I did not know that yesterday!

Cops love asking motorists if they know how fast they were going. We're not sure why. Thanks to their radar guns, cops already know the answer.

Despite all the rhetorical questions it's spawned, the radar gun remains one of the more interesting developments in traffic enforcement. To learn how it works, we consulted the folks at HowStuffWorks.

They explain that speed guns measure "the round-trip time for light to reach a car and reflect back" after a cop shoots a beam at a speeding car. "If the gun takes 1,000 samples per second," it's able to compare the change in distance between the samples. Armed with that information, it can then calculate the car's speed.

Because the radar gun takes so many samples per second, the results are usually very accurate. We suppose that's a good thing, but it does make appealing a ticket much more difficult.

Source: ask.yahoo.com