01
One body, not many
Real orbits are affected by every other mass nearby — the Moon, other planets, Jupiter's pull. This sandbox has just one central mass.
Solar system · Question
Why don't planets fall into the Sun?
They are falling — they're just moving sideways fast enough to keep missing. This is the same thought experiment Isaac Newton used: fire a cannonball from a very tall mountain and see what happens at different speeds.
Visual model
Launch the cannonball.
At 2.6 model speed, a circular reference orbit is expected. Red arrows point toward the central mass; blue arrows show sideways motion.
Three-path comparison: bounded model trajectories from one starting point at 1.0 (slower), 2.6 (circular reference) and 4.1 (above escape threshold), all in model units. Use the comparison button beside the visualization to switch views.
Select Compare three launch speeds to see three outcomes together. The original single-launch sandbox remains available.
Blue arrow: instantaneous velocity · Gold arrow: acceleration toward the central body. Arrow lengths are normalized for visibility, not to the same unit scale.
Launch speed uses arbitrary model units, not km/s. At 2.6, this idealized one-body orbit is approximately circular. Real orbital and escape speeds are listed below.
What's simplified
What this sandbox leaves out.
02
No air resistance
Newton's original thought experiment imagined firing above the atmosphere for exactly this reason — air drag would slow a real cannonball long before it could orbit.
Measurable fact
Real orbital speeds.
~7.8 km/sSpeed needed for a low Earth orbit.
~11.2 km/sEarth's escape velocity — enough to leave and never come back.
~30 km/sEarth's own speed orbiting the Sun.
~4.6 billion yearsApproximate age since the solar system began forming; planetary orbits have evolved over time.
Misconception check
Quick check.
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Go deeper
Keep exploring.
Next in this series →
Weight on planets ↗
Calculate your weight across 8 planets.
Orbital periods
Why do outer planets have longer years?
Use Kepler’s third law to connect distance from the Sun with orbital period.
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Solar system model
See real orbits in the interactive 3D solar system.