Source: Mao Zedong's "Send the Plague"
Credentials:
People live on the earth, and because of the rotation of the earth, they walk 80 thousand miles a day unconsciously. The equator of the earth is 40 thousand kilometers long, which is 80 thousand miles. The earth rotates in the sky, so people living on the earth are also "surveying the sky". Thousands of rivers generally refer to many stars in the universe. As a result, the author of "Imagination" turned from a disaster in the countryside to a dialogue with the cowherd in the sky.
Attached (geographical knowledge):
This poem reveals that the earth is constantly rotating from west to east, which is suitable for the equatorial region. From this, we can calculate the linear velocity of the earth's rotation in the equatorial region and the length of the 10 arc on the equator. The linear speed of rotation in the equatorial region is 40,000 km ÷24 hours ≈ 1.670 km/h (80,000 miles or 40,000 km). The linear velocity of the earth's rotation gradually decreases from the equator to the poles. The length of 10 arc on the equator: 40000km ÷ 3600 ≈11KM/10. The equator is the great circle of the earth, so the length of every 10 arc of the great circle on the earth is about11km (the great circle of the sphere refers to the intersection of the section passing through the center of the sphere and the sphere).