Answer
A lunar eclipse occurs when the Earth, sun, and moon are in a straight line, with the Earth between the other two. Just prior to that, observers on Earth see a full moon. This is shown in Figures 26.14a and 26.14b.
At the time of a crescent or half-moon, the Earth, moon, and sun are not aligned and no eclipses are possible.
Work Step by Step
This is discussed on page 495.
