1. Earth’s Seasons

2. Rotation 1.The imaginary line that passes through Earth’s center and the North and South poles is called Earth’s axis. 2.Earth spinning on its axis is called its rotation. 3.The equator rotates at about 1,600km/h 4.Earth’s rotation on its axis causes day and night.

3. Rotation 5. Earth rotates eastward or counterclockwise. 6. Sun appears to move westward across the sky. 7. Sunlight can’t reach the side of the earth facing away from the sun, so it is night. 8. It takes 24 hours to rotate once on its axis.

4. Revolution 1.Earth travels around the sun. 2.The movement of one object around another object is called revolution. 3.One complete revolution around the sun is called a year. 4.Earth’s path as it revolves around the sun is called its orbit.

5. How Sunlight Hits Earth 1.At the equator, sunlight hits Earth’s surface more directly. 2.Closer to the poles, sunlight hits Earth’s surface at an angle. 3.Near the poles, energy from the sun is spread out over a greater area.

6. Earth’s Tilted Axis 1.If Earth’s axis were straight up and down relative to the sun temperatures would remain constant year around. 2.Earth has seasons because its axis is tilted as it moves around the sun. 3.Earth’s axis is tilted at and angle of 23.5.

7. 4. As Earth revolves around the sun its axis its tilted away from the sun for part of the year and toward the sun for part of the year. 5. When the north end of Earth’s axis is tilted toward the sun, the Northern hemisphere has summer. 6. Summer and winter are not affected by changes in Earth’s distance from the sun. 7. When the Northern hemisphere is having summer, Earth is at is greatest distance from the sun.

9. Earth in June The north end of the Earth’s axis is tilted toward the sun. It has more hours of daylight than the hemisphere that is tilted away. It is summer in the Northern hemisphere and winter in the southern hemisphere.

10. Earth in December The southern hemisphere receives the most direct sunlight, so it is summer. The sun’s rays in the northern hemisphere are indirect and there are fewer hours of daylight, so it is winter.

12. June and December One two days each year, the noon sun is overhead, this is known as solstice. Winter solstice= December 21 for the northern hemisphere. It is the shortest day of the year. Southern hemisphere is having summer. June 21= summer solstice for the northern hemisphere. It is the longest day of the year.

14. March and September Neither hemisphere is tilted toward or away from the sun. This occurs 2 days of the year. Known as “equinox” which means equal night. Length of night and day are about the same. Vernal or spring equinox around March 21 in Northern hemisphere marks the beginning of spring. Autumnal equinox around September 23 in northern hemisphere marks the beginning of fall.