The Propagation of Light In a Vacuum (Unabridged) [Unabridged Fiction‪]‬

As humankind's first starship accelerates past the speed of light, an astronaut wakes up and finds that he is all alone. The crew is gone, the sensors give no readings, and he is trapped. Alone? Not quite. His imaginary wife keeps him company and helps him keep a tenuous hold on his sanity. Maybe he should have believed the scientists who said it was impossible to exceed the speed of light, because now the impossible haunts him at every turn.
Author James Patrick Kelly is a two-time winner of the Hugo Award and a 2007 Nebula Award winner. His stories appear frequently in Asimov's Science Fiction, and he writes the magazine's "On the Net" column. Publishers Weekly has called him "a meticulous craftsman in the demanding short-story form".