"How many balloons does it take to fill a professors office?" read a piece of paper stuck to John Ross Buschert's office door on Monday.

The answer "720" was scrawled underneath the question in ballpoint pen. Buschert's office was filled halfway to the ceiling with birthday party balloons of all colors.

The question on the door was of a classic physics genre called "Fermi questions," named after Enrico Fermi, an Italian physicist. Fermi questions address problems that can be solved more than one way, and have no absolutely correct answer. Buschert, professor of physics, asked his students to solve the balloon question on a quiz last semester.

Though Buschert doesn't know who filled his office with balloons, he isn't completely clueless. "I'd ask Steven Cress or Jacob Brenneman," Buschert said, stifling a laugh. "Or maybe Noah Weaverdyck."

All three students deny involvement.

Buschert wan't offended by the practical joke, and spent a portion of Monday afternoon working at his computer and taking phone calls in his office, nearly over his head in balloons.