A guy goes skydiving for the first time and is surprised to see a blind man climbing into the plane. He's wearing the full parachute gear so he's obviously not just along for the ride. The guy asks him, "Excuse me, but are you actually jumping today?"
The blind man says, "Oh yes, I come here most weekends. I really enjoy the feeling of the wind rushing past my face!"
The guy says, "If you don't mind me asking, how do you know when you're near the ground, so you can get ready for landing?"
The blind man says, "It's easy. I just prepare myself when the dug's lead goes slack!"