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Ask HN: What is the most complex concept you understand?

• xtiansimon 6y ago
  There was a MOOC from TU Delft called Solving Complex Problems. The course professor made a distinction with the term ‘complex’ as different from complicated. The complex problems in the course involved people and opinions and personal/self interest in public policy. I recall hearing in another context the distinction between a complicated Swiss watch versus a cockroach, which would be described as complex. Through that lens your question is undermined. But I take your point. I would say there are a lot of complex ideas I understand from philosophy; however, the very language you use contains critical distinctions. The terms and their construction are not plastic, or forgiving, so an extemporaneous explanation for a lay audience frequently fails. A complicated idea which I understand with a more stable basis is accounting’s debit-credit model. Then again, teaching this versus explaining it to someone is different depending on your num3rical literacy. How much time do you have? https://news.ycombinator.com/item?id=26042885 https://news.ycombinator.com/item?id=26042885
• mettamage 6y ago
  Rowhammer via JS
• xem 6y ago
  I have a few: JavaScript code-golfing; CSS3D art; WebGL (traditional and as in shadertoy); Unicode; 6502 / NES emulation
• david927 6y ago
  I think it's a bit like the coastline paradox: https://en.wikipedia.org/wiki/Coastline_paradox https://en.wikipedia.org/wiki/Coastline_paradox Most maps fairly accurately measure the coastline of a place. Their granularity of topographical measurement is good enough. In other words, it's not if you understand a concept but how deeply. Also, it's hard to sit down and list all the complexities of concepts. You could be understanding a lot more complexity than you realize.
  • yesenadam 6y ago
    Yeah...What one person considers deep understanding about something, might seem to another the most basic, superficial knowledge. It's all relative. It's like: Beauty is as relative as light and dark. Thus, there exists no beautiful woman, none at all, because you are never certain that a still far more beautiful woman will not appear and completely shame the supposed beauty of the first. - Paul Klee, diary, 1910 (And yet, there is light, dark, and beautiful women..)
  • jmkerr 6y ago
    Sorry couldn't resist, from wikipedia: > if one were to measure a coastline with infinite or near-infinite resolution, the length of the infinitely short kinks in the coastline would add up to infinity. No they wouldn't. The sum would converge. What a bad article.
    • pengstrom 6y ago
      Not necessarily if the coast is fractal, no?
    • jjgreen 6y ago
      Well the argument does break down as you get to the atomic level, but the observation is morally correct; the idea (and the divergent sum) is easiest to see with the Koch snowflake (which has an infinite perimeter) https://en.wikipedia.org/wiki/Koch_snowflake https://en.wikipedia.org/wiki/Koch_snowflake
      • jmkerr 6y ago
        There is some self-similarity going on (Mandelbrot discusses scales from 1000 km to 10 km) but rocks or coastal sections with the fractal dimension of Great Britain on a scale of 1m or 10m are a rare exception. I'm not an expert, but I think it's because as the length scale gets smaller, coastal erosion dominates the coastline, as opposed to an older force producing larger features, like glacial erosion or even plate tectonics. No reason to drag quantum mechanics into this discussion, but the circumference of an atom can be defined, so that's not a problem. An actual Koch snowflake you can buy will always have a measurable circumference. E: Some of this misunderstanding is actually due to Mandelbrot himself, he wrote in the introduction to [How long is the Coast of Britain?, 1967]: > Geographical curves are so involved in their detail that their lengths are often infinite or, rather, undefinable. No, they're not any more infinite than a toothbrush.
• injb 6y ago
  Being able to explain it in 5 minutes doesn't necessarily mean it's not complex. It really depends on how elementary the explanation is. In other words, how complex are the terms themselves in which you explained it? For instance, you might say that the Fourier Transform is just a decomposition of a function of time into complex exponentials representing frequencies. But how does a complex exponential represent frequencies? Can you explain Euler's formula? I usually pick someone I know well and consider what it would take to make them understand, given what I expect them to know already. I find this really helpful in testing my own understanding, but it's a good way of testing how complex an idea really is, relative to the average person's knowledge. (Incidentally I'd rank Fourier stuffs as pretty complicated, all things considered).
