Why does the collective condensation of Cooper pairs below $T_c$ result in exactly zero resistance?

Answer

Scattering requires the entire coherent group to scatter simultaneously, which is statistically improbable at low energies.

Because the Cooper pairs move as one coherent quantum wave, any scattering event would require the entire group to scatter at once, which is statistically impossible given the low energy available from typical lattice vibrations.

Why does the collective condensation of Cooper pairs below $T_c$ result in exactly zero resistance?
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