Your Weight on Other Worlds
Would you weigh less on the Moon? Step on a scale and jump on the Moon, Mars, Jupiter, Pluto and even the Sun, side by side with Earth.
Class 9 GravitationSame leg push on both worlds: a 50 cm jump on Earth.
Try this
0 of 5 doneJump higher than 3 metres.Hint: try a world with weak gravity, then press Jump
Make the scale show more than twice your Earth weight.Hint: the biggest planet
Visit three worlds. Does your mass ever change?Hint: watch the mass readout as you switch worlds
Weigh less than a tenth of what you weigh on Earth.Hint: a small, faraway world
Find where you'd weigh the most of all.Hint: it isn't a planet
What's happening
Mass stays, weight changes
Mass is how much stuff you're made of, measured in kilograms. It's the same on Earth, the Moon or anywhere. Weight is the force of gravity pulling on that mass, measured in newtons. Weaker gravity means less weight, even though you haven't changed at all.
Why gravity differs
A world's surface gravity depends on its mass and its size. More mass pulls harder; a bigger radius puts you farther from the centre, which weakens the pull. The Moon has only about 1/6 of Earth's gravity; Jupiter has about 2.5 times.
Jumping on other worlds
Your legs push off at the same speed everywhere. With weaker gravity, nothing slows you down as fast, so you rise higher and stay up longer. On the Moon, a 50 cm Earth jump becomes about 3 metres; on Pluto almost 8 metres.
Who figured this out?
Isaac Newton
1687, EnglandExplained that the same gravity that makes an apple fall keeps the Moon in orbit, and that its pull depends on mass and distance.
Henry Cavendish
1798, EnglandMeasured the tiny pull between lead balls in his lab. From it he worked out Earth's mass, an experiment often called 'weighing the Earth'.
Apollo 15
1971, on the MoonAstronaut David Scott dropped a hammer and a feather together on the Moon. With no air to slow the feather, they hit the ground at the same moment.
Learn more
- Surface gravity · Wikipedia
- Mass versus weight · Wikipedia
Check yourself
1. An astronaut has a mass of 60 kg on Earth. What is her mass on the Moon?
2. The Moon's gravity is about 1/6 of Earth's. A person who weighs 600 N on Earth weighs about…
3. On which planet would you weigh the most?
4. What unit is weight measured in?
Common questions
What is the difference between mass and weight?
Mass is the amount of matter in an object, measured in kilograms; it is the same everywhere. Weight is the force with which gravity pulls on that mass, measured in newtons: W = m × g. Your mass is the same on the Moon, but your weight there is about one-sixth of your weight on Earth.
How do you calculate your weight on another planet?
Multiply your mass by that planet's surface gravity: W = m × g. For example, a 40 kg child on Mars (g ≈ 3.71 m/s²) weighs 40 × 3.71 ≈ 148 N, compared with about 392 N on Earth. A bathroom scale made for Earth would show about 15 kg.
What is the acceleration due to gravity on the Moon?
About 1.62 m/s², roughly one-sixth of Earth's 9.8 m/s². That's why astronauts on the Moon could bounce along and objects fall more slowly there.
What is the value of g on different planets?
Approximate surface gravity in m/s²: Mercury 3.7, Venus 8.9, Earth 9.8, Mars 3.7, Jupiter 24.8, Saturn 10.4, Uranus 8.7, Neptune 11.2. The Moon has 1.6 and Pluto 0.6. For the giant planets, the value is at the level of their cloud tops.
Why does the value of g change from planet to planet?
Surface gravity depends on the planet's mass and radius: g = GM/R². A more massive planet pulls harder, but a larger radius puts you farther from its centre, which weakens the pull. Saturn is 95 times heavier than Earth, but so wide that its surface gravity is only a little more than Earth's.
Why do astronauts feel weightless in space?
Not because there is no gravity. In orbit, astronauts and their spacecraft are falling around Earth together, so nothing pushes up on them and they float. On the Moon's surface they do feel weight, about one-sixth of what they feel on Earth.
Surface gravity values are standard figures; for the giant planets and the Sun they're at the visible surface, where there's nothing solid to stand on.
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