smartglasses or through a mobile device giving the user the ability to view three-dimensional images. Mixed reality (MR) is the merging of the real world and virtual worlds to produce new environments and visualizations where physical and digital objects co-exist and interact in real time. A cyberspace is sometimes defined as a networked virtual reality. Simulated reality is a hypothetical virtual reality as truly immersive as the actual reality, enabling an advanced lifelike experience or even virtual eternity. History The development of perspective in Renaissance European art and the stereoscope invented by Sir Charles Wheatstone were both precursors to virtual reality. The first references to the more modern concept of virtual reality came from science fiction. 20th century Morton Heilig wrote in the 1950s of an "Experience Theatre" that could encompass all the senses in an effective manner, thus drawing the viewer into the onscreen activity. He built a prototype of his vision dubbed the Sensorama in 1962, along with five short films to be displayed in it while engaging multiple senses (sight, sound, smell, and touch). Predating digital computing, the Sensorama was a mechanical device. Heilig also developed what he referred to as the "Telesphere Mask" (patented in 1960). The patent application described the device as "a telescopic television apparatus for individual use... The spectator is given a complete sensation of reality, i.e. moving three dimensional images which may be in colour, with 100% peripheral vision, binaural sound, scents and air breezes." In 1968, Ivan Sutherland, with the help of his students including Bob Sproull, created what was widely considered to be the first head-mounted display system for use in immersive simulation applications, called The Sword of Damocles. It was primitive both in terms of user interface and visual realism, and the HMD to be worn by the user was so heavy that it had to be suspended from the ceiling, which gave the device a formidable appearance and inspired its name. Technically, the device was an augmented reality device due to optical passthrough. The graphics comprising the virtual environment were simple wire-frame model rooms. 1970–1990 The virtual reality industry mainly provided VR devices for medical, flight simulation, automobile industry design, and military training purposes from 1970 to 1990. David Em became the first artist to produce navigable virtual worlds at NASA's Jet Propulsion Laboratory (JPL) from 1977 to 1984. The Aspen Movie Map, a crude virtual tour in