Bardeen, Brattain, Shockley · The transistor
What switches an electrical signal?
That time, that place
Telephone networks and early computers switched signals with vacuum tubes: glass, breakable, hot, power-hungry and short-lived.
ENIAC used some seventeen thousand of them, and one failure stopped the machine.
Why this question
Bell Labs was looking for a way to do the same job inside a solid. The clue was semiconductors — neither conductor nor insulator, and their conduction changes sharply with tiny amounts of added impurity.
Quantum mechanics explains why. In a regular lattice of atoms the energies an electron may hold fall into bands, and managing the gap between them lets you govern the flow.
What was found
In December 1947 Bardeen and Brattain pressed gold foil onto a piece of germanium and used a small signal to govern a large one. Shockley produced a sturdier design the next year.
This is the switch inside every computer — the thing that makes on and off, one and zero. A current chip holds tens of billions of them.
Quantum mechanics, which had looked entirely impractical, becomes an industry here.
Switching belonged to hot, fragile glass tubes
A small input governing a large output at a germanium contact
Electronics became small, cheap and durable. Computers moved onto desks