"Is that like sleep?" one of the scientists asked.
"No, no," the traveler replied. "You know, fly through the air, like a bird."
"And what is a bird?" someone asked. And so the traveler began to explain about flight and what an airplane was and how it flew from one place to another. The room became very quiet, and the expressions on the faces of everyone present darkened.
"Does he expect us to believe this?" one man whispered to another.
"Well, you know what liars travelers are," someone else added.
Finally the host spoke up, slightly embarrassed and slightly indignant.
"If this is your idea of a joke," he began, but was interrupted by the surprised traveler.
"Why, it's no joke at all. People fly all the time."
"I am sorry that you so much underestimate the intelligence and learning of your audience," said a professor across the table. "That a person could enter some metal device—like a car with fins—and rise into the air, and be sustained there, and move forward, why that clearly violates everything we know about the law of gravity and the laws of physics. If we have learned anything from a thousand years of study of the natural world, it is that an object heavier than air must return immediately to earth when it is tossed into the sky."
"Hear, hear," two or three people muttered.
"Now, if you perhaps mean that these 'airplanes,' as you call them, are somehow flung into the air for a short distance and then fall to the ground, well, then perhaps that would be possible." The professor looked expectantly and a bit condescendingly at the traveler, hoping that the man would take this face-saving opportunity.