"Time" as we normally conceive it (i.e., in terms of hours, etc) is an artifact of our contingent existence on this planet, in the current state of the local planetary system. Had we existed on a different planet, our use of time would not be the same, assuming that the planet had a different orbital velocity around its sun. In fact, the artifact that we call "time" could have been derived from a different source other than the relative position of the Sun. "Time" as we normally consider it (as a marching of days, or hours, or seconds, or nanoseconds) is a anthropomorphic hypostitization; it is an arbitrary abstraction of a contingent being.
What would "time" be to a race of beings who didn't use visual cues to explore their environment? Suppose we, as a species, didn't have eyes and couldn't sense our environment at a distance. Suppose we used hearing and touch and the other senses. Could we have the same concept of "time" that we currently do? No, because "time" in its practical sense is a visual measure of the passing of the seasons.
There is no such *thing* as "time", because "time" is an epiphenomenon of our evolved senses and the local state of the planetary system. Our "time" may not be the same "time" as a different species, on a different planet. In fact, our "time" could have been different. We could mesure time in terms of some other phenomenon. For instance, a unit of "time" could be delimited in relation to the "how long it takes" for 1,000 grains of sand to pass through a funnel. And, of course, this "how long it takes" is directly dependent on the diameter of the funnel and the diameter of the grains (assuming they are all even identical). Analogus to this "how long it takes" and its relation to the size of the elements is our subjective concepts of "time", our personal experiences of "time". "Time" goes quickly when we are busy or having fun, but "time" goes slowly when we are bored, etc.
Is there a real Time? Something other than our perception of "time"? Something independent of any species' perception of it? Well, the most ingenous answer is: "I have no idea". For to state and explain that there is an existence or substance or independently real phenomenon that would be Time and to describe what this Time is, would be to turn it again and inevitably into a human metaphor. If there is Time, Time would exist with or without us, unlike our "time", which is merely a figment. If the human species were to die out, our concept of "time" would die out too. But Time, be there such a phenomenon or no, would continue to Be. But what this Time is, is not something that pertains to our explanations of it. Time, therefore, can only be a negative concept: It is not this; It is not that.
Perhaps the only thing we can accurately say of Time is that it is in some manner related to movement or motion. However, I tend to consider this to be another artifact of our contingent existence here. Our use of "time" is directly derived from the movement of the Sun and the Moon. Had we not eyes to see, we would never have developed our concept of "time". Perhaps we would have developed a different "time".
Imagine yourself existing in a vacuum, with no light, no sound, no smell, etc. You cannot see. You cannot taste. You cannot touch. You just have thought. Suppose you were detained in such a device. Could you determine how "long" you were in there? What counter of "time" would you use? What would "time" even be to you? Would you have a sense of Time, or the fluid passing of duration? Or would this sense of passing duration merely be the body's consciousness of its own metabolism of matter? "Time" here would probably be the pulse of your nervous system and the chemical reactions, which would be different for different people. So, again, even this passing of duration would merely be a epiphenomenon of your peculiar chemical makeup and metobolic constitution.
So, is Time perhaps some aspect of the universe that underlies all epiphenomenal "times" and is a necessary, non-arbitrary condition of them? Well, if it is, I would dearly like to know how anyone can establish this independently of our arbitrary, non-necessary and contigently evolved senses and cognitive abilities.
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Thanks for starting this topic. I enjoyed being nihilistic.