Ethnomathematics a rich cultural diversity
conjunction. The situation when two or more planets, or other celestial bodies, are temporarily close together in the sky. For more information see Astronomy answers: Conjunction (Utrecht University, Netherlands).
reflected, refracted, diffracted. All three terms refer to a change in the direction of a wave. A wave has long crests and valleys called wavefronts. The distance between successive crests is called the wavelength. The wave always travels in a direction that is at right angles (90°) to the wavefronts. A wave is reflected when it bounces off a smooth obstacle that is long compared to the wavelength. A wave is refracted when it travels from one medium to another in which its speed is different (eg, from deep water to shallow water); and it is diffracted when it passes through a small opening in, or around the edge of, a large obstacle. A wave is scattered when it bounces off a small or rough obstacle. For more information see Behaviour of waves (The Physics Classroom, USA) and Wave behavior (Alaska Tsunami, USA).
stick chart. A three-dimensional map of ocean patterns that was used by Marshall Islanders to teach and preserve their navigational knowledge. Each map was created by tying together midribs of coconut-palm leaves or pieces of split bamboo in patterns that represented wave and current patterns. Shells were used to indicate the position of islands in relation to the ocean currents. For more information see Traditional Marshallese Stickchart Navigation (Dirk Spennemann, Charles Sturt University, Australia).
Page updated April 2009.