HTML5 Boilerplate: a rock-solid default - <AUTHOR> http://html5boilerplate.com/

<comment><USER2> Working on a similar analog to the .htaccess for nginx. Anyone with input/interest please fork and update as appropriate. Obviously we can't get 100% functional parity, but we can get close! <http://gist.github.com/518000>

</comment><comment><USER3> _HTML5 Boilerplate is the professional badass's base HTML/CSS/JS template for a fast, robust and future-proof site._

For me, future-proof means it's easy for me to maintain. There is just far too much here I find unnecessary to make it easy for me to maintain.

But then again, I find designing websites in Photoshop silly.

<comment><USER4> I think you can pull some of the good stuff from here that you need and leave the stuff you don't.

As for designing websites in photoshop, at work we do it in keynote. It works surprisingly well and you can use mocks for presentations too! reference -> <http://blog.swixhq.com/designing-swix-with-keynote/>

<comment><USER5> OmniGraffle is also a great tool for wireframing and simple web graphics. Every time I complete a task without opening Photoshop, I want to give OmniGraffle a high five.

</comment></comment></comment><comment><USER6> Neat resource, definitely something to borrow from, but I think I'm with Fuchs on this... <http://mir.aculo.us/2010/08/10/pragmatic-html-css/>

<comment><USER7> well said. i would find this more useful as a reference index than a template. it says "quickly" and "right-footed" but i think it's give and take between the two.

</comment></comment><comment><USER8> This is crazy awesome for power users that need a lot of control.

Philosophically, it makes something meant to be easy: html5, and makes it seem like rocket-surgery.

Either way, It's a great learning tool.

<comment><USER9> I wasn't sure whether to feel happy that all kinds of great cross-platform hacks were well-documented, or sad that so many millions of hours have gone into dealing with them. :-/ I wonder again when I see things like this whether the browser's let-me-lay-that-out-for-you approach was the panacea it sure seemed like at the time.

</comment></comment><comment><USER10> Interesting to see the use of HTML serialization instead of the usual XHTML stuff.

I've been going the HTML 4 (and now HTML5 with HTML serialization)route because I don't send pages as application/xml or whatever it should be. But it often means dicking with this or that tool or framework that bought into the previous future-proof technology, XHTML.

<comment><USER11> what does "HTML serialization" mean?

<comment><USER10> This might help: <http://answers.oreilly.com/topic/983-html-5-overview/>

This as well: [http://stackoverflow.com/questions/256953/html-5-versus- xhtm...](http://stackoverflow.com/questions/256953/html-5-versus- xhtml-1-0-transitional)

Basically, the spec says, for example, that HTML5 has an 'html' element, and it may contain a 'head' and a 'body' element. (I'm winging it here.) And the 'head' element may optionally contain one or more 'meta' elements with attributes ... whatever.

So far so good; the spec defines the structural items. But it also says, look, you can manifest, or serialize, this using XML (i.e. XHTML) syntax, in which case you need to have true, proper XML (and that means, for example, that empty elements such as 'meta' or 'br' must be closed, typically using the ' />' stuff). Or you can use HTML syntax, in which case there are a set of empty elements ('meta', 'br', 'img', for example) that do not need an end tags or that ' />' thing.

Also see: <http://hixie.ch/advocacy/xhtml>

It comes down to what you think browsers are going to do based on what you send them.

</comment></comment></comment><comment><USER12> Thanks for this. It's too bad it has to be so incredibly ugly to make up for various incompatibilities, but I really like the references commented in the code at least.

</comment><comment><USER13> Thanks for this link. I was just looking at a similar idea here: <http://html5reset.org/>

</comment><comment><USER14> I'm digging this! I will try it out for my next web project. Thanks!

</comment><comment><USER15> This is really great — an incredibly thorough set of templates.</comment>


Ask HN:  Where do I learn customer discovery skills - <AUTHOR>

I love building web apps and can build MVP's with the best of them.  My problem is that I suck at customer discovery. So I tend to build web MVP's that go no where with little to no feedback.<p>What tips do you guys have for weekend entrepreneurs like me who want to build web apps but suck at customer discovery? <comment><USER2> I feel your pain. It can be hard to get out of the building if you're just "searching" for an idea. If you're passionate about the idea And/Or you have to make it work - those help. Depending on your concept and the target demographic, it's much easier to put yourself where they are - and just ask questions. (B2C products are great for coffee shops, B2B at lobby area of a conference [so you don't have to pay to get in]).

I like putting myself into the flow of traffic to force it. Cold calls can be difficult, but the fear goes away after a while.

If you're looking for something formal, the Lean Startup Machine is a great experience that helps encourage you. (Not affiliated at all).</comment>


Econ major looking to break into startup culture. Advice? - <AUTHOR>

I'm an econ major, math minor at an ivy league school who's literally suffocating in my school's infatuation with wall street. I'd like to intern at and join a tech startup after graduation (currently a junior), but I'm not sure how to best approach the situation.
I consider myself pretty technically savy - I've built a couple of websites using PHP, rails, etc, but at my experience level anything I code would probably scale terribly. I'm "hacker compatible," but I understand my limitations as a developer.
I have a good sense of design. I can create presentations and pitches. I can network and feel out people. I'm persistent, and I'm not afraid of cold-calling or working 80+ hour weeks.
Ideally, I'd like to tackle everything that the serious hacker won't have time to focus on. However, I'm young, relatively inexperienced, and have no real connections that would make me a compelling "business guy" or "funding guy."
Also, I am debt free but also at basically nil savings. While I don't need much more than basic living costs, I simply can't afford to work for free.
Given my situation, how can I break into the startup scene? Should I be targeting early stage ventures? Companies that are already VC funded? Everyone I talk to is looking for a hacker. Should I stop trying to break in on the business side and focus on honing my hacker skills?
Thanks. <comment><USER2> Hal Varian wrote an article a while back talking about the importance of statistics. That and Econ might make you a good candidate for the right sort of position. Learning 'R' is apparently a good idea for that sort of direction.

<comment><AUTHOR> My econ degree is heavily econometric (stats) focused, so I have done a lot of R, Stat, EViews, etc. But I'm having a hard time figuring out how to make those skills applicable...?

<comment><USER2> Here's the article: <http://www.nytimes.com/2009/08/06/technology/06stats.html></comment></comment></comment>


The HP-01 (2009) - <AUTHOR> http://bytecollector.com/hp_01.htm <comment><USER2> Obligitary Techmoan link if you want to see a recent-ish video of this watch in action: [https://www.youtube.com/watch?v=gGQrsSEaZkI](https://www.youtube.com/watch?v=gGQrsSEaZkI)

</comment><comment><USER3> I remember seeing the HP-01 in BYTE. Sorry I don't remember which one off hand. But old BYTE magazines are like a trip back in time. The tech was shockingly primitive.

Download old BYTE magazines from here: [https://www.americanradiohistory.com/Byte_Magazine.htm](https://www.americanradiohistory.com/Byte_Magazine.htm)

Or higher quality scans here: [https://archive.org/details/byte- magazine](https://archive.org/details/byte-magazine)

Or Popular Electronics: [https://www.americanradiohistory.com/Popular- Electronics-Gui...](https://www.americanradiohistory.com/Popular-Electronics- Guide.htm)

Creative Computing: [https://archive.org/details/creativecomputing](https://archive.org/details/creativecomputing)

<comment><USER4> BYTE and Creative Computing are what made me fall in love with computing.

</comment></comment><comment><USER5> I love my HP-01. It is very fun to wear and use. Sometimes it gets comments. Unfortunately I cannot read it without my reading (or progressive) glasses anymore! For that, a Seiko Astron or Citizen works; angles are easier to read without glasses.

</comment><comment><USER6> Even if the Apple Watch flew to the Moon and back all on its own, it would only be half as cool as this starship commander's watch. Did James T. Kirk wear one of these?

<comment><USER4> They had wrist communicators in TMP.

</comment></comment><comment><USER7> I had one of these, of course it's many years lost, just like the stylus appears to be lost from the watch in the article.

</comment><comment><USER8> This is my dream watch. Absolutely. Too expensive though :(

<comment><USER9> The internet and eBay have ruined watch collecting... Especially if you're trying to get things on a budget. One article or blog post and it's over...

<comment><USER10> _OR..._ the Internet and eBay have made watch collecting accessible and broken down a lot of the barriers to entry that used to exist, and were jealously guarded by gatekeepers. Yes, the likelihood is that most collectible watches now cost more, but the prices are probably much closer to a far value for the seller as well as the buyer due to the lessening of the huge information asymmetry that used to exist. Now, the watch you found in grandpa's attic when looking through his estate after he died can be researched and priced accurately using the Internet, and it becomes much harder for unscrupulous dealers to obtain it for peanuts.

> "Oh, these Rolex Milgauss watches with a certificate showing it was > presented to your grandpa while he worked at CERN? [0] Yeah, there are loads > and loads of them floating about, sorry, they're really common. If it was > new, could be worth about five or six thousand pounds [1] but this is old, > used and pretty well worn so probably only worth a couple of thousand quid, > but I'll take it off your hands for GBP 2500.00 just to be nice, ok?"

