To truly understand what the sky and its lights are all about, human beings eventually realized they couldn't just rely on their eyes. They had to develop tools to help explore what stretched far above them. The telescope was the key invention in the progress to modern astronomy, but it took many thousands of years before anyone succeeded in inventing one. This is somewhat surprising since water's ability to change and sometimes magnify objects beneath the surface must have been noticed as early as caveman times. Glass was discovered around 3500 BCE, and crude lenses were even found in Crete and Asia Minor, dating from 2000 BCE. A number of well-respected writers as early as classic times reported about refraction, reflection, and magnification. But for some reason no one put together all these observations and discoveries in the right way until the early 17th century. Instead, ancient peoples used many other kinds of tools and aids to help them observe and track the stars and planets. Ancient sites like Stonehenge in Great Britain and the Egyptian pyramids are some of the earliest evidence we have that our ancestors made pretty accurate observations of the sky. We know that because these sites are aligned in special ways. At Stonehenge, for example, one can see the sun rise through one arch at the summer solstice, which is the time when the sun is at its farthest point north in the sky. The sun rises and slips just above a distant stone called the Heel Stone. [Krupp color slide of Stonehenge] Some sort of measuring tools were likely used to arrange the site in such an exact manner, to produce this effect. We may never discover just why this early society aligned their stones this way. It could be to create a "sacred space" for religious ceremonies or magical practices. It is now believed unlikely that Stonehenge was an early observatory, but there's little doubt that the alignment was made on purpose and that the sun was meant to appear where it does at that time. The pyramids in Egypt are also aligned in a specific way, but in their case it was to point at certain stars. Two shafts which lead down into opposite sides of the Great Pyramid at Giza open on one side to the star Thuban (at the time, the closest star to being the north star) and on the other to the stars in the constellation Orion's belt. [Krupp diagram of pyramids] But since the pyramid was built to be a tomb, like Stonehenge it is not considered an observatory. The pyramid was really a launching pad for the dead pharaoh's soul. The pharaoh was expected to travel to heaven and continue his destiny there, and the shafts pointed in such a way to symbolically guide him to his new, heavenly home. Actually, even a living person standing in the crypt could not see the alignment of stars, since the shafts were blocked. But the ancient Egyptians obviously had some dependable knowledge of the stars' positions in order to arrange the shafts' alignments in the first place. Many other ancient sites have been found, in Central and South America, the U.S., and Ireland, which suggest they were built to point at certain stars or the sun or moon. We will probably never know for sure why these structures or patterns were made, but their existence does at least prove that men and women have been interested in the sky's changes for a very long time, and that they kept close track of where heavenly objects appeared. As time went by, people devised portable aids to star watching that have survived for us to examine. Egyptians invented the merkhet, which was used by two observers facing one another. [picture of drawing of two people using merkhet. image 3: NEED drawing] Each one held a merkhet, and they sat lined up so that one could see the north star just above the other's head. The second person then sat very still as the first one watched and recorded when stars passed by the top of the other's head, by his ear, shoulder, etc. In this way, astronomical positions were recorded so people could predict how the stars moved. In Alexandria around the 2nd century, Ptolemy and his contemporaries invented more instruments for sky watching. To use a quadrant, one side was aligned with the horizon and the other pointed at the zenith, the spot in the sky directly overhead. Then a movable arm or bar was pointed at a certain star, to measure its distance above the horizon. [picture of quadrant; image 4: NEED drawing] Quadrants also could point to the sun and tell the time of day. They were used a lot even after the discovery of the telescope, since early telescopes couldn't measure exactly where a star was. From Alexandria, the center of learning moved to the Middle East, where Arabian astronomers used many fine star-measuring instruments. The astrolabe was either invented or improved at this time; it was used like a quadrant, except one held it by a ring at its top and gravity put it into position to measure the sun or stars. [drawing of astrolabe. image 5: NEED drawing] The cross-staff, just a simple cross with a movable bar, was invented by Jewish astronomer Levi ben Gerson (1288-1344). With a cross-staff, mariners could determine the angle between the moon and a star by sliding the bar so the two objects were aligned with the ends of the bar. Then the angle was read off a scale engraved in the middle. [picture of cross-staffs; image 4A: p. 81 Hoskin] Many instruments were constructed to be larger and larger, so that very exact measurements could be made. One quadrant built was 180 feet in size! Tycho Brahe (1546-1601), just before the age of the telescope, had huge instruments at his observatory, Uraniborg, built on an island off Denmark. There astronomers and their assistants could use quadrants and Tycho's improvement of the cross-staff, sextants. [picture of Stjerneborg ; image 5A: p. 107 Hoskin] Of these first observatories, built to house large instruments, few survive. While some were just abandoned, like Uraniborg, many in the Islamic world were destroyed when the benefactor or ruler who built it died. Astronomy was at this time tied up with astrology, and so star and planet positions were tracked mainly to forecast the future. But such fortune telling was forbidden by Islamic law. Sky watching was actually a risky pastime in those days. One such sponsor of an observatory was executed and his building and instruments destroyed, all because he was found guilty of, among other things, "communicating with the planet Saturn." It was this kind of superstitious belief that hampered the progress of astronomy. From the third through the 13th century, the ability of certain kinds of curved glass to magnify objects was variously reported, but such a thing seemed so amazing that it appeared to some to be "black magic." Claims made by a prospective discoverer were either disbelieved or liable to land that person in prison or to be burned at the stake. Not until the Renaissance, when the scientific age began to dawn, were people better prepared for the miracle of the telescope.
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