Earth has more than 8,000 meters high mountains

The Earth is round, this is a scientific common sense known to modern mankind, so how round is the Earth in the end? The answer given by scientists is that the Earth is very round and can be said to be a near-perfect sphere.

This will inevitably give rise to some doubts, because on the surface of the Earth there are great ups and downs, from high, the Earth has more than 8,000 meters high mountains, to low, the Earth has more than 10,000 meters deep trench, in that case, why scientists still say that the Earth is very round?

A wrong view

There is a view that the reason why the Earth looks round, should be the role of the Earth's oceans, simply put, a large amount of seawater will be the surface of the Earth's undulations "filled in" if the surface of the Earth all the seawater pumped away, then the Earth does not look round, and the following often quoted picture also seems to verify this The following often quoted picture seems to confirm this view.

So is this the case? The answer is no. Because this picture is a very exaggerated way for scientists to describe the difference in height of the "geoid" (i.e., the gravitational equilibrium plane that coincides with the static sea level), not the so-called "Earth's appearance after all the seawater has been pumped away".

If you look closely, you will see that the number in the scale on the right side of the graph ranges between plus and minus 80, and the unit is "m", or "meters", compared to the radius of the Earth of about 6371 km, the "geoid "Compared with the radius of the Earth of about 6371 km, the difference in height of the "geodetic level" is several orders of magnitude, which can be said to be minimal.

Scientists say the Earth is round, but it is an objective description of the Earth

The Earth indeed has trenches more than 10,000 meters deep and mountains more than 8,000 meters high. The known data show that Mount Everest is the highest mountain on Earth, with an altitude of about 8,848 meters, and the deepest trench on Earth is the Mariana Trench, with a depth of 11,034 meters, which is considerable for humans but compared to the volume of the Earth, it is not worth mentioning.

The average radius of the Earth is about 6371 km, a simple calculation will show that the height of the Earth's highest mountain is only equivalent to about 0.14% of the Earth's radius, while the depth of the Earth's deepest trench is equivalent to about 0.17% of the Earth's diameter, what is the concept?

Let's say that the radius of a standard basketball is about 123 mm, that is, if we reduce the Earth to a standard basketball so big, then the highest bump on the surface of the Earth is about 0.17 mm, the lowest depression is about 0.2 mm, the height difference is only 0.37 mm, which is shallower than the depth of the grain on the basketball, can be said to be very flat.

Of course, the flatness of the surface does not mean that the Earth is very round, and what determines the degree of roundness of the Earth is the roundness error of the Earth on the whole.

The earth has been rotating, in the process will produce "centrifugal force", this force is a virtual force, its size is proportional to the angular velocity, on the surface of the earth, the lower the latitude angular velocity is greater, the "centrifugal force" is also greater, which will cause the earth This causes a certain degree of the bulge at the equator, which makes the Earth's polar radius larger than the Earth's equatorial radius.

In the past, scientists have long measured various data of the Earth through artificial satellites, and the measured data show that the polar radius of the Earth is about 6356.8 km, and the equatorial radius is about 6378.1 km, with a difference of 21.3 km, according to which the overall circularity error of the Earth is "21.3/(6356.8 + 6378.1)/2 6378.1)/2", the result of the calculation is about 3.3‰ (3.3 thousandths).

As a comparison, the roundness error of a 40 mm diameter quality table tennis ball used for competition is required to be controlled within 0.1 mm, which is 5‰ (five thousandths), which means that if we reduce the diameter of the earth to 40 mm, then its roundness error will fully comply with the standards of a quality table tennis ball, as to how round the quality table tennis ball is, I believe you should have the concept.

Through the above data analysis can be seen, that the Earth can indeed be said to be very round we humans through a variety of spacecraft photographed the image of the Earth is indeed the same, from the view of space, the Earth will always be presented in front of our eyes with a nearly perfect spherical shape.

What is the force that makes the Earth so round?

The answer is gravity. Gravity is the weakest of the four known fundamental forces in the universe, and because it is a long-range force and has only an "attractive" force and no "repulsive" force, it can be superimposed infinitely.

As we know, the magnitude of gravity is proportional to the mass, so when the mass of an object reaches a certain level, its gravitational force can be superimposed enough to make the matter that makes up the object behave as a fluid at the macroscopic level.

As long as the mass of a celestial body is large enough, even if the body is composed mainly of rocky material, in this case, the body will naturally evolve into a sphere-like shape when the material constituting the body reaches hydrostatic equilibrium.