Engineering is the discipline of applying technical and scientific knowledge and physical resources to design and produce materials, structures, machines, devices, systems, and processes that meet a desired objective under specified criteria. Engineering encompasses a range of specialized subdisciplines, each with a specific area of emphasis and related to a particular area of technology. Examples include chemical engineering, electrical engineering, environmental engineering, mechanical engineering, and so forth.
A person who practices engineering is called an engineer. Those licensed in specific areas of engineering may have formal designations such as Professional Engineer, Chartered Engineer, or Incorporated Engineer.
The American Engineers' Council for Professional Development (ECPD, the predecessor of ABET) has defined engineering as follows:
“[T]he creative application of scientific principles to design or develop structures, machines, apparatus, or manufacturing processes, or works utilizing them singly or in combination; or to construct or operate the same with full cognizance of their design; or to forecast their behavior under specific operating conditions; all as respects an intended function, economics of operation and safety to life and property.”
The concept of engineering has existed since ancient times as humans devised fundamental inventions such as the pulley, lever, and wheel. Each of these inventions is consistent with the modern definition of engineering, exploiting basic mechanical principles to develop useful tools and objects.
The term engineering itself has a much more recent etymology, deriving from the word engineer, which itself dates back to 1325, when an engine’er (literally, one who operates an engine) originally referred to “a constructor of military engines.” In this context, now obsolete, an “engine” referred to a military machine, i.e., a mechanical contraption used in war (for example, a catapult). The word “engine” itself is of even older origin, ultimately deriving from the Latin ingenium (c. 1250), meaning “innate quality, especially mental power, hence a clever invention.”
Later, as the design of civilian structures such as bridges and buildings matured as a technical discipline, the term civil engineering entered the lexicon as a way to distinguish between those specializing in the construction of such non-military projects and those involved in the older discipline of military engineering (the original meaning of the word “engineering,” now largely obsolete, with notable exceptions that have survived to the present day such as military engineering corps, e.g., the U. S. Army Corps of Engineers).
The Acropolis and the Parthenon in Greece, the Roman aqueducts, Via Appia and the Colosseum, the Hanging Gardens of Babylon, the Pharos of Alexandria, the pyramids in Egypt, Teotihuacán and the cities and pyramids of the Mayan, Inca and Aztec Empires, the Great Wall of China, among many others, stand as a testament to the ingenuity and skill of the ancient civil and military engineers.
The earliest civil engineer known by name is Imhotep. As one of the officials of the Pharaoh, Djosèr, he probably designed and supervised the construction of the Pyramid of Djoser (the Step Pyramid) at Saqqara in Egypt around 2630-2611 B.C.E.  He may also have been responsible for the first known use of columns in architecture.
An Iraqi by the name of al-Jazari helped influence the design of today's modern machines when sometime in between 1174 and 1200 he built five machines to pump water for the kings of the Turkish Artuqid dynasty and their palaces. The double-acting reciprocating piston pump was instrumental in the later development of engineering in general because it was the first machine to incorporate both the connecting rod and the crankshaft, thus, converting rotational motion to reciprocating motion.
British Charter Engineer Donald Routledge Hill once wrote:
It is impossible to over emphasize the importance of al-Jazari's work in the history of engineering, it provides a wealth of instructions for the design, manufacture and assembly of machines.
Even today some toys still use the cam-lever mechanism found in al-Jazari's combination lock and automaton. Besides over 50 ingenuous mechanical devices, al-Jazari also developed and made innovations to segmental gears, mechanical controls, escapement mechanisms, clocks, robotics, and protocols for designing and manufacturing methods.
The first steam engine was built in 1698 by mechanical engineer Thomas Savery. The development of this device gave rise to the industrial revolution in the coming decades, allowing for the beginnings of mass production.
With the rise of engineering as a profession in the eighteenth century, the term became more narrowly applied to fields in which mathematics and science were applied to these ends. Similarly, in addition to military and civil engineering the fields then known as the mechanic arts became incorporated into engineering.
Electrical Engineering can trace its origins in the experiments of Alessandro Volta in the 1800s, the experiments of Michael Faraday, Georg Ohm and others and the invention of the electric motor in 1872. The work of James Maxwell and Heinrich Hertz in the late nineteenth century gave rise to the field of Electronics. The later inventions of the vacuum tube and the transistor further accelerated the development of Electronics to such an extent that electrical and electronics engineers currently outnumber their colleagues of any other Engineering specialty.
The inventions of Thomas Savery and the Scottish engineer James Watt gave rise to modern Mechanical Engineering. The development of specialized machines and their maintenance tools during the industrial revolution led to the rapid growth of Mechanical Engineering both in its birthplace Britain and abroad.
