Spacetime Sheet
by ArcadeLabA playful model of how gravity works in Einstein's general relativity. A heavy mass sits in the middle of a stretchy grid and dents it into a deep well — the bigger the mass, the deeper the dip. Flick marbles across the sheet and watch them curve, loop into orbits, or spiral inward. Gravity here isn't a pull; it's marbles rolling along curved space. The classic rubber-sheet picture made interactive.
Frequently asked
What is the spacetime sheet model?
It is a way to picture gravity. Imagine space as a stretchy sheet. A heavy object like a star dents the sheet, and anything moving nearby rolls along the curve. Planets orbit because they are following the bent shape of space around a star.
Why do the marbles orbit instead of falling straight in?
A marble with sideways speed keeps moving forward as it also rolls toward the dip. Those two motions combine into a curved path that loops around the mass — an orbit. Too slow and it spirals in; just right and it circles.
Does a bigger mass really bend space more?
Yes. In the simulation a bigger mass makes a deeper well, and in real space more massive objects curve spacetime more strongly. That stronger curve is why heavy stars hold planets in tighter, faster orbits.