If you imagine that the atomic nucleus grew to the size of an orange, then the electrons will look like a point diameter, no thicker than a human hair, a runaway in orbits distant from the core for several kilometers! A huge space between them - than it is filled? Nothing, emptiness?!
In the language of science is "nothing" is called physical vacuum. That is a vacuum in terms of modern physics, we talk today.
Omnipresent ether
Let us agree at once: we are not talking about technical vacuum - a rarefied gas of very low pressure, which are widely used in various electronic devices from the light bulb to the tube. The gas pressure in them is usually 10 -6 -10 -7 mm Hg. Art. But at the same time in one cubic centimeter volume contains neither more nor less - a few billion atoms or molecules of the gas! The deeper the vacuum required in accelerators - 10 -10 mm Hg. Art. But in this case, in one cubic centimeter it is still a million particles. Even the high vacuum - the space - can not, strictly speaking, be called emptiness: for each "cube" of interstellar space, on average, two or three particles.
The object of our conversation - the emptiness, the space in which we can not see anything, not a single particle, a single photon. It seems to be something to talk about: nothing is nothing! What can you say about anything? This "absolute nothing", the complete absence of any kind was the matter, and it is impossible to imagine something.
So we have a little sin against the truth and for the sake of clarity, to replace the physical vacuum of his closest model - the vacuum of space.
Because of the incredible vistas of the cosmos comes to us the light of the stars. With the help of radio waves Earth liaises with spaceships. All this is possible because both light and radio waves (both is nothing like electromagnetic waves) is very well distributed in the vacuum of space. But how can the waves move through anything?
Remember, sound, that is, the elastic vibrations of the particles of matter are well transmitted through air, water, solid. And it does not apply in the emptiness, in which there is no substance, and hence there is nothing to hesitate. Or waves on the surface of the water? Clean water will disappear and the waves.
So, for the propagation of waves need some material medium, vehicle vibrations. Not an exception and electromagnetic waves - they also want the mediator. So, despite the lack of substance, the vacuum is still not completely empty?!
But what he then filled, if not substance? This question troubled the minds of thinkers in ancient times. According to Anaximander, Democritus and their followers, the vacuum (they called it Amer, or apeiron) is a material medium that fills a universal space and atoms of matter are indivisible bunches vacuum (Apeiron, amer) - which -What kind of dense clumps that can sometimes be found in the pudding.
On a strictly physical terms is very similar idea was first formulated in the second half of the XVII century Dutch scientist Christiaan Huygens. World space, he thought, permeated the air - a special matter, weightless and transparent. This matter and serves as a carrier light waves, similar to how air is the carrier of the sound. Following the Huygens British physicists Faraday and Maxwell not considered air as the carrier of light waves, and in general all types of electromagnetic fields. Unlike ordinary weighty matter that is present only in some areas of space and one to Yaw impenetrable ether omnipresent, infinite and permeable.
For the first time in the History of Science vacuum (ether) was endowed with well-defined physical properties. Now it is not an "absolute nothing" and more or less specific "something". Allowing pretty well solve the problem of electromagnetic fields, the concept of a world ether is very firmly rooted in the minds of physicists of the XIX century. So firmly that in the early XX century continued efforts to experimentally detect the etheric matter.
The failure of many such efforts to some physicists pushed to an extreme measure: they announced that the ether, in principle, do not see any devices.
Dirac sea
When did Einstein's theory, the attention of physicists shifted to the assimilation of the global properties of space-time. As well as for their development (or fight with them). Perhaps on this very quickly for many it was the ether.
Lost, but not all, including Einstein himself. His theory explains well the geometric structure of the global space, its, so to speak, architecture. But to say what material is built grandiose tion building, she could not. Moreover, it appeared in 1916, Einstein's theory of gravitation predicted that in the space other than electromagnetic waves can propagate also gravitational waves. But what is the material environment, the "sea" on which these waves propagate?
They say: "A holy place is never empty." Quantum theory of the structure of matter and experimental discoveries that accompanied Physics 20-30-ies of the century brought with them new ideas about the structure of matter and vacuum. Of course, just to see the structure of the vacuum fails, as well as the "feel" of what it is made. The vacuum was still everywhere and nowhere.
The first in a new way to look at the vacuum has managed in 1931 when a young English physicist Paul Dirac. Solving the problem of the motion of a single electron in a space free of any other particles, fields, forces and so on. E., It has received for the two values of the electron energy - positive and negative. With positive energy it was all clear, but that is negative energy? What is the physical meaning of it?
