U.S. scientists have succeeded in squeezing hydrogen so intensely that it has turned into a metal, creating an entirely new material that might be used as a highly efficient electricity conductor at room temperatures. The discovery, published in the journal Science on Thursday, provides the first confirmation of a theory proposed in 1935 by physicists Hillard Bell Huntington and Eugene Wigner that hydrogen, normally a gas, could occur in a metallic state if exposed to extreme pressure.