Einstein’s equivalence principle can help undergraduates understand gravitational wave detectors
Einstein’s equivalence principle can help undergraduates understand gravitational wave detectors lead image
Following the detection of gravitational waves nearly 10 years ago, physics instructors have worked to explain them in the undergraduate curriculum. Emerging methods for detecting them, however, are becoming increasingly difficult to explain to budding physicists.
Markus Pössel has provided a comprehensive overview for teaching the foundations of gravitational wave astronomy. Starting from Einstein’s equivalence principle, Pössel’s approach shows how gravitational waves affect light, and how current and future detectors put the resulting effects to good use.
“We are entering a golden age of gravitational wave detection, and at the same time, cosmology keeps yielding new findings,” said Pössel. “Making those subjects accessible to undergraduate students is an interesting challenge, and really worthwhile – some of these students might make the next generation of relativistic discoveries!”
Most simplified descriptions of gravitational wave detection focus on laser light measuring the changing size of detectors as evidence for the waves. New results from 2023 demonstrated how the regular radio signals from pulsars can be used as a natural detector as well.
After laying out the fundamentals of gravitational wave physics and how they influence light using the equivalence principle, the paper draws parallels between the expansion of the universe and gravitational wave effects on light.
Pössel concludes by describing how interferometry is used in detectors, such as the Laser Interferometer Gravitational-Wave Observatory (LIGO), and how future detectors — such as the Laser Interferometer Space Antenna (LISA), an international effort slated to launch in 2037 — work.
Pössel hopes to expand his work to orient undergraduates to the practical challenges of detecting gravitational waves.
Source: “Detecting gravitational waves with light,” by Markus Pössel, American Journal of Physics (2025). The article can be accessed at https://doi.org/10.1119/5.0228933 .
