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A new study has discovered a powerful force that is now driving evolution on Earth.

How fast does the Earth spin

As people on earth, it is easy to believe that we are standing still. After all, we cannot feel any movement around us. However, when you look up at the sky, you can see evidence that we are moving. What is the speed at which the earth revolves around the sun?

Some of the earliest astronomers suggested that we live in a geocentric universe, which means that the earth is the centre of everything. They say that the sun revolves around us, which leads to sunrises and sunsets—the same goes for the movement of the moon and planets. But some things are not in line with this vision. Sometimes, a planet will retreat in the sky before resuming forward motion.

We now know that this kind of motion-known as retrograde motion occurs when the earth is chasing another planet in its orbit. For example, the orbit of Mars is farther from the sun than the earth. At some point in the respective orbits of Earth and Mars, we caught up with the red planet and passed it. When we passed it, the planet moved backwards in the sky. Then it moved forward again after we passed.

Another evidence of a solar system cantered on the sun comes from observing parallax, or obvious changes in the relative positions of stars. To give a simple parallax example, place your index finger in front of your face and keep it one arm length with your arm. Look only with your left eye and close your right eye. Then close your right eye and look at the fingers with your left hand. The obvious position of the finger changes. That's because your left and right eyes look at your fingers at slightly different angles.

When we look at the stars, the same thing happens on Earth. It takes about 365 days for us to orbit the sun. If we look at a star in summer (closer to us) and look at it in winter, its obvious position in the sky will change because of our different points in the orbit. We look at this star from different angles. Through some simple calculations, using parallax, we can also calculate the distance to that star.

How fast does the Earth spin?

The rotation of the earth is constant, but the speed depends on the latitude where you are. This is an example. According to NASA, the circumference (the distance around the largest part of the earth) is approximately 24,898 miles (40,070 kilometres). (This area is also called the equator.) If you estimate that a day is 24 hours long, divide the perimeter by the length of the day. This produces a speed of approximately 1,037 mph (1,670 km/h) at the equator. [How fast does the speed of light travel? ]

However, you will not move that fast in other latitudes. If we move half of the earth to 45 degrees latitude (north or south), you can use the cosine of latitude (trigonometric function) to calculate the speed. If you don't know how to calculate, a good scientific calculator should have a usable cosine function. The cosine of 45 is 0.707, so the rotational speed of 45 degrees is approximately 0.707 x 1037 = 733 mph (1,180 km/h). As you go further north or south, the speed will decrease even more. When you reach the North Pole or the South Pole, your rotation is really slow-it takes a whole day to get in place.

Space agencies like to use the rotation of the earth. For example, if they send humans to the International Space Station, the preferred location is close to the equator. This is why cargo missions to the International Space Station, for example, were launched from Florida. By doing this and launching in the same direction as the Earth’s rotation, rockets can gain speed to help them fly into space.

How fast does the earth revolve around the sun?

Of course, the rotation of the earth is not our only movement in space. According to reports, our orbital speed around the sun is about 67,000 mph (107,000 km/h). We can use basic geometry to calculate.

First, we must figure out how far the earth has travelled. It takes about 365 days for the earth to revolve around the sun. The orbit is an ellipse, but to make mathematics easier, we assume it is a circle. Therefore, the orbit of the earth is the circumference of a circle. According to data from the International Union of Astronomers, the distance from the earth to the sun (called astronomical units) is 92,955,807 miles (149,597,870 kilometres). That is the radius (r). The circumference of a circle is equal to 2 x π x r. So in one year, Earth travels about 584 million miles (940 million km).

Since speed is equal to the distance travelled in the time taken, the speed of the earth is calculated by dividing 584 million miles (940 million kilometres) by 365.25 days, and then dividing the result by 24 hours to get miles/hour or kilometres/hour. Therefore, the earth travels about 1.6 million miles (2.6 million kilometres) per day, or 66,627 miles per hour (107,226 kilometres per hour).

What about the movement of the sun and the milky way galaxy?

The sun has its own orbit in the galaxy. The sun is about 25,000 light-years from the centre of the Milky Way, and the Milky Way is at least 100,000 light-years wide. We are considered to be about halfway from the centre. The sun and solar system appear to move at a speed of 200 kilometres per second, or an average speed of 448,000 mph (720,000 km/h). Even at such a fast speed, it takes about 230 million years for the solar system to orbit the Milky Way.

The Milky Way also moves in space relative to other galaxies. In about 4 billion years, the Milky Way will collide with its nearest neighbour, the Andromeda Galaxy. The two are colliding with each other at a speed of about 70 miles per second (112 kilometres per second). Therefore, everything in the universe is in motion.

What if the Earth suddenly stopped spinning?

You can't be thrown into space now, because the gravity of the earth is so powerful compared to its rotation. (The latter kind of motion is called centripetal acceleration.) At the strongest point on the equator, centripetal acceleration only cancels about 0.3% of the earth's gravity. In other words, you won't even notice it, although your weight on the equator will be slightly lighter than at the poles.

NASA said that in the next billions of years, the possibility of the Earth stopping its rotation is almost zero. However, in theory, if the earth suddenly stops moving, it will have a terrible effect. The atmosphere will still move at the original speed of the earth's rotation. This means that everything will disappear from the land, including people, buildings and even trees, topsoil and rocks.

What if the process was more gradual? NASA said this is more likely to happen in billions of years because the sun and moon are pulling the earth's rotation. This will provide sufficient time for humans, animals and plants to adapt to this change. According to the laws of physics, the slowest rotation speed of the earth is 1 revolution every 365 days. This situation is called sun synchronization and will force one side of our planet to always face the sun, and the other side to always face away from the sun. In contrast: the Earth’s moon is already rotating in sync with the Earth, one side of the moon always faces us, and the other side is opposite to us.

But back to the non-rotating scenario: if the earth stops rotating completely, there will be other strange effects. On the one hand, the magnetic field may disappear because it is thought to be partly generated by spin. We will lose the colourful aurora, and the Van Allen radiation belt that surrounds the earth may also disappear. Then the earth will confront the sun's fury nakedly. Every time it sends a coronal mass ejection (charged particle) to the earth, it hits the surface of the earth and bathes everything in radiation. This is a major biological hazard.

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