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

2. Rotation What does Rotation mean?
Rotation occurs when something is spinning around an axis.
What are some examples of things that rotate?
Tops, Ballerinas, Figure skaters, cyclones, Tornadoes, a merry-go-round, Earth
How do we know that the Earth rotates?
Star trails- trails made with time exposure, circular paths that occur because the planet is moving and not stationary.
Winds curve because of the Earth’s rotation.
Ocean currents curve clockwise in the northern hemisphere, and counterclockwise in the southern hemisphere.
The movement of a pendulum. It does not actually move, it is the Earth moving that causes the pendulum to appear to change the direction of its swing.

3. Night and Day What causes night and day? The rotation of the Earth
The side of the Earth that is facing the sun has daylight, the side of the Earth away from the sun has night.
It takes 24 hours for the Earth to complete one rotation.
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
This tilt is what causes our days to get longer in the summer and shorter in the winter.
Because of the Earth’s rotation the sun appears to rise in the east and set in the west.

4. Revolution
The motion of a body, such as a planet or moon, along a path around some point in space
Earth's orbit is elliptical
Earth is closest to the Sun (perihelion) in January
Earth is farthest from the Sun (aphelion) in June
The plane of the ecliptic is an imaginary plane that connects Earth's orbit with the celestial sphere

5. Seasons What two things cause the difference in the seasons?
The angle of the sun’s rays
The length of the days
There are two kinds of rays from the Sun:
Direct- occurs when Earth is tilted toward the Sun
Indirect-occurs when Earth is tilted away from the Sun
In the Summer, we get the direct rays from the sun and the days are longer. (But we are farther away from the Sun)
In the Winter, we get indirect rays from the Sun and the days are shorter. (But we are closer to the Sun)
Why does this happen?

6. What causes the seasons?
The Seasons are due to the Earth’s tilt of 23.5 degrees
When we tilt towards the Sun
The direct sunlight hits the Tropic of Cancer (23.5 degrees N Latitude)
the Northern Hemisphere experiences summer (Summer Solstice)
The Southern Hemisphere experiences winter (Winter Solstice)
When we tilt away from the Sun
The direct sunlight hits the Tropic of Capricorn (23.5 degrees S Latitude)
The Southern Hemisphere experiences summer
the Northern Hemisphere experiences winter

7. What causes the seasons?
The Seasons are due to the Earth’s tilt of 23.5 degrees
When we are sideways to the Sun (Not tilted towards or Away from the Sun)
The direct sunlight hits the Equator (0 degrees Latitude)
the Northern Hemisphere experiences spring or fall
The Southern Hemisphere experiences spring or fall
Spring is known as the Vernal Equinox
Fall is known as the Autumnal Equinox

8. Summary What is the difference between rotation and revolution?
Rotation occurs when an object spins around an axis.(24 hour Day)
Revolution occurs when an object spins around another object. (365 ¼ day per year)
Aphelion is Earth’s orbits farthest point away from the Sun
Perihelion is Earth’s orbits closest point to the Sun
23.5 degree Tilt causes Earth’s Seasons
Summer Solstice the Northern Hemisphere tilts toward the Sun
Winter Solstice the Northern Hemisphere tilts away from the Sun
Vernal Equinox the direct sunlight hits on the Equator after the Winter Solstice
Autumnal Equinox the direct sunlight hits on the Equator after the Summer Solstice
Tropic of Cancer is 23.5 degrees North Latitude
Tropic of Capricorn is 23.5 degrees South Latitude