Judging from the questions my friends and co-workers ask me about the Tour, there's a little confusion about how the Tour de France works as a sporting event, and how Lance is doing. Let me see if I can give you a quick guide to the Tour so far:

I heard Lance lost the yellow jersey today. Can he still win?

Yes. In fact, he probably didn't want to keep it all that much at this point!

The thing about the tour is that it isn't a monolithic competition for the yellow jersey, which is the prize for the leader of the "general classification" (GC), which, with some caveats, is the lowest aggregate time on all stages. Nearly 200 riders started the Tour, nine per team. Most of those are riding in support of their team leaders, but even most of the teams are not trying to win the GC prize.

There's a series of races and goals within the race: winning just one stage is a key goal for many teams. There's a special green jersey for the "points leader," a convoluted contest which is normally won by sprint specialists: they are good at riding with the pack for the entire stage, then sprinting free at the last second to take the win at the finish. There's more to both the points competition and sprinting tactics than I'm explaining here, but you can e-mail me if you care. There are two other jerseys: the polka-dot jersey for the "King of the Mountains", and a white one for best young (born after January 1, 1979) rider; and there is the "combativity" prize, with points awarded by a race jury each day to the rider who is most aggressive (this means participating in breakaways and other actions that tend to drive the race). The most aggressive rider just gets red numbers on his jersey instead of the usual black numbers.

For some of the minor teams in the race, the Tour is a success if they simply manage to participate in a few attention-getting breakaways, which mean lots of TV time even if they get caught before the finish.

But all these other jerseys and suicidal breakaways are so much fuzz to the riders trying to wear the yellow jersey in Paris, where the Tour traditionally finishes. When you hear about other riders wearing the yellow jersey in the first week of the tour (and again, wearing yellow for even one day is a huge achievement for any racer), note that the riders trying to win GC (including Lance Armstrong) are perfectly content with this. The leaders at this point are typically taking the jersey by mere seconds, or else they are riders who will not be a factor in the later time trials and (especially) in the mountains. If you can't climb very well, every mountainous stage (and there's lots of those coming up) is a struggle in which you are trying to stay close enough to the stage winners to make that day's time cut. It is normal for many riders to finish dozens of minutes behind the winners and GC riders.

That said, today's events, in which Thomas Voeckler won the yellow jersey in a huge breakaway, were interesting. On one hand, Voeckler isn't considered a serious threat in the mountains. He rides for a relatively weak team, the French "Brioches La Boulangere" (yep, he's sponsored by a bakery). But thanks to a very aggressive 5-man breakaway aided by bad weather which caused a lot of crashes in the main pack, and a US Postal team that wasn't very interested in working hard today (because defending the yellow jersey can be very difficult, and it isn't part of their plan to have to do so until the big mountain stages), he finished the day over 9 minutes ahead of Armstrong in the GC. This is probably more time than the big riders wanted to give up, and Voeckler may not be a complete pushover in the mountains. The race will be a little more interesting because of today's stage.

Why are the mountains so important?

Because of drafting.

When bike racing on more-or-less flat roads, a rider who drafts another rider uses about 30-40% less energy than the lead rider. This means that two riders working together and taking turns leading and drafting can normally catch a similarly strong solo rider. And with more riders sharing the work, the advantage over one rider or a small group is even greater.

The upshot is that it is very hard to get away on a flat stage because the main pack of riders can usually bear down, work together, and catch back up to your break. Even if only one or two teams, say 8-15 riders, are working hard and taking turns setting the pace at the front of the pack, the rest can draft them as a big bunch, and enjoy a relatively easy ride to the finish. And on most flat stages, that's exactly what happens: a break goes out, a break gets caught. Sometimes, like today, the break survives, but that is rarer than a pack finish.

In the mountains, drafting stops mattering. The steeper the climb, and the slower the riders are going, the less the aerodynamic effects of drafting matter. While the pack can average over 50 km/h on a fast day on the flats, the steepest hills are taken far, far slower. 15-20 km/h even for fast riders is quite possible. If you watch the steep mountain stages, you'll be able to see fans occasionally running alongside the top contenders for a few hundred feet. Note that over those short distances, they can keep up with the cyclists! It gets that slow.

