Piero Bosio Social Web Site Personale

The transition from classical to quantum physics went about as smoothly as you would expect. Happy #QuantumDay!

(Unfortunately, I have no idea who made this classic physics meme. It has been around forever. If you know, please tell me!)

That’s right, the factor of “k” that appears in the formula “S = k log W” — the formula engraved on Boltzmann’s memorial! — was actually introduced by Max Planck. Boltzmann expressed his results in terms of the ideal gas constant R.

Image: user Daderot on Wikipedia

Something that isn’t as widely known is that “h” is not the only fundamental constant that was introduced during Planck’s presentation to the German Physical Society #OTD in 1900!

Planck was investigating emission and absorption by blackbodies, so he needed a way to relate energies and temperatures. Thus, he had to introduce what we now refer to as “Boltzmann’s constant.”

The results of Planck’s December 14th lecture were submitted to Annalen der Physik a few weeks later, on January 7th, and published not long after that.

You can see the original (in German) here:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/andp.19013090310

An English translation of Planck’s paper, taken from Dirk ter Haar’s “The Old Quantum Theory,” is available here:
https://web.archive.org/web/20230529024105/http://hermes.ffn.ub.es/luisnavarro/nuevo_maletin/Planck%20(1900),%20Distribution%20Law.pdf

Planck’s hypothesis was in fact a deep statement about the nature of Nature. Electromagnetic adiation of frequency f comes in discrete chunks of energy E=hf. It's not an artifact of a complicated interaction with matter.

Nowadays we refer to the proportionality constant h as "Planck's constant." In the SI system it takes the value h=6.626 x 10⁻³⁴ kg*m²/s, or 4.136 x 10⁻¹⁵ eV*s.

As far as we can tell, h is a fundamental constant that is hardwired into our Universe.

This sequence of events was a not uncommon narrative in the transformative years of late 19th and early 20th century physics. It would go something like this:

1. An experimental result doesn’t make sense

2. A physicist proposes a radical solution.

3. The solution seems too weird to be real. Everyone assumes it must be a convenient "trick."

4. Eventually, everyone realizes it wasn't a trick, and reality is in fact weirder than they expected.

Here's a great APS Landmarks entry where you can read more about Compton Scattering and the reality of photons.

https://physics.aps.org/story/v13/st8

Many physicists remained skeptical. But Arthur Compton’s 1923 explanation of X-rays scattering off electrons was near-incontrovertible evidence that quanta were real.

If so, it was a trick that *worked*.

Previous efforts to derive the blackbody emission spectrum using classical physics gave nonsensical results at high frequencies. Replace continuous emission with discrete quanta and things work out perfectly.

Evidence for the reality of quanta began with Einstein’s explanation of the photoelectric effect in 1905. The proposal that radiation of frequency f exists only in discrete chunks of energy E=hf was the first result of Einstein’s “Miracle Year.”

Planck’s quantum hypothesis would revolutionize physics, but he initially thought it wasn’t real.

He suspected that the interaction of matter and radiation was tremendously complicated but still governed by the physics known at the time — what we now call “classical physics.”

Invoking quanta of radiation to derive the blackbody emission spectrum was, it seemed to Planck, just a mathematical trick that somehow encapsulated all that complication.

Happy #QuantumDay to all who celebrate!

Max Planck presented work on blackbody radiation to the German Physical Society #OTD in 1900.

His novel “quantum hypothesis” suggested that matter should be treated as it it emits and absorbs light with frequency f only in discrete chunks of energy E=hf.

Image: AIP

Take all that energy use projected for “AI” data centers in the US next year, and that’s about how much work you’d have to do to accelerate a 100kg space probe up to 1/3 the speed of light.

Now, we don’t yet have the technology to do that. But to be fair, we don’t have AI, either.

There’s a big story in Science News on the 100th anniversary of Cecilia Payne-Gaposchkin’s remarkable dissertation. Here’s a thread about her that I wrote a few years ago!
https://mastodon.social/@mcnees/110345032849810344

This morning, during some chaos, this zipped by on one of my feeds. Maybe it was here? Maybe it was BlueSky? Hard to overstate how much this made my day.

https://en.wikipedia.org/wiki/Beaver-engineered_dam_in_the_Czech_Republic

Lolll. Lmao, even.

https://futurism.com/mark-zuckerberg-ai-glasses-demo-fails

For everyone who asked, here’s the full section from the syllabus.

Welp, posted this late last night then logged in and found it’d been around the world and back.

My students are often surprised to learn that LLMs aren’t answering their questions. Rather, an LLM answers the question “what would a reply to this look like?” It’s one of the first things I explain in the “Should I use LLMs?” portion of my syllabus.