The Earth rotates on itself due to its initial rotation movement acquired during its formation billions of years ago. This rotational movement is preserved due to the conservation of the angular momentum of the Earth-Sun system.
About 4.6 billion years ago, our solar system formed from a massive cloud of gas and dust. Under the influence of gravity, this material began to swirl slowly, forming a rotating flat disk known as the protoplanetary disk. It was within this disk that the Earth and other planets began to take shape. As pieces of material came closer together and gathered to form our planet, this initial rotation intensified, much like when a figure skater speeds up by pulling her arms close to her body. The result: the Earth started to rotate on its axis from the very beginning, a movement it still maintains today.
Gravity is a fundamental force that is widespread throughout the universe, attracting massive objects to each other. It acts like a kind of cosmic glue, bringing together gas and dust to form stars, planets, and entire galaxies. It is thanks to this force that the original clouds of matter collapsed in on themselves while spinning, thus giving rise to all sorts of rotating celestial objects. Without gravity, there would be no concentration of matter, and therefore no spontaneous rotation. Our Earth itself comes from a gradual accumulation of matter, drawn in by this invisible force that slowly shaped it into a spherical form and gave it rotational movement. The gravity of the Sun then keeps our planet in orbit around it while influencing its axis of rotation. In short, without gravity, our planet would likely be a pile of scattered dust without coherent movement.
The angular momentum is simply a physical quantity that relates to the amount of rotation of an object in motion around an axis. It's a bit like when you watch a figure skater spinning on the spot, arms outstretched: if they pull their arms closer to their body, they will immediately spin faster. Why? Because angular momentum remains constant. Our planet operates in the same way. Initially, the Earth was a large cloud of space dust that gradually contracted. As it concentrated and reduced its radius, its rotation speed increased to conserve that famous angular momentum. This is also the same principle that keeps the Earth spinning today: no force has come to stop its rotation since then, so it retains its precious initial momentum.
Our planet is not alone: the Moon plays a huge role in the way it spins on its axis. The gravitational pull of the Moon acts on the Earth's oceans by creating those famous tides. This interaction serves as a kind of natural "brake" on the Earth's rotation. As a result, the Earth is gradually slowing down — a few hundredths of a second per century, nothing perceptible on a human scale. At the same time, the Moon is slowly drifting away, about 3.8 cm per year. This long-term interplay between the Earth and the Moon slowly changes the rotation speed of our planet.
Some major astronomical events, such as major meteorite impacts or gravitational interactions with other celestial bodies, can disrupt the Earth's rotation. For example, a giant earthquake or the impact of a large asteroid releases so much energy that it subtly alters the speed or axis of rotation. Even if it's slight, on an astronomical scale, these variations matter a lot. Some long-term interactions, like the gravitational pull of the Sun or the Moon, also create cumulative effects that gradually slow down the Earth's rotation. Such events do not abruptly stop our rotation but clearly influence its rhythm and orientation over millions of years.
The Earth's rotation causes a slight deformation of our planet, giving it a shape that is slightly flattened at the poles and bulging at the equator. As a result, the diameter at the equator exceeds that measured at the poles by about 43 kilometers!
Due to the gradual slowing of the Earth's rotation caused by lunar tides, additional seconds, known as 'leap seconds', are occasionally added to our clocks to stay synchronized with the actual rotation of the Earth.
On Venus, a day lasts about 243 Earth days, which means that its rotation on its axis is slower than its revolution around the Sun. On this neighboring planet, it might be possible to walk faster than the planet's own rotation!
The direction of the Earth's rotation, from west to east, explains why we see the Sun rise in the east and set in the west. On Uranus, however, the extreme tilt of its axis causes days and nights that can last up to 42 Earth years.
Yes, the Earth's rotation speed changes slightly over time, mainly due to the tidal effects caused by the Moon. These interactions gradually slow down the Earth's rotation, lengthening the duration of days by about two milliseconds every hundred years.
If the Earth were to suddenly stop rotating, it would cause a major global catastrophe. We would be propelled eastward at high speed due to inertia; the oceans would generate immense tsunamis, and the climate would undergo drastic changes. However, such a scenario remains completely hypothetical and practically impossible.
Yes, all the planets in the solar system rotate on their axes, but at different speeds. For example, Jupiter completes a full rotation in just about 9 hours and 55 minutes, while Venus takes about 243 Earth days and rotates in the opposite direction, which is called retrograde rotation.
We do not feel the Earth's rotation because its speed remains constant, without sudden variations. Moreover, our bodies and everything around us, including the atmosphere, rotate at the same speed, which gives us the sensation of relative stillness.
The Earth rotates on its axis at an average speed of about 1670 kilometers per hour at the equator. The closer one gets to the poles, the more this speed decreases, becoming almost zero at the poles themselves.
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