Three lamps that had walked

Edmond Halley sits with Ptolemy and with newer European measures. Three bright stars have changed their places relative to the others since antiquity. Sirius. Arcturus. Aldebaran. He publishes the notice in 1718.

This is not a guest. The lamps were always there. They have drifted. The eighth sphere, already wounded by new stars, is no longer a rigid shell.

Proper motion is the slow slide of a nearby star against more distant ones. Arcturus is close, as stellar distances go, and moves quickly on the sky. Halley could not yet turn the slide into a distance. Bessel will, with another star, in 1838.