The inhabitants of the world of Andromeda lived on their immense globe and occupied themselves with their personal affairs as if our Earth had never existed and without suspecting that long before them, in the past, our human race had played the game of destiny, cradled in the illusion that they existed alone in the world. Nobody thought, amid the common people, that worlds succeeded each other in time as well as in space. Only the thinkers standing on the heights from which the whole of things and events can be surveyed, realised that important truth, that the doctrine of the plurality of worlds applies to eternity as well as to infinity.
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In our attempts to arrive at an idea of the constitution of the universe, two questions constantly and inevitably present themselves to our minds: the questions of Space and Time. They are correlative, but their interpretations are far from being identical, as is often supposed.
Space does not exist by itself, nor does time.
It is impossible to imagine the suppression of space. It is asserted in vain that space is the interval which separates two objects, and that if the objects are suppressed, space vanishes also. That is a pure scholastic sophism. The definition is not exact. One can safely say that it is impossible to suppress by a thought the place where objects could be. The place, the locality, that void, if you like, by whatever noun it is designated, is there quite ready to receive any object which our imagination can suppose to be there. Even though the universe did not exist, if nothing, absolutely nothing, existed, that nothing would still be space, empty space ready to receive an object. We are then forced to conclude that space exists by itself, even if it cannot be measured in any way.
It is not the same with time.
Time is created by the movements of the heavenly bodies. If the earth did not turn, nor the stars, if there were no succession of periods, time would not exist. It is astronomy which has created time.
If you suppress the universe, space continues to exist, but time ceases, vanishes, disappears.
We measure the duration of a second, of an hour, of a day, of a year, because the heavenly bodies are there as points of reference between which we can count. Besides, it is all relative. If the Earth moved twice as slowly, the days would be twice as long, but would be apparently the same. If our calendar were different, it would still be our measure of time, and we should be none the wiser.
One may put all the clocks forward or backward by one hour, and all the calendars by one day, one month, or one year, change the reckoning of the centuries, or modify the time system in any way one pleases, but it would not change the real course of nature.