Often depends on whom you ask: physicist or novelist.

In today’s New York Times Book Review (10/02/16), Anthony Doerr the novelist gives my favorite answer. You remember Doerr, the author of the terrific novel, All the Light We cannot See. Doerr reviews James Gleick’s latest, Time Travel: A History.

In his book, Gleick correctly points out the physicist’s answer, namely, that time travel as imagined by science fiction writers is not possible. One of the greatest science writers of our time, J...