the medal has been awarded to more than one person at once; in 1938 it was won by john cockcroft and ernest walton "for their discovery that nuclei could be disintegrated by artificially produced bombarding particles", in 1981 by peter higgs, thomas walter and tom w. b. kibble "for their international contributions about the spontaneous breaking of fundamental symmetries in elementary-particle theory", in 1982 by drummond matthews and frederick vine for explaining the magnetic properties of the ocean floors which then led to the plate tectonic hypothesis, and in 1988 by archibald howie and m.j. whelan for their work on the theory of electron diffraction and microscopy, and its use in the study of lattice defects in crystals.