This is a myth. There were many, many other excellent libraries around the world when the Library of Alexandria was burned down. It contained few if any unique

This is a myth. There were many, many other excellent libraries around the world when the Library of Alexandria was burned down. It contained few if any unique works, and even those that may have been unique wouldn't have held details of unrecoverable technology. It was a great loss from a cultural knowledge standpoint, but it's not as if the sum of human knowledge literally went up in smoke. It's more akin to what ISIS is doing right now.