  • 0xcafecafe 6y ago
    >Being able to explain it in 5 minutes doesn't necessarily mean it's not complex. I second this. Evolutionary biology is a complex topic. But all it took for me to understand the basics of it was the Carl Sagan video about the japanese crabs.
  • goalieca 6y ago
    Building on the giants.. Fourier could more easily be explained once you understand linear transformation as a multiplication with basis vectors. Seems simple enough right? But that is assuming you the prerequisites.
  • mikewarot 6y ago
    I can explain how atomic clocks work, to a layman, in 5 minutes. It's a matter of understanding the subject, and remembering what it is like NOT to understand it, and connecting the two in creative ways.
• mattivc 6y ago
  Probably Lie Theory, or at least the small subset of it that is relevant for robotics. It has taken me a long time and a lot of work to understand it to the level I have, and I still have a lot more to learn. But it is a fascinating subject and a very elegant way to represent some very complex optimization problems.
  • ggeorgovassilis 6y ago
    Thanks. I didn't know about Lie Theory. https://en.wikipedia.org/wiki/Lie_theory https://en.wikipedia.org/wiki/Lie_theory
  • jpcooper 6y ago
    How is Lie theory relevant to robotics and optimisation? I looked into Weyl groups a bit during my undergrad, but didn't really go into Lie theory in much depth.
    • mattivc 6y ago
      Lie theory is, among other things, a very elegant way to parameterize an energy function involving rotations in 3D space. For example the translation and rotation of multiple camera frames that observe the same set of 3D points. This is the basis of how Visual Odometry, SLAM or 3D reconstruction problems are solved. There are other cool things like representing a probability distribution over a 3D rotation with an multivariate gaussian vector interpreted as a so3 or se3 vector. Using this you can for implement a very elegant extended kalman filter estimating a 3D rotation. Which usually can be a tricky thing to do. In robotics we pretty much only use the SO3, SE3 and SIM3 groups so my knowledge is limited to those groups.
      • jpcooper 6y ago
        Thanks for the explanation.
      • domnomnom 6y ago
        What about quaternions?
• verdverm 6y ago
  That every time I "understand" something there is 10X more that I have yet to understand.
• JasonFruit 6y ago
  Every topic is infinitely complex if you go into enough details. It's like the epistemological version of I, Pencil: there's far more to knowing a simple topic than we initially consider.
  • smt88 6y ago
    This person is asking, "What is your deepest topic?" They're not asking, "How deep does [topic] go?" Yes, every topic goes infinitely deep, but I personally have much deeper knowledge about the HTTP client implementations than I do about elephant reproduction.
    • JasonFruit 6y ago
      That is a possible interpretation that I did not immediately see.
  • rriepe 6y ago
    Academics: Knowing more and more about less and less until you know everything about nothing.
• x0hm 6y ago
  Object oriented programming. tl;dr - literally all of you are doing it wrong.
  • mbrodersen 6y ago
    There is no agreed definition of OO so what you are claiming is obviously wrong. But who cares? What we are doing with programming is solving problems. I don’t care if you are doing it “right” or not according to some arbitrary definition. But, having said all that, IMHO Erlang programmers are doing OO better than anybody else. And I am not an Erlang programmer.
  • the_only_law 6y ago
    I’m not sure I could explain it well myself, but many years ago, back when I was still rather new to programming I just never understood it until one day I was working on something and it clicked.
  • deleted 6y ago
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  • letientai299 6y ago
    Could you explain more on why we’re doing it wrong?
  • drcode 6y ago
    I think the question in 2021 is more "why would anyone use OOP at all, compared to other techniques, outside of a few niche use cases?" (though I agree OOP can be very useful in niche use cases where having lots of scattered state makes sense, such as when writing a UI component library)
    • x0hm 6y ago
      You can achieve immutability with OOP. Other paradigms just emphasize it more. I agree, though, that mutability is detrimental, and that traditional OOP can easily lead us to believe that state is not a concern. I do not believe that this is a problem inherent to OOP, rather it's a problem of paradigmatic implementation.
