This thread is posted weekly, and is intended as a place for more-casual discussion of the coronavirus and questions/updates that may not warrant their own dedicated topics. Tell us about what the situation is like where you live!

Today's problem description: https://adventofcode.com/2021/day/11

Please post your solutions in your own top-level comment. Here's a template you can copy-paste into your comment to format it nicely, with the code collapsed by default inside an expandable section with syntax highlighting (you can replace python with any of the "short names" listed in this page of supported languages):

<details>
<summary>Part 1</summary>

```python
Your code here.
```

</details>

When I last wrote about money, some people liked it but u/MimicSquad had issues with my simplified explanation. After thinking about it, I'm going to try again. I don't want to make my "casino world" analogy too complicated, but I will make some changes so that we can talk about payments. (Caveat: I'm not a financial expert, but this is how I think it works.)

So let's say there is a town with two casinos. In the Yellow Casino, gamblers use yellow plastic chips, and in the Purple Casino, they use purple plastic chips. Otherwise, they are much alike. Each casino has a teller window where gamblers exchange the national currency (which we might call green money) for its own chips.

So there are three currencies (yellow, purple, and green) and two exchanges (the teller windows). The casinos want their chips to be worth the same amount as green money, so their teller windows always trade them at par. (This makes yellow and purple chips worth the same amount too, even though nobody trades them directly yet.)

Suppose that a gambler who has yellow chips walks into the Purple Casino. "You can't use those chips here," they say, "but for your convenience, we will trade you a purple chip for each of your yellow chips." Which they do. Then they send an employee to the Yellow Casino and trade the yellow chips for green money.

This is a basic payment system. It's implemented as two trades, one visible and one hidden. The Purple Casino's teller visibly trades yellow chips for purple, and behind the scenes there is a settlement process, implemented using a trusted employee who carries chips and money to do another trade. The gambler doesn't need to know about trades between casinos, but they're essential for providing this service.

Notice that, although the gambler carried yellow chips from Yellow Casino to Purple Casino, the second trade (a withdrawal) causes the Yellow Casino to have less money. The money followed the chips and the chips came back home.

It doesn't need to happen quite that way, though. If Yellow and Purple agree, the Yellow casino could trade anything that's worth the same amount in return for getting its chips back. So, more abstractly, some financial asset must follow the chips from Yellow to Purple.

Furthermore, if the casinos trust each other, they can delay settling up. Perhaps at the end of the day, the Purple Casino will have some yellow chips and the Yellow Casino has some purple chips, so they can exchange yellow for purple and they can use green money (or any financial asset) to make up the difference.

Why settle at all? Partly because of risk. The casinos don't want to trust each other too much. If the Yellow Casino gets into financial trouble, the Purple Casino doesn't want to end up holding worthless yellow chips instead of the green money that they have more confidence in. (Also, they probably find green money more useful than yellow chips.)

These casinos are are my thinly-disguised model for banks. To make things a bit less abstract, I'll talk about the US. There around 4,000 banks (and 5,000 credit unions) in the US. Each bank has its own computers that implement money as bank deposits. They have payment systems that tie them all together and hundreds of thousands of ATM's that trade electronic currency for cash.

We could think of US banks as having 4,000 different currencies that all trade at par. While we normally think of the US dollar as a single currency, it could also be thought of as a federated system of many currencies, all tied together with payment systems that do lots of trades. (Nothing really changes; this is just a different way of thinking about it.) There are some currencies with special status, like paper money and coins and federal reserve accounts, but these are in addition to all the others. (You could even think of each kind of coin as its own currency, and making change as a form of currency trade.)

There is a historical basis in early US history for treating each bank as having its own currency. US banks back then issued their own paper money, and although they tried to make them trade at par, these banks sometimes failed and were sometimes frauds, and their paper money often traded at much less than par. These days banks are much better regulated and we normally don't have to worry about such things, but much as a multicellular organism has cell walls as a sort of remnant of earlier times when cells were more independent, the boundaries between banks still matter, despite all the regulated mechanisms that make their currencies practically the same to us.

Since each bank manages its own computer systems, there is a sense in which electronic money never actually moves outside its own bank. ​When we "move money" electronically, it's done by trading, and there has to be a payment system to bridge the gap. The timing of the trades varies, depending on the details of the settlement process.

What about creating money? In casino world, the Yellow Casino makes yellow chips and the Purple Casino makes purple chips, but they can only make their own chips. Similar, a bank could make money in its own computer system, but they are limited in what they can do in anyone else's computers. They influence other bank's computers via trades.

