http://www.nytimes.com/2016/10/18/science/planets-spinning-the-wrong-way.html 2016-10-17 20:38:53 Planets Spinning the ‘Wrong’ Way There are theories, but no certainty, for why Venus rotates clockwise. In the solar system, only Venus and Uranus do so. === Q. I read that A. The rotation of An explanation for the backward, or retrograde, rotation is not certain. A long-held theory is that Venus once rotated as the other planets do, but was struck billions of years ago by a planet-size object. The impact and its aftermath caused the rotation to change directions or flipped the planetary axis. Another theory is that tidal effects from core-mantle friction and a thick atmosphere might have accounted for the change in direction. A more recent idea,