Why Earth Rotates?

Why Earth Rotates?

The rotation theory of the universe suggests that if the sun shall rise tomorrow, it may just be a fraction late.

Since the Earth came into being some 4.6 billion years ago, every day it spins once around its axis just like the rising and setting of the Sun. This will continue to happen till the point when our world comes to its end. Evidently, this refers to a time when the Sun will swallow our planet and swell into a red giant star. But why does the Earth rotate?

According to Space.com, a spinning disk of gas and dust that swirled around the infantile Sun provided the environment for the bits of dust and rock to stick together and form the Earth. Smadar Naoz, an Astrophysicist at the University of California, told the world that the space rocks continually collided with the nascent planet as the Earth grew. The resultant forces, generated due to these collisions, induced its spin. Coincidentally, debris in the premature solar system rotated around the sun in approximately the same direction. These collisions also spun everything else in the solar system in the same direction.

Another question that arises here is that what made the solar system spin in the first place? The cloud of dust and gas collapsed due to its own weight when the sun and the solar system formed. The gas mostly condensed becoming the sun and the remaining material became the surrounding, planet-forming disk. Before it collapsed, the gas molecules and dust particles were moving erratically, however at a pivotal point, some gas and dust chanced to travel in a singular direction, thus setting the spin in motion. The collapse of the gas cloud triggered an acceleration in cloud’s rotation speed like figure skater tucking their arms and legs in to spin faster.

Once celestial objects start rotating in space they usually continue to do so, because there is very little matter to slow it down. The rotating infantile solar system had lots of angular momentum, the tendency of an object to keep spinning. As a result, all the planets gyrated in the same direction when the solar system formed. Currently, however, there are planets that have rotations that are at odds with the direction of spin of the Earth.

The rotation of Venus is in the opposite direction to that of Earth, and the spin axis of Uranus is inclined 90 degrees. Scientists mystified as to how these planets managed this, but some theories exist. Perhaps Venus, collided with something thus causing its rotation to flip. It is equally possible that Venus began rotating the same way as other planets. But, the sun’s gravitational pull on Venus’ thick clouds, combined with friction between the planet’s core and mantle, caused its rotational direction to change. The latter being a sentiment shared by a study published in Nature in 2001 suggesting that gravitational interactions with the sun and other factors might have caused Venus’ spin to slow down and reverse.

According to a Scientific American report, Uranus may have collided in one colossal crash with a massive rock or perhaps encountered two different objects knocking it off kilter. Despite these disturbances, everything in space rotates in one direction or another. All the celestial bodies like asteroids, stars, and galaxies rotate. Naoz mentioned that in the following words:

“Rotating is a fundamental behavior of objects in the universe.”

According to NASA, the solar system takes 230 million years to complete one circuit around the Milky Way. Pulsars are one of the fastest things in the universe. These corpses of massive stars are dense, whirling objects and some of them have diameters about the size of cities. They can spin hundreds of times per second. Found in 2006, Terzan 5ad, the fastest known pulsar rotates 716 times per second.

Black holes are even faster when it comes to spinning. An astrophysical study, in 2006, found a black hole named GRS 1915+105, which may be gyrating between 920 and 1,150 times per second. Having said that, things also slow down. Naoz referred to that by saying,

“When the sun formed, every four days it spun once around its axis, however now it takes about 25 days to spin once. Its magnetic field interacts with solar wind slowing its rotation.

Deceleration even affects Earth’s rotation. The moon’s gravity pulls on Earth such that it ever so slightly slows it down. A 2016 analysis of ancient eclipses showed that Earth’s rotation slowed by about 6 hours over the last 2,740 years. That comes out to be just 1.78 milliseconds over a century.

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