People first walked on the moon on July 20, 1969. When Buzz Aldrin and Neil Armstrong stepped out onto the surface of the moon that day, they not only made world history — they lost weight.

How is this possible? Let’s find out.

Before we can understand weight, we must first understand gravity and mass. Gravity is a natural force that attracts objects to each other.

On Earth, gravity is the constant force pulling us toward Earth and preventing us from flying off into space like a balloon. When you step on a scale, it shows your weight as a number. This number is actually a measurement of the gravitational pull Earth has on you.

Mass is how much “stuff” you are made of. Unlike weight, your mass is the same whether you are on Earth, on Mars, on the moon, sitting in your living room, swimming in the ocean or floating somewhere in outer space.

Someone who weighs 200 pounds has more mass than someone who weighs 100 pounds. The more mass a person has, the greater the pull of gravity on them. This is why a scale shows a higher number for a larger person.

Small celestial bodies have weaker gravitational pulls than Earth. Larger planets, such as Jupiter and Saturn, have stronger gravitational pulls, which means you’d weigh more if you visited those planets.

Since the moon is smaller than Earth, it has a weaker gravitational pull. In fact, the moon only has 1/6 the gravity that Earth does. This means you weigh six times less on the moon than you do on Earth!

When the astronauts landed on the moon in 1969, they wore space suits and carried heavy packs of equipment. Since gravity is much weaker on the moon, everything weighed only 1/6 of its Earth-weight, and the astronauts were able to move around the moon very easily.