Your Brain is a Time Machine: The Neuroscience and Physics of Time

by Dean Buonomano

Others believe that time is merely an abstraction, a very useful concept to help explain how the universe works, but unlike mass or energy, time would not be a fundamental ingredient of physics. To understand this view a bit better, recall that, in practice, clock time is always measured by change. No matter how accurate or inaccurate, clocks are always quantifying change of some physical phenomenon. The consequence of this fact is that it is always possible to express time as some other nontemporal physical measure. For example, quartz clocks and watches often mark the time with dials that revolve around a circular face, and when the minute hand goes from 12 to 6 we say 30 minutes have passed; but couldn’t we just as well say 180 degrees have passed? Or in the case of a pendulum clock with a base frequency of 1 Hz, instead of saying 30 minutes have passed, we could say 1,800 swings have elapsed. Indeed, the standard unit of time (the second) is not actually defined as some pure unit of time, but instead as 9,192,631,770 cycles of the radiation corresponding to the resonant frequency of cesium 133, which is approximately equivalent to how long it takes the earth to spin 1/240 of a degree around its axis.