Underlying The Secret of the Ninth Planet is the belief that space exploration is important to the well-being of humanity. In Wollheim's vision of the future, humanity establishes a presence in space stations and on the moon before discovering the alien threat. Implicit in the story is the belief that the peoples of Earth need to be prepared to face a possible threat from outer space, whether it be alien invaders or asteroids on a collision course with Earth.

The novel has a strong bias in favor of advanced technology and scientific research, and Wollheim provides brief and somewhat dry explanations for each of the wonders he introduces, including the antigravity drive. He points out that his conception of an antigravity drive is different from that found in H. G. Wells's The First Men in the Moon (1901), which defies known laws of physics. Wollheim...