On the 'Late Show' (weeknights, 11:35PM ET on CBS), David Letterman and guest Harrison Ford started with a debate about flying high. Then they ended up in a debate over their relative heights.

Ford began telling the host about a recent blimp ride that he had taken with his family. The actor is a well-known aviator; he flies airplanes and helicopters. (He once rescued a stranded hiker from the air, and also crash-landed a helicopter.)

But when Dave expressed interest in Harrison's blimp flight, the actor growled this in response: "[Blimps are] really boring." Okay, we can see how floating in a huge balloon might be less fun than messing around in a helicopter.

Dave tried to stand up for airships, saying that dullness was the "charm" of a blimp ride. "It's boring!" Ford said. The pair weren't seeing eye-to-eye on the issue. But in the midst of their blimp-related disagreement, Ford suddenly perked up ... by noticing that he wasn't really "up" after all. It seemed that Letterman was towering over him from his position behind the desk.

"How come you're so much taller than I am?!" he asked the host. "Was it always this way?" In response, Letterman challenged the actor to stand up and compare heights. Who would win? If the two men tied, then they would literally able to see eye-to-eye with each other. On the other hand, if Dave was the victor, his height advantage would merely give him extra time to stare down at Mr. Ford's really ugly socks.