an astronaut (member of the crew of a spaceship or other spacecraft, or someone trained for that purpose)

xenobiology (speculative biology of extraterrestrial life)

(astronomy) cosmic background radiation

(engineering) aerospace engineering

successive series of questions and responses

vicissitudes, the way that the world or a person prospers one day and declines the next

dotting the i's and crossing the t's

You should treasure every encounter, for it will never recur.

a unit of volume equal to 1,200 millet grains

personal