1. Earth-Moon Systems By Gina Wike

2. Earth’s Shape A sphere is a round 3 dimensional object whose surface at all points is the same distance from the center. The Earth is not a perfect sphere; it bulges at the equator and is flat at the poles. Space probes and satellites have shown us that the earth is sphere-shaped.

3. Rotation The spinning of the Earth on its axis is called rotation. Because Earth spins on its axis, the sun appears to move across the sky. One complete rotation takes about 24 hours or one day.

4. Revolution Revolution is the earth’s yearly orbit around the sun. It takes 365 days or one year to make one complete revolution.

5. Earth’s Orbit The Earth’s orbit is an ellipse. The sun is offset from the center. Because of this the Earth is closer to the sun on January 3 and further away on July 4.

6. Earth’s Orbit The amount of solar radiation changes very little throughout the year

7. Seasons Earth’s axis is tilted 23.5 degrees—this is what causes the seasons. Daylight hours are longer for the hemisphere tilted toward the sun. The hemisphere tilted toward the sun also receives more solar radiation.

8. Equinoxes & Solstices

9. Equinoxes An equinox is when the sun is directly above the equator. The number of daylight and nighttime hours are equal all over the world.

10. Equinox Neither the northern or southern hemisphere is tilted toward the sun. Northern Hemisphere- spring equinox- March 20 or 21; fall equinox- September 22 or 23; 0pposite in S. Hem.

11. Solstices A solstice is when the sun reaches its greatest distance north or south of the equator. Northern hemisphere- summer solstice-June 21 or 22; winter solstice- December 21 or 22

12. Solstices When the sun is at summer solstice, there are more daylight hours than during any other day of the year. When the sun is at winter solstice, we have the shortest day and the longest nights.

13. Moon Just as Earth rotates on its axis and revolves around the sun, the moon rotates on its axis and revolves around Earth. The moon’s revolution causes changes in its appearance.

14. Moon Phases Because the moon rotates on its axis in the same amount of time as it revolves around the earth, the same side of the moon always faces the earth. The moon’s phases depend on the positions of the moon, Earth, and sun.

16. Moon Phases When more and more of the lighted side of the moon becomes visible, this is known as waxing. The full moon is when the half of the moon facing earth is lit up. After the full moon, the lighted side of the moon that can be seen becomes smaller. (this is waning) The complete cycle of the moon’s phases takes about 30 days or a month.

17. Eclipses Eclipses occur when Earth or the moon blocks the sunlight reaching the other. LunarSolar

18. Eclipses Sometimes during the new moon a shadow cast by the moon falls on Earth and causes a solar eclipse. During full moon, a shadow of Earth can be cast on the moon resulting in a lunar eclipse. Eclipses only occur when the sun, moon, and earth are perfectly lined up.

19. Solar Eclipse A solar eclipse occurs when the moon moves directly between the sun and Earth and casts a shadow on part of Earth.

20. Solar Eclipses The darkest part of the shadow is called the umbra. A person in the umbra sees a total solar eclipse.

21. Solar Eclipse The atmosphere is the only part of the sun that is visible; it’s a pearly white glow around the moon. (corona) CAUTION: never look directly at a solar eclipse. The light will permanently damage your eyes.

22. Solar Eclipse The penumbra is a lighter shadow surrounding the umbra on the earth’s surface. People in the penumbra see a partial solar eclipse.

23. Lunar Eclipse A lunar eclipse is when the Earth’s shadow falls on the moon. A total lunar eclipse occurs when the moon moves into the Earth’s umbra. A partial eclipse is when the moon is in the penumbra.

25. Moon Features Maria are dark- colored, relatively flat regions on the moon.

26. Moon Features Craters are depressions on the moon caused by meteorite impacts.