Europeans forgot a lot during the Dark Ages. We owe a debt of gratitude to the Muslims of the time for keeping much of the ancient knowledge alive, from mathematics to optics to medicine to cartography, and so on. Add astronomy to that list, as well. It's no coincidence that many of the brighter stars in the sky have Arabic names.

That said, there was a lot of stupid back in the day, too. And a lot of that is still around.