The ancients said: the name is irregular and the words are not smooth. Only with a clear definition can we better understand the essence of things. So let's study the definition first: what is space? In fact, if you think about it carefully, you will find that it is not easy to define. Ancient philosophers usually understood space as something that did not exist, that is to say, the ancients did not actually agree that space was an objective entity. The ancients thought that space was just a concept invented by human beings and a virtual concept that we used to express the change of the world. Without human space, it would not exist.
But this is a topic discussed by philosophers, because the ancients did not have a perfect scientific system at that time, and even did not understand what science was. When the scientific system is gradually established, the definition of space will be inevitable, because science emphasizes rigor. How did Newton define space? Newton thinks that space is an objective entity, but space itself is static, which means that Newton thinks that there is actually an absolutely static object in our universe, and this object is space. Then all the movements derived from this space are real movements.
With the help of Newton's definition, then we can use Newton's mechanics to explain most of the movements at that time, because Newton's definition of space is equivalent to establishing a standard and framework for everything, and people can express space itself with space coordinates, so Newton's mechanics really did everything at that time.
But Newton's definition of space has a big bug, that is, we can't see or touch Newton's space. Since I haven't seen or touched it, how can I assert that this thing must exist? For example, although we can't see or touch the electromagnetic field, with the improvement of measurement technology, we can even detect the field strength anywhere in space. Many people think that electromagnetic field is a virtual thing created by human beings. In fact, electromagnetic field is an objective thing that is not transferred by human consciousness. Electromagnetic field exists when human beings exist, and it still exists when human beings don't exist. But in the face of space, it seems that we can't observe it through the improvement of technology.
The definition of space is not important. Newtonian mechanics is good enough, but there is an unexplained problem, that is, why the speed of light is constant with respect to all reference frames. I have written many articles on special relativity to explain this problem, in fact, because what we think of space is actually more plastic. (Of course, time is also more plastic and can slow down or accelerate).
In Newton's time, space was an absolutely static thing, but in order to explain the constant speed of light, Einstein thought that we must change our original understanding of space. Space is no longer a fixed thing. Space can not only become bigger and smaller, but also be bent. At the same time, because time is also plastic, it is ready to combine space and time to form one thing: time and space.
Once we realize the existence of time and space, then time and space can no longer be analyzed separately. If you want to analyze, you have to analyze directly. This analysis doesn't matter. It leads directly to a very strange conclusion that our time and space are actually curved. In Newton's time, time and space were considered flat, but in Einstein's time, what was the combination of time and space? Time and space? It's actually curved.
Therefore, from the analysis here, we can see that from Newton's absolute view of time and space to Einstein's relativistic view of time and space, people's understanding of space is getting deeper and deeper, and their understanding of space itself is becoming more and more complicated. We can also make a mathematical description of space-time itself: curvature. In other words, we can measure its curvature at any position in time and space. Curvature is the degree of bending. With this understanding, Einstein's general theory of relativity began to shine.