Earth’s Movements

1. Earth is not a perfect sphere. It bulges at the equator and is somewhat flat at the poles.

2. Earth spins like a top. The imaginary center line around which Earth spins is called Earth’s axis.

3. The spinning of Earth on its axis is called rotation.

4. A rotation takes about 24 hours.

5. Scientists hypothesize that the movement of material inside Earth’s core, along with Earth’s rotation, generates a magnetic field. Earth’s magnetic field protects you from harmful radiation.

6. Earth’s rotation causes day and night.
Another movement of Earth is called revolution. Revolution is Earth’s orbit, or the path of Earth, as it goes around the Sun. It takes a year for Earth to orbit the Sun.

7. The shape of Earth’s path around the Sun is an ellipse (ee LIHPS)—a long, curved shape, similar to a stretched-out circle.

8. Earth is closest to the Sun around January 3, and farthest from the Sun around July 4.

9. If Earth’s distance from the Sun caused the seasons, January—when the Earth is nearest to the Sun—would have the warmest days.

10. Earth’s axis is tilted 23.5 degrees

11. The tilt explains why Earth receives such a different amount of solar energy from place to place during the year.

12. In the northern hemisphere, summer begins in June and ends in September. This is when the northern hemisphere is tilted toward the Sun. During summer, there are more hours of sunlight—or solar energy. Longer periods of sunlight are one reason that summer is warmer than winter, but this is not the only reason.

13. Earth’s tilt causes the Sun’s radiation to strike the hemispheres at different angles. Sunlight strikes the hemisphere tilted toward the Sun at an angle closer to 90 degrees than the hemisphere tilted away.

14. Summer occurs in the hemisphere tilted toward the Sun, when its radiation strikes Earth at a high angle and for longer periods of time.

15. The solstice is the day when the Sun reaches its greatest distance north or south of the equator.

16. Summer solstice is the longest period of daylight of the year.

17. The winter solstice is the shortest period of daylight of the year.

18. An equinox (EE kwuh nahks) occurs when the Sun is directly above Earth’s equator.

19. Two times a year the Sun is directly over the equator. This results in the spring and fall equinoxes

20. During an equinox, neither the northern hemisphere nor the southern hemisphere is tilted toward the Sun. The number of daylight hours and nighttime hours is nearly equal all over the world.