Einstein concluded that the past, present and future exist simultaneously. He once wrote in a letter: "We physicists believe that the separation between past, present and future is just an illusion, albeit a convincing one."
This view suggests that Einstein himself was not at all sure that Time was existential.
Before attempting to interpret Time, it is helpful to think about what is actually known about time. The unequivocal answer is "NOTHING". The past, present and future exist exclusively as concepts in the human mind.
Time is not observed. This is a human concept, invented by people for people.
Special relativity probably made the characteristic of time the fourth dimension, but in reality space / time is just a convenient way of describing a region of space, along with its local gravitational field. Time cannot be observed and, in all likelihood, is just a human concept (albeit a very useful concept!). Physics defines time as "that which is measured by the clock", that's all.
Measuring time is simply an arbitrary quantification of a given set of events. There is a common misconception that time is something that actually exists as a fourth dimension independent of matter, energy and space and their various interactions (events). Time cannot be respected, and there is no evidence that it actually exists outside of the human mind. When we measure time, we are actually counting events like the ticking of a clock. Events are real enough, but the time interval we are measuring is best thought of as the imaginary interval between events.
The origin of the concept of time
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It is likely that people came up with the concept of time as a convenient way to divide tasks for several people in one place. For example, an agreement to meet two people to hunt at sunrise on the riverbank next to a large rock represents a synchronization of a two-person sunrise event and a unique geographic location on the planet. The human concept of time serves to precisely synchronize events for a species that owes much of its success to organized cooperative behavior.
Although today we will associate sunrise with a certain time indicated on a wrist watch (more precisely, an atomic clock), in any coordinate system there is no "known" absolute standard of time. those. there is no "known" universal standard time at any point in the universe with or without relativistic effects of speed and gravity. It is noteworthy that the sunrise on the river bank will never exactly coincide in time (even by measuring it with an atomic clock) with the same sunrise observed from the cliff. This is partly due to the constant changes in the Earth's orbit and, in particular, the uncertainty of the location and speed of quantum particles. Quantum observations show that it is impossible to predict or measure the exact local time of any event in the universe.
What do you think about time?
