Newton
Every mass attracts every other mass. The force grows with both masses and falls with the square of distance. This model accurately handles falling objects, moons, planets, and the calculations above.
Force meets spacetime
Change a world. See what gravity does.
Newton gives us the numbers. Einstein gives us the deeper picture. Use both to trace a fall, an orbit, and an escape from the same mass.
One world.
Four consequences.
Choose a known body or enter your own. Every result is derived locally from the values you provide.
Build your world
Earth results
Surface gravity9.820 m/s²
Your weight687.4 N
Escape velocity11.186 km/s
Orbital speed7.672 km/s
Worked equations
g = GM / R²(6.67430e-11 x 5.972e24) / 6,371,000²W = mg70 x 9.820vₑ = √(2GM / R)Escape from the surfacevₒ = √(GM / (R + h))Circular orbit 400 km above surfaceAt 400 km, a circular orbit moves sideways at 7.672 km/s while continuously falling around Earth.
Two models.
One observable world.
Newton and Einstein are not rival buttons. They answer at different depths and agree extraordinarily well in ordinary weak gravity.
Orbit
An orbit is continuous free fall with enough sideways motion to keep missing the surface. Newton's equations predict the speed; the path reveals that falling and orbiting are one family of motion.
Einstein
Mass-energy curves spacetime. Freely falling objects follow the straightest available paths through that geometry, called geodesics. General relativity becomes essential for strong gravity and precision effects.
The explanation gets deeper, not discarded.
Scroll the same event through three levels of description.
The apple accelerates.
Near Earth's surface, the lab calculates an acceleration of about 9.82 m/s². Newton's law turns Earth's mass and radius into that reliable prediction.
The satellite keeps falling.
At 400 km altitude, about 7.67 km/s of sideways speed bends the fall into an orbit. The force model remains a superb working tool.
Spacetime shapes the path.
Einstein reframes the cause: Earth changes the geometry around it, and free objects follow geodesics. The numbers above are the weak-field limit of that deeper theory.
Keep the numbers. Carry the idea.
Export the current world, all four calculations, and the Newton-to-Einstein interpretation as a study-ready text brief.