GE's new turbofan engine is as wide as a Boeing 737 fuselage - <AUTHOR> https://www.wired.com/2017/05/ge-turbofan-huge-jet-engine/ <comment><USER2> So, the GE9x is a super-high-bypass turbofan that makes unusually heavy use of composites and additive manufacturing techniques, and gains about 10.5 inches in fan diameter (and might shed some pounds) over the GE90 parent design currently used on most 777s. I don't know where Wired is getting the 148in figure - duct or nacelle diameter, maybe. It's right for a 737's fuselage, so maybe the writer took a metaphorical statement as literal. But that's not an unusual size for an engine on a 777, and if you've seen one of these big widebody twins alongside its narrowbody elder cousin - or, better yet, superimposed, as in [1] - you know that it's not really a surprise to hear that the engines of the former are comparable in diameter to the fuselage of the latter.

Wired's really gone down the clickbait hole in the last few years - not that it was ever as substantial as it liked to make itself out, but still disappointing to see.

[1] [http://imgproc.airliners.net/photos/airliners/2/0/5/0881502....](http://imgproc.airliners.net/photos/airliners/2/0/5/0881502.jpg?v=v40)

<comment><USER3> GE9x has a 133in fan [0] compared to 128in fan for a GE90-110 series. 148in is the Nacelle width.

[0] [https://en.wikipedia.org/wiki/General_Electric_GE90#GE9X](https://en.wikipedia.org/wiki/General_Electric_GE90#GE9X)

<comment><USER2> Fair point. I was looking at the spec for earlier versions of the same engine, which used a fan five inches narrower.

</comment></comment></comment><comment><USER4> I watched a documentary on GE not that long ago, it wasn't anything new, probably 10 year old or so. Anyway, one of the things that really stood out to me was that GE has a command center where they are able to monitor the performance of all their engines in near real time, as they are flying throughout the world. All of their (newer, I assume) engines have build in data links that call home to the control center. This obviously allows them to see issues really quickly and solve problems nearly before they happen.

It just struck me as one of those things that makes perfect sense, but I never really thought that much about it before seeing it.

I'm surprised I haven't seen more of this in automobiles these days, (maybe Tesla?) but I can't imagine it will be long before it's common place. There would of course be privacy concerns, but it's something that I could live with in order prevent break downs or things of that nature.

<comment><USER5> Rolls Royce does this too for their aircraft engines.

The big difference vs automobiles is that most airlines buy their planes but only lease the engines. GE and Rolls Royce monitor the engines at all times because the own them and are responsible for them at all times.

<comment><USER6> Known as "power by the hour", or maybe TaaS ("thrust as a service") would be more appropriate for HN

</comment></comment></comment><comment><USER7> It's embarrassing that Boeing is still making 737 variants. The first flight of a 737 was over 50 years ago. Yes, most of the systems have been upgraded, but it still has the same small fuselage diameter. Patrick Smith, who's flown both and writes "Ask the Pilot", complains that Boeing discontinued the 757 and continued the 737 instead of developing something better. [1] From his perspective, the 737 is underpowered, has too-high takeoff and landing speeds, and doesn't fly as well as the more modern aircraft. Boeing says they need to make at least 1500 aircraft of a new model to break even, and don't think they can sell that many of something in 737 size.

[1] [http://www.askthepilot.com/757-v-737/](http://www.askthepilot.com/757-v-737/)

<comment><USER8> It's embarrassing that manufacturers are still making computers with silicon chips in them. The first silicon chip was over 50 years ago. Yes, most of the components and surrounding systems have been upgraded, but it still has the same basic material.

(etc., etc. -- "old" does not mean "bad"; the 757 is a perennial example of people claiming to want something they don't really want; and the 737 is a proven, successful design, so there's absolutely _no_ "embarrassment" in the fact that it's still being manufactured and flown)

<comment><USER9> > _It 's embarrassing that manufacturers are still making computers with > silicon chips in them._

You might even zoom out a bit more and go with, "It's embarrassing that manufacturers are still making ATX cases". Just as ATX cases have been able to accommodate several generations of computing, modern 737s are effectively different aircraft than early 737s even though they share common properties.

</comment></comment></comment><comment><USER10> Interesting to see 3-D printing being used in a high-end precision industrial application like this one. Cobalt-chrome sintered powder, neat!

</comment><comment><USER11> Here are some actual numbers [http://m.aviationweek.com/blog/engine-fan- diameters-creeping...](http://m.aviationweek.com/blog/engine-fan-diameters- creeping-past-fuselage-widths)

</comment><comment><USER12> Some pics:

[http://www.newequipment.com/sites/newequipment.com/files/ge9...](http://www.newequipment.com/sites/newequipment.com/files/ge9x-stats- graphic.jpg)

[https://www.aviationcv.com/aviation-blog/2016/worlds- biggest...](https://www.aviationcv.com/aviation-blog/2016/worlds-biggest-jet- engine-first-testing)

</comment><comment><USER13> When I first flew the 777 about seven years ago I was totally awestruck by the size of the engines.

I flew with Qatar Airways, and in Doha they had a mobile staircase plus a bus, and with business class the entrance was just a few meters ahead of the engine. Or at at least it felt that way.

Seems like the diameter of the 777X engine is just a tiny bit larger than the old 777 engine: 339 cm vs 325 cm.

<comment><USER14> From my old flying days, I remember everyone talking about how the engine nacelles on the original model 777's were almost exactly the same diameter as the fuselage barrel on a 737.

That one fact really brought home to me what a huge beast the 777 was...

<comment><USER14> Another standout from my chat with the engineers that day, was the fact that each individual fan blade on the 777 engine was worth far more than my car... I think it was almost the equivalent cost of 24 Porsches spinning around that initial stage of the engine - let alone all the compressor and turbine stage blades behind that!

</comment></comment></comment><comment><USER15> This is a very impressive piece of technology. Coupled with a 777-9, a 2 engine plane can have nearly the same number of passengers as the 4 engine 747.

A GE exec told me that 80% of this technology makes up the electric power generators and that one of these units can power 300,000 homes.

<comment><USER16> The two-engine A330 has been carrying the same number of passengers as the four-engine A340 for decades :).

</comment></comment><comment><USER17> Great that they make such fancy and efficient engines, but can we please do something about the ~20% fuel waste during taxiing?

[http://www.sciencedirect.com/science/article/pii/S1361920911...](http://www.sciencedirect.com/science/article/pii/S1361920911000198)

</comment><comment><USER18> The fan is just a propeller in a shroud, and large diameter propellers are commonplace on large aircraft.

</comment><comment><USER19> This related video shows the inner workings and assembly of the engine. Truly amazing feat of engineering: [https://youtu.be/DMqRsBOihIM](https://youtu.be/DMqRsBOihIM)

<comment><USER20> They locked that poor guy in there at 1:41.

</comment></comment><comment><USER21> Misleading title. Boeing doesn't make aircraft engines. This is a GE Aviation design.

Which happens to first see service in the Boeing 777X, but there's no reason to assume it couldn't go into other airframes or even other manufacturer's aircraft.

To attribute it to Boeing like that makes no rational sense. More information on GE's site:

[https://www.geaviation.com/commercial/engines/ge9x-commercia...](https://www.geaviation.com/commercial/engines/ge9x-commercial- aircraft-engine)

<comment><USER22> Reading NYT coverage of any subject you know about is like having a toddler explain to you what she did today.

<comment><USER23> The NYT has done reasonably, if not perfectly, on surveillance and cryptography topics I know a great deal about. It's substantially better than The Guardian. Also: the quality of the NYT's _reporting_ is far better than any other news outlet: an NYT story is likely to have better sourcing than any competing story.

<comment><USER15> As a long-time NYT reader, I can't speak to whether they are better than other new sources, but in areas that I know well, they generally get it wrong, at times leaving vital information out. At other times, they have done well, when they have jouralnsts who are also specialist write articles. For example, some of the articles on nuclear power are co-written by a PhD in physics, but oddly it seems like he is not a contributor on all articles about nuclear power.

Many of the medical articles are not full of complete information or an understanding of healthcare and public health.

Also, many stories on Israel are lacking context and completeness perhaps in some attempts to be "balanced." For example, the NYT does not discuss that the current Fatah Palestinian administration names childrens schools and streets after terrorists. They don't bring up enough that Fatah pays money to the families of terrorists, both dead and those in Israeli jails. That money they use to pay for terrorists comes from American taxpayers.

<comment><USER23> Can you provide an example of a story in which those details are relevant?

<comment><USER15> Well, for example, many claim that Israel is not ready for peace, but the reality is that since Fatah is still naming children's schoolhouses and streets after terrorists (including the mastermind of the Munich Olympics Massacre (see Spielberg's Munich) and that they are using US funds to pay for families of terrorists in prison they clearly back terror instead of being against it. Until the Palestinians demonstrate their steadfastness against terror, there can be no peace. Also American don't want their tax money funding terrorists.

<comment><USER23> That's a reason why it's important to you that the Palestinians not openly support terrorism. But that's not what I'm asking. I'm asking: can you show us an example of an NYT story about the conflict (or any other aspect of Palestine/Israeli relations) in which those details were needed but absent? It would help to have an idea of what those absent details do to a specific story.</comment></comment></comment></comment></comment></comment></comment>


An open source Google Reader replacement: Sismics Reader - <AUTHOR> http://www.sismics.com/reader/

<comment><USER2> An RSS reader without synchronization is not a Google Reader replacement.

<comment><USER3> Someone suggested using TinyTinyRSS + Liferea.

<comment><USER4> I wasn't able to get Liferea to work with TTRSS, and I really tried :-/. Therefor I wrote one myself but it has only the possibility to show posts, no list or anything because I never used that [http://jabs.nu/feedthemonkey](http://jabs.nu/feedthemonkey) I assume most of the people will not be comfortable with it.

<comment><USER3> Interesting. Did you try to write a mobile client for Nemo or Sailfish as well?

<comment><USER4> No not really, actually I didn't even know wat Nemo or Sailfish was before you posted it and I searched for it.

