What is Time?

It seems that 'time' is a human construct. We have clocks that supposedly measure time, but what are they really 'measuring'? They are basically just moving hands! Instead, they seem to be 'measuring' our position with relation to the sun.

Lets try to come up with some simple and intuitive description.

Maybe we can consider the possibility that there is no such thing as time. In this model, if we consider how some masses are currently distributed, it would difficult to describe how masses 'use to be' distributed. We could display snapshots of masses that moved around a room, and arranged these snapshots in the order that we took them. But, lets say we took the first snapshot after 10 seconds, and the second snapshot after 10 hours, and the third snapshot after 10 years. The pictures would tell us nothing of the spacing between snapshots (the time interval), which presents a big problem.

Lets say we know that a given mass is going to move parabolically. We can picture a mass in our imagination / mind's eye moving slowly over this path. In the real world, though, there seems to be 'something more' than just the movement, namely the instantaneous movement. The mass may speed up the slow down then speed up again. If we forget time, we don't get any of this slow-fast-slow movement, we just get a projected path. This almost suggests that time is necessary so that the human mind can gather more information about the qualitative nature of the system.

In other words, it is useful to have a way to qualitatively describe and causally distinguish these 'snapshots'. So it seems that we have invented 'time' to be able to measure an interval. But, is it niecessary? Is time necessary? In general, it is a qualitative aspect that gives more information to a system; think about 'length' or 'width' i.e. distance, are these necessary? As necessary as time, it seems. So, we must include time, and look for a different model, one where time does exist.

One question though. If time simply describes a snapshot, and we go back in time, do we simply go back to this snapshot?