How do black hole mergers trace back to their cosmic origins?

Researchers developed a shortcut to interpret flexible models of black hole merger rates without reprocessing thousands of gravitational-wave detections. By fitting physics-based progenitor models to existing data-driven merger-rate measurements, they found that black hole pairs form in environments chemically different from where most stars form, with formation rates steeply climbing toward lower redshifts. The method also exposes where current models break down, flagging tensions the standard approach would hide.