The Significance of Statistical &Thermal Physics to Physics & to Science in General

Some comments on the importance of Statistical & Thermal Physics from some famous physicists. Also, some brief history & more trivia.

To put the following in context, the historical acceptance of the atomic hypothesis & the importance of & acceptance of Statistical Mechanics (in the late 1800’s & early 1900’s) are strongly connected. Ludwig Boltzmann played a primary role in both, but he was also a tragic figure, as we’ll see.

Importance of Thermodynamics + Some History Quote from The Feynman Lectures on Physics Volume 1, Chapter 1. Feynman is discussing the fundamental importance of the atomic hypothesis to physics: “If, in some cataclysm, all of scientific knowledge were to be destroyed, & only one sentence passed on to the next generations of creatures…I believe it is the atomic hypothesis…all things are made of atoms; little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another”. Richard P. Feynman (1918-1988)

Physics I: “Heat is a Form of Energy” James Joule’s Experiment Mgh = W = Q & Q = mcT Work can raise the water temperature. Joule’s Experimental Setup James Joule (1818-1889)

Carnot: “Engine of Highest Possible Efficiency” Nicolas Léonard Sadi Carnot (1796-1832) Some history:“Carnot” is the name of a famous French family in both politics & science.

President of France, 1887–1894 The Carnot Family Lazare Nicolas Marguerite Carnot (1753-1823), mathematician & politician. Nicolas Léonard Sadi Carnot (1796-1832), mathematician & eldest son of Lazare, a pioneer of thermodynamics. Hippolyte Carnot (1801-1888), politician & second son of Lazare. Marie François Sadi Carnot (1837-1894), son of Hippolyte, President of France, 1887–1894 Marie Adolphe Carnot (1839-1920), son of Hippolyte, mining engineer & chemist. A number of streets etc. are named after this family throughout France. Nicolas Léonard Sadi Carnot (1796-1832)

Ludwig Boltzmann (1844-1906) But, he also constantly battled for Boltzmann introduced probabilities into a fundamental law of physics. Thus, in his Statistical Mechanics interpretation of the 2nd Law of Thermo, he broke with the classical view that fundamental laws have to be strictly deterministic. “With his work, the probabilistic interpretation of quantum mechanics had already a precedent.” But, he also constantly battled for acceptance of his work.

Importance of the Atomic Hypothesis Boltzmann's contribution to 19th Century science was vital, but it had a tragic outcome! At the end of the 19th century, several puzzling facts (which eventually led to quantum theory), triggered a reaction against 'materialist' science. Some people questioned whether atoms exist! Boltzmann, whose statistical physics work on gases was based on the atomic concept, found himself cast as their chief defender & the debates became increasingly bitter & personal. Ludwig Boltzmann (1844-1906)

Ludwig Boltzmann (1844-1906) Boltzmann constantly battled for acceptance of his work. He also struggled with poor health. Prone to bouts of depression, Boltzmann came to believe that his life's work had been rejected by the scientific community. Boltzmann

Ludwig Boltzmann (1844-1906) But, this wasn’t true! Boltzmann constantly battled for acceptance of his work. He also struggled with poor health. Prone to bouts of depression, Boltzmann came to believe that his life's work had been rejected by the scientific community. Boltzmann But, this wasn’t true!

Tragically, in 1906, he committed suicide! Ludwig Boltzmann (1844-1906) Boltzmann constantly battled for acceptance of his work. He also struggled with poor health. Prone to bouts of depression, Boltzmann came to believe that his life's work had been rejected by the scientific community. Boltzmann But, this wasn’t true! Tragically, in 1906, he committed suicide! Many believe that Statistical Physics was the cause.

Boltzmann’s Gravestone Boltzmann’s Entropy Formula Vienna, Austria

More Tragic History! Paul Eherenfest was Boltzmann’s PhD student.

More Tragic History! Paul Eherenfest was Boltzmann’s PhD student. He delivered Boltzmann’s eulogy & carried on the development of Statistical Thermodynamics for nearly 3 decades.

