In 1957, 3 researchers, John Bardeen, Leon Cooper, and J. R. Schrieffer, came up with a theory that explained how superconductors worked. The theory, known as the BCS theory, helped the 3 researchers receive a Nobel Prize for its development. The BCS theory states that as electrons flow through the superconductor, they join up in pairs (called Cooper Pairs). These electron pairs are put together by phonons, which create a kind of glue-like substance. As a pair flows through the lattice structure of the superconductor, it leaves a wake behind it. The wake would then act as a pathway through the lattice structure in which other electrons could follow, so they would then avoid collisions with other particles that would disrupt the flow and create resistance. The BCS theory also explains how a superconductor loses its ability to conduct an electric current without resistance when its temperature is greater than its critical temperature. According to the theory, as the temperature of the superconducting material rises, the atomic vibrations within the material increase to the point where the lattice structure begins to vibrate too much. The increased vibration causes the electron pairs to break apart and the wake to be disrupted, causing a loss of superconductivity. However, the temperatures needed to cause superconductivity in 1957 were a lot lower than the critical temperatures today, so the BCS theory seems to no longer explain why superconductivity occurs in these new materials. Even though the temperatures are higher, scientists still feel that the electrons must pair up. There are theories now that say the electron pairing is now due to an atomic mechanism that is much stronger than the phonons of the BCS theory. Scientists call that mechanism the exciton. The BCS theory suffices for the older superconductors, but a new theory must be found for the newer high-temperature superconductors.