Why don't eclipses happen every month, even though we have a new moon and full moon every month?
AThe Moon is sometimes too far away
BThe Moon's orbit is tilted about 5 degrees relative to Earth's orbit, so the Sun, Moon, and Earth usually do not line up precisely enough
CEclipses are too rare and random to follow a pattern
DEarth's atmosphere blocks most eclipses from being visible
The Moon's orbit around Earth is tilted about 5 degrees relative to Earth's orbit around the Sun. This means that most of the time, the Moon passes slightly above or below the Sun-Earth line. Eclipses only happen when the Moon crosses this plane (at points called nodes) at the same time it is in the new moon or full moon phase — which occurs only 2 to 5 times per year.
Question 2 Short Answer
During a total lunar eclipse, the Moon often appears reddish rather than disappearing completely. Why?
Think about your answer, then reveal below.
Model answer: Even when Earth blocks direct sunlight from reaching the Moon, some sunlight bends (refracts) through Earth's atmosphere. The atmosphere filters out blue light (scattering it away, which is why our sky is blue) and lets red light pass through. This red-filtered sunlight reaches the Moon and illuminates it with a dim reddish glow — the same physics that makes sunsets red.
If Earth had no atmosphere, the Moon would disappear completely during a total lunar eclipse — it would be totally dark. The red color is essentially the light from every sunrise and sunset on Earth simultaneously projected onto the Moon.
Question 3 True / False
A solar eclipse occurs during a full moon phase.
TTrue
FFalse
Answer: False
A solar eclipse occurs during a new moon, when the Moon is between the Sun and Earth. During a full moon, Earth is between the Sun and Moon — that is the geometry for a lunar eclipse. Remembering which is which: solar eclipse = new moon (Moon blocks Sun), lunar eclipse = full moon (Earth's shadow falls on Moon).