Finding the answer to the question of what a vacuum is is not so simple as it seems at first glance. This problem worried scientists from ancient times, and today there are several approaches that explain the physical side of this phenomenon.
The physical vacuum under the names "nothing", "ether", "substantial emptiness" is considered in many philosophical concepts. Almost all of these theories emphasize that the main advantage of this “nothing” is that, unlike our usual objects and phenomena, it is devoid of any physical restrictions. That is why it is considered as something universal, uniting all existing characteristics and properties.
Another important aspect that is highlighted in many philosophical works is that physical vacuum is the ontological basis of all existing objects and phenomena. Despite the fact that in the absolute dimension this space does not contain anything, it is potentially it is that factor that binds all natural forces and processes together.
Finally, if we move on to purely scientific aspects, we can note that although it is impossible to see the physical vacuum, its existence can be proved on the basis of numerous experiments. This should include the Casimir effect, and the so-called electron-positron pair, and the Lamb-Rutherford effect. So, for example, the well-known Casimir effect is proof that even in an absolutely seemingly “empty” space forces arise that force the two plates to come together.
Modern science considers the physical vacuum from the point of view of the theory of quantum fields, according to which it represents the fundamental (or ground) state of any energy field encountered in the surrounding reality. A significant part of modern physicists agree that any substance comes from this "airless space", from where it gets its basic properties and characteristics. Many go even further and try to prove that the physical vacuum is what our Universe arose from. For example, the famous scientist Y. Zeldovich in his work cites a number of points that such a concept absolutely does not contradict any of the objective laws discovered so far, except for the law of conservation of baryon charge, that is, the equilibrium between matter and antimatter.
In accordance with another modern approach, physical vacuum is the lowest energy state in which any real particles are simply absent. At the same time, these researchers agree that this particular type of matter is literally filled with all kinds of potential antiparticles and particles that can become real under the influence of external fields.
According to these ideas, in a vacuum there is a continuous formation and disappearance of such pairs of elements as positron and electron, nucleon and antinucleon. It is impossible to register them (at least for now), but when a number of conditions are met, they become quite tangible.