# Einstein and Euler: The Accelerating Expansion of the Universe and Dark Matter Theory Put to the Test

Cosmos is a unique laboratory for testing the laws of physics, especially the laws of Euler and Einstein. Euler explained how celestial bodies move, and Einstein explained how celestial bodies distort the universe.

After the discovery of dark matter and the acceleration of the expansion of the universe, the validity of the equation was put to the test. Can they explain this mysterious phenomenon? A team from the University of Geneva (UNIGE) has developed the first method to find out. Consider time skew, a measure that has never been used before. result *natural astronomy*.

The theories of Leonhard Euler (1707–1783) and Albert Einstein (1879–1955) revolutionized our understanding of the universe. Euler gave scientists a powerful tool to calculate the motion of galaxies in the universe through his famous equation that bears his name. Through his general theory of relativity, Einstein showed that the universe is not a static frame but can be distorted by star clusters and galaxies.

Physicists have tested these equations with all kinds of methods that have proven successful so far. But two discoveries continue to test these models: the acceleration of cosmic expansion and the existence of an invisible dark matter thought to make up 85% of the universe’s total matter. Does this mysterious phenomenon still obey Einstein’s and Euler’s equations? Researchers still cannot answer this question.

## missing ingredients

“The problem is that current cosmological data do not allow us to distinguish between theories that break Einstein’s equations and those that break Euler’s equations. This is what we have demonstrated in our study. We are also looking to solve this problem. We present a mathematical method. This is the culmination of a decade of research,” explains Camille Bonvin, first author of the study and Associate Professor in the Department of Theoretical Physics in the Faculty of Science at UNIGE.

The researchers couldn’t distinguish the validity of these two equations at the far end of the universe because they were missing a “component,” a measure of time distortion. “Until then, we only knew how to measure the speed of a celestial body and the sum of its distortions in time and space. We have developed a way to access this additional measurement, and this is the first of its kind,” says Camille Bonvin.

If the time distortion is not equal to the sum of time and space, i.e. the result produced by general relativity, then Einstein’s model does not work. If the time warp does not match the galaxy’s speed calculated by Euler’s equation, it means that the latter is invalid. “This will allow us to discover whether new forces or matter exist in the universe that violate these two theories,” said study co-author Levon Pogosian, professor of physics at Simon Fraser University in Canada. explained. .

## reality check

These results will make crucial contributions to several missions aimed at determining the origins of the accelerating expansion of the universe and the properties of dark matter. These include the EUCLID space telescope, which the European Space Agency (ESA) has partnered with UNIGE to launch in July 2023, and the Dark Energy Spectroscopic Instrument (DESI), which launched a five-year mission in Arizona in 2021. . There are also international Square Kilometer Array (SKA) giant radio telescope projects in South Africa and Australia that will start observing in 2028/29.

“Our methods will be integrated into these different missions. This is already the case with DESI, where we became an external collaborator thanks to this research,” says Camille Bonvin. The research team successfully tested the model on a synthetic catalog of galaxies. The next step is to use the first data provided by DESI to test it, identify obstacles and minimize system functionality that could hinder application.

**Additional Information:**

Camille Bonvin et al, Modified Einstein vs. Modified Euler for Dark Matter, *natural astronomy* (2023). DOI: 10.1038/s41550-023-02003-y. In ~ *arXiv*: arxiv.org/abs/2209.03614

**Journal information:**

natural astronomy

arXiv

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