Experimental consequences of predicted charge rigidity of superconductors

► We examine the charge rigidity of a metal entering the superconducting state. ► BCS theory predicts no change, instead our theory predicts a drastic change. ► This should be seen in experiments measuring the plasmon dispersion relation. ► It should also be seen in an increased screening length for electrostatic fields. ► We also interpret several existing puzzling experimental results with our theory.