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Lecture 5

Lecture 5 - Babylonian Astronomy, Astronomy in Ancient Greece.docx

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York University
Natural Science
NATS 1745
Robin Metcalfe

Babylonian Astronomy (2000 BC) • 1.The babylonian traveled the celestial cycles because they believed that the sky foretold the future. • 2.each night, a record of the sky was entered on a tablet. The daily recorded combined with the book of interpretations, were used to predict the celestial events (and their omens) for the next year. • The Babylonian tablet as shown as above • These predictions about the future were seen as warnings from the sky • Babylonian number system shown above • 3.babylonians numbers • A base-60system (I.e consisting of numbers for 1-60 multiplied by the power of 60), because 60 has many factors (a convenient base for division) • They therefore used numbers that are multiples of 60: • EG. 60 min=1 hr, 60 sec= 1 min, 360 degrees = 1 circle, 60 arc minutes =1 degrees, 60 arc seconds = 1 arc minute) • They borrowed the 24 hour day from the Egyptians • 4.The Zodiac o The Babylonian's divided the stars into groups (constellations) and passed on their descriptions to the ancient Greeks, from whom today's constellations names originate o The constellations on the elliptic (the zodiac constellations: Greek for "circle of animals" held a special importance, as the sun, moon and stars move along this strip of sky o Your zodiac sign in the suns constellation in the month you were born Due to the procession f the equinoxes the suns constellations have changed, since te zodiac signs were assigned 2000 years ago • 5.The Babylonian named the 5 visible planets after the Gods they best describe. The ancient Greeks adopted this practice, which led to the Greeks, then Latin planet names we use today o Mercury: (speedy, scribe/ messenger god); named for its fast motion across the sky; in fact it only takes 88 days for mercury to finish its path across the sky o Venus: goddess of love and beauty; named for its brightness; Venus is comparable to earths size; it is also the closest planet to us o Mars: god of war/bloodshed: named for its red color; the red color is hard to see today due to light pollution but back then it was quite visible, this red color is due to its high concentration of iron o Jupiter: father of the gods; named for its brightness and majestic motion; it is the second brightest planet; it is also huge compared to the earth and also moves very slowly across the sky o Saturn: god of old age/harvest : named for its faintness and slow motion; god of agriculture • 1.the possibilities: o Supernova: the explosive death of a massive star (can appear as a temporary star: "nova Stella" = Latin for new star); o Nova: the re-ignition of a dead star which has yanked fresh gas (star fuel) from a companion star (can appear as a sudden, temporary star) o Comet: a rocky snowballing orbit around the sun (can appear as a temporary star) o However there is a problem, all of these occurrences can be seen from half the planet, however there is no other records of this occurrence, including ancient Chinese records which have been kept in great detail for thousands of years. Chine falls under the same latitude • A planetary conjunction seen above and in the animation : • 2.a supernova, nova or comet is unlikely,
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