It's somewhat of an unspoken rule on Reddit that replying to a comment that's more than a day old is a faux pas. The conversation naturally settles within that period – or, less often, within two days. After that, the only appropriate thing is to either reference the conversation, or quote parts of the comments in relation to a similar issue in another post.

On Hubski, conversations could go on for days. It's explicitly stated in the guidelines that it's completely okay to reply to a comment of any age. I've never seen a year-old "revival" do any good, but the fact that it isn't prohibited or frowned upon adds no burden to the user.

How does Tildes handle this? Is there an unwritten rule already? Should there be a written one? What would be the factors?

Today's Feb 13. I've found a post from Feb 2 that was on a subject of interest of mine, where comments were insightful, but I feel like not all questions that need to be asked have been. Surely I won't go about creating another topic just to revive the conversation against only my own commentary to show for it.

There's also the matter of important, (semi)official topics on Tildes. Suppose a new issue arises that concerns an earlier public discussion held, say, half a year ago. It's a minor issue, but one that requires a discussion to settle. Does one comment on the old official topic, or does one create a new topic for this purpose?

Freshly minted user here, so here is a bit of feedback from the first hour of using ~s.

#1

Having topic-info line below the topic-text-excerpt block creates some usability friction, because if the the excerpt is large-ish, then the "xx comments" link is pushed way down, sometimes below the fold.

https://imgur.com/FUwKHo7.jpg

This is an issue (at least for me) because it interferes with efficient selection of topics to read.

You spot a promising topic, you open excerpt, skim through the top part, if it still shows promise, use the "xx comments" link to open it in.

Key point is that I would very rarely read the whole excerpt before deciding to see the comments. However with existing layout the "xx comments" link sits at the very bottom of the excerpt, requiring scrolling down, correcting for an over-shoot (if the link was below the fold) and then zeroing in on the link.

In comparison, if the link were to stay above the excerpt, it will be within few pixels from where my mouse is after clicking on the "open excerpt" triangle.

#2

If this were my site, I would probably just swapped topic-meta with topic-info, like so - https://imgur.com/fJ3tKxc.jpg.

The rationale here is that meta carries information that is less important and less frequently used/needed that topic-info. I know that I would be more interested in the comment count and the topic age than in tags.

#3

The topic-text-excerpt font size is too big. The index is nice, compact and has a very light feel to it. Then you click to expand the excerpt and it's like - WOAH, HERE'S SOME TEXT FOR YOU.

While browsing through the Tildes documentation, I stumbled across this in the Technical Goals section:

Tildes is a website. Your phone already has an app for using it—it's your browser.

Tildes will have a full-featured API, so I definitely don't want to discourage mobile apps overall, but the primary interface for using the site on mobile should remain as the website. That means that mobile users will get access to updates at exactly the same time as desktop ones, and full functionality should always be available on both.

This got me thinking. Despite Tildes preferring mobile browsers over an app, is there still a chance for one? I usually avoid using websites on mobile unless I must, as mobile websites generally don't have the full functionality of the website. Labelling comments 'Exemplary' and 'Malice' on mobile is an example of what doesn't work (there's more), and it's usually very unresponsive for some of the things that still do work. Also, there aren't any notifications on mobile websites and some people, me included, have cumbersome browsers that make the feel of using the website slow and laborious.

Another thing is, if the app has no chance of happening, could Tildes get desktop notifications? I usually like to respond to replies to my topics and comments as quickly as possible and I'm not a fan of the whole 'constant login to check my notifications' thing. Email notifications aren't possible because of Tildes' privacy belief.

I have the "mark new comments" option enabled. Most of the time, it works, displaying "(X new)" under any topics which have had new comments posted since I last looked at it.

However, if the topic is old enough, this "(X new)" notification does not display. The topic is sorted to the top of my feed, because I'm using activity from all-time as my default sort. But it doesn't show "(X new)". I know it has new comments, or it wouldn't jump to the top of my feed, but I'm not seeing that notification.

I don't know how old is "old enough" but it's definitely longer than a month. The topics this is happening to are 3 or 6 months old, but it doesn't seem to happen for topics which are only a few weeks old.

Currently, we can filter posts based on topic tags, is there any chance we could get the same based upon users? Preferably for comments and topics. There are times when I might be interested in a sub-tilde group, but for one reason or another, not a specific user's content in that group. Is this a bad idea?

Just a few minutes ago I moved this topic from ~creative to ~music, but almost immediately began second guessing my decision. I'm not exactly sure where that belongs, because it's music, but it is creative/the OP's original song. What do you think? Is ~creative more for crafts, IE woodworking and the likes, or anything creative done by the OP? Similarly, I can think of more examples for this, such as if someone wants to show off their Raspberry Pi project, do they put it in ~comp or ~creative? Where does it belong?

Disclaimer: I'm not sure if I'm just now noticing something that has always been that way, or if something has actually changed.

Post tags aren't clickable on the main page, or on any group page. I can click on tags inside a topic, but I can't click on tags on the main page.

I feel like I used to be able to do this. I'm pretty sure I must have been able to do this, because I've done some work in the past making tags consistent, and that's how I obtained lists of posts with certain tags.

Has something changed? Or am I imagining things?

Just a few hours ago I was thinking about how much I miss parent links from Hacker News, and now I see that they have suddenly appeared on user pages and in topics. Did Deimos just roll out an update, or have I been blind this whole time?

Designing our countries to accommodate cars as much as possible has been one of the most destructive things to our health, environment, safety and social connectedness. The damage has spread so far and deep that it has reached a crisis point in most developed cities in almost every country. The suburbs we live in are subjected to strict zoning laws baring any form of high density building and any form of mixed zoning. As a result our houses are spaced so far away from each other and from the essential services we need that unless you own a car you are blocked from having a normal life. The main streets full of independent stores and markets have all been killed by megamalls 30km away from where people live with carparks bigger than most park lands. All of this was caused by car usage pushing our societies further and further apart to the point where many people find it acceptable and normal to drive 40km each direction to work each day.

One of the more devastating effects of this urban sprawl is the supermarket has been moved so far away that most people avoid going as much as possible and limit it to a single trip every 1-2 weeks. Fresh food does not last 1-2 weeks which leaves people throwing out mountains of spoiled food that wasn't eaten in time as well as the move to processed foods packed full of preservatives. As well as a shift to people buying dinner from drive through takeaway franchises because their hour long commute has left them with little time to cook fresh and healthy foods.

Owning a car in many countries is seen as the only way to get a job. This locks the poor from ever regaining control of their life because the cost of owning and maintaining a car is higher than most of these people get in an entire year. Our city streets which should be places of vibrant liability have become loud, unsafe and toxic.

Elon and his electric cars solve none of these issues. Electric cars are not the way of the future. They don't even solve air pollution issues entirely because a large part of air pollution is brake pad fibres and tire wear which is proportional to the vehicles weight. And these Teslas are not light.

The only solution is reducing personal vehicle usage as much as possible in urban areas. Of course there will always be some people who will genuinely need vehicles such as in rural areas but there is simply no reason to have the average person drive to and from their office or retail job every day. Its wasteful and harmful in so many ways.

There needs to be a huge push to reclaim our cities and living spaces to bring back the liveability that we could have had. In my city some of the side streets were closed to cars and the change was incredible. Plants and seating filled the spots that would have once been a row of free parking. The streets are filled with the sounds of laughter instead of the roar of motors. The local pubs and cafes have benefited hugely. They didn't benefit at all from street side car parks that were always filled by people who have done 5 laps of the city looking for an empty park and do not intend to shop there.

What is everyone's opinion on this topic and what can we do about it?

With a lot of websites going down the shitter in an attempt to monetize (looking at you, Reddit), I'm wondering where some nice places are online. Nice whether in UI, the community, or really just in general. Below is a small list off the top of my head.

Tildes, because of high quality discussion.

Disroot. It's a slew of useful tools, available for free, while respecting privacy. Genuinely really useful, lots of utilities, good documentation, and a really nice community.

Wikipedia. It's Wikipedia, end of.

Mastodon. This one wholly depends on your instance, but on most(?) the people are nice, and the environment is a lot less argumentative.

Hacker News, high quality discussion over a fair few topics. Very active, too.

By default, no links are underlined in the Tildes interface, as far as I observed. I suggest that we underline the links that are in topic texts and comments. It is a nice visual clue in prose, and allows to distinguish between two consecutive links. Currently I'm using the following snippet in a userscript to achieve that:

// Underline links in prose.
document.querySelectorAll(".comment-text a, .topic-text-full a").forEach(
  function (elem) { elem.style="text-decoration: underline;"; });

The rest of the links function like buttons, so it's not that important (or even unnecessary) that they be underlined. What do you think?

hey everyone!

i don't usually post a lot in general, and when i do its mostly poetry.

but i'm looking for an excuse to procrastinate, and we've got a big emo rap discussion in the 2019 predictions thread going, so I was inspired (and caffeinated) enough to share my top 10 emo rap tracks of 2018 with you all!

enjoy

10. "Get Dressed" x Cold Hart

Music Video

Lyrics

if there's one phrase, brand, collective, namesake that you should be expecting to hear time-and-again over the next few years, it's the "GothBoiClique". the musical collective that brought us Lil Peep is absolutely filled-to-the-brim of other creative, first-moving, and prolific emo-inspired rappers, like our man here, Cold Hart.

where as a good number of popular emo rap songs (XXXTentacion's "Jocelyn Flores" or Juice WRLD's "Lucid Dreams" come to mind) are particularly more sad, sombre, and dark - Cold Hart is a consistent reminder that there is still joy to be found in dark times.

his music typically more inspired by the alternative rock and emo music of the early 2000s, and all the while touching on some sad topics, is more often than not found to be using his music to celebrate life, love, friendship, and the alternative subculture.

"Get Dressed" is a modern emo anthem, and a perfect song to rally the troops of the GothBoiClique. a cute, uplifting song about a guy with a crush, produced by other GBC members Fish Narc and Yawns, and references to Lil Peep's "Hellboy" album is a perfect reflection of where emo is in 2018, and a reminder that GBC is on the rise.

