4 chinese astronomers recorded sunspots and aurora in

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4. Chinese astronomers recorded sunspots and aurora. In modern times, such records revealed: sunspots and aurora NATS 1745 (Oct 26. 2010 ) notes: Chinese astronomers recorded the temporary appearance of “new stars”, now called novac (Latin: “new”) or supernovac. (diagram: CH2-18) These events are really the temporary brightening of a dying star
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Novac and supernovac occur rarely and randomly in our Galaxy ( on average, 1/century ) Records of supernovac coordinates have been matched with present-day nebulac, proving: nebulac are supernovac remnants The recorded date of a supernova gives the age of its stellar corpse and the nebula’s expansion rate (-1000s km/sec) Astronomy in Ancient Egypt (3200-331BC) In ancient Egypt, survival depended on the annual flooding of the Nile River. Thus the sky was mainly studied for accurate time keeping. The annual cycle of the stars (diagram: CH2-20) due to earth’s annual orbit around the sun, our visible window of stars changes each night ( i.e. the stars we see depend on the time of year) The Egyptian Religious Calendar When a stars returns to the exact same position in the sky, earth has completed 1orbit (i.e. exactly 365.25 days have elapsed) Within the latitudes of Egypt, the heliacal rise of Sirius (the brightest start in the sky) coincides with the Nile’s annual flood . The heliacal rise was therefore used to mark each year. The origin of the leap year The government of Egypt established a civic calendar containing 12 30 day months (360 days) with 5 “leaps” days to stay synchronized with the 365-day seasonal cycle. Since the solar year = 265.242 days, the civic calendar gradually crept ahead of the seasons 239 BC: Ptolemy III added another leap day every 4 years: 4 year *365.242 dats/years =4365 day civic year + 1 day – 11.5min 46 BC: an the advice of the Egyptian astronomer sosigenes, Julius Caesar incorporated the 4-year leap-day into the Julian Calendar (a 365-day calendar with 12 months of 28, 30 or 31 days ) 16 th C: Pope Gregory XIII fixed the 11.5min error by decreeing : years divisible by 100 ( but not 400) are not leap years ( our modern Gregorian Calendar) The Origin of the 24-hour clock The Egyptians tracked time at night using a set of constellations which rise at approximately equal intervals. On average, 12 of these constellations rise each night , so the Egyptians divided night and day into 12 hours each Babylonian Astronomy (2000-331 BC) The Babylonians tracked the cycles of the sky, which they believed to foretell the future This was the origin of western astrology Each night, a record of the sky was entered a tablet , the daily records, combined with a book of interpretations, were used to predict the celestial events (and their omens) for the next year.
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