In ancient times, because of the small range of activities, people only saw a small part of their living area.

Therefore, just by intuition, there are various sayings of "the sky is round and the place is round". For example, as early as two thousand years in China.

Many years ago, in the Zhou Dynasty, there was a saying that "the sky is round as a cover and the ground is like a chess board". Ancient Egypt

As we all know, the sky is like a dome-shaped ceiling and the earth is like a square box. Russians believe that the earth

Like a shield, carried by three giant whales, floating in the vast ocean. Indians have similar ones.

Legend has it, but they think that it is not the giant whale that carries this land, but the three heads standing on the back of the turtle.

Elephant. When an elephant moves, it will cause an earthquake.

With the development of production technology, the expansion of human activities and the accumulation of all kinds of knowledge, people gradually

It is recognized that the earth cannot be flat in a large range, but should be curved and arc-shaped. Because in the sea

Looking at the offshore ships, first the hull disappears, and then the mast sails. People who travel on land, if they go to the north,

Walking, some stars will disappear on the southern horizon, while others will be on the northern horizon.

Appear on the internet. If you go to the south, the situation is just the opposite. These phenomena can only be understood if the earth is curved.

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Around 500 BC, the ancient Greek mathematician Pythagoras and his disciples first put forward great ideas.

The hypothesis that the earth is spherical. They advocate using mathematics to explain the universe, thinking that in all three-dimensional graphics, the sphere

Is the most beautiful. The shape of the universe should be spherical, and all celestial bodies in the universe, including the earth, should be

It should be spherical. It took Aristotle, a famous scientist and philosopher in ancient Greece 100 years to visit the earth for the first time.

Prove that the earth is spherical. He observed the celestial phenomena from the projection of the earth on the moon during the eclipse.

It is inferred that the shape of the earth is spherical. At that time, some people opposed it: if the earth is really

It is spherical. Why don't people who live on the other side of the earth fall into the air below? At that time,

Because people don't understand gravity, it is difficult to answer this question.

Zhang Heng, an astronomer in the Eastern Han Dynasty in China, once said that "the sky is like a chicken, and the ground is like a chicken yellow".

Compare the universe to an egg, and the earth is like the yolk in an egg. This theory is called Huntian theory, which is better than the previous theory of covering the sky.

Great progress has been made.

15 and 16 century's great geographical discoveries, especially1519-1521a ship led by Magellan.

The team successfully sailed around the earth, which provided strong evidence that the earth was spherical. In the late Ming Dynasty,

Western missionaries Matteo Ricci and Tang Ruowang came to China and introduced scientific knowledge such as astronomy, geography and mathematics.

Knowledge, the translated name of "Earth" appeared in China.

So, is the earth a round right sphere? /kloc-at the end of 0/7, British physicist Newton root

According to the theory of gravity he discovered, due to the inertial centrifugal force produced by rotation, the earth's

Matter moves in the equatorial direction, so he came to the conclusion that the earth should have an equatorial radius greater than the polar radius.

Flat sphere. However, according to their meridian survey, the faction headed by Cassini, director of the Paris Observatory,

According to inaccurate data, when the earth revolves around the sun, it should extend to the poles, and it is a long ball, not a flat ball.

Ball. This argument lasted for half a century. Voltaire, a French enlightenment thinker, argued about the shape of the earth.

Once said: "In London, it is considered an orange, but in Paris, it is imagined as a watermelon." Until 18.

In 1930s, the French Academy of Sciences sent two expeditions, one to Lapland near the Arctic Circle and the other to Lapland.

Peru, near the equator in South America, measured the meridian length between the two places, but found that Cassini's measurement results were as follows

Wrong, and Newton's inference is correct.

With the continuous progress of measurement technology, especially the use of artificial earth satellites, earth measurement is now

The equatorial radius is 6378 140m and the polar radius is 6356755m. The difference between them is 2 1385m, and its flatness is

1/298.2。 In this respect, the earth is much more round than oranges.

In addition, people also found from the measurement that the equator of the earth is not a perfect circle, but is similar to an ellipse, which is the largest.

The radius differs from the minimum radius by more than 200 meters. It is also found that the northern hemisphere of the earth is thinner than the southern hemisphere; Arctic region

The geoid (mean sea level) in this area is about 10 meter higher than that in the reference oblate sphere and Antarctic area.

It should be recessed about 30 meters. So some people compare the shape of the earth to a pear and describe the globe as a pear.

Body.

In fact, the earth is neither like an orange nor a pear, but a sphere with its own unique shape.

If this huge earth is shrunk into a globe with a diameter of 1 m, the equatorial radius is only polar.

The radius is greater than 1mm, which is a subtle difference that cannot be expressed on the globe, so we use it.

The globe is still round.