9. "EVERYTHING IS FINE" x scarlxrd

Lyrics Video

Lyrics

this new single from the British up-and-comer "scarlxrd" has been making big rounds in the underground - and been doing great work to hype-up his coming 2019 album, "Infinity."

we've seen screamed vocals begin to make their way into the modern rap scene - most popularly exemplified in songs like "GUMMO" x 6ix9ine, or "Ultimate" x Denzel Curry. scarlxrd has adopted this style, and been one of the biggest proponents of screamed vocals in the underground.

this song shows scar reflecting on a previous relationship, and the current state of his mental health - dripping in emo lyricism, and heavily metal-inspired lyrics

8. "Nike Just Do It" x Bladee

Music Video (your volume is fine - there's just silence at the beginning)

Lyrics

alright, so let's talk about this album really quick.

the name of the artist might sound familiar.

that's because the album that this song was on is Anthony Fantano's #5 worst album of 2018.

give the first 30-60 seconds a listen, and come back. odds are you'll agree - and i really can't argue with that, hahaha.

but - hear me out, because this song is actually pretty important.

Bladee is one of two frontrunners of an emo rap collective in Sweden - most commonly referred to as "Drain Gang". this collective is made up of a few members - Bladee of course, Thaiboy Digital, Ecco2k, Yung Sherm, and a guy named Yung Lean.

the last name might sound a bit familiar, because little Leandoer was actually one of the first people to bring attention to cloud rap, vaporwave aesthetics, and modern emo rap with his releases in 2013 like "Ginseng Strip 2002".

his style and delivery has greatly influenced Bladee, and definitely shows in the cloudy delivery, and emo-influenced lyrics.

i like this song for the same reason that i like the previous one from Cold Hart. yes, it touches on tough subjects. where Cold Hart's track touched on unrequited love from a crush, this track from Bladee touches on deathwishes, drugs, money, and suicide.

but - you pair these themes, the supremely cloudy acid-rap beat, and the lightheared air with which it's all put together - and what you have is a depression-aesthetic song meant to help people just get by, catch a vibe, and have a good time.

what i'm saying, is that this song is the musical equivalent of all of the depression and suicide memes of 2018. things suck, people are broke, people are sad, but damnit life does go on, and we gotta keep on waking up - so we might as well laugh off our own struggle whenever we can.

7. "PPL THT I LUV THE MOST" x 93FEETOFSMOKE

Song

Lyrics

this song was a big surprise to me - and almost nearly didn't come across my ears to make this list! i'd just discovered both this song, and 93FEETOFSMOKE himself a month ago - but on my first listen, i was hooked.

the raw, sad lyrics are painted on top of relatively simple music - almost as a way to make you focus onto what's being said, and how it's being delivered. the half-screamed quarter-sang quarted-spoken-word lyrics are reminiscent of the hardcore rock scene, and bring me memories of songs like "Such Small Hands" x La Dispute and "I Am In Great Pain, Please Help Me" x Crywank

it's songs like this, and a number of others on this list, that give me confidence in the future of emo rap - not solely because of the subgenre's commercial success, or the quick rise in popularity of some of it's more popular artists, but because of how well the essence of emo rock is captured, and exactly how many different areas of emo are drawn from across different artists, albums, and
singles.

6. "Will He" x Joji

from the same man that brought us:

Hair cake (warning: Gross)

Pink Guy - "STFU"

and the Harlem Shake

we have the first major single from rising emo rap artist - Joji.

Music Video

Lyrics

this song is a muted, solemn message to a former lover - peppered with regret, mystery, melancholy, and suicide.

we see the song somehow very bluntly, yet very smoothly pay it's respects to the bi-polar nature of breakups, and the need to take care of oneself, whilst also wanting to still take care of your former partner, the anxiety of wondering if they're in good hands, and the pain of knowing that you cannot ask - that these questions are to remain unanswered.

the music video seems to show the aftermath of a house party gone wrong - a woman in a blood-stained cupid costume on the floor, someone in a panda costume passed out, and Joji - fading and nodding in a bathtub full of blood. in my own interpretation - I would take this to signify the feelings of withdrawal after an important relationship has come to a close.

5. "Lucid Dreams" x Juice WRLD

Music Video

Lyrics

by far the most popular emo rap song of the year, i have to mention Lucid Dreams for it's commercial success, and it's introduction of emo rap to millions of new listeners.

even though it can be an eye-roller, given how much this song gets played at parties, on the radio, in your Spotify recommendeds (you really should get Premium) - this song does deserve attention as being one of the more well-written emo rap songs of the year.

within the realm of emo music, it's very easy to fall into the trap of #imfourteenandthisisdeep as we struggle to find the right words to describe loneliness, anxiety, depression, loss, and the other complex topics that we may find ourselves in the midst in.

one of the reasons this song was so successful, i feel, is because of how absolutely blunt, clear, and to-the-point the lyrics were. it takes no second of meditation to understand lines like

I still see your shadows in my room

I take prescriptions to make me feel a-okay

and

Who knew evil girls had the prettiest face?

these lyrics make the song inherently biting, direct, and most importantly, digestible as the mass market starts to put their headphones on. this was a song written to be inherently relatable, expressed the emotions behind emo music in a modern package, and helped to cement the place of emo rap in the current musical zeitgeist.

4. "In Providence" x Wicca Phase Springs Eternal

Music Video

Lyrics

on the same idea as the previous entry about 93FEETOFSMOKE - this is a track (and an artist as a whole) that very much draws from the emo and metal days of yore.

(fun fact - this song was originally #6 on the list, but my bit of extra research and writeup changed my heart for the better.)

Wicca Phase Springs Eternal, founding member of the aforementioned GothBoiClique, and previous founding member and vocalist of the late 2000s emo band Tiger's Jaw draws very heavily on the emo and gothic superstars of the early 2000s - often referring to groups like Fall Out Boy and My Chemical Romance as major musical influences.

this has led Wicca, throughout his emo rap career, to be a cornerstone of the gothic, and more subtle edges of the alternative. whereas for some, the word "emo" is an aesthetic, with Wicca, it's a lifestyle - the style of which, i feel like, is perfectly captured within this song and it's video.

this song speaks on themes that i feel like we can all relate to (or at least i very much can) - capturing the feeling of a loss of an important relationship, and the feeling of insecurity and concern as you walk about the city in which you both live, carrying about your life, though always looking over your shoulder for unfriendly faces and bad memories.

whether this song will shine as one of the most important emo rap tracks after the genre dies, i'm unsure. however, i think this song very well captures the spirit of emo - both emotionally and musically, and well deserves to be mentioned when we discuss the progression of emo in the future.

3. "Leanin'" x Lil Peep

Song

Lyrics

as we come to close a year of emo rap - it's hard not to mention Lil Peep.

after Gustav's death in late 2017, his fans were nearly foaming at the mouth for unreleased material, and in November, they got their wish with the release of his first posthumous album, Come Over When You're Sober, Pt. 2

this album features a lot of fantastic tracks from peep - such as "Falling Down" ft. XXXTentacion, the more-optimistic-than-usual "Life Is Beautiful", and my personal favorite from the album, "Broken Smile".

however - in light of his passing, none of these songs seem to be quite as harrowing as "Leanin'"

the lyrics feature Peep nodding (the feeling of euphoria and disorientation you may experience on opiates) in his seat, reflecting on someone he misses, and the current state of his life.

peppered with bi-polar lyrics about sex and wanting to scream when you hear someone's name -

and the absolutely chilling verse

Woke up surprised
Am I really alive?
I was tryin' to die last night, survived suicide last night

makes this song a hallmark of the year for me - highlighting the struggle that Peeper felt, how risky he new his lifestyle was, and how much he was ready to give up if it meant him finally being free of the pain he felt.

Rest easy, Gus.

2. "Peach Scone" x Hobo Johnson

NPR Tiny Desk Contest Submission - (Music Video)

Lyrics (the intro changes with every performance. i think it's a cute concept.)

breakout emo rap star Hobo Johnson has had a really big year, with the release of this single, and the growth of attention to his other more-popular tracks "Romeo and Juliet", and "Father" (i'm the new Will Smith!)

our man Frank has seen himself come up on a rise in the underground, as his creative lyricism, inventive instrumentals, and fresh/interesting vocal delivery have gotten the attention of a lot of people inside and outside of the emo rap community. (this aided by the fact that his otherwise bright, bubbly personality has led him to become a bit of a prettyboy in the scene, causing his concerts to be full of sad dudes and girls fawning trying to get a good pic for Instagram. can't say i blame them. he's a cute fella.)

but on the important musical side of things, i love the fact that his lyrics seem to be striking and raw, without being hyper-simplistic. his delivery comes across as raw and pained - without being aggressive or dark. and most importantly, he touches on topics and feelings of anxiety that i feel like we all experience every now and then - but as we grow older, have come to ignore or simply accept as a "part of life" or a "part of the way the world works". with peach scone, we see Frank finding himself smitten with a girl already in a happy, committed relationship - and his struggles of smiling and offering her support, whilst also trying to hide the face that any time he sees this girl,

he's absolutely

smitten

and then the courage builds up inside of him and he cant help but turn to her and admit the fact

that he

loves

...
.

...peach scones.

1. "Train food" x XXXTentacion

and here at number one - we have my personal favorite track off of Jahseh's first posthumous album, "Skins".

Song

Lyrics

this was a very interesting song. and, in the same vein of the song from Peep, very harrowing as it looks forward heavily discussing the topic of death, and it's inevitable nature.

this is not a recanting of a moment in Jahseh's life, or a metaphor expressing some deeper ideas of life/death/pain.

rather, this is a bit of a concept song, meant to tell a story of a boy walking home, as he comes nearby a train track, and meets a man who turns out to be Death.

the delivery, style, and message of the song are very reminiscent of his earlier song "I spoke to the devil in miami, he said everything would be fine" (Song/Lyrics)

this song shows X walking home with his head down as he comes across a man - presumed to be Satan, who stops him for a quick chat.

wanting to avoid confrontation and not wanting to talk, X changes directions, only to be cornered by the weaponless man around every corner. there was no escape.

they begin to "talk" as X is reminded of his history of self-harm, and the life of hardship he'd lead until his recent acquisition of an audience, a change of heart, and financial success.

then we hear X attacked, and bound to the rails of a train track - calling out to God for help and hearing nothing, feeling abandoned, as he knows death inevitably waits around the corner.

almost as if he could see the murder coming just months in the future.

not only is this track absolutely chilling, but it's also a phenomenal use of music to tell a compelling story. we've seen that X has the capacity to create the mindless/empty trap bangers like "Look At Me!" or "#ImSippinTeaInYoHood" - but he instead chooses to use his platform to push the boundaries of what today's rap fans listen to, using his influence to open his fans up to the idea of concept-music and musical storytelling, and to show that he was, above all else, an artist looking for a platform, looking for self-expression, and looking to lose himself in his art.

