It sounds like this“If the Moon were really falling toward us, it would have crashed into Earth long ago.”
Thinking falling always means getting closer
Why it feels right
In daily life, falling and landing go together. Things fall straight down because they were dropped, not thrown, and they end up on the floor. The word 'falling' has landing built into it, so 'the Moon is falling' sounds like a promise of a crash. Add that the Moon looks utterly still against the sky, and it seems absurd to say it is falling at all.
Why it’s wrong
Falling means being pulled, not necessarily getting nearer. The Moon keeps moving sideways while it falls, so the fall bends its path into a curve. It drops about 1.4 mm toward Earth each second while moving about 1,020 metres sideways, and the two match: it falls constantly and keeps missing.
A worked example
Throw a ball hard and flat from a cliff. It follows a curve, landing further away than if you had dropped it. A second ball dropped at the same moment from the same height lands at the same time: sideways motion doesn't change how fast you fall. Both fall 4.9 metres in the first second; the thrown one just does it while travelling forward.
Now throw faster and faster. The ball lands further each time. Earth is a sphere, so eventually, at about 7.9 kilometres per second with no air, the ground curves away beneath the ball as fast as it drops. It still falls 4.9 metres each second, and the ground keeps dropping away by the same amount, so it never lands. That is an orbit.
The Moon is the same thing on a bigger scale. It moves about 1,020 metres sideways each second and falls about 1.4 millimetres toward Earth in that second, and its path curves away from a straight line by exactly that much. It has been falling and missing for billions of years.
How to catch yourself
- You think falling must end in landing.
- You say an orbiting object 'isn't falling' because it isn't getting closer.
- You picture the space station as hovering rather than falling.
What to hold instead
Falling means being pulled by gravity with nothing holding you up. If you also have enough sideways speed, the fall bends your path round the planet instead of down into it. An orbit is falling without ever landing, because the ground curves away as fast as you drop.
Where you’ll meet it
- Understanding why astronauts on the station are weightless.
- Seeing how satellites, from GPS to weather, stay up with no engines running.
- Reading Newton's cannonball thought experiment.
Questions people ask
- Is the Moon really falling toward the Earth?
- Yes, in the sense that Earth's gravity pulls it toward us every moment, bending its path. It falls about 1.4 millimetres each second, but it is also moving sideways at about a kilometre a second, so it keeps missing. That is what an orbit is.
- Why don't satellites fall down?
- They do fall, all the time. They are moving sideways so fast that Earth curves away beneath them as quickly as they drop, so they never land. At about 400 kilometres up that takes roughly 7.7 kilometres per second.