Physics - What Is The Difference Between Mass and Weight?

Mass is how much stuff is inside something, and weight is how hard gravity pulls on that stuff.

Imagine you're holding a bag of marbles. The more marbles you put in, the heavier it feels, that’s because its mass increased, and so did its weight.

Now think about when you go to the moon. You still have the same number of marbles (so your mass stays the same), but you feel lighter because gravity on the moon is weaker, that means your weight is less.

• If you use a scale, it shows your weight, how much gravity is pulling on you.
• If you count marbles in a bag, you're measuring mass, how much stuff is inside.

So when you go to space and feel weightless, it’s not because you’ve lost mass, but because there’s less gravity pulling on your mass.