Even though in its modern form Mechanical engineering originated in Britain, its origins trace back to early antiquity where ingenuous machines were developed both in the civilian and military domains. The Antikythera mechanism, the earliest known model of a mechanical computer in history, and the mechanical inventions of Archimedes, including his death ray, are examples of early mechanical engineering. Some of Archimedes' inventions as well as the Antikythera mechanism required sophisticated knowledge of differential gearing or epicyclic gearing, two key principles in machine theory that helped design the gear trains of the Industrial revolution and are still widely used today in diverse fields such as robotics and automotive engineering.
Chemical Engineering, like its counterpart Mechanical Engineering, developed in the nineteenth century during the Industrial Revolution. Industrial scale manufacturing demanded new materials and new processes and by 1880 the need for large scale production of chemicals was such that a new industry was created, dedicated to the development and large scale manufacturing of chemicals in new industrial plants. The role of the chemical engineer was the design of these chemical plants and processes.
Aeronautical Engineering deals with aircraft design while Aerospace Engineering is a more modern term that expands the reach envelope of the discipline by including spacecraft design. Its origins can be traced back to the aviation pioneers around the turn of the century from the 19th century to the 20th although the work of Sir George Cayley has recently been dated as being from the last decade of the 18th century. Early knowledge of aeronautical engineering was largely empirical with some concepts and skills imported from other branches of engineering. Only a decade after the successful flights by the Wright brothers, the 1920s saw extensive development of aeronautical engineering through development of World War I military aircraft. Meanwhile, research to provide fundamental background science continued by combining theoretical physics with experiments.
The first PhD in engineering (technically, applied science and engineering) awarded in the United States went to Willard Gibbs at Yale University in 1863; it was also the second PhD awarded in science in the U.S.
In 1990, with the rise of computer technology, the first search engine was built by computer engineer Alan Emtage.
Engineering, much like science, is a broad discipline which is often broken down into several sub-disciplines. These disciplines concern themselves with differing areas of engineering work. Although initially an engineer will be trained in a specific discipline, throughout an engineer's career the engineer may become multi-disciplined, having worked in several of the outlined areas. Historically the main Branches of Engineering are categorized as follows:
With the rapid advancement of Technology many new fields are gaining prominence and new branches are developing such as Computer Engineering, Software Engineering, Nanotechnology, Molecular engineering, Mechatronics etc. These new specialties sometimes combine with the traditional fields and form new branches such as Mechanical Engineering and Mechatronics and Electrical and Computer Engineering.
For each of these fields there exists considerable overlap, especially in the areas of the application of sciences to their disciplines such as physics, chemistry and mathematics.
Engineers apply the sciences of physics and mathematics to find suitable solutions to problems or to make improvements to the status quo. More than ever, Engineers are now required to have knowledge of relevant sciences for their design projects, as a result, they keep on learning new material throughout their career. If multiple options exist, engineers weigh different design choices on their merits and choose the solution that best matches the requirements. The crucial and unique task of the engineer is to identify, understand, and interpret the constraints on a design in order to produce a successful result. It is usually not enough to build a technically successful product; it must also meet further requirements. Constraints may include available resources, physical, imaginative or technical limitations, flexibility for future modifications and additions, and other factors, such as requirements for cost, safety, marketability, productibility, and serviceability. By understanding the constraints, engineers derive specifications for the limits within which a viable object or system may be produced and operated.
Engineers use their knowledge of science, mathematics, and appropriate experience to find suitable solutions to a problem. Engineering is considered a branch of applied mathematics and science. Creating an appropriate mathematical model of a problem allows them to analyze it (sometimes definitively), and to test potential solutions. Usually multiple reasonable solutions exist, so engineers must evaluate the different design choices on their merits and choose the solution that best meets their requirements. Genrich Altshuller, after gathering statistics on a large number of patents, suggested that compromises are at the heart of "low-level" engineering designs, while at a higher level the best design is one which eliminates the core contradiction causing the problem.
Engineers typically attempt to predict how well their designs will perform to their specifications prior to full-scale production. They use, among other things: prototypes, scale models, simulations, destructive tests, nondestructive tests, and stress tests. Testing ensures that products will perform as expected. Engineers as professionals take seriously their responsibility to produce designs that will perform as expected and will not cause unintended harm to the public at large. Engineers typically include a factor of safety in their designs to reduce the risk of unexpected failure. However, the greater the safety factor, the less efficient the design may be.
As with all modern scientific and technological endeavors, computers and software play an increasingly important role. As well as the typical business application software there are a number of computer aided applications (CAx) specifically for engineering. Computers can be used to generate models of fundamental physical processes, which can be solved using numerical methods.