0\. [https://onlineonly.christies.com/s/christies-watches- online-...](https://onlineonly.christies.com/s/christies-watches-online-play- time/rolex-milgauss-cern-dial-ref-1019-68/62180) \- Estimate was from 10K to 14K and sold for GBP 17000.00

1\. [https://www.rolex.com/watches/milgauss/m116400gv-0002.html](https://www.rolex.com/watches/milgauss/m116400gv-0002.html) \- Brand new from Rolex is GBP 6300.00</comment></comment></comment>


Why is Maxwell's theory so hard to understand? (2007) [pdf] - <AUTHOR> https://www.damtp.cam.ac.uk/user/tong/em/dyson.pdf <comment><AUTHOR> I actually have happened to delved quite a bit to "really" understand the Maxwell's equations. I've bought original treatise, books with its commentary and plain old "for idiots" sort of books. His original treatise is super dense and unapproachable. Right now we can wear Maxwell's equations on t-shirt but their original form were forbidding. Even with modern form you "really" need to get concepts of differential geometry if you want to just play beyond abstract. There are tons of hand wavy explanations of div and curl out there but almost all can be broken with crafting clever question like "ok, so what you think curl of that would look like?". I don't think even today I can claim I really get these concepts.

In any case, some of my biggest takeaways were these:

1\. There is no such thing as "proof" of Maxwell's equations. Just like Einstein's field equations, Newton's laws and many other things in Physics, Maxwell equations are also simply laid out as _lets assume these_. Vast majority of "greatness" in Physics is simply assuming something without needing to fully understand it and then cross your fingers to see if some good predictions comes out of it.

2\. The major achievement of Maxwell's equations is that you can predict velocity of light using other physical constants that have seemingly nothing to do with light. A consequence that we only later realized was that this was literally a constant and not relative to who is measuring it! This is easily one of the most non-obvious achievement in Physics.

<comment><USER2> You should try to understand differential forms, if you have those then Maxwells equations in vaccuum really aren't strange any more.

But Differential forms aren't that strange really. They are the mathematical objects that allow you to integrate along surfaces and curves. Of course their theory hadn't been developed when Maxwell wrote them. And Maxwell was very much concerned with EM in matter, which mixes the properties of the EM fields and materials, and that can thus be expected to get a bit messy.

But I don't see what you are striving for when you say "really" understand them. I think this is a psychological category, rather than a hard criterion. Can you apply the formalism to calculate consequences? That's the main issue. Maybe you can have a better or worse intuition about the consequences, but that is often mainly due to practice. You can't expect to correctly intuit all possible consequences of a system as rich as EM.

> Young man, in mathematics you don't understand things. You just get used to > them. -- John von Neumann

<comment><USER3> Could you recommend a good (accessible) reference on differential forms?

<comment><USER4> I'm late to the party and not the person you asked, but I've been trying to work through [https://smile.amazon.com/gp/product/0817683038](https://smile.amazon.com/gp/product/0817683038) It's good so far.

</comment></comment></comment></comment><comment><USER5> A lot of the early days failure of Maxwell was his notation was insane. As others notice below; Heaviside notation[1] made it a lot easier to follow and calculate things. Notation is underrated as increasing human power: I'm not sure General Relativity would have been possible without Christoffel notation. FWIIW fun stuff to read; Whittaker's theories of Aether and Electromagnetism gives the detailed history of all this. Cheap from Dover books. Mind blowing in how theoretical physics used to work.

[1] [https://books.google.com/books?id=nRJbAAAAYAAJ&pg=PA109#v=on...](https://books.google.com/books?id=nRJbAAAAYAAJ&pg=PA109#v=onepage&q&f=false)

<comment><USER6> Einstein Notation is similar in this regard. It makes the 'mechanics' of tensor mathematics much easier to deal with. Kinda like how arabic numerals are a lot easier to manipulate than roman numerals.

I'm not sure sure, but I believe that Helen Dukas, Einstein's secretary, is the one who came up with Einstein notation originally. She was just trying to get through his notes faster when writing things up and that method of notation later became accepted. I can't find that citation though, so calling it Dukas Notation is for the moment erroneous.

<comment><USER7> To hell with it. So much great work from lowly support, frequently women, has been robbed of its rightful place. Call it Dukas notation until proved otherwise. Crick and Watson still have their ill-gotten novel prizes and most are unaware they are little more than thieves. (Wildly racist and sexist, sure, hard to deny that nowadays so we don't talk about it as loudly as we should).

tl;dr

"Dukas notation" just sounds good.

<comment><USER6> I believe that you have misunderstood. I do not know if Helen Dukas in fact is responsible for this.

<comment><USER7> I don't think so, fwiw.

"Call it Dukas notation until proved otherwise."

</comment></comment></comment></comment></comment><comment><USER8> Maxwell's theory is hard to understand because it's based on an almost-but- not-quite-appropriate algebra. It's like stringly-typed programming. It _works_ , but it's messy and hard to understand.

Maxwell's set of coupled differential vector electromagnetic equations simplify to a hilariously short _single_ equation in Geometric Algebra.

A random Google turned up this paper comparing classic EM and the GA formulation. It's not even the simplest possible representation, because that uses natural units and a 4D GA to basically condense the entire set of EM theory into about 4 characters worth of equation that is _fully relativistic_ for free: [https://www.researchgate.net/publication/47524066_A_simplifi...](https://www.researchgate.net/publication/47524066_A_simplified_approach_to_electromagnetism_using_geometric_algebra)

It's almost a joke. To me it's reminiscent of looking at beginner programmers. You see them do crazy things like calculate a date "next month" by taking apart the pretty-printed date string, parsing to find the month, realising that sometimes the day part is one digit and sometimes it's two, then having to worry about m-d-y or d-m-y formats, building little tables of "days per month" and leap years... and so on.

They can write pages and pages of _error free_ code and it's still Wrong because the correct way is to just call "thedatevar.AddMonth(1);" and be done with it.

PS: 3D game engine vector algebra libraries have all of this in common with the physics maths. Things like the cross product being bizarre, having to pick a basis, not being able to interpolate rotations, gymbal lock, rounding error, having different maths for 2D and 3D, a bunch of special cases to worry about, and so forth...

Watch Enki Mute's Siggraph 2019 presentation on Geometric Algebra. It's mind- blowing how many stupid little quirks of vector algebra just _evaporate_ if you're prepared to step outside of your comfort zone: [https://youtu.be/tX4H_ctggYo](https://youtu.be/tX4H_ctggYo)

<comment><USER9> The speaker in the video runs a community for people interested in geometric algebra.

[https://bivector.net/](https://bivector.net/)

Check out the demo [https://observablehq.com/@enkimute/animated- orbits](https://observablehq.com/@enkimute/animated-orbits)

Job the discord [https://discord.gg/vGY6pPk](https://discord.gg/vGY6pPk)

<comment><USER8> GA _seems_ to be getting more popular, but I still see vector algebra used in areas such as robotics where GA is _clearly_ superior. In that application the small performance difference between GA and vector algebra is irrelevant, but the advantages of GA are huge.

In game engines the vector algebra method is slightly faster, so the elegant programming model is often sacrificed in the name of performance.

That, I can understand.

Why physicists use at least 4 separate formulations of the EM equations I can't understand, especially considering the vector version is the _worst_ yet the most popular.

<comment><USER10> How can it be faster considering that they are equivalent?

<comment><USER11> Computers don't care about mathematical equivalence. For instance, dividing by a number is generally slower than multiplying with the inverse of that number. Also, memory access patterns can make a difference of night and day.

I'm not sure though where exactly the idea that GA is slower comes from. It's all down to the application and implementation. Perhaps it's because GA generalizes so well to higher dimensions that many libraries are overly generalized and thus slower than vector algebra libraries that _need_ special cases anyway.

<comment><USER8> The 3D case is often handled using a conformal projective geometric algebra, which is 5D and requires 2^5 = 32 elements for a general multivector. This is twice that of a 4x4 matrix, and and eight times the size of a 4-element homogeneous vector as typically used in most 3D engines.

Of course, there are all sorts of optimisations. Most GA libraries are actually based on code-generation and support various "subsets" of the full GA to efficiently represent things like vectors only. From what I've seen, even a well-tuned library has approximately a 25% overhead for hot paths and 50-100% is typical.

This is a bit like representing a simple rotation like the hand of a clock, with either just one angle, or a two-element unit vector pointing in the direction of the rotation. The one-element angle has a bunch of special cases, like have to be checked to see if it goes past 360 degrees and then reset back to the 0..360 range. Representing this with two numbers just requires multiplication with a matrix, which involves no conditionals or modulo arithmetic.

This is analogous to the vector vs geometric algebra. Typically, GA has no special cases and "just works", but it does so by "uncompressing" the compact vector representation. It's going to be slower.

</comment></comment></comment></comment></comment></comment><comment><USER12> It appears no one here has actually read the essay. He's not talking about mathematical complexity of Maxwell's equations (and no, you can use differential forms, Clifford algebras, quaternions, vector calculus, but no matter how you write it, it's still the same thing, and at the end of the day, you will end up solving _exactly_ the same set of coupled partial differential equations, to the letter --there's no magical mathematical notation that makes this go away).

The difficulty he's referring to is in the physics (and not mathematics) associated with the idea that fields are real, fundamental physical entities, and cannot be reduced to mechanical models with "gears and wheels" permeating the space (which was a popular idea back then).

<comment><USER13> You prompted me to read the actual essay. It was considerably more interesting than the comments here would have suggested; which is not a surprise, given it was penned by Freeman Dyson.

