Energy and Thermal Physics

The bloody principle of conservation of energy

Stories from Physics for 11-14 14-16 IOP RESOURCES

The principle of conservation of energy seems to have been developed by a number of scientists working independently around the same time. One of the earliest statements was proposed by a German doctor, Julius Robert Mayer, who served as a ship’s physician in the tropics.

Mayer noted that venous (deoxygenated) blood in the tropics appeared to be unusually red and he hypothesised that someone living in a hot region required less oxygen than a person in a cooler climate. This train of thought led the doctor to consider the relationship between the consumption of food and bodily exertion. Using the term ‘force’ as an explanatory principle for phenomena such as growth and motion in humans, in 1841 Mayer formulated a conservation statement:

Forces, like matter, are quantitatively invariable… motion, heat and… electricity are phenomena which can be explained by a single force… and can be transformed into one another in accordance with definite laws. Motion is transformed into heat by being neutralised by an opposite motion.

However, his idea received little attention at the time, perhaps because he was forced to self-publish some of his work.

Tragically for Mayer, at the same time as the scientific community showed indifference to his work, he lost three of his children and he attempted suicide by jumping from a window, leaving him permanently lame. He was admitted to a mental asylum for a time, but after leaving, Mayer found that his scientific reputation had flourished and he continued to work as a physician till his death in 1878.



appears in the relation ΔEΔt>ℏ/2 ΔQ=mcΔθ E=hf E ∝ A^2
has the special case Photon Energy
is used in analyses relating to Emission/Absorption Spectra Phase Change
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