• idlewords 6y ago
  Understanding would be an overstatement, but there's a mental model in my head about the interaction between personal liberty, privacy, automation, encryption, state power, human psychology, and the feedback loops that connect them that I sometimes get larger glimpses of. Then again, that feeling of occasional clarity is probably how a crank feels. But in terms of stuff I struggle to get my mind around, that is the most complicated thing by far I have ever tried to understand. That and the grammar of numbers in Slavic languages.
  • ggeorgovassilis 6y ago
    > that feeling of occasional clarity is probably how a crank feels I felt like that when I learned about magamps last year... they were hiding in plain sight for my entire life https://en.wikipedia.org/wiki/Magnetic_amplifier https://en.wikipedia.org/wiki/Magnetic_amplifier
    • evilspacemonkey 6y ago
      Dude, I am probably as hardcore as electrical engineers come (define your metric, I will (probably) beat it :-) )... I learnt about magamps from your post today. Thanks
    • mikewarot 6y ago
      I repaired a lot of Westinghouse Industrial Control Modules that were built in 1964 with early transistor technology as a rule, The most interesting was a magnetic amplifier module, it had 4 windings as inputs, each thus DC isolated from all of the others, AND it worked all the way down to DC... which I didn't expect. The drive frequency was about 10 Khz. --- In the 1950s, transistors weren't yet reliable enough for computing, so they invented a solid state computer in the 1950s that ran at 1Mhz, had few transistors, and a few big tubes driving the clocking, it used magnetic amplifiers for logic gates. https://en.wikipedia.org/wiki/UNIVAC_Solid_State https://en.wikipedia.org/wiki/UNIVAC_Solid_State
      • ggeorgovassilis 6y ago
• madsbuch 6y ago
  In my masters thesis I used following quote: > On mathematical perception: “either you have no inkling of an idea or, once you have understood it, this very idea appears so embarrassingly obvious that you feel reluctant to say it aloud; moreover, once your mind switches from the state of darkness to the light, all memory of the dark state is erased and it becomes impossible to conceive the existence of another mind for which the idea appears nonobvious.”
  • tmaly 6y ago
    The Curse of Knowledge is shorthand way of putting this.
  • tunesmith 6y ago
    There are some concepts I have the opposite experience of: I find it fascinating, I start pulling threads, I come to all sorts of wildly interesting insights, I construct it together into something I can easily talk about and explain, I explain it to others, and they nod and respond "of course" as if it were already obvious to them. Sort of feels like Principia Mathematica and 2+2 (although that's a very extreme case).
  • deleted 6y ago
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  • etiam 6y ago
    Seems like an important phenomenon to note. Maybe somewhat tempered by the one described in: Weierstrass' “When I wrote this, only God and I understood what I was doing. Now, God only knows.”
    • high_byte 6y ago
      this applies to half of my notes from 6+ months ago. why am I so cryptic with note taking?
      • voiper1 6y ago
        When I take notes and program, I try to remember that I'll look back at this and know nothing. Will I be able to rederive the entire context in my mind at this moment? I don't know if this is perfect, but I've caught myself many times adding more context.
• czbond 6y ago
  I understand everything in the world to the deepest depth. Let me explain, because this is a bit of sarcasm. I realized after years of being a specialist, that deep knowledge can be hired for at a price much less than the cost of achieving it in most cases. Thus, in most cases, specialized knowledge isn't needed - but in the case it is, find and talk to the person who can get you most of the way there. However, in the spirit of the question, some CS related algo's or quantum mechanics (due to PBS Spacetime). I've learned to be a flexible generalist.
  • iujjkfjdkkdkf 6y ago
    I have rarely if ever seen examples of specialized knowledge being outsourced. If someone (who understood the details) has already build a "product" out of that knowledge that lets you understand what it does for you without knowing how it works, you can use the product. But if you want to make a new product (in the sense I mean here), you actually have to understand. This is a pretty classic mistake I see being made, where managers assume they can outsource understanding something, and are left with an end result that is dummed down to meet their misunderstanding.
