Destruction of Persepolis, Burning of the Library of Alexandria, Sack of Baghdad. Did we truly lose so much sciences from these tragedies? Or is it an exaggeration to say that we have been “held back” scientifically from these events?

by conbutt
cchiu23

here's a great answer on the library of alexandria

https://www.reddit.com/r/AskHistorians/comments/5t6op5/facts_about_the_library_of_alexandria/ddkr2h6/

credits to /u/xenophontheathenian

on baghdad

https://www.reddit.com/r/AskHistorians/comments/4v6cq7/what_was_the_impact_on_the_muslim_world_of_the/

https://www.reddit.com/r/AskHistorians/comments/3uxtai/how_important_were_the_mongol_invasions_to_the/

credits to /u/rakony for these two

not sure about persepolis tho