Ciro Santilli @cirosantilli 40 

Planck constant Updated 2025-07-16

Proportionality factor in the Planck-Einstein relation between light energy and frequency.

And analogously for matter, appears in the de Broglie relations relating momentum and frequency. Also appears in the Schrödinger equation, basically as a consequence/cause of the de Broglie relations most likely.

Intuitively, the Planck constant determines at what length scale do quantum effects start to show up for a given energy scale. It is because the Plank constant is very small that we don't perceive quantum effects on everyday energy/length/time scales. On the

lim_{h \to 0}

, quantum mechanics disappears entirely.

A very direct way of thinking about it is to think about what would happen in a double-slit experiment. TODO think more clearly what happens there.

Defined exactly in the 2019 redefinition of the SI base units to:

6.62607015 \times 1 0^{- 34} J \cdot s

(1)

Pirates (2005) Updated 2025-07-16

One of the first 1 million USD (zero artistic value) porn movie. And also a piece of shit! Hotter porn has been shot in kitchens around the world using iPhones.

IMDb entry: www.imdb.com/title/tt0477457/.

https://web.archive.org/web/20220330011213im_/https://cps-static.rovicorp.com/2/Open/MTI%20Home%20Video/Pirates%20(2005)/_derived_jpg_q90_310x470_m0/Pirates2005-PosterArt.jpg

Pion Updated 2025-07-16

Conceptually the simplest mesons. All of them have neutral color charge:

charged: down + anti-up or up + anti-down, therefore with net electrical charge $\pm 1$ electron charge
neutral: down + anti-down or up + anti-up, therefore with net electrical charge 0

Physics Videos by Eugene Khutoryansky Updated 2025-07-16

www.youtube.com/user/EugeneKhutoryansky

These videos can give some geometric insight and do have their value.

But they are sometimes too slow, there are never any mention of experiments, just "the truth".

And when things get "mathy", it sticks to a more qualitative view which may not be enough.

Very over the top with sexy demons and angels making appearances, and has some classic aesthetic artistic value :-)

Physics Travel Guide Updated 2025-07-16

physicstravelguide.com/about

DokuWiki about physics, mostly/fully written by Jakob Schwichtenberg and therefore focusing on particle physics, although registration might be open to all.

Physics journal Updated 2025-07-16

The strongest are:

early 20th century: Annalen der Physik: God OG physics journal of the early 20th century, before the Nazis fucked German science back to the Middle Ages
20s/30s: Nature started picking up strong
40s/50s: American journals started to come in strong after all the genius Jews escaped from Germany, notably Physical Review Letters

Physics education needs more focus on understanding experiments and their history Updated 2025-07-16

This is the only way to truly understand and appreciate the subject.

Understanding the experiments gets intimately entangled with basically learning the history of physics, which is extremely beneficial as also highlighted by Ron Maimon, related: there is value in tutorials written by early pioneers of the field.

"How we know" is a basically more fundamental point than "what we know" in the natural sciences.

In the Surely You're Joking, Mr. Feynman chapter O Americano, Outra Vez! Richard Feynman describes his experience teaching in Brazil in the early 1950s, and how everything was memorized, without any explanation of the experiments or that the theory has some relationship to the real world!

Although things have improved considerably since in Brazil, Ciro still feels that some areas of physics are still taught without enough experiments described upfront. Notably, ironically, quantum field theory, which is where Feynman himself worked.

Feynman gave huge importance to understanding and explaining experiments, as can also be seen on Richard Feynman Quantum Electrodynamics Lecture at University of Auckland (1979).

'Making' - the best way of learning science and technology by Manish Jain (2018)

Source.

Physics course of the University of Oxford structure Updated 2025-07-16

Physics bibliography Updated 2025-07-16

Photon polarization Updated 2025-07-16

The knowledge that light is polarized precedes the knowledge of the existence of the photon, see polarization of light for the classical point of view.

The polarization state and how it can be decomposed into different modes can be well visualized with the Poincaré sphere.

One key idea about photon polarization is that it carries angular momentum. Therefore, when an electron changes orbitals in the Schrödinger equation solution for the hydrogen atom, the angular momentum (as well as energy) change is carried out by the polarization of the photon!

