What were the two greatest contributions the crusades made to future civilization

Is this science I don't like science

It should be at the center of any map going vertically: the prime meridian, as it passes through greenwich,  england, is considered 0 degrees longitude

Bob: coke is baby pandas.jim: what? how do you figure that coke is baby pandas? bob: because this book says so.jim: how do we know the book is correct? bob: because it says that coke is baby pandas.jim: how does that prove the book's accuracy? bob: because it's statement involving coke and baby pandas is correct, therefore it is accurate.jim: how do we know that it's correct? bob: because we have concluded that the book is accurate, and therefore the statement is correct.therefore, coke is baby pandas.