Can The Doppler Effect Help You Beat The Speed Camera?

The shortest answer is no.

Thanks to the curiosities of physics, there is this paradoxical yet plausible notion that you could beat a camera meant to photograph you speeding by going so fast that it won’t pick you up. In theory there is some speed at which the very light reflected off of your car will become undetectable to the human eye. But how fast would that be?

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When you hear an ambulance headed your way, the blaring sirens increase in pitch* until the vehicle reaches you, and the pitch slides back down as it passes. This is “Doppler Effect.” Sound waves traveling in the same direction can “bunch up,” making them seem at a higher pitch. The same thing can happen with light. Edwin Hubble, the astronomer whose name christened the Hubble Telescope, discovered that galaxies moving away from us had light waves that were stretching apart. Like a fading sound, the light from the galaxies was getting redder—being “red shifted.” What happens as the galaxies gallop away from us means that if you were to go fast enough, there is some point were the light reflecting off your car would be red-shifted below human (or camera) detection.

In a paper from the Journal of Physics Special Topics, authors Worthy, Garner, and Taylor-Ashley do the Doppler number crunching. They assumed that a car would be moving away from the camera when the photo was taken, that the average license plate reflects basically yellow light, and that a license plate is undetectable when the light is red-shifted below 430 terahertz—the human limit.

Using those values and this equation, the authors concluded that the minimum velocity to beat the speed camera with the Doppler Effect is about 0.178c, or 18 percent the speed of light. Unfortunately for your outstanding tickets, even in the fastest supercar ever built, you have no hope of getting to this speed. 18 percent the speed of light is over 33,000 miles per second—if you crashed your car at this speed you would be obliterated by 10 times more energy than was released by the supervolcano Krakatoa.

So no, you can’t red-shift your way out of a ticket. But you could still speed your way out of one.

The Discovery Channel’s Mythbusters actually established that you could outrun the speed camera. So long as you passed the camera at 300 miles per hour or more, you would be far outside of the camera’s range as the photo snapped. If you want to break the law but now the laws of physics, invest in a dragster.

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What Really Happens When Lightning Strikes Sand: The Science Behind a Viral Photo

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Image Credit: Roads At Night: She’s Gone by Cayusa on Flickr

Paper Link: Red-Shifted Speed Cameras

Reference: Worthy, D., Garner, R., Gregory, J., & Taylor-Ashley, J. (2013, November 19). Red-shifted Speed Cameras. Journal of Physics Special Topics, 1-2.

*An earlier version of this post incorrectly linked the Doppler Effect to changes in amplitude, not pitch.

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No chilling effect on donations at the Polar Bear Plunge

Much to the chagrin of the proudly purple people of Baltimore, the Ravens will not be playing in the Super Bowl on Sunday.

But that means quarterback Joe Flacco's schedule was clear last weekend for a very different kind of physical challenge: the 15th annual Maryland State Police Polar Bear Plunge at Sandy Point State Park in Annapolis.

The waters of the Chesapeake Bay were a seasonably chilly 33 degrees, and the beach was blanketed in snow and ice, but that didn't stop more than 12,000 men, women and children from taking a dunk, making it the largest such event in the world, according to the organizers.

Still, it turns out that freezing your tush off requires a certain level of determination, even for a professional athlete. "You can psych yourself out thinking about it. You know how cold it is. You realize how crazy it is," says Flacco, 26. Luckily, he could focus on the heartwarming cause instead. All of those shivering bodies raised $2.1 million for Special Olympics Maryland.

Likewise, the Children's Tumor Foundation will be on the minds of participants in Cupid's Undie Run in Washington on Feb. 12, when just skivvies will be on their bodies. The one-mile trot is "your one opportunity to run by the Capitol half-naked without getting arrested," brags co-organizer Bobby Gill, who's been stunned by what a popular proposition that is. Last year's debut was initially expected to draw 30 runners, but 600 showed up to dash around the remainders of the Snowpocalypse in their underwear. This year, the field was capped at 500, and that filled up nearly a month ago. The event aims to raise $25,000, and the tally so far is more than $20,000.

No to drunk divers

No doubt some people do this type of stuff purely for charity. "If everybody gives a little of their time, we can help people with disabilities do great things," 12-year-old Jake Cowles of Severna Park told me Saturday as he arrived for his third plunge, which he describes as feeling like "being stabbed." I dare you not to believe him.

But part of the appeal also comes from the fact that it seems so nuts. Gill, a 27-year-old biomedical engineer from Beltsville, is an endurance runner whose distance of choice is 100 miles. "So how do you spice it up if you're only doing one? Take away the clothes," he says. With these events, there's no need to train or be born with any athletic skills to feel as if you've accomplished something extraordinary.

"It's daring, but not so extreme that you can't imagine doing it. It's within reach," adds plunge spokeswoman Kelley Schniedwind. "It's Everyman's Everest."

(To check on that, I contacted Dave Hahn of Taos, N.M., a mountain guide who has scaled Mount Everest 12 times. And even though he has swum in Antarctic waters, he wouldn't be so eager to dive in again - or run around in his underwear for that matter. "People make the mistake of thinking I like the cold. I like to keep my clothes on," he says.)

There's a fine line between fun and dangerous, and it's critical that participants remember that, says Matthew Levy, a doctor and director of medical operations for this year's Polar Bear Plunge. Being cold is bad, but being cold and wet is much worse: You'll lose heat 20 times faster and are much more at risk for frostbite, hypothermia and other exposure-related dangers. That's why no one is allowed to stay in the water for more than five minutes and everyone's encouraged to quickly return to the heated changing tents.

As for drinking, the only beverage people were chugging at the plunge this year was coffee. Alcohol was nixed because of a huge increase in medical incidents last year involving intoxication and exposure. "One of the things I'd like to dispel is that alcohol warms you up. It actually dehydrates you and lowers your core body temperature," Levy says. Then there's the added problem that it clouds your judgment, so you're likely to do things like stand around soaking and shirtless.

Cupid's Undie Run starts and ends at the Pour House tavern on Capitol Hill, so boozing is expected, but Gill also encourages participants to find other ways to stay warm. "If you want to move in closer to others for body heat, that's okay," he says. And to keep the crowd's temperature up, the organizers are considering adding a pit stop for push-ups and jumping jacks. (The average low in the District for Feb. 12 is 29 degrees.)

Cold comfort

Getting a blast of cold isn't entirely unhealthy. Several plungers reported to me that they felt invigorated by the experience, and athletes frequently take individual polar bear plunges after brutal workouts to speed recovery. (Not Flacco, though: "I stay out of the cold tub.")

The most applicable science here probably comes from several recent studies related to brown fat. The substance, which burns calories instead of storing them, was recently thought not to be present in adults. Scientists have found that not only do we have it, but we can activate it by exposing ourselves to cold. So it's conceivable, though not in any way proven, that a chilly plunge or run could help participants lose weight.

That could mean the greatest benefits come for the Super Plungers, a group of 60 men and women who earn their name by running into the Chesapeake Bay every hour for 24 hours starting the day before the plunge. But Gregg Pokrywka, a 53-year-old Towson physician who joined their ranks this year, didn't sign up for his health. "I wanted to do something visible as an example," he says. "I think the bottom line is you're enduring a little pain for a good cause."

Maybe that explains why despite the frigid waters, everyone emerging from the beach on Saturday had a grin along with their goose bumps.

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