Lesson 6 of 19
Why it is not every month
Show on a big screenNew Moon comes every month. So why is there no eclipse every month?
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The idea
Step 1 of 4
- Earth's path round the Sun.
- The Moon's path, tilted a little against it.
- Most months the Moon sits above or below the line.
- So the shadow misses Earth and goes into empty space.
The rule
Tilt is measured in degrees, written °.
The Moon's path is tilted about 5°. At most New Moons, its shadow misses Earth.
The Moon's path crosses Earth's path at two points. Twice a year the Sun lines up with them. Those times are called eclipse seasons. A New Moon then can cast its shadow on Earth.
The same tilt explains why lunar eclipses are not monthly.
Try the lab to finish this lesson.