The Solstice Bash

1. TheSolstice 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 Celestial North Pole Celestial Equator East  North South West Geocentric View from the Ground Horizon

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

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.