What is 27.3 days?

27.3 days is how long it takes for our Moon to go all the way around Earth.

Imagine you and your friend are dancing in a big room. You're holding hands, and you both move around each other, that's like the Moon going around Earth. Now, if your dance took 27.3 days to complete one full circle, that would be pretty slow! That’s exactly what happens with our Moon.

Every night, you can see the Moon changing shape, from a thin sliver to a big round full moon and back again. This is called the lunar cycle, and it takes about 29.5 days to complete. But that's not quite the same as how long it takes for the Moon to make one full trip around Earth.

Why the difference? Because while the Moon orbits Earth, Earth is also moving around the Sun, like you're both spinning in a slow, waltz-like dance instead of just turning in place. So even though the Moon completes its orbit in 27.3 days, it takes a little longer for us to see all the changes from our viewpoint on Earth.