While sorting through the attic, elderly Mike Sakler finds a note from himself detailing how he must go back in time to save his grandfather from a mugging near the 1939 New York World’s Fair.
Indeed the notes from that page on were most curious. “Planck energy for opening gap in spacetime fabric = 1019 billion electron volts,” read one, but then that was crossed out with a large X as the writer of the notes took a different tack.

Variants

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  1. “Knot Your Grandfather’s Knot” by Howard V. Hendrix, in Analog, March 2008.
  2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . written by Howard V. Hendrix