Learn on PengiAmplify Science (California) Grade 8Chapter 2: Moon Phases

Lesson 2: Explaining Moon Phases

Key Idea.

Section 1

Phases are Viewing Angles

Key Idea

Moon Phases are strictly a result of our changing perspective. A "phase" is simply a measure of how much of the Moon's illuminated half is visible from Earth.

  • Full Moon: We are in a position to see the entire illuminated half.
  • New Moon: We are facing the dark half.
  • Crescent/Quarter: We see a fraction of the lit side.

Section 2

Synchronized Rotation

Key Idea

As the Moon orbits Earth, it rotates on its axis at the exact same speed. This synchronization means the same side of the Moon always faces Earth.

We never see the "far side" of the Moon. All the phases we observe happen on the surface of the "near side" as the sunlight sweeps across it.

Lesson overview

Expand to review the lesson summary and core properties.

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Section 1

Phases are Viewing Angles

Key Idea

Moon Phases are strictly a result of our changing perspective. A "phase" is simply a measure of how much of the Moon's illuminated half is visible from Earth.

  • Full Moon: We are in a position to see the entire illuminated half.
  • New Moon: We are facing the dark half.
  • Crescent/Quarter: We see a fraction of the lit side.

Section 2

Synchronized Rotation

Key Idea

As the Moon orbits Earth, it rotates on its axis at the exact same speed. This synchronization means the same side of the Moon always faces Earth.

We never see the "far side" of the Moon. All the phases we observe happen on the surface of the "near side" as the sunlight sweeps across it.