Ripples in the Dirac Sea
by Geoffrey A. Landis
A physics guy invents a time machine that can go only backward and must always return the
traveler to the exact same present from which he left.
— Michael Main
- Travel is possible only into the past.
- The object transported will return to exactly the time and place of departure.
- It is not possible to bring objects from the past to the present.
- Actions in the past cannot change the present.
“Ripples in the Dirac Sea” by Geoffrey A. Landis, in
Asimov’s Science Fiction, October 1988.