General relativity: a gap between observations and Einstein’s predictions

Einstein’s theory of general relativity predicts that the expansion of the Universe slows down over time. However, since 1998, we have known that expansion has been accelerating for around 5 billion years. Two possible explanations: the existence of invisible dark energy or a necessary revision of the laws of gravity on a very large scale. Which one is the right one? Are both possible? This is what cosmologists have been looking for for around thirty years.

A spatial investigation

Thanks to the Dark Energy Survey, a new study compared the distortions of space and time caused by galaxies over several billion years. Result: distant observations confirm Einstein, but at more recent times, between 3.5 and 5 billion years, a gap appears. Is this disagreement enough to reject general relativity? Reply with Camille Bonvin, associate professor in the department of theoretical physics at the University of Geneva and co-author of this study published in Nature Communications.