If a bad bank created a lot of their own money and then spent it (perhaps disguised as making a loan), they would still be on the hook during the settlement process, which essentially requires them to take their money back in return for a financial asset worth the same amount that wasn't created by them, such as money in their central bank account. Payments can be very complicated and there is often short-term debt involved in the settlement process, but ultimately a legitimate bank needs to honor its debts.

It's similar to how anyone with a checkbook could write bad checks, but this will catch up with you during settlement. The physical ability to write large numbers on checks isn't a superpower that lets you buy anything. What a criminal could do with it is somewhat limited and short-term.

Every bank has accounts with the central bank and one thing they are used for is implementing settlement. Having "reserves" with the central bank, even there isn't a legally required balance, is something every other bank needs to handle some kinds of payments. Just as you need money in your bank account to write a check and have it not bounce, banks need a high enough balance with the central bank to handle the payments their customers make. (Though I don't know the details of what sort of overdraft protections there are.)

The only bank that can buy anything it likes without consequences to itself is the central bank, which doesn't participate in settlement like everyone else. The central bank's power to create its own money might look superficially similar to other banks, but it's special because payment is complete after the first trade; there is no further settlement after receiving central bank money. (Though a bank could trade reserves for cash if it needs it for its ATM's.)

The end, for now. Sometimes I've been writing in a definitive way here, but keep in mind that I'm still not a financial expert and I welcome corrections from people who know better.

Today's problem description: https://adventofcode.com/2021/day/10

Please post your solutions in your own top-level comment. Here's a template you can copy-paste into your comment to format it nicely, with the code collapsed by default inside an expandable section with syntax highlighting (you can replace python with any of the "short names" listed in this page of supported languages):

<details>
<summary>Part 1</summary>

```python
Your code here.
```

</details>

This thread is posted weekly - please try to post all relevant US political content in here, such as news, updates, opinion articles, etc. Extremely significant events may warrant a separate topic, but almost all should be posted in here.

This is an inherently political thread; please try to avoid antagonistic arguments and bickering matches. Comment threads that devolve into unproductive arguments may be removed so that the overall topic is able to continue.

Today's problem description: https://adventofcode.com/2021/day/9

Please post your solutions in your own top-level comment. Here's a template you can copy-paste into your comment to format it nicely, with the code collapsed by default inside an expandable section with syntax highlighting (you can replace python with any of the "short names" listed in this page of supported languages):

<details>
<summary>Part 1</summary>

```python
Your code here.
```

</details>

What are some VR games where the person in the headset can cast to a TV and the people watching can still participate/have fun?

For example, at a get-together over the summer, my friends and I played a hot seat version of I Expect You to Die 2. The person in the headset played the single-player game themselves, but everyone in the audience was able to watch the cast on the TV and help that person by giving them recommendations to try different things and help them solve the puzzles (or just recommend ridiculous stuff to see if the game will allow it). Even though the game is single-player, it worked really well as a communal experience and was a ton of fun for the whole room.

Any other recommendations for games like this we can try?

Note: we've already played Keep Talking and Nobody Explodes
Target Hardware: Oculus Quest 1

What have you been listening to this week? You don't need to do a 6000 word review if you don't want to, but please write something! If you've just picked up some music, please update on that as well, we'd love to see your hauls :)

Feel free to give recs or discuss anything about each others' listening habits.

You can make a chart if you use last.fm:

http://www.tapmusic.net/lastfm/

Remember that linking directly to your image will update with your future listening, make sure to reupload to somewhere like imgur if you'd like it to remain what you have at the time of posting.

Today's problem description: https://adventofcode.com/2021/day/8

Please post your solutions in your own top-level comment. Here's a template you can copy-paste into your comment to format it nicely, with the code collapsed by default inside an expandable section with syntax highlighting (you can replace python with any of the "short names" listed in this page of supported languages):

<details>
<summary>Part 1</summary>

```python
Your code here.
```

</details>

Today's problem description: https://adventofcode.com/2021/day/7

Please post your solutions in your own top-level comment. Here's a template you can copy-paste into your comment to format it nicely, with the code collapsed by default inside an expandable section with syntax highlighting (you can replace python with any of the "short names" listed in this page of supported languages):

<details>
<summary>Part 1</summary>

```python
Your code here.
```

</details>

Hey all. I just bought my first mountain bike. I don't know much about mountain biking but when I've taken a hybrid out onto logging trails it's been super fun so I'm sure I'll enjoy it. I have a few questions before I head out into the mountains:

1. What kind of mountain-biking specific gear do I need?
2. Where should I go as a beginner? Ideally somewhere with not too many hikers or other cyclists. I have plenty of stamina from my regular uphill cycling routine, but I don't want to get into intense steep riding and jumps right now.

