Can You Drive Fast Enough to Avoid Being Clocked by Speed Cameras?

(Photo: Elliot Brown)

In some jurisdictions, governments set up cameras along roads to track how fast cars move. If a car is traveling over the speed limit, it snaps a picture of the license plate on it. A computer then fines the owner of the car.

Would it be possible to drive so fast that the camera wouldn't be able to take a picture of your license plate? Please don't to do it. But, yes, it is hypothetically possible.

Physics students at the University of Leicester in the UK determined that if a car traveled at 119 million miles an hour--that's about 1/6 the speed of light--the plate would be unreadable to a speed camera. That's because of the Doppler Effect. As the car moved at that velocity, light from it would shift toward the red end of the spectrum, rendering the car undetectable. Phys.Org explains:

Their calculation is based on the Doppler Effect – the physical effect where the frequencies of light or sound waves emanating from an object increase or decrease when it moves towards or away from you.

This effect is at work when you hear an ambulance – its siren will appear to lower in pitch as it drives past you.

With light, this process creates "red shift" – where the frequency of light from an object travelling away from the observer is shifted towards the red end of the colour spectrum. The faster an object is travelling, the bigger the shift in frequency.

This means it would theoretically be possible for the light from a fast-moving car number plate to be shifted out of the frequency range which speed cameras are able to detect.

-via VA Viper