One of the most potent themes of the novel is the idea that scientific discoveries become dangerous in the wrong hands, especially with those with political power. In the first chapter, Si distrusts Rube and the military. He is outraged by the threat of government overreach and the thought of them spying on him. While this distrust is not specifically about science, it does demonstrate the government’s abuse of power and the lack of oversight to control those in charge. This hints at the kinds of corruption that can occur with military or governmental power.

The major example of this theme, however, is the opposing ethics between Danziger and Esterhazy. Danziger represents scientific discovery tempered by a strong moral compass, while Esterhazy represents military/nationalistic zeal without limits or ethical boundaries. As the time travel project is Danziger’s creation and passion, one might assume he would be willing to do whatever is necessary to see it succeed. Yet it is he, not Esterhazy, who decides it should be stopped at all costs—including, unbeknownst to him, his own life.

Danziger believes there is a line they should not cross, even in the name of scientific discovery. When he feels the risks of the project outweigh the benefits, he demands that they stop.