Box of tricks
Question: On a recent visit to Edinburgh, we were in a pub which had an
instrument at the end of the bar approximately 30 centimetres in length and 3
centimetres wide. It appeared to be a black rectangular box, open on one side,
with a series of red lights inside.
When you moved your head swiftly, a brand name of vodka appeared to flash
along the surface of the bar although not all the letters could necessarily be
seen at once. How did the box produce this image, why could all the letters not
be seen simultaneously…
