Today, every student knows that the space in which a person exists is three-dimensional, that is, he has three dimensions: length, width and height. But what is four-dimensional space? If we study not only the spatial position of the body, but also how it changes in time, that is, the processes that occur in three-dimensional space, another coordinate appears - time. Four-dimensional space and consists of three spatial and one time coordinate. In this case, physicists and philosophers speak of a single space-time continuum. Time and space are interconnected. In essence, they appear as different sides of four-dimensional space-time.
Four-dimensional space as a unity of space and time has an interesting property, which is a consequence of the theory of relativity A. Einstein. It lies in the fact that with the approach of the speed of the body to the light, time flows more slowly on it, and the body itself decreases in size.
Imagine such a four-dimensional space quite difficult. When we painted flat geometric shapes at school , we did not experience any particular difficulties - they were two-dimensional (had width and length). It was more difficult to draw and represent three-dimensional figures - cones, pyramids, cylinders and others. And to imagine four-dimensional figures is quite difficult even for mathematicians and physicists.
Of course, it is necessary to get used to the concept of “four-dimensional space”. Theoretical physicists apply the concept of four-dimensional space-time as a tool in calculations, develop four-dimensional geometry in this world.
The theory of A. Einstein suggests that gravitational bodies contribute to the curvature of four-dimensional space-time around itself. It is not easy to visualize “ordinary” space-time, and curved space is even more difficult. But a theoretical physicist or mathematician does not need to imagine anything. Curvature for them means a change in the geometric properties of bodies or figures. So, for example, the circumference of a circle refers to its diameter on the plane as 3.14, but on a curved surface this is not entirely true. The possibility of curving four-dimensional space was theoretically suggested at the beginning of the nineteenth century by the Russian mathematician N. Lobachevsky. In the mid-nineteenth century, the German mathematician B. Riemann began to explore the “curved” spaces of not only three dimensions, but also four, and then with any number of dimensions. Since then, the geometry of curved space has been called non-Euclidean. The founders of non-Euclidean geometry did not know exactly under what conditions their geometry might come in handy. The mathematical apparatus that they created was subsequently used in the formulation of general relativity (general theory of relativity).
A. Einstein pointed out an interesting effect regarding time: in a powerful gravitational field, time will flow more slowly than outside it. This means that time on the Sun will go slower than on Earth, since the gravitational force of the Sun is significantly greater than the gravitational force of the Earth. For the same reason, watches at a certain height above the Earth go a little faster than on the surface of our planet.
Of great importance for the whole science are the properties of time discovered by scientists, such as slowing it down next to neutron stars, stopping time in “black holes”, the hypothetical possibility of “passing” time into space and the reverse process.
Out of the field of gravity appears So called free space - an environment in which the force of gravity on the body either does not act at all, or acts very weakly in comparison with earthly gravity. Stars are in outer space, and most of it is free space.