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1. Which one of the following is true with regards to the ecliptic? 

1. Which one of the following is true with regards to the ecliptic? 

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1. Which one of the following is true with regards to the ecliptic? 

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  1. 1. Which one of the following is true with regards to the ecliptic?  a.  The ecliptic traces out the plane of the north and south celestial poles in the sky.b.  The ecliptic is defined as the eliptical path of the Earth on the horizon.c.  The ecliptic is defined as the intersection of the zodiac with the celestial equator.d.  The ecliptic traces out the path of the Sun in the sky over the course of the year.

  2. Announcements: • Homework #3 due Tuesday; Keep a close eye on the weather. • Reading: 2.1-2.5

  3. Review: • Ecliptic/Zodiac • Sky Charts • Planisphere • Today: • Classical Astronomy

  4. 2. Which direction should you face to see Draco at 9PM on tonight? a) North b) South c) East d) West

  5. 3. Which of the following sketches shows the correct appearance of the Big Dipper at 9PM tonight? A) B)

  6. This constellation can be seen in the northwest about halfway up to zenith at 9PM tonight. a) Auriga b) Eridanus c) Ursa Major d) Leo e) Cassioppeia

  7. Angular Size Depends on distance and actual size.

  8. 1º 20º 10º

  9. Arm must be straight!

  10. Astronomy Through the Ages: Classical All that is required to measure the diameter of the Earth is a person with stick and a brain. -adapted from Big Bang, Simon Singh, p.13

  11. Shape of the Earth

  12. How do we know the Earth is round? Devise a feasible experiment that can be completed in less than one day to prove to me that the Earth is round (or, at least, not flat). • Watch a ship sail away. • Make a long-distance phone call at sunset. • Observe a lunar eclipse. • Travel to the southern hemisphere and look at the stars.

  13. Different stars visible in the southern hemisphere

  14. Earth’s shadow is round as seen during an eclipse

  15. Size of the Earth

  16. How Big is the Earth? • Bigger than the Moon! • Eratosthenes • 200 BC • Greek mathematician, geographer • Curator of library of Alexandria (Egypt) • Compared observations of Sun taken in Alexandria • to those taken in Syene.

  17. 7° 7° How Big is the Earth? • Sun at noon on summer solstice in Syene is straight overhead. • Sun at noon on summer solstice in Alexandria is 7 degrees off the zenith.

  18. Second largest city of Egypt; main port Aswan Dam, Egypt

  19. 7° 7° To Sun Distance between Syene and Alexandria: 5000 stadia (800 km)

  20. Suppose you were an alien living on the fictitious warlike planet Myrmidon and you wanted to measure its size. The planet’s “sun” is shining directly down a missile silo 1000 miles to your south, while at your location, it is 36 degrees from straight overhead. What is the circumference of Myrmidon? • 36,000 mi • 3,600 mi • 10,000 mi • 6,280 mi • 1,590 mi

  21. Size of the Earth + Lunar Eclipse Observations Size of Moon!!!

  22. Size of the Moon + Angular Size in Sky Distance to Moon!!!

  23. Distance to the Moon + Quarter Moon Observation Distance to Sun!!!

  24. Distance to the Sun + Angular Size in Sky Size of Sun!!!

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