The equivalence principle

Equipment

• 3D canvas: accelerating elevator plus curved-grid view near a mass
• Slider “accelerating frame” (frame acceleration)
• Slider “Tốc độ thời gian” (animation speed) and “Tạm dừng” button

Procedure

1. Release a body in the accelerating frame

   Set a moderate acceleration on the “accelerating frame” slider and watch the free body's path in the elevator. In the accelerated frame it appears to fall with acceleration $a$, exactly as if a uniform gravitational field $g=a$ pulled it — no local experiment distinguishes the two.

2. Match acceleration to gravity

   Raise and lower the acceleration and compare with the warped-grid view near the mass. Find the slider setting where the apparent fall in the elevator reproduces free fall in the gravitational field, confirming $a_{\mathrm{frame}}\leftrightarrow a_{\mathrm{grav}}$.

3. Probe the local limit

   Ask what would spoil the equivalence: over a large region, tidal effects — the variation of g from place to place — betray real gravity. Pause the model and explain why the equivalence principle holds only in a sufficiently small neighborhood and is the seed of curved-spacetime gravity.

Simulation

Experiment history

Related physicists

Related library topics