!!Ezio's scientific knowledge
When Ezio is disguised as a minstrel, he sings songs about his past adventures. One goes as such:
-->''Cesare, oh Cesare,\\
A man of great depravity\\
Believed himself immortal 'til\\
He had a date with gravity.''
Some people have made the point that gravity wasn't "discovered" for decades more, meaning that Ezio couldn't possibly have known what it was. But we know that he has had possession of the apple for ten years or more. Meaning he could have EASILY learned about it from there.
Or even that the translated word he used in Italian didn't directly mean gravity, but was whatever word they used then for the concept of falling.