[ICR Creation Online] Almost all bodies in the Solar System orbit and rotate in the same direction, although several exceptions exist. This predominant direction is calledprograde (if you were to look down on the Solar System from the Sun's North Pole, it would be counter-clockwise), and the opposite direction is called retrograde. Some young-Earth advocates claim that, if the Solar System really condensed from a dust cloud as is generally accepted, then all rotations should be prograde. These people claim that the exceptions to the predominant direction show that the prevailing theories of Solar System formation are invalid. Others assert that, since rotation states are thought to be largely influenced by impacts, rotation states should be randomly distributed (approximately half prograde and half retrograde). This second group claims that the existence of a predominant direction of rotation argues against the prevailing theories. Obviously, these two groups are making similar claims, but their justifications for saying so oppose each other.

 

It is most likely that the second group is at least partly correct: rotation states are greatly influenced by impacts, and we would expect them to be close to random. However, this is not known for certain. It is also important not to be misled by planets which have definitely not had their rotations affected by impacts. Two planets (Jupiter and Saturn) are almost entirely gas, and thus impacts would have very little effect on their rotation. Therefore it is no surprise that Jupiter and Saturn have prograde rotation. A third planet, Pluto, has a rotation state that is the result of tidal resonance with its moon Charon. Whatever Pluto's original rotation state may have been, it would have been inevitably dragged by Charon into its present state, in which it always keeps the same face towards Charon (similarly, almost all moons in the Solar System have had their rotation states defined by tidal forces, not by impacts, which explains why they are predominantly prograde). Discounting these three, we are left with 6 planets, two of which (Venus and Uranus) have retrograde rotation. Therefore, the claims of the second above-mentioned group (that rotations should be random) are most likely true, while their objections (that there is a predominant direction) is easily explained by statistical fluctuation and the influence of tides. Also, the objections of the first group (that all rotations should be in the same direction) are answered by considering the influence of large impacts and tides during the early history of the Solar System.