His insight that Maxwell's contemporaries lacked even the language to fully describe what a transformative idea he had is acutely interesting. Once again language both shapes and traps thinking.

He makes the same point with quantum mechanics as well - that we're constrained by not having the proper language to describe the most fundamental behaviour. I think it's fair to say that point still stands today.

</comment></comment><comment><USER14> Modern notation has contributed greatly to making Maxwell's equations more understandable. I dare you to have a look at Maxwell's original paper ([https://royalsocietypublishing.org/doi/10.1098/rstl.1865.000...](https://royalsocietypublishing.org/doi/10.1098/rstl.1865.0008)) and try to understand it, I'd say even for a seasoned physicist it's not trivial. Compare that to the modern differential form of the equations (e.g. [https://en.wikipedia.org/wiki/Maxwell%27s_equations](https://en.wikipedia.org/wiki/Maxwell%27s_equations)), which (IMHO) are really easy to understand even for second-year Physics students (given that you understand the underlying vector operators).

Personally, I found the "flow analogy" always the most intuitive, and there are some books that teach electrodynamics in that way. Typically one would start with electrostatic problems and work one's way to the more complicated stuff like magnetic fields.

I guess to derive a "complete" understanding of classical electrodynamics you need to understand the concept of relativity as well. Magnetism is a consequence of relativity and the finite speed of light, so if you accept that it becomes easier to understand (IMHO). Of course you then have to "understand" relativity, which just moves the problem to a different area. But then again, it's always like that in Physics :)

<comment><USER15> > Magnetism is a consequence of relativity and the finite speed of light

That doesn't make any sense.

<comment><USER16> Here's a video explainer: [https://www.youtube.com/watch?v=1TKSfAkWWN0](https://www.youtube.com/watch?v=1TKSfAkWWN0)

Magnetism affects moving charges, but not stationary charges. A magnetic field in your reference frame is really just an electric field in the moving charge's reference frame.

</comment></comment></comment><comment><USER17> With a lot of theories I find the breakthrough in discovery is separate from the breakthrough in explanation.

How quickly was it that the familiar four vector equations were published? When you come across them now in an undergrad class, it seems so simple because a lot of work went into distilling the insight into the bits that matter. When the theory was still being fleshed out, there were probably a load of intermediate steps acting like a scaffolding.

Likewise with relativity, you can pick up a book and read about it because a lot of people have looked at it over the years and figured out which explanations actually work.

<comment><USER18> Explanations that work for whom? I can't speak for electromagnetism or physics. What I can say is that for years I felt like I didn't have the least bit of clarity on color modeling until I referred to Maxwell's primary materials, which are cited by just about no one sadly.

<comment><USER19> Could you explain this a bit? (Excuse me if I'm asking too much, I don't really know what you mean by color modeling, and how it connects to Maxwell - or maybe you are talking about wavelengths?)

<comment><USER20> [https://en.wikipedia.org/wiki/Color_triangle#Maxwell's_disc](https://en.wikipedia.org/wiki/Color_triangle#Maxwell's_disc)

</comment></comment></comment></comment><comment><USER21> This is a wonderful essay, and I wish I had come across it as a freshman. For example:

"Just as in the Maxwell theory, the abstract quality of the first-order quantities is revealed in the units in which they are expressed. For example, the Schrödinger wave-function is expressed in a unit which is the square root of an inverse cubic meter. This fact alone makes it clear that the wave- function is an abstraction, for ever hidden from our view. No-one will ever measure directly the square root of a cubic meter."

That, of course, is an observation about quantum mechanics, and it is only on rereading the essay today that I noticed its structure: Dyson begins with an anecdote about Maxwell giving an address that spent most of its time discussing some features of Helmholz's "splendid hydro-dynamical theorems" (with a nod to Kelvin, who I guess was present), before briefly drawing analogies to his electrodynamical theory. Dyson brings this up within an essay in which he uses Maxwell's theory to make a point about coming to understand quantum mechanics, though he spends rather more time on his ultimate topic than Maxwell did in his talk.

</comment><comment><USER22> Maxwell's equations are an artifact of the Mathematical Formulation and they can be written in a perhaps easer way. If one describes them in Geometrc Algebra terms it is just one equation [0] and one can understand it in a natural way.

During the nineteenth century and the discussions on different formal ways to describe vector fields Hamilton's quartenion system prevailed. Maxwell had reservations and presented his treatise of electricity and electromagnetism as "the introduction of the ideas, as distinguished from the operations and methods of Quaternions" [1], thus the formulation we know.

[0] Mathematical descriptions of the electromagnetic field [https://en.wikipedia.org/wiki/Mathematical_descriptions_of_t...](https://en.wikipedia.org/wiki/Mathematical_descriptions_of_the_electromagnetic_field)

[1] The vector algebra war a historical perspective [https://arxiv.org/pdf/1509.00501.pdf](https://arxiv.org/pdf/1509.00501.pdf)

<comment><USER23> Currently with Maxwell's equations you can point to each one and couple it with an experiment.

If you simplify the equations any further, it will be a result of mathematical elegance rather than fundamental undergraduate-level physics.

<comment><USER8> > and couple it with an experiment.

Only a handful of special cases that have obvious "paradoxes" that cannot be explained with Maxwell's equations.

It's not even a fully general set of equations classically, it can only handle a certain constrained motions at low velocities, short distances, and generally without accelerations.

I mean sure, a map is simple to understand and is fine for navigating a city, but let's not pretend the Earth is flat and then only introduce its spherical geometry in 2nd year studies. That's not the right pedagogical approach.

<comment><USER24> _> Only a handful of special cases that have obvious "paradoxes" that cannot be explained with Maxwell's equations._

What are you talking about?

 _> It's not even a fully general set of equations classically, it can only handle a certain constrained motions at low velocities, short distances, and generally without accelerations._

Huh? Maxwell's Equations are relativistically invariant and cover all classical electrodynamic phenomena. The only thing they don't cover is quantum mechanics (although in quantum field theory Maxwell's Equations are still the field equations of the quantum electromagnetic field, so even there they play a role).

<comment><USER8> Maxwell's equations only apply to static states, including steadily circulating currents. It's not _generally_ applicable without extensions to more complex scenarios such as handling time delays and arbitrary movement.

[https://en.wikipedia.org/wiki/Li%C3%A9nard%E2%80%93Wiechert_...](https://en.wikipedia.org/wiki/Li%C3%A9nard%E2%80%93Wiechert_potential)

[https://en.wikipedia.org/wiki/Jefimenko%27s_equations](https://en.wikipedia.org/wiki/Jefimenko%27s_equations)

The apparent "paradoxes" are literally the reason Einstein started on his journey to develop Special Relativity.

[https://en.wikipedia.org/wiki/Moving_magnet_and_conductor_pr...](https://en.wikipedia.org/wiki/Moving_magnet_and_conductor_problem)

[https://en.wikipedia.org/wiki/Relativistic_electromagnetism](https://en.wikipedia.org/wiki/Relativistic_electromagnetism)

<comment><USER24> _> Maxwell's equations only apply to static states_

Nonsense. Maxwell's equations are the equations of classical electro _dynamics_.

 _> It's not generally applicable without extensions to more complex scenarios such as handling time delays and arbitrary movement._

The equations for the Lienard-Wiechert potentials are mathematically equivalent to Maxwell's Equations (when you put those equations in potential form instead of field form and make an appropriate choice of gauge).

Jefimenko's equations are also mathematically equivalent to Maxwell's Equations; their originator believed that the causality properties of those equations would be clearer when put in his preferred form. Whether or not he was right is a matter of considerable debate.

 _> The apparent "paradoxes"_

Are a result of lack of understanding on the part of the people claiming and promoting them.

 _> are literally the reason Einstein started on his journey to develop Special Relativity_

Nonsense. The problem Einstein had when he developed SR was not Maxwell's Equations; it was _Newton 's_ equations. He realized that Maxwell's Equations and Newton's equations were inconsistent. Every other physicist at the time who realized that (and there were many) believed that the way to fix that problem was to modify Maxwell's Equations and leave Newton's equations the same. Einstein, however, realized that the way to fix the problem was to modify _Newton 's_ equations and leave Maxwell's Equations the same. The result was SR, and the rest, as they say, is history.

</comment></comment></comment></comment></comment></comment><comment><USER25> This is a lovely essay, but I think it goes a little too far in claiming that the electromagnetic field is intangible or immeasurable, in slightly forced analogy with quantum mechanics.

> We now take it for granted that electric and magnetic fields are > abstractions not reducible to mechanical models. To see that this is true, > we need only look at the units in which the electric and magnetic fields are > supposed to be measured. The conventional unit of electric field-strength is > the square-root of a joule per cubic meter... This does not mean that an > electric field-strength can be measured with the square-root of a > calorimeter. It means that an electric field-strength is an abstract > quantity, incommensurable with any quantities that we can measure directly.

A more conventional way to think of the dimensions of the electric field is [force]/[charge] (e.g. units of Newtons/Coulomb), and you can observe the electric field by observing the force it exerts on a charged particle through

f=qE

for example by observing the trajectory of an electron in a cloud chamber.

Dyson says that the square of the field is a measurable energy density, but it's arguably harder to measure an energy density than it is to measure a force.

Dyson's point is much more true for quantum mechanics, where the only measurable things seem to be quadratic combinations of the wave function, and I do like the analogy he points out with electromagnetism, but I think he oversimplifies a bit to make his point.

