Physics
Jet propulsion is most effective when the Reynolds number is high - that is, the object being propelled is relatively large and passing through a low-viscosity medium.
In biology, the most efficient jets are pulsed, rather than continuous: at least when the Reynolds number is greater than 6.
Read more about this topic: Jet Propulsion
Famous quotes containing the word physics:
“The fundamental laws of physics do not describe true facts about reality. Rendered as descriptions of facts, they are false; amended to be true, they lose their explanatory force.”
—Nancy Cartwright (b. 1945)
“We must be physicists in order ... to be creative since so far codes of values and ideals have been constructed in ignorance of physics or even in contradiction to physics.”
—Friedrich Nietzsche (1844–1900)
“Although philosophers generally believe in laws and deny causes, explanatory practice in physics is just the reverse.”
—Nancy Cartwright (b. 1945)