How Dante beat Galileo to law of motion by 300 years
Tim Radford, science editor
Thursday April 7, 2005
The poet Dante Alighieri knew about modern physics as well as sophisticated rhyme. Some 300 years ahead of Galileo, the great poet of hell, purgatory and heaven described a physical law of motion now known as Galilean invariance, an Italian physicist reports today.
Galileo's principle says the laws of physics are the same in all inertial frames of reference. That is, someone moving at uniform speed observes the same experimental results as someone not moving at all. This principle became one of the foundations of the science built up by Newton and others.
But, writing in the journal Nature, Leonardo Ricci, of the University of Trento, northern Italy, says Dante spotted the same thing early in the 14th century. He did not pursue the logic but did describe it in canto 17 of his epic work Inferno.
In this canto, Dante and his guide, Virgil, descend from one circle of eternal torment to another by climbing on the back of the winged monster Geryon. In what is thought to be the first description of the sensation of flying, Dante is aware only of the air and the monster below him.
In a translation by the American poet Henry Wadsworth Longfellow, the canto runs:
Onward he goeth, swimming slowly, slowly
Wheels and descends, but I perceive it only
By wind upon my face and from below.
[Ella sen va notando lenta lenta;
rota e discende, ma non me n'accorgo
se non che al viso e di sotto mi venta.]
The lines reveal a remarkable intuition. "The observer Dante can imagine himself in a frame that a contemporary physicist would define, with a fair approximation, as inertial," Dr Ricci said.
Dante understood that such a wide spiral flight would be felt as motion in a straight line. But also, "Dante asserts that, aside from the effect of the wind, his sensation of flying was not dissimilar from being at rest ... this invariance [agrees] with the concept expressed by Galileo ... It seems Dante was well ahead of his time with regard to views about the laws of nature held in the middle ages."
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