The Significance of Statistical Thermal Physics to Physics

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, some tragedies.

• To put the following in context, the historical acceptance of the atomic hypothesis & the importance of & acceptance of Statistical Mechanics (late 1800’s & early 1900’s) are strongly connected. • Ludwig Boltzmann played a primary role in both.

But, Ludwig Boltzmann was also a very 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 Richard P. a little distance apart, but repelling Feynman upon being squeezed into one another”. (1918 -1988)

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

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.

The Carnot Family, Part I • 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 (18011888), politician & second son of Lazare.

The Carnot Family, Part II • Marie François Sadi Carnot (1837 -1894), son of Hippolyte, President of France, 1887– 1894 • Marie Adolphe Carnot (1839 Nicolas Léonard Sadi Carnot 1920), son of Hippolyte, (1796 -1832) mining engineer & chemist. • A number of streets etc. are named after this family throughout France.

Ludwig Boltzmann (1844 -1906) • Boltzmann introduced probabilities into a fundamental law of physics. Thus, in his Statistical Mechanics interpretation of the 2 nd 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 19 th Century science was vital, but it had a tragic outcome! • At the end of the 19 th century, several puzzling facts (which eventually led to quantum theory), triggered a reaction against 'materialist' science. Some people questioned whether atoms exist! Ludwig Boltzmann (1844 -1906)

Importance of the Atomic Hypothesis Boltzmann's contribution to 19 th Century science was vital, but it had a tragic outcome! • 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. But, this wasn’t true!

Ludwig Boltzmann (1844 -1906) But, this wasn’t true! Tragically, in 1906, he committed suicide! Boltzmann Many believe that Statistical Physics was one of the causes.

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

More Tragic History! • Paul Eherenfest was Boltzmann’s Ph. D student.

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

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

More Tragic History! • Paul Eherenfest was filled with self- doubt & was prone to bouts of depression. • He was very troubled by the disagreements between his friends which arose during the development of Quantum Theory. He 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! • 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! • 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 Brown (1827) Observed irregular movement of pollens in water under a microscope. [1 st observation of “Brownian motion”: S. Gray, Phil. Trans. 19, 280, (1696). ] Brown’s Major Contribution Robert Brown He proved that non-organic (A botanist!) particles also have Brownian motion. Thus, Brownian motion is not a manifestation of life.

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 Albert Einstein • Which topic was his Ph. D Thesis? 1905 • Which topic was his Nobel Prize?

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

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 30