Some of the earliest astronomers in recorded history proposed that we live in a geocentric universe in which Earth lies at the center of everything. According to them, the sun rotated around us, which caused sunrises and sunsets, same for the movements of the moon and the planets.
But even then, there were certain things that didn’t exactly line up with these theories. For example, sometimes, a planet would back up in the sky before resuming its forward motion.
Normally, humans aren’t thrown off the moving Earth because gravity is holding us down. However, because we are rotating with the Earth, a ‘centrifugal force’ pushes us outwards from the centre of the planet. If this centrifugal force were bigger than the force of gravity, then we would be thrown into space.
The strength of the centrifugal force depends on where you are. It is greatest at the equator and zero at the Earth’s poles. We can calculate how fast the Earth would need to spin to balance the force of gravity (this is known as the ‘escape velocity’). It works out at about 28,437km/h (17,670mph). The Earth would have to spin once every 84 minutes to achieve that speed at the equator, or about 17 times faster than it actually spins.
First, we have to figure out how far Earth travels. Earth takes about 365 days to orbit the sun. The orbit is an ellipse, but to make the math simpler, let’s say it’s a circle. So, the distance from Earth to the sun is called an astronomical unit, which is 92,955,807 miles (149,597,870 kilometers), according to the International Astronomers Union. So in one year, Earth travels about 584 million miles (940 million km). We learn that the earth is moving about our sun in a very nearly circular orbit. It covers this route at a speed of nearly 30 kilometers per second, or 67,000 miles per hour.
Speed of Earth
Since speed is equal to the distance traveled over the time taken, Earth’s speed is calculated by dividing 584 million miles (940 million km) by 365.25 days and dividing that result by 24 hours to get miles per hour or km per hour. So, Earth travels about 1.6 million miles (2.6 million km) a day, or 66,627 mph (107,226 km/h).
In addition, our solar system, Earth and all whirls around the center of our galaxy moving at some 220 kilometers per second, or 490,000 miles per hour. As we consider increasingly large size scales, the speeds involved become absolutely huge!
The galaxies in our neighborhood are also rushing at a speed of nearly 1,000 kilometers per second towards a structure called the Great Attractor, a region of space roughly 150 million light-years (one light year is about six trillion miles) away from us.
In 1989, the COBE satellite was placed in orbit about the earth to measure the long-diluted radiation echo of the birth of our universe. This radiation, which remains from the immensely hot fireball that was our early universe, is known as the cosmic microwave background radiation (CBR).
The earth is moving with respect to the CBR at a speed of 390 kilometers per second. We can also specify the direction relative to the CBR. It is more fun, though, to look up into the night sky and find the constellation known as Leo (the Lion).
What if Earth were to stop spinning?
Back to the no-spin scenario for a second: There would be some other weird effects if the Earth stopped spinning completely, NASA said. For one, the magnetic field would presumably disappear because it is thought to be generated in part by a spin. Then Earth would be naked against the fury of the sun. Every time it sent a coronal mass ejection (charged particles) toward Earth, it would hit the surface and bathe everything in radiation. “This is a significant biohazard,” NASA said.
Each side of the planet would get six months of continuous sunlight and six months of darkness. Without the centrifugal force of the spin, the oceans would gradually move towards the poles, creating a huge supercontinent across the equator.