Hi folks. I'm posting this in ~creative because I want to see what other artists think of it; the technical side is important too, but artists and art are the focus of this project.

Cryptographic Digital Art Tokens are a concept I've been working on for a while, to provide some of the benefits of crypto tokens without perpetuating the harm they create.

CDATs are not NFTs. They are not designed to facilitate investment, but rather collection. They do not use a blockchain and do not rely on distributed consensus at all. Instead, they use traditional cryptography to validate the ownership of art.

How CDATs Work

Let's say an artist Adam creates a piece of art called One. He decides he wants to sell a CDAT of One, so he creates a CDAT key and publishes his public key on his website, adam.art.

A collector, Beth, decides she wants to buy One. She e-mails Adam and they agree on a price, and exchange keys; once she has paid, Adam sends Beth a CDAT, which he has signed. Beth then cross-signs the CDAT and sends it back to Adam. It ends up looking like this:

=== CDAT DATA ===
Artist: Adam <adam@adam.art>
Collector: Beth <beth@betawork.codes>
Date of Sale: 2021-12-08T19:50:56Z
Title: One, a Digital Story
Work ID: art.adam.one
Cover Hash: e82c294938320bf4fab56970f52e1ddf
Work Hash: 3179c999f1d4fab4bcc8a57bca1c9d8c
Artist Key Fingerprint: c634d0420f825b91
Collector Key Fingerprint: 3b2e3bbf91ec96c2
=== CDAT SIGN ===
Artist Signature: YTtsc2tkamY7bHNramY7bGtqZDtsa2pmYTtsZGt...
Collector Signature: cXdpZXVwcXdpeXR1djtsbmFvdWNuZWN2cHdl...
=== CDAT META ===
Cover URL: https://adam.art/images/one-cover.jpg
Work URL: https://adam.art/art/one.zip
Artist Key URL: https://adam.art/static/cdat.key
Collector Key URL: https://betawork.codes/
=== CDAT OVER ===

In an ideal world, with all the software enablement I want to do, Beth would be able to take this token and put it in a digital gallery or on her website, where the art piece, and her ownership of it, would be proudly displayed for all to see in a user-friendly, beautiful format.

Structure

The CDAT has three sections - DATA, which is signed, META, which is not, and SIGN, which contains the CDAT's cryptographic signatures. Hashes and key fingerprints are in the DATA section, but URLs are in the META section, which means they can be changed later; artists and collectors can re-host their art and keys, so long as the files' hashes or fingerprints remain exactly the same.

Semantics

Because the CDAT is cross-signed, anyone can see that both Adam and Beth have agreed to the sale. Assuming the signatures and keys all check out, Beth can now prove to people that Adam sold her his art, and Adam can prove that Beth bought it.

Implementation

In order for this interaction to work, we technically need only existing technology: you can validate such things with GPG and some manual reordering. Ideally, though, we'd have a few tools:

• A CDAT validation program. This should include a command line program and a GUI (maybe even a mobile app?), and would validate the following information:
  • The given signatures are valid and correct for the given CDAT.
  • The keys used to sign the CDAT match both the given fingerprints and identities.
  • The linked key URLs, if any, in fact point to the indicated keys.
  • The linked art and cover URLs, if any, in fact point to files with the given hashes.
• A CDAT creation program. This should include a command line program and a GUI. It would take as input the relevant keys and names, provide a way to set the date, and ensure that everything relevant is online at the given URLs.
  • This program would be used by both artists (to create CDATs) and collectors (to cross-sign CDATs).
• A CDAT hosting service. Obviously there could be more than one of these, and people could host their CDATs and art on their own machines - that's decentralization, baby! - but it would be very nice to be able to host CDATs, art, and keys for free or a nominal fee.

This would be a great start, but in order to really kick-start the ecosystem, it would be nice to provide some additional enablement software, such as:

• A drop-in HTML embed that uses client-side JavaScript to display and validate CDATs on a website.
• A browser extension which validates CDATs found on arbitrary websites, on the user's request.
• A self-hostable CDAT gallery for artists and collectors which displays who owns what, and which art pieces are still for sale.

Please let me know if this idea is interesting to you, and ask any questions/leave comments!