concept

Froude number

A dimensionless number that measures the rhythm of gait: v² divided by (g times L) - velocity squared, over gravity times leg length. The beautiful core idea is that two animals of different sizes move in the same way when their Froude numbers match. Because gait transitions sit at fixed Froude values (walk to trot around 0.5, the ceiling of walking around 1.0), you can calculate the exact speed at which an animal must change gait. Change the gravity and you change that speed: Pandora's lower gravity pulls every threshold down to a lower velocity, so the pa'li breaks into its spring-loaded gaits sooner than it would on Earth.