• deleted 6y ago
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• Nostradedamus 6y ago
  I solve Time ... https://www.youtube.com/watch?v=URZHbauY1yw https://www.youtube.com/watch?v=URZHbauY1yw
• DoreenMichele 6y ago
  My medical condition and how to live with it.
• jbjbjbjb 6y ago
  You’re asking about knowing every detail of a concept, I don’t know much philosophy of concepts but that sounds like an oxymoron.
• jimpudar 6y ago
  I bet the von Neumann architecture is up there for many of us here, although it seems so simple once you have grasped it.
• deleted 6y ago
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• bemmu 6y ago
  When I started learning C as a teen, I somehow got really stuck trying to understand pointers. That's one of the few things I now I feel I understand, but I can also still to a degree recall how it felt not to understand it.
  • orwin 6y ago
    Funny, i had a really hard time understanding something even more basic: functions. I mean, i understood i could call them with arguments and they would do what i wanted them to do, but i didn't _understood_ them. When my main was "too big", i created another function to trim it. I did not get recursive backtracking until i really had to, and then everything lit up for me. I then became a big fan of functionnal programming after that revelation.
    • Gibbon1 6y ago
      What found interesting is I learned assembly first. Understanding C pointers and function was pretty easy from there. But C's notation for dealing pointers is non-obvious. Random old school thought. BASIC has an unappreciated feature in that every line of code stands mostly on its own. It's either valid or it's not. In the case of C/C++ that isn't true. A line of codes validity depends on the lines before it.
• mrwnmonm 6y ago
  Reason is something God creates. You eat because if you didn't you will die. The designer created that reason through the design. So it is not logical to ask about the reason that made God create the world. So the meaning of life depends on why God takes actions, and we will never understand that. I don't think it is very complex concept. - I believe in a designer obviously. I totally understand if you didn't.
  • mrwnmonm 6y ago
    Downvotes? LOL!
  • angelbar 6y ago
    Its ok... move on
  • jbay808 6y ago
    It's funny you put it this way. I have the same philosophy and am agnostic. Here's how I'd express it. Causality is a concept that exists within a universe, because it's bound to time, which also a concept that exists within a universe. The physical law of causality (which can be expressed as both "events of the present are fully defined by system states at previous times" and the time-reversed equivalent, that the past states are fully defined by the future) are only coherent concepts within the framework of specific physical laws that govern this universe. Not every set of possible physical laws gives rise to causality, or even time. In Conway's Game of Life, the future state of the board is also fully determined by the past, although there is no time reversal symmetry. Judea Pearl's causality is similarly bound to applying within the context of a timeline and universal law. Again in Conway's Game of Life, you can implement Turing machines and run simulations of any scenario. Hypothetically you could have artificial life in such a simulation, which might conduct experiments to learn the physical laws of the cellular automaton that governs their world. But those laws, their perception of cause and effect, only exist within the context of that simulation, and within their simulated timeline. Their "time" is a state variable of the simulation. No experiment conducted by creatures within the Game of Life could determine why their simulation is running in the first place, or why its initial conditions were chosen the way they were. The computer running their simulation is outside the laws of their universe. To ask "what was the value of Conway.simTimeIndex before the Game was started?" doesn't make sense. The laws that govern the commencement of Games cannot be perceived from inside the Game. On our own level, the notion of cause and effect is a concept that is coherent within our universe and its concept of time. To ask whether our universe had a cause, or was preceded by something, doesn't make sense. It might or it might not have; that depends on the laws that govern the commencement of Universes, which we cannot measure from observations inside of our universe. If there is any law of meta-causality or time, on the level of reality at which universes are created, we will not identify it via measurements conducted within this universe.
• louiechristie 6y ago
  Centering things in CSS
  • ggeorgovassilis 6y ago
    :)
  • starpilot 6y ago
    Not possible.
  • mustardo 6y ago
    Better yet how about vertical alignment?
• highspeedbus 6y ago
  Maybe not the most complex, but the most useful for me are the concepts of Envelope (like flight envelope) and range of operation. You start to understand how hard reality is and how engineered systems are all bound to it. You can't have, for example, a mic capable of recording both a whisper and a rocket launch. You need to optimize for some function.
