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Origin of 'Daemon' in Computing

takeourword.com

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Re: Origin of 'Daemon' in Computing

#101

Post by mmooss »

They rely too much on Professor Corbato's account:

Corbato confidently gives the reason but A) doesn't claim to have coined the term, and may not know what the coiner's thinking was; B) at the time may have had a different understanding than some other members of the group - it's not the sort of thing that people have a meeting about; and C) is writing about something that happened decades ago.

Corbato then cites Take Our Word's prior description - people who weren't present when the word was coined, and who openly say they have no idea: "This is so reminiscent of Maxwell's daemon watching his molecules that we can only assume that whoever dubbed these "system processes" had Maxwell's daemon in mind. Unfortunately, we have found no hard evidence to support this."

Then Take Our Word cites Corbato, creating a loop. The only evidence in that loop is Corbato's flawed (being human), prompted (by reading Take Our Word) memory of possibly limited knowledge from decades ago.

Re: Origin of 'Daemon' in Computing

#102

Post by n4r9 »

eru wrote: post #93
n4r9 wrote: post #64

Earlier quoted context omitted.

I think you'd have to be pretty precise to know if it's heading towards a hole that's only just large enough for it.

Why would you make the hole so small? The main requirement for the hole is that it's small enough that (with high enough probability) only at most one or a handful of molecules will make its way through. And that size is completely independent of the size of your molecules, and only depends on how many there are per unit volume. There's a lot of 'empty space' between molecules in a gas.

Good question. I was going off the linked article which states:

> In the middle of the divider was a tiny gate, just large enough to admit one molecule of gas.

Still, that's quite a small hole relatively speaking. So you'd have to be fairly precise about both position and velocity. Potentially more than is allowed by Plank's constant. I dunno though, this isn't one of the counterarguments in the Wikipedia page, so probably you're right.

Re: Origin of 'Daemon' in Computing

#103

Post by p_l »

prepend wrote: post #81
vhodges wrote: post #29

Earlier quoted context omitted.

From: https://devrant.com/rants/1101391/my-daily-unix-command-list... unzip; strip; touch; finger; mount; fsck; more; yes; unmount; sleep.

Tail/head It’s almost like these commands were all made by nerd teenage boys.

or rather nerd teenagers finding a way to joke on terms that didn't relate to sex until they thought of it and started spreading.

Re: Origin of 'Daemon' in Computing

#104

Post by BlueTemplar »

Vecr wrote: post #92
BlueTemplar wrote: post #89

Earlier quoted context omitted.

Yes, exactly, and this is what allows quantification. http://www.av8n.com/physics/thermo/entropy-more.html#sec-pha... With 'entropy' being an obsolete term for (lack of) information, and > “classical thermodynamics” is a contradiction in terms.

On the "information" part, I'm not sure that's correct, have you seen the papers that dispute the Bayesian versions of thermodynamics? I think practically though, even before you hit anything "quantum", the requirement that you physically interact with the system is what dooms you.

No, got a link ?

Searching for them did bring me to an interesting discussion :

https://www.lesswrong.com/posts/YSFRazdoWXKHgNakz/link-the-b... (2015)

and then to :

https://bayes.wustl.edu/etj/articles/second.law.pdf (1998)

Which confirms my suspicions, but also sheds lights on how old the confusion is !

There are a bunch of assumptions that are easy to make (because they almost always are true), but very hard to get rid of when they aren't :

- that entropy is objective/ontological rather than subjective/epistemic

- that entropy is equivalent to disorder

- that temperature can always be defined

- that entropy is extensive

(- I think there was at least another one, but I had to do something else in-between and I don't remember now)

- oh yeah, maybe it was that there's a difference between a distribution and a macrostate ? (not sure about it myself)

Now, I don't know what the Bayesian framework can bring to the table here (not being sufficiently familiar with it down to the nuts and bolts of calculations), but if it can prevent us (and future students) from making these mistakes over and over and over again, it would be real progress.

Re: Origin of 'Daemon' in Computing

#105

Post by Vecr »

BlueTemplar wrote: post #104
Vecr wrote: post #92

Earlier quoted context omitted.

On the "information" part, I'm not sure that's correct, have you seen the papers that dispute the Bayesian versions of thermodynamics? I think practically though, even before you hit anything "quantum", the requirement that you physically interact with the system is what dooms you.

