The ceiling IS the roof.
Henri Gavin, a professor of civil engineering at Duke University, defended MJ's head-scratching, "The ceiling is the roof" quote which he delivered amid a halftime speech to the UNC crowd during their game against their in-state rivals.
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Although Jordan was probably trying to say something along the lines of, "the sky's the limit," the Duke professor told Bleacher Report that MJ wasn't exactly wrong in saying "the ceiling is the roof."
"So the traditional dictionary definition of a ceiling is the surface on the inside of the room," Gavin says. "That's what the ceiling is. The roof is the surface that covers the building. But an arena is one giant room, so the ceiling is the roof."
"If you look at the top surface of the arena from the inside, you would call that object the ceiling," Gavin said. "If you looked at that same object from the outside, you'd call it the ceiling. The ceiling is the roof."
So there you have it, folks. The ceiling is, in fact, the roof.