<comment><USER26> > not reducible to mechanical models [...] is much more true for quantum > mechanics

Yes, but... a caveat.

How big is an atom? "Unimaginably small" is an oft repeated phrase. What is an atom? "Definitions [...] models [...] skill at switching between models". Electron behavior? Quantum... "unintuitive... the equation _is_ understanding".

So how well is "small" taught? Horribly, even by the lackluster baseline of current science education research. Asking first-tier medical school graduate students how big cells are, is not happy thing. But hey, maybe cells are "unimaginable" too.

So how well are atoms taught? One challenge in teaching high-school stoichiometry, is students not thinking of atoms as _real_ , as physical objects. But hey, maybe that's a failure to "switch models".

So how well is electron behavior taught? Well, when students use the many realistic interactives emphasizing molecular electron density... oh wait. Well, when students view the many molecular dynamics videos showing electron density... oh wait. They _do_ exist... now find them without using google scholar and sending people email. :/ But hey, if students ever do see them some year, maybe no understanding will result, given how unintuitive it all is.

Punchline? Teaching things badly seems associated with failure attribution errors. As with education research that's "we taught atoms really badly... surprisingly that didn't work... so we draw the obvious conclusion... students of this age aren't developmentally able to understand atoms".

And physics side... there often seems a blurred vision of objectives and their properties. There are a great many plausible learning objectives between "atoms are real" and "i∂_{t}ψ=Hψ". And the usefulness of "mechanical" models varies greatly among them. So "the equation _is_ understanding" gets repeated, in contexts where it's inappropriate, and where it distracts from a broad long-term societal failure to improve wretched science education content.

</comment></comment><comment><USER27> This paper captured what I encountered as a TA in the 90's: students could solve the integral forms, but had trouble with the differential due to fields. I think this is because some students have a very difficult time going from the mental image of fields as 2D arrows, to div, curl and grad in practice. There's a big step function there in manipulating the equations. I wasn't a very good TA because I didn't have much luck explaining to the struggling students (still feel bad about that, sorry folks, I was getting my master's degree and had no choice to be a TA). And students who didn't understand this in second-year physics had even more trouble when their EE classes went into field and waves classes (conductors, antennae, etc.).

TL; DR: I think this is more a problem with teaching advanced differential calculus concepts than Maxwell.

</comment><comment><USER28> Once you understand VC operators (grad, div and curl) and the associated intergals, Maxwells Equations are actually really intuitive and quit beautiful. I was lucky that the maths course I was on covered those a few weeks before we started electrodynamics. Plus I had Mary Boas Mathematical Methods in the Physical Sciences which teaches this material (and Greens theorem etc) very well.

</comment><comment><USER29> Theory of electromagnetic field (of which Maxwell's is a part) was one of my favorite topics in the university. The other being digital signal processing. I don't have very good memory, so I have to rely on things having a lot of consistency and internal structure so they could be efficiently "compressed" and "recovered". Both of these fields have that - the math is consistent, beautiful, and somewhat more intuitive than in other fields. Theory of electromagnetic field does assume that your integral and differential calculus is pretty good though.

</comment><comment><USER30> > Mathematics is the language that nature speaks.

Nature seems to speak in forces and had been doing so long before we arrived and started honing our math skills.

Nature made an imprint on our math. Newton came up with new math to make more accurate physical predictions.

There is a good reason to be an adherent to the mathematical descriptions. We might want the photon to go through only one slit, To help make nature more classical and understandable, but that's not the nature we know and observe. So we keep to the math and let it speak to us, lest our work-a-day understandings of the world lead us astray.

</comment><comment><USER31> I've seen the "another theory which I prefer" quote mentioned elsewhere (possibly with reference to this paper) as being a form of modesty. I would say that it looks to me like typical British understatement, which is often misunderstood (particularly by Americans) and may have been simply an attempt at humour on his part.

[https://en.wikipedia.org/wiki/English_understatement](https://en.wikipedia.org/wiki/English_understatement)

<comment><USER32> The author of this piece, though, is British.

</comment></comment><comment><USER33> So not so much hard to understand (at least for trained physicists at the time), rather too much modesty from Maxwell himself to shout about the importance of his discovery.

</comment><comment><USER34> Excerpt:

"Maxwell explained how the ancient theory that matter is composed of atoms ran into a logical paradox.

On the one hand, atoms were supposed to be hard, impenetrable and indestructible.

On the other hand, the evidence of spectroscopy and chemistry showed that atoms have internal structure and are influenced by outside forces.

This paradox had for many years blocked progress in the understanding of the nature of matter. Now finally the vortex theory of molecules resolved the paradox. Vortices in the aether are soft and have internal structure, and nevertheless, according to Helmholtz, they are individual and indestructible.

The only remaining task was to deduce the facts of spectroscopy and chemistry from the laws of interaction of the vortices predicted by the hydrodynamics of a perfect fluid."

</comment><comment><USER35> This is a lovely essay. Wonderful layers-of-reality analogy to quantum mechanics.

<comment><USER36> Yes. That's the reason why I saved it. I don't know much about quantum mechanism, but I could feel a vague intuition developing after reading this essay.

</comment></comment><comment><USER37> We've all gotten used to the idea that Electric and Magnetic fields are real but then we learn about the Aharonov-Bohm effect and suddenly, maybe it's the electric potential and magnetic vector potential are what is 'real'. But then, there's all the issue with gauges.

I think that the best way of teaching electromagnetism might still be in the future.

</comment><comment><USER38> This is fundamentally a sociological (or philosophy of science) essay rather than about why Maxwell's equations are still so hard to understand for the student. In that it's quite interesting but I found the jump to a parallelism between the model of Maxwell's and quantum mechanical models a bit of a stretch.

</comment><comment><USER39> Very interesting article, I think there's a lot of parallels there to business and startups. I'm a technical person who has always struggled to promote, and it seems scientists/researchers face the same issues. The ideal is to be a showman and technically brilliant.

</comment><comment><USER40> Previous interesting HN discussion on the same paper: [https://news.ycombinator.com/item?id=18837677](https://news.ycombinator.com/item?id=18837677)

</comment><comment><USER41> " We, with the advantage of hindsight, can see clearly that Maxwell's paper was the most important event of the nineteenth century in the history of the physical sciences. If we include the biological sciences as well as the physical sciences, Maxwell's paper was second only to Darwin's ``Origin of Species''."

By what metric? How has Darwin's ``Origin of Species`` been even half as prolific as Maxwell's work? Maxwell's work revolutionized our understanding of the physical world and had lead to the creation of thousands upon thousands of technological advances. It has literally forged the modern world.

<comment><USER42> I think Darwin gets special note for the fact that while there are many incredible works of theory in math and physics, there's really only one in biology: _On the Origin of Species_ by Charles Darwin.

<comment><USER41> Certainly not saying that it's not noteworthy, but if I had to make a top 5 list he wouldn't be on it. Apparently, my metric and the authors metric are different.

</comment></comment></comment><comment><USER43> Does the professor's claim that the "origin of species" is more important than Maxwell's equations got any real takers? Or is it just his personal opinion?

</comment><comment><USER44> what happened to Maxwells original quaternion based equations. the changes made against his will by lorrentz and others to simplify after his death were an affront to science and have set back humanity a hundred years.

</comment><comment><USER45> Ah, yes. It's not the ignorant physicists' fault that Maxwell's theory hasn't got the attention it deserved. It's Maxwell's modesty's fault that set back the science of physics two decades. What a ridiculous notion.

</comment><comment> vincent-toups Try SU(3) Yang Mills!

<comment><USER15> Why not SUSY then? Once you understand the formalism you can derive any field theory to your liking.

</comment></comment><comment><USER46> > Modesty is not always a virtue

Seriously... where and when in the last 50 years in modern society was modesty ever a virtue? I certainly wouldn't expect anything like that at Princeton in the US.

Otherwise an interesting essay nevertheless, but I certainly don't agree with all the points.

> Mendel's modesty setback the progress of biology by fifty years.

Hilarious conjecture.</comment>


Don McCullin captured history in the making - <AUTHOR> https://www.1843magazine.com/culture/look-closer/how-don-mccullin-captured-history-in-the-making <comment><USER2> > and the policemen wear polished shoes and self-important expressions

Their faces range from no expression whatsoever to a slight smile. But please, don't let that stop anyone from assuming their thoughts based upon a momentary countenance.

<comment><USER3> All the great content in that article, and all you were able to take away from it was an opportunity to get offended on behalf of a bunch of cops?

<comment><USER2> No, that's what I felt like deserved comment. Compare to recent events in the US. It isn't cool for media to disparage people who aren't given opportunity to speak for themselves.

As far as offended, no?

</comment></comment></comment><comment><USER4> > the dead Khmer Rouge soldiers in a crater in Cambodia, Congolese soldiers > tormenting freedom fighters in Stanleyville, young Christians on a bombed- > out Beirut street, posing like a boy band over the body of a dead > Palestinian girl.

One thing I learned from photography, is that you can basically use it to tell any story that you want. Take for example a war. You want to make side A out to be courageous heroes - there are photos you can take to do that. Want to make them out to be homicidal psychos, you can do that as well. A lot of photography depends on the story the photographer is trying to tell.