No, got a link ? Searching for them did bring me to an interesting discussion : https://www.lesswrong.com/posts/YSFRazdoWXKHgNakz/link-the-b... (2015) and then to : https://bayes.wustl.edu/etj/articles/second.law.pdf (1998) Which confirms my suspicions, but also sheds lights on how old the confusion is ! There are a bunch of assumptions that are easy to make (because they almost always are true), but very hard to get…

https://arxiv.org/abs/1508.02421v1

https://arxiv.org/abs/1508.02421v3 (updated, 2017)

They claim to fix the criticisms, see the section "The Bayesian arrow of time."

Who knows how well they did though.

As far as I can tell they're still making impossible assumptions, because certain Bayesian problems can't be calculated under a certain amount of energy, and some can't be calculated at all while embedded in spacetime (excepting time travel, and sometimes even then).

I think it's necessary to increase (on expectation) the entropy in a closed system when measuring, unless you take measuring to be magic and not a physical process.

Re: Origin of 'Daemon' in Computing

#106

Post by JadeNB »

saltcured wrote: post #60
JadeNB wrote: post #55

Earlier quoted context omitted.

> Surely the logical pronunciation is the way you'd pronounce it in library, so a long 'ai' rather than any kind of 'i'? Yep, that's what I meant to say with: > … never noticed until I heard someone else say it with a long 'i' that that was obviously the logical pronunciation. But maybe the sentence structure was too tortured for it to be clear what I was saying. > Though I personally always use the short 'i'. I was…

Do you pronounce the vowel in /var as in "bar" or as in "bare"? Also, for those who try to pronounce everything rather than spell them out, where does it end? I now have a newly discovered, morbid interest in how such folks say path elements like "selinux", "httpd", and "pgsql"...

> Do you pronounce the vowel in /var as in "bar" or as in "bare"?

Ha, they're everywhere!

Re: Origin of 'Daemon' in Computing

#107

Post by mmooss »

mmooss wrote: post #101

They rely too much on Professor Corbato's account: Corbato confidently gives the reason but A) doesn't claim to have coined the term, and may not know what the coiner's thinking was; B) at the time may have had a different understanding than some other members of the group - it's not the sort of thing that people have a meeting about; and C) is writing about something that happened decades ago. Corbato then cites Tak…

They do have more evidence, which I overlooked (apologies to the OP):

"Professor Jerome H. Saltzer, who also worked on Project MAC, confirms the Maxwell's demon explanation. He is currently working on pinpointing the origin of the erroneous acronym etymology for daemon in this sense."

Re: Origin of 'Daemon' in Computing

#109

Post by eru »

n4r9 wrote: post #102
eru wrote: post #93

Earlier quoted context omitted.

Why would you make the hole so small? The main requirement for the hole is that it's small enough that (with high enough probability) only at most one or a handful of molecules will make its way through. And that size is completely independent of the size of your molecules, and only depends on how many there are per unit volume. There's a lot of 'empty space' between molecules in a gas.

Good question. I was going off the linked article which states: > In the middle of the divider was a tiny gate, just large enough to admit one molecule of gas. Still, that's quite a small hole relatively speaking. So you'd have to be fairly precise about both position and velocity. Potentially more than is allowed by Plank's constant. I dunno though, this isn't one of the counterarguments in the Wikipedia page, so pr…

Air molecules are large and massive, so their de Broglie wavelength is actually much smaller than their physical size (and that's much smaller than the hole needs to be to let in one at a time at ambient pressure and temperature), and you don't need to know their speeds all that well, eg if you just want to 'pump' all the air from one chamber into another.

So all in all, a classic description would work reasonably well. (Remember that quantum uncertainty is related more to de Boglie wavelength than physical size.)

Re: Origin of 'Daemon' in Computing

#110

Post by n4r9 »

eru wrote: post #109
n4r9 wrote: post #102

Earlier quoted context omitted.

Good question. I was going off the linked article which states: > In the middle of the divider was a tiny gate, just large enough to admit one molecule of gas. Still, that's quite a small hole relatively speaking. So you'd have to be fairly precise about both position and velocity. Potentially more than is allowed by Plank's constant. I dunno though, this isn't one of the counterarguments in the Wikipedia page, so pr…

Air molecules are large and massive, so their de Broglie wavelength is actually much smaller than their physical size (and that's much smaller than the hole needs to be to let in one at a time at ambient pressure and temperature), and you don't need to know their speeds all that well, eg if you just want to 'pump' all the air from one chamber into another. So all in all, a classic description would work reasonably we…

I'm not sure I understand - why is the wavelength size relevant? In my understanding, the standard deviations of position and momentum are at least some constant multiple of Plank's constant.
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