Long Live Jahseh.

(oof)

TRAN-

As evidenced by recent topics, most people are unhappy with the direction the smartphone industry has taken in recent years. As more unnecessary features and sacrifices are made with each passing generation of handsets, what components are essential in your ideal smartphone? Create one in the comments.

Here is mine, in no particular order:

• Optimized Stock Android
• Gesture-based navigation (think iPhone X)
• Removable matte black plastic back
• 2:1 Aspect ratio, 5.6" diagonal AMOLED display
• Dual front-facing speakers in top and bottom bezel
• Dual front facing cameras (Wide Angle and Standard)
• Bezel-less sides
• Dual back cameras, with OIS (Wide Angle and Standard)
• USB-C
• 3700 mAh removable battery with Fast Charging+Qi
• Snapdragon 855
• Apple-esque Face Unlock
• ~$750 price tag

Intro

Hello everyone.

Due to @Kat’s ever-failing health, I will be analyzing the data instead of her this time around. If you have no idea what this is about, see the demographic survey that was posted on the day of Tildes’ half-year birthday. She’s done this before, so let’s see what's new.

The original survey was answered by 404 people, while the half year survey was answered by 293. Though the total number of replies was lower, the completion rate was actually higher: 293 responses from 422 unique visitors, or 69.4%, up from the first year’s 404/599=67.4%. The decrease in answers is most likely attributed to the change of the default sort from “Activity, all time” to “Activity, 3 days”: the response rate held fairly consistent for the first three days, then plummeted after the third as the topic stopped being able to gain any publicity. Though response rates on the original were not high after the first three days, there was a steady trickle up until the survey stopped accepting responses.

While the numbers are relatively big (for a community of this size), do take anything found with a healthy dose of scepticism. Even though the original dataset she shared with me does not contain any identifiable information (all I can see are randomly-generated user strings) the specifics of that data will not be posted, as was mentioned during the original survey. This is because I am unable to be certain I can sufficiently anonymize it. Typeform has created a summary of the data on a per-question basis with substantially more datapoints than this thread, which you can find https://themeerkat.typeform.com/report/H2TtYg/rVf75AqbKaPncy6y.

Explanation

I will compare the statistics with a similarish reference set based on the six most common territories, all of which are above one percentage of the survey answers. That means when I compare on the general populace, I will base it on numbers from USA, Canada, UK, Australia, the Netherlands, and France.

This means it will be weighted like this:

I’ll clean up my data sheet and post it in the comments later. You all are absolutely encouraged to fix it because it will most likely contain errors.

The interesting stuff

What has changed in the first half year?

Age

This time around an age range was used instead of an exact numerical input, but if we were to assume that everyone is aged in the middle of their age range (so 20 for 18-22 year olds, for instance), the average age of a user would be 26.84 years, or 26 years, 9 months, and 4 days old (roughly). So we’ve grown a bit younger than last year, on average.

Gender and identity

Gender distribution seems to be roughly the same. We see a small decrease in percentage of heterosexuals, divided roughly evenly on the remaining categories. We also see a significant increase in the amount of transgender users, but since the amount reported is small, that could also just be statistical noise. The percentage of polyamorous people has remained exactly the same. For pronouns, there are only three users who prefer it/its, and zero who prefer any neopronoun set: every “Other” was offering commentary on the question rather than answering it. Similarly, almost all of the “Others” for orientation were expressing that they didn’t understand the specifics of the options given.

All in all, little has changed.

Territorial

In both surveys, three options dominated: the USA, the UK, and Canada. On that end, little has changed, though it seems that all of the Swedes disappeared, with zero answering the half year survey as compared to eight for the first one. Wonder what they’ve been busy with.

Native language

Unsurprisingly, about everyone speaks English. What is more surprising is the lack of native multilinguals: fewer than 6% of Americans who natively speak English also natively speak a second language. For comparison, that’s 10% for Australians, 21% for Canadians, and 13% for the UK. This represents an overall decrease in geographic diversity, with users coming from 36 different countries as compared to 42 the first time.

Religion

Compared to the world at-large, we sure are a god-denying folk. A whopping 52% of us consider ourselves atheists, whereas the sample data puts it at 12.1%, so we’re far from the norm of our fellow citizens.

We got a few interesting answers in the “other” section of the religion part of the survey. We got a few interesting ones I had never heard of before, like “Discordian”. But generally speaking, around half of them were either “none” or one of the actual options. Two stood out to me though.

To the one Chinese user who filled it in as “The heck is chinese traditional”: I have no idea either.

To the one Australian user who wrote “Left-hand path Heathen”, you be yourself, mate.

Politics

The average has barely moved in the last half year—we’re still slanted very much to the left. Unlike the first survey, there was no freeform input this time around, so the specifics are hard to discuss.

Computers

We have seen a drastic fall in the percentage of Windows users. It was at 60%, and is down to 43%. Nearly all of this has gone to Linux, which is now at 38%. That’s quite large, especially compared to the reference data, which has Linux use among web users at 1.23%. It’s like a herd of penguins in here.

Mobile phones

Compared to half a year ago, not many of us have switched mobile OS. Compared to the calculated data, we like Android slightly more than average. 62% vs 72%.

Not much interesting in the “other” section, though I will give a salute to the one American user still holding out on Windows 10 Mobile.

Work

We have a pretty even distribution with three exceptions. “Computer software”, “Never employed”, and “IT”. Nearly 3/4 who answered “Never employed” are currently students.

Among the students, we only have one student that proudly smokes and has no interest in quitting. The campaigns seem to be working.

Tildes usage

If we look at the users who visit Tildes multiple times per day, we see a few interesting trends. Nearly all of them use Android, and nearly all of them are employed. Beyond that it all seems surprisingly… average.

Overall, people rated Tildes as a platform as-it-stands a 5.7/7 (0.81), and their optimism for the future of the site at a 5.4/7 (0.77). The most important reason they use the site (of the options given) is “Minimal, fast design” at a 4.6/5 (0.92), with “Privacy-consciousness and lack of trackers” right on its heels. 20.8% of users have ever contributed money to Tildes (surprisingly high, compared to most donation campaigns), with about half as many making a recurring donation.

Despite @Kat’s insidious attempt to influence the data, “waves” as a demonym only received 5.5% of the vote. The leader for that, overwhelmingly, is “no demonym at all”, with a combined 49% of the votes and 18.5% of respondents strongly preferring the site not to have a demonym. Second place, the generic “users”, only has 15.8% in comparison. The first Tildes-specific demonym present is Tilders/~​rs, with 13.4%.

Most notably, about ⅔ of users would prefer Tildes to be remain invite-only long-term.

Freeform questions

The survey had three freeform questions: “What do you like most about Tildes, thus far?”, “What do you like least about Tildes, thus far?”, and “What is the most pressing missing feature/‘pain point’ for you about Tildes in its current state?” All the comments fill over 30 pages, so it seems like we really have a lot to say. You can download and look at all of the raw answers here, if you’d like. They’ve been shuffled to ensure privacy.

Likes

A large majority of the comments boil down to “a quality of discussion where disagreement is discussed in a respectful and level-headed way”. A very significant amount also point out the lack of “low effort content and trolls” as a good thing. A significant amount also mention the simple and quick-loading interface. We also have one user who believes he can find a twerk team on Tildes.

So on this, @Deimos can feel proud for what he has done. Though you know what really makes the site good? There is one comment that properly gets it: “The people, d’awwww.”. Yes, that includes you.

Dislikes

But not everything is perfect, though negatives about Tildes seem to be a lot less unanimous than the positives. There are a few that repeat a bit more often than others: the biggest one is “left centrism in discussions” or “echo chambers”, though in a close second, as with any political discussion, is its exact opposite with complaints about “too much discussion about left-centrism in discussions”—notably, though, in the question “Do you feel as though Tildes has a good mix of political opinions, for your personal preferences?”, the leading answer was “Yes” with 63%. A small amount of users also think we have too many software developers.

Beyond that, the main complaint that stands out is “lack of users and content”, which I am sure will improve in time.

Missing feature/pain point

This too is very varied. A lot of the comments are actually about features that have been introduced since the survey was done, like bookmarking. Honestly, it’s not that many complaints compared to just likes and dislikes.

The “majority” seem to be on a lack of tag autocompletion, USA-centrism, and the lack of a mobile app.

There was one more section: “If you would like to offer any long-form commentary, criticism, or feedback regarding Tildes, you may do so here.” Due to its nature, I’ll let you read through them yourself in the raw data, if you’re interested.

Closing words

First of all, to everyone who took the time to answer: thank you! I hope this post and the survey has brought some fun to everyone. If there’s an interest, I am sure that Kat, myself, or someone else will make another one at the one year anniversary. We already got some feedback in the previous thread, but we’re always open for more.

I will do some additional data comparisons on request. I might be a bit occupied this weekend, though, so that will come when it comes.

Hey! Despite the seemingly negative name, I want to make this thread so anyone can say pretty much whatever you want about the games you've been playing! Whether it's a review, a brief paragraph or two of thoughts, recommendations, or frustrations, let's try to commiserate or proliferate discussion about what we've been playing!

This week let's share some of those favorite tracks that you don't usually advertise to other people - the guilty pleasures. The ones that tend to make music critics and other music lovers cringe, and garner raised eyebrows from your friends and family. We've all got them hiding in our playlists.

Thanks @ainar-g for the topic suggestion. Feel free to suggest topics for upcoming threads in the comments, and happy listening. :)

Last week's thread on uplifting earworms.

