Style Guide: The Correct Length of a Man’s Tie

I have a professor that wears his ties several inches above his belt. To me it looks horrendous. I asked my lady friend sitting next to me what she thought. She told me that she agreed that wearing a tie a few inches above the belt does not look appealing but her ex-boyfriend had told her that is how it is supposed to sit. However, I’ve been told and have been adhering to the practice that ties should fall between the top and bottom of my belt buckle. Apparently, among men, if asked, there is some disagreement on this, but according to my internet research the correct length of a tie is…drum roll please… that the tie should indeed fall at the belt (between the top and bottom of the belt buckle), not several inches above it.