  • ggeorgovassilis 6y ago
    I think the nature of trade-offs is interesting. I had a glimpse of understanding of the Heisenberg uncertainty principle when analysing a "beep" sound with Audacity. When switching to spectral view, I was expecting a single, clear frequency, but it was a band. The Fourier analysis settings include a "window size": the larger the window, the more precise the frequency becomes, but that temporal bounds (start and stop) become blurred.
  • thewarrior 6y ago
    Why not have two mikes that can record either and switch intelligently?
• kleer001 6y ago
  How are you measuring complexity? Number of nested connections? That would probably be life its self. So, understanding it from its various mathematical basis through physics and chemistry on up to genetics, game theory, and evolution. Connections to seemingly unrelated topics? Like human politics? That involves brain chemistry, psychology, history, philosophy, (again) game theory, and ethics. Complexity resulting in application of said concept? That's just fractals. Nothing more complex. Then again, depending on your bent you might consider cosmology the ultimate complexity as it literally involves everything. IMHO it's possible that your friend truly does understand women. It's a testable claim. Make him put his money where his mouth is. Writing good fiction is seemingly orthogonal to your intention, but I'd put it up there on the list of complex concepts one could know. Additionally making a movie, the most complex human artistic work, is pretty complex. Personally I couldn't say I understand any of these as an expert would. But I dabble.
  • ggeorgovassilis 6y ago
    > How are you measuring complexity? I think measurements are useful when comparing things in an absolute space (eg. rate all cars by engine power). But complexity is relative; something complex to me is simple to you. A topic might be simple to me because I axiomatically accept a premise which you consider a topic of analysis.
    • kleer001 6y ago
      Hmm, I think that's comparing the complexity of our understanding of the topic and not the complexity of the topic its self which I think is regularly laid out by experts and researchers of said topic. So, you might have a savant belting out absurdly complex fugues on a piano with little to no effort, while a young music student spends two hundred hours understanding the content of that music. The music itself, however, has the same complexity regardless of who's appreciating it. No?
      • ggeorgovassilis 6y ago
        Maybe there is an objective, absolute complexity, but I can't find good examples. Building on your example (music), a chord seems complex when you think of it as a sequence of individual notes, but is simple if you think of it as an object in a multi-dimensional space (of which a single note is a trivial instance). The complexity arises from how one looks at the thing and what the conceptual tools available for understanding are.
• Barrin92 6y ago
  Depends on what you mean by complex. In a technical sense probably some of the stuff I did in uni. I worked on something called Legendrian Submanifolds which is a topic within contact geometry, so that's probably the most arcane academic thing I know anything about. In a practical sense managing an organisation with a sizable amount of people in it due to the sheer amount of diverse issues you have to deal with, and the way in which you can't really reduce it to any kind of formula and where you find new problems every day. Everything that involves organising people is very complex. I was originally thinking about writing "organising WoW classic raids" as a joke but it might actually be true as well.
• TuringNYC 6y ago
  Human nature. Vastly more complex.
• ergonaught 6y ago
  Reading comprehension.
• sgt101 6y ago
  When I understand things they seem simpler. To try though : recursion, induction & generalization, entailment, parse trees. One thing I don't understand is relativity, but someone once told me that you could summarize it by saying "force acts at a distance over time".
• 317070 6y ago
  How to do numerical backpropagation (differentiation) on the result of an integration of a stochastic differential equation. And I am sure I only have scratched the surface of this niche already. Numerical algorithms can be both amazingly intricate and omnipresent at the same time. Optimization is a beautiful field because of it.
• rsync 6y ago
  I think I understand interest rate swaps and, by extension, credit default swaps and could, if pressed, explain them in a concise and approachable manner. I'm not sure how complex that really is but it seemed difficult to wrap it all up in my mind at the time. More interesting: A complex concept that I don't understand is the relationship between water pressure and water flow rates and how they affect one another. I've had people explain it to me and I'm not even sure they understand it.
