A small tape dispenser is an object that holds a roll of tape and has a mechanism on one end to easily shear the tape. Dispensers vary widely based on the tape they dispense. Abundant and most common, clear tape dispensers (like those used in an office […]

            The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object (the Milky Way) was made in the 1930s, but subsequent advances (especially post-World War […]

              For opposition to a fundamental change in power, see counter-revolution. Tachometer showing engine RPM (revolutions per minute), and a redline from 6000 and 7000 RPM. A tachometer (also called a revolution-counter, rev-counter, or RPM gauge) is an instrument that measures the rotation speed of a shaft or disk, […]

          In chemistry, polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene which finds numerous applications. PTFE is most well known by the DuPont brand name Teflon. PTFE is a fluorocarbon solid, as it is a high molecular weight compound consisting wholly of carbon and fluorine. Neither water and water-containing substances nor […]

          Xerography (or electrophotography) is a dry photocopying technique invented by Chester Carlson in 1938, for which he was awarded U.S. Patent 2,297,691 on October 6, 1942. Carlson originally called his invention electrophotography. It was later renamed xerography—from the Greek roots xeros (dry) and graphos (writing)—to emphasize that, unlike reproduction techniques […]

              A computer is a machine that manipulates data according to a set of instructions. Although mechanical examples of computers have existed through much of recorded human history, the first electronic computers were developed in the mid-20th century (1940–1945). These were the size of a large room, consuming as […]