One of the most widely used tools in the profession is computer-aided design (CAD) software which enables engineers to create 3D models, 2D drawings, and schematics of their designs. CAD together with Digital mockup (DMU) and CAE software such as finite element method analysis allows engineers to create models of designs that can be analyzed without having to make expensive and time-consuming physical prototypes. These allow products and components to be checked for flaws; assess fit and assembly; study ergonomics; and to analyze static and dynamic characteristics of systems such as stresses, temperatures, electromagnetic emissions, electrical currents and voltages, digital logic levels, fluid flows, and kinematics. Access and distribution of all this information is generally organized with the use of Product Data Management software.
There are also many tools to support specific engineering tasks such as Computer-aided manufacture (CAM) software to generate CNC machining instructions; Manufacturing Process Management software for production engineering; EDA for printed circuit board (PCB) and circuit schematics for electronic engineers; MRO applications for maintenance management; and AEC software for civil engineering.
In recent years the use of computer software to aid the development of goods has collectively come to be known as Product Lifecycle Management (PLM).
Engineering is a subject that ranges from large collaborations to small individual projects. Almost all engineering projects are beholden to some sort of financing agency: a company, a set of investors, or a government. The few types of engineering that are minimally constrained by such issues are pro bono engineering and open design engineering.
By its very nature engineering is bound up with society and human behavior. Every product or construction used by modern society will have been influenced by engineering design. Engineering design is a very powerful tool to make changes to environment, society and economies, and its application brings with it a great responsibility, as represented by many of the Engineering Institutions codes of practice and ethics. Whereas medical ethics is a well-established field with considerable consensus, engineering ethics is far less developed, and engineering projects can be subject to considerable controversy. Just a few examples of this from different engineering disciplines are the development of nuclear weapons, the Three Gorges Dam, the design and use of Sports Utility Vehicles and the extraction of oil. There is a growing trend amongst western engineering companies to enact serious Corporate and Social Responsibility policies, but many companies do not have these.
Engineering is a key driver of human development. Sub-Saharan Africa in particular has a very small engineering capacity which results in many African nations being unable to develop crucial infrastructure without outside aid. The attainment of many of the Millennium Development Goals requires the achievement of sufficient engineering capacity to develop infrastructure and sustainable technological development. All overseas development and relief NGOs make considerable use of engineers to apply solutions in disaster and development scenarios. A number of charitable organizations aim to use engineering directly for the good of mankind:
Engineering is a well respected profession. For example, in Canada it ranks as one of the public's most trusted professions.
Sometimes engineering has been seen as a somewhat dry, uninteresting field in popular culture, and has also been thought to be the domain of nerds. For example, the cartoon character Dilbert is an engineer. One difficulty in increasing public awareness of the profession is that average people, in the typical run of ordinary life, do not ever have any personal dealings with engineers, even though they benefit from their work every day. By contrast, it is common to visit a doctor at least once a year, the chartered accountant at tax time, and, occasionally, even a lawyer.
This has not always been so - most British school children in the 1950s were brought up with stirring tales of 'the Victorian Engineers', chief amongst whom were the Brunels, the Stephensons, Telford and their contemporaries.
In science fiction engineers are often portrayed as highly knowledgeable and respectable individuals who understand the overwhelming future technologies often portrayed in the genre. The Star Trek characters Montgomery Scott, Geordi La Forge, Miles O'Brien, B'Elanna Torres, and Charles Tucker are famous examples.
Occasionally, engineers may be recognized by the "Iron Ring"—a stainless steel or iron ring worn on the little finger of the dominant hand. This tradition began in 1925 in Canada for the Ritual of the Calling of an Engineer as a symbol of pride and obligation for the engineering profession. Some years later in 1972 this practice was adopted by several colleges in the United States. Members of the US Order of the Engineer accept this ring as a pledge to uphold the proud history of engineering.
A Professional Engineer's name may be followed by the post-nominal letters PE or P.Eng in North America. In much of Europe a professional engineer is denoted by the letters IR, while in the UK and much of the Commonwealth the term Chartered Engineer applies and is denoted by the letters CEng.
In most Western countries, certain engineering tasks, such as the design of bridges, electric power plants, and chemical plants, must be approved by a Professional Engineer or a Chartered Engineer or an Incorporated Engineer.
Laws protecting public health and safety mandate that a professional must provide guidance gained through education and experience. In the United States, each state tests and licenses Professional Engineers. In much of Europe and the Commonwealth professional accreditation is provided by Engineering Institutions, such as the Institution of Civil Engineers from the UK. The engineering institutions of the UK are some of the oldest in the world, and provide accreditation to many engineers around the world. In Canada the profession in each province is governed by its own engineering association. For instance, in the Province of British Columbia an engineering graduate with 4 or more years of experience in an engineering-related field will need to be registered by the Association for Professional Engineers and Geoscientists [(APEGBC)] in order to become a Professional Engineer and be granted the professional designation of P.Eng.