Attaching politics to a topic they wish to squelch. That effectively “controversializes” the issue and divides public opinion so that no more than half of people will typically believe or pay attention to the offending information.

https://thehill.com/opinion/campaign/405807-a-news-consumers-guide-to-astroturf-sources

Preface

Different projects have different use cases that can ultimately result in common solutions not suiting your particular needs. Today I'm going to diverging a bit from my more abstract, generalized topics on code quality and instead focus on a specific project structure example that I encountered.

Background

For a while now, I've found myself being continually frustrated with the state of my project configuration management. I had a single configuration file that would contain all of the configuration options for the various tools I've been using--database, API credentials, etc.--and I kept running into the problem of wanting to test these tools locally while not inadvertently committing and pushing sensitive credentials upstream. For me, part of my security process is ensuring that sensitive access credentials never make it into the repository and to limit access to these credentials to only people who need to be able to access them.

Monolithic Files Cause Monolithic Pain

The first thing I realized was that having a single monolithic configuration file was just terrible practice. There are going to be common configuration options that I want to have in there with default values, such as local database configuration pointing to a database instance running on the same VM as the application. These should always be in the repo, otherwise any dev who spins up an instance of the VM will need to manually tread documentation and copy-paste the missing options into the configuration. This would be incredibly time-consuming, inefficient, and stupid.

I also use different tools which have different configuration options associated with them. Having to dig through a single file containing configuration options for all of these tools to find the ones I need to modify is cumbersome at best. On top of that, having those common configuration options living in the same place that sensitive access credentials do is just asking for a rogue git commit -A to violate the aforementioned security protocol.

Same Problem, Different Structure

My first approach to resolving this problem was breaking the configuration out into separate files, one for each distinct tool. In each file, a "skeleton" config was generated, i.e. each option was given a default empty value. The main config would then only contain config options that are common and shared across the application. To avoid having the sensitive credentials leaked, I then created rules in the .gitignore to exclude these files.

This is where I ran into problem #2. I learned that this just doesn't work. You can either have a file in your repo and have all changes to that file tracked, have the file in your repo and make a local-only change to prevent changes from being tracked, or leave the file out of the repo completely. In my use case, I wanted to be able to leave the file in the repo, treat it as ignored by everyone, and only commit changes to that file when there was a new configuration option I wanted added to it. Git doesn't support this use case whatsoever.

This problem turned out to be really common, but the solution suggested is to have two separate versions of your configuration--one for dev, and one for production--and to have a flag to switch between the two. Given the breaking up of my configuration, I would then need twice as many files to do this, and given my security practices, this would violate the no-upstream rule for sensitive credentials. Worse still, if I had several different kinds of environments with different configuration--local dev, staging, beta, production--then for m such environments and n configuration files, I would need to maintain n*m separate files for configuration alone. Finally, I would need to remember to include a prefix or postfix to each file name any time I needed to retrieve values from a new config file, which is itself an error-prone requirement. Overall, there would be a substantial increase in technical debt. In other words, this approach would not only not help, it would make matters worse!

Borrowing From Linux

After a lot of thought, an idea occurred to me: within Linux systems, there's an /etc/skel/ directory that contains common files that are copied into a new user's home directory when that user is created, e.g. .bashrc and .profile. You can make changes to these files and have them propagate to new users, or you can modify your own personal copy and leave all other new users unaffected. This sounds exactly like the kind of behavior I want to emulate!

Following their example, I took my $APPHOME/config/ directory and placed a skel/ subdirectory inside, which then contained all of the config files with the empty default values within. My .gitignore then looked something like this:

$APPHOME/config/*
!$APPHOME/config/main.php
!$APPHOME/config/skel/
!$APPHOME/config/skel/*
# This last one might not be necessary, but I don't care enough to test it without.

Finally, on deploying my local environment, I simply include a snippet in my script that enters the new skel/ directory and copies any files inside into config/, as long as it doesn't already exist:

cd $APPHOME/config/skel/
for filename in *; do
    if [ ! -f "$APPHOME/config/$filename" ]; then
        cp "$filename" "$APPHOME/config/$filename"
    fi
done

(Note: production environments have a slightly different deployment procedure, as local copies of these config files are saved within a shared directory for all releases to point to via symlink.)

All of these changes ensure that only config/main.php and the files contained within config/skel/ are whitelisted, while all others are ignored, i.e. our local copies that get stored within config/ won't be inadvertently committed and pushed upstream!

Final Thoughts

Common solutions to problems are typically common for a good reason. They're tested, proven, and predictable. But sometimes you find yourself running into cases where the common, well-accepted solution to the problem doesn't work for you. Standards exist to solve a certain class of problems, and sometimes your problem is just different enough for it to matter and for those standards to not apply. Standards are created to address most cases, but edge cases will always exist. In other words, standards are guidelines, not concrete rules.

Sometimes you need to stop thinking about the problem in terms of the standard approach to solving it, and instead break it down into its most abstract, basic form and look for parallels in other solved problems for inspiration. Odds are the problem you're trying to solve isn't as novel as you think it is, and that someone has probably already solved a similar problem before. Parallels, in my experience, are usually a pretty good indicator that you're on the right track.

More importantly, there's a delicate line to tread between needing to use a different approach to solving an edge case problem you have, and needing to restructure your project to eliminate the edge case and allow the standard solution to work. Being able to decide which is more appropriate can have long-lasting repercussions on your ability to manage technical debt.

I was looking for preferences on 120/140mm case fans. RGB is a want, but not at the expense of quality fans.

I'm pretty new to the topic and not super familiar with the technical side. So open to reading more in depth too.

Thanks!

Intro

Hello everyone,

Today we cover entropy and the heat death of the universe.

The previous chapters can be found here and here. While I recommend you read both, you should at least read the first part and skim the second.

A collection of all topics covered can be found here: https://tildes.net/~tildes/8al/.

Subject

Intro

Entropy describes how chaotic a system is. In thermodynamics, chaos is created from an irreversible process. We are all sort of familiar with this concept. A broken cup will not unshatter itself. As a consequence of how our universe works, (net) chaos can only increase. And this might have far reaching consequence, if we look at the effects of entropy on a cosmic scale.

Entropy

Entropy describes an amount of irreversible chaos.

But first, let's cover cycles super quickly. In thermodynamics, a very important concept is a "cycle". A cycle is a repeating process, that returns to its initial condition. For instance, when we ride a bike. We're turning our feet around the crank shaft. Repeatedly returning to the same position we started from. As we push on the pedal, some of our work is lost and turned into heat. Primarily due to friction from the wheels and from the different mechanical parts.

A cycle that wastes no energy is called a reversible cycle. That would mean 100% of the work in a cycle (even the work that is turned to heat) has to be returned in some way to its original state. The most famous example of this is the Carnot heat engine.[1] But in reality, the Carnot heat engine is nothing more than a theoretical engine. As we remember from before, we cannot turn 100% of heat back into work. So any heat engine, be it a car's motor, a refrigerator, a star, or the human body, will in some way contribute to this irreversible chaos.

Now what about entropy? If we look at entropy at the molecular level, it all becomes a bit abstract. But we can think of this concept with bigger building blocks than molecules, and still be close enough. Say you have a brick house with orderly layed bricks. This house would love to come crashing down. And lets imagine it does. When the house lays in ruins, it is not likely to suddenly "fall" into the shape of the house again. So if the house has collapsed, our system is in a higher state of chaos. Our entropy has increased. And unless we supply work to the system (and waste energy trough heat), we will not get the brick house back.

So now we understand, that on the grand scale of the universe, entropy will only increase.

The heat death of the universe

But what are the consequences of this? Imagine entropy going on for billions and billions of years. Everything in the universe slowly reaching a higher state of chaos. Everything that is orderly, turns into chaos. All high quality energy has turned into low quality energy. Everything has been wasted and turned into heat. Everything ripped apart until you are left with nothing to rip apart. At this point, there is no interactions between molecules any more. Everything has reached absolute zero temperature.

At this point, entropy is at its absolute maximum. And we have reached entropic equilibrium.

This is the heat death of the universe.

Afterword

Of course, the heat death of the universe is just one of the many theories about the end of the universe. It assumes that thermodynamics properly describes the universe, and that there are no hidden surprises.

Frankly told, it's the best bet we have with our current knowledge. But we still know so little. So I would not panic just yet. Alternatively, this is where we could continue with "an engineer's perspective on existensial nihilism". But I think that this is something better reserved for later, and better presented by someone else.

We have covered what I consider the absolute minimum of thermodynamics, that still gives us a basic understanding of thermodynamics. There are of course a lot of other topics we could cover, but thats it for now. I will potentially write an appendix later with some questions or things that have been asked.

But for now, that's it. Questions, feedback or otherwise?

Notes

[1] The Carnot heat cycle is a bit beyond the level of what we have discussed so far. It describes a system where heat is supplied and removed to have a piston expand and contract without any energy becoming waste heat.

Some people have mentioned they'd like to have some sort of weekly track-sharing thread, so let's have a little fun and find some good music in the process.

Everybody's got that playlist somewhere with all of your favorite earworms - the songs you put on repeat to the point where you annoy the hell out of everyone else in the room because you love them so much. Let's collect some of those earworms here and see what we can come up with.

In particular, let's go for the uplifting kind - feel good music. When the thread settles down I'll pull these all together in a nice playlist and share that here as a separate link submission.

Any time period, any genre, any style, popular, obscure, or even your own music, it's all good - just as long as it's positive energy and you can't stop spinning it. If you're on mobile, don't worry about making it into links, others can linkify it for you (and eventually, Tildes can do that automatically to make this all easier in the future). Share as many as you've got. If you've already got a playlist like this for yourself, you can share that too. ;)

Oh, and don't worry about nebulous 'standards' or if people will like it. If you like it, that's all that matters. Don't overthink it!

Edit: Almost forgot, feel free to make suggestions for the topics of upcoming share threads in the next few weeks!

I have poor vision and I rely heavily on a Firefox plugin called Stylus to make websites readable - in particular the trend for low contrast and small text. That includes Tildes.

I updated it to v1.5.0 and now the styles I set for Tlldes no longer work - most other sites still appear to work but I've not checked them exhaustively.

I immediately tried rolling back a release or two (1.4.23 and 1.4.22) but those versions no longer work for any site. I tried randomly downgrading to even older versions but the same result. I think I'm stuck with the latest version..

