With Einstein on crooked paths
Annual fundraising project supports search for gravitational waves deflected by gravity
Gravitational waves and gravitational lensing are two of the surprising predictions of Einstein’s general theory of relativity. Each of them individually is well studied and widely used in modern astrophysical research. A new project at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in the Potsdam Science Park will now combine the two into a novel method for exploring the Universe. The project is funded by the Supporting Members of the Max Planck Society through the Society’s Annual Donation Project. This project has received around 20% more in donations than those in previous years.
Gravity deflects the path of a ray of light in such a way that multiple images of the same object can sometimes be observed in our Universe. This effect, called gravitational lensing, is a prediction of Einstein’s theory of relativity and has since become an important and well-studied tool in astrophysics with numerous applications. They are used to find planets around other stars or to map out the distribution of the otherwise invisible dark matter.
Gravitational waves are ripples in the fabric of space-time. They are created when massive objects are accelerated and travel through our Universe at the speed of light. Since 2015, astronomers have been measuring gravitational waves from mergers of compact (small and massive) objects, such as colliding black holes and neutron stars. They have used these waves to study more than 90 such mergers and their astrophysical properties, and to identify nearly 200 other possible mergers.
Like light, gravitational waves are deflected and sometimes split into multiple signals. Is it possible to find such gravitational waves deflected by lensing? Miguel Zumalacárregui and his team at the Max Planck Institute for Gravitational Physics in Potsdam have developed a mathematical description for the deflection of gravitational waves and efficient software to calculate these effects. It accurately predicts them within a fraction of a second.
“My work aims to study the deflection of gravitational waves instead of light, because deflected signals are also magnified, this will allow us to detect signals further away than is normally possible,” explains Miguel Zumalacárregui. “In addition, gravitational waves distorted by intervening objects will help us better understand the distribution of ordinary and dark matter in the Universe.”
Each year, the Max Planck Society’s Supporting Members donate to a featured project that would otherwise not be possible. In 2025, they generously support Zumalacárregui’s research on deflected gravitational waves. This project has received around 20% more in donations than those in previous years. It will allow the group leader to hire a postdoctoral researcher to work in his team for three years.
Zumalacárregui also plans to make these exotic and fascinating phenomena of Einstein’s theory more accessible to the general public: “Thanks to the generosity of the donors, I’ll be able to invest some of the funds to produce outreach videos that cover the intersection of gravitational waves and gravitational lensing.” The videos will also be part of Einstein Online, an outreach web portal of the Max Planck Institute for Gravitational Physics dedicated to Einstein’s theory of relativity.