Of course, Dirac could well do as we are doing by calculating, for example, the length of the hypotenuse of a triangle by the Pythagorean theorem. Get two values, square root - positive and negative, we reject the latter as meaningless. Negative length of the interval can not be? Just as it may seem physically meaningless negative energy .
Still, Dirac tried to understand the value obtained. What if negative energy is not such a nonsense? Perhaps the second solution belongs to a certain mirror counterpart of the electron? So there is a crazy idea at first glance. What if the vacuum is not empty, but rather filled to negative-energy electrons? The result is something like an infinitely deep well with a myriad of cells, each of which sits on the electron. Jump out of this hole the electron can only get enough for this energy - the more, the deeper he sits. When it does happen, the electron is in the real world, and in a vacuum, in the place where he was sitting, a hole is formed. At this point, there is a positive charge equal in magnitude to the electron charge.
It is the same in a vacuum. The hole in it - the real particle is no less real than the electron. So for the first time it predicted a positron - the antithesis of the electron. Because of the vacuum of nothingness, they are born in pairs. After wandering in our world, the electron can go back into the vacuum. But it can only sit in a cell, since all other busy. Therefore, our wanderer must meet a hole, that is a positron and provzaimodeistvovat him. After that the electron and hole will disappear, dissolve in a vacuum.
Dirac replied to the question why the electrons in a vacuum is not observable. See an electron can only be if it somehow provzaimodeistvuet physical instrument will give a signal about yourself. But any interaction of bodies is a change in their energy. By interacting with the device, an electron in a vacuum must somehow change their energy, move to the former place in the pit to another. But where? Pit something full to capacity, all cells are occupied. Here comes an sit in his cell and go unnoticed.
In 1932, the theoretical prediction of Dirac brilliantly confirmed in an experiment: in one of the photographic plates exposed to cosmic rays, had found traces of the particles of the same mass as the electron, but positively charged. So positron became a full member of the family of elementary particles. Later added to the list of antiparticles antiprotons, antimesons, antihyperons and many other anti.
But if the proton has its anti-particle, then there must be a vacuum and filled unborn protons. Just like neutron vacuum, the meson, and so on. So the void! So little by little the physical vacuum finds its material content, allowing the contradictions that was unable to handle the old broadcast in classical physics of the XIX century.
FOAM VACUUM
«crazy» ideas of Dirac's ideas gave rise to a completely fantastic.
Imagine that we are armed with extremely powerful microscope, giving a glimpse into the world of incredibly small scale - many billions of times smaller than the size of the elementary particles. If that were possible, we would see a complex grain structure like soap suds. This "foam" is the vacuum matter, which, according to scientists, must possess enormous density - 10 93 grams per cubic centimeter. This huge figure is easier to feel, if we imagine that in one cubic micron pressed tens of trillions metagalaxies!
How can hidden all the colossal mass, and hidden so securely that we vacuum looks absolutely empty? The answer is to be found in the so-called gravitational mass defect. Infinitely large density of the vacuum creates an infinitely strong gravitational field that bends space so that vacuum energy appears as if sealed in cells "foam." Therefore, we can not find it in any device - vacuum seems to us empty.
(Something remotely similar happening in the collapse - gravitational collapse - massive star, when strong gravitational field closes the space in which lies a contracting star with all his weight, the energy of the radiation. The image of "black hole" that we have not seen for us as it does not exist.)
At some point the energy blockage is still not completely reliable, and part of the energy spills over into our world. The cell "foam" as it breaks, and against the background of empty space appear small bunches (portions, quanta) of energy in the form of elementary particles.
So, from the point of view of physics, vacuum all elementary particles, nuclei, atoms and even the stars and the galaxy is nothing, as a result of quantum fluctuations in the vacuum - no more than the spray from the waves, raging ocean power vacuum. Moreover, in comparison with a giant vacuum density is now our usual stuff looks infinitely sparse, almost empty!
As physics progressed deeper into the matter, in the world ever smaller scales, constantly opening more intensive energy sources. At the core it was a hidden power is much greater than in the atom. Maybe in the proton, composed of quarks, it even more? A vacuum in the cells, trillions of times more compact than the proton energy, respectively, in trillions of times more?
And it is not impossible that one day people will learn to "uncork" the cell and use the limitless reserves of energy of the vacuum.