<comment><USER3> They are Qt centric, so I thought you've heard of them, since you work on Qt based client.

* [https://wiki.merproject.org/wiki/Nemo](https://wiki.merproject.org/wiki/Nemo)

* [https://sailfishos.org/](https://sailfishos.org/)

</comment></comment></comment></comment></comment></comment><comment><USER5> An RSS reader that won't use the "j" and "K" keys to iterate forward and backwards through the articles is useless to me.

<comment><USER6> Right? To me that's the only reason I stayed with Google for so long, key commands to quickly jump through several hundred items.

</comment></comment><comment><USER7> Sorry about posting here. Couldn't find a bug report link on your website:

wheezy/sid (Really Mint Linux but whatever)

openjdk-7-jre:i386

$ sudo dpkg -i reader-1.1.1.deb

dpkg: error processing reader-1.1.1.deb (--install):

parsing file '/var/lib/dpkg/tmp.ci/control' near line 2 package 'reader':

error in Version string '${reader.version}': version number does not start with digit

Errors were encountered while processing: reader-1.1.1.deb

Hope that helps.

<comment><USER8> Thank you, I have just fix the issue on Debian packaging

</comment></comment><comment><USER9> Seems good, I like it. I might try it later on my server (hopefully it's not too heavy on the system, since I'm going to try it in a small vps).

But it's still another reader that I'll probably not use. Why? Because since there isn't an open standard for RSS reader I can't use it with the client I want.

I'm not saying it's your fault, as it sure isn't. But it's sad that we didn't learn this from the death of Google Reader. There were some talk about creating an open standard right after it's death, but nothing major came out of it.

This is also why I'm still using Google Reader, because every RSS reader out of there doesn't have either a mobile client or a website that I like. If there were an open standard, I could use the mobile client I want, the desktop client I want, and rely on the backend for synchronization and reading on computer without a desktop client.

<comment><USER8> This is true there isn't a standard for RSS feeds synchronizer, but Sismics Reader provide an open JSON API, so you can write whatever client you want, on any platform you prefer

<comment><USER9> This is great, but every developer has to include your API to get it's app working with your service. And he has to do it for every service that he want to support (Feedly, FeedBin, Feever, NewsBlur...).

My rant was not about Sismics not providing an API, but the lack of a standard open API for RSS readers. Beside that, Sismics seems pretty great.

</comment></comment></comment><comment><USER10> Looks nice, just ran the installer on my Windows machine and besides needing 3 restarts for it to finally work, it is too buggy to use.

Importing my feeds works for 5 of them for a short while, after getting the items for the 5th feed it reverts to thinking I have no feeds at all.

<comment><USER8> Hi, I'm one of the 2 developers, can you add an issue on GitHub and join your XML, so we can fix this?

<comment><USER10> Done, should have done it instantly, sorry for that :)

</comment></comment></comment><comment><USER11> Looks good, and I like the mobile web view. Key missing feature for me: oldest-first view.

[Edit]: Also, keyboard shortcuts (most important for me: jk for next/previous).

<comment><USER8> Keyboard shortcuts should be in the next release (there is an issue about it on GitHub)

</comment></comment><comment><USER12> This looks pretty promising. Judging from the demo, they have the UI close enough. They need to offer it as a service, though. I like that I have the freedom to run my own server, but I really don't want to have to bother in practice.

<comment><USER11> I agree. This — service plus open source — is the model for my Google Reader replacement of choice, FeedHQ [1].

[1]: [http://feedhq.org/](http://feedhq.org/)

<comment><USER13> What is it with every new site developed by HN:ers. No screenshots and required signup to learn more.

<comment><USER11> Here are a couple really quick screenshots. Let me know if there's anything else you'd like to see.

Unread view, one unread post: [https://dl.dropboxusercontent.com/u/611024/feedhq/Screen%20S...](https://dl.dropboxusercontent.com/u/611024/feedhq/Screen%20Shot%202013-06-26%20at%201.28.42%20PM.png)

Post view: [https://dl.dropboxusercontent.com/u/611024/feedhq/Screen%20S...](https://dl.dropboxusercontent.com/u/611024/feedhq/Screen%20Shot%202013-06-26%20at%201.28.50%20PM.png)

[edit: moved files in my dropbox]

</comment></comment></comment></comment><comment><USER14> I like the decisions so far! On a pure style/preference note, I prefer content over chrome to an almost absurd degree - the margins around the individual posts could be tighter maybe?

<comment><USER8> Sure, there is a theming system, so you can fully customize the CSS

</comment></comment><comment><USER4> A Google Reader replacement for me is some sync-server with which I can sync read/unread between a native feed reader on my iPhone, my ThinkPad, my Android tablet and my iMac.

<comment><USER15> With all the cloud DBs available... one would think you could simply target one of them as a platform (say mongodb) and that you could define a set of collections/tables/account to use. You could get quite a bit of data in a free account level with couchbase or mongolab. You wouldn't even need to store the full article, just the feeds, urls, dtm and read status... you could do more, but it could work.

For that matter, one could come up with such a "MyData" system that works with the DropBox API or something similar.

<comment><USER4> I would like just a protocol for which I or basically anyone could implement a server and a client, kind of like SMTP and IMAP for email (but as a REST service or something easier)

</comment></comment></comment><comment><USER16> Installed on Windows. OK. Presents a login prompt. Accepts no username that exists on the system.

/uninstall

</comment><comment><USER17> This is awesome. To those listing the faults: It's on github. Fork it, fix it, push it, pull (request) it.

</comment><comment><USER18> How is this a desktop client and mobile at the same time?

<comment><USER19> Good old Java! Though I personally would never want what is suppose to be a slim low memory footprint application (reading text) to be ran by Java. But that's more of a personal objection, and has nothing to do with the actual product.

<comment><USER18> But where does the feeds reside, local or remote?

<comment><USER8> The feeds are remotely synchronized on the server, so you will see the same since whatever your client is (mobile or desktop)

<comment><USER18> Okay interesting. But it currently doesn't seem to have all the bells and whistles for a local or a web client. Something tells me my memory usage will shot up if I attempt to import thousands of feeds into it. Besides, the fetching doesn't appear to be near the real-time (HN rss it pulled in for me, were at least an hour or more delayed).

Anyways, my installation on the windows went well. For now I'm back to testing InoReader.</comment></comment></comment></comment></comment>


Damn Cool Algorithms: Spatial indexing with Quadtrees and Hilbert Curves - <AUTHOR> http://blog.notdot.net/2009/11/Damn-Cool-Algorithms-Spatial-indexing-with-Quadtrees-and-Hilbert-Curves

<comment><USER2> Addenda & thoughts since I do a lot of work along similar lines:

It's probably not a bad idea to have the option of a spatial index at the leaves of a geohash, as the geohash is necessarily of limited precision and will behave badly if someone inserts 100k points all within a 1x1 foot area. ;) (This is equivalent, roughly, to a plain quadtree only with the first N levels of the tree pre-calculated and cached locally.)

I'm guessing the riddle at the end ("Does it remind you of anything?") would be gray code.

Quad-trees can be used for polygons, although they are less than ideal, by storing a list of polygons for each quad. If a quad is entirely contained by the polygon, add the polygon to its list; if a quad is part in and part out of the polygon, add it to its list if length(poly-list) < heuristic_value; otherwise split the quad and redistribute its list among its leaves. (The same arrangement can be used for line segments only, too.) The "query for a region" image shows how this would work, just change the caption to "insert a region." ;)

A reference for this type of index, which is called a PMR-quadtree: <http://www.cs.umd.edu/~hjs/pubs/NelsSIGG86.pdf>

Another good option for points is a KD-tree. You can't turn it into a hash, at least not straightforwardly, but it gives you some nice queries like n-nearest-neighbours, and can be done with as many dimensions as you like rather than just two. (Example use: accelerating the k-means clustering of big multivariate datasets.)

<comment><USER3> Quadtrees are actually actively used for spatially indexing polygons (in shapefiles) by the OGR tools (part of the GDAL package) and MapServer. Quadtrees work quite well in MapServer because it's primary use case is as a read-only renderer of shapefiles. In this scenario, rebuilding the index from scratch each time you make a change is trivial.

</comment></comment><comment><USER4> This is a great write-up.

For n-dimensional Hilbert curves check out <http://www.tiac.net/~sw/2008/10/Hilbert/>

</comment><comment><USER5> That was a good explanation to calculating the index of a point on the Hilbert curve - I had been wondering how that was done myself. I'm going to have to sit down and implement one of these someday.

Other than the quadtree, the Hilbert curve can be used to optimize the r-tree as well: <http://en.wikipedia.org/wiki/Hilbert_R-tree> .

</comment><comment><USER6> You may be interested in my more detailed writeup of morton codes here that was briefly mentioned in this article. It also comes with Python code.

<http://www.codexon.com/posts/morton-codes>

</comment><comment><USER7> Very interesting stuff. Our project has been required to work with the ESRI ArcObjects stuff for the past 4 years and I've been dying to get inside of their algorithms. Thanks for resparking my curiosity.

<comment><USER2> ESRI ArcObjects under the hood:

       if (random()) { crash(); }
       else return UndefinedError;

Tongue in cheek, of course, and they've gotten noticeably better since 4 years ago. (I've been working with ArcObjects since their 8.3 release... _shudder_.)

If you're interested in how they implement vector operations:

       - http://www.vividsolutions.com/jts/main.htm
       - http://trac.osgeo.org/geos/

As far as raster operations go, I think that GRASS does all they do, plus more. All of the above are nice open-source implementations so you can go as deep as you'd like. ;)

p.s. Most of the algorithms ESRI (and similar) use might not be spelled out in blog posts, but they certainly are in textbooks. ;)

p.p.s. Out of curiosity, what have you been working on? ESRI tech is about as anti-startup as one can imagine. It's like using Oracle for your startup's database.

<comment><USER7> Heh, I've been using ESRI since 9.0. Well, to be honest it's required by the contract. I joined when it got bought out.

</comment></comment></comment><comment><USER8> Interesting. I've been thinking about the 'Small World' problem for the Facebook puzzles and came up with the quadtree concept, but I never even imagined something like the geohash/Hilbert curve.

