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.
More Geeky Science:
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.