Tidal forces

Galileo Galilei, who was an Italian physicist, mathematician, astronomer and philosopher, is well known for his achievements and discoveries that made a great contribution to modern astronomy. Unfortunately, his theory of the tides, which by the way was a very impressive and well thought out idea, was wrong. Galileo came up with an argument for the planet’s motion based on his own theory of the tides, which disagreed with Kepler’s theory. Kepler believed that the moon caused tides on Earth, and Galileo’s theory was based on the tides caused by the Earth’s orbit around our sun and the rotation of our planet. Of course we know that Galileo’s theory was wrong, but given Galileo’s own time and his rationality, this theory was very conceivable.

Justification for the tides came to him while being on a barge traveling to Venice. Galileo observed that whenever the ship’s speed changed the water inside splashed around consequently. At that instance, he realized that the tides could not be explained without the Earth’s motion. Galileo’s argument was that Earth’s rotation and orbit around the sun had the same effect on oceans as did the water that splashed around on the barge when the speed of the barge would change.

Galileo’s argument was based on his consideration of the earth’s rotation with the orbital motion which would result in a faster speed of the surface during the night rather than in a day. So, Galileo came to the conclusion that the speeding and slowing down of the Earth causes the oceans to move back and forth, and causes the low or high tides. The part of the Earth that is not facing the sun travels faster because it’s moving in the same direction as the Earth’s rotation and orbit around the sun. It slows down when ...

... middle of paper ...

... of scientific biography, (New York:

Charles Scribner’s Sons, 1970–1980), pp. 287–288.

Shea, W. J. (1970) Galileo’s claim to fame: the proof that the earth moves from the evidence of the tides, The

British Journal for the History of Science, 5, 111–127.

Topper, D. (1990) Galileo, sunspots, and the motions of the earth, Isis, 90, 757–767.

Trefil, J. S. (1975) Introduction to the physics of fluids and solids (New York: Pergamon Press).

Wallis, J. (1666) Hypothesis on the flux and reflux of the sea, Philosophical Transactions of the Royal Society of London, 1, 263–294.

© 2011 John Wiley & Sons A/S

Copyright of Centaurus is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.