</comment><comment><USER9> FTA: _the next part of our position is 1, and the square we should consult next is the third one._

Doesn't he mean the second one (again)?

This is a good article, but he really should have added an 8x8 illustration and/or mentioned his coordinates start at (0,0) in the upper left. And maybe picked a different point so the example doesn't end up going from the first square to the second to (I believe incorrectly) the third.</comment>


Ask HN: What are your greatest method for learning coding? - <AUTHOR> I am noob and 28 years old. I don't want to waste my time. <comment><USER2> Build a nethack/rogue clone. Works every time, for any language.

<comment><AUTHOR> What if i publish these clone projects live?

<comment><USER2> what if?

</comment></comment></comment><comment><USER3> Side projects.

<comment><AUTHOR> Any idea for side projects?

<comment><USER4> Any kind of thing that you can apply to your personal life, or a family member or friend. Something you care enough about that you'll get excited of doing it.

Off the top of my head, a tool for measuring your favorite sport or activity, for example (say, a website that sends you info about your team's schedule or scores).

Or something for your schedule. Or a weight tracker. Something to organize a collection (music, movies, whatever).</comment></comment></comment>


Every character has a story: U+213a (rotated Q) (2005) - <AUTHOR> https://web.archive.org/web/20060909235709/http://blogs.msdn.com/michkap/archive/2005/01/10/349769.aspx <comment><USER2> Per the article, U+213a ('℺') is part of ISO 5426-2:

> _ISO 5426-2 is a second part to ISO 5426, published in 1996.[4] It specifies > a set of 70 characters, some of which do not exist in Unicode. Michael > Everson proposed the missing characters in Unicode 3.0, but some were > postponed for further study. Later, new evidence was found, and more was > encoded. P with belt is probably an error for P with flourish.[5]_

* [https://en.wikipedia.org/wiki/ISO_5426](https://en.wikipedia.org/wiki/ISO_5426)

</comment><comment><USER3> I am not seeing in the article what the rotated Q is used for: what language(s), what phonetic value, etc.

Found this: [https://en.m.wiktionary.org/wiki/%E2%84%BA](https://en.m.wiktionary.org/wiki/%E2%84%BA)

> Used by publishers as a signature mark on the bindings of printed books

I don't think I am familiar with this use.

<comment><USER4> It's not a phonetic letter; it's a symbol.

The real short of it is that it's a character that existed in another character set, and its role in that character set appears to be limited to "minor printing mark," the sort of role that would cause it to be rejected if someone proposed it as a Unicode character de novo.

<comment><USER5> > The real short of it is that it's a character that existed in another > character set, and its role in that character set appears to be limited to > "minor printing mark,"

Not really. The _printing mark itself_ wasn't a "character" in any character set until Unicode. It was probably a custom SVG-like shape that could be plopped into the margin of the document in desktop-publishing programs; sort of like drawing any other arbitrary vector shape (e.g. a 13-agon.) In specialized desktop-publishing programs (e.g. musical-score "engraving" programs), all sorts of these custom vector-shape symbols come with the system for placement onto the document; but—until very recently†—these weren't "text" in any sense, just shapes.

† [https://blog.dorico.com/2013/05/introducing-bravura-music- fo...](https://blog.dorico.com/2013/05/introducing-bravura-music-font/)

What _was_ a character in a character set (ISO 5426-2) was a sort of "reference to said printing mark" or "exemplar of said printing mark", used once in a standards document to give examples of how printing marks are used. Note the difference: the printing mark _itself_ is an arbitrarily-complex and varied shape that different desktop-publishing programs might render in all sorts of ways. The "reference to the printing mark" is one mark that appears in the standards document, one way. (Picture the difference between an actual calligraphic flourish separating passages of text, and a Unicode fleuron/heart-bullet. One is not the proper encoding of the other! The former is a _shape_ , not a character per se. The latter _is_ a character: it's a standard shape-thing with a standard meaning, that _communicates_ meaning, and is considered "part of" the text.)

Unicode's mission statement is essentially to offer an encoding for the set of all _characters_ needed to losslessly re-encode all document-corpuses (corpii?) of historical importance, such that those corpuses may be _re- encoded_ into Unicode for archival purposes, with the Unicode standard then acting as the record-keeper of the semantic meaning of the characters used in those documents. Without this work, over time we'd lose the semantic meanings of those _encoded characters_ , as the original living systems that represented the encoding began to rot/disappear. We'd just be left with opaque bytes in the middle of a document that we'd have to guess at the meaning at.

The printing mark, as used for its intended purpose, doesn't meet Unicode's mission statement, because nobody's encoding it _into_ a (preserved) document, only "drawing" it on page-edges before trimming them off. It's not "text" per se. It doesn't appear in any electronic stream-of-text in need of archival preservation. It exists only in the same way an image embedded in a Word document exists: as self-contained data interpretable by the document- publishing system, an "add-on" on top of the text, but without the meaning of the text _depending on_ the image. The document-publishing system "brings together" a text source, and other data, to create a final "layout" that is more than just text per se. The _text source_ , not the final layout, is what Unicode is concerned about.

But the "exemplar of the printing mark" ended up in a _standard_ about document binding. And _that_ glyph _is_ "text", in the same sense that an emoji is text — i.e. it's part of the corpus that Unicode seeks to preserve, in order to preserve the meaning of the text surrounding it. So it must treat the mark _there_ as a character.

(Yes, this means that if a text of historical importance has some odd squiggle in the middle of it — and it then talks about the squiggle — that squiggle will inevitably become part of Unicode. That doesn't imply that a visual for the glyph will be drawn by every font artist, though! Just that Unicode will retain a codepoint defining it in the standard, to _document_ the meaning of the glyph as it appears in that one archived document. It'll likely appear as a replacement-box character, but people can go look up in the standard what that particular replacement-box character means, and that's all a historian needs.)

<comment><USER4> > It likely wasn't a "character" in any character set until Unicode.

The article expressly states:

> The proximate cause for the encoding of this character was the need to > provide roundtrip mapping for encoded characters in ISO 5426-2:1996

What is ISO 5426-2, if not a character set?

<comment><USER5> You misunderstand. ISO 5426-2 is a standard specifying the encoding previously used for the text of the _standard_ ; it isn't the encoding used by the desktop-publishing programs themselves that said standard refers to/affects. (After all, the standard is only tangentially "about" desktop-publishing.)

In the context of the standards document and its accompanying encoding, yes, sideways-Q — the exemplar of the mark — is already a defined character; and so Unicode could just adopt it directly from that source character-set.

But my point was twofold:

1\. in the _source desktop-publishing files_ that the standard _documents_ , sideways-Q _isn't_ a character. It's an embeddable shape. This shape is the 'reality' to which the character in the standard is a reference. Like the difference between a real floppy disk, and the floppy-disk emoji. Making it out to be one would be like encoding a game of hangman drawn on a page as a standard "hangman glyph." Not the same! Loses meaning!

2\. Even if the standards document _didn't_ have its own character set where sideways-Q was defined as a character, but instead just took a particular desktop-publishing program's sideways-Q shape and plopped it inline into the text — the fact that the text _refers to the mark, requiring you to be able to see the rendering of the glyph to know what it was talking about_ means that _that_ "sideways-Q exemplar" would inevitably become a Unicode codepoint, in order to encode this document successfully. (In fact, if the standards document were entirely-analogue, e.g. typewritten; and the sideways-Q were drawn onto the page after the fact; then it'd _still_ make it into Unicode in the process of digitizing the work.)

<comment><USER6> Okay, so I think we agree that ISO 5426-2 is a character set... are you saying that it's a character set invented solely to encode its own standard document, or some predecessor standard? Or you're possibly saying that it was only included in Unicode to facilitate representing the ISO 5426-2 standard document as Unicode?

Do you have some particular knowledge/reason for saying so? Other than your comments I can't find any evidence to this effect... maybe I'm simply misunderstanding you. I don't see anything that leads me to believe this was the rationale behind either the creation of the original standard or its inclusion in Unicode.

The sideways Q specifically, like most of this particular set, seems to originate from a British Library internal character set, was included in the earlier 5426-2 set, and from there into Unicode, with the primary interest throughout focusing on bibliographic records, i.e., MARC.

The bit about the difference between the character and the shape/glyph is fine as far as it goes (and does matter here as these older standards didn't really follow that separation) but is similarly true for all of Unicode.

</comment></comment></comment></comment></comment></comment><comment><USER7> IIUC the original was moved (aka erased) in a big reorganization of the blogs of Microsoft. I think this is the new version hosted by the author [http://archives.miloush.net/michkap/archive/2005/01/10/34976...](http://archives.miloush.net/michkap/archive/2005/01/10/349769.html)

<comment><USER8> No, his blog was deleted when they fired him (I don't remember the details). Also, he's been dead for a few years now.

Both things are a shame because I liked his blog a lot (along with Chen's)

<comment><USER9> Not knowing any of this I looked it up. [https://sortingitoutv2.wordpress.com/](https://sortingitoutv2.wordpress.com/)

It seems, according to Michael Kaplan, that he was fired from Microsoft for taking a photo with a personal camera of a framed plaque of a patent certificate with his name on it where the patent number was too visible. That is some horrid garbage.

Having gone through the corporate patent game myself it's not something I would ever recommend.

<comment><USER10> I just googled and came up with the same result.

Does anyone know why taking a photo of a patent (with the patent number visible) would be a fireable offence? I thought patents were public?

<comment><USER4> His blog post said "The second one was after I was granted a patent that I honestly believed never should have been issued." If he posted the photo of the patent in an article where he simultaneously made that remark, that combination would be extremely damning evidence in any patent trial and could lead to the invalidation of the patent.

Although, on re-reading his statement, the firing wasn't the taking a picture of a patent, but including some ("infamous") art in another blog post.

<comment><USER11> The "infamous art" was a red screen of death from a beta copy of Windows Longhorn. Apparently the blog post was in the middle of the negative news cycle about Longhorn and his posting the RSOD didn't help.

