Weight and Mass

Centre of Mass

Earth and Moon taken by
the Galileo Spacecraft
Credit: NASA

The mass of an object tells us the amount of ‘stuff’ or matter it is made of. An object’s mass remains the same wherever the object is. 


Mass and Weight

Weighing the Earth?

The mass of an object tells us the amount of ‘stuff’ or matter it is made of. An object’s mass remains the same wherever the object is. Mass is measured in kilograms (kg). Or grams for small objects, and tonnes for larger objects.