Shel Kaphan Updated 2025-07-16
First Amazon hire, wrote and led the team that wrote v1.
He looks like an older and more experienced dude compared to Bezos at the time.
Bibliography:
. www.geekwire.com/2011/meet-shel-kaphan-amazoncom-employee-1/2/ also mentions that unlike California, there's no sales tax in the state of Washington, which is important for selling books.
Video 1.
Shel Kaphan interview by Internet History Podcast (2015)
Source.
Video 2.
Amazon.com Continues to Grow by NBC 15 (2014)
Source. Features short excerpt of filmed interview with Shel.
Figure 1. . Source. TODO year. Presumably more or less close to publishing date of source at 2020.
This experiment seems to be really hard to do, and so there aren't many super clear demonstration videos with full experimental setup description out there unfortunately.
For single-photon non-double-slit experiments see: single photon production and detection experiments. Those are basically a pre-requisite to this.
photon experiments:
Non-elementary particle:
Video 1.
Single Photon Interference by Veritasium (2013)
Source. Claims to do exactly what we want, but does not describe the setup precisely well enough. Notably, does not justify how he knows that single photons are being produced.
10You literally have written a book.
7 - 9Expert, go-to person on this technology.
5 - 6Solid daily working knowledge. Highly proficient.
3 - 4Comfortable working with this, have to check manual on some things.
1 - 2Have worked with it previously but either not much, or rusty.
I copied this grading scale mechanism from a failed Google interview ;-)
One problem with it is that I am always very hesitant to put a 5 on anything, who can not look at the documentation?
It is also hard to scope things right. Who can claim to be a C++ or Linux kernel expert, even if you wrote a book about it, since those are such humongous topics?
As a result, I haven't updated this in a while, and things may be out of date.
If your project does something that interests me, I can what it takes to contribute. Tell me what I must know, how long I have to learn it, and I'll call you back when I've mastered it.
Smiley's People (TV series) Updated 2025-07-16
This is perhaps slightly worse than the Tinker Tailor Soldier Spy, but still amazing.
Some difficult points:
  • how did the general deduce that the old woman's daughter had a link to Karla? It must be linked to the fact that the Russian agent who made the offer was a Karla-man.
  • some things are hard to understand without having seen the previous Tinker Tailor Soldier Spy, e.g. they say nothing clearly who Toby Esterhase is, he now works on art sales
  • but others are inconsistent, e.g. they changed the actor for Peter Guillam...
Video 1.
Smiley's letter to Karla scene from Smiley's People 1982 BBC miniseries John le Carré adaptation EP6o
. Source. Fan-uplod by Ciro Santilli, one of the greatest television scenes ever. Blocked in the UK.
SmartNIC Updated 2025-07-16
A network interface controller that does more than just the base OSI model protocols, notably in a programmable way.
Video 1.
Hyperscalers Lead The Way To The Future With SmartNICs by The Next Platform (2019)
Source.
Associated article: www.nextplatform.com/2019/10/31/hypercalers-lead-the-way-to-the-future-with-smartnics/ mentions that:
Google is widely believed to be working on its own design.
smashkarts.io Updated 2025-07-16
Quite good, Ciro Santilli played this a lot in 2021/2022, his user ID: ofo5fNy7wRNC1Cw94YVB4KMOW5f2.
The physics not as good as the original Mario Kart 64, and it is notably missing jump gliding, and generally not as sharp! But it is really not bad.
Some of the weapons were too useless that you are just better firing them straight away at wall immediately to get something better, they could have a little better balancing there. I'm talking about you gatling that takes 10 seconds to finish firing, and does not kill enemies immediately. You are better off just firing that gun immediately when you get it to be able to get another gun ASAP. They seem to have done some balancing there however.
It had no chat option, but in a way it was cool to be forced to communicate non-verbally with people whose usernames you got familiar with. Funny you can love people like that, without ever talking to them. The best way of doing so being tea-bagging by going back and forth on a player after winning.
Performance was sometimes a problem. When Ciro tried it again on December 2022, it was unplayable due to the impossibly large lag. Things were much better again in 2023 however it seems.
Solexa Updated 2025-07-16
This is one of the prime examples of Europe's decline.
Instead of trying to dominate the sequencing market and gain trillions of dollars from it, they local British early stage investors were more than happy to get a 20x return on their small initial investments, and sold out to the Americans who will then make the real profit.
