Ciro Santilli @cirosantilli 37

If you shine microwave radiation on a Josephson junction, it produces a fixed average voltage that depends only on the frequency of the microwave. TODO how is that done more precisely? How to you produce and inject microwaves into the thing?

It acts therefore as a perfect frequency to voltage converter.

The Wiki page gives the formula: en.wikipedia.org/wiki/Josephson_effect#The_inverse_AC_Josephson_effect You get several sinusoidal harmonics, so the output is not a perfect sine. But the infinite sum of the harmonics has a fixed average voltage value.

And en.wikipedia.org/wiki/Josephson_voltage_standard#Josephson_effect mentions that the effect is independent of the junction material, physical dimension or temperature.

All of the above, compounded with the fact that we are able to generate microwaves with extremely precise frequency with an atomic clock, makes this phenomenon perfect as a Volt standard, the Josephson voltage standard.

TODO understand how/why it works better.

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In vitro Updated 2025-07-16

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An Introduction to Tensors and Group Theory for Physicists by Nadir Jeevanjee (2011) Updated 2025-07-16

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This does not seem to go deep into the Standard Model as Physics from Symmetry by Jakob Schwichtenberg (2015), appears to focus more on more basic applications.

But because it is more basic, it does explain some things quite well.

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An LC circuit is analogous to a spring-mass system Updated 2025-07-16

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Both are harmonic oscillators.

In the LC circuit:

the current current may be seen as the velocity and containing the kinetic energy
the charge stored in the capacitor as the potential energy

You can kickstart motion in either of those systems in two ways:

charge the capacitor, i.e. pull the string, and then let it go, i.e. close the circuit. This is the simpler one to realise. Shown concretely at: Video "LC circuit dampened oscillations on an oscilloscope by Queuerious Guy (2014)"
give speed to the mass, i.e. make a current pass through the inductor

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Can a smartphone's PIN or password be brute-forced in an offline attack? Updated 2025-07-16

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security.stackexchange.com/questions/202174/can-a-smartphones-pin-or-password-be-brute-forced-in-an-offline-attack

Ciro Santilli has a hard time understanding why this is possible, e.g. many people use short 4 digit pins, or a short swipe pattern. Why can't this be cracked easily offline?

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Inward Bound by Abraham Pais (1988) Updated 2025-07-16

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Free borrow on the Internet Archive: archive.org/details/inwardboundofmat0000pais/page/88/mode/2up

The book unfortunately does not cover the history of quantum mechanics very, the author specifically says that this will not be covered, the focus is more on particles/forces. But there are still some mentions.

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Is fog computing more efficient than cloud computing? Updated 2025-07-16

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Advantages of fog: there is only one, reusing hardware that would be otherwise idle.

Disadvantages:

in cloud, you can put your datacenter on the location with the cheapest possible power. On fog you can't.
on fog there is some waste due to network communication.
you will likely optimize code less well because you might be targeting a wide array of different types of hardware, so more power (and time) wastage. Furthermore, some of the hardware used will not not be optimal for the task, e.g. CPU instead of GPU.