Today I Learned

[Swamp Thing]

When was the first all-solid-state superhet radio reciever built?

Spoiler

In the 1920s, experimenters discovered "negative resistance" effects in point-contact crystal rectifiers. They exploited this property to make amplifiers and oscillators. Russian physicist Oleg Losev took this technology to the ultimate level:

The first person to exploit negative resistance practically was self-taught Russian physicist Oleg Losev, who devoted his career to the study of crystal detectors. In 1922 working at the new Nizhny Novgorod Radio Laboratory he discovered negative resistance in biased zincite (zinc oxide) point contact junctions. He realized that amplifying crystals could be an alternative to the fragile, expensive, energy-wasting vacuum tube. He used biased negative resistance crystal junctions to build solid-state amplifiers, oscillators, and amplifying and regenerative radio receivers, 25 years before the invention of the transistor. Later he even built a superheterodyne receiver.

He died in 1942, so a few years before the Bell Labs point contact transistor was invented.

https://en.wikipedia.org/wiki/Crystal_detector#Crystodyne:_negative_resistance_diodes

http://www-smirc.stanford.edu/papers/chapter1.pdf

 

[BillTre]

TIL learned that National Napping Day was created to help make up for the sleep lost during the time change from daylight savings.
It seems the day celebrated varies, often just after the time change.

NATIONAL NAPPING DAY HISTORY
William Anthony, Ph.D., a Boston University Professor, and his wife, Camille Anthony, created National Napping Day in 1999 as an effort to spotlight the health benefits to catching up on quality sleep. "We chose this particular Monday because Americans are more ‘nap-ready’ than usual after losing an hour of sleep to daylight saving time," Anthony said in B.U.’s press release.

 

[berkeman]

TIL about the Kopp-Etchells Effect, which can produce glowing rings from propeller aircraft operating in sandy environments. I'd never heard of this striking visual effect before...

https://en.wikipedia.org/wiki/Kopp–Etchells_effect

Helicopter rotors are fitted with abrasion shields along their leading edges to protect the blades. These abrasion strips are often made of titanium, stainless steel, or nickel alloys, which are very hard, but not as hard as sand. When a helicopter flies low to the ground in sandy environments, sand can strike the metal abrasion strip and cause erosion, which produces a visible corona or halo around the rotor blades.

The effect is caused by the pyrophoric oxidation of the ablated metal particles.[6][7] In this way, the Kopp–Etchells effect is similar to the sparks made by a grinder, which are also due to pyrophoricity.[8] When a speck of metal is chipped off the rotor, it is heated by rapid oxidation. This occurs because its freshly exposed surface reacts with oxygen to produce heat. If the particle is sufficiently small, then its mass is small compared to its surface area, and so heat is generated faster than it can be dissipated. This causes the particle to become so hot that it reaches its ignition temperature. At that point, the metal continues to burn freely.[9]

Abrasion strips made of titanium produce the brightest sparks,[2][10] and the intensity increases with the size and concentration of sand grains in the air.[11]

 

[phinds]

Very cool. Thanks for posting, Mike.

 

[sbrothy]

I must admit this isn't exactly new knowledge to me but perhaps some of you (at least those without a degree in CS) haven't heard of it. Computers have been using so called speculative execution for optimization for some time. It's not a new thing and it's not the only optimization technique in use. I still find it kinda creepy. When we're talking about AI and the dangers thereof I'm sometimes baffled with how convoluted and advanced "ordinary" computers have become.

I'd love to see spintronics become a reality but I doubt it'll be in my lifetime - if at all. When I say becmoe reality I mean ofcourse in more widespread use. Shouldn't it theoretically be able to double processing power?

https://m.xkcd.com/1938/

 

[Swamp Thing]

https://m.xkcd.com/1938/

Is rowhammer really a thing?

 

[sbrothy]

Is rowhammer really a thing?

Yup. https://en.wikipedia.org/wiki/Row_hammer

the milw0rm site was the goto site foor up to date exploits like that. It's closed now though. I haven't kept up. Dunno if anyone took up the challenge.

And if you want to learn to "hack", the magic word to search for is "pentesting" (as in penetration testing).

 

[sbrothy]

Yup. https://en.wikipedia.org/wiki/Row_hammer

the milw0rm site was the goto site foor up to date exploits like that. It's closed now though. I haven't kept up. Dunno if anyone took up the challenge.

And if you want to learn to "hack", the magic word to search for is "pentesting" (as in penetration testing).

Speaking of hacking this one is right on the money:

https://xkcd.com/932/

I don't remember how many web- and appservers I've set up. But if anyone managed to gain root access the vast majority was merely a frontend for some mainframe with old legacy code noone dared touch.

The webserver would talk with the backend using either CICS, MSMQ or - oh the horror *shudder* - an encrypted socket using a bespoke protocol.

If database access was needed the specific data, which would be the bare minimum, would likely be cached on a dedicated server where the mainframe would unload a bunch of data from time to time. Virtually a cul-de-sac.

But then you read about exploits like Rowhammer and you realize the lengths people will go to. And sometimes just for the challenge itself!

