What is spacetime ?

 While the idea  of space-time is strongly related to Einstein's theory of "special  relativism", which appeared in 1905, it was the athlete Hermann  Minkowski who coined this expression three years after the emergence of  Einstein's theory, in 1908

Time is a measure of the change that takes place within what we know of the place. The series of changes that your life takes during a time and somewhere. The  word "space-time" is a fusion of the two concepts together within a  certain continuity: the three spatial dimensions, in addition to the  fourth dimension "time". While we have the ability  to control the first three dimensions (height, width, and depth), we  seem unable to control, manipulate, or move through time, although  physics tells us that this dimension is similar to the other three  dimensions. For human existence, time appears as a one-way road with strict limits on speed

Regardless of our inability to manipulate our experience with time, we can observe the existence and uniqueness of space-time based on experience. If you rotate a bucket of water on a circular path, you know that when you reach a certain speed you can rotate the bucket completely and sideways without the water coming out of it.

This results in the principle of equivalence, the main principle of Einstein's theory of general relativity. This principle states that gravity works in one direction and equates acceleration in the other

For  this reason too, it is not possible to find a lift that offers a  feeling of increasing gravity during climbing, or decreasing during  landing. The principle of equivalence means that gravity affects time and space  measurements, that is, they distort the space-time itself.
The  idea of ​​an object with an enormous mass distorting the space around  it is a familiar idea for us - a planet or star is distorting the  geometry of the surrounding area, causing the objects to be dragged  nearby by the dips created by that body. But scientists have also been able to detect the possibility of mass objects to distort time as well. For  example, if you synchronize two hours and take one into space (away  from the Earth's gravity center), these two hours will lose their  synchronization. This proves that time is part of the same medium of space, and therefore space-time is a real and useful concept

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