Academic journal article The Science Teacher

Try This Top Idea!

Academic journal article The Science Teacher

Try This Top Idea!

Article excerpt

moon on a stick

...adapted from EARTH, MOON & SUN #40

by TOPS Learning Systems

1. Locate the moon in the daytime sky.

FIRST QUARTER: Look east in the afternoon.

THIRD QUARTER: Look west in the morning.

2. Tape a small ball onto a straw, and hold it in sunlight, next to the real moon.

3. Observe: sunlight and shadow create the same phase on both "moons."

4. Why doesn't the moon look round?

5. What fraction of the whole moon is lit by the sun?

OBJECTIVE

To understand why our always-round moon doesn't usually look round!

LAB NOTES

Step 1. A waxing first-quarter moon rises in the east at noon and culminates (overhead or southward in the northern hemisphere) at sunset. A waning third-quarter moon culminates at sunrise and sets in the west at noon. These are fine opportunities for viewing both sun and moon together, and understanding moon phases. Steps 2-3. Folks often think we are seeing Earth's shadow "shaping" the moon. Not so. Both the real and model moon, lit by the sun from the same direction, create their own similar shadows. (Earth's shadow crosses the moon only during a lunar eclipse.)

ANSWERS

4. Only the lighted part of the moon is reflecting sunlight. Its shadowed side is not reflecting enough light to be clearly seen from Earth (unlike the ball). …

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