Running, swimming and flying occur in vastly different physical environments and, likewise, involve quite different body mechanics. Nonetheless, there are strong convergences in certain functional characteristics of runners, swimmers and fliers.

To run or fly at optimal speed is to strike a balance between the vertical and horizontal loss of energy.

Adrian Bejan

The Earth with its solar heat input, heat rejection, and wheels of atmospheric and oceanic circulation, is a heat engine without [a] shaft. Its maximized mechanical power cannot be delivered, but is instead destined to dissipate through air and water friction and other forms of heat loss. It produces maximum power, which it then dissipates at a maximum rate.

Adrian Bejan

It was swimming that stumped us. Everyone knows that, in water, fish are weightless.

Adrian Bejan