Monday, April 1, 2024

Hyperlinks for emails?

It's looking like we could be able to hyperlink to emails soon! No more of this "oh uh check your email for the one I sent at 11:27...". You'll be able to add a link that works just like linking the web!

The IETF is working on their "Parsable Mail Pointer Email Protocol" (PMPEP), and I was able to get an advance copy! Check it out below:

RFC 9869: Parsable Mail Pointer Email Protocol (PMPEP)

Personally, I think they backronymed it from "Per My Previous Email Protocol"...

Edit 4/11: Yes, this was a joke. And apparently it would indeed be enough just to use the messageID. So why hasn't anyone implemented this???

Thursday, February 22, 2024

Setting short-selling straight; or, "But who let you short that?"

You might not be aware, but I've been short-selling some cryptocurrencies. (I would have said "been making money short-selling cryptocurrencies", but ...)

Often people ask some from of, "oh wow, what broker lets you do that?" It's actually an interesting misunderstanding, in that it misses a key insight:

You can short-sell any time you have a debt denominated in that asset.

At that point, you are short the asset. You benefit from anything that makes that asset easier to obtain, and thus extinguish your debt.

In the decentralized finance world, there are platforms (in my case, that let you deposit some crypto asset A, and borrow some other crypto asset B. Once you do so, and sell B, you are now short-selling B!

The concept applies more generally too: for example, if you owe your friend the favor of helping them move, then you are "short moving services" (because anything that makes moving services cheap, also makes your debt easier to service, at least because you have the option to satisfying by paying a service rather than doing it yourself).

Also, if you borrow US dollars, and spend them, you are "shorting the dollar", although it's usually not talked about in these terms. (You hold a debt denominated in dollars, after having "sold" them for something else, which we generally refer to as "buying".) Although, there was an interesting case where people would borrow USDC (a crypto dollar substitute) and then find out they could be bought back for less than a dollar during the Silicon Valley Bank collapse. Thus making them "accidental short-sellers"!

Sunday, January 28, 2024

A serious paper on bits as Joules per Kelvin

My ramblings about thermodynamics aren't so off-base, it turns out!

Remember this one? From 2009? Where I explained how Joules per Kelvin (energy per unit temperature) is a valid measure of information (or entropy, effectively "missing information"), which is normally measured in bits?

Well, now there's a paper that formalizes that idea and related ones. As the title ("Temperature as Joules per Bit") indicates, it looks at a rearranged version of the same insight (mine was "bits as Joules per temperature"). But, it also goes a lot deeper and derives thermodynamics starting from entropy to understand temperature, rather than the other way around, as is conventionally done.

Related thought: I remember back in that 2009 thermodyanmics/info theory frenzy, one of my goals was rederive the Carnot limit based on information-theoretic considerations -- that is, show it as a simple implication of the amount of knowledge you have about a system in a case where only know the temperature difference. (Naturally, I assumed someone had already done this and tried to find it but it was very hard to google for.)

Background: The Carnot limit tells you the maximum amount of mechanical work ("useful energy") you can extract from heat -- like, through an engine -- and, as it turns out, it's a function of the ratio of absoute temperatures you're working between. You don't face this limit when extracting work from a flywheel (spinning disc with grooves). Inspired by an counterintuitive insight in an Eliezer Yudkowsky LessWrong post, and my thoughts about it, I figured you could draw a more direct line from "knowledge of a temperature difference" to "how much energy is extractable".

Now I'll give it a go with ChatGPT, and post my findings!