A light clock ticks each time a photon completes a round trip between two mirrors. In the spacecraft's own frame the photon travels straight up and down, but in the laboratory frame the spacecraft has moved sideways during the trip, so the photon follows a longer diagonal path. Since light speed is the same in both frames, the laboratory sees the moving clock tick more slowly.
• Two mirrors, a clock photon, the current round-trip path, a laboratory clock and a spacecraft clock in one interactive 3D scene. • Controls for spacecraft velocity (0 to 0.95c), the photon-path frame (Laboratory or Spacecraft) and explanatory moving markers. • Readouts for Lorentz factor, laboratory elapsed time, spacecraft proper time, laboratory and rest round-trip periods, and the difference between lab and spacecraft time. • Two experiments: at rest both clocks agree with a 2 s period; at 0.8c γ = 5/3 so 10 lab seconds correspond to 6 spacecraft seconds.
With mirror spacing L = 1 light-second the rest round trip takes Δτ = 2L/c = 2 s. The laboratory period is Δt = γΔτ, so Δt = 2γ s, and the spacecraft proper time satisfies τ = t√(1 − β²). The diagonal path in the lab frame is just the Pythagorean consequence of a constant light speed.
The model assumes constant velocity, transverse light-clock motion, and no acceleration or gravity. The path drawing covers the current round trip and is repositioned after each cycle, while elapsed totals keep running. The frame selector only changes how the photon path is drawn; readouts keep the lab coordinate-time convention. The effect is frame-dependent comparison, not a damaged mechanism.
No. In the spacecraft frame the photon travels straight between the mirrors and the clock ticks normally. Dilation only appears when comparing against another frame, and the simulator shows both paths by switching the photon-path frame.
The Lorentz factor is 5/3, so a moving clock accumulates 3/5 of the laboratory time. The Fast spacecraft experiment shows 10 lab seconds corresponding to 6 spacecraft seconds.
While the photon rises and falls, the mirrors move sideways with the spacecraft, so the photon traces a diagonal. Light speed is the same, so the longer path takes longer, giving Δt = γΔτ.
No. It models constant-velocity motion in flat spacetime only. For the gravitational case see the Gravitational Time Dilation lab, and for acceleration effects see The Twin Paradox lab.