one thing from project hail mary the book that i really wish theyd made clear in the movie is that when grace makes the decision to save rocky instead of go back to earth, he is prepared to die. like i understand why the movie had to cut a lot from the book for pacing and it wasnt exactly necessary to include the whole sub-subplot where rocky and grace figure out that there is nothing on erid that is safe for humans to consume, but it would have been worth a passing mention at some point, because grace goes back for rocky knowing that even if rocky takes him to erid, he will still die there, because there is nothing he can eat. the only reason he survives is by eating taumoeba, which is a solution rocky comes up with only after grace saves him and admits to him that he came to his rescue fully prepared to die.
the movie really breezes past rocky's rescue and the time skip, and it never explains why choosing to save rocky is so monumental in the first place: it answers the central question grace is grappling with for the whole movie. "who would i die for?" he doesn't just go back for rocky because it's the right thing to do. he sacrifices himself to save rocky. he is ready to die if it means rocky will live.