I notice in the browser console there are 2 errors reported on Tildes e.g. on this page I see:

Content Security Policy: The page's settings blocked the loading of a resource at inline ("script-src"). new_topic:1:1
Content Security Policy: The page's settings blocked the loading of a resource at inline ("style-src"). new_topic:1:1

Using the Firefox Developer tools Inspector - I see my style settings for Tildes injected by Styuls (after the body) but they do not work any more.

Since only Tildes so far is not working with my Stylus settings I guess there is also a recent change to Tildes that is causing Stylus to fail.

This is a rather serious issue for me as all the colour options in the setting are low contrast and cause eye strain which becomes painful without the Stylus settings.

Thanks for any help you can offer.

Introduction

I want to give an introduction on several physics topics at a level understandable to laypeople (high school level physics background). Making physics accessible to laypeople is a much discussed topic at universities. It can be very hard to translate the professional terms into a language understandable by people outside the field. So I will take this opportunity to challenge myself to (hopefully) create an understandable introduction to interesting topics in modern physics. To this end, I will take liberties in explaining things, and not always go for full scientific accuracy, while hopefully still getting the core concepts across. If a more in-depth explanation is wanted, please ask in the comments and I will do my best to answer.

Previous topics

Bookmarkable meta post with links to all previous topics

Today's topic

Today's topic is the dual nature of light and matter, the wave-particle duality. It is a central concept in quantum mechanics that - as is tradition - violates common sense. I will first discuss the duality for light and then, in the next post, for matter.

The dual nature of light

In what terms can we think of light so that its behaviour becomes understandable to us? As waves? Or as particles? There are arguments to be made for both. Let's look at what phenomena we can explain if we treat light as a wave.

The wave nature of light

Let's start with an analogy. Drop two stones in a pond, imagine what happens to the ripples in the pond when they meet each other. They will interact, when two troughs meet they amplify each other, forming a deeper trough. When two crests meet they do the same. When a crest and a trough meet they cancel out.

Now if we shine light through two small openings and observe the resulting pattern, we see it's just like ripples in a pond, forming an interference pattern. When looking at the pattern formed on a screen placed at some distance from the openings, we see a striped pattern Light can be described as an electromagnetic wave, with crests and troughs. It sure seems like light is wavey! The wave nature of light allows us to describe phenomena like refraction and diffraction.

The particle nature of light

When we shine light on some metals, they will start tossing out electrons. This is called the photoelectric effect. How can we understand this process? Well we know light is a wave, so we imagine that the wave crashes into the electron that is chilling out near the surface of the metal. Once the electron has absorbed enough of the light's energy it will be able to overcome the attractive forces between itself and the positively charged atom core (remember, an electron has negative charge and so is attracted to the atom cores). So a higher intensity of light should make the electron absorb the required amount of energy more quickly. Easy, done!

However, there's something very peculiar going on with the photoelectric effect. If we shine low frequency light on said metal, no matter how intense the light, not a single electron will emerge. Meanwhile if we shine very little high frequency light on the metal, no matter how low the intensity, the electron will emerge. But how can this be? A higher intensity of light should mean the electron is receiving more energy. Why does frequency enter into this?

It seems that the electron needs a single solid punch in order to escape the metal. In other words, it seems it needs to be hit by something like a microscopic billiard ball that will punch it out of the metal in one go. The way physicists understand this is by saying light is made up out of particles called photons, and that the energy a photon carries is linked to its frequency. So, now we can understand the photoelectric effect! When the frequency is high enough, the photons in the light beam all individually carry enough energy to convince an electron to leave the metal. When the frequency is too low, none of the photons individually can knock an electron out of the metal. So even if we fire a single photon, with high enough frequency, at the metal we will see one electron emerging. If we shine low frequency light with a super high intensity at the metal, not a single photon will emerge.

So there you have it! Light is made out of particles. Wait, what? You just told us it's made out of electromagnetic waves!

The wave-particle duality of light

So, maybe light is just particles and the wave are some sort of emerging behaviour? This was a popular idea, one that Einstein held for some time. Remember the experiment where we shone light through two small openings and saw interference (commonly known as the double slit experiment)? Let's just take a single photon and shoot it at the openings! Because light is particles we'll see the photon just goes through either opening - like a particle would. Then all the non-believers will have to admit light is made out of particles! However, when we do the experiment we see the photon interfere with itself, like it was a wave. Remember this picture which we said was due to wave interference of light? When a single photon goes through the openings, it will land somewhere on the screen, but it can only ever land in an area where the light waves wouldn't cancel out. If we shoot a bunch of photons through the openings one at a time, we will see that the photons create the same pattern as the one we said is due to wave interference!

Implications

So it would seem light acts like a particle in some cases, but it acts like a wave in some others. Let's take a step back and question these results. Why are we trying to fit light into either description? Just because it's convenient for us to think about things like waves and particles - we understand them intuitively. But really, there is no reason nature needs to behave in ways we find easy to understand. Why can't a photon be a bit wavey and a bit particley at the same time? Is it really that weird, or is it just our intuition being confused by this world we have no intuitive experience with? I would love to hear your opinions in the comments!

Observing photons

To add one final helping of crazy to this story; if we measure the photon's location right after it emerges from the slit we find that it doesn't interfere with itself and that it just went through a single slit. This links back to my previous post where I described superpositions in quantum mechanics. By observing the photon at the slits, we collapsed its superposition and it will behave as if it's really located at one spot, instead of being somehow spread out like a wave and interacting with itself. The self interaction is a result of its wavefunction interacting with itself, a concept that I will explain in the next post.

Conclusion

We learned that light cannot be described fully by treating it simply as a wave or simply as a bunch of particles. It seems to be a bit of both - but neither - at the same time. This forces us to abandon our intuition and accept that the quantum world is just fundamentally different from our every day life.

Next time

Next time we will talk about the dual nature of matter and try to unify the wave and particle descriptions through a concept known as the wavefunction.

Feedback

As usual, please let me know where I missed the mark. Also let me know if things are not clear to you, I will try to explain further in the comments!

Addendum

The photoelectric effect is actually what gave Einstein his Nobel prize! Although he is famous for his work on relativity theory he was very influential in the development of quantum mechanics too.

I've posted a few lengthy topics here outside of programming challenges, and I've noticed that the ones that seem to have spurred the most interest and generated some discussion were ones that were directly related to code quality. To avoid falling for confirmation bias, though, I thought I would ask directly.

Is there generally a greater interest in code quality discussions? If so, then what kind of things are you interested in seeing in those discussions? What do you prefer not to see? If not, then what kinds of programming-related discussions would you prefer to see more of? What about non-programming discussions?

Also, is there any interest in an informal series of topics much like the programming challenges or the a layperson's introduction to... series (i.e. decentralized and available for anyone to participate whenever)? Personally, I'd be interested in seeing more on the subject from others!

Intro

Hello everyone,

Today we cover equilibriums and phase changes. Through that we will get a basic understanding of how things like pressure, temperature, density, volume, etc. are related.

The previous chapter can be found here: https://tildes.net/~science/8ao/. I highly recommend that you read it before continuing.

A collection of all topics covered can be found here: https://tildes.net/~tildes/8al/.

Subject

Summarized

"Equilibrium" is fancy word for "balance". A system is in equilibrium when it is in balance with the surrounding systems. Any system will naturally attempt to be in equilibrim, and will adapt its physical properties to do so.

A phase change is the transition of matter from a state (solid, liquid, gas, or plasma) to a different state. This happens due to a change in internal energy, changing how a material is bonded.

Now that we have it summarised, lets dig a bit deeper.

Equilibrium

A system always tries to be in balance with its surrounding systems. We maybe don't think about this a lot, but we are all very familiar with this principle since we observe it every day.

If you have a cup of hot cocoa, it will cool down until it has reached ambient temperature. At this point, the cocoa is considered to be in "thermal equilibrium". If we fill a balloon with air, it will expand. It will do so until the air inside the balloon has the same pressure as the air outside the balloon. At this point, the balloon is considered to be in "barometric (pressure) equilibrium".

Just like when we talk about energy, there is a relationship when we talk about equilibriums. We have something we call (you may remember this from basic chemistry) an "ideal gas". An ideal gas is a good way of looking at this principle. Since the temperature, volume and pressure have a direct relationship.

Pressure-volume-temperature diagram for ideal gases.

In the diagram above we can see that if we change one of the three variables, then one (or both) of the other two variables has to change too. For instance, if we heat some air in a canister, the air will try to expand. But being unable to change in volume, it will instead increase pressure. [1]

Phase changes

Any material has a set of phases. The ones we'll discuss are the solid, liquid and gaseous phases. Unless we control the material's environment very carefully, materials will always follow this order when energy is added. Solid becomes liquid, liquid becomes gas, and vice versa. For instance water; ice (solid) becomes water (liquid), water becomes steam (gas). So each of these transformations is a phase change.

So when water is solid (ice), the molecules are in a grid. The molecules do not move around much, maybe a little bit where they stand. But they all still stand in a grid.

When the water gets heated up, the molecules will start to move. Molecules have a natural attraction to each other due to subatomic forces like the van der Waals force. So the molecules will no longer stay in a grid, but they will still keep each other close due to this attraction. So a material that sticks together but freely moves around is called a liquid.

Once the material overcomes this natural attraction, the molecules can go anywhere they want. And that's when we get a gas. Or steam, in the case of water. All of this applies even for materials we don't usually imagine would melt or evaporate, for instance steel.

Here is a visual representation of the three states.

Now comes the fun part. Ice is water that is at 0 degrees Celcius or below. Liquid water is water that is 0 degrees and above. But wait! Does that mean that water can be both solid and liquid at the same temperature? Yes, indeed. A material requires a certain amount of internal energy to become liquid. That is why internal energy and temperature is often used interchangeably, but is not exactly the same.

The water molecules in ice will use the supplied energy to get excited and start moving around. This continues until the solid-liquid water reaches a point where all molecules move around. At that point it has completely become a liquid. While water is in solid-liquid state, the amount of internal energy dictates how much is liquid and how much is solid. The exact same thing happens with water at 100 degrees. It can be steam or liquid, but not fully either until it reaches a certain amount of internal energy.

Here is a diagram of this process.

