With the invention of writing, a great change came over primitive man. First with pictures, later with simple writing, he could leave for his children a record that was not entirely dependent upon memory. As we shall show, many of these earliest records were astronomical. The Babylonian “boundary stones” were decorated with pictures representing the constellations; and many Egyptian temples were oriented to the Sun. Most religions have some astronomy hidden in their roots; for early peoples looked to the Sun for their greatest benefits; and to the stars for the Sun’s path.
The religions were suited to the regions of their origin. But all worship is based on tradition, and a migrating tribe was apt to take its religion in the old form, when it started off for farther, greener fields. The tribes whom it encountered en route would worship the same gods in a different manner; and, as from any conflict of thought, developments finally spring–so from the wars of these migrating tribes, religion, philosophy and science received fresh impetus.
Some system of measurement was the first necessity for even simple calculations of time. We may say today that time is that which is measured by a watch or a calendar; but in that definition we already imply a knowledge of duration and the difference between minutes and hours, days and weeks, months and years. A watch is the short-scale measure of a calendar.
Together they give us all that is necessary for our ordinary purposes; but neither alone is sufficient. An engineer of today is accustomed to gauge the flow of air through a tunnel by an anemometer which measures the velocity of wind. If the air is unduly sluggish he must find some other device such as a flare set at a point in the tunnel, and a man with a stop watch a hundred feet away. The watch is started when he sees the light and stopped when he smells the smoke. For most tunnels the scheme works perfectly, but one engineer who advised such an experiment received a note from his desperate foreman: “Enclosed find stop watch. It was useless for the purpose. Kindly send me a calendar.”
These two systems of measurement, the calendar and the watch, have developed together. There are five great timekeepers in the heavens, but today we employ only two–the rotation of the Earth on its axis and the revolution of the Earth around the Sun. The watch is tied to the first; the calendar to the second. There is a third, equally well known, which was once employed as much as either of the others. The Moon however is a lady of uncertain reputation, and of recent years she has fallen into bad days. Her name lingers in our “months”; and they bear also a vague remembrance of her, in their length; but the direct connection has been severed.
As a matter of fact the Moon complicated everything. Once in between twenty-nine and thirty days, our satellite revolves around the Earth, and this revolution causes its phases. The period is not commensurable with any period of the Earth’s movements around the Sun; and the astronomers of Ur and Heliopolis had really enough to bother them without the Moon’s vagaries. Yet they made a valiant effort to understand and adjust their calendars for the pleasure of all their gods. Like the man in the fable they ended at last by suiting no one. If they adjusted their calendars to the Moon (as Mohammed did in later times) then the seasons were unpredictable. Winter might very easily arrive when the calendar showed summer; and the leaves fall during a Maypole dance.
If the astronomers reversed the process and calculated by the Sun, then their calendars kept time with the seasons, but the months failed to show when the Moon was full; and the men who lived near the mouth of the Tigris and Euphrates knew that if the night goddess were provoked, the tides of the sea would rise. In the end the harassed calculators cast the Moon out. The calendar became purely solar, and today you must ask an astronomer or a lover if you would know when the Moon will be full. We know our months as artificial divisions of unequal length, to which we look forward with joy or sorrow–as they mark our pay day or our bills. Only their inequalities, due to the vanity of Roman emperors, are in the least reminiscent of the Moon who gave them her name.
Under the guardianship of the Sun, we have at last arrived at a stage where our watches and clocks are almost perfect and our calendar reasonably accurate. Yet the finest of our mechanisms are only secondary timekeepers. Each earthly timepiece must be adjusted to the movements of the heavenly bodies. Curiously, very few people seem to be aware of this necessity. They seem to think that it was all very well for the primitives to observe the heavens but only fools and astronomers would spend valuable time on such pursuits today.
We had been making some observations ourselves, one sunny afternoon. We had worked out the calculations, made all the necessary corrections, and were fairly certain that our newly set watches erred by not more than five seconds, when a visitor was announced. At the moment when she came in, we were perched rather precariously on chairs, while we set the hands of our clocks. “That sounds like fun,” she said, when we tried to explain our actions; “but surely you don’t set your clocks to the Sun do you? Haven’t astronomers discovered that the Sun was all wrong?” Just at that moment we found some difficulty in keeping our balance, but when we were on firm ground we explained.
The Sun is irregular in its apparent movements; but its irregularities are known. They repeat themselves constantly, and any astronomer can make the proper correction to cover them. Ultimately, hours are not dependent upon the clock in the Naval Observatory in Washington, any more than the year is dependent upon the calendar. Our devices for telling time have improved enormously since the days of the first hunters; but the nature of time has not changed. It was, and it is, determined by observation of the heavens.