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Chapter 2

Chapter 2 - we find that 1 light-year we can convert...

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8 Chapter-by-Chapter Guide we find that 1 light-year 9.46 10 12 km, so we can convert: We can now find the ratio of the two diameters: The diameter of the Milky Way Galaxy is about 3.5 trillion times as large as the diameter of Saturn’s rings! 44. a. The circumference of Earth is 2 6,380 km 40,087 km. At a speed of 100 km/hr, it would take: to drive around Earth. That is, a trip around the equator at 100 km/hr would take a little under 17 days. b. We find the time by dividing the distance to the planet from the Sun by the speed of 100 km/hr. It would take about 170 years to reach Earth and about 6,700 years to reach Pluto (at their mean distances). c. Similarly, it would take 6,700 years to drive to Pluto at 100 km/hr. FYI: The fol- lowing table shows the driving times from the Sun to each of the planets at a speed of 100 km/hr. d. We are given the distance to Alpha Centauri in light-years; converting to kilometers, we get: At a speed of 100 km/hr, the travel time to Proxima Centauri would be about: It would take some 47 million years to reach Proxima Centauri at a speed of 100 km/hr. 45. a. To reach Alpha Centauri in 100 years, you would have to travel at 4.4/100 0.044 of the speed of light, which is about 13,200 km/s or nearly 50 million km/hr. b. This is about 1,000 times the speed of our fastest current spacecraft. = 4.7 * 10 7 yr 4.16 * 10 13 km , 100 km hr = 4.16 * 10 13 km * 1 hr 100 km * 1 day 24 hr * 1 yr 365 day 4.4 light years * 9.46 * 10 12 km 1 light year = 41.6 * 10 12 km 40,087 km , 100 km/hr = 40,087 km * 1 hr 100 km * 1 day 24 hr = 16.7 days = 9.46 * 10 17 km 2.7 * 10 5 km = 3.5 * 10 12 ratio = diameter of Milky Way diameter of Saturn’s rings 100,000 light years * 9.46 * 10 12 km 1 light year = 9.46 * 10 17 km Planet Driving Time Mercury 66 years Venus 123 years Earth 170 years Mars 259 years Jupiter 888 years Saturn 1,630 years Uranus 3,300 years Neptune 5,100 years Pluto 6,700 years Chapter 2. Discovering the Universe for Yourself This chapter introduces major phenomena of the sky, with emphasis on: The concept of the celestial sphere. The basic daily motion of the sky, and how it varies with latitude. The cause of seasons. Phases of the Moon and eclipses. The apparent retrograde motion of the planets, and how it posed a problem for ancient observers. As always, when you prepare to teach this chapter, be sure you are familiar with the relevant media resources (see the complete, section-by-section resource grid in Appendix 3

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Part I 9 of this Instructor’s Guide) and the online quizzes and other study resources available on the MasteringAstronomy Web site. What’s New in the Fourth Edition That Will Affect My Lecture Notes? As everywhere in the book, we have revised to improve the text flow, added optional Cosmic Calculations boxes, improved art pieces, and added new illustrations. The art changes, in particular, will affect what you wish to show in lecture. We have not made any substantial content or organizational changes to this chapter.
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Chapter 2 - we find that 1 light-year we can convert...

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