How far away
is the Moon?
On average 384,400 km — but the orbit is elliptical, so it ranges from about 356,000 to 406,000 km. We know the distance to within millimetres by bouncing lasers off reflectors left by Apollo.
On average, 384,400 kilometres — about thirty Earths lined up side by side. Light, the fastest thing there is, needs 1.3 seconds to make the trip.
But the Moon’s orbit is an ellipse, not a circle, so the true distance swings between roughly 356,000 km at perigee (closest) and 406,000 km at apogee (farthest) each month. That 14% difference is why some full moons — supermoons — look noticeably larger and brighter than others.
How do we know so precisely? The Apollo 11, 14 and 15 crews left retroreflectors on the surface — arrays of corner-cube prisms that bounce light straight back where it came from. Observatories still fire laser pulses at them today and time the echo: about 2.6 seconds there and back. Half the round-trip time multiplied by the speed of light gives the distance to within a few millimetres.
Those measurements revealed something else: the Moon is drifting away from Earth by about 3.8 centimetres a year — roughly the rate your fingernails grow — as it slowly steals rotational energy from Earth through the tides.
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.
Try the interactive lesson — freeDates 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.