Early Astronomy

People must have watched the skies from time immemorial. Human beings have always shown intellectual curiosity in abundance, and before the invention of modern distractions people had more time-and more mental energy-to devote to stargazing than we have. Megaliths, Chinese oracle bones, Babylonian clay tablets, and Mayan glyphs all yield evi­ dence of early peoples' interest in the skies. To understand early astronomy we need to be familiar with various phenomena that could-and still can-be seen in the sky. For instance, it seems that some early people were interested in the points on the horizon where the moon rises or sets and marked the directions of these points with megaliths. These directions go through a complicated cycle-much more complicated than the cycle of the phases of the moon from new to full and back to new, and more complicated than the cycle of the rising and setting directions of the sun. Other peoples were interested in the irregular motions of the planets and in the way in which the times of rising of the various stars varied through the year, so we need to know about these phenomena, i. e. , about retrogression and about heliacal rising, to usc the technical terms. The book opens with an explanation of these matters. Early astronomers did more than just gaze in awe at the heavenly bodies; they tried to understand the complex details of their movements. By 300 H. C.

Contenu

1. Early Stargazers.- The Celestial Bowl.- The Constellations.- The Rotation of the Heavens.- Small Irregularities.- The Sun.- The Directions of Sunrise and Sunsets.- The Irregular Sun.- The Moon.- The Direction of Moonrise.- The Cycles of the Moon.- The Irregular Moon.- Eclipses.- The Luni-Solar Calendar.- The Planets.- Venus Observed.- Rising Azimuths.- The Stars.- Heliacal Risings.- Precession.- Precession and the Pyramids.- The Astronomer's Tools.- Celestial Latitude and Longitude.- Armillaries.- Polar Elevations and the Obliquity of the Ecliptic.- 2. Megalithic Astronomy.- Stonehenge.- Other Megalithic Structures.- 3. The Babylonians.- Early Period.- The Mul-Apin Tables.- The Zodiac.- Observations.- Sexagesimal Numerals.- Late Period.- The Sun.- The Moon.- Latitude.- The Lengths of the Months.- System B.- Lengths of Fundamental Periods for the Moon.- The Planets.- 4. The Egyptians.- 5. The Chinese.- Chinese Units.- Units of Length.- Dates.- Time of Day.- Cosmology.- Almanacs.- The Length of the Year.- Official Records.- Noon Shadows.- A Tang Dynasty Survey.- The Exact Instant of the Solstice.- Later Developments>.- The Length of the Year.- The Obliquity of the Ecliptic.- Celestial Motions.- The End of the Story.- 6. The Greeks.- The Early Thinkers.- The Classical Greeks.- Meton and Euctemon.- The Greek Zodiac.- Eudoxus.- Aristotle.- The Size of the Earth.- Does the Earth Move?.- Aristarchus.- Hipparchus.- The Length of the Year.- Periods of the Moon.- Table of Chords.- The Sun's Motion.- The Moon's Motion.- Precession.- A Possible Origin for the Constellations.- Ptolemy.- The Sun.- The Moon.- The Distance of the Moon.- The Distance of the Sun.- Eclipses.- The Stars.- The Planets.- Mercury.- Venus.- Mars.- Accuracy.- Calculations from the Theory.- Latitudes.- Note on the Epicycle Theory.- Closing Remarks on the Almagest.- The Ptolemaic Universe.- 7. The Astronomy of ?ryabha$$ \mathop t\limits_. $$a.- The Sun.- The Moon.- The Planets.- Further Topics.- Unwritten Astronomy.- 8. Arabic Astronomy.- 9. The Mayas.- The Moon.- Venus.- Eclipse Table.- The Accuracy of the Maya Calendar.- 10. The European Renaissance.- Copernicus.- Tycho Brahe.- Kepler.- The Latitude of Mars.- The First Theory of Mars.- The Earth.- Mars Again: Is its Orbit a Circle?.- The Orbit of Mars Is an Ellipse.- Kepler's Laws.- Appendix 1. Hipparchus's Table of Chords.- Appendix 2. Calculation of the Eccentric-Quotient for the Sun, and the Longitude of its Apogee.- Appendix 3. Ptolemy's Table of Chords.- Appendix 4. Calculating the Radius of the Moon's Epicycle.- Appendix 5. The Eccentric-Quotient and Apogee of Mars.- Appendix 6. Reversed Epicycles.- Further Reading.- Sources of Information.