What is a second? That’s an easy one; a second is defined as 9 192 631 770 oscillations of a caesium 133 atom.
That’s all settled, then; or is it?
Does a second have any independent existence, or is it just something that has emerged from arbitrary divisions of years and days?
Compare, for example, a second and a proton. It seems quite reasonable to assume that a proton has an existence that is independent of our measurements. It is probably safe to assume that the diameter of a proton would be about 1.7536 femtometres, whether or not we ever measured, or even thought about it.
Can we say the same for a second? Would a second exist as anything in its own right if it had never been defined? If not, does that tell us anything about the “reality” of time? One thing we know about the second is that it is the SI base unit for the measurement of time. So, for example, if the base unit of time has no independent existence, can time be said to have independent existence?
