A New Method of Measuring Nuclear Magnetic Moment Updated +Created
Physical Review Volume 53, page 318.
Not paywalled as of 2024! A miracle! It is barely one page long.
This is the paper that contains the first successful report of experimental nuclear magnetic moment observation.
They promise more at the end:
We have tried this experiment with LiC1 and observed the resonance peaks of Li and Cl. The effects are very striking and the resonances sharp (Fig. 1). A full account of this experiment, together with the values of the nuclear moments, will be published when the homogeneous field is recalibrated.
and this promise was fulfilled on the later The Molecular Beam Resonance Method for Measuring Nuclear Magnetic Moments.
Figure 1. .
This figure sums it all up: they were measuring the intensity of one side of a molecular beam after a Stern-Gerlach experiment.
Then, they vary the constant magnetic field before the splitting, and at the same time apply a fixed radio frequency to the beam.
When the constant magnetic field makes the energy gap match the radio frequency input, nuclear spin of many atoms goes to the anti-aligned direction, the beam gets diverted, so the previously detected beam gets weaker.
Molecular beam Updated +Created
Molecular beams are cool because they create a one dimensional flow of molecules, which makes it easier to observe certain single-molecule effects, as it removes the multi-particle issues from experiments.
Key molecular beam experiments include:
The center piece of the control system of atomic clocks is a molecular beam.
Public domain scientific paper by year Updated +Created
Here we list public domain academic papers. They must be public domain in the country of origin, not just the US, which had generally less stringent timings with the 95 year after publication rule rather than life + 70, which often ends up being publication + 110/120. Once these are reached, they may be upload to Wikimedia Commons!
Quantum entanglement Updated +Created
Quantum entanglement is often called spooky/surprising/unintuitive, but they key question is to understand why.
To understand that, you have to understand why it is fundamentally impossible for the entangled particle pair be in a predefined state according to experiments done e.g. where one is deterministically yes and the other deterministically down.
In other words, why local hidden-variable theory is not valid.
How to generate entangled particles:
Video 1.
Bell's Theorem: The Quantum Venn Diagram Paradox by minutephysics (2017)
Source.
Contains the clearest Bell test experiment description seen so far.
It clearly describes the photon-based 22.5, 45 degree/85%/15% probability photon polarization experiment and its result conceptually.
It does not mention spontaneous parametric down-conversion but that's what they likely hint at.
Done in Collaboration with 3Blue1Brown.
Question asking further clarification on why the 100/85/50 thing is surprising: physics.stackexchange.com/questions/357039/why-is-the-quantum-venn-diagram-paradox-considered-a-paradox/597982#597982
Video 2.
Bell's Inequality I by ViaScience (2014)
Source.
Video 3.
Quantum Entanglement & Spooky Action at a Distance by Veritasium (2015)
Source. Gives a clear explanation of a thought Bell test experiments with electron spin of electron pairs from photon decay with three 120-degree separated slits. The downside is that he does not clearly describe an experimental setup, it is quite generic.
Video 4.
Quantum Mechanics: Animation explaining quantum physics by Physics Videos by Eugene Khutoryansky (2013)
Source. Usual Eugene, good animations, and not too precise explanations :-) youtu.be/iVpXrbZ4bnU?t=922 describes a conceptual spin entangled electron-positron pair production Stern-Gerlach experiment as a Bell test experiments. The 85% is mentioned, but not explained at all.
Video 5.
Quantum Entanglement: Spooky Action at a Distance by Don Lincoln (2020)
Source. This only has two merits compared to Video 3. "Quantum Entanglement & Spooky Action at a Distance by Veritasium (2015)": it mentions the Aspect et al. (1982) Bell test experiment, and it shows the continuous curve similar to en.wikipedia.org/wiki/File:Bell.svg. But it just does not clearly explain the bell test.
Video 6.
Quantum Entanglement Lab by Scientific American (2013)
Source. The hosts interview Professor Enrique Galvez of Colgate University who shows briefly the optical table setup without great details, and then moves to a whiteboard explanation. Treats the audience as stupid, doesn't say the keywords spontaneous parametric down-conversion and Bell's theorem which they clearly allude to. You can even them showing a two second footage of the professor explaining the rotation experiments and the data for it, but that's all you get.
