Tycho Brahe, Kepler and the laws of planetary motions (Alberto Righini, Department of Physics and Astronomy University of Florence - Italy)

The international year of astronomy, which has been celebrated in the year 2009 to recall Galileo Galilei first telescopic observation, has not enough emphasized that 400 years ago in Prague Kepler published the first two laws of the planetary motion in his Astronomia Nova. These laws were the final result of a long intellectual adventure started perhaps in Stonehenge, or in the Nile Valley or in the Mesopotamian countries, continued by Hipparchus and Ptolemy, Ulug Begh and completed by Tycho and Kepler. The results obtained by Kepler were achieved thanks to the dramatic increase of the precision of Tycho’s astronomical measurements at the limit of the eye’s angular resolving power due to the technological improvements of the instruments, and to the strict observing protocols.