  • eutropia 6y ago
    I started trying to explain water flow / pressure by doing dimensional analysis (comparing the units) and I just confused myself. Count me among those that don't understand.
  • kroeckx 6y ago
    I find it easiest to explain it in terms of electricity, which I assume most people here are familiar with. It acts just the same. Pressure, like voltage, is a difference. The flow rate is like the current, how much goes though. A pipe has a resistance that depends on it's diameter and length. You can calculate the resistance of the pipe as the pressure difference over the pipe divided by the flow rate. One thing people might get confused by is why making the opening at the end of the pipe smaller makes the water go faster. What you do in electricity terms is add a series resistor, the total flow rate in the pipe will be lower, but the speed can be higher because it needs to go through smaller opening and so is more concentrated.
• v64 6y ago
  American tax code. I have become the de facto tax explainer in my circle, being able to provide explanations for taxes that apparently many of my friends' accountants are unable to elucidate for them. I'm not sure exactly why it clicks for me so well, but I've found that even among those used to working with equally arcane processes/codebases, taxes still evade their comprehension.
• arethuza 6y ago
  It depends what you mean by "understand" I've implemented a purely functional programming language that macro expanded in lambda calculus and was transformed into various set of combinators for evaluation. So I know you can express the Y-combinator in terms of S and K to implement recursion and I've literally watched the resulting expressions resolve but do I really do not understand conceptually how you can implement recursion in terms of two ridiculously simple functions.
• Shish2k 6y ago
  It’s difficult to judge because everything feels simple in retrospect - but going by “number of times I attempted to learn something and gave up” - I made around 6 attempts over 2 years to learn Blender (in the v2.5 era), and each time failed to get as far as making a nice-looking cube. Then something clicked, and suddenly every aspect of the interface makes perfect sense and I’ve never been so productive with an art tool :)
  • angelbar 6y ago
    I aspire to get someday there
• deleted 6y ago
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• nimih 6y ago
  I can bake a pretty good apple pie from scratch, OP. Took me more years to master that than learning how to calculate cohomologies or administrate a kubernetes cluster did.
  • zwieback 6y ago
    That's a good one. When I moved from Germany to the US in '92 I looked down on pies - nothing like a good German Apfelkuchen. Fast forward 20+ years and I'm slightly obsessed with making a good apple pie. Lots of variables and due to fluctuations in the exact makeup of the ingredients it's a new challenge every single time. I came here to say I recently took the time to really understand the Lucas Kanade algorithm in depth but I'm going to join the apple pie bandwagon instead.
    • sammyo 6y ago
      Actually the simple rule is choose apples so sour and hard they can barely be eaten raw, smaller the better. Oh and De Morgan's theorem.
• angelbar 6y ago
  I got nauseous when I try to comprehend the real cosmos size.
• aynyc 6y ago
  Ski carving. I tho I was doing it right for 10 years, I finally understand it this season.
• nonameiguess 6y ago
  I don't think I can say I actually understand it, but the most complex thing I have ever tried to understand is basic molecular biology. The simple processes by which the instructions to produce a protein from constituent molecules is encoded, transcribed, and reproduced, via other proteins that induce signal cascades and fit with each other to close and open channels that propagate the signal. I say "simple" but it's amazingly complex and a miracle that such a thing is possible and actually happened. Somehow, the electromagnetic properties of specific configurations of protons and electrons can create exactly the right shape of field as to make it possible for them to chain together in a way that encodes the ability to produce exact copies of the same configuration from available inputs and free energy, and that just happened, with no supervision or intent or purpose, and from that, a part of the universe now exists with thoughts and values and teleology and collectively attempts to bend the rest of the universe to its purpose. How? Why? There is no answer and I will soon no longer exist to ask the question, and soon after that nothing will exist that can ask questions, but the fact that, for some brief period, part of the universe became self-aware, information that will eventually be lost forever, is a miracle. And I got to be a part of it. And I got to spend a few years trying and failing to grok how basic principles of physics and chemistry can make this possible.
• Poiesis 6y ago
  I'm pretty sure that I don't completely understand anything.
• tenebrisalietum 6y ago
  How the Atari 2600 display hardware works.
