Meanings
- natural sciencesA physical paradox that arises when considering the buoyant force exerted on a relativistic bullet (or in a submarine) immersed in a fluid subject to an ambient gravitational field. If a bullet has neutral buoyancy at rest in a perfect fluid and is then launched at relativistic speed, observers at rest within the fluid would conclude that the bullet should sink, since its density will increase due to the length contraction effect. On the other hand, in the bullet's proper frame it is the moving fluid that becomes denser and hence the bullet would float.
Synonyms: submarine paradox
Synonyms & antonyms
proper nounA physical paradox that arises when considering the buoyant force exerted on a relativistic bullet (or in a submarine) immersed in a fluid subject to an ambient gravitational field. If a bullet has neutral buoyancy at rest in a perfect fluid and is then launched at relativistic speed, observers at rest within the fluid would conclude that the bullet should sink, since its density will increase due to the length contraction effect. On the other hand, in the bullet's proper frame it is the moving fluid that becomes denser and hence the bullet would float.
Origin
First formulated by James M. Supplee (1989).
Full word history & related roots →Cite this entry
Supplee's paradox. (n.d.). In WatkinsX Dictionary. Retrieved November 5, 2026, from https://dictionary.watkinsx.com/word/Supplee's%20paradox
“Supplee's paradox.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/Supplee's%20paradox. Accessed November 5, 2026.
WatkinsX Dictionary, s.v. “Supplee's paradox,” accessed November 5, 2026, https://dictionary.watkinsx.com/word/Supplee's%20paradox.
Source: Supplee's paradox on Wiktionary, CC BY-SA 4.0.