How the concept of energy evolved?
The word energy appeared in English in the late sixteenth Century. In the 1580s, writers used the term ‘energy to describe a vigorous use of Speech or writing. It took another two and a half centuries for its modern scientific meaning to emerge. The concept of energy has evolved from those of the archaic fire, the more modern vis Viva (“living force”), which was dominant until the nineteenth century, and force, which persisted well into the 19th Century and today have a much narrower scope.
Prior to the time of Galileo (1546-1642 A.D.), science was conducted largely by philosophical argument. ideas were proposed, and elegant arguments put forward to lend reason to the premises of philosophers. The concept of energy was no exception. It was Aristotle (384-322 BC) who developed the concept of “fire’ as one of four basic ‘elements’ of nature first described by Empedocles (490-430 BC), the other three being earth, water and air.
Aristotle used the Greek word energeia to refer to the body being ‘at (en) work (ergeia)”. As late as 1842, the Encyclopaedia Britannica gave the word a brief entry: ENERGY, a term of Greek origin, signifying the power, virtue or efficacy of a thing.
As you already know that the Scientific Revolution in Europe in the Seventeenth Century, at that time many scientists investigated phenomena related to motion, heat and electricity. They were the ones to give the term “energy’ its modern meaning.
The concept of energy has its origins in the search of the Wis Viva, or the “living force” of motion. In Galileo’s times, it was thought that if experiments involving the collision of balls could be understood, one might discover the vis Viva, the cause for the effect. In the late seventeenth century, Leibnitz (the inventor of Calculus as we know it today) championed the idea that the vis Viva of a body is its mass times the square of its speed (what We now know to be twice the kinetic energy of a body). In the ensuing 150 years or so, a clear distinction could be made between the more abstract concepts of force and energy and the less abstract concepts of heat and work.
The invention of the thermometer – as early as in 1592 by Galileo (1564-1642) and then by Fahrenheit (1686-1736) in the early eighteenth century first helped to clarify the distinction between temperature and heat. Detailed studies of heat were carried out by Joseph Black (1728-1799) at the University of Edinburgh, UK. These studies served to inspire James Watt (1736-1819) who developed the first modern steam engine. The invention of steam engine inspired a spate of work on the relationship between motion and heat.
Experiments with electricity and electric motors led people to investigate the relation between motion and electricity around the same time. MaxWell was actively involved in this work. However, that the conservation of energy was a more basic law of the universe became clear only in the mid nineteenth century, when the science of thermodynamics was developed. The creators of the concept of energy were interested in investigating how steam and heat engines operate.
They had also discovered the conversion processes between heat, electricity and other phenomena. A number of discoveries were made at around the same time by brilliant scientists like the Englishmen Thomas Young (1773-1829) and James Prescott Joule (1818-1889), the American-born Benjamin Thompson (1753-1814), the Germans Julius Robert Mayer (1814-1878) and Hermann Helmholtz (1821-1894), the Frenchman Seguin (1786-1875) and the Dane Ludvig Colding (1815-1888). All of us know that Young demonstrated the wave-like character of light. We also know him for his research on the elasticity of materials. But the credit for being the first, in 1807, to use the word energy to denote what We now call kinetic energy goes to him.
The term “kinetic energy’ was first defined in 1829 by Gustave Gaspard Coriolis (better known for the Coriolis force). The phrase potential energy first appeared in the 1850s followed by mechanical, thermal, chemical, electrical and finally atomic energy.
Thompson, better known as Count Rumford – clarified the nature of heat by showing in 1804 that it is not a fluid-like substance, as was widely believed until then (Caloric theory of heat). He proposed that heat and temperature were related to motion. This realisation and the analysis of inter-conversion between heat and work by Seguin, Mayer, Colding and especially Joule, in the period 1839-1849, clarified the relationship between heat and work, as two qualitatively different but quantitatively equivalent forms of energy. Joule studied the nature of heat and discovered its relationship to mechanical work that led to the theory of conservation of energy. The SI unit of work, the joule, is named after him.
The 1840s were marked by the nearly simultaneous and independent conceptualisation of the conservation of energy by Mayer, Joule, Helmholtz and Colding. Mayer clearly formulated in 1842 the Conservation of energy and that heat is a form of mechanical energy. Finally, in 1847, the inspired young Helmholtz generalised this principle of conservation of energy into a universal law of nature, which came to be known as the First Law of thermodynamics.