  • karmakaze 6y ago
    Oh yeah! I learned everything there was to learn about my Atari 8-bit computer. Of course, programming it and others is something I'm still learning.
    • tenebrisalietum 6y ago
      :) The 2600 is a bit different than the 8-bit computer lines (400, 800, etc.). On the computers you have an ANTIC chip that drives the CTIA/GTIA using instructions in display lists. On the 2600 the CPU has to program the TIA directly and basically in realtime.
      • karmakaze 6y ago
        Yes, the 2600 doesn't have enough memory for anything else. Did some scanline timed programming on the 400 as well. In one job had a similar case of less memory than output area with a laser printer engine. It had a short memory buffer where the laser would wrap around many times while printing a page. The trick was to split up all the input commands into output object slices that were short enough to fit into a band of the buffer, order them, and paint them just-in-time, wrapping around the bottom of the short buffer to the top. The lower-end HP LaserJets had a similar implementation that would get the dreaded 'print overrun' error.
• thelastinuit 6y ago
  word, a complicate airflow. Fascinating concept and complex to my stupid and simple mind.
• mam2 6y ago
  "model sufficiency" a lot of actual researchers spend entire lifetimes to model complex stuff at the lower level possible when a good model tuned on real data will generally give better predictions. relevant quote : "all models are wrong, some are useful"
• ryandvm 6y ago
  I have a pretty in-depth understanding of the NEXRAD WSR-88D weather radar data formats. It's not that it's rocket science, but it's just an insane volume of incredibly arcane data and math. I've learned all of it for a hobby project of mine and I still have a lot more to learn, but I find studying and deciphering it to be strangely relaxing. It's weird.
• airhead969 6y ago
  All acquired concepts are built on simpler, innate ones or we could never learn anything. (50k innate concepts) There uncountably infinite potential concepts in abstract subjects because an additional layer, reduction, parameterization, or generalization can be made. Some answers might include, but aren't impressive: - General relativity. - Quantum computation. - Derivation of time-dependent Schrödinger equations. - Tensor calculus. - Dependent typing. - Monads. - Ambiguity. (in general) - Women. (literal) A general genius would be able to list things almost no one has ever heard of and fewer could understand without additional time and explanation.
• bmn__ 6y ago
  > I tried to explain them and failed You can perhaps get better results by mimicking https://www.wired.com/video/series/5-levels https://www.wired.com/video/series/5-levels – explain the concept at different levels of expertise. You might change your mind about that a concept you think you could not explain.
• mikewarot 6y ago
  I have a mental map of how the universe works, so the whole map for me is the simplest and most complicated thing I understand, all at the same time. I have repaired HP 6051b Cesium beam frequency standards, and can explain how they work, to laymen. I don't believe there is anything I can't understand. I believe there are two ways of thinking, mapping, and packing... I believe that mappers can learn ANYTHING, if they are sufficiently motivated and resourced. Computers on the other hand, are the ultimate packers... as long as you can give them a sufficiently constraining set of instructions that accounts for most small deviations, they can do almost anything.
• abss 6y ago
  Zero Knowledge Proofs
• midrus 6y ago
  I'm pretty stupid so I think that the most complex thing I understand is that spacetime is something with a "shape" and that it deforms in presence of matter. It blows my mind thinking about it.
• david38 6y ago
  When I was at the top of my game, I knew third semester discrete math proofs like the back of my hand. Not memorized, but really grokked the math behind the proofs. I noticed after I graduated there was a period of time when I would have to concentrate for ten minutes and the epiphany would return. Now, several years later, I’ve entirely lost it.
• Balgair 6y ago
  Light. Optics specifically. Well, maybe I understand it. I'm pretty good with photons in the near-visible range. Muller matrices, point spread functions, the wave-particle duality, fluorescence, what have you. Though gamma rays and AM radio still confuse me. Ok, I guess I'm still learning then...
