Understanding Heat Energy

The concerted unrelenting  systematic attempts  and the rational attitudes  of  scientific brains during the centuries following Renaissance  to understand the rules of physical universe are most wonderful and quite awe inspiring. As an example let us see how studies on the phenomenon of heat developed  in their studies. To understand what heat is(the heat we get from flames and fires, the endless heat coming from sun, the nature of hot

bodies particularly metals ,the phenomenon of melting and boiling, heat radiation coming from hot hill sides and hot boulders during hot summers etc) all these made them think.

Necessary environment was already created by very accurately defining  primary physical units for Length, Mass and Ttime  and secondary units like Density and Pressure etc, by the  invention of physical and chemical balances, study of chemical reactions and search for chemically  pure substances etc

Simultaneously with these studies, the studies about “Heat” were also conducted. Soon they wanted units to measure all types of phenomena relating to heat. Firstly  to start a very systematic study of heat, the recognizing of “melting point of ice” and  “boiling point of water” as “standard heat levels” helped a lot. The scientific people invented a mercury thermometer  marked the mercury levels  of melting point of ice and boiling point of water on it and divided the distance in between them into one hundred degrees. The investigators might first have been wonderstruck when they saw that when ice melted or water boiled the mercury level did not change until the change of state ended. They found the stoppage of temperature during the melting and boiling processes to be true for all pure solids, crystals and liquids. It must have been treated as a great discovery indeed!.

 Defining unit of temperature was a great step forward. But from here we should go by big  leaps to reach the modern age in Physics. Temperature was only heat level. They could not fully realize that heat was a form of energy. They treated it as some thing like a fluid, like the water hiding inside wet cloth. It was called caloric fluid. When one heated an iron ball the  caloric fluid goes on filling the sphere just as water poured into a drum slowly fills it! To measure this caloric fluid they defined a unit quantity—the mysterious  “caloric fluid” that would newly enter inside a gram of water when it is heated by one degree. This unit quantity of the invisible caloric fluid was called calorie. The most important idea (which we now know as utterly wrong) was that each homogenous solid substance ,whether a metal, wood, rubber,  stone etc all should have very specific “heat capacity”( heat absorbing capacity) peculiar to that substance.

A French scientist –engineer Count Rumford  proved this idea to be wrong. He accidentally observed with wonder  that a  small but thick solid piece of  iron fixed in a frame when it is subjected to very strong friction (as when being bored into thick-walled  tubes for making guns) release large unlimited quantities of heat for unlimited time  not in keeping with the  small size of the iron piece. Drums of water could be heated by the heat coming out of the friction from this small iron piece!

So scientists soon found the caloric theory to be  wrong. They came to conclusion that heat is a kind of energy like kinetic energy (energy possesses by objects in motion like fly wheels, heavy objects falling down). Soon scientists started to study heat as radiant energy coming from hot bodies like Sun,.fires,other hot objects radiating heat into cooler sorroundings etc. Once heat is received by direct contact with a hot body or absorbed from a distant body by radiation, it starts to flow in the bodies from one molecule to another by conduction and convection. Scientists came to the conclusion that all objects above “-273 degrees centigrade” radiate heat energy. Not only hot objects but even cold objects radiate energy if they are above “-273 degrees centigrade”. It is a two way process every moment in entire physical world.

The next big step was the effect of study of electro magnetic spectrum. After the velocity of Light radiation as calculated purely from optical calculations exactly matched the velocity of “theoretical electromagnetic radiations” calculated by Prof Clerk Maxwell, it was realized that heat energy is a fundamental form of electromagnetic radiation energy.The very great researches in spectroscopy, the discovery of electron,radioactivity and x-rays and the most fundamental researches of Dr. Einstein on nature of matter and energy and discovery that velocity of light is the ultimate limit for velocity etc ---all these researches once for all changed man's outlook on matter and energy. the entire range of electromagnetic spectrum was understood and heat was found to be just a part of it  and occurring near the infrared range.

It was a great luck for scientific community that Dr.Max Planc of Germany  propounded that heat waves travel as “quanta”( i.e as little fixed size pieces of the long wave and not as continuous waves, just like fixed size pieces cut from an endless reel of sewing thread). He had to do this to satisfactorily explain some anomalies in experiments on heat radiation beyond experimental error. This new idea of propagation of heat in fixed size “quanta” was forgotten entirely for a few decades. After Dr. Rutherford declared that electrons should orbit a positive heavy nucleus but could not explain some anomalies in r/o of Hydrogen spectrum Dr Niels Bohr with his extraordinary intellect and with the help of certain existing radiation formulas(like Lyman,Balmer and Paschen series relating to proved laboratory experiments on hydrogen spectra) applied quantum theory very successfully to all electromagnetic radiations including heat radiation.

So finally we understand nature of Heat energy. It is the ever present radiation easily recognizable in most chemical reactions (including the chemical reactions we encounter everyday every where in nature) or in ordinary heating of objects. Heat radiation like any other electromagnetic radiation is given out when electrons jump out ward from high-energy inner orbits to lower energy outer orbits in atoms comprising all matter.    

BY SASTRY POLAVARAPU (Admin at PDEP)