https://phys.org/news/2018-07-milky.html

The land that he described is literally out of this world, and the document bears the title Sidereus Nuncius ("Starry Messenger"). In it, the Italian mathematician and astronomer presents his observations of the satellites of Jupiter, the Earth's moon and also the Milky Way. Until then, their nature had remained a mystery, and had above all been the subject of mythology. The Greek natural philosopher Democritus had already claimed in the 5th century BC that the diffusely glowing strip in the sky – known by the African !Kung bushmen as the "backbone of the night" – consisted of countless weak stars.

After the discovery made by Galilei, however, nearly 150 years would pass before this celestial structure would again became the subject of scientific study. Thomas Wright of County Durham believed that stars were arranged in a flat region similar to a grindstone, which extended over the entire sky. For him, the Milky Way was nothing other than the projection of this grindstone. The German philosopher Immanuel Kant seized on this theory – and came very close to discovering the truth.