• mlady 6y ago
  Grappling. Brazilian Jiu-Jitsu specifically. I'm a purple belt (middle belt, halfway to black belt) and I understand things about manipulating how another human body moves that would either make my white belt mind of 8.5 years ago explode or it would be incomprehensible. It usually takes around 10 years for a person to go from white belt to black belt if they train consistently. There are exceptions, of course, but I usually liken the thought and mat time spent, knowledge acquired, and skills sharpened to obtaining a PhD.
• simonblack 6y ago
  The big problem with that question is that when you understand something, it becomes simple(r) in your mind, and no longer complex. But objectively, that might be something that thousands of other people class as complex, very complex or even extremely complex..
• dave_sid 6y ago
  Why my image is flipped horizontally when looking in the mirror but not vertically.
  • karmakaze 6y ago
    I'm trying to explain this to myself and can only come up with either horizontally or vertically depending on how you think about it. e.g. if there's a mirror standing on the floor and I'm lying horizontally on the floor looking into the mirror, I can say my image is flipped left-right from my vantage point or vertically wrt. normal standing. But also that my sideways image is flipped head-to-toe, as in bilaterally in normal standing position.
  • babygoat 6y ago
    Wow that’s a mindfuck. I understand it in an optical sense but not intuitively. Do you have a good explanation for this?
    • dave_sid 6y ago
      No. It’s a fucking nightmare. The only clue I can give myself is that if I were to stand on a mirrored floor and look down, then actually I would then be flipped vertically, but not horizontally. Although that just makes me more confused really.
• dave_sid 6y ago
  Understanding that time is change, and that’s all it really is. Simple now I think about it.
• karmakaze 6y ago
  I tend to get to a semi-deep, practical working knowledge of an area and stop there. I tend to know more about relational databases than my peers, nice ones like PostgreSQL and others like MySQL 5.7. I'm really good at devouring a new subject area to find the boundaries of what there is to know, even as I don't understand it. Sometimes, terms or phrases will stick in my mind and at a later opportune moment become clear that it's what I need to use. Programming languages and ORMs are curious in how we seem to keep on using not such good ones. I like to draw analogies from disparate subjects and apply some aspect of it to solve a problem. I often wondered if anyone is ever purely creative, and thought hard about a time when I had a truly original thought. I finally remembered that time in grade 7 math when I thought that Pi was dumb and that 2 Pi was more fundamental. My reasoning was (1) radius is more fundamental than diameter, (2) arc length of a circle. This was of course back in the late 70s before I'd ever heard of Tau. I'm an expert in the Blub language and looking both ways from that vantage point.
• lamontcg 6y ago
  I've been teaching myself optimal control theory and rocket trajectory optimization using pontryagin's minimum principle. There's still a some quite large "...and then a miracle occurs..." gaps in my understanding, but it is coming along. Also done some work on a pseudospectral optimization engine (baby version of GPOPS) and gotten some results out of that. And I have a very small understanding of convex optimization and can at least describe one simple concrete problem that I've solved (or improved) using convex techniques. I can at least read lars blackmore's hoverslam papers and see how they could be implemented. I took a quarter of graduate level quantum in school and optimization problems involve much more voodoo.
• _nalply 6y ago
  This question is difficult to answer because it's likely that the most compex concept you think you understand you don't really. I thought about this question and thought, Rust lifetimes or Rust coherence rules, but then again I thought maybe I don't really understand them. Perhaps it is more helpful to ask: what is the most complex concept you can explain the basics?
• RichardCA 6y ago
  I remember watching this in the 80's and it felt like cheating. In exchange for 25 minutes of your time you get the gist of Special Relativity. But the idea of γ (gamma) is dirt simple, it's just simple Algebra. https://www.youtube.com/watch?v=feBT0Anpg4A https://www.youtube.com/watch?v=feBT0Anpg4A
• smitty1e 6y ago
  After 50+ years, it occrred to me that if we consider body, mind and soul as axes of a 3D space, we can explain an awful lot of otherwise baffling human behavior. Treating these dimensions as orthogonal resolves much tension. For example, modern politics is soulless, and has ceased to be an intellectual exchange. It simply boils down to treating other peoples' bodies like livestock. Not flaming any countries, parties, or individuals here; merely being descriptive.