Pioneers In Vannevar Bush At MIT, Bush became professor of electrical The Differential Analyser This machine was designed to power transmission, and set out to investigate one solve an important class of of the major problems involved in the supply of mathematical functions that electricity — how to avoid blackouts that occur as a occur in many areas of result of sudden unpredicted surges in demand. science and engineering, known as second order The mathematical equations that govern such a differential equations. The situation had been discovered at the end of the method had first been 19th century by the Scottish scientist James Clerk suggested by Lord Kelvin and Maxwell (1831 — 1879). But there were so many involved feeding the output of simultaneous equations involved that the problem one integrator (a device that effectively calculates the area could not be solved by hand, and so Bush set about under a curve) into the input inventing a machine for this purpose. Bush was of another. However, the also inspired by the work of Lord Kelvin (1824 - strength of the output was 1907), a British scientist who had proposed a generally too weak to act as an input and it was not until general purpose machine for solving the amplifiers were invented that mathematical equations involved in predicting the method could be applied. tides. Bush's 1931 machine was In the early 1920's, Bush built his first machine, entirely mechanical and was a which he called the `product telegraph'. This complex structure of gears, axles and electric motors. machine enabled human operators to trace the Input and output were in the paths of waves drawn on a graph (using a form of shaft rotations and the potentiometer — a device that turns a position feedback problem was solved measurement into a voltage). They then fed these by using a 'torque' amplifer. electrical signals into a specially adapted watt In the 1940's, a more advanced differential analyser meter — the spinning disc found in any power was built using electrical meter, which records the amount of power components, but the machine consumed by integrating the fluctuating values of weighed over a hundred tons. The differential analyser, current and voltage to give the `product'. The output from the five The success of this machine in solving a set of registers was in a digital designed by Vannevar Bush, was printout form and was simultaneous equations suggested that it might be accurate to one part in an electromechanical calculator possible to build a device that could solve even 10,000. The initial conditions more difficult second order differential equations. and control parameters were that solved differential equations supplied on punched paper Further research by Bush led to the completion of tape. The machine was used Many people argue that Vannevar Bush is the the first differential analyser in 1931. The machine throughout the Second World father of the computer. His most important proved extremely successful, and copies were built War for cryptography and contribution to the development of computer in Britain and Europe. In America, the Moore ballistic work science came in 1931 when he created a School of Electrical Engineering at the University mechanical differential analyser, which stimulated of Pennsylvania — which was later to build the research that eventually led to the development of ENIAC computer (see page 88) — commissioned the digital computer one. Where Bush's product telegraph had been Bush was born near Boston, Massachusetts, on accurate to only two per cent, the differential 11 March 1890 and, following in his father's analyser gave results accurate to 0.05 per cent. footsteps, studied engineering at college. After However, the cost of improving the accuracy of graduating in 1913, he worked briefly for the this type of mechanical device increased by a General Electric Company before taking up a factor of ten for every extra decimal place. With junior lectureship at his old college. This was the development of the digital computer, however, followed by postgraduate studies at Harvard the cost of a machine only doubled if its accuracy University and the Massachusetts Institute of were similarly increased. Technology (MIT). During the First World War, Bush became dean of the engineering school Bush was involved in the development of and vice president of the Carnegie Institute in submarine detectors for the US military. 1939, and his able work in administering the Bush developed his first invention, a device for millionaire's estate for scientific research resulted surveying land, while he was still a student. The in his appointment as chairman of the National mechanism, which was suspended between two Defense Research Committee in the following bicycle wheels, calculated the height of the ground year. In this office he was responsible for wartime over which it travelled and displayed the output as US military research and, in particular, was a profile of the land in graph form. It also influential in authorising the Manhattan project, incorporated a device known as an integrator, which led to the creation of the atomic bomb. Bush since the determination of the height at any retired in 1955 to devote time to his personal position required a knowledge of all the previous hobbies. These included boating and turkey values on its journey. farming, as well as inventing. He died in 1974.

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