Your mass is the same everywhere in the universe, but your weight is not — it is W = m × g, and every world pulls with a different gravity. Set a mass, tap a planet, and watch the same person's scale reading leap from world to world in real time.
Two controls drive the whole simulator. The mass slider sets how much matter the astronaut is made of, and the planet buttons — Moon, Mars, Earth and Jupiter — swap in each world's surface gravity. Tap a button and the little planet in the corner changes, the needle swings to a new reading, and the gold weight arrow grows or shrinks. There is also a manual gravity slider, so you can dial in any world you like, from a tiny asteroid to a crushing super-Earth.
Keep your eye on the mass slider while you jump between planets: it never moves. That is the single idea the lab is built to show — only your weight changes, never your mass. On the Moon the scale reads about a sixth of its Earth value; on Jupiter about two and a half times more; yet the kilograms of matter making up the astronaut are identical in every case. Mass is what you are, weight is how hard a world pulls on it.
Behind the readouts the sim is simply solving W = mass × surface gravity, then converting that force into the kilograms an ordinary bathroom scale would display by dividing by Earth's gravity. The “times Earth” figure is just the ratio of the two gravities, so it reads exactly 1.00 on the Earth preset and tells you at a glance how many times heavier or lighter you would feel elsewhere.
The lab also quietly corrects a popular myth: that a bigger planet always means more weight. Nudge the gravity slider to Saturn's value, around 10.4, and you will find the ringed giant — far larger than Earth — barely outweighs it, because surface gravity depends on radius as well as mass. For the full tour of how much you would weigh across the solar system, read the guide to weight on other planets. To put exact figures on any world, open the weight on other planets calculator, or explore another idea in the full simulation collection.
It multiplies your mass by the surface gravity of the world you pick: W = m times g. Mass stays in kilograms, gravity is in metres per second squared, and the result is a weight in newtons. The scale reading in kilograms is that weight divided by Earth's gravity, m times g divided by 9.81, which is what an ordinary bathroom scale would show.
Because mass is the amount of matter in you, and that does not depend on where you are. Moving to the Moon or Jupiter changes the gravitational pull on that matter, which changes your weight, but never the matter itself. That is why the mass slider stays put while the scale reading jumps — mass in, weight out.
It is the ratio of the chosen world's gravity to Earth's, g divided by 9.81. On Earth it reads 1.00; on the Moon about 0.17, so you weigh roughly a sixth as much; on Jupiter about 2.53, so you weigh about two and a half times more. Multiply your Earth weight by this number to get your weight on that world.
Jupiter is a giant ball of gas with no solid surface to stand on — the 24.79 m/s² figure is the gravity at its cloud tops. The preset is there to show how much heavier the same person would feel under that pull: on a Jupiter-strength world your scale reading would be about two and a half times your Earth value.
Of the presets, Jupiter gives by far the highest reading because it has the strongest surface gravity. A bigger planet does not automatically mean more weight, though — what matters is surface gravity, which depends on both mass and radius. Set the gravity slider by hand to compare worlds like Saturn or Uranus, which are huge yet pull only a little harder than Earth.