Explain why weight and mass are used as synonyms on earth, but are different for an astronaut traveling to the moon. Explain why it would be used as a synonym by someone who grew up on the moon their whole life?

In scientific circles, Mass and weight are ACTUALLY NOT synonymous, and it is a misconception if people use them like that. Mass is a measure of the amount of matter, and measured in kilograms. Weight on the hand, is the amount of force exerted by the Earths gravity on an object of finite mass.

If a body has a mass of ##m## kilograms, then its weight ##W## is given by

##W = m*g## , where ##g## is the gravitational constant, ##9.81 ms^-2## .

Usually ##g## is taken as ##10 ms^-2## and is fairly constant on Earth, hence the word weight is used to refer to your mass, however in scientific terms, that would be incorrect. Weight is NOT equivalent to mass.

For an astronaut on the moon, his mass will remain the same, and equal to his mass on Earth, however, his weight on the moon is different since the pull of the moon on his mass is less because the moon has a lower mass. His weight on the moon is still given by the same formula, but with ##g## representing the moons gravitational pull.