There are many perspectives from which we can discuss the nature of time. Here are a few:
1. Time is integral to the structure of the universe. It’s one of 4 dimensions, where events occur in sequential order. It can be shown on a time line. Time travel may be possible.
2. Time is NOT a container or fluid through which events and objects move, nor does it flow. Time is an intellectual idea. We use it, together with space and numbers, to sequence, organize and compare events. Time is neither an event nor a thing, is not measurable and cannot be traveled.
3. Time is a cyclical, repetitive thing, endlessly repeating in a great cycle. A snake chasing its own tail. There is no linear movement in time, no progress, no upwards or onwards.
These three conceptions are religious and philosophical, as well as scientific. We can each chose a favorite. In fact we each have to choose, because time is social.
If you are on your own (no boss, no spouse, no kids) or on vacation, you don't need a watch. Time is more or less irrelevant. You do what you wish, when you please.
But add another person, and suddenly time is necessary. It allows us to compare the duration and sequence of events. Time makes it possible to say to each other,
This takes longer than that and Which one happened first? and I want my dinner now!
A unit of time is usually defined as a number of cycles of a regularly moving physical body (a pendulum, planet, moon or star). We watch this moving item - either together or separately - and synchronize ourselves in time.
I'll see you the day after the next full moon, ok?
Watching heavenly bodies is fairly easy. They usually appear in the sky over the earth for a few hours each night. But not always. Weather can hide them, and they aren't visible from some locations. And they are not really all that regular in their movements.
So we learned to make swinging pendulums and water clocks - then clocks and watches of all sorts. They let us share time at night, in bad weather, on the seas and in the air.
So time is a social way to compare the length and sequence of events. What else?
I don't know about you, but time travel has always seemed like an appealing thing to me. As long as there is a reverse gear so I can get home!
I'll write more on this at another time - I'm late ...
I used to own this very Rolex. Click it to see what time it is.