By Hugh Thurston
People should have watched the skies from time immemorial. humans have continually proven highbrow interest in abundance, and sooner than the discovery of recent distractions humans had extra time-and extra psychological energy-to commit to stargazing than now we have. Megaliths, chinese language oracle bones, Babylonian clay pills, and Mayan glyphs all yield evi dence of early peoples' curiosity within the skies. to appreciate early astronomy we have to be conversant in quite a few phenomena that could-and nonetheless can-be visible within the sky. for example, apparently a few early humans have been attracted to the issues at the horizon the place the moon rises or units and marked the instructions of those issues with megaliths. those instructions plow through a sophisticated cycle-much extra complex than the cycle of the levels of the moon from new to complete and again to new, and extra advanced than the cycle of the emerging and environment instructions of the sunlight. different peoples have been attracted to the abnormal motions of the planets and within the manner within which the days of emerging of many of the stars diverse throughout the yr, so we have to learn about those phenomena, i. e. , approximately retrogression and approximately heliacal emerging, to usc the technical phrases. The booklet opens with a proof of those issues. Early astronomers did greater than simply gaze in awe on the heavenly our bodies; they attempted to appreciate the complicated info in their hobbies. by means of three hundred H. C.
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Let us consider how the Egyptians could have oriented the pyramids. They must have started by finding north or south-east and west are simply the directions midway between them and cannot be found directly. To find north or south accurately we must use the stars; the sun is too big and too bright to yield an accurate result. I describe one way in which north can be found on page 26. Another way would be to bisect the angle between the directions in which a star rises and sets, taking care that the horizon heights are the same at the two points, perhaps by building an accurately leveled wall some distance north of the observer and using this as a horizon.
What is the mathematical probability that a collection of point-to-point alignments could, by sheer chance, come so close to so many astronomically interesting directions? First, we must decide how accurate we can reasonably expect an alignment to be. Anyone who has moved a 100-kilogram stone (perhaps building an oriental garden) will know how difficult it is to place it exactly where it is wanted; and the stones of Stonehenge me much larger than that. Gerald Hawkins suggested 2° accuracy .
Thus from the two elevations of the sun we find both the obliquity and the latitude. This method has the practical difficulty that the solstice will usually occur not at noon but between noons, so the sun will not have reached its extreme declination when the measurement is made. We will see on page 98 how the Chinese dealt with this difficulty. 1. If we stand in the middle of them at dawn on the day of the summer solstice, we can watch the sun rise over a distant stone pillar known as the heel-stone.