How much do I weigh in the Solar System? (346 kB Excel Spreadsheet)

People often get confused between these two things.   If you only deal with things on Earth, it usually doesn't matter, but once you go elsewhere in the universe, mass stays the same whist weight does not.   So we thought it worth putting up a page on the topic.

Scientists use the term ‘mass’ rather than weight when they are describing how much ‘stuff’ or matter they are talking about.   They use the term ‘weight’ to describe the force of an object in a gravity field. 

Mass is measured in kilograms.   (1000 kg = 1 tonne)

Force, and therefore weight, is measured in newtons. The unit is named after Isaac Newton, the famous seventeenth century scientist who first explained gravity.   Newton said his thoughts were set in motion after he saw an apple fall off a tree.  In the Earth’s gravity field, 1kg has a weight of 10 newtons (9.81 to be more precise).   Appropriately, 1 Newton is about the weight of a medium sized apple.

The force of gravity on the Moon is only one sixth of what it is on the Earth.  On Earth, a bag of six apples would have a mass of 0.6kg and would weigh 6 newtons. 

On the Moon, the bag of six apples would still have a mass of 0.6kg but they would only weigh 1 newton.

The difference between mass and weight is very important to space engineers and  scientists.   The space suit of this astronaut weighs about twice his body weight so on Earth he would weigh a total of three times his body weight.   He would be unable to move.   On the Moon, he weighs a sixth of that i.e. only half his body weight on Earth.  Astronauts found that they could even bounce up and down like a kangaroo as they hopped over the lunar surface.   On the other hand their mass was three times what they were used to and, with less weight, there was less friction between their boots and the ground.   They found it very difficult to stop!