Two identical balls fall from the same height. Which reaches the ground first?
Press Start test to see the difference.
🏀 Planetary Basketball Challenge
Can you make the same shot on two different planets? Set your shot strength and launch angle, then watch the identical basketballs fly. The hoops are the same distance away and the same height. No wind or air resistance.
Adjust the controls, then shoot!
Adjust the controls, then shoot!
Tip: A weaker gravitational pull usually means the ball travels higher and farther with the same shot.
🧲 What Is Gravity?
Gravity is an attractive force between objects that have mass. Earth's gravity pulls you, a basketball, and everything else toward Earth's center. That's why a dropped ball falls and why you come back down after jumping.
Every planet pulls on objects, but not equally strongly. A planet's mass and the distance from its center both matter.
Scientists can compare planetary gravity with Earth's. If another world has 109% of Earth's gravity, its pull is 9% stronger at the reference level. A 100-pound Earth weight would correspond to about 109 pounds there.
If gravity is 38% of Earth's, the same object weighs only 38% as much and falls more slowly in our no-air-resistance experiment.
Mass is how much matter an object contains. Your mass does not change when you travel to another planet.
Weight is the force of gravity pulling on your mass. Your weight changes from planet to planet. Here, “pounds” means familiar Earth-weight equivalents, not changes to body mass.
Mercury, Venus, Earth, and Mars have solid surfaces. Jupiter, Saturn, Uranus, and Neptune do not have solid surfaces to stand on.
Our astronauts and basketball hoops stand on imaginary hovering platforms near those planets' atmospheric reference levels. This lets us compare gravity only; their real pressure, temperature, and weather would make these scenes unsafe.
Compare the planets
| Planet | Earth's gravity | What it means for a 100 lb Earth weight |
|---|---|---|
| Mercury | 37.8% | 37.8 lb equivalent |
| Venus | 90.7% | 90.7 lb equivalent |
| Earth | 100% | 100 lb |
| Mars | 37.7% | 37.7 lb equivalent |
| Jupiter | 236% | 236 lb equivalent |
| Saturn | 91.6% | 91.6 lb equivalent |
| Uranus | 88.9% | 88.9 lb equivalent |
| Neptune | 112% | 112 lb equivalent |
Try these investigations
Predict: On which planet will the same basketball travel the farthest? Test: Keep the same power and angle while switching planets. Explain: How did the changing gravity affect the path? Can you adjust power and angle to score on Jupiter?
Which planet makes the same object fall faster?
Teacher notes and science behind the model
Drop tests assume the same release height and ignore air resistance. Jump tests assume the same launch speed (a simplified controlled comparison), so lower gravitational acceleration produces a higher, longer jump. These are idealized physics demonstrations: they do not simulate drag, pressure, temperature, health effects, or what would actually happen to a human astronaut.
Jupiter, Saturn, Uranus, and Neptune have no solid walkable surface. Their platform is imaginary, hovering at a standard atmospheric reference level. Gravity ratios are approximately based on NASA's planetary fact sheet, which uses reference levels rather than literal surfaces for giant planets.
Mass stays constant when you change planets. The weight comparison shows gravitational force expressed as an Earth-weight equivalent; it is not a change in body mass.