Transformation of energy

William John Macquorn Rankine

William John Macquorn Rankine

William John Macquorn Rankine (Edinburgh, July 5, 1820 - Glasgow, December 24, 1872) was a Scottish engineer and physicist. He had very different interests; In his youth he was interested in botany, music theory and number theory and in his last years in mathematics and technology.

Together with Rudolf Clausius and William Thomson, he is among the founders of thermodynamics. He also developed the theory behind the steam engine, introduced concepts such as kinetic and potential energy, and investigated shock waves and metal fatigue. A temperature scale is named after William Rankine, known as the Rankine scale.

Life of William John Macquorn Rankine

Rankine was the son of the professional soldier and later civil engineer David Rankine and the daughter of banker Barbara Grahame of Glasgow. He was the second son, but his older brother died at an early age. Due to his poor health, he was taught mainly at home. He attended high school in Ayr and Glasgow only a few years after the family moved there in 1830. In his youth, he had a keen interest in music and mathematics. After reading, at the age of fourteen, Isaac Newton's greatest work, Principia Mathematica (1687) in Latin, became interested in physics.

At sixteen, in 1836, he began studying natural sciences at the University of Edinburgh, where he was taught, among other things, natural philosophy with James David Forbes and in natural history with Robert Jameson. At that time, he also read a lot of work by philosophers of the Scottish Enlightenment. At the university he received two awards for essays on physical research methods and on the wave theory of light, but did not complete the course.

In 1838 he left the university and became an assistant to the Irish civil engineer John Benjamin MacNeill. He worked here on railroad design, port construction and sewer construction. At the same time, he began writing articles that were published, among others, by the British "Institution of Civil Engineers." In 1855 he was appointed Professor of Civil Engineering and Mechanical Engineering at the University of Glasgow.

Rankine became a member of the Royal Society of Edinburgh in 1849 and of the Royal Society in London in 1853. He was also a member of the Royal Swedish Society of Sciences and the American American Academy of Arts and Sciences. In 1857 he founded a Scottish branch of the "Institution of Civil Engineers" and was the first president until 1870. In 1857, Rankine received an honorary doctorate from Trinity College in Dublin.

Rakine was also a talented musician and played cello, piano and sang. He also wrote poems, which were published posthumously as compiled works.

Importance of Rankine's Work

In addition to his work as a civil engineer, Rankine has made several contributions to science. He wrote standard works of mechanics, steam theory and practice, civil engineering principles and mechanical construction principles. With this he made an important contribution to the formalization of technical sciences, which at that time became a national and international example of Europe to America and Japan.

A special feature of his work was that Rankine was able to close the gap between engineering practice and scientific research. The science at that time was mainly pure and abstract and the engineers distrusted it. In the spirit of Francis Bacon and Thomas Reid, Rankine managed to make scientific research useful for practice. For example, he has made an important contribution to thermodynamics with his scientific research and the construction of theories. It was also based on the work of Benoît Clapeyron, Sadi Carnot and JP Joule.

Mechanical Engineering Research

Partly at the suggestion of his father, who knew a lot about the railroads, Rankine initially focused on mechanical engineering. His first publication, from 1842, was entitled "An experimental investigation on the advantage of cylindrical wheels on railways." The following year he presented an article on the fatigue of the metal that occurred in the axes of the locomotives. He showed that axle ruptures arose due to progressive degeneration, which fatigue (fatigue mentioned). This phenomenon occurred mainly with sudden transitions in the structure, and advised to complete these transitions.

In the field of static, he has developed methods to calculate the distribution of forces in building structures and has conducted research on the stability of buildings. He also studied hydrodynamics and ship design.

The Object of Physics

In addition to his contributions to the technical sciences, Rankine began his research in natural sciences in the course of the 40s of the 19th century. Rankine had been fascinated by steam engines from an early age, which had acquired a new dimension through his work with the railroads. He sought fundamental laws through experiments with thermodynamic processes. Rankine went even further in her thoughts and philosophized about the nature of the universe and the object of physics. For example, in 1852 he declared what would later be called the law of conservation of energy:

"Experimental evidence is accumulating every day, or a law that has conjectured that there is a long leg," all the different types of physical energy in the universe are mutually convertible, "that the total amount of physical energy, whether in form of visible movement and mechanical power, or of heat, light, magnetism, electricity, or chemical agency, or in other ways not yet understood, are immutably the transformations of its different portions of one of those forms of power to another, and its transfer from one part of matter to another, constituting the phenomena that are the objects of experimental physics. "

Rankine saw a connection between all the physical phenomena of visible movement and mechanical energy, heat, light, magnetism, electricity and chemical energy. He later resolved the idea of ​​the interchangeability of all these forms of energy and the laws that underlie this in his theory of energy. To make this set of physical phenomena debatable, he came up with a hypothesis of molecular vertebrae to describe the molecular structure of matter. The name of the Rakine cycle owes its name to the Scottish physicist.

