A compilation of unsettling trivia and fun facts about Earth

The Earth is not a perfect sphere.

When we think of Earth’s shape, we often picture a beautiful circle—the way it’s drawn in illustrations—so most people have that impression.

However, while Earth is round, it isn’t a perfect sphere.

Strictly speaking, it’s an “oblate spheroid,” bulging at the equator and flattened at the North and South Poles.

The reason is Earth’s rotation: the centrifugal force causes the equatorial region to bulge.

It’s a fact that helps us grasp how fast the Earth spins and what kinds of forces that rotation produces.

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The mass extinctions that occurred on Earth are called the “Big Five.”

According to studies of fossils, life is said to have originated on Earth 3.5 billion years ago.

Since the emergence of life, it is thought that there have been five mass extinctions on Earth, collectively called the Big Five.

In the end-Permian period, about 251 million years ago—also known as the largest extinction event in Earth’s history—it is believed that 90 to 95% of species went extinct.

Early reptiles, amphibians, insects, and plants are said to have lived then.

Dinosaurs and birds are also said to have lived as well.

There are several proposed reasons for the extinctions; one is that evidence of a global retreat of coastlines suggests the food chain collapsed.

Other factors include large-scale volcanic eruptions and changes in the composition of the atmosphere caused by the metabolism of proliferating bacteria.

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The Earth’s rotation is slowing down.

The Earth takes 24 hours to complete one rotation on its axis.

However, Earth’s rotation has been slowing down year by year.

Because of the Moon’s gravitational pull, we experience ocean tides.

When tides cause seawater to move, friction with the seafloor occurs at the same time, which slows Earth’s rotation.

Incidentally, when Earth formed 4.6 billion years ago, a day lasted about 5 hours.

It is thought that over a very long time, the rotation has gradually slowed.

In the same way, Earth’s rotation is still slowing today.

As the rotation slows, the length of a day increases—by about 2 milliseconds per century, 1 second every 50,000 years, and 1 hour every 180 million years.

In the distant future, calculations suggest that a day would become 25 hours long.

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The Earth rotates at about 1,700 kilometers per hour.

The Sun’s position in the sky changes and a day passes because the Earth is rotating.

That rotation happens at an astonishing speed of about 1,700 kilometers per hour.

You can infer this from the distance around the Earth and the fact that it returns to the same place in one day, and it’s striking that we move this far without feeling any centrifugal force.

It’s also curious that the speed is zero at the North and South Poles and increases toward the equator, even though we don’t feel the speed at all.

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The side of the Moon visible from Earth is always the same.

It seems that around the world, people see different shapes on the Moon’s surface—like a rabbit, a long-haired woman, or a crab.

There are many ways to see it, but what’s common is that they’re all looking at the same side of the Moon.

From Earth, we can only observe one face of the Moon.

While the Moon makes one revolution around the Earth, it also rotates once on its axis, keeping the same side facing the Earth.

That’s why we always see the same lunar face from Earth.

Incidentally, if you look at Earth from the Moon, the parts illuminated by the Sun appear bright.

Depending on the positions of the Moon, the Sun, and the Earth, it can appear as a half-moon or a crescent shape.

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