That blog article is available at [https://web.archive.org/web/20170623173912/http://archives.m...](https://web.archive.org/web/20170623173912/http://archives.miloush.net/michkap/archive/2005/05/07/415335.html)

He blogged about it ten years later at [http://archives.miloush.net/michkap/archive/2015/09/04/87706...](http://archives.miloush.net/michkap/archive/2015/09/04/8770668856267197190.html)

</comment></comment></comment></comment></comment></comment><comment><USER12> Guessing that printers originally picked the Q because (in some face) the plug was square, so fit in a frame sideways.

<comment><USER13> My guess too, also because Q doesn't get used much so there's probably one spare in the box

</comment></comment><comment><USER14> Is there also a Unicode encoding for the invisible interjection "fnord"? I tried looking it up in the Unicode dictionary but could not find it, but maybe I'm just not seeing it...

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

>In the novel trilogy (and the plays), the interjection "fnord" is given hypnotic power over the unenlightened. Under the Illuminati program, children in grade school are taught to be unable to consciously see the word "fnord". For the rest of their lives, every appearance of the word subconsciously generates a feeling of unease and confusion, preventing rational consideration of the text it appears in. The uneasiness and confusion create a perpetual low-level state of fear in the populace. The government acts on the premise that a fearful populace keeps them in power.

>In the Shea/Wilson construct, fnords—occurrences of the word "fnord"—are scattered liberally in the text of newspapers and magazines, causing fear and anxiety in those following current events. However, there are no fnords in the advertisements, encouraging a consumerist society. The exclusion of the text from rational consciousness also enables the Illuminati to publish messages to each other in newspapers, etc., without fear that other people will be aware of them. It is implied in the books that fnord is not the actual word used for this task, but merely a substitute, since most readers would be unable to see the actual word.

[...]

>Paulo Goode, a typeface designer from West Cork, Ireland, created a humanist serif font named Fnord in 2016 which contains 23 fonts in five weights. The geometry of the upper case 'O' is drawn on an axis of 23 degrees while the lower case 'o' falls on a 17-degree axis. The 23 / 17 numerology is reflective of similar numerical themes from The Illuminatus! Trilogy.

</comment><comment><USER15> ℺</comment>


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Double Slit Experiment No Mystery - <AUTHOR> https://billwadge.wordpress.com/2019/10/25/double-slit-experiment-no-mystery/ <comment><USER3> This misses whole swathes of the double slit experiment.

It doesn't cover the Observer problem, which means it doesn't acknowledge duality, which (you would have to assume) means it doesn't even recognise delayed-choice quantum erasers.

At the risk of getting downvoted to oblivion I feel like the author needs to study up on quite a bit more of this research as there's a much larger body of evidence than that which is countered in the article.

<comment><USER4> The author of TFA has little understanding of what they're talking about and misses all of the nuance of the double slit experiment and its relationship to other QM phenomena like the Dirac three polarizer experiment[1] and delayed choice quantum eraser experiment[2]. The three polariser experiment in particular makes it almost impossible to argue that light is a particle even if it had hidden state, unless that hidden state was propagating faster than light.

TFA reads like /r/iamverysmart content or a medium effort troll post. I don't understand how this ended up on HN frontpage.

[1] [http://www.informationphilosopher.com/solutions/experiments/...](http://www.informationphilosopher.com/solutions/experiments/dirac_3-polarizers/)

[2] [https://en.wikipedia.org/wiki/Delayed- choice_quantum_eraser](https://en.wikipedia.org/wiki/Delayed- choice_quantum_eraser)

<comment><USER5> I didn't know about Duane's hypothesis even though I read a few books mentioning the double slit experiment so I'm glad I read the article. In the end, as much as the wave/particle duality seems mysterious at the moment, I'm convinced we'll find a quite boring/straightforward explanation for it.

</comment></comment></comment><comment><USER6> Actually the mysteries are deeper. This one can't explain "Delayed Choice Quantum Erasure" experiments, which is also a double slit experiment. But the arrangement allows you to detect the path _AFTER_ the photon has traveled through one of the slits and hit the surface. Now _after_ the photon has hit the surface you can decide whether to detect its path or not. A delayed choice. But based on your later choice the interference pattern of the photon from a time from the past appears, or doesn't.

This is the main reason why some scientists come up with many world interpretation. This article doesn't even touch the surface of it.

[https://en.wikipedia.org/wiki/Delayed- choice_quantum_eraser](https://en.wikipedia.org/wiki/Delayed- choice_quantum_eraser)

<comment><USER7> How can a "thought experiment" demonstrate anything?

<comment><USER8> Well, from the article on the dual-slit experiment ...

> What many don't realize is that the double slit experiment (with particles), > proposed by Feynman in 1963, was for decades only a thought experiment. > Finally, in 2013, it was successfully performed with electrons.

<comment><USER6> The author implied it was a thought experiment for "particles" like electron, though actually demonstrated from the very beginning for non-particles such as photons.

That claim still might not be true.

</comment></comment></comment></comment><comment><USER9> > What many don't realize is that the double slit experiment (with particles), > proposed by Feynman in 1963, was for decades only a thought experiment. > Finally, in 2013, it was successfully performed with electrons.

Total crackpot, electron diffraction was observed in 1927 by several different groups of people[1][2] some of them who later in 1937 shared the Nobel Prize in Physics[3].

[1] [http://www.nature.com/nature/journal/v119/n3007/pdf/119890a0...](http://www.nature.com/nature/journal/v119/n3007/pdf/119890a0.pdf)

[2] [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1085484/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1085484/)

[3] [https://www.nobelprize.org/prizes/physics/1937/summary/](https://www.nobelprize.org/prizes/physics/1937/summary/)

<comment><USER10> Came here to say this, but the 1927 experiment was only the first with electrons. The first experiment with light was in 1803 by Thomas Young. This was the foundation of the wave theory of light.

I stopped reading the article at this point.

[http://www.cavendishscience.org/phys/tyoung/tyoung.htm](http://www.cavendishscience.org/phys/tyoung/tyoung.htm)

</comment></comment><comment><USER11> It is very common in physics that the same phenomenon can be explained using different concepts. Treating particles hitting a regular structure as diffraction of de Broglie waves gives exactly the same results as the momentum transfer approach the author prefers. In fact, both can be derived from standard quantum mechanics and both are widely used, depending on which is easier in the particular case.

However, scattering particles off objects is only one of many experiments they can be done. For instance, one will have a hard time explaining how atoms work without using some kind of wavefunction description of the electrons. Furthermore, as other commenters have mentioned, there are more sophisticated versions of the double-slit experiment, such as the delayed-choice quantum eraser, where the "quantum weirdness" simply cannot be argued away.

Frankly, it is pretty insulting by the author to assume that physicists intentionally choose the "more complicated" explanation over the "simpler" one.

<comment><USER12> +1 for the delayed choice quantum eraser as being the one experiment that makes it more or less impossible to argue against quantum weirdness.

<comment><USER13> The delayed choice quantum eraser is often explained as being more 'spooky' than it actually is.

The interference patterns only appear when you compare coincidences between the detectors. It's easy to see you could get an interference pattern after the fact by taking a bell curve (no interference) and subtracting out a sine curve (interference).

<comment><USER14> but how do you get the sine curve in the first place? because you're not subtracting a sine curve, you're subtracting non-coincidences, for which there is no reason they would be on the sine curve

</comment></comment></comment></comment><comment><USER15> Getting some real crackpot vibes here.

How does Duane's hypothesis account for the diffraction pattern going away if the particular slit the particle goes through is measured?

<comment><USER16> If he had read the article that he linked to, he'd see that duane's hypothesis is a special case that can be derived from quantum mechanics.

I don't believe that you can derive the rest of quantum mechanics from duane's hypothesis.

<comment><USER17> I agree. The relevant paragraph from [https://en.wikipedia.org/wiki/Duane's_hypothesis](https://en.wikipedia.org/wiki/Duane's_hypothesis)

> _Quantum mechanics_

> _According to Ballentine, Duane 's proposal of quantum translational > momentum transfer is no longer needed as a special hypothesis; rather, it is > predicted as a theorem of quantum mechanics.[22] It is presented in terms of > quantum mechanics by other present day writers > also.[23][24][25][26][27][28]_

</comment></comment></comment><comment><USER18> I'm a physicist and I'm sorry to say this blogpost is just drivel (I'm sure the original works linked are perfectly fine).

</comment><comment><USER19> Duane doesn't explain double slit experiment. It says momentum exchnge is quantized if you direct particle at lattice and this gives same pattern as interference.

If you consider single electron in this interpretation, point like particle without any associated wave or ability to be in more than one point of space at the same time ... when it is directed and passes through one of the slits, it produces the pattern but only if the it potentially could have been directed at the other slit.

How the hell what could happen with a particle (but didn't) could influence what actually happened to the particle (quantized, not normal momentum exchange)?

\--

For me the way to deal with weirdness of double slit experiment is that electrons and such are just waves, all the time. Fuzzier, sharper but always waves. The only thing that makes us think that's not the case is that, when they exchange energy and momentum, it's governed with same equations as if they were two balls bouncing off of each other.

The truth in my opinion is that electrons don't bounce like tiny balls, but balls exchange energy and momentum as if they were huge, very sharp electrons. Macroscopic balls are waves too, but imperceptibly because they are build out of bazzilion particle waves all tangled together into a very constraining packet.

<comment><USER20> If you have wave-systems with high enough fidelity (Q-factor in a cavity for example), they behave a lot like particles in certain energy/time regimes. People yelling from a mountain top hear echoes.

<comment><USER19> People have always thought about "atoms" of matter as being primary units of existance and waves being some second order, compound behavior. That's why it was so hard to get rid of the idea of ether.

</comment></comment></comment><comment><USER21> > _Duane's Law says that if a body is periodic in space in a given direction > then momentum exchanges in that direction are quantized. That means that the > emerging electron is more likely to go in certain directions than in others, > depending on how many quanta of sideways momentum are exchanged. Guess what? > When a stream of electrons is sent through, a 'diffraction' pattern > results._

If this "direction preferentiality" were all that were needed to cause a diffraction pattern, then we should see it if we run the experiment with one slit closed for a while, and then the other slit closed for a while.

