Learn on PengiAmplify Science (California) Grade 8Chapter 1: Light and Dark on the Moon

Lesson 2: Light Sources and Illumination

Key Idea.

Section 1

The Moon Reflects, It Does Not Glow

Key Idea

In our solar system, the Sun is a light source because it generates its own visible energy. In contrast, the Moon is a non-luminous object made of gray rock.

The Moon is visible from Earth only because it acts like a mirror. Sunlight travels through space, strikes the surface of the Moon, and reflects toward our eyes. If the Sun were turned off, the Moon would instantly vanish from our view.

Section 2

The Half-Lit Principle (The Model)

Key Idea

Now we apply the "straight line" rule to the Moon. Since the Moon is a sphere and the Sun is a distant light source, the geometry forces a specific result: The Sun always illuminates exactly one half of the Moon.

There is always a "Day Side" facing the Sun and a "Night Side" facing away.

Lesson overview

Expand to review the lesson summary and core properties.

Expand

Section 1

The Moon Reflects, It Does Not Glow

Key Idea

In our solar system, the Sun is a light source because it generates its own visible energy. In contrast, the Moon is a non-luminous object made of gray rock.

The Moon is visible from Earth only because it acts like a mirror. Sunlight travels through space, strikes the surface of the Moon, and reflects toward our eyes. If the Sun were turned off, the Moon would instantly vanish from our view.

Section 2

The Half-Lit Principle (The Model)

Key Idea

Now we apply the "straight line" rule to the Moon. Since the Moon is a sphere and the Sun is a distant light source, the geometry forces a specific result: The Sun always illuminates exactly one half of the Moon.

There is always a "Day Side" facing the Sun and a "Night Side" facing away.