Another fun tidbit that makes water special: Water has a lower density as a solid than it has as a liquid, when both are at 0 degrees Celcius. This means that per unit of volume ice weighs less than (liquid) water. Therefore ice floats on top of water. This is the only material that behaves in this way. And thats extremely important to our existince, since it helps regulate heat in the ocean.

Steam engines (and implication)

We have learned a few new things today. But there is one really important wrinkle to all of this. A system always will try to be in balance. And this we can exploit. Pressure is a type of "pushing". So thats a type of work! And an increase in thermal energy can lead to an increase in temperature. We remember that from the ideal gas. So if we cleverly organize our system, we can create work from heat! This is the basis behind most heat engines (simplified a ton). We supply thermal energy to some gas or fluid, and extract work from this gas or fluid.

A classical example is the steam engine. We have water inside a closed system. When we heat up the water, it will turn into steam. And this steam will want to be much less dense than water. As a consequence, the pressure inside the water tank increases drastically. We release a small amount of this steam into a closed piston.

Here is an animation of this in action.

The piston suddenly gets a high pressure level. As we remember, it will want to be in equilibrium with its surroundings. Currently the pressure inside the piston is much higher than outside the piston. As we remember from the ideal gas law, a higher volume will mean a lower pressure. So the piston will be moved, as the steam expands to reach a pressure balance. The movement from the piston will drive something, like a wheel. The steam is removed from the expanded piston, and the piston will return to its closed position.[2] Then the process is repeated again and again, to have the piston continously move something.

All that from a bit of water in a tank and some supplied heat.

Whats next?

Next time we will talk about another important property. Entropy! In the previous topic I had a lot of questions regarding the quality of energy types, and what specifies heat from work on an intrinsic level. Entropy is the big answer to this. From that we will also cover the heat death of the universe, which would be a good introduction to "a laypersons introduction to nihilism" if we have any philosophers here.

Note

[1] For solid and fluid materials (as well as non-ideal gassess) this becomes a lot more complicated. If we ever do a "layperson's intro to fluid mechanics" we will cover it then.
[2] This described design is very inefficient and very simplified. Usually the piston is made so steam is supplied in turns supplied to either side of the piston. Then the work will both removed the steam that already performed work as well as move the piston. That way you can have continous movement in both directions.

See for instance this image.

I'd love to hear about how you create your favorite works. Of anything. How did you write your best music? How did you create your favorite character in a story you wrote? Anything of the sort.

I'd love to hear all the different processes people have. It's really quite an interesting topic of discussion, for me.

Personally, I grab a cup of coffee and listen to instrumental music (mostly avant-garde jazz [Coltrane, Washington, etc]) while creating the world of the story I'm writing. There's something very productive-feeling about being wired on caffeine while also having a constant noise in your ears. It's how I compose some of my better characters and settings.

Due to my constant writer's block phenomenon, sometimes I'll smoke some pot to get past it. It's almost like phasing through a wall you can't jump over. There's something lifting about it.

Deimos and I were discussing the use of "ask" topic tags this week, and we agreed it might be a good idea to get a consensus on these.

At the moment, Tilders are using four "ask" tags on topics:

• ask

• ask.survey

• ask.recommendations

• ask.help

(There may be more "ask" tags created in the future, but these four are what we're all using at the moment.)

Anything that's a question gets tagged with "ask". Some specific types of question will then get tagged with "ask.survey" or "ask.recommendations" or "ask.help", depending in the type of question being asked.

• "ask.survey" is for questions about preferences and favourites. "What's your favourite horror movie?" "What's the best place you ever visited?" "What's your favourite type of holiday?" The asker is collecting data about people's likes and dislikes (even if they're not going to publish the results in a report later!).

• "ask.recommendations" is for questions asking for recommendations. "What's a good browser to use?" "What book should I read next?" "Which brand of phone should I buy?" The asker is looking for people to recommend things to them.

However, Deimos and I wondered about "ask.help". One interpretation we came up with was that "ask.help" is for questions looking for a specific answer, where it should generally be possible for people to think "yes, this is the right answer to the question". This would include questions seeking help learning about an academic topic, such as happens in /r/AskScience and /r/AskHistorians over on Reddit. Another interpretation we came up with was that "ask.help" is for questions looking for guidance on doing something, like a "how to" type question. This would be more like the types of questions in /r/Help and like the Help menus in software and the F1 key - helping people get things done.

What do you think about the "ask" tags? In particular, what should the "ask.help" tag be used for? In general, are the existing "ask" tags okay? Do we need more "ask" tags? Do we need different "ask" tags?

Introduction

I want to give an introduction on several physics topics at a level understandable to laypeople (high school level physics background). Making physics accessible to laypeople is a much discussed topic at universities. It can be very hard to translate the professional terms into a language understandable by people outside the field. So I will take this opportunity to challenge myself to (hopefully) create an understandable introduction to interesting topics in modern physics. To this end, I will take liberties in explaining things, and not always go for full scientific accuracy, while hopefully still getting the core concepts across. If a more in-depth explanation is wanted, please ask in the comments and I will do my best to answer.

Previous topics

Bookmarkable meta post with links to all previous topics

Today's topic

Today's topic will be light emitting diodes, better known as LEDs. As the name suggests, we'll have to discuss light and diodes. We will find out why LEDs can only emit a single colour and why they don't get hot like other sources of light. Let's start by discussing diodes, in case you are already familiar with diodes note that I will limit the discussion to semiconductor (p-n with a direct bandgap) diodes as that's the type that's used in LEDs.

What's a diode?

A diode is an electronic component that, ideally, only lets electric current through in one direction. In other words it's a good resistor when the current flows in one direction and a really good conductor when the current flows in the other direction. Let's look a bit closer at how diodes function.

Semiconductors

Diodes are made out of two different semiconducting materials. In everyday life we tend to classify materials as either conducting (metals being the prime example) or non-conducting (wood, plastics, rubber). Conductance is the flow of electrons through a material, a conducting material has a lot of electrons that can move freely through a material while an insulator has none. Semiconducting materials fall in between these two categories. They do conduct but not a lot, so in other words they have a few electrons that can move freely.

N-type semiconductors

We are able to change a semiconductor's conductivity by adding tiny amounts of other materials, this is called doping. As an example, we can take silicon (the stuff that the device you're reading this on is made out of) which is the most well-known semiconductor. Pure silicon will form a crystal structure where each silicon atom has 4 neighbours, and each atom will share 1 electron with each neighbour. Now we add a little bit of a material that can share 5 electrons with its neighbours (how generous!). What will happen? Four of its shareable electrons are busy being shared with neighbours and won't leave the vicinity of the atom, but the fifth can't be shared and is now free to move around the material! So this means we added more freely flowing electron and that the conductivity of the semiconductor increases. An illustration of this process is provided here, Si is chemistry-talk for silicon and P is chemistry-talk for phosphorus, a material with 5 shareable electrons. This kind of doping is called n-type doping because we added more electrons, which have a negative charge, that can freely move.

P-type semiconductors

We can do the same thing by adding a material that's a bit stingy and is only willing to share 3 electrons, for example boron. Think for a moment what will happen in this case. One of the silicon atoms neighbouring a boron atom will want to share an electron, but the boron atom is already sharing all of its atoms. This attracts other electrons that are nearby, one of them will move in to allow the boron atom to share a fourth electron. However, this will create the same problem elsewhere in our material. Which will also get compensated, but this just creates the same problem once more in yet another location. So what we now have is a hole, a place where an electron should be but isn't, that is moving around the crystal. So in effect we created a freely moving positive charged hole. We call this type of doping p-type. Here's an illustration with B the boron atoms.

Creating a diode

So what would happen if we took a n-type semiconductor and a p-type semiconductor and pushed them against one another? Suddenly the extra free-flowing electrons of the n-type semiconductor have a purpose; to fill the holes in the p-type. So these electrons rush over and fill the holes nearest to the junction between the two semiconductors. However, as they do this a charge imbalance is created. Suddenly the region of p-type semiconductor that is near the junction has an abundance of electrons relative to the positive charges of the atom cores. A net negative charge is created in the p-type semiconductor. Similarly, the swift exit of the electrons from the n-type semiconductor means the charge of the cores there isn't compensated, so the region of the n-type semiconductor near the junction is now positively charged. This creates a barrier, the remaining free electrons of the n-type cannot reach the far-away holes of the p-type because they have to get through the big net negative charge of the p-type near the junction. Illustration here. We have now created a diode!

How diodes work

Think for a moment what will happen if we send current* (which is just a bunch of electrons moving) from the p-type towards the n-type. The incoming electrons will face the negative charge barrier of the p-type and be unable to continue. This means there is no current. In other words the diode has a high resistance. Now let's flip things around and send electrons through the other way. Now they will come across the positive charge barrier of the n-type semiconductor and be attracted to the barrier instead. The electrons' negative charge compensates the net positive charge of the barrier on the n-type and it will vanish. This destroys the equilibrium situation of the barrier. The p-type holes are no longer repelled by the positive barrier of the n-type (as it no longer exists) and move closer to the junction, this means the entire barrier will fade and current can move through. We now have a conductor.

OK, but I don't see what this has to do with light

Now let's find out how we can create light using this method. When current is applied to a diode what happens is that one side of the diode is at a higher energy than the other side. This is what motivates the electrons to move, they want to go from high energy to low energy. If the p-type semiconductor is at a higher energy than the n-type the electron will, upon crossing the junction between the two types, go from a high energy level to a lower one. This difference in energy must be compensated because (as @ducks mentioned in his thermodynamics post) energy cannot be destroyed. So where does the energy go? It gets turned into light!

The energy difference between the p-type and n-type is fixed, meaning a fixed amount of energy is released each time an electron crosses the junction. This means the light is of a single colour (colour is how we perceive the wavelength of light, which is determined by the energy of the light wave). Furthermore, none of the energy is lost so there is no energy being turned into heat, in other words the LED does not get warm.

Conclusion

So now we know why the LED is so power-efficient; it does not turn any energy into heat, it all goes into light. We now also know why they only emit a single colour, because the energy released when an electron crosses the junction is fixed.

Next time

I think next time I will try to tackle the concept of wave functions in quantum mechanics.

Feedback

As usual, please let me know where I missed the mark. Also let me know if things are not clear to you, I will try to explain further in the comments!

