Why doesn’t the Moon
fall down?

It is falling — continuously, toward Earth. But it also moves sideways at about 1 km/s, so it keeps missing. That endless falling-and-missing is what an orbit is.

The honest answer is that the Moon is falling. It has been falling toward Earth for four and a half billion years. It just keeps missing.

Newton explained it with a thought experiment. Fire a cannonball horizontally and it falls to the ground some distance away. Fire it faster and it lands farther. Fire it fast enough and something remarkable happens: the ground curves away beneath it exactly as fast as the ball falls toward it. The ball is still falling — it just never lands. That is an orbit.

The Moon moves sideways at about 1 kilometre per second. In the same second, Earth’s gravity pulls it about 1.4 millimetres off its straight-line path. Those 1.4 millimetres per second, applied forever, bend the Moon’s path into a closed loop around Earth. Take away gravity and the Moon would sail off in a straight line; take away its sideways speed and it would drop on us. Orbit is the balance of the two.

This is also why astronauts float. They aren’t beyond gravity — at the International Space Station’s altitude, gravity is still 90% as strong as on the ground. They float because they are falling around Earth together with their spacecraft, endlessly missing, just like the Moon.

This is one of seven interactive lessons in Moon Academy inside the Moon Explorer app — there, you don’t read the answer, you drag the Moon around its orbit and watch it happen.

← All seven questions

Dates and times are in Universal Time (UT). The free Moon Explorer app for Android converts everything to your local time and your exact location — fully offline, with no ads or accounts.