The First Quantum Mechanic

Max Planck was the first quantum mechanic.  He began as an "old school" mechanic, thoroughly steeped in Newtonian mechanics and Maxwell's electrodynamics; those laws conveniently sorted physics into the "corpuscular" and the "ethereal" domains, a dichotomy that corresponded to things having mass and things lacking mass, i.e., radiant light. Higgs had something to say about this later.

Isaac Newton had solved the age-old riddle of why apples fall, allowing astronomers to predict the motions of the heavens. Miracle, mystery and authority. Newton also dabbled in light, describing reflection and interference--along with his famous prism experiments--but the mathematical laws governing light propagating "through the ether" were first described by a Scotsman, James Clerk Maxwell. Newton's Laws of Gravitation governed masses while Maxwell's electrodynamics ruled the waves. Planck came along in 1900 and sort of melded the two theories at their interface.

Physics then had a big unsolved problem called "black body radiation." Heating kilns and ovens made the inside walls glow--first red, then yellow, and finally white hot. Glass makers and potters could even gauge an oven's temperature based on its color inside. Adding more heat to an oven made the walls give off progressively higher energy light but there was a limit: ovens would not begin to emit UV light. Light bulbs were another 19th century invention that used heat (electrical resistance) to produce light and Planck was motivated in part by practical concerns.

What Planck did can be summarized visually with a plot of light intensity versus wavelength:

Planck's theoretical curves (berechnet) agreed beautifully with experiment (beobachtet). Note that there are seven different non-overlapping curves corresponding to progressively higher temperatures. Prior attempts to predict the same phenomenon, based on classical electrodynamics, had failed. These attempts are neatly summarized in this graphic:

The green line corresponds to Planck's law and to reality; the red line, Rayleigh-Jeans Law, only worked at low frequencies (long wavelengths), while the blue line, Wien's Law, worked only at the high frequencies (short wavelengths).  As an aside, the red line's straight up ascent was later referred to as the "Ultraviolet Catastrophe" as a sort of metaphor for the failure of classical theory to account for the reality of Planck's Law. But Planck did more than meld two theories--he invented anew.

The newer science of thermodynamics and Maxwell Boltzmann in particular had shown that tiny invisible yet indivisible atoms could statistically sum to bulk properties. The details are grounded in probabilities rather than certainties, much like my Parable Of The Gas. What Planck did was to apply Boltzmann-like statistical mechanics to the problem of black body radiation.

Planck viewed a red-hot oven (black body radiator) as material in equilibrium with light--sort of a transubstantiation of the ethereal and corpuscular. He named the nexus--the unseen--"resonators" and counted them in a statistical way, describing their behavior mathematically. This was all well before anyone knew or even thought that atoms were held together by electrons--atoms were still thought to be amorphous blobs. That something as seemingly seamless as light should be treated like discrete masses when it interacted with matter was an assumption but it proved key to deriving the solution to the black body problem. There was no other way to explain the behavior. What Planck did was revolutionary, but he did not do it because he understood why--he did it because his theory fit experiment. Werner Heisenberg later stated Planck's insight most succinctly and in most certain terms:

Radiant heat is not a continuous flow and indefinitely divisible. It must be defined as a discontinuous mass made up of units all of which are similar to one another. 

Around the time of Planck's insight, another, younger German physicist appeared on stage. He was then a Swiss patent examiner and barely known, preoccupied with developing his own theories of relativity, but his elastic mind intuitively wrapped around what even Planck had trouble fully accepting and generalizing.  Einstein took Planck's teachings and explained the photoelectric effect--why blue light but not red light could make certain metals conduct electricity. It seemed counter intuitive that even the most intense red light could not do what the faintest of blue light could do. Einstein explained that only blue light was energetic enough to knock electrons free. There were energy thresholds and band gaps at the atomic level. Discontinuities and E=hv.

According to Thomas Kuhn, Planck needed the goading of Einstein and Paul Ehrenfast afterwards to fully realize what he had done. Certainly Planck's older contemporaries were doubters too. In Planck's words:

A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.

