Well, I did run some numbers and he had enough of a grasp of Newtonian stuff to do some calculations, sorta - but mostly because he used the line that they'd been accelerating at 1 gee for 40 hours and needed to work out the distance - but there isn't much clarity on how that works in the context of the alien solar system, and he keeps using AU as a unit of distance which isn't all that easy to work with.