Time is something that can be measured with relative ease. Humanity has been measuring time for thousands of years. But scientists and philosophers have been struggling with the definition of time since, well, time immemorial. The best definition of time should be one that does not include references to time within the definition. So words such as rate, before, after, since, passing, sequence, speed, etc. should not be used. So let me give it a go.
Time is that character of a frame of reference caused by the changes that occur within that frame of reference down to the quantum and/or subatomic level.
These changes can manifest themselves macroscopically as any physical change in an object, such as its position, or at the subatomic level, such as changes in spin or energy level of an electron. Qualities such as rate (amount of change per unit of time) would be governed by the number of Planck time units that were involved in a certain change. Planck time is the theoretical smallest unit of time possible.
Think about how we measure time. It always involves a change that occurs in a repeating pattern: the swing of a pendulum, the vibration of a spring or the frequency of radiation emitted from an atom. Cyclical changes are what we use to keep track of the flow of time. But it doesn't have to be cyclical changes to cause a sensation of time. A banana gets ripe, then rots as time passes. A vehicle passes by, thus changing its position. If there were no changes occurring at all, then time would be irrelevant and, basically, non-existent. Even thought processes are the result of changes in electrical patterns in the brain. Ions flow from place to place, resulting in sensations of time passing.
Time absolutely requires changes to take place, and if none did, even at the quantum level, there would be no time. So the definition of time must, therefore, include the fact that it depends on things changing.
But does the term "change" require time within its own definition? If it does, then I can't use it in my definition of time. If we define change as the processes whereby an object ceases to be in a particular state or position because another state or position is manifest, then we can avoid the use of any reference to time in that definition, and it is a definition that is adequate for our purposes here.
Therefore, I think my definition of time is fairly all-encompassing and accurate. However, I will admit that it potentially results in a chicken-and-egg scenario. Are changes what cause time to flow or is the flow of time the cause of changes? I welcome feedback.
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