“Gravity’s books have got to balance.”
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 17, “Disaster” (p. 177)

Farmer In The Sky is a 1950 science fiction novel by American writer Robert A. Heinlein about a teenaged boy who emigrates with his family to Jupiter's moon Ganymede, which is in the process of being terraformed. Among Heinlein's juveniles, a condensed version of the novel was published in serial form in Boys' Life magazine , under the title "Satellite Scout". The novel was awarded a Retro Hugo in 2001.Passing references by the lead character to the song "The Green Hills of Earth" and to its author, Rhysling, have caused some to consider it part of Heinlein's Future History series.
“Gravity’s books have got to balance.”
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 17, “Disaster” (p. 177)
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 12, “Bees and Zeroes” (p. 125)
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 2, “The Green-Eyed Monster” (p. 21)
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 4, “Captain DeLongPre” (p. 50)
“Pioneers need good neighbors.”
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 14, “Land of My Own” (p. 147)
“Horses can manufacture more horses and that is one trick that tractors have never learned.”
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 18, “Pioneer Party” (p. 187)
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 20, “Home” (pp. 218-219)
“I’m not raising any kids to be radioactive dust.”
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 18, “Pioneer Party” (p. 198)
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 16, “Line Up” (p. 161)
“You can only grieve so much; after that it’s self pity.”
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 18, “Pioneer Party” (p. 188)
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 18, “Pioneer Party” (p. 196)
“Bill, why is it that some apparently-grown men never learn to do simple arithmetic?”
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 14, “Land of My Own” (p. 142)
“It was so darn quiet you could hear your hair grow.”
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 13, “Johnny Appleseed” (p. 131)
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 18, “Pioneer Party” (pp. 193-194)
Robert A. Heinlein book Farmer in the Sky
Source: Farmer in the Sky (1950), Chapter 9, “The Moons of Jupiter” (pp. 90-91)