But that's not what happens! If you send particles through only one slit, you _do not get a diffraction pattern_! (Actually you do, but the valleys are spaced far wider than those with both slits open.) No diffraction pattern = no valleys. Running the experiment again with the other slit closed can't add those valleys in. This is logically no different than individual electrons simply "randomly" entering alternate slits, so that can't make a diffraction pattern either.

What am I missing? It seems like the author is trying to explain double-slit purely in terms of statistical ensembles of quantum-ish particles rather than exploiting the full generality of quantum fields, which makes _no sense_ simply by looking at the results of a single- vs. double-slit setup. (e.g. [https://en.wikipedia.org/wiki/Double- slit_experiment#/media/...](https://en.wikipedia.org/wiki/Double- slit_experiment#/media/File:Single_slit_and_double_slit2.jpg))

</comment><comment><USER22> QM is easy to describe. There is wave-particle duality, but not at the same _' time'_, only in a strict alternating sequence of propagations and interactions.

 _Propagation_ is completely wave-like. It is unitary and time reversible, without loss of information. There is no particle there, and no _' there'_ there, as the propagation is non-local. Waves have complex amplitudes. Interference happens because that's what waves do. Propagation is described by the Schrodinger/Dirac equation.

 _Interaction_ is completely particle-like. The interaction is non-unitary and time-irreversible. The interaction may also be known as _detection_ or _measurement_.

The wave only contributes the probability of the interaction happening, which is described by the Born Rule. Amplitudes are complex, so squaring them with the Born Rule can give negative probabilities, which is why the double-slit experiment gives many fringes.

The interaction is local, because it creates the _' there'_. Positions and distances are created by the interaction as a specific spacetime event. Hence the aphorism _spooky distance at an action_ , meaning that (inter)action is fundamental, and distance is a strange thing created as a byproduct.

There are _conservation laws_ that balance some incoming and outgoing properties, _scattering laws_ that determine how the interaction happens for various _forces_ , and some constraints between the knowable values of _commuting pairs_ of observable state (particle properties) that are revealed (entangled) by the interaction. These constraints are also known as Heisenberg's _Uncertainty Principle_ , but are really just direct and obvious mathematical properties of wave packets, as described by Fourier Analysis.

After the interaction, there will be propagation of new waves for the outgoing _particles_ (meaning a bundles of state). The interaction results in an _entanglement_ (correlation of future possible interactions) between these distinct outgoing waves.

That's it.

<comment><USER23> > QM is easy to describe.

That's easy for you to say!

<comment><USER24> I understand QM intuitively. I just don't wanna explain it to you is all.

</comment></comment></comment><comment><USER25> Physicist here. This is just self-congratulatory nonsense. Though I shouldn't be surprised, because I originally signed up for this site to comment against some other self-congratulatory nonsense.

Quantum mechanics is built on extraordinarily simple rules, in fact simpler ones than classical mechanics: all you do is sum up the amplitudes for various paths, and square it to get a probability. The problem is that the objects obeying these rules thus act _neither_ like particles _nor_ waves. So obsessing over whether quantum objects are "really" particles or waves is not useful.

It certainly works sometimes. There are many limits where quantum objects behave just like particles, or just like waves (there must be, since we must be able to recover classical mechanics from quantum mechanics). And sometimes you can _describe_ a quantum calculation in terms of classical wave or particle intuition, which is what's going on here. The double slit experiment is in fact so simple that I know of at least 5 ways to derive the result, using all sorts of different intuition. "Duane's law" is one of them, though I never knew it had a name, as it pops out rather straightforwardly from the mathematics.

The reason that we don't try to extend this to cover all of quantum mechanics is because it doesn't work. Treating the quantum mechanics as if it were classical underneath leads to all kinds of paradoxes. Bell inequality violations tell us that the classical variables would have to either influence each other faster than light, or be pre-set since the beginning of the universe in a malicious conspiracy. The delayed choice quantum eraser tells us that if you want to treat the photon as a classical particle, you need to accept that it can _retroactively change the past_. Yet another failed attempt is quantum logic: if you insist on treating quantum superpositions as representing some unknown classical position of a particle, you need propositions about those positions to _violate the rules of logic themselves_.

Hundreds of experiments probing quantum mechanics have been performed, all with the same results: committing to a classical ontology in terms of "waves" or "particles" costs you more than just accepting that quantum objects are different from either.

Physicists have spent a _lot_ of energy thinking about this. All of the author's claims were under active debate in the 1920s. He is just completely ignoring the following century of investigation, and claiming that it never happened!

<comment><USER26> > the classical variables would have to either influence each other faster > than light, or be pre-set since the beginning of the universe in a malicious > conspiracy

Why is superdeterminism almost universally rejected by working physicists? From the outside, it feels like the most parsimonious explanation: there is just a single way things are and will be, set in motion from the very beginning. It doesn't feel like a conspiracy of any kind to me.

I'm definitely missing something, but what?

<comment><USER25> Because if you take superdeterminism seriously, you can't do science.

Sure, it is logically possible that the world runs on classical mechanics, but that random factors in the light emitted from opposite ends of the observable universe billions of years ago were delicately set at that point so that whenever you run an experiment with it, naively assuming that no such correlations exist, quantum mechanics appears to be true instead.

Unfortunately, if you are consistent with applying this principle you can't conclude anything at all. If you see the Sun and planets move every day, would you eventually accept orbital mechanics, or would you prefer the explanation that "orbital mechanics is false, everything actually moves however it wants according to random unknown factors, but those factors were arranged just so that whenever we make observations, standard orbital mechanics _appears_ to be true"?

Suppose we're betting on horce races, but I win 100 times in a row while you always lose. Would you accept my explanation that "this was merely superdetermined to be the case"? Or would you start to suspect that I'm stealing your money?

Superdeterminism is philosophically equivalent to Cartesian skepticism. It's just a minor twist on being a brain in a vat. Scientists reject this not because we can disprove it, but because you can't _do_ anything if it's true. I mean, you might as well not bother getting out of bed in the morning.

<comment><USER27> > _you might as well not bother getting out of bed in the morning._

Sometimes I feel that way.

But I get up, take my meds, and press on.

</comment></comment></comment></comment><comment><USER28> When I watched a goofy layman's explanation[1] about the double slit, it stressed the importance of the effects of observation on the behavior or nature of the electrons.

When observed to see "which" slit the light passed through, they no longer created the interference pattern described by Duane's law. And when left unobserved (at the slits) the interference pattern emerged even when shooting "one electron at a time" at the slits.

Does this article or Duane's Law cover or appreciate this? It seems like it only describes the interference pattern.

1\. [https://m.youtube.com/watch?v=Q1YqgPAtzho](https://m.youtube.com/watch?v=Q1YqgPAtzho)

<comment><USER29> The focus on "observation" in quantum mechanics is dumb and damaging. In quantum mechanics observation means something very different from what people assume when you use the word observation.

When you say "if we observe the position of the electron" people think: "we put an observer who without interring in any active way and he looked at the electron to see where it is". What QM actually means is more akin to "if we take a 200 Ton bulldozer and force the electron into one or two positions and then test which one it's in".

The very issue arising from Observer effects is that you cannot have the system in a single state where for instance momentum and position are both observable, and observing either means forcing the system into a state where the other is "uncertain", that is to say that it will have a distribution of outcomes if you use a different 200ton bulldozer to observe this parameter afterwards. The uncertainty principle basically tells you that the technical requirements for a "position bulldozer" and a "momentum bulldozer" makes it fundamentally and axiomatically impossible to make a single bulldozer that carries out both "observations".

<comment><USER30> Observation is what makes physics matter in the practical sense.

<comment><USER31> Is there anything about the point being made that is inconsistent with that?

<comment><USER30> A theory without observables is not science.

<comment><USER31> The point being made is that all observations change the thing being observed, so you have to be very careful what you measure and how you measure it. That is all. This is a basic point in science that is often missed. As here, apparently.

</comment></comment></comment></comment></comment></comment><comment><USER32> This is intellectual arrogance on full display.

</comment><comment><USER33> The hallmark for any reinterpretation of QM in terms of more classical ideas would be that it explains Planck's constant in terms of other constants. If an explanation of a quantum phenomena succeeds to eliminate one of the fundamental constants, all physicists will provide a listening ear, no conspiracy involved...

</comment><comment><USER34> Single slit diffraction and double slit diffraction are very different. This difference is elegantly and simply explained by the wave model. Without it, you'd expect the double slit experiment to create a simple sum of the pattern from each of the slits, but what you get is a completely new pattern that depends on the spacing between the slits, and the wavelength of the thing passing through.

</comment><comment><USER35> With respect I simply disagree with Feynman that the double slit experiment contains everything... Maybe in suggestive outline?

As an example of how QM is weird, my go-to is a game that I call Betrayal. It is a challenge for a 3 person team. The teammates go through rounds where they are relativistically separated and unable to talk with each other; each such room has a big computer screen and two buttons labeled 0 and 1, and during each round each teammate has to press one or the other of these buttons; then their selections are summed up to a number that we call The Sum.

The reason we call this Betrayal is that we are trying to force one of the teammates to betray the other two. So 25% of the time we run a "control round" where we ask everyone to make The Sum even, and the team passes the round if The Sum is even. Or the rest of the time we secretly select one of the three at random to betray their colleagues: we tell the other two the true goal, make The Sum odd, and the team passes the round only if it is odd: but we lie to the traitor and tell them to make The Sum even, so they will work at cross purposes to the other two.

The key result is that there are 4 cases and classical strategies can only work for at most 3 of them, so your pass rate is limited to 75%. But quantum players who share a so-called "GHZ state" can pass 100% of trials in principle—albeit quantum computers have finite probabilities of simply failing, but if you could improve that to 90% fidelity then over the course of 100 rounds you will still score visibly ahead of the 75s, occasional 80s, and rare 85s produced by random chance.