I'm flabbergasted! (This entire post was just an excuse for using that word;) ).

 

[mathwonk]

Am I the only one to check the expansions in Bill Tre's pi posts? I was struck by the apparent error in the berry pie version, which looked off to me, although as it turns out merely (correctly) rounded up. The pearls before swine version is more in line with my approach to such things, as being only truncated. If you own Euler's Introduction to Analysis of the infinite, or even its earlier Latin version I believe, you have no doubt been shocked by the error in about the 113th place of the expansion of pi in the work of that famous Swiss citizen, (who was apparently unknown to the apocryphal Orson Welles). I presume this error the work of the printer.

 

[BillTre]

"Atheism is a non-prophet organization".
--George Carlin

 

[mathwonk]

I have my own issues with Wikipedia. I often find useful information there about things I am ignorant of, but do not post on things I feel knowledgable about, after one experience, when I tried to post an answer to a question about the Riemann-Roch theorem.

My elementary and concrete version was quickly altered and eventually erased, in favor of a generic abstract modern account, written by someone possibly less conversant with, or less appreciative of, classical sources.

So to me the problem with Wikipedia is that everyone has license to edit work of others, leading to a sort of generic second or third hand homogenization of readily available treatments. Thus I often prefer individual signed explanations such as one can find here, and on mathoverflow, and tend to restrict my contributions to such sites.

 

[Swamp Thing]

I have often wondered what could have led Fourier to consider expressing the initial temperature profile in a rod in terms of many "wavy things" added up together, when there is no waviness at all in the problem itself.

But today I learned that he started out with a simpler problem -- the diffusion of heat along an "anchor ring", a metal ring used to attach a chain to an anchor. Of course, the temperature profile on the ring is periodic in the sense that it repeats as you move along the ring over and over; and this gave him the germ of the idea of expressing any temperature profile on the ring in terms of many waves that "close" exactly over the ring.

https://www.yalescientific.org/2010/12/fourier-transform-natures-way-of-analyzing-data/#:~:text=The question itself was complicated,sinusoidal waves around the ring.

https://iopscience.iop.org/article/10.1088/1361-6404/acdf2e/pdf

There are also accounts that claim he went "eureka" when he happened to see an actual anchor ring, but this seems to be historically uncertain.

 

[jack action]

Today I learned that Canada has its own "Grand Canyon" called The Gully but ... it's underwater! It's a protected area, home to many marine species.

​

The Gully is located approximately 200 kilometres off Nova Scotia to the east of Sable Island on the edge of the Scotian Shelf. Over 65 kilometres long and 15 kilometres wide, the Gully is the largest underwater canyon in the western North Atlantic. The movement of glaciers and meltwater erosion formed the canyon approximately 150,000 to 450,000 years ago, when much of the continental shelf was above the current sea level.

The Gully ecosystem encompasses shallow sandy banks, a deep-water canyon environment, and portions of the continental slope and abyssal plain, providing habitat for a wide diversity of species. The Gully’s size, shape, and location have an effect on currents and local circulation patterns, concentrating nutrients and small organisms within the canyon.

The Gully is home to the endangered Scotian Shelf population of Northern bottlenose whales and is an important habitat for 15 other species of whales and dolphins. Tiny plankton, a variety of fish such as sharks, tunas and swordfish, and seabirds inhabit surface waters, while halibut, skates, cusk and lanternfish can be found as deep as one kilometre. The ocean floor supports crabs, sea pens, anemones, brittle stars, and approximately 30 species of cold-water corals.

 

[docnet]

Should have posted how I found out about it - a recent deployment:

The video is a minute and a half and mostly air traffic control communications, but there's some mobile phone footage at the end of the thing coming down.

Wow, that's wild. I wonder if the airplane has to be scrapped afterwards because of safety concerns.

 

[Ibix]

Wow, that's wild. I wonder if the airplane has to be scrapped afterwards because of safety concerns.

According to the Wiki link in the post above the one you quoted, "The goal of employing this system is the survival of the crew and passengers and not necessarily the prevention of damage to the airframe". So you definitely need to take it to the shop before taking off again...

 

[DaveE]

I wonder if the airplane has to be scrapped afterwards because of safety concerns.

The vertical speed is about 17 knots (1700 fpm). Then there's the question of what you hit at that speed. So the expectation is that the airframe will be scrapped. But, IDK, maybe if your lucky and spend a bunch of money... I wouldn't buy that airplane.

 

[Astronuc]

YIL,

(Reuters) -Telecom company AT&T said on Saturday that it is investigating a data set released on the "dark web" about two weeks ago, and said that its preliminary analysis shows it has impacted approximately 7.6 million current account holders and 65.4 million former account holders.

