Time is not measured in segments of a certain size, ie. minuts, hours, days, years. Time is the result of change. If nothing changes there is no time! If you make an experiment where you Time with a stopwatch how many sekunds it takes for a plant to grow from seed to first leaf, you would get all sorts of different results. The reason: It is not time that is a factor it is the circumstances.
Well, yes it is - but only in its conventional formulation, and probably only here on Earth. Other advanced civilisations probably use change-measurement systems that would appear wholly... alien to us. Time is an imposition - a workable but sometimes inadequate Newtonian invention devised to measure states of change in the universe. It's easy to think of time as something external to us - as an intrinsic, controlling element of the universe itself - rather than something which we've invented in order to make sense of the change we see around us. Problem: states of change flow unceasingly, whereas conventional Newtonian time jumps in a series of discrete blocks. Time appears not to exist, and change not to take place, in the gaps between the blocks. Because of the shortcomings of the conventional system, Einstein and other leading lights of modern physics re-evaluated our understanding of time and came up with the concept of Spacetime. Someone more comfortable with the concept might come along now and tell us all more - it contains far too many formulae for my liking.
(Insert title here) Time is a necessary facet of existence. The measurement of time as we know it is a convenient terminology derived from human perspective. But one can just as easily say that without time, nothing changes. And without changing, nothing exists. Consider, for instance, atomic clocks. These monitor time according to natural processes. The NIST-F1 Cesium Fountain Clock measures time according to the natural resonance frequency of the element cesium. Now, here's the thing: if cesium—or any element, or any thing—stops resonating, it stops existing. In complete and utter stasis, the Universe would cease to exist. In this context, it seems, the passing of time is inevitable, and the only real question for humans is how to measure it. We already say there aren't enough seconds in a day, but that's our own damn faults. Measuring the period from seed to first leaf attempts to account for many factors, and thus will bring variable results. The resonance frequency of cesium, however—or any natural element—is pretty stable. If you attempt to measure relevant periods of very basic natural events, you're going to achieve a predictable, valid, and reliable result. Beyond that, ask a physicist to explain gravity and time. I'm not qualified to give that lecture.
It takes 5.730 years for 1g. of Carbon (C-14) to degrate into ½g of C-14. This is just one example on how fast one of the known elements degrate. But.... There are hundres of known elements and isotopes and they all change in different intervals.
