Mass versus Weight

It is easy to think of weight and mass as the same thing. That is because on Earth, both terms seem to imply the same concept; however, in space the concepts of mass and weight are very different. No matter where you are in the universe, your mass is always the same: mass is a measure of the amount of matter which makes up an object. Weight, however, changes because it is a measure of the force between an object and body on which an object resides (whether that body is the Earth, the Moon, Mars, et cetera). When we talk about weight on Earth, we are really speaking about how much force the Earth is currently exerting on us through gravity.

This is what differentiates mass from weight: we will have the same mass anywhere in the universe regardless of what bodies we are near. However, our weight changes depending on how strong the local force of gravity is.