Albert Einstein's general relativity theory has been a pillar of contemporary physics for more than a century. But according to a recent study, there is a little discrepancy between Einstein's predictions and how the Universe has behaved during various cosmic eras.
In order to better understand the Universe's accelerated expansion, which was found 25 years ago, researchers from the University of Geneva and Toulouse III - Paul Sabatier examined data from the Dark Energy Survey. When applied on a global scale, the analysis revealed variances that cast doubt on Einstein's equations, especially for extrasolar occurrences.
These results, titled "Measurement of the Weyl potential evolution from the first three years of dark energy survey data," which were published in Nature Communications, lead to fresh debates on the validity of general relativity and the forces influencing the universe. The results point to gaps in our knowledge of space-time and dark energy, but they do not refute Einstein's theories.
According to Albert Einstein's theory, the Universe is deformed by matter, like a large, flexible sheet. These deformations, caused by the gravity of celestial bodies, are called ''gravitational wells''. When light passes through this irregular framework, its trajectory is bent by these wells, similar to the effect of a glass lens. However, in this case, it is gravity, not glass, that bends the light. This phenomenon is known as ''gravitational lensing''.
Observing it provides insights into the components, history, and expansion of the Universe. Its first measurement, taken during a solar eclipse in 1919, confirmed Einstein's theory, which predicted a light deflection twice as large as that predicted by Isaac Newton. This difference arises from Einstein's introduction of a key new element: the deformation of time, in addition to the deformation of space, to achieve the exact curvature of light.
"Until now, Dark Energy Survey data have been used to measure the distribution of matter in the Universe. In our study, we used this data to directly measure the distortion of time and space, enabling us to compare our findings with Einstein's predictions," says Camille Bonvin, associate professor in the Department of Theoretical Physics at the UNIGE Faculty of Science, who led the research.
"We discovered that in the distant past - 6 and 7 billion years ago - the depth of the wells aligns well with Einstein's predictions. However, closer to today, 3.5 and 5 billion years ago, they are slightly shallower than predicted by Einstein," reveals Isaac Tutusaus, assistant astronomer at the Institute of Research in Astrophysics and Planetology (IRAP/OMP) at Universite; Toulouse III - Paul Sabatier and the study's lead author.
