Mass is one of the fundamental and at the same time mysterious concepts in science. In the world of elementary particles, it cannot be separated from energy. It is nonzero even for neutrinos, and most of it is located in the invisible part of the Universe. RIA Novosti tells what physicists know about mass and what secrets are associated with it.
Relatively and elementary
In the suburbs of Paris, at the headquarters of the International Bureau of Weights and Measures, there is a cylinder made of an alloy of platinum and iridium weighing exactly one kilogram. This is the standard for the whole world. Mass can be expressed in terms of volume and density and it can be considered that it serves as a measure of the amount of matter in the body. But physicists studying the microworld are not satisfied with such a simple explanation.
Imagine moving this cylinder. Its height does not exceed four centimeters; nevertheless, a noticeable effort will have to be made. It will take even more effort to move, for example, a refrigerator. The need to apply the force of physics is explained by the inertia of bodies, and mass is considered as a coefficient connecting the force and the resulting acceleration (F = ma).
Mass serves as a measure not only of motion, but also of gravity, which forces bodies to attract each other (F = GMm / R2). When we get on the scale, the arrow is deflected. This is because the mass of the Earth is very large, and the force of gravity literally pushes us to the surface. On a lighter moon, a person weighs six times less.
Gravity is no less mysterious than mass. The assumption that some very massive bodies can emit gravitational waves when moving was experimentally confirmed only in 2015 at the LIGO detector. Two years later, this discovery was awarded the Nobel Prize.
According to the equivalence principle proposed by Galileo and refined by Einstein, gravitational and inertial masses are equal. It follows from this that massive objects are capable of bending space-time. Stars and planets create gravitational funnels around them, in which natural and artificial satellites revolve until they fall to the surface.
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Quark interacts with the Higgs field / Illustration RIA Novosti / Alina Polyanina.
Where does the mass come from
Physicists are convinced that elementary particles must have mass. It has been proved that the electron and the building blocks of the universe - quarks - have mass. Otherwise, they could not form atoms and all visible matter. A massless universe would be a chaos of quanta of various radiation, rushing at the speed of light. There would be no galaxies, no stars, no planets.
But where does the mass come from?
“When creating the Standard Model in particle physics - a theory that describes the electromagnetic, weak and strong interaction of all elementary particles, great difficulties arose. The model contained unavoidable divergences due to the presence of nonzero masses in particles,”says Alexander Studenikin, Doctor of Science, Professor of the Department of Theoretical Physics at the Physics Department of the Lomonosov Moscow State University, RIA Novosti.
The solution was found by European scientists in the mid-1960s, suggesting that there is another field in nature - a scalar one. It permeates the entire Universe, but its influence is noticeable only at the micro level. The particles seem to get stuck in it and thus acquire mass.
The mysterious scalar field was named after British physicist Peter Higgs, one of the founders of the Standard Model. The boson is also named after him - a massive particle arising in the Higgs field. It was discovered in 2012 in experiments at the Large Hadron Collider at CERN. A year later, Higgs was awarded the Nobel Prize along with François Engler.
Ghost hunt
The ghost particle - neutrino - also had to be recognized as massive. This is due to observations of neutrino fluxes from the Sun and cosmic rays, which for a long time could not be explained. It turned out that a particle is capable of transforming into other states during movement, or oscillating, as physicists say. This is impossible without mass.
“Electronic neutrinos, born, for example, in the interior of the Sun, in the strict sense cannot be considered elementary particles, since their mass has no definite meaning. But in motion, each of them can be considered as a superposition of elementary particles (also called neutrinos) with masses m1, m2, m3. Due to the difference in the speed of mass neutrinos, the detector detects not only electron neutrinos, but also neutrinos of other types, for example, muon and tau neutrinos. This is a consequence of mixing and oscillations predicted in 1957 by Bruno Maksimovich Pontecorvo,”explains Professor Studenikin.
It has been established that the mass of a neutrino cannot exceed two tenths of an electron volt. But the exact meaning is still unknown. Scientists are doing this in the KATRIN experiment at the Karlsruhe Institute of Technology (Germany), launched on June 11.
“The question of the magnitude and nature of the neutrino mass is one of the main ones. His decision will serve as the basis for the further development of our understanding of the structure, - the professor concludes.
It would seem that in principle everything is known about the mass, it remains to clarify the nuances. But this is not the case. Physicists have calculated that the matter that we observe occupies only five percent of the mass of matter in the universe. The rest is hypothetical dark matter and energy, which do not emit anything and therefore are not registered. What particles do these unknown parts of the universe consist of, what is their structure, how do they interact with our world? The next generations of scientists will have to figure it out.
Tatiana Pichugina