Spin experiments Updated +Created
Trapped ion quantum computer Updated +Created
TODO understand.
Video 1.
Trapping Ions for Quantum Computing by Diana Craik (2019)
Source.
A basic introduction, but very concrete, with only a bit of math it might be amazing:
Sounds complicated, several technologies need to work together for that to work! Videos of ions moving are from www.physics.ox.ac.uk/research/group/ion-trap-quantum-computing.
A major flaw of this presentation is not explaining the readout process.
Video 2.
How To Trap Particles in a Particle Accelerator by the Royal Institution (2016)
Source. Demonstrates trapping pollen particles in an alternating field.
Video 3.
Ion trapping and quantum gates by Wolfgang Ketterle (2013)
Source.
Video 4.
Introduction to quantum optics by Peter Zoller (2018)
Source. THE Zoller from Cirac–Zoller CNOT gate talks about his gate.
Two-state quantum system Updated +Created
Discrete quantum system model that can model both spin in the Stern-Gerlach experiment or photon polarization in polarizer.
Also known in quantum computing as a qubit :-)
Videos of all key physics experiments Updated +Created
It is unbelievable that you can't find easily on YouTube recreations of many of the key physics/chemistry experiments and of common laboratory techniques.
Experiments, the techniques required to to them, and the history of how they were first achieved, are the heart of the natural sciences. Without them, there is no motivation, no beauty, no nothing.
School gives too much emphasis on the formulas. This is bad. Much more important is to understand how the experiments are done in greater detail.
The videos must be completely reproducible, indicating the exact model of every experimental element used, and how the experiment is setup.
A bit like what Ciro Santilli does in his Stack Overflow contributions but with computers, by indicating precise versions of his operating system, software stack, and hardware whenever they may matter.
It is understandable that some experiments are just to complex and expensive to re-create. As an extreme example, say, a precise description of the Large Hadron Collider anyone? But experiments up to the mid-20th century before "big science"? We should have all of those nailed down.
We should strive to achieve the cheapest most reproducible setup possible with currently available materials: recreating the original historic setup is cute, but not a priority.
Furthermore, it is also desirable to reproduce the original setups whenever possible in addition to having the most convenient modern setup.
Lists of good experiments to cover be found at: the most important physics experiments.
This project is to a large extent a political endeavour.
Someone with enough access to labs has to step up and make a name for themselves through the huge effort of creating a baseline of amazing content without yet being famous.
Until it reaches a point that this person is actively sought to create new material for others, and things snowball out of control. Maybe, if the Gods allow it, that person could be Ciro.
Tutorials with a gazillion photos and short videos are also equally good or even better than videos, see for example Ciro's How to use an Oxford Nanopore MinION to extract DNA from river water and determine which bacteria live in its for an example that goes toward that level of perfection.
The Applied Science does well in that direction.
This project is one step that could be taken towards improving the replication crisis of science. It's a bit what Hackster.io wants to do really. But that website is useless, just use OurBigBook.com and create videos instead :-)
We're maintaining a list of experiments for which we could not find decent videos at: Section "Physics experiment without a decent modern video".
Ciro Santilli visited the teaching labs of a large European university in the early 2020's. They had a few large rooms filled with mostly ready to run versions of several key experiments, many/most from "modern physics", e.g. Stern-Gerlach experiment, Quantum Hall effect, etc.. These included booklets with detailed descriptions of how to operate the apparatus, what you'd expect to see, and the theory behind them. With a fat copyright notice at the bottom. If only such universities aimed to actually serve the public for free rather than hoarding resources to get more tuition fees, university level education would already have been solved a long time ago!
One thing we can more or less easily do is to search for existing freely licensed videos and add them to the corresponding Wikipedia page where missing. This requires knowing how to search for freely licensed videos:
Why is the spin of the electron half? Updated +Created
More interestingly, how is that implied by the Stern-Gerlach experiment?
physics.stackexchange.com/questions/266359/when-we-say-electron-spin-is-1-2-what-exactly-does-it-mean-1-2-of-what/266371#266371 suggests that half could either mean: