By: Silas Laycock
GLOBE (a globe) was the first item I bought with my own money.
I was maybe 5 years old then and I was so excited to bring him home. As I soon found out, you can rotate it in the direction the earth actually rotates.
Also read: What Is Earth’s Rotation and Its Impact on Everyday Life?
There is an imaginary line between the North Pole and the South Pole. We call this the axis of rotation. For Earth, the axis of rotation points toward a bright star, Polaris, which is visible on clear nights in the Northern Hemisphere.
If you want to know the direction of rotation of a globe, make a “thumbs up” sign with your right hand. Think of your thumb as the Earth’s axis of rotation, pointing to the North Pole.
Your fingers will naturally curl around your hand, and the direction those fingers will point is the direction the Earth rotates.
Every 24 hours, the Earth makes a full rotation, rotating from west to east, which is why the sun rises in the east and sets in the west and the stars at night appear to move across the sky.
To understand why this is the case, let’s see what we can learn from other objects in space.
Everything is spinning
The sun also rotates. In fact, the Sun rotates in the same direction as the Earth.
Not only that, the Earth also orbits the Sun in the same direction, as do all the other planets and more than a million asteroids and dwarf planets.
Most also rotate in the same direction. Jupiter and Saturn rotate slightly faster than Earth, taking only about 10 hours to rotate.
Also read: Earth’s Rotation: Definition and Impact
Saturn’s rotation is slightly tilted so we can see how the appearance of the rings changes over time.
There are two interesting exceptions: Uranus appears to have reversed its position. No one knows exactly how. Maybe it collided with another planet.
Venus is also strange – it rotates backwards. We don’t know for sure whether Venus formed that way or fell.
Most scientists now think that its rotation has been reversed over time by tidal forces involving the Sun and Venus’ thick atmosphere.
All of which makes astronomers like me wonder: Is there something about how the solar system formed so that it “spins in the opposite direction?”
The birth of a star
NASA, ESA, D. Golimowski (Johns Hopkins University)
Beta Pictoris image taken from the Hubble Telescope.
For further clues we can look at young stars that have recently formed their planetary systems.
Also read: Earth’s Rotation in 2021 Is Called Slowing Down, What’s Happening?
One of the famous is Beta Pictoris. This star is surrounded by a thin disk of dust, gas, and small objects called planetesimals; The size ranges from a grain of sand to a rock and can even be as big as a mountain.
Astronomers believe the disc was formed from material left over when stars were born
Every star is born from a cloud of gas and dust that moves through space and is surrounded by similar clouds. The gravitational force causes these clouds to attract each other when they pass each other so that the clouds rotate slowly.
Even when one of these clouds collapses and forms a star, these clouds keep spinning.
Stars form, rotating amidst a flat, rotating pancake of gas and dust called the protoplanetary disk. Everything – stars, gas and dust – revolves in the same direction.
Astronomers suspect that our Solar System is very similar to Beta Pictoris in its early days.
We expect that inside the disk, gas and dust can stick together in a process called “acretion.” As the baby planet begins to grow, it will become heavier and its gravity will attract even more small pieces.
When a baby planet is massive enough, gravity will begin to crush it and make it more dense.
Also read: The planet with the fastest rotation, a day there is less than 10 hours
Therefore, like an ice skater pulling her arm to spin, the planet rotates faster. The increased pressure in the core causes the core to melt.
The denser matter would sink into the core and the lighter matter would float to the planet’s surface. Finally, we get a planet with an iron core surrounded by rock and possibly water and ice on the outside.
That’s what we see in our solar system.
What if the Earth doesn’t rotate??
The rotation of the Earth is very important for life. The rotation of the Earth causes day and night.
The rotation of the Earth is also important for the ebb and flow of sea water. Without the daily ebb and flow of water, it is likely that life would never have emerged from the sea onto land.
So astronomers believe that the Earth is rotating because the entire solar system was already rotating when the Earth was formed – but there are still many questions about how the planet’s spin changed over time and how spin affected the evolution of life.
With more than 5,000 planets that have been discovered outside the solar system, scientists in the future will be busy exploring.
Also read: Researchers find reasons for the odd rotation of the planet Venus
Silas Laycock
Professor of Astronomy, UMass Lowell
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2023-08-19 12:33:00
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