# A Brief History of Entropy pt. 1 – The Doctor and the Brewer

### Prologue

Tanzania, circa 3,000,000,000 B.C.

A small group of apes are staring in front of an enourmous deep black monolith. No light is reflected nor emitted by it. They frown at this unusual, unnecessary, inconceivable stone. How could it be? Of course they are puzzled: they know that nothing in the World can be that black, it must emit something according to Hawing’s radiation. Everybody knows Stephen Hawking!

### Bloody Hot

1840, East Indies, Djakarta

A Dutch sailor is doing bad. The ship’s surgeon, a 26 years old german doctor whose name is Rober Mayer takes the decision to spill some blood out of him. But hey, wait a moment, this blood is bright red! He must have lanced an artery instead of a vein! Indeed, dr. Mayer knows how to do it very well. It’s just different than in Ole Europe, where our venous blood is dark rather than bright.

After a lot of thinking, Mayer realized that this is because at the tropics humans consume less food (it’s actually oxygen) than in the temperate regions. At the tropics it’s hot…bloody hot! The higher the outside temperature, the lower the body temperature, the lower the food consumption. Is there a relationship between food and temperature?

Unfortunately for our young doctor, he wasn’t so good with math, so his clumsy paper was firmly rejected. He messed up with forces, energy and heat. Too bad, but his idea was stunning: energy can not be created nor destroyed, only transformed.

1834, Manchester, England

Two kids, James and Benjamin are sent to the Manchester Literary and Philosophical Society to study with John Dalton (curiosly, the original venue burned down in a fire during the bombing of Manchester in 1940). At that time, Dalton was studying the gases. In the end, he convinced himself that their properties could be explained by postulating the existence on small, elementary units called atoms. A chemical reaction simply changes the way atoms are grouped together. James and Benjamin are fascinated by Dalton’s ideas and by the newly discover electricity. James inherited their father’s brewery, but still he was committed to do Science at his best (eventually he decided to sell the business in 1854). In 1845 John Prescott Joule published a paper called On the mechanical equivalent of heat. In this paper he demonstrated how much mechanical work is needed in order to increase water temperature by one degree. Now, the point is that Mayer predicted this value, but nobody believed him unti this value was actually measured! Poor Mayer, he went crazy and was sent into asylum several times. After many years, in 1863 John Tyndall wrote “Heat: A mode of motion” and Mayer’s work was finally vindicated.

So let it be written, so let it be done

After much work, eventually the idea of the conservation of energy was finally stated and applied to heat, giving rise to the so called first law of thermodynamics:

$\Delta U = Q - W$

The change of internal energy of a system is equal to the difference between the heat transferred to the system and the work perfomed by the system.