reference frame

Spacetime provides a powerful description of how events happen: how they are ordered relative to one another, how sequences of events are measured to unfold and how lengths are measured in different reference frames.

In the electron's reference frame, the laser intensity appeared to be about 50% of the Schwinger limit, triggering nonlinear QED phenomena.

However, the notion of continental groupings as a meaningful reference frame for understanding human biological variation persisted.

For decades, radio astronomers have tracked minute changes in Earth’s surface rotation—the length of a day—against a cosmic reference frame: the fixed position of distant cosmic beacons called quasars.

This was achieved by Gaia tracing its movement against the stars, using the "fixed" points of light from very far-away galaxies as a reference frame.