1. Earth, Sun, and Moon Interactions
Unit 1- Astronomy
Earth, Sun, and Moon Interactions

2. Rotation
Spin/turn on an axis Earth’s tilt or axis is 23.5⁰ from the equator One rotation = one solar day (24 hrs/day) Foucault Pendulum- evidence of Earth’s rotation on its axis

3. Revolution Move around an object; to orbit
A path the Earth follows around the sun
Takes 1 year or days for Earth to travel around the Sun
Causes seasons

5. Solstice Summer Solstice- Winter Solstice-
Sun directly overhead at Tropic of Cancer
23.5 ⁰ north latitude
June 21 each year
Maximum daylight hours in northern hemisphere
Winter Solstice-
Sun directly overhead at Tropic of Capricorn
23.5 ⁰ south latitude
December 21 each year
Minimum daylight hours in northern hemisphere

6. Equinox Vernal (Spring) and Autumnal (Fall) Equinox
“Equal night”- 12 hours of daylight, 12 hours of night
Earth’s axis is NOT pointed at the Sun
Both hemispheres receive equal amounts of sunlight

7. Plane of Ecliptic = the plane in which Earth orbits around the Sun

8. Stop to Summarize
1.) What’s the difference between rotation and revolution? 3.) How does the Earth’s tilt influence the equinoxes and solstices?

9. Earth’s Shape OBLATE SHEROID
Equatorial Bulge- flattened sphere along the axis from pole to pole such that there is a bulge around the equator.
- caused by the rotation of the Earth
- the diameter at the equator is 43 km (kilometer) larger than the pole-to-pole diameter.

10. Precession Precession
Slow and continuous change in the orientation of a Earth’s rotational axis
Caused by the gravitational pull between the Sun and the Moon
Changes the stars near the Pole
Like a rotating toy top
Occurs over a period 26,000 years