In what year was the transistor invented?

1947 → tub · rake.

In December 1947 at Bell Labs, John Bardeen, Walter Brattain and William Shockley demonstrated the first working transistor — a tiny solid lump of semiconductor that could switch and amplify electrical current. It replaced the fragile, power-hungry, room-heating vacuum tube, and because transistors could be made ever smaller it set computing on its path to shrinking without limit. The three shared the 1956 Nobel Prize in Physics, and the transistor is often called the most important invention of the twentieth century. Peg 19 · 47 → tub · rake: a rake standing in a tub.

Go deeper:

• The History of Computing — Vacuum Tube to Transistor to Integrated Circuit — a short documentary on the switch from bulky tubes to the transistor and on to the chip.