String (beads)
Endpoints (v → c)
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String theory's founding insight was that a fundamental particle is not a point but a tiny vibrating string, and each vibrational/rotational state corresponds to a different particle. This simulator renders a real relativistic open string — tension T, proper length L — spinning rigidly about its center with its endpoints approaching the speed of light, exactly the classical picture that first connected string theory to particle physics. Live readouts track the string's mass M = πTL, angular momentum J = πTL²/4, and the Regge slope α' = J/M², which stays constant as you change the string's length yet tilts when you change its tension — the defining signature of a Regge trajectory. An excitation-mode slider layers quantized transverse harmonics onto the spinning string, visualizing how the full particle spectrum builds on top of the classical rotation.