Question: Why do we see phases of the Moon?

Student Exploration: Phases of the Moon                                        

Vocabulary: axis, crescent, First Quarter, Full Moon, gibbous, illuminate, Moon phase, New Moon, orbit, revolve, rotate, Third Quarter, waning, waxing

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

Gizmo Warm-up

The path that the Moon takes is called its orbit. The Moon is revolving around Earth.

This motion is called rotation. Earth rotates on its axis, a straight line connecting the North Pole to the South Pole.

Activity A: Moon phases

Get the Gizmo ready: Click Reset ().

Question: Why do we see phases of the Moon?

Why do you think we see phases of the Moon?

How does the Moon’s appearance change as the Moon revolves around Earth?

Based on your observations, why do we see Moon phases? 

Activity B: Name that phase!

Get the Gizmo ready:

Goals: Learn the names of Moon phases and when they occur.

Click Play. When you are ready to fill in part of the diagram, click Pause (). Sketch what the Moon looks like and write the phase name and day next to your sketch. (The first two are done for you.) Click Play to continue.

Suppose you saw a waxing gibbous Moon. What phase would you expect one week later?         Test your prediction using the Gizmo.

Waxing means “growing” and waning means “shrinking.”

Extension: The Man in the Moon

Get the Gizmo ready:

Question: If you look closely at the Full Moon, you may notice dark areas that look a bit like a face. This is known as “The Man in the Moon.” Does this side of the Moon always face Earth?

Do you think we always see the same side of the Moon?

Click Play. The flag helps you notice how quickly the Moon is rotating. Click Pause when the flag has rotated in a full circle, showing that the Moon has rotated once.

Where does the flag point as the Moon revolves around Earth?.

Do we always see the same side of the Moon? How do you know?

What do you notice about these two time intervals?

Suppose the Moon rotated on its axis just as quickly as Earth. Would we still always see the same side of the Moon from Earth? Explain.