I am impressed by the following words contained in the opening pages of the classic The Time Machine by H.G. Wells.
“Nor, having only length, breadth, and thickness, can a cube have a real existence.”
“There I object,” said Filby. “Of course a solid body may exist. All real things- “
“So most people think. But wait a moment. Can an instantaneous cube exist?”
“Don’t follow you,” said Filby.
“Can a cube that does not last for any time at all, have a real existence?”
Filby became pensive. “Clearly,” the Time Traveller proceeded, “any real body must have extension in four dimensions: it must have a Length, Breadth, Thickness, and – Duration. But through a natural infirmity of the flesh, which I will explain to you in a moment, we incline to overlook this fact. There are really four dimensions, three which we call the three planes of Space, and a fourth, Time. There is, however, a tendency to draw an unreal distinction between the former three dimensions and the latter, because it happens that our consciousness moves intermittently in one direction along the latter from the beginning to the end of our lives.”
“There is no difference between Time and any of the three dimensions of Space except that our consciousness moves along it.”
“For instance, here is a portrait of a man at eight years old, another at fifteen, another at seventeen, another at twenty-three, and so on. All these are evidently sections, as it were, Three-Dimensional representations of his Four-Dimension being, which is a fixed and unalterable thing.
In these few words Wells succinctly explains the concept of time. What charm there is in a simple explanation of a complex matter.