SEATTLE - It's an age-old question: If you have to go outside and you don't have an umbrella, will you stay drier walking or running?
Science for more than a half-century has found ways to complicate the matter until two North Carolina researchers settled the question with a highly sophisticated experiment:
One walked in the rain, the other ran, and then they weighed their clothes.
More than logic
The logical theory - run, spend less time in the rain, get less wet - would be true enough if rain landed only on the top of your head and shoulders.
But the problem gets slippery when you consider that you end up running into raindrops, wetting the considerable surface area of your face, chest and leg fronts.
So now you have to factor in how much surface area is exposed for how long - a function of things such as kinematics, relative velocity, vector components and flux.
Lest your mind be shutting down around now, Doug Craigen, a Winnipeg-based physicist, has a calculator on his Web site that will compute all this for you: www.dctech.com/physics/ features/physics-0600a.html.
Here's one scenario:
A 6-foot-tall, 44-year-old with male-pattern baldness and bad knees emerges from a 1977 Volkswagen van in a downpour. He has about 200 yards to cover between the parking lot and his office.
According to Craigen's calculator, the following happens:
As he walks at about one yard per second, his bald spot and other surfaces will be hit by 61.5 milliliters of water - about two ounces - in the three minutes and 20 seconds the walk takes.
Jogging at a 10-minute-a-mile pace, he catches only 40 milliliters of water.
He's actually catching more water per second but comes out ahead by cutting in half the time he's in the rain.
It pays to run, Craigen said, but not as much as you would think:
"Between you and your destination, there's a certain amount of water, and no matter how fast you run, you're going to run into that water."
Trevor Wallis and Thomas Peterson, two runners and meteorologists at the National Climatic Data Center in Asheville, N.C., took a different approach.
Waiting for rain
They measured out a 100-yard track near their office, waited for rain, donned cotton sweat suits and went outside.
Wallis ran; Peterson walked.
They then weighed their sweat suits to see who took on more water. Peterson's weighed 40 percent more.
"To be rigorous, we should have done it 100 times for the statistics," Wallis conceded, "but it was more of a joke than a serious investigation. We never expected the reaction we got. We are both pretty serious researchers."
The results were published in Weather, a peer-reviewed journal.