29 ноября 1803 родился австрийский физик Кристиан Доплер

Everyone knows this Austrian physician in connection with an effect that bears his name. This effect was wittily described by Robert Wood, an American physicist. Once he ran a red light and got stopped by the police. Wood explained his mistake by the Doppler effect: the frequency of the light increases when approaching the source of light, and it is entirely possible to see green rather than red. But Wood failed to dupe the policeman, for the latter also knew physics a bit. In order to take red light for the green on an immobile traffic light, the observer’s speed has to be, putting it mildly, very high. And so, Wood got a speeding ticket.

Indeed, how could the policeman not know the Doppler effect when it is used in radar guns?