Addendum

*) Yes, current flow is defined to be opposite to the flow of the electrons, but I don't want to confuse readers with annoying definitions.

Intro

Hello everyone,

@wanda-seldon has been giving us an introduction to quantum physics. For now, she will be given a short break to prepare new stuff. In the meantime I will be covering some classical mechanics, more specifically thermodynamics. In part 1, we need to work our way through some of the more dry concepts, so we can understand and appreciate the horrifying implications of the fun parts. So I promise, this will be the most verbose one.

Some of you may have briefly seen a version of this posted, that was due to me misunderstanding the schedule with @wanda-seldon. If you saw that one, I will mention I rewrote nearly all of it to be more readable.

Now, on today's agenda: The basics of heat, work and energy and how it's all related.

Previous posts can be found here: https://tildes.net/~science/8al/meta_post_for_a_laypersons_introduction_to_series

Important note

If @wanda-seldon in her posts mention "energy", it's most likely in the context of energy operators, which is a concept in quantum physics. I'm not going to pretend I understand them, so I will not be explaining the difference. We will cover what energy is in classical mechanics. So keep that in mind if you read something from either of us.

Subject

Summarized

What is heat? Using a lot of fancy words we can describe it as follows. Heat is an energy that is transferred between systems by thermal interaction. And what is work? Work is an energy that is applied in a way that performs... work. The combined energy in a system is called internal energy. This type of energy can be transformed or applied to other systems.

These are a lot of new words, so lets break that down a bit.

Systems

A system is just a catch-all term for something that can be defined with a boundary of sorts. Be it mass, volume, shape, container, position, etc. A canister, your tea mug, the steam inside a boiler, your body, a cloud, a room, earth, etc. They are all systems because you can in some way define what is within the boundary, and what is beyond the boundary.

In theory, you could define every single nucleid in the universe as an unique system. But that would be counter-intuitive. In thermodynamics we tend to lump things into a system, and treat it as one thing. As opposed to Quantum stuff that looks at the smallest quantity. Calculating every single water molecule in my coffee would be pure insanity. So we just treat my mug as the boundary, and the tea inside the mug as the system. And just so it's mentioned, systems can contain systems, for instance a tea mug inside a room.

Energy

Energy is some quantifiable property that comes in either the form of heat, work. It can be transferred to other systems, or change between the different energy types. An example of transfer is my coffee cooling down because it's in a cold room. That means heat has been transferred from one system (my mug) to another system (the room). Alternatively you could say my hot coffee mug is warming up the room, or that the room is cooling down my coffee. Thermodynamics is a LOT about perspective. An example of transforming energy types is when we rub our hands together. That way we convert work (rubbing) into heat. It's really not more complicated than that. An interaction in this case is just a system having an effect on a different system. So a thermal interaction means it's an interaction due to heat (like in the mug example).

This brings us to an extremely important point. So important, it's considered "law". The first law of thermodynamics even. Energy cannot be destroyed, it can only change forms.

Your battery charge is never really lost. Neither is the heat of your mug of coffee. It just changed form or went somewhere else. The combined energy of all types that is residing inside a system is called internal energy.

Heat and work

Let's say we have a system, like a room. And all windows and doors are closed, so no energy can leave. In this system, you have a running table fan connected to a power line, getting energy from outside the system. The table fan is making you feel cool. Is the fan cooling down the room, heating up the room, or doing nothing? Think about it for a moment.

http://imgbox.com/CKtQLLOQ

The first thought of many would be to think that this fan would cool the room down, it sure makes you feel cooler! But it's actually heating up the room. As we remember, internal energy is the energy inside a system (room, in this case). The fan is getting energy from outside, and uses this energy to perform work. The fan accelerates the air inside the room, and this accelerated air will evaporate some of your sweat, so you feel cool. But as we remember, energy cannot be destroyed. So we are importing energy into the system, increasing the internal energy. Some of the work from the fan is also directly converted to heat, since the motor of the fan will get hot.

So if we are not getting rid of any of this excess energy, we are increasing the internal energy. And therefore actively increasing the temperature of the room.

http://imgbox.com/SAtqk7YG

To use a more tangible example: Simplified, this phenomena is why green house gases are bad. Lets define earth as a system. Earth gets a lot of energy from the sun. And a lot of this energy will be reflected and sent back to space. Green house gases will reflect back some of this energy trying to leave earth. So instead of having a roughly equal amount of energy enter the system (from the sun, from us doing stuff, etc) that leaves out in space, we have an increasing amount of energy on earth. This, as a consequence, increases temperature.

Implications

Now, what are the maybe not so obvious implications of this?

Waste heat, from supplied energy or inefficient work is a constant headache in engineering. If we cannot remove enough heat, we will actively heat up objects until they are destroyed. Thats why good cooling systems are important in cars, computers, etc.

Whats next?

Now this was not so bad. In the future we will cover phase changes, equilibriums, entropy, the heat death of the universe and briefly touch upon engines. So thats most likely two more parts after this. After that @wanda-seldon will take over again.

I plan on doing one main part per week, but if something is asked that warrants a small topic I might do smaller ones inbetween.

Feedback

Something unclear? Got questions? Got feedback? Or requests of topics to cover? Leave a comment.

What's this?

This post contains all entries of the "a layperson's introduction to" series. I will keep this thread up to date and sorted. This means this post is an excellent opportunity to try out the bookmarking feature!

Physics

Quantum Physics

Basics of quantum physics

Material Science

Classical physics

Thermodynamics

Computer Science

Artificial Intelligence

I am a bit lazy, and I also seem to like the default 3 day filter on the activity feed... but, sometimes a person less lazy than I responds to a topic of mine which is older that 3 days. These are usually good responses. These folks clearly played with the time filter. Other users are missing out on these responses.

I agree that a 3 day filter may be the ideal filter at the normal activity level of Tildes at large, at this point. But Tildes is still really fluctuating in activity, as may other sites based on the codebase. This may be an even bigger issue in specific groups.

Would there be any workable and beneficial way to make the default time filter a function of recent activity? This may apply to the main feed, and each group feed. This would help in site/group times of low activity, and might scale to the much higher activity of the future.. does this make any sense at all?

Would it be better to make the default time filter a function of activity, instead of a arbitrary setting which an admin selected?

Edit: the list box label might default to a dynamic “recent”, or similar, and then still have the other options of “last 1 hour, last 12 hours,” etc...

EDIT: With the help of @ducks the post now has illustrations to clear up the experimental set-up.

Introduction

I want to give an introduction on several physics topics at a level understandable to laypeople (high school level physics background). Making physics accessible to laypeople is a much discussed topic at universities. It can be very hard to translate the professional terms into a language understandable by people outside the field. So I will take this opportunity to challenge myself to (hopefully) create an understandable introduction to interesting topics in modern physics. To this end, I will take liberties in explaining things, and not always go for full scientific accuracy, while hopefully still getting the core concepts across. If a more in-depth explanation is wanted, please ask in the comments and I will do my best to answer.

Previous topics

Spintronics
Quantum Oscillations
Quantisation and spin, part 1

Today's topic

Today's topic will be a continuation of the topics discussed in my last post. So if you haven't, please read part 1 first (see link above). We will be sending particles through two Stern-Gerlach apparatuses and then we'll put the particles through three of them. We will discuss our observations and draw some very interesting conclusions from it on the quantum nature of our universe. Not bad for a single experiment that can be performed easily!

Rotating the Stern-Gerlach apparatus

We will start simple and rotate the set-up of the last post 90 degrees so that the magnets face left and right instead of up and down. Now let's think for a moment what we expect would happen if we sent silver atoms through this setup. Logically, there should not be in any difference in outcome if we rotate our experiment 90 degrees (neglecting gravity, whose strength is very low compared to the strength of the magnets). This is a core concept of physics, there are no "privileged" frames of reference in which the results would be more correct. So it is reasonable to assume that the atoms would split left and right in the same way they split up and down last time. This is indeed what happens when we perform the experiment. Great!

Two Stern-Gerlach apparatuses

Let's continue our discussion by chaining two Stern-Gerlach apparatuses together. The first apparatus will be oriented up-down, the second one left-right. We will be sending silver atoms with unknown spin through the first apparatus. As we learned in the previous post, this will cause them to separate into spin-up and spin-down states. Now we take only the spin-up silver atoms and send them into the second apparatus, which is rotated 90 degrees compared to the first one. Let's think for a moment what we expect would happen. It would be reasonable to assume that spin-left and spin-right would both appear 50% of the time, even if the silver atoms all have spin-up too. We don't really have a reason to assume a particle cannot both have spin up and spin right, or spin up and spin left. And indeed, once again we find a 50% split between spin-left and spin-right at the end of our second apparatus. Illustration here.

Three Stern-Gerlach apparatuses and a massive violation of common sense

So it would seem silver atoms have spin up or down as a property, and spin left or spin right as another property. Makes sense to me. To be sure, we take all the silver atoms that went up at the end of the first apparatus and right at the end of the second apparatus and send them through a third apparatus which is oriented up-down (so the same way as the first). Surely, all these atoms are spin-up so they will all come out up top again. We test this and find... a 50-50 split between up and down. Wait, what?

Remember that in the previous post I briefly mentioned that if you take two apparatuses who are both up-down oriented and send only the spin-up atoms through the second one they all come out up top again. So why now suddenly do they decide to split 50-50 again? We have to conclude that being forced to choose spin-left or spin-right causes the atoms to forget if they were spin-up or spin-down.

This result forces us to fundamentally reconsider how we describe the universe. We have to introduce the concepts of superposition and wave function collapse to be able to explain these results.

Superpositions, collapse and the meaning of observing in quantum physics

The way physicists make sense of the kind of behaviour described above is by saying the particles start out in a superposition; before the first experiment they are 50% in the up-state and 50% in the down-state at the same time. We can write this as 50%[spin up]+50%[spin down], and we call this a wave function. Once we send the particles through the first Stern-Gerlach apparatus each one will be forced to choose to exhibit spin-up or spin-down behaviour. At this point they are said to undergo (wave function) collapse; they are now in either the 100%[spin up] or 100%[spin down] state. This is the meaning of observing in quantum mechanics, once we interact with a property of an atom (or any particle, or even a cat) that is in a superposition this superposition is forced to collapse into a single definite state, in this case the property spin is in a superposition and upon observing is forced to collapse to spin up or spin down.

