reference frame

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.

It said: "They are much more than a convenient geographical reference frame. They are fundamental to our notion of what our country is and of our own place within it."