What is the most complex topic you understand?

I'm not sure there's anything that I understand, at least not fully. There are things I know a certain amount about, but probably nothing that I understand as fully as I'd like.

Also, understanding can be fleeting if you don't think about a certain topic all the time. Take relativity for example: I recall a very specific moment when I was talking to a friend who is actually formally educated in Physics, and we were talking about the speed of light, time dilation, mass expansion, etc. And I had a definite "aha" moment when I understood why mass has to increase with velocity and why time dilation had to occur. But... could I explain it to somebody else now (that was probably 10 years ago), and convey the same understanding? Do I even understand it as well now as I did in that moment? Arguably not. :-(

OTOH, if you just ask "What's a topic that you know a lot about?" I'd say, generally speaking, "firefighting" and "computer programming, especially in Java". shrug

I guess it might be 'graph hashing', also known as canonicalization.

So this is related to some other things, like the Weisfeiler-Leman Algorithm, and Morgan numbers, and partition refinement. The idea is that to compare two graphs (networks, or Eulerian graphs) for equality one way to do that is to 'hash' the graph. The resulting canonical representations of the graphs are then compared directly for equality.

I implemented a couple of different approaches for doing this - one based on a research paper calling the technique 'signatures', and the other based on an algorithm from a book called 'C.A.G.E.S' (can give references in a bit).

For me, the process of understanding how to achieve this meant learning about permutations, group theory, partition refinement, applying permutations to graphs, and so many other things. I think all told it took me more than a year to properly understand and implement it all!

Very fun, but maybe not the best use of time, looking back...

Germany.

Though I have to admit an ever increasing number of details are getting fuzzy as they fade into the rear-view mirror of my attention.

As a foreigner fluent in German, with a very diverse set of German friends, and years of experience living there, in three very different regions at different stages of my life, I will make the bold claim that I understand Germany, even if I probably understood it more in the past than I will in the future.

I’m sure there are many people who understand it better, deeper, more completely; but I’m not sure any of them are Germans. Ask the fish about water, etc.

I think this kind of sounds like hubris. I plead guilty, but with the mitigating circumstance that my claim to understanding isn’t any more hubristic than the next guy’s.

Austria, on the other hand, is a complete mystery to me.

Rather than "understand" I'll talk about complex "accomplishments".

I once built a computer. I had Alan Clements "Microprocessor Systems Design" for an undergraduate text and built a 68000 based machine with 64M of RAM and ROM. Using discrete ICs on two big Eurorack wirewrap cards was hard work and needed good eyesight and dexterity. Then I wrote a bootloader and kermit-like like RS232 program loader, and finally hashed together a really basic OS from Tannenbaum (with a synchronous scheduler and fixed job table). A long summer of late nights. Can I say "I understand computers". No way! But I feel confident I know more about them than most people I'll ever meet.

Another heroic adventure was "Linux from Scratch", compiling everything along the way with tinycc.

These things are rites of passage. They don't mean I understand those things, and even if I did, that knowledge is obsolete today, but I'm glad I did them.

Healthcare accumulators & benefit plan designs : embedded coverage vs non-embedded coverage, drug tiers, medicare d coverage stages, deductible, out of pocket, formulary, preferred/non-preferred, drug specific caps,

Essentially all those instruments healthcare companies invented to make coverage and payout rules complex.

The Prime minicomputer architecture, from the 80's. Competed with Dec VAX, Data General Eclipse, etc.

The Prime architecture was based on the Multics design from a group of guys hailing from Honeywell and MIT. I worked on Primes for around 12 years, worked for Prime briefly in the 80's, and wrote an emulator that runs many versions of Prime's OS, Primos: https://github.com/prirun/p50em

Prime systems are very much the opposite of RISC, with instructions for:

- process exchange and task scheduling

- procedure call, incl arguments, ring crossing, stack handling, register saves

- decimal arithmetic, incl picture editing for COBOL & PL/I

- string instructions and picture editing

- 6 CPU modes for compatibility with older processors

- DMA, DMC, DMT, DMQ I/O modes for controller access to memory

- 32, 64, and 128-bit floating point

Bash*

I got a book published with a bunch of community and personal findings as an "I wish I had known this earlier" kind of collection.

