fractions of the speed of light, their observers eager to observe differences and non-differences in synchronisation under various circumstances.
What is time? A clock is the means by which a physicist knows that time has passed – a hand that ticks away the seconds, the oscillation of a crystal or atoms in an atomic clock, or the simple movement of matter from here to there. Each stage of its movement or change of state demonstrates the passing of time.
Suppose that, for some reason, there was no change – no movement, no discernible difference between the way things are and the way things are again. Well, that would mean that time was not passing. You may believe that it was passing, but if nothing changed and the clock did not even begin to tick, then for all intents and purposes, there was no time. Suppose that from this state things did move to another state: as a matter of observation, the change demonstrates the passing of time.
Suppose that you have a state where matter is absent. When would that be? Well, it’s hard to say. If matter is absent, everything that can tell time is also absent. If you had a clock there, then you would know, but if there’s nothing, then there’s no time to tell. And even if there was, you wouldn’t be able to say anything about how long that time was, if it was even time.
Suppose you observed that where there had been nothing, there was now something. What would that mean? This is a change! Something happened! What do we call this change? The best name is “The beginning”. If you were writing a book about this change of state from nothingness to somethingness, you would typically start it like this:
In the beginning …
Now if your book had a slightly scientific bent, you would point out a physical clock to demarcate the changes of state and the order in which they were done. If the stuff populating your space was interesting enough to be described in some detail, you would note the ticks of your clock between your descriptions of the changes. You could use language like this between the descriptions of the states:
There was evening and there was morning, one day.
And just to rub it in, you could repeat it, like this:
There was evening and there was morning, a second day.
There was evening and there was morning, a third day.
There was evening and there was morning, a fourth day.
There was evening and there was morning, a fifth day.
There was evening and there was morning, the sixth day.
So, here’s the thing:
- Time as we experience it begins at the beginning. There is no better place for it to start.
- The proper clock by which we measure time is an evening and morning.
- The thing by which we currently measure an evening and morning is the sun.
The sun is not the thing that makes the time – it’s just there to reflect the evening and morning which began ticking slowly in the beginning. Like any good clock, the sun is just a signal by which you may properly know the time. For good measure, the sun and moon were only put there for our benefit on the fourth day. Time was fine without them:
God said, “Let there be lights in the expanse of sky to divide the day from the night; and let them be for signs, and for seasons, and for days and years …”
There you have it: you can use the sun as a clock. What? You do already? Good for you! It was placed there for this very purpose! The cool thing is that by simple arithmetic and observation, it will signal to you seasons and years as well.
How do we know that the day is the clock for the universe, and not just a clock for the earth? Well, it turns out once the clock had been a-ticking for three whole days already, God made the stars. The stars are not the overwhelming cosmos that gave birth to our world, they are there for good measure, because the universe needs a decent screen saver:
He also made the stars.
If you don’t like the universe that God made you may be tempted to invent your own. You are going to run into trouble, however, if you conflate an imaginary universe with its imaginary history of time, with the real universe with its real history of time. Even if the real universe is a mathematical subset of your fake universe, that will not make your fake universe spring into existence. It’s stupid to ignore the real world’s real time clock in favour of the clock of a fake mathematical world. The fake mathematical world with its fake time of billions of years has been around for just 82 years. The real world has been around for well under 3 million days.
If you want some of this and more, but set out in a more concise manner (and provided you don’t mind bad layout) you can read this article: God’s Clock.