How the Sky Moves, 6 September 2013!The study of how objects in the sky move used to occupy more of 1.astronomer's time in the past (1880s), partially because they did not have the technology to study the physical nature of the objects themselves. They noticed that:!Different constellations are visible in each season: !A.if you look east in autumn, you will see Cassiopeia, Perseus, and the a.square of Pegasus !if you look east in winter, you will see Perseus overhead, Orion, the b.twins, the bull, and the Pleiades star cluster !in spring, you will see Boötes, the arc of Taures, the big dipper, and c.others !in summer, you will find find summer triangle of stars (Deneb, Altair, d.Vega)!in general, the constellations seem to move upward and to the west. !e.this was the first problem addressed by astronomers.!1.Stars appear to rise in the east and set in the west, or move around the B.poles every night: !You can see the motion of the stars by taking a picture with a long a.exposure. !If you point your camera towards the north or south poles, you will 1.see a strongly curved star patterns encircling the poles (because the stars themselves seem to circle the poles).!If you points your camera towards the equator you will see basically 2.straight star patterns that rise from the eastern horizon, cross high in the south, and set in the western horizon. !This happens because the earth is spinning: !b.The stars appear to rise in the east because the east horizon is 1.descending to uncover them.!The stars appear to set in the west because the western horizon is 2.rising to cover them up. !Where the sun rises, arcs through the sky, and sets depends on the season:!C.In summer, the sun rises north of east, arcs high in the sky, and sets a.north of west. !On the summer solstice, the sun rises at its farthest north, rises to its 1.highest vertical point in the sky and sets its farthest north.!In winter, the sun rises south of east, arcs lower in the sky, and sets b.south of west. !On the winter solstice, the sun rises at its farthest south, doesn't get 1.up very high in the sky, and quickly sets south of west.!On the equinoxes March 21 and September 23, the sun rises due east, c.and sets due west. !The sun's angle causes the seasons: !d.When the suns rays come more from the north than the south, the 1.northern hemisphere gets more sunlight (solar energy) and they have summer. !When the sun's rays come more from the south than the north, the 2.southern hemisphere gets more sunlight and they have summer!Watching the motion of the sky has practical applications: !2.It can help you find your bearings (north, south, east, or west)!A.For example, the direction the stars and sun rise from is east.!a.The point where the sun rises can tell you the season: !B.For the northern hemisphere, the sun rises farther to the south during a.the winter and farther to the north in the summer. !For example: !C.Used for calendaring by the Hopi to know when to plant and harvest a.their crops.!it gets warmer as the sun migrates north from the winter solstice.!1.it gets colder as the sun migrates south from the summer solstice.!2.Hunter-gatherer societies could also have used the position of the sun to b.predict animal migrations and fruit seasons.!People have been watching the horizon since before recorded history: !3.Stone Henge:!A.located in England, Salisbury plain, west of London!a.the most famous megalith (big stone monument)!b.more the 4,000 years old (older than writing)!c.no one knows who built it!d.probably used for calendaring!e.The structure of stone henge is composed of a semi circle and a f.complete circle of stones. There is an avenue that travels between the center of three main arches which leads to a "heel stone." If you look through these arches from a central altar stone on the day of the summer solstice, you will see the sun rise above the heel stone. !You can also see the winter solstice sun set over the heel stoneon the 1.rare chance that it is not cloudy. !Stone Henge imitations:!g.A nearly full scale model in Maryhill, Washington on the Columbia 1.river near mount Hood and Portland!The heel stone is unfortunately too close because the river is A.where the heel stone should be.!Two in texas, one in Michigan!2.One in Odessa texas is the closest in scale, but has only inner A.stones and they are brown and sharply cut. !The others are the wrong size or leave things out. :!B.Most people only know about stone henge, but in reality there are B.hundreds of megaliths throughout British isles and mainland Europe: !Avebury: bigger than stone henge, but it has a lot fewer stones and no a.known alignment. !Carnac: an enormous field of stones stretching many kilometers wide !b.located in mainland Europe (France)!1.3000-4000 years old!2.Its use is highly debatable: !3.Right now, it is a summer resort in France.!A.The lines of stones are approximate and not precise enough for B.astronomic work, and they weren't at the time they were built.!One hypothesis is that the stones were placed by rival clans.!a.the use of most of the other stone groupings are equally debatable!C.There are also bigger, more deliberate monuments on the American C.continent and in India: !"Temple of the Sun" and "Temple of the Moon" pyramids at Teotihuacan, a.Mexico!Built by the Mayans!1.Information shows that they were for the sun and moon, but 2.astronomers are not sure exactly what astronomical purpose they serve.!Cahokia Mounds State Park, immediately east of St. Louis Missouri !b.There were 150 mounds, but about 70 mounds remain today. !1.There are also many holes, some of which have been filled in today 2.with wood poles.!If you look east over the edge of Munt's Mound, towards one of A.the filled in holes, you can see the direction of the equinox sunrise.!Another pole will give you the summer solstice and the winter B.solstice.!No one knows what other 80 holes in the ground are for. !C.5 observatories built by Majaraja Jai Singh II in his capital Jaipour, old c.Delhi, Varanasi, Ujjain, and Matura (India)!Built in in the early 1700s !1.The astronomy of this time was still interlaced with astrology, but A.the exact measurements of astronomical phenomena is partially what helped separate it from the voodoo of astrology. !They contained very large, and therefore very accurate scientific 2.instruments to view the motion of the sun, moon, planets, and star. !For example, there were large versions of sundials which measured A.the time
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