The key is that quantum systems come out with these strange global correlations that cannot be explained classically. You also cannot see them locally; nobody knows the round succeeded until everyone comes back together to compare what bits everyone committed to.

</comment><comment><USER36> 1\. It's very nice to be introduced to Landé and Duane.

2\. After so much emphasis on reason and experiment and evidence, it is jarring to switch gears to a conspiracy theory about scientists concealing or ignoring theories in order to make themselves seem "superhuman."

3\. It's very nice to be introduced to Landé and Duane.

<comment><USER37> You'd be surprised how much scientists hush and push dissenting voices which don't suite a particular theory which one cabal wants to be true. Sean Caroll has been advocating strongly in public to go back and take a look at measurement problem but nobody wants to do it. He speaks more about this on his podcast (mindscape) and also on Joe Rogans podcast ( I mean the fact that he had to bring it up in Joe Rogans podcast to let the public know what's up) is pretty bizzare and in indicative of the kind of schemes that go on in academia.

<comment><USER25> This kind of conspiratorial thinking is precisely the problem. There is a constant avalanche of papers being published on interpretations of quantum mechanics, in my mind, too many. To believe that Sean Carroll is the only person thinking about this is frankly insulting.

This is comparable to hearing one C++ developer speak, then getting the impression that they are the only programmer in the world who uses a strongly typed language, and that there's a conspiracy to cover up strong typing.

</comment></comment></comment><comment><USER38> > Admittedly there's still a bit of mystery left. How does periodicity in > space quantize momentum (I think if it as a sort of resonance phenomenon). > But it's hardly an impenetrable, soul searing mystery that makes you > question reality itself.

I don't find this to be true. What's left is the key issue. The entire mystery is left. The old QM worked exactly like that explanation: you take a classical explanation and postulate that some quantity in it is quantised. This is ad- hoc and not a general approach. A major breakthrough in the new QM was an explanation why things are quantised. And yes, it's a resonance phenomenon. Resonance of what? Probability amplitude waves. Once you have that explanation you can do away with the classical+quantised part of the explanation, because it becomes superfluous.

</comment><comment><USER39> The problem/mystery is more that the double-slit experiment and other quantum phenomena are always presented in a hand-wavy way where it's not clear how it derives from the mathematical formalisms.

</comment><comment><USER40> The author has gotten confused the bit about the double slit experiment that is "mysterious".

The mysterious bit isn't what happens when you transmit a stream of particles.

It's what happens when you only send one at a time. If the movement was purely changes to particle momentum you would get a uniform spread across your detector.

But that's not what happens. What happens is you get a diffraction, that only makes sense if your particle goes through both slits.

</comment><comment><USER41> Reading things like this article and replies, it seems apparent that physics research, or at least teaching, often blurs the distinction between experiments in thought or otherwise explaining a theory, and those that motivated theory by empirically disproving previously-held beliefs.

Also I've noticed a strange form of entropy in physics that tends to show more evidence for models that have the largest number of equivalent formulations based on different assumptions. You could say that this is a result of how physicists work to prove their own theories, but perhaps the gods work the same way.

Waves of probability amplitudes with quantized action is a nice abstraction that works so far, but so was continuum mechanics. Wave-like observations could easily be a simple consequence of the central limit theorem in the same way.

</comment><comment><USER42> Has the double slit experiment been done and verified in a vacuum? I'm able to produce the superficial results with a simple neon laser, but it always struck me that outside a vacuum, there is a lot available to skew those results.

<comment><USER17> > _Has the double slit experiment been done and verified in a vacuum?_

99.9999999% sure yes, but I can't find a source with the actual experiment. The versions with electrons are made in vacuum, but I'm not sure they use the double slit pattern.

You can reproduce the experiment with light in air. It's expected that you will get the same result in vacuum. An actual experiment is nice, but the setup in more complicated, so it's not done in a normal lab class.

It should be easy to setup for someone with access to a vacuum pump, and some free time (1 week top). It would be nice to see how the lines move when the refraction index of the air that is almost 1 changes to the refraction index of vacuum that is exactly 1.

It's hard to convince someone of doing the actual experiment, because it looks a lot of work without an insightful result. Perhaps you are lucky and someone already did this. I guess this is the case, but I can't find it. Perhaps you can convince someone like Cody of "Cody's lab" to make the experiment and upload a video.

<comment><USER42> Exactly. Lots of food for thought there.

I _expect_ these results in the open air, since there is so much for the photons to bounce off of. They're probably even bouncing off the sides of the actual slits, unless the block is thin and precise enough, and anti-reflective enough to not allow light bouncing off of it - straight polarized lines only.

This is why I ask such a specific question. I don't deny the effect is happening at all - I question the influence of other parts not taken care of in the experiment.

We speak of "noise" (interference) when discussing related observations in regards to quantum computing. I'm hoping we're at least as stringent about these experiments. But so far, I've only ever seen them done in open-air environments, which to me leaves too many nagging questions. I doubt the quantum effects I can produce in my dusty office are as precise and pure as they would be in a proper lab, but all the evidence I've seen is that I'm doing it pretty much precisely the same (sloppy) way.

Electrons do indeed show the same effect and I recall reading once that the experiment was first proposed using electrons. There are other particle/wave effects as well, but those two are the easiest to demonstrate with, apparently.

<comment><USER17> > _We speak of "noise" (interference)_

Note that interference here has a very technical meaning that is NOT noise. (Sorry for the all-caps, but it's very important in these experiments.)

I think you don't understand the important point in the double slit experiment. Let's try to explain it, but it's a long explanation.

\---

First you must understand the single slit experiment. If the slit is thin enough you get a nice diffraction patter.

If this spread was caused by dust or something like that, a good guess is that the image gets a gaussian blur like exp(-x^2).

In a diffraction experiment, the image you get is something like sin²(x)/x². (You should draw them in Wolfram Alpha or something.)

The main difference is that the first one is always positive, so you get light everywhere, but it get's dimmer very soon. The second one has a lot of zeros, so you get strips of light and darkness. The math details are complicated, so let's ignore them.

You can do this experimentally. In the lab we used two razorblades with some screws to move them arcuately. There should be plenty of recipes in Internet to reproduce it. You can try it in more dusty environments, and clean environment. Sharp razorblades, not sharp razorblades. Wind or not wind. Try it a few times until you get use to the images it produces. You will notice that the cleaner environment produce the better results, so I hope you will get convinced that it's not caused by the dust or something

You can probably buy some single slit from an educational provider. Buy some of them of different width to compare the results with your homemade version.

It's important to understand how it looks before going to the second step, so play for some time with the single slit version. Some resources: [https://en.wikipedia.org/wiki/Diffraction#Single- slit_diffra...](https://en.wikipedia.org/wiki/Diffraction#Single- slit_diffraction)

\---

Now, the double slit version looks more difficult to make at home. I think you should buy one (or a few), and the single slit version with the same width.

The idea is that if it has only one slit you would see the old image. If you have only the other slit you would see the old image. If the screen is far away and the slits are very close, you can't notice the difference. So you would expect to see the same image, but with more bright.

The weird thing is that you don't get the same image. You get almost the same image but with a lot of additional strips. There are the old dark lines and many new dark lines. These new dark lines are the interesting one. In this lines you have something like

. light + light = darkness

Try the experiment in air and try to read the explanations in [https://en.wikipedia.org/wiki/Double- slit_experiment](https://en.wikipedia.org/wiki/Double-slit_experiment) and [https://www.youtube.com/watch?v=Iuv6hY6zsd0](https://www.youtube.com/watch?v=Iuv6hY6zsd0) . Try again until you scream <all-caps> "The new dark lines are weird!"</all- caps> If you are not screaming, try the experiments with one and two slits again and the info again.

You can try with a dusty windy environment, and it should make the lines more fuzzy. You can try wit a clean environment and get better results. The lines are not caused by the dust, they are just weird.

. light + light = darkness

(If you are going to buy things, add a diffraction gratting. It's like using many slits instead of two. The math is more difficult but they create nice rainbows. [https://en.wikipedia.org/wiki/Diffraction_grating](https://en.wikipedia.org/wiki/Diffraction_grating) )

The dark lines are not so surprising when you use light that is usually approximated a wave. But if you get more advanced equipment you can repeat the same experiment with electrons or neutrons and get the same weird lines. (When you understand this, you can scream again.)

</comment></comment></comment></comment><comment><USER43> I actually don't like the double slit experiment because it's so easy to confuse yourself. Good for learning the math, maybe, but bad for presenting the "weirdness." Tests of Bell's inequalities are much more interesting and IMO cut straight to the heart of the weirdness of QM. Likewise with tests of the quantum Zeno effect. For me, at least, these two experiments go straight to "okay fine, measurement is weird and let's just treat superposition as its own thing" while double slit experiments beg for hand waving mysticism.

</comment><comment><USER44> For those who don't know, Bill Wadge is an esteemed computer scientist who created the Lucid dataflow language with Ed Ashcroft.

Not that that has anything to do with the double slit experiment, but it's worth knowing.

</comment><comment><USER45> If you like crackpot "science" check out Rex Research. (Fair warning, not everything there is BS, but you can find all sorts of weird stuff to gawk at.)

</comment><comment><USER46> "Something that is periodic in space"

I could swear we have a name for that. I think it started with a W?

</comment><comment><USER47> No physicist but feel like this should show up in a one slit experiment

</comment><comment><USER48> The wave/particle duality notion isn't really meant to hold an accurate deep insight into QM, it's just meant to inform intuitions, and sorta communicate it to laypeople.

<comment><USER30> This is not correct. The duality is the fact that an elementary particle is point-like but requires wave mechanics to describe its motion. Another related discovery was that energy waves, too, consist of quanta, which in many respects behave as particles. Those are valuable physical insights (similar in its power to the idea that "everything consists of atoms").

<comment><USER17> I disagree with your disagreement, but perhaps we all three agree.

The electrons/photons/whatever must be described quantum field theory, but the math is too complex to use it unless it's a very simple experiment with a few particles or with a computer. So it's good to have some simplifications.

In some cases, you can approximate an electron/photon/whatever as a wave. The math is much simpler and with some training you can to with paper and pencil or in some simple cases with handwaving.

