A Stealth bomber?

Nope, it's Santa's sleigh, one of the engineering wonders of the modern world. And -- with a wink and a smile -- Dr. Larry Silverberg at North Carolina State University thinks he knows how it works.

"Santa clearly is ahead of the curve when it comes to applying advanced scientific theories to his sleigh's design. Children shouldn't believe others who say he isn't real because there's no way he could deliver toys all over the world in one night. There is a way, and it's based on plausible science," says Silverberg, a professor of mechanical and aerospace engineering and a member of NASA's Mars Mission Research Center at N.C. State.

As an academic exercise in fun (and a gift to beleaguered parents), Silverberg and some of his students gathered after class recently and devised these scientific answers to questions long asked about Santa:

How can Santa's sleigh travel around the world in one night, making stops at so many houses? Albert Einstein's theory of relativity proved that under the right conditions, time can dilate and space can contract. It is theorized that annually on Dec. 24, these conditions occur at the North Pole, which is the earth's center of rotation and also a point of convergence of its electromagnetic field. When this happens, a rip literally develops in the fabric of time, allowing Santa to slip through. Until he returns back through the rip, time stands still for the rest of the world. He can take as much time as he wants to deliver the packages, and to us, it seems like it was done in the twinkling of an eye.

How does Santa know where children live, and what gifts they want? Although old- fashioned letters to Santa still work, Silverberg and his students speculate that the Jolly Old Elf also has a strategically placed multigrid receiving antenna system that picks up electromagnetic signals from children's brains. Sophisticated signal processing methods are then used to filter the data and ascertain who the children are, where they live and whether they've been bad or good. This data is transferred to Santa's onboard sleigh guidance system, which uses a computer software program to plan the most efficient route of delivery.

How can one sleigh carry all those presents? It doesn't have to. Thanks to state-of- the-art nanotechnology, which was developed in 1988, Santa can now use a hierarchial distributed mobile manufacturing system to make the gifts on site in each child's home. Silicon chip-based machines, so tiny they can fit on the head of a pin, are loaded with a code containing the child's toy list. Using large-scale algorithms similar to those that make DNA work, the machines literally grow the toys, atom by atom, from bits of snow and soot Santa collects along his route.

Large toys require thousands of nanomachines working in concert and can drain Santa's technological resources, Silverberg warns, which is why children shouldn't expect more than one big gift each year.

How can Santa's reindeer fly? It's in their genes. After centuries of selective breeding and (more recently) bioengineering, the volumetic displacement of their lungs is of such a proportion that when filled with an appropriate mixture of helium, oxygen and nitrogen, they become buoyant. Pulling the sleigh becomes as easy for them as pulling a raft in water.

How can Santa eat so much milk and cookies without bursting? Simple: He only takes one nibble at each house. The remainder is placed in his sleigh's built-in food dehydrator, where it is preserved for future consumption.

What is Santa's sleigh made of? Since it's never been analyzed in a laboratory, we can't be sure. But it likely is made of a Kevlar-like composite fiber encapsulated in an epoxy resin matrix. This would make it very strong, lightweight, durable, and cold-resistant. Anecdotal evidence also supports this theory. "When going through the ionosphere, a sleigh made of this material would glow like a speck of bright red, a sight children and other reliable sources have long reported seeing in the sky on Christmas Eve," Silverberg notes.

Assisting Silverberg in his lighthearted endeavor were: Robert Stanley of Cary, a doctoral student in mechanical engineering; J.P. Thrower of Charlotte, a doctoral student in electrical engineering; Dan Deaton of Tabor City, a senior in mechanical engineering; Charles Grant of Raleigh, a senior in mechanical engineering; and Jeffry Windsor of Raleigh, a doctoral student in mechanical engineering.