The Orbital Tilt
Learn why lunar eclipses are rare: the Moon's orbit is tilted relative to Earth's path around the Sun, so during most Full Moons the Moon passes above or below Earth's shadow.
Key Concepts
The Moon's orbit around Earth is tilted relative to Earth's orbit around the Sun. They do not sit on the same flat plane.
This tilt means that during most Full Moons, the Moon is physically located slightly above or below Earth's shadow. Sunlight passes Earth and still hits the Moon.
Common Questions
Why doesn't a lunar eclipse happen every Full Moon?
The Moon's orbit is tilted about 5 degrees relative to Earth's orbit. During most Full Moons, the Moon sits slightly above or below Earth's shadow, so sunlight still reaches it and no eclipse occurs.
What does orbital tilt mean in Grade 8 science?
Orbital tilt describes the angle between two orbital planes. Grade 8 students learn that the Moon's tilted orbit explains why lunar eclipses only occur a few times per year rather than monthly.
How does the Moon's orbital tilt prevent eclipses?
Because the Moon orbits on a different plane, it usually misses Earth's shadow. A lunar eclipse only occurs when the Moon crosses Earth's orbital plane exactly at Full Moon.