Scientists are trying to determine the properties of the graviton – a hypothetical particle that carries the force of gravity. In a work published in the magazine *High Energy Astrophysics Journal* the professor. Marek Pisada and colleagues based on analysis of 12 galactic clusters **Introduce a new constraint on the mass of graviton**. It is seven times stronger than the limitations of observing gravitational waves.

General relativity (GST) has changed our ideas about gravity. According to the OTW, matter bends spacetime, and all objects, if unaffected by interactions other than gravitational, move in this curved spacetime along special paths called geodesics. Since there are no very large curvatures of time and low velocities, compared to the speed of light, Einstein’s theory reworks Newton’s law of universal gravitation, which we still successfully apply to describe the motion of planets or stars in galaxies.

We know that the other three fundamental forces – the long-range electromagnetic force, the weak and the strong forces that govern matter at the subatomic level – are quantum forces in nature. In the quantitative description, the reaction consists of the exchange of a particle (the boson) that carries it. For electromagnetism, it is a photon – a light particle, a quantum of an electromagnetic wave. For strong and weak interactions, these are gluons and Z and W bosons respectively For over a hundred years, physicists have tried to look at universal gravity in the same way, searching for a quantum theory of gravity. By analogy with other interactions, a hypothetical gravitational-carrying particle would be a so-called graviton. Because of the infinite range of gravitational interactions that decrease with the square of the distance, the graviton – like the photon – must be massless. However, these are just theoretical predictions that need to be verified experimentally.

When examining the properties of the hypothetical graviton, the opposite question can be asked: what observable results should appear in the available picture of the universe and its dynamics, if the graviton has different properties than we expect – for example, if it has a very large effect. Small but non-zero mass? If the observational data – always burdened with uncertainty – are consistent with the massless hypothesis of the graviton, then the uncertainty associated with these data allows to estimate the maximum mass of the graviton in advance, that is, it allows answering the question about the influence of light. It can be a graviton, so that the consequences of its mass do not conflict with the observational data. In a study published in the journal High Energy Astrophysics, Professor F. Marek Bisiada of the NCBJ with Dr. Alexandra Bjorkoska-Corbas of the University of Silesia and Professor. Thus Shuo Cao of Bejing Normal University obtained a limitation on the mass of graviton m_{g} <5 10^{-29} volts.

*Each particle has a distinct length called a Compton wave – inversely proportional to its mass* – Explains the professor. Marek is sovereign. *The higher the mass, the shorter the wavelength. In the case of the interaction carrier particles, the Compton wavelength determines the extent of the interaction. Zero mass means the infinite compton wavelength, or infinite range. In the case of electromagnetism, theory predicts that the photon should be massless. Same thing with gravity. Thus, studies of the mass of the graviton are actually a test of the theory. It is a very important test, because some researchers have proposed theories that modulate GTA, which predict that the range of gravitational interaction should be limited. In theories of such modifications, the Newtonian voltage undergoes: over long distances the force of gravity decreases faster than the square of the distance*.

We currently have more and more accurate measurements of the masses of galaxy clusters as a function of distance from the center. This is possible thanks to a combination of X-ray observations and cosmic microwave radiation recorded by the Planck satellite.

*In our research, we used collective measurements of 12 galactic groups from the X-COP sample, to test for possible deviations from the Newtonian potential* Professor Pisyadeh adds. *As a result, we get one of the strongest upper limits of the mass of the graviton. It is seven times by magnitude (10 million times) more powerful than the limitations provided by the observation of gravitational waves by LIGO-Virgo detectors.*.

NCBJ scientists participate in all ongoing and planned projects of major importance to cosmology. They will definitely bring new and more accurate tests of basic physics.

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