* Giant disclaimer: Bash is insanely complex, mostly for historical reasons. There are infinite ways of doing basically anything, and all of them have different trade-offs. The big one usually being between the complexity of the code and the kind of situations it can handle.

Nothing. There's nothing that I fully understand because there's always another level deeper you can go.

I understand software engineering and DevSecOps well enough to keep a number of applications in production use, but both subjects are so broad that I think anyone who tells you they fully understand them either doesn't know how much they don't know, or is selling something.

I don't know, because once I understand something it always seems very simple to me.

Cannabis strains and how CBD can work as a governor to suppress the psychological effects of high THC percentages. How the brain receptors react and trigger different states.

The science of recreational drugs are interesting to me.

English local government form, function and finances - or at least I used to, 15 years ago. For my sins, I worked as part of the Lyons Inquiry[1][2] team for 2.5yrs.

... And no. It's not all my fault.

[1] - https://www.gov.uk/government/organisations/lyons-inquiry-in...

[2] - https://en.wikipedia.org/wiki/Lyons_Inquiry

As others have said, I don't think I fully understand a whole lot! But let me think of it this way: Of all the topics that I know stuff about, which one do I think has the biggest delta between what I know and my co-workers in the same space? I'd say cryptography. I'm not an expert by any means, but even among my co-workers, I find myself explaining a lot of basic concepts before even getting into the gritty.

To the extent that I understand anything, which is to say with all humbleness, incompletely, I'd say the most complex things I understand are: 1. human behavior 2. supply chains (arguably a subset of 1.) 3. distributed software systems

It’s a bit hand wavy but conceptually: Hot rock to running application is mentally wild.

I got good at understanding how rocket engines work and the design considerations simply by watching everyday astronaut and Scott manly videos. But now that I understand it, it really doesn’t seem complex.

Methods of self-organizing DHTs to optimize lookup performance. I had to learn hyperbolic geometry and figure out how to compute Delunay/Voronoi graphs on it, at scale, distributedly.

I've repaired multiple HP 5061 Cesium Beam Atomic Clocks. I've got a very good handle on how they work. I'm fairly good at explaining it to people as well.

My girlfriend. Of course it's not a complete understanding, and there's always new things to learn. But that's part of the wonder and enjoyment.

Genome engineering and how our agricultural system actually functions. Next step is to have an in-depth understanding of the entire value chain of agriculture.

How avoid making my wife unhappy (…most of the time)

How CDMA, eHRPD and LTE backend systems design and deployment. My other odd ball skill is knowing old PBX/Key based phone systems.

The electrical properties and strength of covalent molecular bonds during DNA splicing

Also microinstruction vulnerabilities of CPUs.

Semiconductor fabrication process flows. How to start with a bare epitaxial silicon wafer, then process it step by step, until it leaves the fab.

The answer to life, the universe, and everything.

Software programming. Probably not surprising, considering the discussion board I'm posting on.

Nothing.

Some people don't understand things, that is not the same as understanding nothing.

I also understand ashtanga and programming.

FAA Certification

Developer experience and managing complexity

- Regular Expressions

- Unicode and characters encodings

- Native WebGL

- CSS3D

- Women

I lied about women.

EM theory. Ask away...

Jira and its schemes

topic: How we understand things and etc.

Monads.

My wife.

FFT...?

well... programming

data sync

Entropy.

It was hard for me to understand this arbitrary rule of things becoming less ordered over time. Was this just a fundamental natural law?

The answer is no. Entropy is a logical consequence of probability and time.

Why do things become more chaotic over time? Because chaotic configurations have a higher probability of occurring.

There are far more disordered configurations of things then there are ordered, this is why things become more disorder with time. Time changes the configuration. And by probability a high probability configuration is more likely to occur then a low probability configuration. So the axiom of nature here is not entropy, it's probability. Entropy is just a consequence of probability.

There are systems where ordered configurations are more numerous then disordered configuration and in those systems things become more ordered with time. In these cases entropy is STILL defined to be increasing as things get more ordered. Thus entropy is not describing disorder, or is it?

The thing I don't fully understand yet is heat entropy. Apparently when you take heat into account for everything, the disordered intuition suddenly becomes applicable. So if you have a system becoming more ordered with time, heat must be increasing somewhere to offset this increase in order. Maybe someone can explain this part to me?

women