Key Idea.
Section 1
The Terminator Line
The terminator is the visible line that separates the illuminated day side from the dark night side.
To an observer standing on this line on the Moon, the Sun would appear to be rising or setting. It marks the physical point where the curvature of the Moon blocks the Sun's straight rays.
Section 2
Darkness is Self-Shadow
A common misconception is that the dark part of the Moon is caused by Earth's shadow. This is incorrect (except during an eclipse).
Under normal conditions, the dark portion we see is the Moon's own shadow. It is simply the side of the sphere turned away from the Sun.
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Section 1
The Terminator Line
The terminator is the visible line that separates the illuminated day side from the dark night side.
To an observer standing on this line on the Moon, the Sun would appear to be rising or setting. It marks the physical point where the curvature of the Moon blocks the Sun's straight rays.
Section 2
Darkness is Self-Shadow
A common misconception is that the dark part of the Moon is caused by Earth's shadow. This is incorrect (except during an eclipse).
Under normal conditions, the dark portion we see is the Moon's own shadow. It is simply the side of the sphere turned away from the Sun.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter