Moon Phases
Why the Moon changes shape on a 29.5 day cycle, and why eclipses are rare.
Playback
Orbit tiltThe Moon's real orbit is tilted about 5 degrees. Turn the tilt off to see what a flat orbit would do.
Drag the Moon around its orbit, or press Play and watch a month pass.
A model of the Earth-sun-moon system, viewed from above the North Pole. Sizes and distances are not to scale; orbit tilt exaggerated for visibility.
New Moon
Phase tonight
DAY 0 OF 29.5
In this cycle
ORBIT TILT 5 DEGREES
Orbit shape