History of heat
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In the history of science, the history of heat traces its origins to the first hominids to make fire and to speculate on its operation and meaning to modern day particle physicists who study the sub-atomic nature of heat. In short, the phenomenon of heat and definition of what it is evolved from mythological theories of fire, to heat, to terra pinguis, phlogiston, to fire air, to caloric, to the theory of heat, to the mechanical equivalent of heat, to thermo-dynamics (sometimes called energetics) to thermodynamics. The history of heat, then, is a precursor for developments and theories in the history of thermodynamics.
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[edit] Early views
The ancients viewed heat as that related to fire. The Egyptians in 3000 BC viewed heat as related to origin mythologies. One example, is the theory of the Ogdoad, or the “primordial forces”, from which all was formed. These were the elements of chaos, numbered in eight, that existed before the creation of the sun.[1]
The first to have put forward a semblance of a theory on heat was the Greek philosopher Heraclitus who lived around 500 BC in the city of Ephesus in Ionia, Asia Minor. He became famous as the "flux and fire" philosopher for his proverbial utterance: "All things are flowing." Heraclitus argued that the three principal elements in nature were fire, earth, and water. Of these three, however, fire is assigned as the central element controlling and modifying the other two. The universe was postulated to be in a continuous state of flux or permanent condition of change as a result of transformations of fire. Heraclitus summarized his philosophy as: "All things are an exchange for fire."
As early as 460 BC Hippocrates, the father of medicine, postulated that:
| “ | Heat, a quantity which functions to animate, derives from an internal fire located in the left ventricle. | ” |
The hypothesis that heat is a form of motion was proposed initially in the 12th century. Around 1600, the English philosopher and scientist Francis Bacon surmised that:
| “ | Heat itself, its essence and quiddity is motion and nothing else. | ” |
This echoed the mid-17th century view of English scientist Robert Hooke, who stated:
| “ | Heat being nothing else but a brisk and vehement agitation of the parts of a body. | ” |
[edit] 18th century
In 1761, Scottish chemist Joseph Black discovered that ice absorbs heat without changing temperature when melting. From this he concluded that the heat must have combined with the ice particles and become latent. Between 1759 and 1763 he evolved that theory of "latent heat" on which his scientific fame chiefly rests, and also showed that different substances have different specific heats. James Watt, who later invented the Watt engine, was Black's pupil and assistant.
In this direction, the ability to be able to use heat transfer to generate work allowed the invention and development of the steam engine by people such as Thomas Newcomen and James Watt. In addition, in 1797 a cannon manufacturer Sir Benjamin Thompson, Count Rumford, demonstrated through the use of friction it was possible to convert work to heat. To do this, he designed a specially shaped cannon barrel, thoroughly insulated against heat loss, then replaced the sharp boring tool with a dull drill bit, and immersed the front part of the gun in a tank full of water. Using this setup, to the amazement of his onlookers, he made cold water boil in two-and-half-hours time, without the use of fire.[2]
Several theories on the nature of heat were developed. In the 17th century, Johann Becher proposed that heat was associated with an undetectable material called phlogiston that was driven out of a substance when it was burnt. This was finally refuted by Lavosier demonstrating the importance of oxygen in burning in 1783. He proposed instead the caloric theory which saw heat as a type of weightless, invisible fluid that moved when out of equilibrium. It was this theory used in 1824 by the French engineer Sadi Carnot when he published Reflections on the Motive Power of Fire. He set forth the importance of heat transfer: "production of motive power is due not to an actual consumption of caloric, but to its transportation from a warm body to a cold body, i.e. to its re-establishment of equilibrium." According to Carnot, this principle applies to any machine set in motion by heat.[3]
Another theory was the kinetic theory of gases, the basis of which was laid out in 1738 by the Swiss physician and mathematician Daniel Bernoulli in his Hydrodynamica. In this work, Bernoulli first proposed that gases consist of great numbers of molecules moving in all directions, that their impact on a surface causes the gas pressure that we feel.[4] The internal energy of a substance is then the sum of the kinetic energy associated with each molecule, and heat transfer occurs from regions with energetic molecules, and so high internal energy, to those with less energetic molecules, and so lower internal energy.
[edit] 19th century
The work of Joule and Mayer demonstrated that heat and work were interchangeable, and led to the statement of the principle of the conservation of energy by Hermann von Helmholtz in 1847. Clausius demonstrated in 1850 that caloric theory could be reconciled with kinetic theory provided that the conservation of energy was employed rather than the movement of a substance, and stated the First Law of Thermodynamics.
In 1851, William Thomson outlined the essentially modern-view, as based on recent experiments by those such as James Joule on the dynamical theory of heat, that:[5]
| “ | Heat is not a substance, but a dynamical form of mechanical effect. | ” |
On this view, he argued that we must "perceive that there must be an equivalence between mechanical work and heat, as between cause and effect.”[5]
[edit] 20th century
Heat in modern terms, is generally defined as a type of energy transferred due to a temperature difference or that generated by friction, etc.
[edit] See also
[edit] References
- ^ J. Gwyn Griffiths (1955). "The Orders of Gods in Greece and Egypt (According to Herodotus)". The Journal of Hellenic Studies 75: 21–23. doi:.
- ^ Baeyer, H.C. von (1998). Warmth Disperses and Time Passes — the History of Heat. New York: The Modern Library. ISBN 0-375-75372-9.
- ^ Mendoza, E. (1988). Reflections on the Motive Power of Fire — and other Papers on the Second Law of Thermodynamics by E. Clapeyron and R. Clausius. New York: Dover Publications, Inc.. ISBN 0-486-44641-7.
- ^ Mahon, Basil (2003). The Man Who Changed Everything — the Life of James Clerk Maxwell. Hoboken, NJ: Wiley. ISBN 0-470-86171-1.
- ^ a b Thomson, William. (1951). “On the Dynamical Theory of Heat, with numerical results deduced from Mr Joule’s equivalent of a Thermal Unit, and M. Regnault’s Observations on Steam.” Excerpts. [§§1-14 & §§99-100], Transactions of the Royal Society of Edinburgh, March, 1851; and Philosophical Magazine IV. 1852, [from Mathematical and Physical Papers, vol. i, art. XLVIII, pp. 174]
