Home > Science & Mathematics > Astronomy & Space > Why would you weigh less on the moon compared to earth?

Why would you weigh less on the moon compared to earth?

  • Best Answer
    Because weight depends on gravity. And gravity is caused by mass. The Moon is smaller than the Earth, so it has less mass, so its gravitational pull is smaller, so you don't get pulled down to the ground so hard and you'll see that if you try to weigh yourself there. What scales actually measure is the pressure you put on them.

    Out in space, there's no gravity pulling you in any direction so your weight is nothing. On the International Space Station, where there's effectively no gravity because it's in a free-fall orbit, astronauts need to weigh themselves so the doctors can keep a check on their health, but normal scales don't work because you'd just float off them. The Russians have invented a gadget to do it that astronauts have to bounce up and down on, and it measures resistance to the springs in it. They call it "riding the donkey"!

    It's important to make the difference between mass and weight. Your weight is entirely a function of what gravity is pulling on you, but mass never changes - it's a measure of the amount of "stuff" in you. While we're on Earth, it's not important to know the difference because we're in the same gravity all the time and we say we have a weight in kg. It works for everyday life. But really, as a physicist will tell you, kg measures mass, and weight is in newtons. Newtons are a unit of force and that's the point - your weight is the force you press down on the ground with. And you only press down on the ground with a force because gravity pulls you down.

    Let's imagine we're both astronauts on the ISS. We both weigh nothing and float around. But if I bump into you, you'd know I still have mass! To be absolutely correct, "the donkey" doesn't measure weight because you don't have any, it measures mass. Boing, boing, boing...
    Clive · 0 0
  • Other Answer
  • my dork
    larry · 0 0
  • You have mass and weight. There is a definition of mass which is basically the force required to move you if stationary or to alter your velocity if moving. Basically, it depends on the amount of you. It is correctly measured with the kilogram (kg) and remains the same wherever in the universe you are.

    Weight is determined by the acceleration due to the force of gravity acting on your mass and is correctly measure with the newton (N). On Earth, gravity varies but it is very roughly 10 metres per second squared (m/s^2). Let's say you are Mr average male and you have a mass of 70 kg. Your mass is the same on Earth, on the Moon or in deep space. On Earth your weight is your mass multiplied by the acceleration due to the force of gravity acting on your mass, i.e. 70 x 10 = 700 N.

    On the Moon the acceleration due to the force of gravity is about one-sixth of what it is on Earth. Therefore, on the Moon your weight will be less. If your weight on Earth is 700 N, on the Moon it would be ca. 117 N.
    MARK · 0 0
  • The Moon is much smaller than Earth and has a smaller mass than that of Earth. That exact number is .012 th the mass of Earth. So the smaller mass of the Moon does not pull (gravity) as much as that of the larger massed Earth. The Moon's surface gravity .156 that of Earth. 1/6 = 0.1666

    Now if you were on Jupiter with a mass of 317.8 times that of Earth you would experience a weight (at cloud tops) of 2.64 times that of your weight on Earth.

    However you 'mass' would remain the same regardless of where you went in the Universe.
    Fred · 2 0
  • Gravity
    Slim shady · 3 1
Amazon Ads