Special-relativity journey

Travel between the stars and compare Earth time with the proper time experienced aboard your spacecraft.

Earth → Proxima CentauriSplit-frame comparison

Velocity0.9500c

Lorentz factor3.203

Earth time4.47 y

Traveller time1.40 y

Contracted distance1.32 ly

Journey clocks

Spacetime diagram

Time dilation

Earth measures a longer coordinate time. The traveller’s own clock always runs normally and records the shorter proper time.

Length contraction

In the spacecraft frame, the distance along the direction of travel is L₀/γ. The spacecraft does not see itself contracted.

The speed limit

Relativistic kinetic energy grows without bound as a massive object approaches c, so it cannot reach or exceed light speed.

Model note: Constant-speed journeys idealise acceleration as instantaneous. Visual starfield and colour shifts are illustrative; clock, Lorentz and length calculations use special relativity.