 Sometimes Venus only <unk> the Sun during a transit . In this case it is possible that in some areas of the Earth a full transit can be seen while in other regions there is only a partial transit ( no second or third contact ) . The last transit of this type was on 6 December 1631 , and the next such transit will occur on 13 December <unk> . It is also possible that a transit of Venus can be seen in some parts of the world as a partial transit , while in others Venus misses the Sun . Such a transit last occurred on 19 November <unk> BC , and the next transit of this type will occur on 14 December 2854 . These effects occur due to parallax , since the size of the Earth <unk> different points of view with slightly different lines of sight to Venus and the Sun . It can be demonstrated by closing an eye and holding a finger in front of a smaller more distant object ; when you open the other eye and close the first , the finger will no longer be in front of the object . 