In other cases, you can approximate an electron/photon/whatever as a particle. The math is much simpler and with some training you can to with paper and pencil or in some simple cases with handwaving.

I don't like the name "wave–particle duality" but it is probably too late to change it. It's not true that an electron/photon/whatever _is_ sometimes a particle and sometimes _is_ a wave. It is always a weird quantum thing that sometimes can be _approximated_ as particle and sometimes can be _approximated_ as wave.

For historical reasons, people discovered first the approximations, named it as the "wave–particle duality", and later understood what is really happening.

<comment><USER30> Except we may never know what's "really happening." Field theory is, well, "just" a theory, that is to say, an approximation, albeit a better one.

<comment><USER17> Yes, perhaps string theory is correct.

</comment></comment></comment></comment></comment><comment><USER49> [https://en.wikipedia.org/wiki/Escalation_of_commitment](https://en.wikipedia.org/wiki/Escalation_of_commitment)

</comment><comment><USER20> > What many don't realize is that the double slit experiment (with particles), > proposed by Feynman in 1963, was for decades only a thought experiment. > Finally, in 2013, it was successfully performed with electrons. It's easy to > see why it took so long: the slits were 62 billionths of a meter apart.

Who is this clown? I did the two slit experiment using a CRT (aka using electrons) in undergrad experimental physics class in the late 80s, and unless I had some amazing experience, I'm pretty sure every undergraduate physics major does the same thing. The '37 Nobel in physics was awarded more or less for doing this in the 1920s after de Broglie said it would be there.

<comment><USER50> Doing it with actual slits and standalone particles is not so easy:

[https://www.sciencedirect.com/science/article/abs/pii/S03043...](https://www.sciencedirect.com/science/article/abs/pii/S0304399112000599)

<comment><USER20> Doing the two slit experiment with electrons and actual slits is absolutely trivial, and that link doesn't say what you think it means.

<comment><USER50> "The general perception is that the electron double-slit experiment has already been performed. This is true in the sense that Jönsson demonstrated diffraction from single, double, and multiple (up to five) micro-slits [2], but he could not observe single particle diffraction, nor close individual slits. In two separate landmark experiments, individual electron detection was used to produce interference patterns; however, biprisms were used instead of double-slits [3, 4]. First, Pozzi recorded the interference patterns at varying electron beam densities. Then, Tonomura recorded the positions of individual electron detection events and used them to produce the well known build-up of an interference pattern. It is interesting to point out that the build up of a double-slit diffraction pattern has been called 'The most beautiful experiment in physics' [5, 6], while the build-up for a true double- slit has, up to now, never been reported."

[https://iopscience.iop.org/article/10.1088/1367-2630/15/3/03...](https://iopscience.iop.org/article/10.1088/1367-2630/15/3/033018/meta)

<comment><USER20> I did the experiment in 1989, closing individual slits and everything. There are entire fields of material science based on photo electron interference (ARPES, XPS and other photo emission spectroscopies). Quoting some clown who claims "well you never did it my (irrelevant) way" is not useful here.

<comment><USER50> If you think that citing a paper by a physics professor in a peer-reviewed physics journal is "quoting some clown" you'll probably understand that I don't give much weight to a comment from a random person on HN.

<comment><USER20> You're perfectly free to believe in ghosts, the flat earth or DMT elves as well. People who know what they're talking about are still going to laugh at you.

Do you think clowns who publish physics papers (and yes, those guys are grade-A quacks for writing that paper with such claims) are immune to the temptations of PR balognia? Do you really think "Ultramicroscopy" is a reputable physics journal? Had someone actually done something as innovative as his claims: it would be in Science, Nature and PRL. But I guess you don't actually know anything about physics and think google substitutes for knowledge and "muh links" substitute for argument.

<comment><USER50> For what it's worth, one of the clowns who coauthored that Ultramicroscopy paper is credited with the first observation of the build-up of the interference pattern from individual electron detections in 1974 (using an electron biprism, not slits in a plate).

<comment><USER20> I'm sure their motion picture tells us all about it. PR != reality.

<comment><USER50> What's the reality then?

Let's accept for the sake of the argument that it's a clownish thing to do in the 21st century to report that you're sending electrons one by one (at intensities low enough so the interaction is necessarily that of independent particles, not that of a beam) towards a metal plate with two slits (which can be opened and closed at will) and detecting the arrival of individual electrons at the other side as independent events. Because that's a trivial thing to perform and thousands of students were doing it already in the eighties.

You say that if it was innovative it would be in the cover of Nature or something. When would you say it was done for the first time then? Was it published in a top-tier journal when it was innovative? If not, why not?

<comment><USER20> I'd say you either don't understand the english language or are a bored grad student with nothing better to do than attempt to defy objective reality on the internet.

<comment><USER50> Maybe there is a misunderstanding. What I originally said is that "Doing it with actual slits and standalone particles is not so easy".

Are you claiming that it is absolutely trivial to do it with a double slit and single electron detections, and you were doing it in 1989, or not?

Probably not, but then I don't know why did you choose to reply to my comments in the way you did.

(I don't know either what do you imagine that I think that the paper I cited means, or what do you believe that the paper claims that is so innovative that it would belong in a much more reputable journal.)

</comment></comment></comment></comment></comment></comment></comment></comment></comment></comment></comment></comment><comment><USER51> The problem I have with this. Quantization must be a factor of wavelength and perhaps width of one slit. Yet the interference pattern produced by the double slit experiment depends on the distance between two slits. Diffraction pattern is not the same as an interference pattern, something the original researchers were well aware of.

</comment><comment><USER52> I'd recommend reading the book The Physics of God.

The author goes into a whole different theory on how it's possible for a photon to be both a wave or a particle depending on whether there is an Intelligent Observer/sensor.

</comment><comment><USER53> This explanation doesn't seem to leave any room for the experimental observation that simply knowing which slit the electron went through - <USER2> some physical interaction that disturbs it but simply having that knowledge - changes the pattern.

<comment><USER54> How would you know which slit the particle went through without physically interacting with it?

<comment><USER53> You can decide afterwards whether to figure out which way it went or not, and make your observation then. While the English language isn't great at describing this sort of thing, it seems fairly safe to suggest that I cannot choose now to physically interact with an event that happened in the past.

</comment></comment></comment><comment><USER55> I absolutely agree. We tend to forget that nothing is still in our universe.

Everything to the smallest quanta oscillates. The only way to get something to stop moving is by freezing it. You need to hit absolute zero to stop movement completely, I don't believe we have even observed absolute zero.

If you think about it, absolute zero shouldn't be possible. There are an infinite amount of degrees between 1 and 0. Aren't we only limited by the sensitivity of our equipment?

<comment><USER27> They don't stop at absolute zero, either, because then position and momentum would both be fixed.

But there is a continuous range of temperature all the way down, and there is plenty of work at increasingly tiny fractions of the last degree. It is meaningful to talk about what happens at a billionth of a degree.</comment></comment>


Mozilla is removing tab groups and complete themes from Firefox - <AUTHOR> http://venturebeat.com/2015/11/20/mozilla-is-removing-tab-groups-and-complete-themes-from-firefox/ <comment><USER2> I get and agree with focusing resources where you get the most payoff. But there is also something to be said for product differentiation. These two features definitely differentiate Firefox from Chrome and Safari, and do so in a useful way. There have been times that Tab Groups was the sole reason I stuck with Firefox. There have been times that the sole reason I did not move to Chrome was knowing I could never 100% personalize the GUI. Throw in the how Mozilla handled the DRM issue as well as Pocket and new tab sponsored websites fiasco and you begin to erode the privacy reasons for sticking with Firefox. Yes, Firefox must compete, must stay competitive, but if it becomes just another Chrome, there is no way they can compete with the resources Google can bring to the table. Firefox must compete on product differentiation or it will lose.

</comment><comment><USER3> Another heavy tab group user. I can see that the panorama part with drag & drop support takes quite some work to maintain. The ordering of tabs in groups however should not be that much extra work and is the important bits. Simplifying the code instead of axing it would be appreciated, but guess that ain't never going to happen. Of course I also use classic theme restorer.

The Pale Moon browser comes up more and more so I suppose it is time to check it out.

edit: OK, installed and love it (at least so far). Migration was smooth. Ran the profile import app with both browsers shut down and have ALL of my old tab groups using the tab group extension that has to be installed separately (install after the import). Almost all of my important extensions that where about to stop working are just fine. It feels good to be home again.

</comment><comment><USER4> Solution is simple, use Palemoon.

I've been using it for a few years now, its great.

It runs on all OS's, Windows, Linux, Android etc...</comment>


Show HN: Capture a screen area in OS X and automatically pin it - <AUTHOR> http://snappy-app.com/

<comment><USER2> This looks like a replacement for Skitch. It is nowhere near as good yet, but perhaps it will get there. I'm hoping it will!

Mind you, when I write "Skitch", I mean the original Skitch 1.0, not the disaster that happened after Evernote bought Skitch and decided to "redesign and integrate with Evernote".

<comment><USER3> The worst thing about Skitch is the integration with Evernote. No, I don't want to sync, I just want to take a screenshot and drag the image to an application.

<comment><USER2> Download Skitch 1.0. It is still available and works great — it is much more useful than their 2.0 version, in fact.

While it still works, it is by far the best solution for capturing quick screenshots and annotating them.

</comment></comment></comment><comment><USER4> I really like this tool! Thanks!

Some small requests thou:

\- I would like to be able to select multiple old snaps and delete them.

\- Some kind of Quit-protection would be nice, I closed Snappy by mistake when I tried to close a snap with Cmd+Q.

<comment><AUTHOR> Thank you for the feedback! The first point is planned for 1.2 which i hope to launch by years end. It also has annotations and more sharing+storage options. Plus iCloud with an iOS app so you can access the snaps on the phone. As for CMD+Q, you're right, it needs quit protection - added to list for 1.2.

<comment><USER5> CMD+Q is intended to quit: that's what CMD+W is for (for closing the current window).

