1. Earth’s Rotation and Revolution
What causes night and day?
What causes the seasons to change?

2. Rotation Night and Day Rotation Animation
What does Rotation mean?
Rotation means to spin. Rotation is when something is
spinning around an axis (imaginary line through its center).
What are some examples of things that rotate?
Tops, Ballerinas, Figure skaters, cyclones, a merry-go-round, Earth...
Night and Day
What causes night and day?
Rotation of Earth around the sun. The side that faces the sun is day. The side facing away from the sun is night
Earth rotates once on its axis in 24 hours.
The actual rotation is 23 hours, 56 minutes, 4.1 seconds
When viewed from above the North Pole, Earth rotates counterclockwise.

3. Revolution To revolve means to go around something. 365.242199
Earth revolves around the sun once every days, a year.
When viewed from above our solar system, Earth revolves counter clockwise around the sun.
Orbit is sometimes used as a synonym for revolution. Orbit really refers to the path taken as Earth revolves around the sun.
Leap Year
Yearly revolution around sun animation
Earth Movement Animation

4. Seasons What two things cause the difference in the seasons?
The angle of the sun’s rays
The length of the days
Earth’s Tilted Axis
The Earth is tilted on it’s axis at a 23.5 degree angle.
The Earth’s tilt is always in the direction of the North Star.
What is another name for the North Star?
Polaris
Earth’s tilt is what causes our days to get longer in the summer and shorter in the winter. (opposite in the Southern Hemisphere)
Earth’s tilt causes uneven heating of its surfaces by the sun.
Because of the Earth’s rotation the sun appears to rise in the east and set in the west.

5. Seasons NASA What Causes Seasons? NASA Planetary Seasons
When Earth’s Northern Hemisphere is tilted towards the sun it receives more direct solar radiation.
Angle of the sun is higher in the sky. More energy, heat and light per square meter.
When the angle of the sun is lower in the sky, we get indirect solar radiation. Less energy, heat and light.
In the Summer, the Northern Hemisphere gets more direct rays from the sun and the days are longer. (But we are farther away from Sun. aphelion ~152.6 million km, 94.4 million mi on ~7/4)
In the Winter, the Northern Hemisphere gets indirect rays from the Sun and the days are shorter. (But we are closer to Sun. Perihelion ~147.5 million km, 91.5 million mi on ~1/4)

6. YouTube Earth's Tilted Axis
Planetary Motion Animation
YouTube Earth's Tilted Axis