 Venus transits are historically of great scientific importance as they were used to gain the first realistic estimates of the size of the Solar System . Observations of the 1639 transit , combined with the principle of parallax , provided an estimate of the distance between the Sun and the Earth that was more accurate than any other up to that time . The 2012 transit provided scientists with a number of other research opportunities , particularly in the refinement of techniques to be used in the search for exoplanets . 