<comment><USER6> Yes, but it's standard for apps to ask for confirmation before quitting if there's reason to think the user might not really mean it e.g. there's unsaved data or unfinished operations.

<comment><USER7> I know you know, but for those who don't: it _was_ standard. Apple nowadays promotes applications to autosave and restore windows with their content at startup.

I think an utility like this should follow that strategy.

</comment></comment></comment></comment></comment><comment><USER8> This seems to be solving a problem of information being hidden by overlapping windows - but that's also solved by tiling window managers, like Amethyst and osxmonad.

[https://github.com/ianyh/Amethyst](https://github.com/ianyh/Amethyst)

On the whole I think I prefer the Amethyst approach - the snappy overlays themselves obscure information beneath them.

<comment><USER9> If it weren't for the extraneous window decoration you end up with. I'm good with using Moom to size and shape my windows on the fly on OSX. I've been relatively happy tiling on Linux though, but customizing keyboard shortcuts gets tedious quickly.

The main problem with OSX has been knowing which window is foregrounded, especially with two monitors.

</comment></comment><comment><USER10> I thought this was superfluous until I downloaded it. It does what it does so well that it makes itself useful in a surprising number of ways - for me, I can quickly screen grab anything I need to remember or keep around for the day and put it at the front of my secondary screen.

Simple idea, great execution.

</comment><comment><USER11> What I thought this was judging by the name (and what I want): Windows-style window 'snapping' at the edges. Pull window to the left to dock in the left 50% of the screen. To the right for the right 50% of the screen. Up to take up the whole screen.

One of the few things I miss about Windows.

<comment><USER12> You might like BetterSnapTool - [https://itunes.apple.com/US/app/bettersnaptool/id417375580?m...](https://itunes.apple.com/US/app/bettersnaptool/id417375580?mt=12)

<comment><USER11> Looks perfect. Thanks!

</comment></comment></comment><comment><USER13> Most of this isn't useful to me, but I really like your "Snap Webpage Preview" feature. Sometimes I just want a clean copy of the site, and this is a fast easy way to get it.

I also like the Snaps from the Past, so far, fast to load, and clean. Good defaults for sorting.

One thing I think would be nice, would be once you have a floating snap, if I mouse over it I'd love to see where it was taken. I realize that information is available in the Snaps from the Past window, but a quick transparent window with clear text across the bottom of the snap (not sure what you'd do if the snap was too small) would be wonderful.

Thank you for the opportunity to try this app. When you put your price back up, I've a number of clients I'll be recommending it to.

</comment><comment><USER14> I wrote an app that takes aspects of this to the next level, especially the cases where they recommend when to use it.

In my app, you capture a full window instead of a portion of the screen. Then the snapshot is continually updated. It's not for saving, just for cross- reference really. Though it also works really well in presentations and demos.

[http://appstore.com/mac/duplicatewindows](http://appstore.com/mac/duplicatewindows)

</comment><comment><USER15> I've been using Screenfloat ([http://www.screenfloatapp.com](http://www.screenfloatapp.com)) for a long time, the one thing that I didn't like about it was the delay involved from screenshot execution to display. Sometimes this could take 4-5 sec which was a pain cause I needed it to be instantaneous. SnappyApp solves this problem so thank you, you've just become the replacement :)

<comment><AUTHOR> We won't disappoint. :)

</comment></comment><comment> triple-double This looks really great. I take tons of screenshots, always forget to delete the file on my desktop after I'm done doing whatever I need to do with it (email it, tweet it, whatever), and then spend too much time cleaning everything up once I've amassed too many. Now I can do what I need to do with it, keep it or delete it, and not have to worry about my desktop filling up.

</comment><comment><USER16> Nice work. Might be interesting to be able to add our own backends, e.g. allow a URL to be entered in preferences and then SnappyApp just does a regular POST of multipart/form-data and the "Location: ..." returned by the server is copied to the clipboard as the shareable URL.

</comment><comment><USER17> I use Jing in first place for fastly sharing screenshots and videocasts. But I also use it 3-4 times a year for the same functionality your app provides. [http://www.techsmith.com/jing.html](http://www.techsmith.com/jing.html)

</comment><comment><USER18> I kind of see the utility of having screenshotted rects remain visible. I personally will stick with Cmd+Shift+4 since it does the screenshot-with- bounds and saves to desktop by default. Maybe I just don't see what the extra value is here?

<comment><USER19> Automated upload instead of having to use Dropbox.

<comment><USER20> I've used Cloud app for this in the past - works great, but has an upload limit. What's the story on that here?

</comment></comment></comment><comment><USER21> Voila does the same + much more, like gallery manager and recording with sound. Also uploading to SFTP and FTP.

[http://www.globaldelight.com/voila/](http://www.globaldelight.com/voila/)

<comment><AUTHOR> The concept is a bit different. Snappy is not a screen capture app, it's a tool for referencing info between screens. But granted, it does it by taking a snapshot of a portion of the screen.

Snappy is designed to be seamlessly used, not a feature packed app. It's an extension to the OS.

</comment></comment><comment><USER22> This is excellent - I've been looking for a simple replacement to Skitch for a while. Any chance you could add either Cloud.app support or let me drag the image to Cloud.app (like you can with V1 of Skitch)?

<comment><USER23> Have you seen [https://www.monosnap.com](https://www.monosnap.com)? It's worked well for me as a Skitch replacement.

</comment></comment><comment><USER24> This is really cool but I have one question: "Now free, one month only" that means it's free forever if I download it this month or can I use it for free for one month and then I have to pay?

</comment><comment><USER25> The demo would be more useful if it told me I can drag the boxes after snapping them, and if the page had more vertical scroll space so I could see them stay in place when I scroll.

</comment><comment><USER26> I didn't know I needed this but it's great!

Some feature requests:

\- Ability to resize by grabbing corners

\- Option to quit after all snaps are closed

<comment><AUTHOR> Glad you like it! Funny thing, "I didn't know i needed this" is the most common feedback we get. :)

Resizing is on the list, although it will impact the image quality if you resize up. On the same list I have making the window transparent so you can see content below it.

Not sure if I understand the second one. Do you mean quit Snappy after closing all snaps? (it's quietly sitting in the top bar)

<comment><USER27> With that being the most common feedback you get, I would highly recommend adding some good use cases to your landing page to tell people why they _should_ want to use it.

<comment><AUTHOR> Will do. New website coming up v1.2. Thanks!

</comment></comment></comment></comment><comment><USER28> Quite a coincidence. I was seriously thinking that I could really use an application precisely like this earlier today, and here it is!

Love it!

</comment><comment><USER29> Hello everyone, because of the HN traffic, i'll have to take the site off-line for a few minutes to resize the server.

<comment><USER29> Back online :)

</comment></comment><comment><USER30> I love it. Something I won't use all the time, but will be glad that it's there when I need it.

</comment><comment><USER31> Incredibly useful, getting my whole office to use it. I only wish I could resize the snaps on my screen.

<comment><AUTHOR> Resizing snaps is actually one of the next features on our list. :)

</comment></comment><comment><USER32> Is it Free to use for one month, or free to download and use forever, offer expiring after one month?

<comment><USER33> It's in the Mac App Store (they can't charge you again later) so it's free to download and use forever, offer expiring after one month.

</comment></comment><comment><USER34> Personally, I use the Dashboard clipping tool in Safari, I don't quite see what this adds.

<comment><AUTHOR> Well, it doesn't limit you to clipping in safari for one.

And even if you only clip in safari, it's not that seamless of a process with selecting the area and all.

</comment></comment><comment><USER35> They should list the price on the website

<comment><AUTHOR> It's free. :)

</comment></comment><comment><USER36> Can I hide the icon from the top bar?

<comment><AUTHOR> In this version, no. But you will be able to do this in the next one.

</comment></comment><comment><USER37> everything is good, but i think the image sharing url is a little bit of ugly :((

<comment><AUTHOR> I know, it is. We're shortening it with the next version. :)

</comment></comment><comment><USER38> wow, already used this several times this morning. Thank you!</comment>


Ask HN: What software engineers/programmers to make sense of large code? - <AUTHOR> I'm interested to know if there are tools or programs that help software engineers understand big source code bases (projects that have lines of code in the thousands), like how to understand all the parts involved. <comment><USER2> FYI, "Thousands" of lines isn't particularly, a large code-base, I'm a developer who tends to specialize in legacy code bases and I've seen aspx (asp webforms) pages with 5k+ LOC in a single file.

Also, you haven't really defined what "makes sense" means for you. Does that mean being able to refactor it, maintain or just evaluate it?

That said, the following are essential:

1\. An IDE with a fast token-based search

This is the number one requirement, you need to be able to search for a badly remembered function or variable name to find the method. Jetbrains' "Go to anything" search that resharper/rider has is unrivalled here, you can quickly see partial matches and the type of match (function, variable, etc)

2\. An IDE with a text editor that won't choke with 5-10k LOC files.

If your environment is freezing up any time you open a certain file then you'll have no chance if (and you likely will, for a large enough project) you encouter a monster file.

3\. Pen and Paper

Don't be scared to write things down, draw diagrams and write down your mental models as you go. A pen and paper is essential, it persists through all sessions, can't crash and if you think something is wrong you can easily throw it out and start again without considering that time wasted.

<comment><AUTHOR> > Also, you haven't really defined what "makes sense" means for you. Does that > mean being able to refactor it, maintain or just evaluate it? I meant to be > able to understand the components that make up the software, so to be able > to maintain it and contribute to code base.

thank you for the reply.

</comment></comment><comment><USER3> 1\. First see if you can get the use cases, I.e. what are the requirements for the system. 2\. Choose 1-3 core use cases. Analyse those use cases - Data in / Processing / Data out. 3\. Draw UML diagram of the components in the systems. 4\. Trace each use case end to end with either a debugger or just code reading. 5\. Along the way, draw UML diagram of the class / data structure. 6\. For each class add the core methods where all the business logic resides.

BTW thousands line of code is NOT a big code base.

</comment><comment><USER4> I use debugger to trace it, instead of looking at the source code.

opengrok is also a good tool for searching.</comment>