In an era when science is not so advanced and the amount of human information is still low, people have always upheld the saying that the sky is round, that is, the theory of Gaitian. In ancient China, when we described a location, we also talked about a place. It is conceivable that a place where the sky is round and round is the common perception of the ancients.
Tianyuan Place
Since the opening of the new route of , Western navigators have begun to explore the world, and Magellan has completed the first time around the world for mankind, thus proving that the earth of is a sphere.
When people know that the earth is round rather than square, Westerners use the sun’s rays and simple geometric principles to determine the circumference and radius of the earth. The accuracy is almost the same as now. It can be seen that the wisdom of mankind at that time should not be underestimated!
The ancients measured the radius on the ground
Since the last century, humans have begun to explore outer space. When the rocket keeps rising from the ground, it can be clearly found that the earth is a round sphere.
So, how much height does human beings have to observe intuitionally that the earth is round? How high is the distance from the ground to see the entire earth sphere?
If one stands on the highest mountain- Everest , can you see the arc of the earth? Regrettably, even if people are now on Mount Everest, which is 8,844.43 meters above sea level, there is still no arc in sight. Even if the current passenger plane flies at a height of more than 10,000 meters, it is almost impossible to see any arc of the earth!
Why are passenger planes flying at an altitude of ten kilometers,Still can't see the arc of the earth?
When looking at the ground from an airplane, you will be obstructed by mountains or clouds. You may not even be able to see the scenery outside, let alone the curvature of the earth. In addition, when comparing the altitude of the airplane with the radius of the earth itself, this altitude seems insignificant. Because the average radius of the earth is 6371.393 kilometers, and ten kilometers seems to move close to the surface.
But if the plane encounters a vast and relatively flat place like oceans and deserts, you can barely see a slight arc of the earth on the plane.
There is a foreigner named Felix Baumgartner. He is good at extreme sports and has completed the world record of 39000km skydiving. When he rises to such a height, the image taken by the camera shows that the curvature of the earth does appear, but is this true the curvature of the earth?
The answer is no, the radian of the picture is the image distortion caused by the wide-angle lens, not the true radian.
If you want to see the obvious curvature of the earth's sphere, it must be more than 100km away from the surface, but this is only to see the obvious curvature, but you can't see the entire earth. Even if an astronaut can make a rocket that can raise the altitude to 400km, he still can't see the entire earth. Fortunately, they can already see the arc easily!
The question now is, how far above the surface do we have to rise to see the whole earth?
This relates to the line of sight of the human eye. The maximum horizontal angle of the human eye is about 124 degrees. The height can be easily calculated by simple geometric calculations to be 340,000km.
If you look at the earth from the moon, what does the earth look like?
Looking at the earth from the moon,It shines because of the reflection of the sun, which is very fascinating to see. Because the moon has only one side facing the earth, it can only be observed on the surface of the moon facing the earth. Seeing the entire earth from the moon is 14 times as large as the entire moon (that is, the moon at fifteen) as we see it on the earth.
NASA launched a picture of the Earth. It is on Mars, and the Earth seen there is very small, like a grain of dust in the vast universe.
When Voyager One was 6 billion kilometers away from the earth, it was in 1990. That is the farthest photo it has ever taken of the earth, and the earth is a small blue dot on such a large scale. But on this inconspicuous little blue dot, all kinds of life and wisdom breed.
.
