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Richard Feynman's drug use by

Ciro Santilli 40 Updated 2025-07-16

From Surely You're Joking, Mr. Feynman chapter O Americano, Outra Vez!:

The people from the airlines were somewhat bored with their lives, strangely enough, and at night they would often go to bars to drink. I liked them all, and in order to be sociable, I would go with them to the bar to have a few drinks, several nights a week.
One day, about 3:30 in the afternoon, I was walking along the sidewalk opposite the beach at Copacabana past a bar. I suddenly got this treMENdous, strong feeling: "That's just what I want; that'll fit just right. I'd just love to have a drink right now!"
I started to walk into the bar, and I suddenly thought to myself, "Wait a minute! It's the middle of the afternoon. There's nobody here, There's no social reason to drink. Why do you have such a terribly strong feeling that you have to have a drink?" - and I got scared.
I never drank ever again, since then. I suppose I really wasn't in any danger, because I found it very easy to stop. But that strong feeling that I didn't understand frightened me. You see, I get such fun out of thinking that I don't want to destroy this most pleasant machine that makes life such a big kick. It's the same reason that, later on, I was reluctant to try experiments with LSD in spite of my curiosity about hallucinations.

One notable drug early teens Ciro consumed was Magic: The Gathering, see also: Section "Magic: The Gathering is addictive".

Discrete logarithm of the cyclic group by

Ciro Santilli 40 Updated 2025-07-16

This is the discrete logarithm problem where the group is a cyclic group.

In this case, the problem becomes equivalent to reversing modular exponentiation.

This computational problem forms the basis for Diffie-Hellman key exchange, because modular exponentiation can be efficiently computed, but no known way exists to efficiently compute the reverse function.

Discrete Fourier transform by

Ciro Santilli 40 Updated 2025-07-16

Input: a sequence of

N

complex numbers

x_{k}

Output: another sequence of

N

complex numbers

X_{k}

such that:

x_{n} = \frac{1}{N} \sum_{k = 0}^{N - 1} X_{k} e^{i 2 π \frac{kn}{N}}

(1)

Intuitively, this means that we are braking up the complex signal into

N

sinusoidal frequencies:

$X_{0}$ : is kind of magic and ends up being a constant added to the signal because $e^{i 2 π \frac{kn}{N}} = e^{0} = 1$
$X_{1}$ : sinusoidal that completes one cycle over the signal. The larger the $N$ , the larger the resolution of that sinusoidal. But it completes one cycle regardless.
$X_{2}$ : sinusoidal that completes two cycles over the signal
...
$X_{N - 1}$ : sinusoidal that completes $N - 1$ cycles over the signal

and is the amplitude of each sine.

We use Zero-based numbering in our definitions because it just makes every formula simpler.

Motivation: similar to the Fourier transform:

compression: a sine would use N points in the time domain, but in the frequency domain just one, so we can throw the rest away. A sum of two sines, only two. So if your signal has periodicity, in general you can compress it with the transform
noise removal: many systems add noise only at certain frequencies, which are hopefully different from the main frequencies of the actual signal. By doing the transform, we can remove those frequencies to attain a better signal-to-noise

In particular, the discrete Fourier transform is used in signal processing after a analog-to-digital converter. Digital signal processing historically likely grew more and more over analog processing as digital processors got faster and faster as it gives more flexibility in algorithm design.

Sample software implementations:

numpy.fft, notably see the example: numpy/fft.py

Figure 1.
DFT of $2 sin (t) + cos (4 t)$ with 25 points
. This is a simple example of a discrete Fourier transform for a real input signal. It illustrates how the DFT takes N complex numbers as input, and produces N complex numbers as output. It also illustrates how the discrete Fourier transform of a real signal is symmetric around the center point.

Hewlett-Packard by

Ciro Santilli 40 Updated 2025-07-16

They do seem to have been very innovative, and have had a very good work culture. They also had a huge impact on the Silicon Valley startup scene.

