Ch2 - Assignment: Chapter 2 Class: Astronomy I Date: August...

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Class: Astronomy I Date: August 28 th , 2007 Review Questions 1. Describe three structures or carvings made by past civilizations that show an understanding of astronomy. About four to five thousand years ago, the British inhabitants erected stone structures to show the location of the sun and some of the key times during the year. The ancestral Puebloans used stone carvings that were illuminated by the Sun on the first days of summer or winter to indicate the coming of the season. Also, the Incans of Machu Picchu used a narrow window carved in a rock to indicate the sunrise on December 21 st each year. 2. How are constellations useful to astronomers? How many stars are not parts of any constellation? The study of constellations provides a convenient framework for stating the position of an object in the heavens for the astronomers. Unaided human eye can only detect about 6000 stars. Because half of the sky is below the horizon at any one time, you can see at most about 3000 stars. 3. A fellow student tells you that only those stars in Figure 2-2 b that are connected by blue liners are part of the constellation Orion. How would you respond? A constellation is any one of the 88 areas into which the sky is divided. Orion is just one of the most well-known constellations today, but there are so many other spectacular constellations. 4. Why are different stars overhead at 10:00 P.M. on a given night than two hours later at midnight? Why are different stars overhead at midnight on June 1 than at midnight on December1? This daily motion is called the diurnal motion, in which it is the consequence of the Earth rotating once a day around an axis through its center and it also revolves once a year around the Sun. 5. What is the celestial sphere? Why is this ancient concept sill useful today? Celestial sphere is an immense hollow sphere that ancient societies believed to contain bits of fire imbedded in its inner surface as stars. While this concept placed the Earth in the center of the universe with the celestial sphere rotating around it, even today it is helpful to consider this concept to specify the directions of objects in the sky and to visualize their motions. 6. Imagine that someone suggests sending a spacecraft to land on the surface of the celestial sphere. How would you respond to such a suggestion? Celestial sphere is an imaginary object that has no basis in physical reality. 7. What is the celestial equator? How is it related to the Earth’s equator? How are the north and south celestial poles related to the Earth’s axis of rotation? The celestial equator divides the sky into northern and southern hemispheres, just as the Earth’s equator divides the planet into two hemispheres. The north and south celestial poles are where the Earth’s axis of rotation intersects the celestial sphere. Last Name: Sung
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Ch2 - Assignment: Chapter 2 Class: Astronomy I Date: August...

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