Sheldon: Do you want to hear an interesting thing about stairs?
Leonard: Not really!
Sheldon: If the height of a step is off by as little as two millimeters, most people will trip.
Leonard: I don't care. 2 millime--? That doesn't seem right.
Sheldon: It's true. I did a series of experiments when I was 12. My father broke his clavicle.
Leonard: Is that why they sent you to boarding school?
Sheldon: No. That was the result of my work with lasers.