The black hole became a rotating cylinder made from a material that can absorb energy. Zel’dovich imagined that light waves could extract energy from the cylinder and become amplified.

Although we think of Colt percussion revolvers as being an open-top design, there was one exception with a topstrap—the Colt 1855 Sidehammer Pocket Revolver.

The counter-rotating crankshafts get the headlines, but the MC4S’s impressive power is a product of its cylinder-head design. Gurney studied more than 200 valve-configuration variations to find ...