1. The Solstice Bash Reasons for the Seasons

2. sunwatching How does the Sun’s path across the sky change from season to season? –When is the day longest? –When is the day shortest? Does the Sun always rise and set in the same place on the horizon? Does it always rise to the same height in the sky?

3. Morning on Earth The Sun rises on the eastern horizon. In the summer, the Sun rises to the north of east. In the winter, the Sun rises to the south of east.

4. Noon Noon is when the Sun reaches its highest point in the sky. In summer, this is higher in the sky than in winter. In Ithaca, is the Sun ever directly overhead in summertime?

5. Sunset Sunset is symmetrical with sunrise. If the Sun rises 10˚ north of east, it will set 10˚ north of west. Can we create a simple picture that shows how the Sun moves through the sky at different times of the year?

6. The Heliocentric View

7. The Geocentric View:

8. Celestial Sphere Geocentric View from the Ground Horizon NorthSouth East West Celestial North Pole Celestial Equator 

9. The Ecliptic Plane In the heliocentric picture, the ecliptic is the plane of the Earth’s orbit. What is the ecliptic in the geocentric picture?

10. TheEcliptic on the Celestial Sphere As the celestial sphere whirls once per day, the Sun creeps along the ecliptic. How will this affect the Sun’s path through the sky?

11. Changing Seasons North South East West Winter Solstice Summer Solstice Fall EquinoxSpring Equinox

12. Insolation Why is it colder in Winter? Not just because the days are shorter! When the Sun is low in the sky, its flux is more spread out.