The Building Speed Blog

The Science of Fast

The NASCAR Vortex Theory

The NASCAR Vortex Theory says that cars racing around an oval track create a rotational disturbance that repels oncoming storms. Truth? Or Myth?

What’s a Vortex?

A vortex is a region in a fluid (and remember: air is a fluid) where the flow revolves around an axis line. A physicist or engineer represents a vortex with vectors, where the shorter vectors mean the fluid is moving faster. You’re looking at the vortex below from the top. The axis about which everything revolves is coming out of your screen.

A vector diagram of a vortex field

FACTOID: The plural of vortex is vortices OR vortexes. Either one is right.

Scientists use vortices to describe lot of things including

Vortices in Aerodynamics

Vortices are also important in aerodynamics: they create drag and lift — in planes and race cars.

A NASA image showing the vortex off the wing of an airplane

Vortices in Nature

But you see them pretty much everyday, too. For example, when you pull the plug in a drain and the water runs out…

A beautiful photo of water draining.

Or when you flush the toilet

A toilet flushing

You’ve probably heard that water drains in different directions in the Northern and Souther hemispheres; however, toilets use jets of water to flush, so the direction they flush depends on the toilet design, not the hemisphere. Similarly the shape of a sink and how you remove the plug can change the direction a sink drains. A definitive experiment was performed and the video is well worth watching.

The Vortex Effect is Real

Aerodynamics is critical to racing, but there’s one thing that’s even more critical to racing: weather.

The Coriolis effect is a force related to the rotation of the earth. The Earth is bigger at the equator than the poles. A spot on the equator moves at 1,040 mph, while a spot close to the axis of rotation moves 0.00005 mph.

If you stand at the Equator and launch a ball to someone in Kansas, the ball will land to her right: she’s moving slower than you are. This effect was first described in 1651 to explain why cannonballs fired a long distance missed their marks. My father used to tell me about his time at Fort Lewis learning to calculate trajectories using a slide rule to account for the Coriolis force in calculating munitions tracks.

Size and Speed

The equations for the Coriolis force are complicated, but here’s all you really need to know:

  • The bigger the distance, the bigger the Coriolis force.
  • The higher the speed, the larger the Coriolis force.

Jupiter has the fastest rotation in the solar system. One day on Jupiter is about 10 hours. The Coriolis force is so strong that it transforms north-south winds into east-west winds, with speeds of up to 380 miles per hour. This wind pattern creates belts of clouds and the boundaries between those belts are very active storm regions. The Great Red Spot is one of those storms.

The bands on Jupiter are shown. They're due to the Coriolis Force, as is the Great Red Sport

But we’re not racing on Jupiter. So what — relative to the planet Earth — can we consider “big” and “fast”.

Weather systems.

A NASA image of Hurricane Irene from 2011

Hurricane Irene was about 510 miles in diameter, with is about 1/3 the size of the U.S. The inner 140 miles were hurricane-force winds; the rest were ‘merely’ tropical-storm force. It did 14.2 billion dollars of damage.

In the Northern Hemisphere, hurricanes rotate clockwise. In the Southern Hemisphere, they rotate counter clockwise. Coriolis forces are responsible for hurricanes, tornadoes and cyclones, as well as everyday weather trends, like the trade winds.

The ‘Vortex Theory’ of the Coriolis Force is unquestionably real.

Is the NASCAR Vortex Theory Real?

So if the circling of the Earth can cause big-scale effects like tornadoes, then is it possible that the circulation of very fast cars about very big speedways might be able to cause similar effects and cause storms to veer away from the track?

Daytona International Speedway is the biggest of ‘big tracks’ and the speeds reach 200 mph. But that’s pretty much nothing compared to a tornado.

But what about a smaller storm?

According to the National Weather Service, your garden-variety storm is 15 miles in diameter and lasts an average of 30 minutes. Daytona’s effective diameter is about 0.8 miles. Even Daytona isn’t big enough to affect the weather. And if it can’t happen at Daytona, it won’t happen at Martinsville or Bristol, which are tinier and smaller.

