I leave my morning cup of coffee on the table to pick up a telephone call. After coming back, I find the coffee cold and undrinkable. There are strong reasons to believe that with this simple process the drama of time flow is connected. The process of cooling, or of energy dissipation, has been mathematically modelled by physicists and described as the process of “entropy increase”.

The law of nature stating that, when irreversible processes occur in isolated systems, the entropy increases was the first law of phy­sics that was sensitive to the direction of time or the “arrow of time”.

And here we meet the first conundrum. Cooling is a statistical process consisting of energy interchange between a great number of particles. If the arrow of time depends on such processes, it is meaningful only with respect to great aggregations of particles. You cannot do statistics on a single particle. Does this mean that a single particle does not experience the directional lapse of time?

The true troublemaker in the city of Chronos was Albert Einstein. In his Special Theory of Relativity, absolute time has been degraded (by the constant velocity of light) to the role of local indications of various clocks depending on their relative state of motion.