|OBJECTIVE||Observe how different angles between the sun, earth and moon affect the phases of the moon we see each month.|
|OVERVIEW||Students, acting as the earth, will see differences in light and dark sides of their handheld moon.|
|TOTAL TIME||10 minutes|
|SUPPLIES||Table lamp (or another light source) for class. (A clear light bulb will work better than a frosted bulb.)
Per pair of students: pencil, white Styrofoam ball (approximately two to three inches in diameter).
|PRINTED/AV MATERIAL||Observation form (pdf)|
|TEACHER PREPARATION||A room that can be darkened.|
|SAFETY FOCUS||Rip Currents|
The moon orbits the earth approximately every 27¼ days. The moon reflects sunlight on to the earth. It is over a quarter of Earth's diameter which is much larger in comparison with its planet than any other in the solar system.
However, despite its size, gravity on the moon is about a sixth of that on the earth. For example, an object weighing 100 pounds on the earth would weight only 17 pounds on the moon.
Because there is no atmosphere on the moon, there are no weather systems. The lack of atmosphere also means there are large temperature swings from the sunlit side to the dark side. On the sunlit side, temperatures are as high as 250°F (>100°C) falling to as low as -250°F (-173°C) on the dark side.
- Divide the students into pairs and distribute one observation form to each student.
- Place a lamp on a table or desk and remove the shade. Turn the lamp on.
- Stick the Styrofoam ball on the pencil.
- Darken the room.
- Have one of the pair of students hold the ball, by the pencil, at arms length blocking out the light from the lamp. Explain they represent the earth, the ball is the moon, and the lamp is the sun.
- Comparing the light and dark side of the ball, on the observation form, under the "View from Earth" column, have that person draw/shade what their "moon" looks like. Have the student label this as "New Moon".
- Have the other person mark the location of the moon relative to the earth and sun on the dotted line (representing the Moon's orbit) under the "Position in Space" column.
- Have the student holding the "Moon" rotate 45° counter-clockwise. Repeat steps 6 and 7. Label this as "Waxing Crescent".
- Rotate another 45°. Repeat steps 6 and 7. Label this as "First Quarter".
- Repeat steps 6 and 7 for each additional 45°, labeling them as "Waxing Gibbous", "Full Moon", "Waning Gibbous", "Last Quarter", and "Waning Crescent" respectfully.
- Have the students switch positions and repeat the process again.
Spring/Neap Tide Wheel
Black Background (1.4 mb)
White Background (1.4 mb) Each student will see their "moon" from two vantages points; from earth's viewpoint and from "space". They should quickly observe that the position of the moon, relative to the earth and sun, is the reason for the various phases of the moon.
They will also observe the phenomena at the new and full moon positions. At "new moon", when the moon is between the earth and sun, the moon will block the sun's light, called a solar eclipse. At "full moon", the earth blocks light from reaching the moon causing the moon to be darkened. This is called a lunar eclipse.
You can explain that since the moon's orbit is inclined to the earth's equator that these eclipses typically occur just twice a year. Also, as the moon orbits the earth, the moon's tidal pull also moves around the earth. As a result, the difference between the height difference and times of high and low tides changes each day.
When the moon, earth and sun are inline (twice a month), the tidal pull by the moon and sun are at their greatest producing "Spring Tides", where the difference between the daily high and low tide are at their greatest.
When the earth, moon and sun are at right angles to each other (also twice a month), the difference between the daily high and low tides are their least, called "Neap Tides". The "Spring Tide or Neap Tide" wheel (above right) can be printed and cut-out to help illustrate how the orbit of the moon affects the spring and neap tides.
Rip currents are the leading surf hazard for all beachgoers. They are particularly dangerous for weak or non-swimmers. Rip current speeds are typically 1-2 feet per second. However, speeds as high as 8 feet per second have been measured--this is faster than an Olympic swimmer can sprint! Thus, rip currents can sweep even the strongest swimmer out to sea.
Rip currents can be found on many surf beaches every day. Under most tide and sea conditions the speeds are relatively slow. However, under certain wave, tide, and beach profile conditions the speeds can quickly increase to become dangerous to anyone entering the surf.
Learn how to swim!
- Never swim alone.
- Be cautious at all times, especially when swimming at unguarded beaches. If in doubt, don't go out!
- Whenever possible, swim at a lifeguard protected beach.
- Obey all instructions and orders from lifeguards.
- If caught in a rip current, remain calm to conserve energy and think clearly.
- Don't fight the current. Swim out of the current in a direction following the shoreline. When out of the current, swim towards shore.
- If you are unable to swim out of the rip current, float or calmly tread water. When out of the current, swim towards shore.
- If you are still unable to reach shore, draw attention to yourself: face the shore, wave your arms, and yell for help.
- If you see someone in trouble, get help from a lifeguard. If a lifeguard is not available, have someone call 9-1-1 . Throw the rip current victim something that floats and yell instructions on how to escape. Remember, many people drown while trying to save someone else from a rip current.