Light Harp
It’s time for a little light music... use lights and light detectors to play songs on this virtual instrument. ExplanationLight shines from the top of the frame onto the detectors below. When you break each light beam with your hands, the detector sends a signal to the computer to play a note. The computer contains samples of pre-recorded instruments. The light detectors in Light Harp are found at the bottom of deep holes. Light travels in straight lines, so only light that comes directly from above will be detected. The same is true for deep wells—the well is only filled with light when the sun is correctly aligned overhead. An ancient site in Ireland called Newgrange uses this principle to light up a chamber at the end of a 19 m long passageway on the shortest day of the year. Extras for ExpertsYou might have heard that you can see stars in the daylight if you stand at the bottom of a very deep well or a long chimney. This is actually a myth! If you stand at the base of a well, the daylight at the top of the well will form a very bright spot. This brightness from the sunlight in the sky swamps out the brightness of the stars. A patch of light sky is roughly six million times brighter than the same patch of dark sky on a moonless night. Only the very brightest of stars can possibly be seen. Because light travels in straight lines, only stars that are directly overhead will be visible from the bottom of the well or chimney. The chance of one of the very few visible bright stars passing directly overhead is very slim. Questions to AskWhat instruments can everyone play? Has anyone played an instrument that needs electricity to work? How about an instrument doesn’t need you to touch it to work? Can you guess how this might work? Further Reading
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