Secrets of the Earth’s Rotation: From the Origin of the Solar System to the Tilt of the Axis

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Estimated reading time: 4 minutes

Have you ever wondered why the Earth rotates?

The Earth completes a full revolution around its axis in 24 hours, resulting in the alternation of day and night. Additionally, our planet orbits the Sun at a speed of 30 kilometres per second. However, do you know why the Earth rotates and where the strange tilt of its axis, which creates the seasons, comes from?

The reasons for these phenomena lie in the distant past, specifically the origin of the solar system

To understand the reason for Earth’s rotation on its axis, we must look back billions of years to the formation of our planetary system. It is believed that approximately 4.5 billion years ago, the Sun was a rotating cloud of gas and dust that gradually compressed due to gravity.

Within this protoplanetary disc, matter began to merge into larger clumps, which eventually formed the planets. The rotational motion of the mass was transferred to the forming celestial bodies as they slowly rotated around a common centre of mass.

Due to the conservation of momentum, the already cooled Earth ‘inherited’ this rotation. Over 4 billion years, it has taken the form of a flattened ball at the poles and has continued to rotate in this manner.

Causes of the tilt of the Earth’s axis

The primary rotation should have been much more chaotically orientated, but the collision caused the axis to tilt and stabilized the rotation.  The Earth’s axis is tilted relative to the plane of its orbit by 23.5 degrees. This tilt is believed to have been caused by a planetary collision in the Earth’s distant past.

According to one theory, a large celestial body the size of Mars collided with the young Earth, causing the tilt. This collision caused the fragments of rock from which the Moon was formed to be knocked out of their original orbit.

The impact also caused the Earth to tilt on its axis, resulting in its current 23-degree tilt and the changing of seasons. While some alternative theories suggest the influence of other planets or the Sun, the exact cause of the Earth’s tilt remains uncertain.

The uneven illumination of the planet’s surface by the Sun throughout the year is the reason for the diverse climate in different hemispheres. This is due to the tilt of the planet’s axis of rotation, which has been inherited from ancient times.

Over 4 billion years, the Earth’s rate of rotation around its axis has gradually decreased from the original 6 hours to the current 24. This is due to the gradual loss of rotational momentum caused by the Moon, tides, and other processes that act as a ‘brake’ on the Earth’s rapid rotation. In approximately half a billion years, our planet will become tidally locked with the Moon, resulting in one side of the Earth always facing the Moon. This will cause the length of a day to be equal to the length of a lunar orbit.

The slowing of axial rotation in the distant future may lead to a new ice age for mankind. This is because the reduction in angular velocity will cause the Earth to become slightly more flattened at the poles, which could have significant climate effects.

This will increase the tilt of the axis, causing a greater difference in seasonal illumination between the Northern and Southern Hemispheres. Some models predict that the Earth will experience epochs of glaciation in tens or hundreds of millions of years due to weakening of the planet’s axial rotation!

Conclusions about the causes of the Earth’s rotation:

The Earth rotates and has an axial tilt due to the laws of conservation of momentum inherited from the rotation of the protoplanetary cloud around the Sun. The axis tilt was caused by either a giant collision or gravitational disturbances. The Earth’s rotation slows down gradually due to the loss of energy caused by tidal friction from the Moon and the Sun. This means that even the basic features of our planet’s motion are connected to natural phenomena that originated in the ancient history of the solar system.