This Perspectives article argues that measurements of gravitational waves can be used together with particle physics experiments to learn about fundamental physics. The authors review how different kinds of gravitational-wave signals carry information about dense matter, dark matter, and processes in the very early Universe. They emphasize that the next generation of detectors will open new ways to test ideas that are hard or impossible to reach with particle colliders alone.

The paper explains several concrete links. Ripples in space and time called gravitational waves (GWs) from neutron-star mergers are sensitive to the behavior of matter made of quarks and gluons at very high density. Signals from black-hole mergers can probe some dark-matter scenarios. A stochastic gravitational-wave background (SGWB) — a faint, persistent hum of many unresolved sources — could come from a first-order phase transition in the early Universe. Such a transition would leave a GW signal that can be sensitive to energy scales around the teraelectronvolt (TeV) range, which is the target of collider projects such as the High Luminosity Large Hadron Collider (HL-LHC) and proposed future colliders. The article also notes recent results from pulsar timing arrays at frequencies near 10^-8 hertz, which may be explained by supermassive black-hole binaries but do not yet rule out other early-Universe sources.

The authors describe how upcoming instruments fit into this picture. The Laser Interferometer Space Antenna (LISA) is a planned space mission that will look for GWs in the millihertz band (about 10 microhertz to 1 hertz). LISA will consist of three satellites forming a triangle separated by millions of kilometres and will be sensitive to supermassive black-hole mergers, extreme mass-ratio inspirals, many compact binaries in our galaxy, and to potential TeV-scale phase transitions. On the ground, proposed third-generation detectors such as the Einstein Telescope and Cosmic Explorer aim to improve sensitivity by more than an order of magnitude over today's detectors and should see many more stellar-mass black-hole and neutron-star mergers.