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Foundations of Astronomy Part 4. Question 7. a) during the new moon phase. b) when the Sun blocks the Moon. c) during the full moon phase. d) always around the summer solstice. A total lunar eclipse occurs. Question 7. a) during the new moon phase. b) when the Sun blocks the Moon.
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Question 7 a) during the new moon phase. b) when the Sun blocks the Moon. c) during the full moon phase. d) always around the summer solstice. A total lunar eclipse occurs
Question 7 a) during the new moon phase. b) when the Sun blocks the Moon. c) during the full moon phase. d) always around the summer solstice. A total lunar eclipse occurs
Eclipses Lunar Eclipse When the Earth passes directly between the Sun and the Moon. Sun Earth Moon Solar Eclipse When the Moon passes directly between the Sun and the Earth. Earth Moon Sun
Solar Eclipses Diamond ring effect - just before or after total Total Partial Annular - why do these occur?
Moon's orbit tilted compared to Earth-Sun orbital plane: Sun Moon Earth 5.2o Side view Moon's orbit slightly elliptical: Moon Distance varies by ~12% Earth Top view, exaggerated ellipse
Certain seasons are more likely to have eclipses. Solar “eclipse season” lasts about 38 days. Likely to get at least a partial eclipse somewhere. Animation It's worse than this! The plane of the Moon's orbit precesses, so that the eclipse season occurs about 19 days earlier each year.
Eratosthenes Determines the Size of the Earth in about 200 B.C. Sun's rays Syene Alexandria N 7.2o S Earth
He knows the distance between the two cities is 5000 "stadia". From geometry then, 7.2o 5000 stadia = 360o Earth's circumference => circumference is 250,000 stadia, or 40,000 km. So radius is: 40,000 km 6366 km = 2p (very close to modern value, 6378 km!)
Lecture Tutorial in Introductory Astronomy • Motion – Pages 3-6 (finish) • The Cause of Moon Phases, pages 79-81
POST-Tutorial Question • You are looking toward the north and see the Big Dipper to the right of Polaris. Fifteen minutes later, the Big Dipper will appear to have moved in roughly what direction? • east (to your right) • west (to your left) • up (away from the horizon) • down (closer to the horizon)
POST-Tutorial Question • How much time is there between when a star rises and when it sets? • less than twelve hours • about twelve hours • more than twelve hours • d) it depends on the star
Sun rise and sunset – variance with seasons • Demonstration