The 2004 transit of Venus was an opportunity to explain how mankind succeeded to mesure the universe: during centuries, it was not possible to know the distance Earth- Sun which is the basis of the measurements in astronomy. During the XVIIIth century, the observation of the transit of Venus allows to know this distance. Through an international project VT-2004, we proposed to make the same observation on June 2004 but with another goal: astronomers were replaced by pupils, students and amateur astronomers and travels to favorable sites were replaced by the use of Internet. The VT-2004 project was a success with several thousands of observers worldwide sending their observations to a central site through Internet allowing to re-measure the Astronomical Unit with a good accuracy The transits of Venus are very rare (two times every century) and we plan to do a similar project in 2012.