38 seconds. That's all. That's the entirety of Lance Armstrong's lead ahead of Danish cyclist Michael Rasmussen in the Tour de France. But what does that mean? Exactly how big of a lead is that? Let's go to the slide rule.

This year's Tour has so far been one of the fastest in history, averaging over 45 kilometers an hour. At that rate a 38 second lead amounts to 475 meters or almost 1500 feet. Pretty big, right? Not so fast. When racing in anger, the peloton can crank up to 60 KPH which converts a 38 second advantage to a lead of more than 630 meters and on a decent where racers routinely fly down the mountain at more than 100 KPH Lance would have a huge lead of more than a kilometer.

Those are nice figures, but they don't tell any of the story, because the Tour de France is not won or lost on the flats or on the descents. It is won and lost in the mountains. In the mountains, the pace varies but let's for arguments sake, say that the average is 20 kilometers an hour. At that pace Armstrong leads Rasmussen by a mere 200 meters. It's nothing. Rasmussen in the current King of the Mountains leader, so we know he can climb. So for Lance to win he needs to keep Rasmussen at bay in the next few stages until the TdF flattens out on the way to Paris. If Armstrong can put some time between him and the Dane, all the much better.