Mysteries of Modern Physics: Time

Studying the physics of time; the meaning of a clock; understanding a phrase; the arrow of time; the concept of entropy; how it holds the key to the one-way direction of time in the universe.

Approaching time from a philosophical perspective; presentism holds that the past and future are not real; only the present moment is real; the laws of physics appear to support eternalism that says all moments in the universe are equally real.

How to measure the passage of time; the practical concerns have driven the search for more and more accurate clocks; the problem of longitude is solved with a timepiece of unprecedented accuracy; GPS navigation units rely on accurate clocks.

Understanding time; the arrow of time; how memory and ageing are related to time; looking at irreversible processes, such as an egg breaking or ice melting; the essence of the one-way direction of time.

The history of the second law of thermodynamics; it is considered by many physicists to be the one law of physics most likely to survive unaltered for the next thousand years; entropy is the degree of disorder in a closed system.

Isaac Newton's laws of physics are fully reversible; particles can move forward or backward in time without any inconsistency; the arrow of time is fundamentally connected to irreversible processes and the increase in entropy.