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Why is the Meissner effect more than simply having zero electrical resistance?

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Figure 1: Specific heat in the normal (Cen) and superconducting (Ces) states of a classic superconductor as a function of absolute temperature. The two functions are identical at the transition temperature (Tc) and above Tc. — superconductivity Figure 1: Specific heat in the normal (C_en) and superconducting (C_es) states of a classic superconductor as a function of absolute temperature. The two functions are identical at the transition temperature (T_c) and above T_c.

The Meissner effect is distinct from zero electrical resistance because it demonstrates that a superconductor is not merely a "perfect conductor," but is also a fundamentally diamagnetic material.1

For many years, it was assumed that superconductors were simply materials with infinite electrical conductivity. However, the discovery of the Meissner effect in 1933 revealed that superconductors actively expel magnetic fields from their interiors as they transition into the superconducting state.21

If a material were only a perfect conductor, it would theoretically trap any magnetic field present at the moment it became superconducting. Instead, the Meissner effect shows that the material actively repels magnetic flux, a property that cannot be explained by zero resistance alone. This discovery was crucial because it proved that the superconducting state is a unique thermodynamic phase, rather than just a state of zero resistance, and it provided the necessary foundation for developing a comprehensive theory of the electromagnetic properties of superconductors.1