Discovered in 1933 by Walther Meissner and Robert Ochsenfeld, who measured magnetic flux expulsion from tin and lead samples cooled below their superconducting transition in an applied field.
Fritz and Heinz London explained the effect in 1935 via ∇²H = λ⁻²H, showing that external magnetic fields decay exponentially inside the surface over the London penetration depth λ.
Because a superconductor expels pre-existing flux during field cooling rather than trapping it, the Meissner state (χ_v = −1) is a history-independent thermodynamic phase distinct from a classical perfect conductor.