1. The Sun's Light: The Sun illuminates the Moon, just like it illuminates Earth.
2. The Moon's Orbit: The Moon orbits Earth in about 27.3 days.
3. The Changing Angle: As the Moon orbits Earth, the angle at which the sunlight hits its surface changes.
Here's how it works:
* New Moon: The Moon is between the Sun and Earth, with its unlit side facing us. We can't see it.
* Waxing Crescent: A sliver of the Moon's illuminated side becomes visible, growing larger each day.
* First Quarter: Half of the Moon is illuminated, appearing as a half-circle.
* Waxing Gibbous: More than half of the Moon is illuminated, growing larger each day.
* Full Moon: The entire face of the Moon is illuminated, facing Earth.
* Waning Gibbous: The illuminated portion of the Moon begins to shrink.
* Last Quarter: Again, half the Moon is illuminated, appearing as a half-circle.
* Waning Crescent: The illuminated portion shrinks further, becoming a sliver until it disappears completely, returning to the New Moon phase.
Think of it like this: Imagine holding a flashlight and shining it on a basketball. As you move the basketball around, the amount of light hitting its surface changes. The Moon is like the basketball, and the Sun is like the flashlight.
The cycle of lunar phases repeats roughly every 29.5 days. This is why we see the Moon change shape over time.
