ASTR 100 Week 5 Notes
ASTR 100 Week 5 Notes ASTR 100
Popular in Introduction to Astronomy: Solar System and Beyond
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This 2 page Class Notes was uploaded by Sarah Gardner on Sunday February 14, 2016. The Class Notes belongs to ASTR 100 at Ball State University taught by Dr. Bob Berrington in Fall 2016. Since its upload, it has received 24 views. For similar materials see Introduction to Astronomy: Solar System and Beyond in Astronomy at Ball State University.
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Date Created: 02/14/16
ASTR 100 Week 5; Section 3 cont I. Intersection of the Celestial Equator and the Ecliptic a. Equinox i. Sun is on the celestial equator ii. Vernal Equinox (zero point on calendar – March 21) iii. Autumnal Equinox (Sept 2223) b. Solstice i. Point where Sun is furthest North or South ii. Northern Hemisphere 1. Summer = Furthest north (June 21) 2. Winter = Furthest south (Dec 21) iii. Southern Hemisphere 1. Summer = furthest south 2. Winter = furthest north II. Seasons a. Earth’s orbit is (nearly) circular b. Seasons are caused by the tilt of earth’s axis, not different distances from the sun i. Causes sunlight to be more/less direct ii. Changes length of the day c. Drawing a bowl diagram for the orbit of the sun i. Went over in class, the picture is an example done for the Southern Hemisphere, 30 degrees South on 12/21 ii. Insert Picture here III. Zodiac a. Astrological sign i. Defined by ecliptic ii. Constellation in the path of the sun iii. Established around 2000 BC (by the Babylonians) iv. 12 main constellations b. Precession i. The ecliptic moves on the sky over long time scales (1000s of yrs) ii. One actually should take a program and go back to 2000 BC to see the true astrological sign c. Eratosthenes of Cyrene i. Measured the diameter of the earth – did a lot of research while in Alexandria, Egypt ii. How? 1. Noticed the sun shone at the bottom of a well in Syrene 0 2. At the same time, the obelisk in Alexandria gave a 7 angle from straight above 3. The distance between Syrene and Alexandria is 1/50 of the circumference of the earth a. Result: 46,620km b. One can find the radius of the earth once you have the circumference [use algebra with d(circumference) = 2(pi)r] d. Aristarchus of Samos i. Measured relative sizes of the Earth and moon ii. Used lunar eclipses iii. Found the moon to be 0.35 time Earth’s radius (correct ratio calc by modern astronomers = 0.27