You can imagine the pivotal moment here, where someone (according to Wikipedia, it was Immanuel Kant, which is a neat fact all by itself) said "hey, that band of faint stars could be a gravitationally rotating disk seen from the inside, and what if those other oblong smudges we see are entire other disks really really far away?"
For residents of our hypothetical planet, that moment, which seems very important to me, would be hard to have!
For residents of our hypothetical planet, that moment, which seems very important to me, would be hard to have!