The vortex Perpetual motion
The age-old dream of perpetual motion, in which an object moves forever without the expenditure of any limited internal or external source of energy, became a fashionable quest for Renaissance inventors.

In the Codex Madrid, Leonardo recalled “having seen many men and from various countries brought by their infantile credulity to Venice with the great hope of gain by making mills in dead water. Being unable, after much expense, to move such a machine, they were compelled by great fury to escape from this debacle”. Carefully drawn “wheels which continually revolve” in the Codex Forster may well be the designs of others encountered in Venice. Commenting on the failure of each device, Leonardo noted that such wheels are “sophistical”. Later he exclaimed “speculators on perpetual motion, how many vain designs you have created in the like quest! Go and join up with the seekers of gold”. And yet, he was unable to resist the challenge himself!

In the belief that spirals and screws might hold a solution, he applied his beloved principle of the vortex to the problem. The design on the right of Codex Forster Fol 44r is one of a number of solutions or “compound screws” involving planar spirals, conical spirals and V-shaped configurations of tubes combined to achieve continuous motion. The water ascends to the centre of the planar spiral “s p” and then passes to the pyramidal screw “n c” running from the point at “c” to “p” and acting as an “equidistant lever” to turn the whole apparatus. As the device revolves, further “levers” would come into play, though the precise configuration or operation is far from clear. Ultimately, the quest for perpetual motion eluded Leonardo, just as it eludes modern physicists today.
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