It is accurate and rapid to measure the distance with laser. A laser signal is sent from the earth to the moon, and the signal reflected from the moon surface is received in about 2.56 seconds

It is accurate and rapid to measure the distance with laser. A laser signal is sent from the earth to the moon, and the signal reflected from the moon surface is received in about 2.56 seconds

The speed of light is 300000 km / s, so the distance of this laser signal is 30 * 2.56 = 768000 km, so the distance between the earth and the moon is 768000 km △ 2 = 384000 km