The federal US government, however, supervises aviation through the Federal Aviation Regulations administrated by the Dept. of Transportation, Federal Aviation Administration. Designated Engineering Representatives approve data for aircraft design and repairs on behalf of the Federal Aviation Administration.
Even with strict testing and licensure, engineering disasters still occur. Therefore, the Professional Engineer, Chartered Engineer, or Incorporated Engineer adheres to a strict code of ethics. Each engineering discipline and professional society maintains a code of ethics, which the members pledge to uphold.
Refer also to the Washington accord for international accreditation details of professional engineering degrees.
Scientists study the world as it is; engineers create the world that has never been.—Theodore von Kármán
There exists an overlap between the sciences and engineering practice; in engineering, one applies science. Both areas of endeavor rely on accurate observation of materials and phenomena. Both use mathematics and classification criteria to analyze and communicate observations. Scientists are expected to interpret their observations and to make expert recommendations for practical action based on those interpretations. Scientists may also have to complete engineering tasks, such as designing experimental apparatus or building prototypes. Conversely, in the process of developing technology engineers sometimes find themselves exploring new phenomena, thus becoming, for the moment, scientists.
In the book What Engineers Know and How They Know It, Walter Vincenti asserts that engineering research has a character different from that of scientific research. First, it often deals with areas in which the basic physics and/or chemistry are well understood, but the problems themselves are too complex to solve in an exact manner. Examples are the use of numerical approximations to the Navier-Stokes equations to describe aerodynamic flow over an aircraft, or the use of Miner's rule to calculate fatigue damage. Second, engineering research employs many semi-empirical methods that are foreign to pure scientific research, one example being the method of parameter variation.
As stated by Fung et al. in the revision to the classic engineering text, Foundations of Solid Mechanics, 
"Engineering is quite different from science. Scientists try to understand nature. Engineers try to make things that do not exist in nature. Engineers stress invention. To embody an invention the engineer must put his idea in concrete terms, and design something that people can use. That something can be a device, a gadget, a material, a method, a computing program, an innovative experiment, a new solution to a problem, or an improvement on what is existing. Since a design has to be concrete, it must have its geometry, dimensions, and characteristic numbers. Almost all engineers working on new designs find that they do not have all the needed information. Most often, they are limited by insufficient scientific knowledge. Thus they study mathematics, physics, chemistry, biology and mechanics. Often they have to add to the sciences relevant to their profession. Thus engineering sciences are born."
The study of the human body, albeit from different directions and for different purposes, is an important common link between medicine and some engineering disciplines. Medicine aims to sustain, enhance and even replace functions of the human body, if necessary, through the use of technology. Modern medicine can replace several of the body's functions through the use of artificial organs and can significantly alter the function of the human body through artificial devices such as, for example, brain implants and pacemakers. The fields of Bionics and medical Bionics are dedicated to the study of synthetic implants pertaining to natural systems. Conversely, some engineering disciplines view the human body as a biological machine worth studying, and are dedicated to emulating many of its functions by replacing biology with technology. This has led to fields such as artificial intelligence, neural networks, fuzzy logic, and robotics. There are also substantial interdisciplinary interactions between engineering and medicine.
Both fields provide solutions to real world problems. This often requires moving forward before phenomena are completely understood in a more rigorous scientific sense and therefore experimentation and empirical knowledge is an integral part of both. Medicine, in part, studies the function of the human body. The human body, as a biological machine, has many functions that can be modeled using Engineering methods. The heart for example functions much like a pump, the skeleton is like a linked structure with levers, the brain produces electrical signals etc. These similarities as well as the increasing importance and application of Engineering principles in Medicine, led to the development of the field of biomedical engineering that utilizes concepts developed in both disciplines.
Newly emerging branches of science, such as Systems biology, are adapting analytical tools traditionally used for engineering, such as systems modeling and computational analysis, to the description of biological systems.
There are connections between engineering and art; they are direct in some fields, for example, architecture, landscape architecture and industrial design (even to the extent that these disciplines may sometimes be included in a University's Faculty of Engineering); and indirect in others. The Art Institute of Chicago, for instance, held an exhibition about the art of NASA's aerospace design. Robert Maillart's bridge design is perceived by some to have been deliberately artistic. At the University of South Florida, an engineering professor, through a grant with the National Science Foundation, has developed a course that connects art and engineering. Among famous historical figures Leonardo Da Vinci is a well known Renaissance artist and engineer, and a prime example of the nexus between art and engineering.
In Political science the term engineering has been borrowed for the study of the subjects of Social engineering and Political engineering, which deal with forming political and social structures using engineering methodology coupled with political science principles.
All links retrieved September 22, 2013.
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