Which direction do Earth and other planets rotate?

Earth spins in the same direction as the sun, but this is not true for all planets in the solar system. The spin of the planets is connected to the formation of the solar system billions of years ago.

The solar system began as a dense cloud of gas and dust which eventually collapsed on itself, forming the sun at its center. The surrounding gas formed planets, and the initial spin of this cloud is still evident today. As objects shrink in size, they spin faster due to conservation of angular momentum. This is similar to a figure skater pulling in their arms while twirling. The sun represents the center of gravity, while the planets and moons can be compared to the skater's arms and legs. Consequently, the planets and the sun continue to spin.

Considering the direction of rotation, astronomers use a reference point, which in the case of the solar system is the counterclockwise spinning sun. Most of the planets, including Earth, Mercury, Mars, Jupiter, Saturn, and Neptune, also rotate counterclockwise. However, there are exceptions.

Venus, for instance, spins clockwise, causing the sun to rise from the west instead of the east. Scientists previously speculated that a massive object collision may have caused this reverse spin. However, it is now understood that Venus' thick atmosphere plays a crucial role. With an atmosphere about 90 times thicker than Earth's, the pressure created beneath it causes friction with the planet's surface and likely slows down its rotation over time. Additionally, a 2020 study suggested that the sun's heat generates atmospheric tides that move in the same direction as Venus' spin, contributing to its clockwise rotation.

Further out, Uranus presents an eccentric case as it spins on its side. Astronomers speculate that a significant impact early in its history was responsible for this unusual rotation. There is another theory proposing that Uranus had a massive moon whose gravitational influence tilted the planet before colliding with it, setting Uranus on its current tilted state. As a result of this extreme tilt, Uranus experiences dramatic seasonal changes, with winters lasting approximately 21 Earth years, in contrast to Earth's milder seasonal variations caused by its 23-degree tilt.

Understanding the rotation of planets and their unique characteristics provides valuable insights into the diverse formations and dynamics of the solar system.