What if the Library of Alexandria had survived? The ultimate demise of the Library of Alexandria and its Hellene scholarship is usually correlated with the murder (motivated by the Pope) of Hypatia, stripped naked in the streets of Alexandria with her flesh scourged from her body by Christian hands and fingers while being dragged to her final death by being burned alive. The final loss of Hypatia to scholarship and advancement of knowledge marked the beginning of the end of humanist Greek science and mathematics until it was resurrected in Europe during the Renaissance, the Age of Reason, and the Age of Enlightenment, all of which the Catholic Church continued to strenuously oppose.
What if the Spanish Inquisition never existed? The Domicans who ran it were charged by the church as the protectors of doctrine (including scientific theories motivated by scripture). Those who questioned the doctrine were automatically wrong and were tortured until they renounced their error. Catholic apologists have argued that only a few scientific books were on the banned list, and only one scientist was killed, therefore, the Inquisition should not have had a chilling effect on scientific advancement. I'm amazed that they could argue that with a straight face.
It is true that monks preserved some of the knowledge of antiquity through the Dark Ages, but while they were busy copying manuscripts, how much new scientific research occurred? Steeped in dogma as they were, was there any motivation to investigate the universe for what it actually was rather than what the Bible said it was, particularly if the Inquisition awaited for those who taught theories contrary to church doctrine?
I have to wonder whether we would be colonizing other worlds by now if our world had not suffered under the grip of Christianity (and Islam) for so many centuries. Seth MacFarlane, writer of Family Guy, obviously had similar thoughts.