Why do Searchlights "Shorten"? A few days ago I had the opportunity to stand near the base of a revolving searchlight (apparently part of an ad campaign for a car dealership). It was a clear night. An odd optical illusion struck me: the beam seemed to go out only a few hundred feet... and then stop completely in a short distance, as if stopped suddenly by a cloud or fog bank. The operator told me that the beam actually reached 5 miles and I biked around and verified that it looked that way from the side. But still, from the base the appearance was very different. What could have caused this? My guess is it has something to do with a slight flaring of the beam which might mess with the perspective. Still it is an eerie and striking effect and if you ever have a chance to see a revolving searchlight from the base, don't miss it.