Moon complicated everything

Moon complicated everything

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.”
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The first great division of time is marked by day and night

The first great division of time is marked by day and night

The first great division of time is marked by day and night. The Earth rotates on its axis like an orange strung on a wire before a steady light and the glow falls first on one side then on the other. Were we situated on a distant star, we should see in this motion the most perfect regularity known to nature. The period is so even that astronomers are doubtful whether there has been any change in its pace since the beginning of historical time. From our prejudiced viewpoint on the surface of the rotating planet, this perfect regularity seems upset by another, quite different motion–the motion which causes the seasons–the revolution of the Earth around the Sun. There is nothing even about this second movement, and its unevenness seems, to our prejudiced eyes, to upset the regularity of day and night.

Consequently the standard observatories make their readings from the time when one star crosses the meridian to the time when the same star recrosses, rather than by the crossings of the Sun. By this means they manage to pretend that they are watching our planet from the distant star itself, and their viewpoint becomes impartial. Yet the reckonings, whether made by an amateur taking time by the Sun or a professional gauging it by a distant star, are both made to agree with the Earth’s motion on its own axis; and by that the twenty-four hours are set.

Equally important for us is the revolution of the Earth around the Sun, and on this revolution our calendars are based. All our “anniversaries” (from their very name), our festivals, the seasons which mark the planting and reaping of crops, and, in specific cases, the overflowing of rivers, are dependent upon this revolution. The period of the year is very nearly constant, but the half-year periods are variable. In our time the Sun prefers its northern residence, and lingers there three and a half days overtime, so that summer in the northern hemisphere is longer than summer in the antipodes.

These three celestial clocks, the rotation of the Earth on its axis, the revolution of the Earth around the Sun, and the revolution of the Moon around the Earth, have formed the bases of time in our practical, everyday lives.
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The evening and the morning were the second day

The evening and the morning

Alas for permanency! The ancient Egyptians forgot in their calculations that the rising and setting points of heavenly bodies are likewise dependent upon the Earth. The stars do not rise now, where they rose in ancient times. The poles of the Earth are not remaining in one place while the Earth spins around. They too have a motion and every little movement has a meaning all its own. They are wobbling as the points of a top wobble when the top is slowing down.

It is hard to buy an old-fashioned top today; but allow us to recommend one to you, if you wish to understand Precession. Wind the top up with a cord, give it a good swift start on a flat surface; then watch it carefully. Do you notice that the tip end has a little motion of its own? Even while the spin is still so fast that the rotation is indistinguishable, the end where you wound the cord is describing a much slower circle, apparently all on its own?

In much the same way our Earth behaves. The spin, like the spin of the top, makes its day and night; but the wobble of the poles, makes precession, and this little circular movement is so slow that 25,800 years are required before the precessional hand on our grandfather’s clock will have returned once to its starting point.
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“The time has come”

"The time has come"

Saint Augustine was, of course, quite correct. The celestial bodies measure time for us; they do not tell us its nature. Like all too common words, “time” has developed a multitude of meanings. We use it in one sense if we say, “The time has come,” and with a slightly different meaning if we speak of “time and tide,”–to give only two examples out of thousands; therefore philosophers have sought to define the nature of time, and differentiate its meanings. From Aristotle and Saint Augustine to the superb treatment offered by Thomas Mann in the Magic Mountain philosophers have tried to solve their own problem; and from Thales to Herschel the astronomers have been content to measure this aspect of the universe and scorn its nature.

Not until our generation have the two problems touched each other; but recent scientific theories indicate a close bond between the two. When Einstein announced to the world his fourth dimension, the philosophers looked up with startled eyes. Einstein was a physicist and a mathematician. They had not expected to find in him so close an ally. “But that is what we have been trying to say for two thousand years,” the philosophers announced, rather modestly to be sure, for philosophers like astronomers have fallen on evil days. “We have not stated it as well, and we could not point to mathematical proof behind us; but surely we have told something of the sort. Don’t you remember that in the Republic, Plato said that the studies of three dimensions would not, by themselves, completely explain the world. Surely you remember that?” No one answered; no one remembered. “This fourth dimension,” said the world, “is a new idea, and because it is new we must investigate it.”
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Now we have Babylon, and a long time further on we reach the cavemen

Now, we have Babylon...

