Kant imagined other galaxies long before telescopes confirmed them
In 1755, philosopher Immanuel Kant suggested that some faint nebulae might be enormous systems of stars comparable to the Milky Way. At the time, astronomers did not know whether these cloudy patches lay inside our galaxy or far beyond it. Only in the twentieth century did observations establish that many were separate galaxies. Kant had proposed the possibility long before it could be tested.