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Special Relativity Spacetime Lab

Special relativity made physical. A rod-train moves at speed $\beta = v/c$ and is Lorentz-contracted to $L_0/\gamma$ against its dashed rest length, while two twin clocks tick: on a round trip the travelling twin returns having aged only $2L/(\gamma\beta)$ against the stay-home $2L/\beta$. The side panel is the Minkowski diagram with the 45-degree light cone, the boosted lines of simultaneity, and the bent twin worldline.

Figure 1. Lorentz contraction, the desynchronising twin clocks, the contraction ratio, the Minkowski worldlines, and a textual reading.

WHAT TO TRY

  • Push beta = v/c toward 1: the moving rod contracts to L0/gamma, the travelling clock visibly falls behind the home clock, and the worldline on the Minkowski diagram tilts toward the light cone. All three effects share the one gamma factor.
  • Read the twin clocks side by side: the traveller ages less, the elapsed-time gap widening as you approach c. This is time dilation, not an illusion of signalling delay.
  • Watch the Minkowski diagram: the home twin runs straight up the ct axis while the traveller leans over, and the 45-degree light cone is the speed limit neither can cross.