August 1, 2021

The Coolidge effect | Science

The Coolidge effect | Science



Incredible as it may seem, a platoon of soldiers marching in step could lead to the collapse of a bridge, if the structure of the same vibrated with a frequency such that each foot strike could slightly increase the amplitude of the oscillation until, by a cumulative effect, cause fragmentation at some point, which justified the military ordinance mentioned last week. Currently, steel structures, new materials and damping systems make such an effect almost impossible (even if it is a Calatrava bridge); but what is not impossible, and in fact happens sometimes, is that unwanted vibrations occur, capable of hindering the walking of pedestrians.

Our regular commentator Lorem Ipsum mentioned the case of the London Milenium Bridge, which had to be closed to the public on the day of its inauguration by the effect of "synchronized lateral vibration" that occurred when a crowd crossed it (see comment 3 of last week ). By adjusting their pace to the vibrations of the bridge, those who crossed it ended up synchronizing their march and increasing the effect until it was difficult to maintain balance, for which reason the structure's damping system had to be considerably reinforced before reopening the bridge to the public.

When the supply stimulates the demand

In the last weeks we have talked about the Venturi effect, the Magnus effect, the Doppler effect and the resonance effect (of which we will have to speak again in its chemical meaning). There are many more interesting "effects", and their number is considerably extended if we do not limit ourselves to the field of physics. And one of the most curious, at least as regards the origin of his name, is the Coolidge effect.

In all mammalian species (including humans), males, and also females, although to a lesser extent, show a greater willingness to mate in the presence of new receptive individuals. This phenomenon is known as the "Coolidge effect" in honor of Calvin Coolidge, the 30th president of the United States, who in the twenties of the last century played a funny anecdote in relation to the effect that concerns us.

Carlo Frabetti He is a writer and mathematician, a member of the New York Academy of Sciences. He has published more than 50 scientific dissemination works for adults, children and young people, among them Damn physics, Damn mathematics or The big game. He was a screenwriter The Cristal ball

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