Some products they are known for:

oscilloscopes
Atomic clocks, notably highly portable ones, see e.g. Video "Inside the HP 5061A Cesium Clock by CuriousMarc (2020)"
pocket calculator

Video 1.

The decline of HP by Company Man (2022)

Source.

Video 2.

HP Origins promotional documentary by HP (2006)

Source. A bit too star eyed, but gives some good ideas.

Chinese currency by

Ciro Santilli 40 Updated 2025-07-16

Population inversion by

Ciro Santilli 40 Updated 2025-07-16

Pentane interference by

Pentane interference typically refers to the impact that pentane, a straight-chain hydrocarbon with five carbon atoms, can have on various chemical analyses, particularly in chromatographic methods. In the context of gas chromatography or mass spectrometry, pentane can co-elute with other compounds, potentially leading to inaccurate results or difficulties in identifying and quantifying other analytes.

Suspension (film) by

"Suspension" is a film that was released in 2015. It is a psychological horror film directed by Dave R. Sheppard, featuring a storyline that revolves around a group of friends who find themselves trapped in a series of bizarre and suspenseful situations. The narrative often intertwines elements of fear and the supernatural, typical of the horror genre. The film delves into themes of isolation and psychological strain, often keeping viewers on edge through its suspenseful atmosphere and twists in the storyline.

Suvini Zerboni by

As of my last update in October 2023, there is no widely recognized entity or subject known as "Suvini Zerboni." It’s possible that it could refer to a person, a brand, or a concept that emerged after that date, or it might be a relatively niche or obscure reference.

Per Carlqvist by

Per Carlqvist is a name that could refer to different individuals or contexts, but it's not widely recognized in popular culture, politics, or science as of my last knowledge update in October 2023.

Swedish nuclear physicists by

"Swedish nuclear physicists" refers to scientists from Sweden who specialize in the field of nuclear physics, which is the study of atomic nuclei, their constituents, and interactions. This field encompasses a variety of topics, including nuclear decay, nuclear reactions, and the properties of nuclear matter. Sweden has contributed significantly to nuclear physics research and development, particularly through institutions like the Uppsala University, Lund University, and the Swedish National Space Agency.

Symposium on Theoretical Aspects of Computer Science by

The Symposium on Theoretical Aspects of Computer Science (STACS) is a renowned academic conference that focuses on theoretical computer science. It serves as a venue for researchers to present their work, exchange ideas, and discuss various aspects of theoretical foundations related to computer science. The topics covered in STACS typically include areas such as algorithms, complexity theory, automata theory, formal languages, logic in computer science, and computational models.

Syntacticians by

"Syntacticians" refers to linguists or researchers who specialize in syntax, which is the study of the structure and rules governing the arrangement of words and phrases to create well-formed sentences in a language. Syntacticians analyze how different components of sentences interact with each other, including word order, grammatical relationships, and hierarchical structures. They may also explore how syntax interacts with other linguistic domains such as semantics (meaning) and morphology (structure of words).

Syntagmatic analysis by

Syntagmatic analysis is a concept derived from linguistics and semiotics, primarily associated with the structuralist approach to language and meaning. It refers to the relationships and associations that words or signs have with one another within a sequential context—essentially, how elements operate in conjunction with one another in a sequence (or "syntagm"). In syntagmatic analysis, the focus is on the horizontal relationships of elements that are combined to create meaning.

Percy Williams Bridgman by

Percy Williams Bridgman (1882-1961) was an influential American physicist known for his work in the field of high-pressure physics. He is best remembered for his research on the properties of materials at high pressures, particularly with regard to phase transitions and the behavior of solids.

Tacheometry by

Tacheometry is a surveying method used to determine the distances and elevations of points on the ground without the need for a direct measurement of distance. It is a technique that combines the principles of trigonometry with the use of instruments like theodolites or total stations. In tacheometry, the surveyor typically measures angles and, using a fitted scale or an equation, can obtain horizontal distances based on the angles measured and the height of the instrument above the ground (the instrument's height).