1. Do Not Write What is in Yellow APPARENT MOTIONS OF THE CELESTIAL OBJECTS

2. Definitions  Celestial sphere: Imaginary sphere encircling Earth on which all object in the night sky appear  Celestial object: Object in the sky outside Earth’s atmosphere; the sun, moon, stars, planets  Terrestrial: Objects that are a part of Earth, such as rocks, oceans, and clouds

3. Motions The sun, moon, planets, stars or any distant object seems to rise in the east and set in the west- this is an illusion: the Earth is the object that is moving The apparent motion of objects occurs at a rate of 15 degree per hour, which is the rate that earth rotates Daily Motion: the movement of a celestial object over a 24-hour period Day: Average interval of time during which the sun passes from its highest point on one day to its highest point on the next; ~24 hours

4. Zenith: The point on the celestial sphere that is directly above the observer.

5. From Different Perspectives Mid-Latitudes: Stars appear to move from east to west in circular paths North Pole: Stars appear to move in a circle

7. STAR'S PATH THROUGH THE SKY The Earth rotates, causing the stars to appear to rise and set. Remember that the Sun is a star. It rotates/spins in place but does not revolve/orbit

8. Information Sundials were used to tell time using the apparent movement of the sun The passing of hours is indicated by the movement of the shadow Days are short during the winter because we are pointed away from the sun so the sun is below the horizon most of the day Sundials More on sundials

11. Path of the Planets  Planets do not remain in fixed positions among the stars  Planets change their position from night to night  Each planet has its own unique motion  Sometimes they appear to drift west, other times east  “Planet” = Wanderer

12. The Moon  The moon revolves around Earth in about 27 days  The moon rises about 50 minutes later each evening  The path of the moon varies from higher to lower depending on the time of year  The moon’s path is similar to the sun’s as it looks like it rises and sets

13. Apparent Motions of the Sun The sun appears to rise in the east, travel in an arc across the sky and set in the west The greater the length of the sun’s path over an area, the more hours of daylight In the spring and fall, the sun rises due (exactly) east and sets due west In the summer, the sun rises north of east and sets north of west In the winter, the sun rises south of east and sets south of west

15. Changes in the Altitude of the Sun at Noon The sun is always highest at local solar noon Only between the latitudes of 23.5 degrees North and 23.5 degrees South can the noon sun be directly overhead