More Tragic History! Paul Eherenfest was Boltzmann’s PhD student. He delivered Boltzmann’s eulogy & carried on the development of Statistical Thermodynamics for nearly 3 decades. Similar to his mentor Boltzmann, he was filled with self- doubt & was deeply troubled by the disagreements between his friends (Bohr, Einstein, etc.) which arose during the development of quantum mechanics.

Eherenfest shot himself to death in 1933!! More Tragic History! Paul Eherenfest was Boltzmann’s PhD student. He delivered Boltzmann’s eulogy & carried on the development of Statistical Thermodynamics for nearly 3 decades. Similar to his mentor Boltzmann, he was filled with self- doubt & was deeply troubled by the disagreements between his friends (Bohr, Einstein, etc.) which arose during the development of quantum mechanics. Eherenfest shot himself to death in 1933!!

More Tragic History! “Ludwig Boltzmann, who spent much of his life Studying Statistical Mechanics, died in 1906 by his own hand”.

More Tragic History! “Ludwig Boltzmann, who spent much of his life Studying Statistical Mechanics, died in 1906 by his own hand”. “His student, Paul Ehrenfest, carrying on Boltzmann’s work, died similarly in 1933”.

More Tragic History! “Ludwig Boltzmann, who spent much of his life Studying Statistical Mechanics, died in 1906 by his own hand”. “His student, Paul Ehrenfest, carrying on Boltzmann’s work, died similarly in 1933”. “Now it is our turn to study statistical mechanics. Perhaps it will be wise to approach the subject cautiously”.

More Tragic History! “Ludwig Boltzmann, who spent much of his life Studying Statistical Mechanics, died in 1906 by his own hand”. “His student, Paul Ehrenfest, carrying on Boltzmann’s work, died similarly in 1933”. “Now it is our turn to study statistical mechanics. Perhaps it will be wise to approach the subject cautiously”. From the book “States of Matter” by David L. Goodstein (Dover, 1985)

Still More Tragic History! US physicist Percy Bridgmann (on right in photo below), who had been a post-doc of Ehrenfest, was a 1946 Nobel Physics Prize winner. He was a thermal & statistical physics pioneer. He studied the physics of matter under high pressures.

Still More Tragic History! Bridgman committed suicide in 1961! US physicist Percy Bridgmann (on right in photo below), who had been a post-doc of Ehrenfest, was a 1946 Nobel Physics Prize winner. He was a thermal & statistical physics pioneer. He studied the physics of matter under high pressures. Bridgman committed suicide in 1961!

Still More Tragic History! Bridgman committed suicide in 1961! US physicist Percy Bridgmann (on right in photo below), who had been a post-doc of Ehrenfest, was a 1946 Nobel Physics Prize winner. He was a thermal & statistical physics pioneer. He studied the physics of matter under high pressures. Bridgman committed suicide in 1961! There’s no need to worry! I’ve never known a student who didn’t survive a course in thermal & statistical physics!!

Robert Brown & Brownian Motion Observed irregular movement of pollens in water under a microscope. [1st observation of “Brownian motion”: S. Gray, Phil. Trans. 19, 280, (1696).] Brown’s Major Contribution He proved that non-organic particles also have Brownian motion. Thus, Brownian motion is not a manifestation of life. Robert Brown (A botanist!)

Einstein, Brownian Motion, & Atomic Hypothesis “The Miracle Year” Einstein published 4 papers in the Annalen der Physik in 1905. The Photoelectric Effect Brownian Motion Special Theory of Relativity Which topic was his PhD Thesis? Which topic was his Nobel Prize? Albert Einstein 1905

Einstein on Thermodynamics “A theory is the more impressive the greater the simplicity of its premises, and the more extended its area of applicability”. “Classical thermodynamics… is the only physical theory of universal content which I am convinced that, within the applicability of its basic concepts, will never be overthrown”. Albert Einstein 27

Eddington on Thermodynamics “If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations – then so much the worse for Maxwell’s equations”. “But if your theory is found to be against the second law of thermodynamics I can offer you no hope; there is nothing for it but to collapse in deepest humiliation.” Sir Arthur Eddington, 1929 28 28