This method proves Einstein’s theories about the expansion of the universe

Two discoveries seek to verify the acceleration of the expansion of the universe and the existence of invisible dark matter, which is believed to represent 85 percent of all that in the cosmos.

A team from the University of Geneva (Unige) in Switzerland developed the first method to jointly test Albert Einstein’s and Leonhard Euler’s theories about the accelerating expansion of the universe and dark matter using a measure that had not been used before. : the distortion of time, as published in the journal Nature Astronomy.

Leonhard Euler (1707-1783) described the movements of celestial objects, while Albert Einstein (1879-1955) explained how these bodies distort the universe. Since the discovery of dark matter and the acceleration of the expansion of the universe, the validity of his equations has been put to the test.

The theories of both revolutionized our understanding of the cosmos. With the famous equation that bears his name, Euler provided scientists with a powerful tool for calculating the motions of galaxies in the universe. With his theory of general relativity, Einstein showed that this is not a static framework: it can be distorted by star clusters and constellations.

Physicists have tested these equations in every possible way, which so far have been successful. However, two discoveries seek to verify these models: the acceleration of the expansion of the universe and the existence of invisible dark matter, which is believed to represent 85 percent of all matter in the cosmos. Researchers are still unable to answer this question of whether these mysterious phenomena still obey Einstein’s and Euler’s equations.

“The problem is that current cosmological data does not allow us to differentiate between a theory that breaks Einstein’s equations and another that breaks Euler’s. This is what we demonstrated in our study. We also present a mathematical method to solve this problem. It is the culmination of 10 years of research,” said Camille Bonvin, associate professor in the Department of Theoretical Physics at Unige’s Faculty of Sciences and lead author of the study.

The researchers were unable to differentiate the validity of these two equations at the far reaches of the Universe because they were missing one ingredient: measuring time warp. Until then, they only knew how to measure the speed of celestial objects and the sum of the distortion of time and space. So they developed a method to access this additional measure, and “it’s a first,” says Bonvin.

If the distortion of time is not equal to the sum of time and space, that is, the result given by the theory of general relativity, it means that Einstein’s model does not work. If the time distortion does not correspond to the speed of the galaxies calculated with Euler’s equation, it means that the latter is invalid. “This will allow us to find out if there are new forces or matter in the universe that violate these two theories,” said Levon Pogosian, a professor in the Department of Physics at Simon Fraser University in Canada, and co-author of the study published in the journal Nature Astronomy.

These results will be a crucial contribution to several missions whose objective is to determine the origin of the accelerated expansion of the universe and the nature of dark matter. Among them are the Euclid Space Telescope. This will be launched in July 2023 by the European Space Agency, in collaboration with Unige, and the Dark Energy Spectroscopic Instrument (DESI).

The latter began his five-year mission in 2021 in Arizona. There is also the international project of the giant Square Kilometer Array (SKA) radio telescope, in South Africa and Australia. It will begin its observations between 2028 and 2029.