Compare the war photographs from WWII vs Vietnam. The WWII war photographs in the American press were by photographers who were deeply favorable to the American cause, and so many of the photographs paint the Americans as heroic warriors - the best example being the raising of the flag on Iwo Jima. The Vietnam photos were taken by photographers who were largely opposed to American involvement, and a lot of the most famous photos emphasize either American or South Vietnamese attrocities (the impromptu execution of a captured Vietcong member, the naked, burned child, Mai Lai massacre).

Just looking at the photos and the list of his famous photos, it seems that Don McCullin's sympathies lay with those who were opposed to the capitalist West.

<comment><USER5> > Just looking at the photos…

Perhaps look harder.</comment></comment>


Battery-Free Cell Phone - <AUTHOR> http://www.techradar.com/news/this-phone-needs-no-battery <comment><USER2> Related, this spying microphone bug first used by the Soviets in the 50s that has no battery or electricity wire and can keep listening "forever", which was discovered by accident in a "gift" eagle sculpture given to the US ambassador, after years of staying in that embassador's office, listening [https://en.m.wikipedia.org/wiki/The_Thing_(listening_device](https://en.m.wikipedia.org/wiki/The_Thing_\(listening_device)

<comment><USER3> The Thing could not receive transmissions, though.

Which makes this all the more impressive!

The Thing actually needed power to operate, btw. The power was just beamed in externally.

<comment><USER4> As far as prior art on the receiving side lets not forget about good old fashioned crystal radios [https://en.m.wikipedia.org/wiki/Crystal_radio](https://en.m.wikipedia.org/wiki/Crystal_radio)

</comment></comment></comment><comment><USER5> There were earlier discussions on this.

> _Right now the battery-free phone needs a custom base station to transmit > and receive calls. But the team says there 's no reason why the technology > couldn't be integrated into standard mobile network infrastructure._

This could only be called a cell phone, if the cell phone network changes to accommodate this radio. It's not a cell phone, because it doesn't work with cellular phone towers.

<comment><USER4> I agree calling it a cell phone sets the wrong expectations, but it's still neat and I think a good application could be an elder care pendant (help, fallen, can't get up, yadda yadda) where close promity and custom base station aren't an issue, but never needing to worry about the status of battery would be a big plus.

<comment><USER5> I agree!

Those applications are called medical alert systems, and there are various kinds. Some of the systems contain GPS, while other work with a radio base station to inform if the person has fallen and can't get up.

For example, [http://www.best10medicalalertsystems.com/](http://www.best10medicalalertsystems.com/)

</comment></comment></comment><comment><USER6> When tech writers write about things they don't understand, they tend to omit all the caveats, like "cripplingly short range" and "probably illegal to operate as a consumer device due to RFI".

<comment><USER7> Probably legal due to the frequencies involved, but also useless in anything but a completely radio-quiet environment (the ISM bands are specifically allocated to common interference sources --- and the only reason other wireless devices like WiFi and BlueTooth can survive there are due to processing techniques that can transmit/receive below the noise floor, like spread spectrum.)

<comment><USER8> Even if it operates in the unlicensed freq. bands, ie ISM bands, there are still limitations to how much you may interfere with others, expressed in eg duty cycle requirements (ie not sending too long at a time) and energy levels (ie not sending too strong). That's what the FCC/ETSI/CE etc etc regulations do.

</comment></comment></comment><comment><USER4> So this uses vibrations caused by our voice to change the effectiveness of the antenna to absorb power from the base station right? Base station then interprets the varying current draw as amplitude modulated audio and Bob's your uncle? If I'm correct (no sure that I am) wouldn't this require being pretty close to the base station?

<comment><USER9> Thinking about this I wonder why there's no kinetic charger.

<comment><USER10> I'm suddenly picturing a shakeweight or crank cell phone

<comment><USER11> I would definitely buy a crank cell phone if I were allowed to clone my sim (for emergencies).

<comment><USER12> [https://www.amazon.com/Peach-Dynamo-Charger-Emergency- Supply...](https://www.amazon.com/Peach-Dynamo-Charger-Emergency- Supply/dp/B01NBM5S0C/)

3.99 with free shipping.

</comment></comment></comment></comment></comment><comment><USER13> > _The biggest step was eliminating the analog-to-digital converter that turns > your voice into data. Instead, they took advantage of tiny vibrations that > happen in a microphone when a person is talking into it, or a speaker when > someone is listening. An antenna converts that motion into radio signals in > a way that uses almost no power._

Does it mean the voice is transmitted in plaintext using analog modulation of (reflected) carrier wave? Privacy concerns aside, how can it handle calls from multiple stations over same frequency range?

<comment><USER14> Voice is always transmitted in a "plain text" is it radio or phone except if you use some special device (it's never easy to get one) and protocol (good luck to access it for cheap).

<comment><USER15> But GSM is fully digital and encrypted

<comment><USER16> poorly encrypted

<comment><USER15> Yes but it's not just a naked signal of the audio as this is.

</comment></comment></comment></comment></comment><comment><USER17> I'd like to try to make a mobile device like this that can run with ~100mA input power from a solar cell. I thought about using the Particle Photon & an E-ink display, but my knowledge of hardware isn't the greatest. Any EE out there think it's possible?

<comment><USER18> How large of a device do you have in mind? 100 mA is more than enough power for the Photon module, but would require a relatively large solar cell -- probably at least 3 to 4 inches square under ideal conditions.

<comment><USER17> That's roughly the size I was thinking. I was thinking of adding a battery too, less as a storage bank and more as a way of papering over the ideal conditions issue.

<comment><USER19> Have those graphene supercapacitors become commercially available? If so, you may be able to do without a battery at all. Well, depending on use, available charge, and efficiency.

</comment></comment></comment></comment><comment><USER20> Battery-free wireless headset would be a better name I believe.

<comment><USER21> Wait. Depending on how loud this thing can go, it could be 100% effectively pivoted as "world's first battery-free wireless headphones". Start a company selling that and use it to fund R&D to remove the PTT switch from the communicator design etc.

<comment><USER22> The main problem with wireless headphones currently is unreliable/lossy connection, and latency. This would make it worse.

<comment><USER21> Is this design analog or digital? If it's analog, all those issues are replaced by static noise, which could very probably be largely mitigated by amplification power and possibly audio processing on the transmitting side.

</comment></comment></comment></comment><comment><USER23> Previous discussions:

[https://news.ycombinator.com/item?id=14659236](https://news.ycombinator.com/item?id=14659236)

[https://news.ycombinator.com/item?id=14716986](https://news.ycombinator.com/item?id=14716986)

</comment><comment><USER24> This is an incredible feat.

It runs on 3.5uW, and the homemade cellphone I built last year with off-the- shelf components drew 2A when syncing with GSM antennas.

Some people don't realize it, but GSM is very expensive power-wise, especially on boot when it has to find antennas. Having a device that can be solar powered or even with ambient radios is extremely useful!

      Right now the battery-free phone needs a custom base station
      to transmit and receive calls. But the team says there's no reason
      why the technology couldn't be integrated into standard mobile network infrastructure

Well, there's the trick. But an awesome proof of concept nonetheless

<comment><USER25> I'm a bit puzzled by the statement "But the team says there's no reason why the technology couldn't be integrated into standard mobile network infrastructure"

There's obviously many reasons. Transmission range, security, privacy, reliability, ...

</comment></comment><comment><USER26> Here I am in 2017 reading this, and yet I can only dream of an iPhone with a battery life greater than one day.

<comment><USER27> Apple is building this so they don't have to give you a battery at all.

I'm always confused by people complaining about iPhone battery life. My wife's iPhone 6 lasts days, it's called a battery pack. And she gained this incredible battery life without forcing me to carry a heavier bulkier iPhone. That's what Apple understands, making their devices heavier and thicker to please a minority of users while inconveniencing the majority makes no sense when battery packs exist.

</comment></comment><comment><USER28> Is this what Tesla dreamt about? It's incredible.

</comment><comment><USER29> The low power usage of the device is impressive (I think), but the battery free part not so much. It seems as though this is just the modern day version of the crystal radio sets many of us built (or tried to) when we were kids.

</comment><comment><USER30> Nice, but then what about a thousand miles using a voice powered transmitter? [http://soldersmoke.blogspot.it/search?q=El+silbo](http://soldersmoke.blogspot.it/search?q=El+silbo) [http://qrznow.com/amateur-radio-transmits-1000-miles-on- voic...](http://qrznow.com/amateur-radio-transmits-1000-miles-on-voice-power/)

</comment><comment><USER31> My dream phone would have a small e-ink display that can maybe read wikipedia or text based websites, simple physical buttons, and a 5000 mAh battery, maybe even some low discharge chemistry instead of lion, shooting for a charge maybe once a month.

Naturally GPS would be right out...

Pretty sure the potential market size is in the single digits, but I'd be happy.

</comment><comment><USER32> Is this sort of passive device practical for applications such as wireless mouse and keyboard? It would seem like a great selling point (similar to Logitech's attempts to make solar powered peripherals)

</comment><comment><USER33> Looks like it doesn't support snapchat or texting, so Im sure the "festival goers" aren't going to be doing backflips over it.

I could use this in my spy operations though. Not that Im a spy or anything.

Definitely, not a spy.

</comment><comment><USER34> I've been wondering. Is it possible to build a logic circuit out of a radio frequency? If so, it would be possible to build a computer out from it.

</comment><comment><USER35> If this is basically push-to-talk, then I wonder if it might have some good applications as a walkie-talkie / handheld radio?