But I’ve Seen It!

We all remember times in which it looked like it was going to rain, but then the race started and the race held off. If you collected systematic data, you’d find just as many cases of a race starting, then being called because of rain. (Like last weekend at Dover.) As Chad Myers, a CNN meteorologist with a background in motorsports broadcasting says:

“Considering how much rain we’ve had and how many races have been rained out, if this theory actually worked you’d never rain a race out. You can’t pick and choose when it works and when it doesn’t.”

Chad Myers via Turner Sports Interactive

Then Why Do They Keep Talking About The Vortex Theory?

A photo montage of DW creating a vortex at a track.

‘The Vortex Theory’ has become NASCAR’s version of the catch phrase, the same way ‘Dy-no-MITE!’ and “NaNu NaNu” became catch phrases in the 70s and 80s. People picked up on the phrase and so Darrell Waltrip kept using it.

A DW tweet about The Vortex Theory

Just like those catch phrases from the 70s drove my parents nuts, the Vortex Theory drives a number of NASCAR people nuts.

Jeff Gluck's tweet expressing frustration at the Vortex Theory

And just like we used those phrases even more once we realized it annoyed our parents…

Mike Joy's tweet trolling Gluck

I am sure that Mike Joy knows better. Larry McReynolds, with his interest in the weather, definitely does. So it’s mostly tongue-in-cheek; however, there are some downsides to pulling this out every time it rains.

The biggest downside is that there are some people who believe everything they hear. Just visit the r/NASCAR site for examples.

The second downside is that most people outside of NASCAR don’t realize it’s an inside joke. Combine that with their stereotypes of NASCAR fans and, as one fan complained on Reddit, “it makes us look like hillbilly rubes.”

Maybe we should let the concept leave with its originator.

So There’s No Such Thing as ‘The Vortex Theory”?

Actually, there is.

It’s also wrong.

Rene Descartes — the ‘Cogito Ergo Sum’ (I think, therefore I am) guy — came up with a theory about how the universe worked and called it “The Theory of Vortices”.

Descartes postulated that space was entirely filled with matter (in various states) whirling about the Sun like a vortex. You see, Descartes died in 1650. Little Isaac Newton was just seven years old and the theory of gravity was still thirty-seven years away from publication. Despite Newton’s convincing arguments, the French championed Descartes’ theory for nearly one hundred years after Newton showed it was impossible.

Is the Coriolis Force Why We Turn Left?

The Coriolis force makes things circulate oppositely in the Southern Hemisphere than the Northern Hemisphere, so someone always wants to ask if they race in the opposite direction in the Southern Hemisphere.

No.

  • There are a lot of clockwise tracks (horse and car) in Europe.
  • About half the horse tracks in Germany are clockwise and half are counter clock-wise.
  • In Australia, horses race counterclockwise in the states of Victoria, South Australia, Tasmania and Western Australia, but clockwise in Queensland and New South Wales.
  • Formula One has historically raced on both clockwise and ‘anti-clockwise’, as they say in Europe, tracks.
  • In 2014, the Indy 500 ran counter clockwise and the Grand Prix of Indianapolis, at the road course, was clockwise.

So We Could Just Decide to Turn Right?

Although we turn left by tradition, most tracks are designed to run in a specific direction. The entrances for the emergency vehicles are directional, as shown below. The green arrow shows the correct direction. The orange area shows the wrong direction..

An overhead view of the Walt Disney World Track and the sharp end of the barrier at the emergency egress.

If you run the track backward, you have a much higher probability of running head on into the sharp end of the barrier (circles). Running a track backward resulted in the death of driving instructor Gary Terry at the Walt Disney World track in 2014 when his student lost control and they this barrier.

But there’s another reason for us to keep turning left: The driver’s seat is on the left and you are more likely to hit the outside wall than the inside. That means you hit the side of the car furthest from the driver, and the driver has an easier time getting out of the car because he’s not right up against the wall.

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