Galileo Galilei, an Italian physicist, mathematician, astronomer and philosopher, is well known for his achievements and discoveries which made a great contribution to modern astronomy. Unfortunately, his tidal theory, which was indeed a very impressive and well thought out idea, was wrong. Galileo put forward an argument for the motion of the planet, based on his own theory of tides, which disagreed with Kepler's theory. Kepler believed that the Moon caused the tides on Earth, and Galileo's theory was based on tides caused by 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 time and rationality, this theory was entirely conceivable. The vindication of the tides came to him while he was on a barge en route to Venice. Galileo observed that whenever the ship's speed changed, the water inside splashed accordingly. At that point he realized that tides could not be explained without the movement of the Earth. Galileo's argument was that the Earth's rotation and orbit around the sun had the same effect on the oceans as the water splashing on the barge when the speed of the barge changed. Galileo's argument was based on his consideration of the Earth's rotation with orbit. movement that would cause the surface to move faster at night than during the day. Thus, Galileo came to the conclusion that the speed and slowing down of the Earth causes the oceans to move back and forth and cause low or high tides. The part of the Earth that does not face the sun moves faster because it moves in the same direction as the Earth's rotation and its orbit around the sun. It slows down when...... middle of article ...... of a scientific biography, (New York: Charles Scribner's Sons, 1970-1980), pp. 287-288. Shea, W.J. (1970) Galileo's claim to fame: evidence that the earth moves from the evidence of tides, TheBritish Journal for the History of Science, 5, 111-127.Topper, D. (1990 ) Galileo, sunspots and the movements of the earth, Isis, 90, 757-767.Trefil, JS (1975) Introduction to the physics of fluids and solids (New York: Pergamon Press).Wallis, J. (1666 ) Hypothesis on the ebb and flow of the sea, Philosophical Transactions of the Royal Society of London, 1, 263-294. © 2011 John Wiley & Sons A/SCopyright of Centaurus is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a mailing list without the express consent of the copyright holder of author. written authorization. However, users may print, download, or email articles for individual use..