 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 . 
 Venus transits <a href='drop_aux' title='1'><mark>are</mark></a>historically of great scientific importance as they <a href='uninflect' title='2'><mark>were</mark></a> 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 <a href='null_relcl' title='3'><mark>that</mark></a>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 . 
Venus transits historically of great scientific importance as they was used to gain the first realistic estimates of the size of the Solar System . Observations of the 1639 transit , combined with da principle of parallax , provided an estimate of the distance between the Sun and the Earth was more accurate than any other up to that time . Tda2012 transit provided scientists with a number of other research opportunities , particularly in the refinement of techniques to be used in the search fir exoplanets .