“Gravity’s books have got to balance.”
Source: Farmer in the Sky (1950), Chapter 17, “Disaster” (p. 177)
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Robert A. Heinlein 557
American science fiction author 1907–1988Related quotes
McKeon, Belinda. Metaphysics gets a Mayo accent http://www.irishtimes.com/culture/metaphysics-gets-a-mayo-accent-1.441635, The Irish Times (13 May 2005)

“You've got to balance the compassionate-use aspect with trying to figure out whether it works.”
Quoted by the New York Times http://www.nytimes.com/2014/08/09/health/in-ebola-outbreak-who-should-get-experimental-drug.html?_r=0 (August 9, 2014), regarding the Ebola virus epidemic in West Africa.

“I've got forward momentum. There's no virtue in it. It's just a balancing act. I don't dare stop.”
Source: Vorkosigan Saga, The Warrior's Apprentice (1986)

“He's got great balance and great vision, and Emmitt has earned his starting spot.”
Galen Hall — reported in United Press International (October 11, 1987) "Emmitt Smith is a Gator on the loose", Houston Chronicle, p. 5.
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Lecture 1: Inflationary Cosmology: Is Our Universe Part of a Multiverse? Part I.
The Early Universe (2012)