The Earth's interior is composed of four layers, three solid and one liquid—not magma but molten metal, nearly as hot as the surface of the sun. The deepest layer is a solid iron ball, about ...

The four-layer diode was the key to William Shockley's plan to revolutionize AT&T's phone system. It was a great device in theory, but not in practice -- at least not at the time when Shockley ...