Professor Hermann Bradley has managed to have his time travel device last seventeen seconds in various past times before spectacularly exploding. Now he’s on the verge of cracking that seventeen second barrier (and, according to the narrator, possibly the wiping out of the dinosaurs as well as hundreds of thousands of people in Hiroshima, Nagasaki and Tunguska), but the damnable Professor Notkin is blocking him, claiming that Bradley has committed crimes against humanity (and perhaps against dinosaurity).
He steps through into a room and his beaming, grinning, smiling, happy-o jolly-o face shouts to the world: “We’ve done it, we’ve cracked it—thirteen seconds!”

Variants

(1)
  1. “Shall I Tell You the Trouble with Time Travel?” by Adam Roberts, in Solaris Rising: The New Solaris Book of Science Fiction, edited by Ian Whates (Solaris, November 2011).
    2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . written by Adam Roberts