Winemakers love technology, so why are they watching for comets and calculating the cycles of the moon?

At this time of year, some winemakers in Burgundy say, the season's tasks are best performed under a rising moon. Many of these vignerons will be leaving their beds long before dawn. And when they start work, they'll strip naked.

Now this scene may sound as if it came straight from one of those mud-caked French movies--Jean de Florette, say, or The Return of Martin Guerre--that will use even the most thinly disguised pretext to get Gérard Depardieu out of his britches. But, believe it or not, nudity has become a cutting-edge, ultrafashionable winemaking technique. And you're as likely to see it in California, Australia or New Zealand as you are in a small Burgundian village.

Something weird is happening in the world of wine. Until quite recently, producers would boast about their stainless steel tanks, pure yeast strains, high-tech filters and chemicals, and, above all, their lengthy scientific training. Today, however, many an ambitious winemaker will be more eager to tell you about the amount of time he spends plowing his fields with a horse or calculating the cycles of the moon; he may even tell you about achieving excellent results with a form of pigeage that calls for plunging completely naked into an old-fashioned open-top fermentor.

Are winemakers simply becoming more credulous? Advocates of pigeage and lunar viticulture don't think so, arguing that over the past 20 years mainstream winemakers have added a whole range of techniques and approaches that not too long ago were considered irrational. The philosophy that motivates many of these new-wave peasant winemakers is biodynamism, a system of organic agriculture based on theories developed by Rudolph Steiner, an Austrian educator who died in 1925. Biodynamism considers plants to be part of a total system that embraces both the soil and the cosmos. Biodynamic viticulture has taken rapid hold in France, with believers in such esteemed places as Domaine Leflaive in Burgundy and M. Chapoutier in the Rhône. It's also winning converts at some of the top wineries in the New World.

Pigeage, for example, is a practice that I thought had died out in France years ago. After all, the naked men depicted stomping grapes in my copy of Hugh Johnson's World Atlas of Wine are definitely sporting haircuts dating back to the Fifties. Yet when I visited the small-scale growers of southern Burgundy and the Rhône, it turned out that this method was, so to speak, alive and kicking.

It's a well-accepted fact that bare feet are ideal for crushing grapes, leaving the grape pips and their bitter oils intact. However, according to Olivier Merlin of Domaine du Vieux Saint-Sorlin (one of wine critic Robert M. Parker, Jr.'s favorite Burgundy growers), more complete body contact is important throughout fermentation. While workers who step into a tank with bare legs can break up the floating "cap" of skins, Merlin says full-body immersion is the best way to find areas inside the tank that are overheating. Besides, he adds, the sensation of being naked inside a tank is quite pleasant: the temperature of fermenting wine is comfortably close to body temperature, and the rising bubbles of carbon dioxide make the vessel feel a bit like a Jacuzzi.

Pigeage has not only survived in the Old World but has been adopted in the New. The producers at Foxen Vineyard in Santa Maria, California, rely on it. So does Gary Farr of Bannockburn Vineyards in Geelong, Australia, who makes one of the country's most expensive Pinot Noirs. Like many of the New World's new-wave peasant winemakers, he is directly imitating what he saw in Burgundy at the renowned Domaine Dujac. "I'm sure that if I had an enology degree I would have been far less receptive," he maintains. "As it was, I just went for it head on."

Although Farr practices pigeage, he doesn't schedule his work according to an astrological calendar--yet. Many of his peers do, and they are not just in Burgundy. In Bordeaux, winemakers don't hesitate to attribute good vintages to such cosmic influences as the Hale-Bopp comet, which was visible during the start of the 1997 growing season. The newsletter of a local growers' federation, celebrating the approach of Hale-Bopp, noted that comet years have often been associated with great wines. (The relatively modest success of the 1997 Bordeaux wines, which were considered good rather than great, may have caused more than a few winemakers to question their faith.)

Belief in the power of the moon is startlingly widespread in the wine world. Telmo Rodriguez, a young winemaker at Rioja's Remelluri bodega who trained at Bordeaux University, told me that it was his family's custom to prune young vines when the moon was waxing and to trim old vines when the moon was waning. In the cellars of many Beaune wine shippers, it is considered anathema to rack wine (siphon it from barrel to barrel) when the moon is waxing, for the lunar pull is thought to turn the wine cloudy. Some professionals avoid tastings when the moon is full, as the wine is said to "close up," or become less expressive.

One of the best examples of once-weird winemaking techniques that are increasingly commonplace is wild fermentation, that is, allowing fermentation to begin spontaneously by permitting the juice to come in contact with yeasts in the air rather than inoculating it with a commercial yeast strain. Though all fermentations were once done with wild yeast, around the turn of the century The Geisenheim Research Institute in Germany isolated new yeasts that could be counted on to begin and end fermentation in a predictable way. A goal of the creation of these commercial yeasts was the elimination of hydrogen sulfide, or H2S, the notorious rotten-egg gas.

Now such top producers as Peter Michael Winery in Sonoma are convinced that wild yeasts make more complex-tasting and thus greater wines. Even big outfits like Penfolds in Australia are currently experimenting with this technique, their winemakers seemingly unfazed by hydrogen sulfide. "Yes, H2S is a bad wine fault," acknowledges Richard Gibson, Penfolds's group technical manager. "But in tiny quantities it can create complexity."

Another practice that might once have been questioned but has since gained wide acceptance is a preference for wooden barrels over stainless steel tanks. The producers at Robert Mondavi's Oakville winery have begun replacing stainless steel fermenting tanks with wooden vessels, which are theoretically less hygienic. Why? Mel Knox, a consulting winemaker, barrel broker and coauthor of an influential paper on the science behind this practice, discovered that people simply prefer the way wine tastes when it's been fermented in wood. Fetzer and Kendall-Jackson are two well-known makers of premium California wines that attribute their success to barrel fermentation. They also use a number of other old Burgundian techniques, including maturation on the lees, which is the practice of allowing wine to remain in contact with spent yeast cells.

Randall Grahm, the original Rhône Ranger and founder of Bonny Doon Vineyard in Santa Cruz, claims that he was one of the first Californians to take traditional French winemaking techniques seriously. Grahm adopted his outlook at the University of California at Davis in the Seventies. "I was very immature," he admits. "I'd take what I thought was the French position, even if I didn't really understand it. It was a reaction to the old guard at Davis, who were frankly contemptuous of the traditions of European winemaking: old vines, low yields, wild yeast fermentations, maturation on the lees. They thought you might as well just add vinegar."

This may sound like a grandiose comparison, but wine, like the human brain and the structure of the universe, has complexities that researchers are only now beginning to appreciate fully. "Science can analyze and explain," notes Olivier Merlin, who spent two years in California before settling in Burgundy. "What it can't do is replace 20 centuries' worth of human observation."

Patrick Matthews, a London-based wine writer, is the author of The Wild Bunch: Great Wines from Small Producers (Faber), which was named the 1998 Glenfiddich Drink Book of the Year.