# Why does Venus rotate differently from other planets?

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If you are in space, at a point exactly above the North Pole of the Earth, you can see that the Earth rotates on its axis counterclockwise. Likewise, if we look at the rotation of Mercury, Mars, Jupiter, Saturn or Neptune from a point located above their north poles, we will also see the same picture: the rotation will be counterclockwise.

But with Venus, everything is different. Venus rotates clockwise! Why is that? Now we can hardly establish this with any high degree of certainty. However, we can make reasonable assumptions based on our understanding of the laws of physics.

All of our solar system formation models predict that all planets should rotate:

The first two predictions are perfect, but the third is a problem in the case of Venus.

In modern astrophysics, there are two main theories that explain this atypical rotation of Venus. Both of them say that initially Venus rotated in the same way as the rest of the planets, but then changed the direction of rotation.

In the first theory, the change in the direction of rotation of Venus is explained solely by the influence of the tidal forces of the Sun. Tidal forces arise from the fact that the sun’s gravitational field is not uniform. The closer to the Sun — the stronger the attraction, the further — the weaker. Therefore, the attraction of the Sun to the side of Venus facing it is stronger than to the opposite.

The difference in these forces can be significant and the long-term effect of such forces leads to the fact that the planet may find itself in a tidal capture near its star, i.e. will always face the star with one side. So, for example, the Moon is in tidal capture of the Earth.

It is believed that the tidal forces of the Sun could first slow down the rotation of Venus around its axis, and then spin in the opposite direction. There are mathematical models that show the theoretical possibility of such a development of events.

The second hypothesis is called the great collision hypothesis. It consists in the fact that in the past, Venus revolved around its axis as well as the rest of the planets.

Then it collided with another large celestial body, as a result of which it spun in the opposite direction. According to the calculations of astrophysicists, the object should have a mass comparable to the mass of Venus itself.

There are also other hypotheses, for example, the American astrophysicist Thomas van Flandern was able to calculate such a scenario in which Mercury was in the past a satellite of Venus, then left Venus, as a result of which Venus changed its direction of rotation, and Mercury entered the orbit where it is now.

For all the amusement of this hypothesis, it is not supported by data on the formation, structure and composition of Mercury, which at the time when van Flandern made his calculations were simply not known.

Correia, Alexandre C. M.; Laskar, Jacques; De Surgy, Olivier Néron.Long-Term Evolution of the Spin of Venus,

Shapiro, I. I.; Campbell, D. B.; De Campli, W. M.

Thomas C. Van Flandern, Robert S. Harrington

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