Imagine sitting down to Christmas dinner -- roast bird, glittering tree, stockings hung by the chimney with care -- when your dinner partner gestures to the turkey thigh on your plate. Did you know, he asks, that the leg meat is dark because it contains myoglobin, an oxygen-storing molecule that a turkey needs in its muscular legs but not in its lazy breast? Game birds, on the other hand "spend more time on the wing, and their breast meat may be as dark as their drumsticks, seasoned with myoglobin throughout."
Oh yes, he goes on, and that dreaded plum pudding is a descendant of "frumenty, a type of porridge made from hulled wheat spiced and boiled in milk," while the brandy sauce that makes it edible is of "huge interest to surface scientists" because of the unusual way the molecules bind together. As for the role of the chimney at Christmas, some psychologists believe it is a metaphor for the vagina: One reason people become depressed at Christmas may be that Santa's descent revives memories of their birth traumas. If this is your idea of great holiday chitchat, Roger Highfield, the science editor at London's Daily Telegraph, has written the book for you.
"The Physics of Christmas: From the Aerodynamics of Reindeer to the Thermodynamics of Turkey" is a collection of short, bright essays that attempt to explain by means of science -- very broadly defined to include anthropology, psychology and sociology as well chemistry and biology -- all the wacky things people do during the holidays. No subject is too small for Highfield's enthusiastic scrutiny. He devotes one essay to the reasons Brussels sprouts are bitter; another to the architecture of snowflakes; yet another to the biology of reindeer.
Sampled in small doses, these essays can be fascinating. You may have some dim notion that Santa Claus harks back to St. Nicholas, a holy man from the coast of Turkey. It is less well known that some academics posit that his suit is red because people liked to ingest psychedelic toadstools -- "the recreational and ritualistic drug of choice in parts of northern Europe before vodka was imported from the East." Santa's vivid robes, Highfield writes, are thought by some to "honor the red-and-white dot color scheme of this potent mind-altering mushroom." It will be a long time before I forget that the Lapps of northern Scandinavia -- who pulverize reindeer horns and market the stuff as an aphrodisiac -- actually have a genetic mutation rendering some of the men "unusually virile." Or that a cancer research organization has found that Christmas is the only meal of the year at which most British children eat sufficient amounts of vegetables.
But read more than one or two of Highfield's pieces at a time, and you may find yourself reaching anxiously for another egg nog. Highfield is an engaging writer, with an obvious and endearing passion for his subject. But what he has assembled in this pretty volume is an intimidating mountain of random scientific trivia. Taken as a whole, it is more exhausting than explanatory. Like Christmas cheer -- "the fermentation of fruit and grain by the activity of fungi called yeasts" -- "The Physics of Christmas" is best enjoyed in moderation.