Quantum Mechanics 9b - Photon Spin and Schrodinger's Cat II by ViaScience (2013)

Source.

clear animations showing how two circular polarizations can make a vertical polarization
a polarizer can be modelled bra operator.
light polarization experiments are extremely direct evidence of quantum superposition. Individual photons must be on both L and R states at the same time because a V filter passes half of either L or R single photons, but it passes all L + R photons

Photonic quantum computer Updated 2025-07-16

Uses photons!

The key experiment/phenomena that sets the basis for photonic quantum computing is the two photon interference experiment.

The physical representation of the information encoding is very easy to understand:

input: we choose to put or not photons into certain wires or no
interaction: two wires pass very nearby at some point, and photons travelling on either of them can jump to the other one and interact with the other photons
output: the probabilities that photos photons will go out through one wire or another

Jeremy O'Brien: "Quantum Technologies" by GoogleTechTalks (2014)

Source. This is a good introduction to a photonic quantum computer. Highly recommended.

youtube.com/watch?v=7wCBkAQYBZA&t=1285 shows an experimental curve for a two photon interference experiment by Hong, Ou, Mandel (1987)
youtube.com/watch?v=7wCBkAQYBZA&t=1440 shows a KLM CNOT gate
youtube.com/watch?v=7wCBkAQYBZA&t=2831 discusses the quantum error correction scheme for photonic QC based on the idea of the "Raussendorf unit cell"

Photon Updated 2025-07-16

Initially light was though of as a wave because it experienced interference as shown by experiments such as:

But then, some key experiments also start suggesting that light is made up of discrete packets:

Compton scattering, also suggests that photons carry momentum
photoelectric effect
single photon production and detection experiments

and in the understanding of the 2020 Standard Model the photon is one of the elementary particles.

This duality is fully described mathematically by quantum electrodynamics, where the photon is modelled as a quantized excitation of the photon field.

Photomask Updated 2025-07-16

Photoelectric effect Updated 2025-07-16

No matter how hight the wave intensity, if it the frequency is small, no photons are removed from the material.

This is different from classic waves where energy is proportional to intensity, and coherent with the existence of photons and the Planck-Einstein relation.

Photoelectric effect by UCSB Physics Lecture Demonstrations (2021)

Source.

Phi Updated 2025-07-16

Two lower case variants... both used in mathematical notation, and for some reason, in LaTeX \varphi is the one that actually looks like the default standard modern lowercase phi, while \phi is the weird one. I love life.

Phase shift gate Updated 2025-07-16

Phaser.js Updated 2025-07-16

Likely the best JavaScript 2D game engine as of 2023.

github.com/photonstorm/phaser
phaser.io/
phaser.io/examples/v3.85.0/games contains the demo games

Uses Matter.js as a physics engine if enabled. There's also an alternative (in-house?) "arcade" engine: photonstorm.github.io/phaser3-docs/Phaser.Physics.Arcade.ArcadePhysics.html but it appears to be simpler/less robust (but also possibly faster).

TODO any 2D first person examples a bit like Ciro's 2D reinforcement learning games?

The examples are present under:

git clone https://github.com/photonstorm/phaser3-examples

but note that that repo is huge, about 4.5 GiB on local disk, as is has tons of assets.

The demos also include a Monaco-editor based sandbox mode where you can edit code directly on the web and see the game update which is a really sweet addition.

Phagocytosis Updated 2025-07-16

Peter Todd's hash collision puzzles Updated 2025-07-16

As mentioned at the prize was claimed at 8d31992805518fd62daa3bdd2a5c4fd2cd3054c9b3dca1d78055e9528cff6adc (2017-02-23) which spends several inputs with the same unlock script that presents two different constantants that have the same SHA-1:

printf 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 | xxd -r -p | sha1sum
printf 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 | xxd -r -p | sha1sum

both giving

f92d74e3874587aaf443d1db961d4e26dde13e9c

It was claimed on the same day that Google disclosed the collision: security.googleblog.com/2017/02/announcing-first-sha1-collision.html

Both of these are PDF prefixes, so they start with the PDF file signature, but are not fully viewable PDFs on their own.