reference frame

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.

It was the basis of a brand-new celestial reference frame, a fixed, imaginary grid against which everything else moves, akin to lines of latitude and longitude on Earth.