The Universal Tendency of Energy

William Thomson’s Struggle with Heat and Work

In 1847, when William Thomson (later Lord Kelvin) (1824–1907) learned of Joule’s experiments (on the mechanical equivalent of heat) demonstrating that work could be converted to heat, he immediately recognized the impact of this discovery. Moreover, it was clear, although not explicitly demonstrated by Joule’s experiments (but nonetheless claimed by Joule), that this equivalence meant that one would expect the conversion of heat into work to be possible as well. This caused problems for Thomson, since at that time, he was still a proponent of caloric theory, which stood in direct opposition to Joule’s conclusion.

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Galileo, The Ingenious Experimenter

A major concept of the book was to connect the science with the actual story around it. This aspect endowed the book with a lot of fascinating science history and biographical information about the scientists. I particularly enjoyed the stories of how Galileo cleverly overcame the many obstacles he encountered when performing his experiments. Enjoy this excerpt from the book.

Galileo Galilei

Galileo Galilei was born the oldest of seven children in Pisa on February 15, 1564 to Vincenzo Galilei and Giulia Ammannati. His father was both a music practitioner and music theorist. Although a number of his compositions were published Vincenzo made only a meager living as a performer and teacher.

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Max Planck’s Rough Road to Quantum Theory

Max Planck’s Early Life

Max Planck (1858–1947) was born in Kiel, (in modern day Germany), the sixth child to the distinguished jurist and professor of law at the University of Kiel, Johann Julius Wilhelm Planck and his second wife, Emma Patzig. His family culture would bestow in Planck’s life and work a sense of excellence in scholarship, incorruptibility, idealism, reliability, and generosity.

In 1867, when Planck was nine, his father received an appointment at the University of Munich. The family moved and Planck enrolled in the city’s Maximilian Gymnasium where his interest in physics and mathematics was piqued. However, Planck excelled in his other studies as well, in particular music. Thus at the time of graduation, now 16, Planck had the difficult decision of choosing a future in either music or physics; he chose physics.
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Energy vs Momentum Conservation

Hints of energy being conserved, much like momentum, were showing up by the 1840s. But unlike momentum conservation, which by comparison was quickly accepted and understood (pretty much by 1687 with Newton’s Principia), energy conservation remained a mystery until 1850.

Heat is “Motion”

In 1798, while boring holes into cannon barrels (as part of the manufacturing process), Count Rumford concluded that heat was the result of some sort of motion within objects.

Feynman on Energy

“It is important to realize in physics today, that we have no knowledge of what energy is … It is an abstract thing in that it does not tell us the mechanism or the reasons …”

Photon Momentum

In 1905, Einstein said light is a particle (photon) with energy proportional to its frequency. Although photon momentum was known much earlier to Einstein, he waited until 1916 to finally declare it.

Energy and Entropy

Energy and the first law that governs it can’t explain why certain processes tend in what apparently is a favored direction; for that we need entropy.

Energy, Entropy and the Universe

Whereas the universe keeps energy at a constant (energy is conserved), it continues to increase the entropy. Therefore, no process that occurs will ever result in an overall decrease in the entropy of the universe. The universes’ tendency of maximizing entropy is reminiscent of “a universal tendency to the dissipation of mechanical energy” as stated by Thomson, and Clausius noted the connection.

Heat is Energy

Heat was the biggest stumbling block to a complete understanding of energy, remaining separate from it until around 1850 when the first law of thermodynamics was inducted.

Confusion About Energy

An understanding of energy in its entirety did not occur until well into the nineteenth century.

Einstein’s Photon

The major theme of Einstein’s 1905 paper, On a Heuristic Point of View Concerning the Production and Transformation of Light, was that light (under certain circumstances) behaves as if it’s comprised of individual particles rather than waves. These particles, or “chunks” of light were originally called light quanta, and then later came to be called photons.

Atomic Energy States are Discrete

The energy states available to atoms and molecules occur at specific intervals. In other words, they are discrete rather than continuous.