Molecular Vertebrae Hypothesis

A central assumption in Rankine's scientific work was his hypothesis of molecular vertebrae (molecular scale swirls), also called "centrifugal elasticity theory." According to this hypothesis, all matter consisted of molecules formed by atomic nuclei surrounded by an elastic atmosphere, which was held in place by attractive forces. Rankine also approached that heat was a kind of vibration of the atmosphere that revolved around the atomic nucleus and light was, in fact, a vibration that emerged from the movement of atomic nuclei and spread even more thanks to the attraction and mutual repulsion of these nuclei. Rankine attributed mechanical properties to the atmosphere itself. According to him,

This hypothesis offered him a model for his theory of light and heat. He explained the double refraction of light as the transfer of movement from the atmosphere to the atomic nuclei and vice versa. He also came from this hypothesis to his comparisons on gas and heat. He took another step and worked on a general theory of mechanical action that could generate heat. He showed that a certain amount of heat disappeared and came to his own formulation of the second law of thermodynamics. This hypothesis did not play a role in the theory of steam machines of Rankine, but it did return in the theory of energy of Rankine that would be important in the industry of thermal power plants and solar thermal energy.

This hypothesis had some influence at the time. James Clerk Maxwell, for example, used it in his article "On physical lines of force" of 1861. He assumed that the magnetic lines of force in a substance were transported by a sea of ​​molecular vertebrae, consisting partly of ether and partly in ordinary matter.

Theory and Effects of Thermodynamics

According to his hypothesis of molecular vertebrae in 1849, he had found the connection between saturated vapor pressure and temperature. The following year he found some connections between the quantities of temperature, pressure and gas density and described the latent heat after evaporation of a liquid. Rankine correctly predicted that the specific heat of saturated steam would be negative.

Rankine has made an important contribution to elementary understanding in the theoretical field. For example, he introduced the name "energy" for the fundamental physical quantity that was previously known as "life force." He was also the first to describe the transfer of energy in steam engines, for example, as a conversion of heat into kinetic energy.

Rankine stated on the basis of its own theory that the maximum efficiency of thermal motors would depend solely on the temperature fluctuations to which these motors are subject during operation. Prussian Rudolf Clausius developed the Carnot process based on Rankine's ideas. Rankine's work in the field of thermodynamics was resumed by James Clerk Maxwell.

Rankine later reformulated the results of his own theory about the movements of molecules with energy and energy transformation. He claimed that effective energy (real energy) in dynamic processes was lost and replaced by potential energy, an idea that had been known in some way as the law of conservation of energy for some time.

In 1859, Rankine proposed its Rankine scale to measure absolute temperatures.


In the article "Schemes of energy science" of 1855, Rankine intervened in the scientific-philosophical debate on the deductive and inductive method to acquire knowledge and the role of the hypothesis in this. Rankine opined that the hypothesis, which he called hypothetical theory, was only an intermediate step necessary to simplify the consideration of phenomena. This allowed to arrive at a formulation of an abstract theory that can be postulated by induction.

Following his hypothesis of molecular vertebrae and their effect on thermodynamics, Rankine presented a new theory in which dynamics was treated on the basis of energy and the transformation of energy instead of force and movement. With this, he brought all the forces of nature known at that time to a universal theory: a theory of the general law, which regulates every transformation of energy. He called it the science of energy. This theory was often mentioned especially in the second half of the nineteenth century and formed an example for more speculation on this by Ernst Mach and Wilhelm Ostwald, among others.

Mathematical Physics

With contributions to the theory of elasticity and waves, Rankine has made an important contribution to the development of mathematical physics.


Published: February 26, 2020
Last review: February 26, 2020