Is the Earth pear-shaped? Dehydrated earth like walnuts? Wrong, the Earth is actually more round than you think

Many enlightenment teachers have made some inaccurate metaphors or descriptions in order to facilitate children's quick understanding of things. Does this happen?

There really are, and there are many more.

wrong "general knowledge"

Take an interesting phenomenon found in the comment area today. Some people actually think that the earth is really closer to a pear shape, not a few, but a lot of people. The reason given is that the teacher has said it before, or many people around me think so: "The earth is not a true sphere, but an irregular ellipsoid with slightly flattened poles and a slightly bulging equator, more like a pear." .

Is the earth really like a pear? Are the mountains in Tuli really that high?

In order to prove this point of view, some people even came up with a so-called "dehydration map of the earth" (below), saying that the earth is actually deflated.

Is this the so-called "dehydration map of the Earth"? actually not

It is true that the poles of the earth are slightly flat and the equator is slightly bulging, but the difference is too small to be observed intuitively. Therefore, in the early years, some enlightenment teachers or programs created the so-called "pear-shaped" earth, which is actually a popular metaphor for children to easily understand that the earth is not a perfect spherical shape. Over time, it has been passed down as "general knowledge" by many people.

why the earth is not like a pear

In fact, the scientific community has never acknowledged this claim.

Because although the earth is not a perfect sphere, it is definitely not as irregular as a pear. The precise size data of the earth is there. There are so many spacecraft in the earth's orbit, which can be simulated or observed with data. In fact, compared to the pear shape, the earth, although not perfect, is still closer to a true sphere.

Earth is very round as seen from the International Space Station

In fact, although the earth is not perfect, it is still a little closer to a near-perfect sphere than a "pear", and even the earth is actually rounder than many sphere-like products we currently manufacture.

why? Let's calculate the flatness of the earth.

Earth flattening = (equatorial radius - polar radius) / equatorial radius = (6378137 meters - 6356755 meters) / 6378137 meters ≈ 0.003. This tiny flattening, not to mention visually invisible, is that many globes we make cannot be so round.

Is a dehydrated earth like a walnut?

In order to understand the concept of scale, let's do a simulation, assuming that the earth is scaled to a globe.

How deep is the deepest ocean trench if the Earth is scaled to a 1-meter-diameter globe?

The average radius of the earth is 6371KM, the highest peak Mount Everest is about 8.8KM, and the deepest trench, the Mariana Trench, is about 11km deep. It can be easily concluded that the radius of the earth is 724 times that of the highest peak and 579 times that of the deepest trench. If the earth is shrunk into a large globe with a radius of 50CM and a diameter of 1 meter. The highest mountain and deepest ocean trench on earth can be easily converted.

On this globe, the height of Mount Everest=50CM/724=0.069CM, the depth of Mariana Trench=50CM/579=0.086CM, all of which are less than 1 mm, which is the thickness of a piece of paper, and this is still the highest peak and deepest trench. With such subtle differences, there are basically no obvious three-dimensional bumps and terrain undulations that can be observed on this large globe with a diameter of 1 meter. Mountains, seas and ravines are just a thin layer on the surface of the earth.

So, is the earth like a rough walnut? Certainly not.

However, some people will take the so-called "dehydration map of the earth" and say, "Look, isn't this a walnut?"

Let's talk about the fake "Dehydrated Earth" map

This picture has been regarded by many people as a model to show that the earth will look like a shriveled walnut after the surface is dehydrated.

In fact, this is not a "dehydration map of the earth", it does not express the real topography, but a "map of the distribution of the earth's gravity field".

Schematic diagram of the distribution of the earth's gravity field

How did this picture come about?

Due to the irregularity and mobility of the mass distribution of the earth's interior, the earth's gravitational field is not a force field that changes according to simple laws. Therefore, according to the data and trend of the earth's gravity field, scientists convert it into the height of the geoid, and obtain a simulated earth image that is very close to a spheroid to visually display the distribution and movement of the gravity field. And in order to make the display more obvious, the undulating effect is deliberately magnified dozens of times, looking like a walnut.

So, there is this picture, but it's not a simulated picture of a dehydrated Earth.

Let's forcibly make a "walnut map" after the earth is dehydrated

At this point, everyone should understand. In fact, the earth is not as rough and round as many people imagine. The real earth may be round and smoother than many spheres you see in daily life.

However, it is not impossible to make the dehydrated earth look like a "walnut".

The size of the earth's radius is unchanged, and the effect diagram after the terrain height difference is enlarged by 500 times alone

Once a netizen modeled in the computer, kept the size of the earth unchanged, and enlarged the terrain height fluctuation difference in the stereo image by 500 times, and finally obtained the desired "walnut". Note that this is the effect only after the size of the earth remains unchanged and the height difference of the terrain is simply enlarged to an exaggerated 500 times! Making "walnuts" in order to make "walnuts" is just for fun.

Another misunderstood "general knowledge"

Another netizen said: "Isn't the earth 70% ocean? Then the amount of water on the earth should be very large. If you remove the water, wouldn't the earth be obviously shriveled? And the earth should be called a "water polo"!"

Hearing this sentence, I was moved and speechless. In fact, the accurate statement is that more than 70% of the earth's surface is covered by oceans, not that 70% of the earth is oceans. Surface area and volume are two concepts.

Schematic diagram: Most of the earth's surface is covered by oceans, but it does not mean that the earth is full of water

The earth is a sphere with an average radius of 6,371 kilometers, and the average depth of the oceans is around 3.5 kilometers.

Of course, for a human height of more than 1 meter, the average depth of the ocean is 3500 meters; but for the average radius of the earth 6371 kilometers, the average depth of the ocean about 3.5 kilometers is equivalent to plating the earth. It's just a film, and it's a very thin film.

Therefore, the area does not represent the amount of water, and it cannot be guessed by the mind set. As long as you calculate the data, you will understand. The earth is called the earth, and there is nothing wrong with it.

The dauntingly deep ocean is only a thin layer compared to the scale of the earth

So stop thinking that the earth is shaped like a pear, that the earth is dehydrated like a walnut, and that the earth is a big water polo filled with water.

In fact, the ocean can only be regarded as a thin layer of the earth's surface. Even if the ocean water already accounts for about 97% of the earth's total water volume, all these water volumes together can only be regarded as a glass of water for Mother Earth to drink.

Follow @ Brain Hole Science Club There are popular popular science articles that you love to read.