A physics professor discovers a mysterious metallic substance that can alter its weight based on thought. This substance, named tellecarbon, exhibits strange properties, including the ability to float or become incredibly heavy depending on the mental focus of its users. The professor and his colleagues experiment with it, eventually realizing its potential for propulsion. They construct a spaceship powered by tellecarbon, intending to travel to Mars. As they embark on their journey, they experience the wonders of space, but soon face a crisis when the tellecarbon seems to take control of the ship, propelling them away from their intended destination. The crew grapples with fear and uncertainty, realizing that their thoughts and emotions may influence the substance's behavior. They hypothesize that the tellecarbon has developed a form of intelligence, leading them to consider the possibility that it is searching for companionship. In a moment of desperation, they decide to help the tellecarbon find another piece of itself, which they believe will allow them to regain control of their ship. They spot another chunk of tellecarbon and, through a series of mental communications, manage to convince it to return to Earth in exchange for its freedom. The ship successfully lands back on Earth, and the tellecarbon, now affectionately named Tillie, escapes into the sky, seemingly to reunite with its counterpart. The protagonist reflects on the adventure, which not only involved scientific discovery but also personal growth and romance, culminating in a marriage and the birth of a child. The story concludes with a hint of the tellecarbon's return, suggesting that its journey is far from over, and leaving the protagonist and his partner in a state of wonder and joy.
By Robert Silverberg · First published 1973 · Genre: Science Fiction, Fantasy, Adventure