</comment><comment><USER36> Makes you wonder if this was what was being tested in Cuba that attacked the diplomats.

</comment><comment><USER37> This has been posted here earlier and HN couldn't get over how it's not perfect, just like Atom. HN isn't the audience for "big-picture" technologies that will get more efficient over the years and have broad applications eventually.

<comment><USER38> Agreed. Given YC's "launch early and iterate" mindset, it's surprising how little that is reflected in the HN comments for new projects.

</comment></comment><comment><USER39> what about using this tech to create a backup pager.

I'd love a device that ONLY does sms or text based comms (fb, whatsapp etc..) but only the text. and nothing else.

that would sip battery.

</comment><comment><USER40> Time to start optimizing Android and iOS, haha...</comment>


Interview with a Tor developer who works on hidden services - <AUTHOR> https://blog.torproject.org/blog/nine-questions-about-hidden-services <comment><USER2> Is there added security by stacking hidden services? So a.onion is just a reverse proxy for b.onion? Buys you a bit more time before the final server gets popped? Or can you increase the number of Tor hops for your hidden service to get a similar effect?

Thinking of Silk Road - was it ever proved they leaked their IP versus some more advanced way of finding the server? (I know, it's highly likely that such a poorly written system would have had a real IP leak, just wondering what documented facts we have.)

<comment> at-fates-hands The investigators claimed they found it when the login page leaked its IP. It was one of the more contested facts of the case - some thought it was possible, other infosec people thought it wasn't.

There are stories that say Ulbricht was notified by someone in one of the chat rooms that the site was leaking IP addresses, but Ulbricht never fixed it, which allowed the FBI to find the real server in Iceland.

Wired did a great two part article on the story:

[http://www.wired.com/2015/04/silk-road-1/](http://www.wired.com/2015/04/silk- road-1/)

More articles on the leaky login page:

[http://www.wired.com/2014/09/the-fbi-finally-says-how-it- leg...](http://www.wired.com/2014/09/the-fbi-finally-says-how-it-legally- pinpointed-silk-roads-server/)

[http://krebsonsecurity.com/2014/09/dread-pirate-sunk-by- leak...](http://krebsonsecurity.com/2014/09/dread-pirate-sunk-by-leaky- captcha/)

[http://www.theregister.co.uk/2014/09/08/leaky_captcha_behind...](http://www.theregister.co.uk/2014/09/08/leaky_captcha_behind_fbis_silk_road_rapture/)

<comment><USER3> This conversation shouldn't happen without first talking about "parallel construction".

[https://en.wikipedia.org/wiki/Parallel_construction](https://en.wikipedia.org/wiki/Parallel_construction)

We know they've tapped every fiber there is, in closets and undersea. It would be simple to use timing attacks at that point.

Given that they had the means, and the lack of principles to use those means, why would we believe it was anything else? We don't have to invent absurd scenarios, nor should we believe anyone else's inventions.

</comment></comment></comment><comment><USER4> > Yes, I do run onion services; I run an onion services on every box I have. I > connect to the PC in my house from anywhere in the world through SSH—I > connect to my onion service instead of my house IP. People can see my laptop > accessing Tor but don't know who I am or where I go.

Funny, I do the same thing and it saved me a few times when my router went crazy and stopped port forwarding, but I still had access to it. (And successfully fixed the problem without making a visit to the site...)

</comment><comment><USER5> I wonder if I2P is not becoming a little more attractive than tor.

<comment><USER6> Unfortunately I2P has not had nearly the same amount of research attention.

</comment></comment><comment><USER7> I think that correct definition of this article is "FAQ", not interview. The term "interview" usually implies actual conversation.

<comment><USER8> I disagree; Interviews range from full conversations to simple questions and answers, "FAQ" on the other hand implies many people asking the same questions, not a single interviewer asking them.

<comment><USER9> Q&A might be what the OP meant?</comment></comment></comment>


Gobolinux - the filesystem is the package manager - <AUTHOR> http://www.gobolinux.org/

<comment><USER2> NixOS ( <http://nixos.org/nixos/> ) is quite similar on the face of it, except that it does not make all the symlinks. Its package definition language is purely functional, too!

Gobo looks a bit unmaintained, too :(

<comment><USER3> I like the idea of gobo (I used it for a little while) but the packages they had available just weren't doing it for me. I'm an arch guy, now :-)

</comment></comment><comment><USER4> Though I really like the concept, I'm concerned by package availability (or a lack thereof). It's frustrating to have to take a big detour when developing to circumvent my linux's preferred way of package installation in order to get some newer version of a library.

On the other hand, I've almost just as many headaches with outdated libraries in the current Ubuntu repo (like anything Ruby, which is all for 1.9.1 and older, iirc).

I went with Arch for a while, but missed a lot of the conveniences of Ubuntu. I stick with Ubuntu since of all the distros I've used in 5 years of using Linux, it's given me the least friction when I just want to get stuff done.

<comment><USER5> I use PPAs (personal package archives) in Ubuntu to have a semi-rolling release. My browser, compiler and other select applications are updated daily but the underlying system is stable.

</comment></comment><comment><USER6> Homebrew on OS X uses the same approach to install packages. It works as long as the installed software doesn't have to modify system files (/etc).

</comment><comment><USER7> The idea of having packages installed in different directories is very convenient for development, you often need to install several versions of the same package and don't want to clutter /usr/local (or don't have root permissions)

Some months ago I have written a small tool that automates installing apps in separate directories and then symlink them to a directory in the path. It also supports disabling/reenabling/removing single packages (by removing the symlinks) and has a PIP fork to simplify installation of Python packages (also an "autobuild" for standard configure/make build systems)

It was written for development but actually it became my preferred system to install packages in Mac OSX, packaging systems (fink, macports...) are _terrible_ there.

It's on pypi and doesn't require any installation, if you want to give it a try: <http://pypi.python.org/pypi/bpt/>

<comment><USER8> Doesn't this do roughly the same thing as the Debian alternative system?

EDIT: I should have read your link first. It appears that your system allows for greater isolation and the ability to relocate different versions.

<comment><USER7> Yes, and also everything is contained in a single user directory, a "box". You can have multiple independent boxes.

<comment><USER9> Is this similar to Gnu Stow? Or does it do something significantly different?

<comment><USER7> Stow installs packages in /usr/local, bpt in a directory specified by the user (for example under the home directory) BPT uses the pair (name, version) as install directory, so it is possible to install several versions of the same package and switch between them.

The "boxes" (directories with packages) created with bpt are relocatable, so it is possible to prepare a box with all the applications and their dependencies and deploy it without needing root privileges.

It has first class support for python packages (through PIP) and "autobuild", which is similar to checkinstall. I couldn't find these features anywhere else.

<comment><USER10> > Stow installs packages in /usr/local

No, it doesn't. I've used stow heaps of times in my home directories on various university machines. The common case is for managing /usr/local, but you can ./configure --prefix=$HOME && make && make install prefix=$HOME/stow/foo-3.14 && cd $HOME/stow && stow foo-3.14 without trouble.

</comment></comment></comment></comment></comment></comment><comment><USER11> I'm using Arch now for two reasons. It is surprisingly easy to install and maintain. The documentation and wiki are the real reason behind this. I guess that's the surprise: docs beat guis, at least in linux distros.

Also I can keep a bleeding edge system up to date with out much trouble. I never could figure out how to do this with unbuntu.

I guess there is also a third reason. Arch seems to keep up with haskell developments very well.

<comment><USER12> I use Arch too, but I really don't get what this has to with GoboLinux...

<comment><USER11> No argument. I made the comment for the benefit of distro shoppers. They won't see it as off-topic even if it is.

<comment><USER12> I understand. I just fear that Arch users become another group of overzealous fanbois.

I have already seen the joke "How do you recognize an Arch Linux user? He will tell you" floating around on the web...

<comment><USER11> I consider myself to be an underzealot. I wouldn't recommend it to anyone who doesn't already know how to get in and out of nano or vi.

My main motivation came from noticing the extensive support for haskell packages. I would have been happy to use a debian-based distro, but haskell seems to be too bleeding edge for distros like ubuntu to keep up.

</comment></comment></comment></comment></comment><comment><USER13> Reminds me a lot on NeXT and MacOSX. And I like it.

</comment><comment><USER14> it's a neat idea but why use Gobo instead of other distros? The intro page doesn't really explain its advantages and benefits.

<comment><AUTHOR> <http://www.gobolinux.org/index.php?page=at_a_glance>

The key point is that a package is stored entirely under /Programs/packagename - bash is stored under /Programs/Bash/3.0, and /bin/bash is just a symlink to /Programs/Bash/3.0/bin/bash.

When you want to uninstall bash, just use rm -rf /Programs/Bash/3.0.

They also have some tools which allow you to cleanly install programs _from source_ in this manner, i.e. programs that are not included in the Gobolinux distribution. So regardless of whether Gobo packaged it, all programs are under package management (unlike yum/apt-get/etc).

<comment><USER15> Well apt has tools that help you install it through dpkg and manage it through apt, just not many use it.

What I am wondering is how they solve the dependency problem, like say something depends on bash and you remove bash with rm do you get any warnings or help or just a broken system? (This is more for when it is part of gobo and not installed from source).

<comment><USER16> Removing bash using rm would probably be a bad idea.

