Weighta

Meet Weighta, an astronaut standing on a scale on the Moon.

Mass and weight are often mixed up, but they are different quantities. Mass, measured in kilograms, is how much matter you contain and how hard you are to accelerate; it is the same everywhere. Weight is the gravitational force on that mass, W = mg, measured in newtons, and it depends on the local gravitational field strength g.

A 60 kg astronaut on Earth, where g ≈ 9.81 m/s², weighs 60 × 9.81 ≈ 589 N. On the Moon, where g ≈ 1.62 m/s², the weight is 60 × 1.62 ≈ 97 N, about one sixth. The mass is 60 kg in both places.

That is why astronauts could bound across the Moon in heavy suits, and why engineers designing rovers and landers must know the weight they will have on each world. Bathroom scales measure force but display it as mass, assuming Earth's g.

Even on Earth, g varies a little, from about 9.78 m/s² at the equator to 9.83 m/s² at the poles, so your weight changes slightly while your mass does not.