Time makes our lives. It is the key to how we perceive everything, from the ticking of our own minds to the events which mark our passage from birth to death.The true nature of time continues to elude us. Physicists have made huge strides in the last century or so in the way we think about time, but as to what it is exactly we are not really any wiser than the Ancient Greeks. Plato, after all, thought time was an illusion. We talk of time ‘flowing’, but flowing through what? At what speed does it flow and why? And what is the ‘substance’ that flows? Time throws up all sorts of paradoxes. You can use the existence of time, for a start, to prove that nothing is real. The past is as dead as those who no longer live, no more real than your dreams, right? And the future has not happened yet. So all that is to come is, again, imagination. All that is real, therefore, is that infinitesimal sliver of time between past and present, which of course amounts to nothing, because as time never stops that sliver has zero thickness. So, time is real, but nothing else is.
What science has always been happy to do with time is to ignore the philosophical horrors it throws up and just get on with measuring it, giving it a symbol and plugging it into our equations, represented by a nice little letter, like t, doing its job, oiling the clockwork of the spheres. Time is a fundamental quantity, meaning that it cannot be defined by reference to
any other quantity. We can only measure it and use time to derive less fundamental quantities. A change in velocity over time gives us acceleration. Einstein showed us that the pull of gravity and the tug of acceleration were equivalent. Indeed, Einstein went on to show that ‘space’ and ‘time’ are really different sides of the same coin. Before Einstein, it was thought that space was filled
with an invisible medium called the ether, waves in which carried light and other electromagnetic radiation just as air carries sound. But in Einstein’s relativity, the old ether was abolished and
replaced by space–time, a sort of conceptual super-ether, through which motion and the attracting force of gravity can be plotted.
Unlike quantum effects, time is something we perceive directly. We have memories of the past but not of the future. Neither the future nor the past are ‘real’ in the sense that they are accessible and measurable, but one seems to have a privileged position over the other: the fact the past has ‘happened’ gives it a reality denied the future. Time as a fundamental quantity seems to be intrinsically linked to our conscious perception of the world.
The idea that time is just the fourth dimension of space, one which we have a special interaction with through the offices of our conscious minds, is an attractive one. And clearly there is an element of truth in it. In our everyday experience, time flows, as we flow with it. In classical physics time is frozen as part of a frozen space–time picture. And yet there is as yet no agreed upon
interpretation of time in quantum mechanics. What if a future scientific understanding of time were to show all previous pictures to be wrong and demonstrate that the past, the future and even the present do not exist?
The distinction between past, present, and future is only a stubbornly persistent illusion….