Scientificlly: What is time?

Question

What are the theories of time and why it passes?

Answer 1

Actually there is no such thing as time when you describe it scientifically. Time is just a ratio. You take a moving object, or a repeating event as a reference and divide its motion or its event period into equal pieces and you assign a value to the completion of each piece.

For example assume that the rotation of earth is at a constant speed. You say that one full rotation is 24 hours and divide it into pieces to get the minutes and seconds. Now atomic clocks are used where each radiactive event describes a second.

Relativity is a different matter, it states that you time observations are related to your observations of 3-D space. Which is quite intuitive because both are based on motions right.

You can read this in Feynman Lectures in Physics volume 1.

Answer 2

Relativity shows us that space and time must be treated together as a space-time continuum. Time is a dimension just like our 3 space dimensions. (But time is treated differently mathematically)

Quantum gravity theory might show that both space and time are really just approximations of some more basic entity. But no one knows what those entities are.

To answer your question, no no really knows what time is or why it seems to flow.