The moon doesn't actually change shape. Ciò che vediamo come le diverse "forme" della luna (le fasi lunari) sono effettivamente causate dai mutevoli angoli della luce solare che riflettono dalla superficie della luna mentre orbita in orbita la terra.

Ecco una rottura:

* The moon always has the same shape: È una sfera.

* Sunlight illuminates the moon: Just like the Earth, the moon is illuminated by the sun.

* The moon orbits the Earth: As the moon orbits, the angle at which sunlight hits it changes.

* We see different amounts of the illuminated side: This is what we perceive as the lunar phases, from a sliver of light (new moon) to a full circle (full moon).

Think of it like holding a ball in front of a lamp. As you rotate the ball, different parts of the ball are illuminated.