When Rooke is 24, the King of England decides that the British territory New South Wales should become a penal colony. Dr. Vickery writes to Rooke and suggests that the expedition—bringing British prisoners to New South Wales—might need an astronomer. Rooke writes back the same day. Dr. Vickery then explains to Major Wyatt, Rooke's superior, why Rooke must be brought along as an astronomer: Dr. Vickery predicts that a significant comet will return in 1788, will only be visible in the southern hemisphere, and that the event will be as significant as Halley's Comet. Rooke thinks that Major Wyatt isn't entirely convinced by all this but isn't willing to argue with Dr. Vickery.
Here, Rooke jumps at the chance to use the military system as an excuse for continuing his preferred pursuits, which shows that Rooke is not yet willing to look outside of social norms or structures, even within inherently violent systems like the military. The way that Dr. Vickery describes the comet shows storytelling doing Rooke a favor: it paints the observation of the comet as an absolute necessity, and Dr. Vickery uses his power as the Astronomer Royal to make this assertion true.
Rooke tries to think of the expedition to New South Wales as a fresh start, and thinks he might be the only astronomer to record Dr. Vickery's comet. Rooke knows that ten years ago he would've considered an opportunity like this as something owed to him, but he understands now that life gives, but also takes. He buys notebooks and for the first time in a long time, feels happy as he thinks about what he'll record in their pages.
Though Rooke does frame his involvement with the First Fleet as something that will benefit him as a person, his joy in the scientific discoveries shows that he still prioritizes rational, scientific thought over his emotional sense of humanity.
Rooke receives a letter from Silk at the same time he receives Dr. Vickery's letter. Silk encourages Rooke to volunteer for the First Fleet and says that he's already been promoted to the title of Captain-Lieutenant. Further, a man in Piccadilly has promised to publish whatever Silk writes about New South Wales. Rooke realizes that Silk isn't much of a soldier, either, and has been waiting for his chance to be a writer. He understands that Silk thinks about writing the same way Rooke thinks about numbers.
At this point, Rooke thinks of Silk's storytelling and his own love of science as two different ways of telling the truth. Yet though they're entirely different ways of thinking about it, they accomplish the same goal. This suggests that Rooke still thinks of Silk's narratives as being mostly factual and therefore on par with his science (which he also assumes to be objective and detached).
Anne pulls out the globe that Rooke made for her when he left for the war in America. He tells her that the sky is different in the southern hemisphere. She cautiously asks if he'll see the moon upside down, and he realizes she's afraid of disappointing him by sounding stupid. Anne promises she'll look at the moon and think of Rooke, and then smiles and adds that she'll stand on her head so they can look at it the same way. Later, when he takes out his red military jacket, Rooke feels nauseous smelling the gunpowder and sweat.
Rooke's uniform is a loud and clear symbol that he's a part of the British military. He cannot escape its legacy of violence when he wears the uniform, which is reinforced by his reaction to smelling the gunpowder on his jacket. His nausea is a very emotional, human reaction. It's a reflex, which drives home again that Rooke is very much an emotional individual, even if he tries to act otherwise.