In such a case one would have to fall back upon some other terminating events, which would indicate a lapse of time; such for instance as the life of a man. This, however, would be no universal measure, for on one planet the life might be a thousand years, and on another only a hundred.
Or we may look at it in another way. Suppose the earth were to turn twice as fast about itself and about the sun, the persons who lived sixty of such years would only have lived thirty of our present years, but they would have seen sixty revolutions of the earth, and, rigorously speaking, would have lived sixty years. If the earth turned ten times as fast, sixty years would be reduced to ten, but they would still be sixty of those years. We should live just as long; there would be four seasons, 365 days, &c., only everything would be more rapid: but it would be exactly the same thing for us, and the other apparently celestial motions having a similar diminution, there would be no change perceived by us.
Again, consider the minute animals that are observable under the microscope, which live but for five minutes. During that period, they have time to be born and to grow. From embryos they become adult, marry, so to speak, and have a numerous progeny, which they develop and send into the world. Afterwards they die, and all this in a few minutes. The impressions which, in spite of their minuteness, we are justified in presuming them to possess, though rapid and fleeting, may be as profound for them in proportion as ours are to us, and their measure of time would be very different from ours. All is relative. In absolute value, a life completed in a hundred years is not longer than one that is finished in five minutes.
It is the same for space. The earth has a diameter of 8,000 miles, and we are five or six feet high. Now if, by any process, the earth should diminish till it became as small as a marble, and if the different elements of the world underwent a corresponding diminution, our mountains might become as small as grains of sand, the ocean might be but a drop, and we ourselves might be smaller than the microscopic animals adverted to above. But for all that nothing would have changed for us. We should still be our five or six feet high, and the earth would remain exactly the same number of our miles.
A value then that can be decreased and diminished at pleasure without change is not a mathematical absolute value. In this sense then it may be said that neither time nor space have any real existence.
Or once again. Suppose that instead of our being on the globe, we were placed in pure space. What time should we find there? No time. We might remain ten years, twenty, a hundred, or a thousand years, but we should never arrive at the next year! In fact each planet makes its own time for its inhabitants, and where there is no planet or anything answering to it there is no time. Jupiter makes for its inhabitants a year which is equal to twelve years of ours, and a day of ten of our hours. Saturn has a year equal to thirty of ours, and days of ten hours and a quarter. In other solar systems there are two or three suns, so that it is difficult to imagine what sort of time they can have. All this infinite diversity of time takes place in eternity, the only thing that is real. The whole history of the earth and its inhabitants takes place, not in time, but in eternity. Before the existence of the earth and our solar system, there was another time, measured by other motions, and having relation to other beings. When the earth shall exist no longer, there may be in the place we now occupy, another time again, for other beings. But they are not realities. A hundred millions of centuries, and a second, have the same real length in eternity. In the middle of space, we could not tell the difference. Our finite minds are not capable of grasping the infinite, and it is well to know that our only idea of time is relative, having relation to the regular events that befall this planet in its course, and not a thing which we can in any way compare with that, which is so alarming to the ideas of some—eternity.
We have then to deal with the particular form of time that our planet makes for us, for our personal use.
It turns about the sun. An entire circuit forms a period, which we can use for a measure in our terrestrial affairs. We call it a year, or in Latin annus, signifying a circle, whence our word annual.
A second, shorter revolution, turns the earth upon itself, and brings each meridian directly facing the sun, and then round again to the opposite side. This period we call a day, from the Latin dies, which in Italian becomes giorne, whence the French jour. In Sanscrit we have the same word in dyaus.
The length of time that it takes for the earth to arrive at the same position with respect to the stars, which is called a sidereal year, amounts to 365·2563744 days. But during this time, as we have seen, the equinox is displaced among the stars. This secular retrogression brings it each year a little to the east of its former position, so that the sun arrives there about eleven minutes too soon. By taking this amount from the sidereal we obtain the tropical year, which has reference to the seasons and the calendar. Its length is 365·2422166 days, or 365 days, 5 hours, 48 minutes, 47·8 seconds.