Although I think using the filesystem for this purpose is a good idea -- you get parallel-installed versions for free, and it's more reliable and transparent than what you get from rpm -- you're right that just deleting stuff willy nilly won't work. You still need to manage dependencies, and dependency graphs are not easy for humans to keep in our heads.</comment></comment></comment></comment>


Show HN: A template to help you write your web project specs in less than 10mins - <AUTHOR> https://specstemplate.com/ <comment><USER2> I like it! Here's some feedback for you:

1) When deleting a section, it would be nice if you placed the confirmation box closer to the delete button, instead of using the browser's built in confirmation dialogue.

2) The Prestashop logo doesn't work on the project details page: [https://specstemplate.com/specs/6820fc58-b65e-44ce-b2d3-ba27...](https://specstemplate.com/specs/6820fc58-b65e-44ce-b2d3-ba27286c362f)

<comment><AUTHOR> Thanks for the feedback! Will implement both in the next iteration :)</comment></comment>


Customer Tracking at Ralphs Grocery Store - <AUTHOR> https://www.schneier.com/blog/archives/2020/01/customer_tracki.html <comment><USER2> This is a nice analysis of what Ralph's is up to, but they aren't exactly exceptional. The entire purpose of any store's "loyalty program" is to collect as much data on their customers as possible.</comment>


China to build giant buses that cars can drive under - <AUTHOR> http://www.engadget.com/2010/08/02/china-to-build-ginormous-buses-that-cars-can-drive-under-video/ <comment><USER2> Are those really busses or are they trains? This scheme looks cool, until I try to picture what happens during turns. Remember that "large vehicles make large turns." One way to think about it is that "turn radius" of the from wheels is much larger than for the back wheels. It's more complicated than that, but it's the gist.

EDIT: Watching the video now. The "bus" is divided into many sections which need to "snake" around turns. This fact is fudged a lot -- many of the illustrations also show vehicles that do not have joints. Judging from the size of the bending joint sections, the minimum turn radius of the bendable trains looks fairly large.

<comment><USER3> This strikes as feasible, assuming total computerized control of _all_ the vehicles, both the "bus" and the cars trying to drive under it. Humans will be smashing the sides of that bus with frightful regularity, though.

And by the time you have that, there are probably way better ways to deal with traffic than this sort of crazy contraption. Even if this ever becomes practical I have a hard time seeing it ever being the best use of money.

Segmenting the bus enough to give it a safe turning radius will make it seat very few people. (And note I don't say "decent" or "cost-effective", I said _safe_. If cars are driving underneath, the "bus" must also turn _exactly_ like a car.)

Nifty concept, pretty pictures, much less practical than the only-barely- practical-if-that trains that don't have to stop that got posted four or five times a few months ago. But worth noodling around with; I don't fault the designers too hard, I fault the credulous media.

<comment><USER2> _Humans will be smashing the sides of that bus with frightful regularity, though._

I'm pretty sure Houston drivers would be. They can't even deal with light rail on city streets!

<http://www.youtube.com/watch?v=CV2rdGX4JYc>

<comment><USER4> Based on my own observations I take it as a given that people regularly break traffic rules. Car-car smashes happen with frightful regularity too. It isn't a Houston-only issue.

The reasons for this may be carelessness or disregard--reasons don't really matter. The behavior exists and rules/signs don't appear to mitigate very successfully (especially strange signs and irregular rules you don't see anywhere else).

Carelessness and disregard are part of the human condition and why defensive driving is great. It follows the robustness principal of "Be conservative in what you send; be liberal in what you accept."

Unfortunately, the performance envelope of Houston's passenger train precludes defensive driving on its part. It can't be a good street-citizen.

<comment><USER2> Having lived in Houston for 7 years, I'd say we have a much bigger problem with the car drivers not being "a good street-citizen." I wouldn't say it's Houston only, but there is a lot of it here. There's a lot of just plain pinhead disregard for physics and common sense here.

<comment><USER5> I've never been to Houston, but I've been to a lot of US cities, and I've been to China. I find it hard to imagine that the drivers in Houston are worse than the drivers in China.

<comment><USER2> I've heard first hand descriptions of driving in China, Italy, and Pakistan. In Pakistan, they have problems with people obeying stop lights!

This all just supports my point. If Houston drivers are pinheads that feel like they can cut-off a train that out-masses their vehicle by a factor of ten, what are Chinese drivers going to do about these massive tunnel-things going around when they have to drive underneath those things? It's begging for a lot of accidents, I think.

</comment></comment></comment></comment></comment></comment></comment><comment><USER6> Given the nature of traffic in China the one angle they don't show in the video is the one that matters most... what happens when vehicles in front of the bus straddle the lane, blocking it?

They line up neatly coming from the back because they physically have to but anyone who has seen the traffic in China knows that cars will not get out of the way or obey the lane markers and are quite likely to abruptly (even at risk to themselves or their vehicle) cut the thing off from the front in order to squeeze in front.

<comment><USER7> The same way we solve all of life's problems: Giant spinning blades!

Or, y-know, fines. And a bored cop sitting on the top of the giant bus with a crane.

</comment></comment><comment><USER8> Think of it the other way around: cars don't drive underneath, but the _bus drives above the stationary cars_ in the congested metropolis.

<comment><USER9> The congested cars in China aren't neatly stacked in their lanes.

</comment></comment><comment><USER10> Neat idea but it violates the 'kiss' principle on several points.

I'll believe it when I see it, in spite of the fact that 'building will commence soon'.

<comment><USER11> It is simple in a way. It's an alternative to building another deck on top of the road for light rail to run along. Probably cheaper and less devastating to communities that it runs though.

<comment><USER10> Not really, building another deck on a road (assuming that's the right solution for a given topology) is well understood technology wise. Adding a completely new, untried infrastructure for a vehicle class that nobody has any experience with will add unique challenges that may be difficult or even impossible to overcome. In practice, for instance, how would you deal with it if one of these monsters broke down? What will you do when a car has an accident with another car underneath one of them in such a way that you can't move it without further risk to the occupants?

How will the drivers deal with a vehicle that is in their perpetual dead angle ? How will the driver of the 'urban train' see the vehicles he's moving over and make sure that none of them get crushed at intersections in case traffic somehow got blocked?

China has some history of 'grand announcements' which are then not followed up on, and a few that they did follow up on that failed fairly spectacularly. We'll see if this one works out, I'm sceptical but who knows, maybe it will work.

The three gorges dam is also still holding up in spite of lots of nay saying so I'll give them the benefit of the doubt.

</comment></comment></comment><comment><USER12> I don't think that it's such a great idea.

ACCESIBILITY: In crowded cities you need people to get in and out of the bus quickly, meaning lots of doors and very few steps. Also let's not forget wheel chairs. How could an elderly person climb all those steps to get out of the bus? How about someone with a baby in a buggy?

INFRASTRUCTURE: Yes, it's cheaper than a subway, but that's the only advantage. When this bus makes a turn, at least some part of the traffic must be stopped. Cars will crash into the bus without doubt. The bus stops will be expensive to build.

SUGGESTION: Spare two lanes and build a light rail, separated from the traffic by fences solid enough to prevent cars from landing on the rail. Make all intersections with regular traffic at different grades (overpass or underpass). It's a proven technology, no accesibility issues, cheap stations, completely separated from the rest of the traffic (because of this it can become completely automated).

<comment><USER13> Why not just build the light rail over the highway, like they do in Bangkok?

<comment><USER14> I hadn't read about the rail in Bangkok, looks cool:

<http://www.railway-technology.com/projects/bangkok/>

</comment></comment></comment><comment><USER15> I wonder what their turning radius is? How will they turn around at the end of the route (I would imagine probably just switch back like a train). Thanks China for another crazy but awesome idea.

</comment><comment><USER16> It's a cool innovative idea. Now it's the execution, which probably won't be easy. Vehicle design and construction will be different from norm. Road design and regulation will be different. Kudos for coming up with the idea.

</comment><comment><USER17> This looks dangerous. Two lanes of traffic competing for limited space under a moving bus? Imagine what happens when a car underneath hits the side and goes into a spin.

</comment><comment><USER18> If both 'layers' of traffic are moving, not sure this is any better than a double-decker bus. Certainly, it has less route flexibility, if it requires special rail/roadway support.

My hunch is that computer-driven cars are the real transport innovation we should be concentrated on. When a region can go 100%-auto-auto, it will increase road capacity and eliminate congestion, without tearing up roads with massive new (and inflexible) rail construction.

</comment><comment><USER19> There must a transport revolution going on in China. It instantly reminded me of this video:

<http://www.youtube.com/watch?v=p9Ig19gYP9o>

These trains that never stop seem a lot more feasible than the buses. Granted it would require a massive amount of work from an infrastructure perspective but it seems like such a brilliant solution that would make public transport infinitely more appealing.

<comment><USER20> This was posted to HN before. The comments on that were basically, it's been done before, and wasn't economical/safe. Keep in mind, you still have to spend energy to accelerate the cars, and there are a lot of safety issues introduced by the extra complexity.

</comment></comment><comment><USER21> This concept was brought up in one of the Patlabor anime movies, except instead of buses, it was police/fire/ambulance/emergency vehicles that could move over congested traffic to get to an accident scene more quickly.

