“That's the difference between theory and experiment,” responded the nonchalant physics professor as he entered the class.
“I have no idea what that means.”
The professor sighed. “Okay, consider it this way; light travels faster than sound, so a person can appear smart before you hear them speak.”
“I don’t understand that either, but I know I don't deserve zero on this test!”
“I totally agree,” smiled the professor. “But that’s the lowest score I could give you.”