Velocity
Speed v / c
0.6000 c
Presets
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Light-Clock Readout
Lorentz γ1.250
v / c0.600
Proper time τ0.00 s
Dilated time t0.00 s
Ticks (stationary)0
Ticks (moving)0
The light clock. A photon bounces between two mirrors
a fixed distance L apart. In the clock's own rest frame it travels
straight up and down — one round trip (one "tick") takes
τ = 2L / c.
Seen from a frame in which the clock moves sideways at speed v, the photon must also cover the sideways distance the clock travels during the bounce, so it follows a longer diagonal path. Because light speed c is the same in every frame, that longer path takes more time: t = γ·τ, where γ = 1 / √(1 − v²/c²). This is the textbook derivation of time dilation — no assumption beyond "c is constant" is used.
Seen from a frame in which the clock moves sideways at speed v, the photon must also cover the sideways distance the clock travels during the bounce, so it follows a longer diagonal path. Because light speed c is the same in every frame, that longer path takes more time: t = γ·τ, where γ = 1 / √(1 − v²/c²). This is the textbook derivation of time dilation — no assumption beyond "c is constant" is used.