Atomic clock by Ciro Santilli 37 Updated 2025-07-16
Video 1.
How an atomic clock works, and its use in the global positioning system (GPS) by EngineerGuy (2012)
Source. Shows how conceptually an atomic clock is based on a feedback loop of two hyperfine structure states of caesium atoms (non-radioactive caesium-133 as clarified by the Wikipedia page). Like a quartz clock, it also relies on the piezoelectricity of quartz, but unlike the quartz clock, the quartz is not shaped like a tuning fork, and has a much larger resonating frequency of about 7 MHz. The feedback is completed by producing photons that resonate at the right frequency to excite the caesium.
Video 2.
Inside the HP 5061A Cesium Clock by CuriousMarc (2020)
Source.
A similar model was used in the Hafele-Keating experiment to test special relativity on two planes flying in opposite directions. Miniaturization was key.
Contains a disposable tube with 6g of Caesium. You boil it, so when it runs out, you change the tube, 40k USD. Their tube is made by Agilent Technologies, so a replacement since that opened in 1999, and the original machine is from the 60s.
Detection is done with an electron multiplier.
youtu.be/eOti3kKWX-c?t=1166 They compare it with their 100 dollar GPS disciplined oscillator, since GPS satellites have atomic clocks in them.
Video 3.
Quick presentation of the atomic clock at the National Physical Laboratory (2010)
Source. Their super accurate setup first does laser cooling on the caesium atoms.
Sandy Lerner by Ciro Santilli 37 Updated 2025-07-16
This chick is hardcore.
Video 1.
Black-body Radiation Experiment by sciencesolution (2008)
Source. A modern version of the experiment with a PASCO scientific EX-9920 setup.
Allen Wu by Ciro Santilli 37 Updated 2025-07-16
This situation is the most bizarre thing ever. The dude was fired in 2020, but he refused to be fired, and because he has the company seal, they can't fire him. He is still going to the office as of 2022. It makes one wonder what are the true political causes for this situation. A big warning sign to all companies tring to setup joint ventures in China!
Video 1.
ARM Fired ARM China’s CEO But He Won’t Go by Asianometry (2021)
Source.
Stanford University by Ciro Santilli 37 Updated 2025-07-16
The other major university in the Bay Area (and basically in California itself) besides a few University of California places.
The heart of Silicon Valley.
Manhattan Project by Ciro Santilli 37 Updated 2025-07-16
Video 1.
Historic, unique Manhattan Project footage from Los Alamos by Los Alamos National Lab
. Source.
Mostly the daily life part of things, but very good, includes subtitles explaining the people and places shown.
Marked with identifier "LA-UR 11-4449".
Amazon Prime Video by Ciro Santilli 37 Updated 2025-07-16
As of 2021, Ciro Santilli feels strongly that Amazon originals are so much sillier compared to Netflix ones in average.
Of course, everything pales in comparison to The Criterion Collection.
One of the main reasons why physicists are obsessed by this topic is that position and momentum are mapped to the phase space coordinates of Hamiltonian mechanics, which appear in the matrix mechanics formulation of quantum mechanics, which offers insight into the theory, particularly when generalizing to relativistic quantum mechanics.
One way to think is: what is the definition of space space? It is a way to write the wave function such that:And then, what is the definition of momentum space? It is of course a way to write the wave function such that:

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