The Tortoise and the Hare

Revised version of Fig. 1, showing that the aircraft data line up with the animal fliers when the effect of lower air density and drag at higher altitudes is taken into account.

"The fastest animals and vehicles are neither the biggest nor the fastest over lifetime" is the subtitle of A. Bejan, U. Gunes, J. D. Charles, and B. Sahin in their Nature Scientific Report published the 27 August 2018.

Thanks to their theory, in this article, the authors explained phenomena such as the emergence of animal "outliers":  higher speed at smaller body mass.

They show that what accounts for the animal outlier also accounts for the vehicle outlier: military jet fighter are smaller and reach speeds higher than the biggest commercial aircraft. Yet, like the cheetah, the jet fighter spends most of its active life at rest, on the ground, out of sight.  This new view gives the word ‘outlier’ a different meaning: the jet fighter is the outlier because, during its overall lifetime, it is slower than the bigger commercial aircraft, which spend most of its time flying.

This new meaning is in fact the oldest, taught by Aesop in his fable "The Tortoise and the Hare”: what matters in the life of the mover is the movement - i.e. the territory covered, the speed averaged - over the whole lifetime.

• A. Bejan, U. Gunes, J. D. Charles & B. Sahin, The fastest animals and vehicles are neither the biggest nor the fastest over lifetime, Scientific Reports, volume 8, Article number: 12925 (2018), Nature, 27 August 2018.