Now, since we are flying faster than the speed of light, historical events are enacted before our eyes. True, we see the result before we see the cause; but our point of view becomes only the more philosophic by that reversal. All the historic disputes are settled. So it was Homer (not another man named Homer) who wrote the epics!

Now we have Babylon, and a long time further on we reach the cavemen. “Would you like to see a dinosaur?” our pilot asks. Personally, we should like that very much, but the others of our party are becoming nervous. They cannot quite believe that the world they left is still there, quite intact, and very conscious of the twentieth century. They would rather turn back. So the pilot decelerates his plane, and the later light rays, which we have passed, begin to catch up with us again. History comes up in its proper order. We see surveyors taking observations on the Sun and laying out the pyramids. We could not ask greater accuracy of a modern surveyor laying out grounds with the help of all his instruments. This history at last has the perfection toward which all history should strive; we feel as though we were living in those times.

As we slow down, we see the Barbarian hosts ransacking the proud city of Rome, while cramped in a cell Dionysius Exiguus studies imperfect old records to determine when Christ was born. From his work all our own chronology dates, but we never saw him before. Another deceleration and we are in the midst of astrologers who inform us that this is not a propitious day to start business. They are a great convenience. While they are around, the professional man, caught by a persistent and non-paying cilent, on a beautiful afternoon, need not make the customary apology: “I’m sorry that I can’t attend to your business, but it just happens that I have a very important conference with Messrs. Bunker, Ball and Green to decide an important question on the outskirts of town.” He need only point to his astrolabe and state firmly: “Sorry the planets are unpropitious today. In ten days they will have changed, possibly for the better. You might come back and see me at that time.” The client could have no possible answer to make, and the businessman can proceed to his game of golf with a clear conscience.
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“Twentyfour hours” is a clumsy mode of expression

24 hours system

Wake! for the Sun who scatter’d into flight
The Stars before him from the Field of Night,
Drives Night along with them from Heav’n, and strikes
The Sultán’s Turret with a Shaft of Light.

OMAR KHAYYAM, The Rubaiyat

The change from night to day and day to night is so obvious that names to distinguish one from the other must have been among the earliest words in the vocabulary. Yet there is no term, even in English (which we like to think fairly well advanced) that will designate the whole period of twenty-four hours, except as we speak loosely of a “calendar day” for convenience’ sake. “Twentyfour hours” is a clumsy mode of expression, and the compound words which astronomers have developed to suit their scientific needs are (as usual) still worse. This anomaly is far from proving that the men who invented our language were uninterested in time; rather the reverse.

We know from existing primitive societies, that men give explicit names to the things which interest them most; and as their interest becomes more acute they develop a terminology to suit the complications of their knowledge. General and abstract words are left to the realm of uninteresting subjects. The Eskimos today have only one word for “trees” because verdure lies outside their immediate province; but they have a dozen names to differentiate the varieties of snow all about them, and not one of these terms means just plain snow as more southerly peoples speak of it. In the same way a dog-fancier divides his favorite animals into collies, chows, Pekinese or Samoyedes, but never under any circumstances will he call a dog, a dog. If the animal passes his understanding, he can only refer to it as a cur.
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Three simple divisions of the day: Sunrise, noon and sunset

Sunrise, noon and sunset

We can only guess how the Egyptians worked out the observations. They may have used equal altitudes of the Sun, marked their directions and bisected the angle. Possibly they employed the equal altitudes of stars, or bisected the extreme angles of the pole star. Since any definite knowledge of them begins with pyramid inscriptions and since they had worked out a method of determining the meridian before the pyramids were built, we have no knowledge of their ingenuity.

Sunrise, noon and sunset: these three simple divisions of the day were used by the earliest peoples, and continued in use far into classical times. Homer sang of no others: and the Romans never reckoned by hours until five centuries after the “Foundation of the City.” But the peoples along the eastern Mediterranean belonged to an older civilization. They had found need to divide the day, even before they could reckon the meridian line. In Babylonia, at least, some such system as hours probably preceded any knowledge of “high” noon.

It is often said that the oldest sundial of all was a pyramid. That may be true; but we are not entitled to the deduction that the pyramids were built for astronomical purposes. Primarily they were intended to house the body of the king while his spirit was crossing the lake of waterlilies, tricking hostile gods, and generally encountering wild adventures in his afterlife.

