The image compares the situations of a rocket model under the sunlight at noon and afternoon in a recent day. Have you noticed something strange? Yes, the rocket model at noon seems not casting any shadow. Under most circumstances, even at noon, objects on ground that exposed to sunlight will cast long shadows, but there is an exception to this well-known phenomenon, which is the time when "Lahaina Noon" occurs during every summer.

In addition to the motion from the east to the west, the sun also moves in the south-north direction slowly. During summer solstice, the sun reaches the overhead position of any region on the Tropic of Cancer (23.5°N). Since Hong Kong is located at 22.3°N, the sun passes through the zenith of Hong Kong before and after the summer solstice. When it happens, the sun shines directly overhead, Lahaina Noon occurs. If some bamboo poles or other objects are erected outside at this particular time, their shadows will simply disappear.

This year, Lahaina Noon occurs at 12:22 p.m. on June 3 and 12:29 p.m. on July 9 respectively in Hong Kong. You may pay attention to the street on Thursday at noon to check if the shadows of objects are slowly shrinking and disappearing.