The Milky Way is a phenomenon of the upper terrestrial atmosphere rather than the combined light of distant stars.

This history contains a particularly good scientific detour.

Before Aristotle, some Greek thinkers had already proposed explanations connecting the Milky Way with stars. In Meteorology, Aristotle reviews rival ideas and specifically rejects the proposal that its light comes from innumerable imperceptible stars.

He instead fits the Milky Way into his own physical system. The motion of the heavens, he argued, continually excites combustible material in the upper terrestrial region. The Milky Way is therefore a persistent “fringe” associated with the great circle where stars are densest, making it a meteorological phenomenon in his system.

That explanation had an advantage: it connected the Milky Way to Aristotle’s broader accounts of comets, meteors, air, fire, and the division between the changing terrestrial realm and the eternal heavens.

The telescope changed what could be observed. Galileo reported in 1610 that the Milky Way’s whitish glow broke into a vast multitude of stars too faint to distinguish with the naked eye. Modern astronomy goes much farther: the Milky Way is a galaxy roughly 100,000 light-years across containing on the order of hundreds of billions of stars.

The striking part is that an earlier stellar idea existed, was rejected by a more influential system, and was later revived in a far richer observational form.