Simulation · Relativity

Time Dilation Simulation

Reading time: 6 minConfidence: HighLast verified: July 2026

This simulation uses the classic "light clock" thought experiment — a photon bouncing between two mirrors — to show geometrically why a moving clock must tick more slowly, as measured by a stationary observer, purely as a consequence of light travelling at a constant speed.

Interactive simulation

Velocity (fraction of c)0.60c

Lorentz factor γ: —

Stationary clock elapsed: — s

Moving clock elapsed: — s

Dilation ratio: —

The physics behind this simulation

A "light clock" ticks once every time a photon completes a round trip between two mirrors a fixed distance apart. In the clock's own rest frame, the photon travels straight up and down. Viewed from a frame in which the clock is moving sideways, the photon must travel a longer, diagonal zigzag path to complete the same round trip — since light always travels at the same speed c in every frame, covering a longer path necessarily takes longer, meaning the moving clock ticks more slowly as measured by the stationary observer.

Δt = γΔt₀, γ = 1/√(1−v²/c²)

Common mistakeThis isn't a limitation of light clocks specifically — every kind of clock (mechanical, atomic, biological) is predicted, and has been experimentally confirmed, to dilate by exactly the same factor γ. The light clock is just an unusually clean, visualisable way to derive the effect from the constancy of the speed of light directly, not a special case that applies only to light-based timekeeping.

Sources

Taylor, E.F., Wheeler, J.A. (1992). Spacetime Physics, 2nd ed. W.H. Freeman, Ch. 3.

Last verified: July 2026 · Source: Taylor & Wheeler (1992) · Confidence: high

Interactive simulation

The physics behind this simulation

Sources

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