Flash (1959) #139
First appearance and origin of Professor Zoom, the Reverse-Flash. "Menace of the Reverse-Flash!" is drawn by Carmine Infantino. Cover by Infantino and Murphy Anderson. It was seen as a triumph of science. A time capsule sent into a super-fast orbit around the Earth is flung into the future instead of being buried in the ground. But the brilliant young physicist who dreamed up this scientific marvel is horrified when he realizes that the Atomic Clock he placed in the capsule will become an atomic bomb once it reaches its 25th Century destination.
Enter the Flash, the Fastest Man Alive, who vows to use the Cosmic-Powered Treadmill to travel to the future and make sure the Atomic Clock doesn't harm anyone. But another object in the capsule is one of the Flash's spare costumes, an artifact that is taken by a brilliant thief who sees it as his opportunity to gain the ability to move at super-speed. Dying the costume the opposite color scheme of the Flash and calling himself Professor Zoom, this crook launches a crime spree. It's up to our hero, the Flash, to catch up with Zoom and stop a nuclear disaster in under one hour!