“Weighty” gravitons - the key to the expansion of the universe

Having discovered in 1990 that the Universe is expanding with acceleration, scientists are trying to figure out what is the dark energy that feeds this process, and why the acceleration is so small.

One of the most plausible theories is that dark energy is an essential attribute of a cosmic vacuum. Elementary particle physics predicts the existence of such energy, but at the same time its estimated value is 10120 times higher than that which is enough to create the observed acceleration. If the dark energy were so great, the Universe would be smashed long before the formation of the first stars and galaxies.

In 2010, physicists suggested that dark energy could still be vacuum energy if part of it is absorbed by hypothetical particles - gravitons. Gravitons serve as carriers of gravitational interaction - one of the four fundamental interactions, each of which is responsible for its particles.

The range that covers each of the fundamental interactions is determined by the mass of carrier particles. Thus, the electromagnetic interaction transmitted by photons that have no mass extends unlimitedly far, while the strong and weak nuclear interactions, the carriers of which are masses of Z and W bosons, propagate only on a subatomic scale.

Most physicists believe that graviton, like a photon, is a massless particle, so gravity travels unlimitedly throughout the universe. But if gravitons nevertheless have an insignificant, but non-zero mass of the order of 10–33 eV, this will still correspond to the observed picture of the world. (For comparison, the mass of neutrinos, the lightest known particle with a non-zero mass, is not more than 0.28 eV, and the electron is 510999 eV).

Massive gravitons are quite capable of absorbing most of the energy of the vacuum, and the remainder would be enough to maintain the acceleration with which the universe expands. Such a model is quite capable of explaining the results of observations without involving new entities - exotic particles.

The beautiful theory almost died in the bud when physicists expressed concern that “ghost fields” that have negative energy and are impossible in reality may be hidden behind the calculations. But another group of scientists refuted this assumption.

Experimentally verify the theory of massive gravitons, probably, it will be possible in the near future. If it is legitimate, the difference between the “classical” and the “massive” gravitational interactions between the Earth and the Moon will create a deviation of the orbital precession of the last one-part magnitude by 1012. Recent experiments with a laser beam reflected from a mirror left on the moon have made it possible to determine the precession and the distance between Earth and its natural satellite with an accuracy of one part per 1011.

According to Nature News

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