Kudos to the Chinese for being willing to try it out, but the concept existed at least in 2001(if it was Patlabor 3) or 1993(Patlabor 2)

</comment><comment><USER22> I ride the bus to work most days. A lot of the drivers like to gun the engine when they can and stop quickly. This is annoying in a low-slung bus and would be scary in one with a high center of gravity. Much of the route has old, beautiful trees along it--not much change for them.

</comment><comment><USER23> How is it driven? It looks like it would be a disaster if the bus weaved left or right by a few millionths of an inch.

</comment><comment><USER24> Adds a whole new level of enforcement to the left turn only lane.

</comment><comment><USER25> An excellent idea, maximizing use of the available road space.

</comment><comment><USER26> US to build giant pickup trucks that SUVs can drive under.

</comment><comment><USER27> Odd that all the CGI people in the movie are white.

<comment><USER28> Probably stock models that came with the animation software.

</comment></comment><comment><USER29> Maybe one day, say the year 3000 cars will be driving under cars, under cars, under cars. We can only go up to the skies.

<comment><USER29> I guess hackers don't like predictions so much. Who is to say that such wont be the time in one thousand years. Are we going to dig down to earth instead, rather than find more effective ways to use the very finite space on earth.

They did not start building high buildings for no reason. Why would the solution be any different if a solution one day our roads needed?

</comment></comment><comment><USER30> this is so beyond cool...</comment>


Under Threat, Women Bond, Men Withdraw - <AUTHOR> http://www.scientificamerican.com/article.cfm?id=under-threat-women-bond

<comment><USER2> The article doesn't suggest higher-level reasons why men withdraw, but my guess would be because they tend to become more focused on a task, at the cost of human interaction. Maybe this is a result of making hard choices in leadership/hunting scenarios - if your hunting buddies are injured by a sabretooth tiger, worrying about them is probably the worst possible short- term reaction because then the sabretooth will get you, too. Kill the beast first and then save your buddies, or everyone dies.

Losing some ability to empathize would help one make hard decisions that benefit the group at the expense of the few. That could be a bad thing if "benefitting the group" becomes crossed with an arbitrary goal, and "the few" becomes "those not in power", but that's well beyond the scope of this topic.

<comment><USER2> I wonder if actual anthropologists hate when unqualified people make wild guesses like the one I just made above...can anyone answer?

<comment><USER3> I'd argue that the act of making such guesses, ideally based on some education and insight, are at the heart of science. A professional anthropologist may or may not have any more education in the relevant areas, but I can imagine lots of cases where they might not have as much insight or creativity or natural genius as some particular non-anthropologist.

</comment></comment></comment><comment><AUTHOR> I don't know how true the whole article is, but I definitely get anti-social under stress. Worst part of being a startup founder, if you ask me.</comment>


AWS Nightmare: Leaked Access Keys Result in a $6,000 Bill Overnight - <AUTHOR> http://wptavern.com/ryan-hellyers-aws-nightmare-leaked-access-keys-result-in-a-6000-bill-overnight

<comment><USER2> Aren't there caps on AWS preventing such type of spikes without user intervention? Like with a credit card where I will get a call if I all of a sudden make a huge purchase.

</comment><comment><USER3> i doubt that wp creates `wp-config.php.save` but the said person himself.

while i feel sorry for him but it's probably his fault.

<comment><USER4> His MAJOR f-up was using his main account credentials (completely unrestricted access) instead of creating a second set of IAM credentials policy-restricted only to S3 access.</comment></comment>


Amazon Doesn't Consider the Race of Its Customers. Should It? - <AUTHOR> http://www.bloomberg.com/graphics/2016-amazon-same-day/ <comment><USER2> Pretty sensationalist article. The important parts are buried about halfway through:

> Amazon, he says, has a "radical sensitivity" to any suggestion that > neighborhoods are being singled out by race. "Demographics play no role in > it. Zero."

> Amazon says its plan is to focus its same-day service on ZIP codes where > there's a high concentration of Prime members

The areas Amazon does same-day delivery are likely just driven by pure numbers and algorithms -- larger order counts/sums will result in a higher chance of same-day delivery to a certain area and low numbers for an area means it will get it later.

</comment><comment><USER3> This may be correlation, but their own data doesn't look like causation.

For example, they talk about the "hole" in Boston with blacks carved out.

They don't talk about the hole in Dallas with whites carved out. In Dallas, compare the depiction of the hole on left vs. right. On the right they delete the whites (green dots) so it looks like nobody's in the hole. On the left, the hole is almost solid green, clearly invalidating the thesis.

They interview blacks in the Boston hole, but not whites in the Dallas hole, and nobody in L.A. where a higher % of blacks are served by same day Prime than whites.

I'm comfortable with a combination of two straightforward factors: where are Prime subscribers, and, where are the warehouses and package delivery hubs?

Prime and FedEx both likely have correlation to % of folks happy to pay $23 for a letter today vs $0.50 next week, and where you can put a warehouse and shipping hub to best logistically serve those folks, with Prime having a bias towards residential density and FedEx a bias towards commercial.

<comment><USER4> Except the "hole" in Dallas is not Dallas. It's Highland Park and University Park, Texas, two completely separately governed areas from the City of Dallas. But keep that tin foil hat handy.

</comment></comment><comment><USER5> There's two things the article doesn't consider enough which might be important:

1\. Road access

2\. Crime

The first is a lesser concern but does affect deliveries. An area with easy access to highways and truck-worthy roads is easier to do economical deliveries in. Some areas have roads that can't take trucks due to clearance, quality of road itself, weight limits on wooden bridges, stupid GPS routes, and so on. Fixing that stuff up helps.

The second, crime, is a major concern. This article starts being less shocking when you replace "mostly black or latino" with "high chance of being robbed, raped, or murdered." I cant speak to all their examples but many jump right out. The blacks I know from Chicago say the South-side is "the hood all over it." All of them have said that. Then the Bronx shows up of course. Also parts of Atlanta where crime is highest and a few thugs I had the displeasure of meeting. Kicked their ass back to Georgia. All areas where a company vehicle and/or driver is likely to get robbed with the driver maybe being straight-up _murdered_. And for almost no money since it's low-income areas.

 _That_ might factor into their analysis. Wisely so as almost nobody in the murder capital I live in wants to deliver to the hood even though plenty do (eg Dominos pizza or Jimmy Johns) because they need a job. A number of those report the occasional gun to their head to get a free product with manager blacklisting that house. Stories like that go around business to business, driver to driver. A truck stolen for $80,000 losses does too. Compare it to the white neighborhoods where people just don't get robbed at gunpoint delivering a pizza. Rarely if ever.

It's perfectly reasonable to refuse to deliver to high-crime areas until they get their shit under control. Neighborhoods need to start standing up for their own and ejecting people like that. Enough of that happening will let the companies differentiate more between safe and unsafe neighborhoods that are low-income. Then, companies might come back to them. Meanwhile, companies reduce their losses greatly by not showing up.

Note: I've turned down multiple, high-paying jobs because I'd have to waste too much money on security or insurance. Because they were in the hood. And, yes, there's articles about those same locations just like this talking about how avoidance happens because they're black or Latino. No, it's because we'd rather not die, buy another smartphone, or go to the DMV again cuz assholes take the license. Stuff that doesn't happen in poor, mostly-white parts of my area. They just steal gas, burglarize empty houses, sell weed/meth, and so on. Stuff that won't kill me outside the occasional thug solo or pair. 2nd Amendment works fine for that as it's not 15-20 person gang all at once like in the hoods.

</comment><comment><USER6> Quick! To the Betteridge-mobile!</comment>


Postgres Randomized Primary Keys (2017) - <AUTHOR> https://medium.com/@emerson_lackey/postgres-randomized-primary-keys-123cb8fcdeaf <comment><USER2> What's wrong with UUIDs, which seem to meet all the stated requirements? The article discusses them without saying why.</comment>


Show HN: This year resolution's first open-source project: PHP-Spellchecker - <AUTHOR> https://github.com/tigitz/php-spellchecker <comment><AUTHOR> Hello HN community,

You've been an immense part of my career without knowing it. You're the reason why I'm still passionate about programming and can live comfortably as a senior developer. I'm having fun sharing all the online knowledge you taught me with my not-so-passionate coworkers. They appreciate it and it is all thanks to you. I keep believing PHP ecosystem is going strong and it has a bright future ahead.

I would like to take the time to give back through my modest contribution.

I identified an unfulfilled need while I was being frustrated of not finding a reliable (at least according to my standards) library to do spellchecking easily from PHP.

I decided it would be a good candidate to finally achieved my goal. I though it would be a matter of 3-4 weeks of work.

It took me 11 months, not of actual work though. But it was hard. I felt alone, overwhelmed, being too perfectionist, not confident on the real world usage and at some point real life caught up.

Eventually I made the last final push at the end of this year, as I feel I reached a state I'm proud of I present it to you.

On a bright side, I also learned a freakin' ton !

* Travis CI * docker / docker-compose * Makefile * Packagist publishing * Documentation (I've built my own generator !) * Github Pages * Spellcheckers algorithms and features, * and so much more.

I hope you'll find it good enough to star it and give it visibility, that sounds cheesy writing it and I would probably ignore it myself if I read it in a post but now that I'm on the other side... I understand how much it can help the author and the community if it's deserved.

Happy new year everyone.

</comment><comment><USER2> I'm not a PHP dev, so I can't say much of the technical side of the project. What I think looks amazing is the level of detail to the documentation and readme. Congrats!</comment>