- Uexküll, Jakob von
- uncertainty principle
- uncoordinated hypotheses are like protoplasm
- underdetermination
- underground methane tries to get to the Earth surface
- uniformitarianism is like bookkeeping
- unit of analysis
- unstable atom is like a miser
- unvaccinated people are like fish in a barrel
- unwelt
- uranium bomb did not need to worry about imploding
- useful ambiguity