Planck and Einstein remained close friends throughout the 1930's. Planck, conservative Christian, and Einstein, agnostic Jew, enjoyed making music together when not discussing physics in Wilhelmine and Weimar Berlin--while it lasted (maybe they did discuss the physics of music--frequencies, harmonics, metered beats). Planck tried in vain to intervene on his friend's behalf during the rise of the Nazi regime but he ultimately failed.

There was even greater sadness for Planck besides the exile of his great friend Einstein; there was the trial of his eldest son Erwin at the hands of Roland Freisler, whom I described back here. The Nazis executed Erwin Planck just a few heartbreaking months before the whole regime finally collapsed. The older Planck never recovered from the loss of Erwin and died just two years later in 1947. Here they are during happier times:

Max and son Erwin Planck

Erwin Planck on trial for his life before the People's Court, arrested and charged as part of the July conspiracy to assassinate Hitler:

Erwin Planck vor dem Gesezt in 1945

Erwin Planck, like so many others, was only involved in aftermath planning--helping to draft a post-Hitler German Constitution--and not the actual assassination plot.

The elder Planck's life sort of tracked a shape: A half-century of slow triumph peaked in the 1930's and then precipitously declined, much like the shape of one of his triumphant black body radiation curves which conquered physics. Post-war Germany honored Planck by renaming the Kaiser-Wilhelm-Gesellschaft (its premier scientific society) the Max-Planck-Gesellschaft.

Parable Of The Gas Explained

A while back I wrote The Parable Of The Gas without explanation:

Consider a spherical, sealed glass container of gas. Further suppose that the gas inside is all the same -like helium in a balloon. Room temperature and stable. Everything equal inside...but it's not. The individual gas atoms in the container have unequal energies because there's a range--a statistical distribution--of energies present: Some atoms move more slowly than others, some more quickly, some much more quickly.

How can we make things fair? How can we make it such that each individual (atom) has the same energy as its next nearest neighbor? We cannot. The only way to approach that state is to remove energy from the entire system. Cool the economy. Everything slows. Eventually, approaching zero Kelvin, all motion stops. Of course catastrophic things like condensation (downsizing from gas to liquid) and solidification (loss of liquidity) occur along the way. But the goal is achieved: every atom is finally the same (or nearly the same) energy wise.

Here is what I was picturing:

Original

The figure shows how at higher temperatures the average speed increases but so does the spread (inequality). The range narrows at lower temperatures which is what some policymakers seem to want. But what they want is also unnatural and contrived. An Austrian physicist named Ludwig Boltzmann first came up with the mathematical model behind all this in 1877. He based his derivation on entropy--arguing that a situation where all members of a group have identically the same velocity is highly improbable--as improbable as all the gas molecules being located on just one side of the vessel. It's much more probable (favorable) to allow each member of the group to experience a range of velocities and not to constrain them into one single energy or spatial configuration.

Another physicist named Max Planck extended Boltzmann's ideas and also changed the world by extending statistical mechanics to heat and light thus introducing quantum mechanics.  Einstein ran even further with Planck's ideas.  Both men would have their doubts--"God doesn't roll dice" and all that--but neither man denied reality.

Added:  When I liken the economics of wealth and poverty to a gas, it's important to remember that "rich" and "poor" may interconvert: link

A Conservative Notion of Mass*

I find the designation of the Higgs Boson particle as the "God Particle" amusing. Amusing because I associate God particles with the lighter particles--the ones that defy measurement by virtue of their zero-point energy.

Zero-point energy is like Freud's terms das Ich, das Es, and das Über-Ich, which resounded better in German. As originally posited by Einstein, zero-point energy is that residual energy present in matter even at absolute zero Kelvin.  Those who don't believe in absolutes should ponder temperature scales--there are no negative degrees Kelvin. Anyway, even at zero Kelvin, atoms like hydrogen, the most abundant element, still have energy. If uncertain as to why, consult Heisenberg.
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*Lavoisier gave us the notion of Conservation of Mass--before he was beheaded by his government.

The Discovery of the Electron

"The electron has conquered physics, and many adore the new idol rather blindly" 

Henri Poincaré (1907)

After the discovery of the electron and the measurements of its mass and charge (a combination of Thomson's and Millikan's truly ingenious experiments), the next big question was how to describe and understand electrons in atoms and molecules.

Bring on the dream team:

There is a bigger version of the photo with the names of the scientists listed beneath here.