Earth rotates on its axis once every 24 hours. When your part of the earth faces the sun, you experience day. What happens to cause night? Video clip on day and night Rotation
East West Sun appears to rise in the east and set in the west because the Earth turns on its axis from west to east.
Revolution The time it takes to make one trip around the sun is a year. That is one revolution. Click here for an animation of a year.
rotation revolution Hyperlinks to animations of rotation and revolution.
Leap year It takes 365.24 days for Earth to do around the sun one time. This means we are not at the same place in our orbit as we began. Because of the 0.24 equals about ¼ of a day, we add a day to our calendar every 4 years. This year (2008) was a leap year so we had a February 29 th . Our next February 29 th will be in 2012.
Tilt of earth causes seasons. Video clip on seasons
Many people believe we have summer because we are closer to the sun in the summer. Look at the diagram and explain why they are wrong!
Bad Astronomy : Only on the day of the Vernal (spring) Equinox, can you stand a raw egg on its end. Good astronomy : If you can stand a raw egg on end, it has nothing to do with the Equinox. How it works : This has to be one of the silliest misconceptions around, and it never seems to die. Every year, without fail, some TV station broadcasts a news segment showing local schoolchildren standing eggs on end on the first day of spring . Usually, the newscaster will make some vague mention about how this works, but it is rarely specific, and never holds up to too much scrutiny.
The terminator is the moving boundary between day and night. Notice that it moves right to left. The moon does not make its own light. We see it because it reflects light from the sun.
Daytime on the moon Night on the moon Terminator
Phases of the moon are caused by the angle between the earth, moon, and sun.
Lunar Phase animation Another animation Video clip on phases Notice that the terminator is moving right to left.
Waxing means getting bigger every night. Waning means getting smaller every night. Crescent means less than half the surface of the moon facing you is lit by the sun. Gibbous means more than half of the surface of the moon facing you is lit by the sun.
Review this diagram and name the phases on the following slides!