Among his peoples, his spirit alone was entitled to this immortality. The pyramid was certainly a symbol of the king rising to meet the Sun God; but its time-telling features may have been purely incidental. We should really be rather surprised if these gigantic stone structures, built to face the cardinal points, endowed with all the knowledge and resource of the age, did not tell time in some way or other.
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“There are 360 days,”— a slightly inaccurate calculation

Ancient calendars

Since we wish the divisions of our day to be equal, the hour lines on the board must be of unequal length. The Sun gains far more altitude between 8:00 A.M. and 9:00 A.M. than between the hours of 11:00 and noon. In fact for a short while at midday the change in the Sun’s altitude is so slight that it becomes useless as a gauge of time.
Similarly in the afternoon there is only a slight drop until 1:00 P.M. and then the length of shadow increases more and more rapidly until sunset.

However refined such a dial of the Thutmose-type may be, it is always dependent upon the altitude of the Sun, and therefore it suffers from a number of disadvantages. For each observation it must be turned until the shadow of the gnomon falls at right angles to the graduated rule, and it must be set horizontal. At a time considerably after Thutmose, the Egyptians added a plumb bob to their sundials, to keep the ruler level.

Denver is approximately forty degrees north of the equator, and here the days vary considerably in their length. The midsummer days are fifteen hours long; the midwinter days nine. Karnak was near the tropics; and Thutmose hardly needed lines to mark the difference between months on his dial. A few seasonal guide lines would suffice to show the change. Yet even in Karnak there was a difference between summer and winter, easily seen in the variable length of days. The mechanism of their time measurement depended upon the Sun itself, not upon whirling dials and springs and wires. We adjust ourselves to the routine of mechanical necessity. They adjusted themselves to the variations of nature.
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Egyptians expended a great deal of ingenuity and scientific care in their construction

Giza Pyramids in Egypt

No one in Egypt, and no one around the fertile crescent of Mesopotamia, had ever seen the Sun shine at night. The people could obtain a fair idea of time by the stars; but the remote heavenly bodies need careful observation and calculation if they are to give time truly. A man, wanting to know the approximate time of night, could not go out and glance at a shadow cast by a star on a dial. He had to perform a much more elaborate ritual. To fill the need for telling time casually and quickly at night, the Egyptians invented water clocks.

Almost simultaneously two kinds of water clocks were invented. The outflow clocks had to be refilled every evening at sunset. The water flowed out of a hole near the bottom. At sunrise they were empty. On the inside were marked twelve divisions, like the divisions in a measuring cup, and a man need only observe the level of the water to determine the correct time.

The principle was very simple, but the Egyptians expended a great deal of ingenuity and scientific care in their construction. Water flows swiftly under pressure, but as the pressure is decreased, the rate of its flow lessens. So in the evening, when the water clocks were newly filled, the water level would sink very fast; but toward morning, when most of the water had flowed out, the change would be quite slow.
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In antiquity, sand glasses were much less important than water clocks

Sand glasses vs. water clocks

In antiquity, sand glasses were much less important than water clocks, but their influence lasted longer. The middle ages took them, as the Greeks had taken the water clock–to time the length of speeches. Even in the sixteenth and seventeenth centuries they were to be found in every church. When the minister started preaching the clock was started, and when the sand had run out the minister must stop. There are certain common needs of humanity which reappear in every age.

We still see sand glasses today; they are sold as toys for children and as kitchen gadgets to time a boiling egg; but in only one place have they retained their original dignity. When a division is called in the English House of Commons, a two-minute sand glass is still turned; and, while the sand is running, the “division bells” are set in motion throughout the house.

The Greeks had yet another method of telling time. One which the Egyptians did not know, and which the Greeks probably invented themselves. There is a slight confusion about this, for Berosus (to whom the invention is attributed) seemed to have a bad habit of popping up at odd intervals in different countries and entirely different centuries, in a way that is quite extraordinary for a man who was himself a timekeeper. He is variously cited as a Chaldean who lived about 640 B. C. on the island of Cos, and as a Greek, living in Bithynia about 280 B. C. The latter, just to help out the confusion, wrote a history of Chaldea. Whatever his date, his fame at least has persisted, and at one time must have been greater than it is now.
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  • Important events in astronomical history