 Pippard demonstrated the reality, as opposed to the mere abstract concept, of Fermi surfaces in metals by establishing the shape of the Fermi surface of copper through measuring the reflection and absorption of microwave electromagnetic radiation (see the anomalous skin effect).He also introduced the notion of coherence length in superconductors in his proposal for the non-local generalisation of the London equations concerning electrodynamics in superfluids and superconductors.The non-local kernel proposed by Pippard, inferred on the basis of Chambers' non-local generalisation of Ohm's law) can be deduced within the framework of the BCS (Bardeen, Cooper and Schrieffer) theory of superconductivity (a comprehensive description of the details of the London–Pippard theory can be found in the book by Fetter and Walecka).