However, once we send our particles through the second apparatus, they are forced to collapse into 100%[spin left] or 100%[spin right]. As we saw above, this somehow also makes them go back into the 50%[spin up]+50%[spin down] state. The particles cannot collapse into both a definite [spin up] or [spin down] state and a definite [spin left] or [spin right] state. Knowing one precludes knowing the other. An illustration can be seen here.

This has far reaching consequences for how knowable our universe it. Even if we can perfectly describe the universe and everything in it, we still cannot know such simple things as whether a silver atom will go left or right in a magnetic field - if we know it would go up or down. It's not just that we aren't good enough at measuring, it's fundamentally unknowable. Our universe is inherently random.

Conclusion

In these two posts we have broken the laws of classical physics and were forced to create a whole new theory to describe how our universe works. We found out our universe is unknowable and inherently random. Even if we could know all the information of the state our universe is in right now, we still would not be able to track perfectly how our universe would evolve, due to the inherent chance that is baked into it.

Next time

Well that was quite mind-blowing. Next time I might discuss fermions vs bosons, two types of particles that classify all (normal) matter in the universe and that have wildly different properties. But first @ducks will take over this series for a few posts and talk about classical physics and engineering.

Feedback

As always, please feel free to ask for clarification and give me feedback on which parts of the post could me made clearer. Feel free to discuss the implications for humanity to exist in a universe that is inherently random and unknowable.

Addendum

Observant readers might argue that in this particular case we could just as well have described spin as a simple property that will align itself to the magnets. However, we find the same type of behaviour happens with angles other than 90 degrees. Say the second apparatus is at an angle phi to the first apparatus, then the chance of the particles deflecting one way is cos^2(phi/2)[up] and sin^2(phi/2)[down]. So even if there's only a 1 degree difference between the two apparatuses, there's still a chance that the spin will come out 89 degrees rotated rather than 1 degree rotated.

feels like we should probably have one of these in here since it doesn't appear we've had one of these as a community in ~creative in awhile--if ever.

i've spent the better portion of my day today working on a census form for the kryfona kingdom, which is one of the many countries in my fairly large worldbuilding effort. the first page actually came out really well, i think, so that was time well spent. i've considered making a post about some of its more intricate detail since i think some people on here might enjoy that, but for now i've opted to just make this general thread since i dunno how well it'd go as a discussion topic. maybe if y'all think it's worthy of one? idk.

anyways, what creative things have you been working on recently?

I have not been paying close attention lately, but I swear that it was possible to highlight some text in my notifications and/or topic’s comment thread views, so that I can paste it into a quote in my reply.

Anyone else have an iOS device that they can try this on?

Hey Tildes, I got a job directly supervising a small team of 4 software developers. I'm very excited at the prospect and would like to put my best foot forward. To that end, I would like to have a discussion around a few topics. Feel free to expand the scope if you believe the conversation would be beneficial. I'm sure I won't be the last person to be in this position. I've done research, read, and watched videos regarding several of these questions; however, since Tilde prioritizes high-quality discussion, I thought it would be a fun opportunity to chat with others about these topics.

• As a member of a software development team, what are things that your supervisor has done that has had the greatest (a) positive and (b) negative impact?
• Supervisors, when you joined your new team, what was your methodology for reviewing the team, projects, and processes? What was the scenarios behind your review and the outcome? What would you do differently?

Sometimes one may knowingly add a comment that should be tagged as one of those, and sometimes I see people say (me included) things like "BTW this should be tagged <as such>." Maybe allowing a user to tag their own comment proactively with these three tags would be useful?

Edit: My main focus is the offtopic tag because I think that it's not necessarily bad or low-quality. Partially off-topic content can be very interesting and useful. Maybe I'm misunderstanding the use of that tag, was it intended for completely off-topic stuff in the first place?

Edit 2: I've opened an issue on Tildes Gitlab for this.

Introduction

I want to give an introduction on several physics topics at a level understandable to laypeople (high school level physics background). Making physics accessible to laypeople is a much discussed topic at universities. It can be very hard to translate the professional terms into a language understandable by people outside the field. So I will take this opportunity to challenge myself to (hopefully) create an understandable introduction to interesting topics in modern physics. To this end, I will take liberties in explaining things, and not always go for full scientific accuracy, while hopefully still getting the core concepts across. If a more in-depth explanation is wanted, please ask in the comments and I will do my best to answer.

Previous topics

Spintronics
Quantum Oscillations

Today's topic

Today's topic will be quantisation, explained through the results of the Stern-Gerlach experiment which was first performed in 1922. This topic treats a much more fundamental concept of quantum physics than my previous topics.

What is the Stern-Gerlach experiment?

In 1922 physicists Stern and Gerlach set up an experiment where they shot silver atoms through a magnetic field, the results of this experiment gave conclusive support for the concept of quantisation. I will now first explain the experiment and then, using the results, explain what quantisation is. If you would rather watch a video on the experiment, wikipedia provided one here, it can be watched without sound. Note that I will dive a bit deeper into the results than this video does.

The experiment consists of two magnets, put on top of each other with a gap in the middle. The top magnet has its north pole facing the gap, the bottom magnet has its south pole facing the gap. See this illustration. Now we can shoot things through the gap. What do we expect would happen? Let's first shoot through simple bar magnets. Depending on how its poles are oriented, it will either bend downwards, upwards or not at all. If the bar magnet's north pole is facing the top magnet, it will be pushed downwards (because then north is facing north). If the bar magnet's south pole is facing the top magnet, it will instead be pushed upwards. If the bar magnet's poles are at a 90 degree angle to the two magnets it will fly straight through, without bending. Lastly, if the bar magnet's poles are at any other angle, say 45 degrees, it will still bend but less so. If we send through a lot of magnets, all with a random orientation, and measure how much they got deflected at the other side of the set-up we expect to see a line, see 4 in the illustration.

Now we'll send through atoms, Stern and Gerlach chose silver atoms because they were easy to generate back in 1922 and because they have so-called spin, which we will get back to shortly. We send these silver atoms through in the same way we sent through the bar magnets; lots of them and all of them with a random orientation. Now what will happen? As it turns out all the atoms will either end up being deflected all the way up or all the way down, with nothing in between. 50% will be bent upwards, 50% downwards. So silver atoms seem to respond as if they were bar magnets that either bend maximally up or maximally down. In the illustration this is labeled 5.

If we were to take only the silver atoms that bent upwards and sent them through the experiment again, all of them would bend upwards again. They seem to remember if they previously went up or down rather than just deciding on the spot each time if they go up or down. What model can we think of that would explain this behaviour? The silver atoms must have some property that will make them decide to bend up or down. Let's call this property spin, and say that if the silver atoms chose to bend up they have spin up, if they chose to bend down they have spin down. It seems that these are the only two values spin can have, because we see them bend either maximally up or maximally down. So we can say the spin is quantised; it has two discrete values, up or down, and nothing in between.

Conclusion

We have found a property of atoms (and indeed other particles like electrons have spin too) that is quantised. This goes against classical physics where properties are continuous. This shows one of the ways in which physics at the smallest scales is fundamentally different from the physics of everyday life.

Next time

Next time we will investigate what happens when we rotate the angle of the magnets used in the experiment. This will lead us to discover other fundamental aspects of physics and nature, quantum superpositions and the inherent randomness of nature.

EDIT: part 2 is now up here.

Feedback

As discussed in the last post, I am trying something different for this post. Talking about more fundamental quantum physics that was discovered 100 years ago rather than modern physics. Did you like it? Let me know in the comments!

Yesterday @talklittle posted the topic Halloween game sales are live. What are your Horror/Halloween-themed recommendations?. There have been some good recommendations and whatnot. If you like horror games and weren't aware of the ongoing sales, go check out the comments for some recommendations.

Being the meta-killjoy that I am, I started this sidebar about the top comment. tl;dr: I don't think this type of content engenders Tildes's discussion forward community.

Fell free to read the whole thread of comments for some civil discussion on the matter, but I do want to open this up to all of Tildes: should this type of comment be policed on Tildes?

Also: do you think this type of comment is good? Do you agree with me that it's retroactive to Tildes's goals? Am I just a big killjoy? Given that the comment I'm calling into question is the top comment of that topic, I'm probably David in this arena but I want to hear it from everyone else.

I've been thinking about my experience on Tildes with news and articles. It's mostly been seeing high quality content and discussion that I'm happy with. However for the sake of this, I want to discuss avoiding something negative.

Lately I've noticed news and articles with headlines that I feel are biasing in nature and potentially inflammatory.

I would guess that we're all pretty familiar with this method in general. At some point when a forum/aggregate becomes large enough it provides an profitable opportunity for third parties to distribute content. Or an individual is pursuing their fulfillment of a personal ideal.

I have a few suggestion to handle the issues productively.

News sources that put a higher priority on traffic versus their reputation tend to do so consistently. It would be valuable for users to be required to tag the parent domain when posting external links to allow users to discern sources case by case using tags.

Blocking something a news source versus <inciting-phrase> has the benefit of allowing higher quality sources mentioning the same topic to have an impact on the user. That's potentially very valuable in encouraging informed perspective.

Linking news and articles for commercial or personally motivated reasons is posted on subs that have a marginal relation. E.g. Posting a story on Mike Pence denouncing all white men working in agriculture in an agriculture sub. The connection can certainly be made but I don't think that's a good way of organizing that information. I think it would be more productive to post that in a news or news/political thread. Having the ability to choose when we see and engage with that type of content is important. It benefits the individual and encourages healthy and engaged communities.

Blocking users ( I wasn't sure if this existed ) Alternatively, a system for linked content reputation per user. But I think that's a bad solution overall.
I meant filtering users content and comments as a preference for users. I'm not talking about site wide.

I'm curious if other Tilde users agree with my issues or suggestions.

We have the "Exemplary" label for comments, which identifies comments as particularly good, and even boosts their ranking within threads.

Now that we've had this for a while, I keep finding myself want to do the same for topics. I'll read an article and want to give it an extra boost because it's better than average.

I'm ready for an equivalent to the "Exemplary" label for topics.