How did the engineer behind the Eiffel Tower help explain how wings fly?

He turned his own tower into a laboratory. Gustave Eiffel's first aerodynamic experiments dropped a test surface and a measuring apparatus down a cable stretched from the tower's second level to the ground, and showed that a body's air resistance is very closely related to the square of its airspeed. Then, in a wind tunnel he built at the tower's foot in 1909, he studied the wing shapes used by early aviation pioneers such as the Wright brothers, and established that a wing's lift comes from reduced air pressure above it rather than from extra pressure pushing on its underside.

His road to the lab ran through a courtroom. Eiffel had been contracted to design and build locks for the French effort to dig a canal across Panama, and when the canal company collapsed, he was implicated in the scandal that followed. In 1893 he was found guilty of misusing funds, fined and sentenced to prison, though he was acquitted on appeal. Shortly before the trial he resigned from the company that bore his name, declaring that he would abstain from any manufacturing business from then on and insisting that his name be removed from it.

Wind was not a new subject for him: his interest in aerodynamics grew out of the problems wind forces had caused for the structures he had built. He set up a laboratory at the foot of the tower in 1905, and after neighbors complained about the noise of his wind tunnel, he moved his experiments to Auteuil in 1912.

The work mattered to the young science of flight. In 1913 the Smithsonian Institution awarded him the Langley Medal for Aerodromics, and in his speech Alexander Graham Bell said that Eiffel's writings on air resistance had already become classical, giving engineers the data to design flying machines on sound scientific principles. The man once dragged through a canal-company trial ended up helping explain how to leave the ground.