Mike Marcum didn’t have a lab, funding, or a PhD. Just a pile of salvaged electronics — and a theory. One night in Missouri, he fired up his homemade device. It formed a vortex. He tossed in a screw.

SCIENTISTS have built the world’s first time machine — sort of. Working with electrons in the bizarre realm of quantum mechanics, they first created the equivalent of a break for a game of pool. The ...