Generally, a machine converts one form of movement into another. It is the responsibility of engineers to design machines whose parts and assemblies function in a safe and reliable, efficient and predictable fashion. In the words of one author, the mechanical engineer applies scientific method to the solution of mechanical problems. Indeed, the numerous laws and principles developed by scientists are the everyday tools of the mechanical engineer. Anything the engineer does that is related to the motion and dynamics of heat, gas, air, fluids and solid materials requires the understanding and application of science.
Mechanical engineers contribute to many industries and occupations, encompassing many specialties.
Some mechanical engineers work in areas not usually considered to require engineering. Efforts to clean up and preserve the earth's environment have attracted many mechanical engineers to projects involving the treatment of water, soil and waste material. Mechanical engineers also work alongside physicians, therapists and other medical professionals to investigate the workings of the human body and to design aids and instruments for medicine. Other mechanical engineers work closely with trainers, coaches and athletes on the design of sporting equipment. Mechanical engineers design advanced materials and structures to meet the demands of supersonic and hypersonic space travel.