Everyone knows that outside the earth is the universe, so what is outside the universe? Could it be that, as the science fiction film showed, the earth is just a toy of a powerful extraterrestrial civilization, and the existence of human beings is arranged?
Because ancient science and technology were very backward, people at that time believed that the sky was round and the earth was square, and there was a heavenly cover theory of the round place, the main point of view of which was that the sky was above and the earth was below, and the sky was like a hemispherical cover, covering human beings inside. In the 6th century BC, the ancient Greek mathematician Pythagoras proposed the theory that the earth is spherical, and many humanistic scholars in Europe at that time believed that the earth was round. From 1519 to 1522, the Portuguese Magellan completed the first circumnavigation of the globe in human history, and he proved the theory of the earth circle with practice, which made an important significance to science and the exploration of the universe.
Subsequently, geocentristic theory, heliocentrism, cosmic infinity theory, Einstein's theory of relativity, space-time variability and the big bang theory of the universe constantly updated human cognition of the universe, and then with the continuous progress of science and technology, people's understanding of the universe also expanded to the Milky Way and the depths of the universe farther than ten billion light-years, and realized that the earth was really very small. From the perspective of the development stage of our understanding of the universe, human exploration and cognition of the earth and the universe are in constant change, and there are both correct understandings and wrong inferences.
So far, the observable age of the human universe is estimated at about 13.8 billion light years, due to the continuous expansion of the universe, the radius of the observable universe is not fixed, after complex deductions, the observable universe radius is about 46.5 billion light years, the diameter is about 93 billion light years, the observable universe is the largest cosmic range we can observe at present, but through the observation of the universe over the years, it reveals a terrible fact, we may never be able to observe what is outside the universe, why do we say so?
We all know that the universe originated from the Big Bang, followed by the formation of various galaxies, Earth, life, etc., in the early 20th century, astronomers found that those distant galaxies are slowly accelerating away from us, which means that in the future these galaxies will disappear forever in our field of vision, the universe is like a balloon that is constantly being inflated, and any position on the balloon is getting farther and farther away, so there will be a question here, what kind of shape is the universe? According to scientists, the universe has about three different forms.
The first, the flat universe, is flat, like a prairie that can't see the edge, can't find the edge, can't see the end.
The second, the closed universe, they believed that the universe resembled a sphere like Earth, and that whatever place it came from in the universe would eventually return to where it started.
The third, the arched universe, they believe that the universe has no boundaries, like our hilly terrain that rises and falls, with no borders and no end in sight.
Most researchers prefer the flat universe, but other researchers believe that the universe is a closed spherical shape, but in fact these are only theoretical speculations, to the current measurement range of human beings can only reflect the situation of the universe, just like before we thought that the earth is flat, but in fact the earth is round, because the earth is too large, our measurements can only reflect the local situation, so it leads to our misconception.