And now Solexa doesn't even have its own Wikipedia page, while Illumina is set out to be the next Microsoft. What a disgrace.
Cambridge visitors can still visit the Panton Arms pub, which was the location of the legendary "hey we should talk" founders meeting, chosen due to its proximity to the chemistry department of the University of Cambridge.
In 2021 the founders were awarded the Breakthrough Prize. The third person awarded was Pascal Mayer. He was apparently at Serono Pharmaceutical Research Institute at the time of development. They do have a wiki page unlike Solexa: en.wikipedia.org/wiki/Serono. They paid a 700 million fine in 2005 in the United States, and sold out in 2006 to Merck for 10 billion USD.
Bibliography:
Solutions of the Schrodinger equation Updated 2025-07-16
As always, the best way to get some intuition about an equation is to solve it for some simple cases, so let's give that a try with different fixed potentials.
TODO. Can't find it easily. Anyone?
This is closely linked to the Pauli exclusion principle.
What does a particle even mean, right? Especially in quantum field theory, where two electrons are just vibrations of a single electron field.
Another issue is that if we consider magnetism, things only make sense if we add special relativity, since Maxwell's equations require special relativity, so a non approximate solution for this will necessarily require full quantum electrodynamics.
As mentioned at lecture 1 youtube.com/watch?video=H3AFzbrqH68&t=555, relativistic quantum mechanical theories like the Dirac equation and Klein-Gordon equation make no sense for a "single particle": they must imply that particles can pop in out of existence.
Bibliography:
Once upon a time, when Ciro Santilli had a job, he had a programming problem.
A senior developer came over, and rather than trying to run and modify the code like an idiot, which is what Ciro Santilli usually does (see also experimentalism remarks at Section "Ciro Santilli's bad old event memory"), he just stared at the code for about 10 minutes.
We knew that the problem was likely in a particular function, but it was really hard to see why things were going wrong.
After the 10 minutes of examining every line in minute detail, he said:
I think this function call has such or such weird edge case
and truly, that was the cause.
Spacetime diagram Updated 2025-07-16
Why should I care when I can calculate new x and new time with Lorentz transformation?
Answer: it can give some qualitative intuition on what is larger/smaller happens before/after based only on arguably more intuitive geometric considerations, without requiring you to do any calculations, see e.g. Figure "Spacetime diagram illustrating how faster-than-light travel implies time travel".
Spark-gap transmitter Updated 2025-07-16
The first type of device that allowed sending Morse code without wires, as opposed to the wired electrical telegraph that previously existed.
Naval communications was one of the first major applications, as you can't have wires on boats!
Wireless voice transmission came about with modulation.
Video 1.
Spark-gap transmitter at the at the The Museum of Radio and Technology Jeri Ellsworth (2017)
Source.
Ciro Santilli's preferred visualization of the real projective plane is a small variant of the standard "lines through origin in ".
Take a open half sphere e.g. a sphere but only the points with .
Each point in the half sphere identifies a unique line through the origin.
Then, the only lines missing are the lines in the x-y plane itself.
For those sphere points in the circle on the x-y plane, you should think of them as magic poins that are identified with the corresponding antipodal point, also on the x-y, but on the other side of the origin. So basically you you can teleport from one of those to the other side, and you are still in the same point.
Ciro likes this model because then all the magic is confined just to the part of the model, and everything else looks exactly like the sphere.
It is useful to contrast this with the sphere itself. In the sphere, all points in the circle are the same point. But this is not the case for the projective plane. You cannot instantly go to any other point on the by just moving a little bit, you have to walk around that circle.
Figure 1.
Spherical cap model of the real projective plane
. On the x-y plane, you can magically travel immediately between antipodal points such as A/A', B/B' and C/C'. Or equivalently, those pairs are the same point. Every other point outside the x-y plane is just a regular point like a normal sphere.
Spin number of a field Updated 2025-07-16
Physics from Symmetry by Jakob Schwichtenberg (2015) chapter 3.9 "Elementary particles" has an amazing summary of the preceding chapters the spin value has a relation to the representations of the Lorentz group, which encodes the spacetime symmetry that each particle observes. These symmetries can be characterized by small integer numbers:
As usual, we don't know why there aren't elementary particles with other spins, as we could construct them.

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