ASTRO103 .pdf - Astronomy: natural science that studies the...

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Astronomy: natural science that studies the physical characteristics and history of the universeas a whole and the individual celestial objects with inSection 1.1Scales and Content of the universe-The universe is huge1.3Motions of objects in the sky-The stars trace our circular paths-The sun moves along the zodiac-The planets trace their own paths-Mars, jupiter, and saturn show retrograde motion-Mercury & venus never stray far from the sunEarly Models (geocentric)-Aristotle (384-322BC): nested spheres for “perfection”-Ptolemy: 140AD: Epicycles (wheels upon wheels)Early Astronomical measurements1.The earth is round2.The motion of heavens in perfect3.Earth is stationary and is located at the center of the universe-Aristarchus: distance & Size of the mood (280 BC)-Measure the relative scale of the moon-Shadow of the moon on earth, sun is bigger than earth-Began experimenting-Eratosthenes: Size of the earth (200BC)-Director of great library in alexander-Geographer at heart-Circumference of the earth → a little over 40,000 kilometers-Hipparchus: stellar magnitude scale (150 BC)-Created first stella catalog-Perfected aristarchus measurements of moon’s size and distance-Discovered earth's precession-Determined the length of the year within 6 mins of accuracy-Invented astrolabe-Precursor to mechanical clocks, sextants, and planispheres-Invented the stellar magnitude scale-1 Magnitude → intensity ratio 2.5, usual differenceRetrograde motion-The superior planets (Mars, Jupiter, Saturn) from time to time appear to reverse direction-Geocentric system: The epicycle swings the planet back briefly-Heliocentric system: as earth passes the planet, it appears to move backward“Retrograde motion is the apparent backwards motion of a planet with relation to backgroundstars. It is caused by angles in which the planet is viewed during different points of its orbit.”
1.4-Copernicus (ideas)-1473- 1543, roman catholic-heliocentric universe → everything revolves around sun, proposed amathematical explanation-99 years of astronomy→ time it took to confirm heliocentric-Occam’s razor: many times the simpler answer is correct-Planets travel in circular orbits, perfect (incorrect)-Planets move at constant speed (incorrect)-Motion of sun and stars is cause by earth's rotation and revolution-Stars are extremely distant-Heavenly throne at outermost celestial sphere-(hell, farthest from god, at center of earth)-According to aquinas, angels moved the planets-Sun, not outermost crystalline sphere, had throne of god-Planets moved because circular motion was natural and perfect-Equants were not circles and not perfect-Book → on the revolutions of the heavenly spheres-Right: simpler, predicted retrograde motion, predicted relative distances-Perspective affect, faster planet moving past slower, illusion-Relative to backward stars-Elongation-The angle between a planet and the sun-inferior → mercury venus-Inferior conjunction- elongation of 0 on the near side of sun-Orbit:, 1AU, the size of orbit is obtained from its value of greatestelongation

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Term
Spring
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dacis

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