Everyone knows that the Moon goes through phases, but let’s talk about why it does. It comes down to illumination, which in this case, all originates from our nearby star.
Our Moon orbits around our planet, and this Earth-Moon system orbits around the Sun.
Even though we only see light on part of the Moon, from the perspective of the Sun, half of it is always illuminated.
Stuck here on Earth, we see the Moon in various phases of illumination as it completes a 27.3 day orbit around the Earth.
As The Moon travels around us we see it pass through its phases. It goes from New Moon, to Full Moon and back to new Moon again.
Crescent Moons are when it’s less than half illuminated, and gibbous when it’s more than half.
“Waxing” means that the Moon becomes more illuminated night-by-night, and the term “waning” means that it’s getting less illuminated each night.
If you ever get the chance to travel to the other hemisphere, you’ll immediately notice how unfamiliar the Moon behaves – it’s upside down.
If you live in the Northern Hemisphere, after a New Moon the crescent begins on the right-side. But if you’re in the Southern Hemisphere, it’s reversed, with the illumination starting on the left side.
The alignment of the Sun, Earth and Moon can lead to some fantastic astronomical events.One event occurs when the Moon is full, and it passes through the Earth’s shadow. Or as you probably know it, a lunar eclipse. This causes the Moon to grow dark and then turn an eerie red color.
When the Moon is new, it can pass in between the Earth and the Sun, casting its shadow down on our planet. As you know, a solar eclipse.You’d think we would see a solar and lunar eclipse every month, but we don’t because the Moon’s orbit is inclined relative to the Sun.
Most months, the Moon is either above or below the Sun in the sky, so they just don’t line up perfectly.One more thing, you might not know that Venus also goes through phases. When the planet is on the other side of the Sun from us, we see it as a nearly complete disk. But when Venus is on our side, just about to pass into the glow of the Sun, it’s a thin crescent, just like how we see the Moon.
I hope this gives you a better understanding of why the Moon goes through its phases every month, and the interesting relationship between the Earth, the Sun, and the Moon.