sky lantern (plural sky lanterns) An ornament consisting of a small hot air balloon made of paper, with an opening at the bottom where a small fire is suspended. In China, Taiwan and Thailand, sky lanterns are traditionally made from oiled rice paper on a bamboo frame. The source of hot air may be a small candle or fuel cell composed of a waxy flammable material. For example, the Mid-Autumn Festival and the Spring Lantern Festival both feature sky lanterns. The sky lantern also started to play a role in Buddhist ceremonies. They believed that the lanterns would carry away their troubles, and would bring good luck and prosperity. A lantern is an often portable source of lighting, typically featuring a protective enclosure for the light source – historically usually a candle or a wick in oil, and often a battery-powered light in modern times – to make it easier to carry and hang up, and make it more reliable outdoors or in drafty interiors. A simple wooden or metal frame, a paper shell, and a source of flame are all you need to create a sky lantern. They first took to the sky as military signals above the battlefields of ancient China, and are sometimes still called Kongming lanterns after a legendary 3rd century Chinese general who first put them to use Unfortunately, sky lanterns are not environmentally friendly. “Biodegradable” lanterns made of bamboo take decades to break down and can injure or entrap animals in the meantime. They can also start dangerous fires. More than 30 animals died in Germany after floating lanterns started a fire inside a local zoo. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum and polarization. Its speed in a vacuum, 299 792 458 metres a second (m/s), is one of the fundamental constants of nature.