Since its formulation in 1915, Albert Einstein's general relativity, which describes gravity as an effect of the curvature of space-time, has been largely validated by experiments. This theory has successfully predicted phenomena such as black holes and gravitational waves.
On the left: observation of the black hole M87* in polarized light.
On the right: a simulation of a black hole created using general relativity.
Credit: EHT Collaboration
However, researchers at the University of Waterloo suggest that on cosmic scales, involving distances counted in billions of light-years, this theory might have gaps. They describe this phenomenon as a "cosmic glitch," an anomaly where the gravitational force proves to be about 1% weaker than predicted by the theory. This finding paves the way for a possible revision of the theory to include these observations.
The scientists propose adjusting the standard cosmological model, specifically by modifying the gravitational constant, to address these inconsistencies without challenging the success of general relativity in other areas. This approach suggests an extension of the theory, without overturning it.
This need for revision is not unprecedented. Einstein himself had to modify his theory shortly after its first formulation, adding what is called the "cosmological constant" to predict a static Universe, a popular hypothesis at the time. After being eliminated, this constant was re-evaluated and reintroduced later to explain the accelerated expansion of the Universe, discovered at the end of the 20th century.
Future observations of the large-scale structure of the Universe and the cosmic microwave background could confirm this "cosmic glitch" hypothesis. This advance represents a significant step in our understanding of the Universe, indicating that, even in the most fundamental areas of physics, adjustments remain necessary to harmonize theory and observation.