Wind tunnel for car testing.

iStockphoto.com/Kiyoshi Takahase Segundo

­In the world of stock car racing, it all comes down to one factor -- speed. Since the beginning of the sport, drivers, owners and the corporations who make the cars have been searching for ways to go around the track just a little bit faster. Do you know what's slowing them down? The answer is blowing in the wind …

As a car moves through the air, friction between the automobile and the air molecules creates a force called drag. If you've ever stuck your hand out the window of a moving car, then you already have experience with this force. When you tilt your fingers down, the air moving past your hand will push it down. That's drag and it slows you down -- a lot. It's all part of a branch of mechanics known as aerodynamics. When you hear a car referred to as aerodynamic, it simply means that it has been built to minimize friction with the air [source: American Heritage].

­So how do we study this interaction between a moving car and the air -- especially when the car we're trying to study is averaging 160 mph (258 kph)? We certainly can't run beside it or drive next to it while making observations and recording results. This isn't practical or safe. That's where wind tunnels come into the equation. Instead of driving a car 160 mph, scientists can blast air past a stationary car in a controlled environment and conduct accurate studies.

Wind tunnels can provide stock car drivers with a huge amount of information on how to make their cars aerodynamic. They help answer questions about how the cars should be shaped, what angle their spoilers should be set at, and where the air inlets should be placed [source: Aero Warriors]. Wind tunnels also eliminate other variables that can affect results, such as bumps in the road or inclement weather. When it comes to aerodynamic development, wind tunnels are hard to beat [source: Hilton Racing].

­It's a good bet that with their ability to provide accurate and efficient results, wind tunnels will play a central role in the advancement of aerodynamic design for years to come.