Unusually for the time, the story adhered to the laws of physics as they were known by showing a starship that was limited by the speed of light and took several years to travel between the stars.

Shortly after the elderly Bradley's death, Jack discovers that a Centaurian spaceship is approaching the Adastra, and he suspects that its intention is hostile.

Leinster not only worked within the constraints of the theory of relativity but also even calculated that a trip to Proxima Centauri would take seven years if the ship traveled under a constant acceleration and deceleration of one gravity.

Leinster also notes that such an acceleration would bring the ship to a significant fraction of the speed of light, but he fails to take account of the resulting time dilation, which would reduce the subjective length of the trip by at least two years.

Asimov also writes, "The thing I remember most clearly over the years about 'Proxima Centauri' is the peculiar horror I felt at the thought of a race of intelligent plants that lusted after animal food.

It is almost an unfailing recipe for a startling science fiction story to begin by inverting some thoroughly accepted situation, something so ordinary as to be almost disregarded.