I was once on a plane taking off from Mexico City. One of the flight attendants opened and closed the door to make sure it was locked properly. The guy next to me said he was glad she closed the door, because “our heads would have popped when we got to altitude.”
“Really?”
“Yeah. I once had a bag of chips in my car, and it popped open just getting here from Acapulco.” (Acapulco is sea level. Mexico City is 7400 feet above sea level.) “Less pressure means air expands,” he confidently added.
“And you think our heads are filled with air?” I asked.
He seemed puzzled, and thought about it for a second. “Well, you tell me what would happen,” he said.
I had to give a 40-something year old American businessman, a “titan of industry,” a lesson in physics and anatomy and physiology.