5.05.2025

CERN

Research team develops new test to verify Einstein's theory of gravity using the Large Hadron Collider

A research team from the Center of Applied Space Technology and Microgravity (ZARM) at the University of Bremen and the Institute for Theoretical Physics at the University of Tübingen has developed an innovative approach to test the limits of Einstein's general theory of relativity. They propose to carry out this investigation using the Large Hadron Collider (LHC) at CERN.

Einstein's theory of gravity has revolutionized modern science and led to many successful predictions, including black holes, gravitational waves, and the evolution of the entire universe. However, the general theory of relativity (GR), together with the standard model of particle physics, has its limitations. On the one hand, there are observations, such as the accelerated expansion of the universe or the motion of stars at the edge of galaxies, that can only be explained in the context of GR by assuming the existence of unknown entities in the universe, commonly referred to as dark energy and dark matter. On the other hand, GR predicts that the gravitational force becomes infinitely strong in certain regions of the universe, so that it is still not possible to reconcile Einstein's theory of gravity with all the other forces of nature (electromagnetic force, weak and strong nuclear force).

As a result, many questions remain unanswered when it comes to understanding gravity, driving physicists worldwide to search for an extension or modification of GR that can clarify the still unexplained phenomena of gravity.

On April 28, 2025, a scientific paper by Christian Pfeifer and Dennis Rätzel from ZARM and Daniel Braun from the University of Tübingen was published, which deals with a test of the general theory of relativity. They propose testing the properties of gravity with particles whose speed is very close to the speed of light. These ultra-relativistic (or simply very fast) particles create a gravitational field that attracts stationary test particles when they fly by. The motion of the test particles can be predicted theoretically and compared with the observed motion, effectively turning the test particles into sensors for gravity. The special feature of the proposed experiment is that the source of the gravitational field generated by the ultra-relativistic particles lies mainly in their very high speed – i.e. in their very high kinetic energy – and not in the rest mass energy of the particles. The experiment therefore measures what the gravitational effect of kinetic energy looks like. Does it agree with the predictions of GR or are there deviations? 

Mathematical model shows deviations

The researchers have predicted the acceleration of the test particle and the momentum transfer due to the gravitational field of the passing ultra-relativistic particles in a mathematical model which is based on a modification of GR. The results show that there is a parameter range in which the momentum transfer calculated by the mathematical model deviates significantly from the predictions of GR. This deviation increases with the speed of the ultra-relativistic particle stream.

Fascinatingly, this experiment could actually be carried out with the help of the particle accelerator LHC (Large Hadron Collider), operated by the European Organization for Nuclear Research CERN (Conseil Européen pour la Recherche Nucléaire) near Geneva. At this facility, protons can be accelerated to approximately 99.9999991 percent of the speed of light. What is still missing for the experiment are test particle sensors, that would be installed around the LHC’s beam pipe and react to the protons’ gravitational field. The technical details of installing such sensors are currently being studied.

Quelle: Universität Bremen Center of Applied Space Technology and Microgravity (ZARM)