You may think that people have always somewhat known that the earth spins. After all, people have been using stars to navigate and tell the time for thousands of years, and people have seen the plants in our solar system move across the sky for just as long.
But many ancient cultures believe that the stars and plants roasted around fixed earth and that the earth itself did not move or rotate at all. In fact, people only began considering that the earth was the one moving just under 500 years ago.
The Ancient Greeks
Ancient Greek philosophers held opposing viewpoints on why the planets moved across the sky, and their theories influenced Western Civilization's worldview until the sixteenth century Scientific Revolution.
One group believed the planets orbited the Sun, which we now know today is true. But Aristotle's had different beliefs, and these are the ones that prevailed the most. Aristotle believed that the planets and the Sun orbited the earth. He saw no signs that the earth was moving.
He believed that if it was, there would be a constant breeze felt on the earth from the moving motion, and in a test, he threw a ball straight up into the air, which did not fall behind the thrower as Aristotle predicted if the Earth were moving.
To Aristotle, this meant that the earth had to be stationary whole the planets, sun, and stars roasted around it.
For nearly 1,000 years, Aristotle’s view of stationary earth at the center of a spinning universe was the idea that dominated natural philosophy or science. Nothing changed and hardly anyone challenged the idea until Nicolaus Copernicus came along.
A Polish clergyman named Nicolaus Copernicus proposed in 1515 that the Earth was a planet like Venus or Saturn and that all planets rotated around the Sun. Because he was frightened of criticism, he did not publish his theory until 1543, shortly before his death.
Some academics say Copernicus was more worried about scientific errors in his theories than with the Church's issues about the idea, but we will never know why he didn’t publish it for so long. Still, he was the first recorded person to put forward the idea that the earth spins.
The concept had few supporters, but those who believed it were accused of heresy for a time. An Italian scientist, Giordano Bruno, was burned at the stake for teaching Copernicus' heliocentric theory of the Universe, among other heretical beliefs.
The evidence for this theory kept growing stronger over time though, despite what the church said. Galileo discovered moons orbiting Jupiter for the first time in human history when he pointed his telescope towards the night sky in 1610. If Aristotle was true about everything orbiting Earth, these moons would not exist.
Venus' phases were also spotted by Galileo, which confirmed the planet's orbit around the Sun. While Galileo did not meet the same fate as Bruno, the Roman Inquisition found him guilty of heresy and placed him under house arrest for life.
At around the same time as this, Johannes Kepler, a German mathematician, published a set of rules to describe the orbits of the planets around the Sun. Under Copernican theory, the mathematical formula, which is still in use today, provided precise predictions of the planets' movement.
When Isaac Newton struck the final nail in the coffin of the Aristotelian, geocentric view of the Universe in 1687, the old theory that the earth is still was finally put to rest. Based on Kepler's theories, Newton explained why the planets orbited the Sun in the way they did and named the force that kept them in check gravity.
How Fast Does The Earth Spin?
Although we can’t feel it, the earth is spinning incredibly quickly. But depending on where you are standing on the earth.
The Earth's spin remains constant, however, the speed varies depending on your latitude. Here's an illustration. According to NASA, the circumference (the distance around the biggest section of the Earth) is approximately 24,898 miles (40,070 kilometers).
This region is also known as the equator. You divide the circumference by the length of the day, which is 24 hours long. At the equator, this results in a speed of around 1,037 mph (1,670 km/h).
At other latitudes, however, you won't be moving as quickly. We can determine the speed by using the cosine (a trigonometric function) of the latitude if we move halfway up the globe to 45 degrees in latitude (either north or south).
If you don't know how to compute it, a good scientific calculator should have a cosine function. Because the cosine of 45 is 0.707, the spin speed at 45 degrees is around 0.707 x 1037 = 733 miles per hour (1,180 kilometers per hour).
As you travel further north or south, the speed falls even more. When you reach the North or South poles, your spin is extremely slow – it takes an entire day to spin in place.
Will The Earth Ever Stop Spinning?
The earth is not going to stop naturally spinning for billions of years. This is very good news as if the earth was to stop spinning we probably would not survive as the earth would no longer be inhabitable.
But what would happen if the earth was to suddenly stop spinning?
It wouldn’t be good for us that’s for sure. If the earth arrived at a hard stop over the course of 60 seconds, things like the oceans and the atmosphere would continue to spin, while everything else would be wiped out instantly. If the earth suddenly stopped rotating it would completely destroy everything on the surface of the earth.