With virtually no drafting, finishing times in the mountains are much more about having strong legs, not being too heavy, and a willingness to endure massive amounts of pain. The pack will split up on each climb, riders will form into many small bunches, and solo finishes become the norm. This is where the riders will finish with minutes separating them.

So Lance is going to win once it gets to the mountains?

Were that it were so simple! Aside from the simple bad luck of possible crashes, illness, or the other bad things that can happen, Armstrong has serious rivals in this race, including Tyler Hamilton and Jan Ullrich. Ullrich is an especially serious rival: he won the last Tour before Lance's run of five, and has never finished lower than second place. In other words, he's lost to Lance a couple of times, but just barely. This could be his year, it could be that Lance is just too old and too tired, or it could be that some rising star (Voeckler?) comes out of nowhere and ends the streak. Five riders have won five tours, including Lance. The four previous winners all attempted to win a sixth tour, and none did.

If Lance does win, then, will he be the best cyclist ever?

Cross-generation comparisons of athletes are always hard. For some critics, Lance's single-minded focus on the Tour de France means he isn't even the best rider right now, though that is the minority opinion.

The Tour de France has become a much more important race than it used to be. Years ago, the other two major grand tours (Vuelta Espana and Giro d'Italia; I'll let you guess which countries) were of nearly equal prominence. But the Tour was still the big race, if only by a little bit, and the Spanish and Italian riders generally wanted to win their home tours as much as they wanted to win the Tour de France.

In some ways, Lance changed that: he is part of a series of riders who have focused more and more sharply on the Tour as an exclusive goal. Although Armstrong races several other events each year, they are generally treated as training and testing for the big event. He also aims exclusively at the yellow jersey, and so does his whole team: no team in the Tour will be as focused on one goal as US Postal. Even rival Ullrich's team, T-Mobile, has a sprint specialist (Erik Zabel) who expects team support for his own goals.

This is in sharp contrast to riders of yore, who would ride many more events with victory in mind, and would even skip the Tour to concentrate on the other two grand tours.

No rider brings up this contrast more than Eddy Merckx. He's one of the five-time Tour winners. In his prime, he actually skipped the event altogether once or twice because he was riding the other two tours that year.

Merckx also contested all of the "Spring classics", races you hardly hear of on this continent, but these are one-day races, mostly in Belgium and the Netherlands, which are prestigious cycling events on their own. Armstrong rarely participates and almost never seriously competes in these early-season events, though some US Postal riders do make these races a major goal.

Merckx was the most dominant rider of his era. He always wanted to win, he always attacked, and he was most amazing cycling machine of his generation. Remember how I talked about all the separate jerseys a few paragraphs back, and how each is contested by a different group of riders? In 1969, Merckx won his first Tour. He also won the points and mountains contests at the same time, the only three-jersey winner ever. In fact, if the young-rider jersey had existed, he would have won that too. He won all three grand tours. He won the Giro d'Italia five times. He won just about everything.

How do you know Eddy was the best? Well, Lance's nickname is "Lance," or maybe "Mellow Johnny" or "Daddy Yo-Yo." Eddy's nickname was "The Cannibal."

Okay, so I can't get up at 6AM PDT every morning. Which stage should I skip work and sleep to watch live?

First, I want to say something in favour of the 500-channel universe and OLN TV's coverage of the Tour. Not so long ago, watching the Tour on TV meant an hour of highlights once a week narrated by college basketball experts. OLN practically becomse the Tour de France network, including hours of live broadcasting, repeats, follow-ups, and a mid-afternoon roadside travelogue show. Some of this is very stupid. Sometimes the commentators say stupid things, and they have a few commentators who don't really know much about cycling. It's still amazing, and the pictures speak for themselves.

That said, here's the deal: the race will probably be decided in the mountains, and even if it gets decided by the time trial on July 24, TTs are boring to watch on TV unless you're a real bike nerd.

The first really interesting mountain stage is on Bastille Day, July 14. There are eight classified climbs on this longest stage. It probably won't be decisive, but this will be the first hard mountain test for all the big teams and riders.

Stage 13, though, that's where the fun begins. Seven climbs, including a mountaintop finish, which means there will be big time gaps. Get up early on Saturday, July 17.

Those are the early, hard mountain stages coming up next week. The week after that features more suffering still, and I'll focus on those stages then.