1 - Origins of thinking about time

Summary

Ever since I started reading popular science books on physics, I have regarded it as self–evident that time is synonymous with empty duration, that it flows like a river and carries in this flow all events without exception. This stream is unalterable and unstoppable, going in a never–changing direction: from the past to the future.

It seemed that this interpretation, given our knowledge about the surrounding world, was unavoidable.

I learnt only many years later that people had not always held such or similar intuitive notions - far from it.

Heraclitus of Ephesus, a philosopher in ancient Greece who lived at the end of the 6th century bc, appears to have been one of the first thinkers of antiquity who set forth a belief that everything in the world changes and that this changeability is the highest law of nature (all things are in process and nothing stays still). Heraclitus set out his view in the book About Nature, of which only a few fragments survived and reached us (Cosmic Fragments).

Heraclitus taught that the world is full of contradictions and variability. All things undergo changes. Time flows relentlessly, and everything that exists moves with this unstoppable stream. The skies move, physical bodies move, a human's feelings and consciencemove as well. ‘You cannot enter twice into one and the same river’ said he, ‘because its water is constantly renewed.’ Things come to replace other things.