The company said the data set appears to be from 2019 or earlier. AT&T said it does not have evidence of unauthorized access to its systems resulting from the incident.

https://finance.yahoo.com/news/t-says-leaked-data-set-142120306.html

 

[Astronuc]

TIL about Lincombian-Ranisian-Jerzmanowician complex.
https://en.wikipedia.org/wiki/Lincombian-Ranisian-Jerzmanowician

The technocomplex is named after findings in Kents Cavern, Lincombe Hill, Torquay (Devon, England), the cave of Ilsenhöhle in Ranis (Thuringia, Germany), and the Jerzmanowicien cave in Ojców (Kraków County, Poland).

https://www.msn.com/en-us/news/tech...timeline-of-ancient-human-history/ar-BB1iaEuR

https://www.cnn.com/2024/02/01/europe/ancient-tools-humans-neanderthals-europe-scn/index.html

Nature - Homo sapiens reached the higher latitudes of Europe by 45,000 years ago
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10849966/

 

[F X]

OK now I just learned about that as well. Thanks

 

[gmax137]

He just grinned and shook my hand. "No", was all he said!

So, I went to the webz to read the entire lyrics of "The Weight," and found this:
"Take a load off Fanny..."
I had always heard "Annie" not "Fanny." That's after listening to Big Pink for 50 years.

 

[DaveE]

So, I went to the webz to read the entire lyrics of "The Weight," and found this:
"Take a load off Fanny..."
I had always heard "Annie" not "Fanny." That's after listening to Big Pink for 50 years.

TIL "Fanny" was a Jewish bookseller in NYC.
https://forward.com/culture/music/3...and-roll-songs-of-all-time-was-inspired-by-a/

 

[Astronuc]

So, I went to the webz to read the entire lyrics of "The Weight," and found this:
"Take a load off Fanny..."
I had always heard "Annie" not "Fanny." That's after listening to Big Pink for 50 years.

I thought it was Manny.


My favorite song by The Band is Chest Fever. I do not get the lyrics, but I like the organ and piano. I never did get poetry, although there are some poems I like and do understand.





Lyrics

I know she's a tracker
Any style that would back her
They say she's a chooser
But I just can't refuse her
She was just there, but then she can't be here no more
And as my mind unweaves
I feel the freeze down in my knees
But just before she leaves, she receives
She's been down in the dunes
And she's dealt with the goons
Now she drinks from a bitter cup
I'm trying to get her to give it up
She was just here, I fear she can't be there no more
And as my mind unweaves
I feel the freeze down in my knees
But just before she leaves, she receives
It's long, long when she's gone
I get weary holding on
Now I'm coldly fading fast
I don't think I'm gonna last very much longer
"She's stoned, " said the Swede
And the moon calf agreed
But I'm like a viper in shock
With my eyes in the clock
She was just there somewhere and here I am again
And as my mind unweaves
I feel the freeze down in my knees
But just before she leaves, she receives

 

[Tom.G]

Those lyrics read like a drug hallucination!

 

[Hornbein]

Those lyrics read like a drug hallucination!

It was the 60's. They got their big break as Bob Dylan's band. He was/is highly respected for this kind of thing.

I don't care about sense in lyrics. If it sounds good, it is good. Lyrics are also at the bottom of my musical priority list. My focus goes elsewhere.

 

[BillTre]

TIL that Lucy the fossil (named for the Beatle's song "Lucy in the Sky with Diamonds") is 50 years old (time above the ground).
Closer to 3 million in total age.

 

[BillTre]

TIL there are RNAs in mouse neurons that have exist in cells 2 years (a significant part of the mouse's lifespan). Very unusual.
They are thought to have something to do with maintaining chromatin (chromatin vs. heterochromatin) structure in particular neurons.

 

[Swamp Thing]

Today I learned that in one of his Lectures, Feynman estimated that the age of the stuff at the center of the earth is about a day older than stuff at the surface, a la General Relativity. This idea then remained embedded in the conventional wisdom canon for decades. Only in 2016 did someone fact-check Feynan on this ... https://iopscience.iop.org/article/10.1088/0143-0807/37/3/035602 ... Turns out, GR says the core is around 2.5 years older than the surface.

Edit: Core younger. Thanks, collinsmark.

 

[collinsmark]

Today I learned that in one of his Lectures, Feynman estimated that the age of the stuff at the center of the earth is about a day older than stuff at the surface, a la General Relativity. This idea then remained embedded in the conventional wisdom canon for decades. Only in 2016 did someone fact-check Feynan on this ... https://iopscience.iop.org/article/10.1088/0143-0807/37/3/035602 ... Turns out, GR says the core is around 2.5 years older than the surface.

I think you mean "younger." But whatever the case, interesting.

 

[Orodruin]

Turns out, GR says the core is around 2.5 years older than the surface.

Younger. The article says so as well.

 

[pinball1970]

T.I.L. Voyager 1 problem has been identified

https://blogs.nasa.gov/voyager/2024...e-of-voyager-1-issue-are-working-on-solution/

 

[Swamp Thing]

TIL that magnetic compasses are made slightly unbalanced so that they won't scrape against the glass or the lower plate due to magnetic dip, and you don't need to tilt the case to keep the pointer free. The compasses' imbalance is tailored for the intended latitude.

And then there are "global" compasses that use a little trick to solve this problem...

 

[Hornbein]

TIL that magnetic compasses are made slightly unbalanced so that they won't scrape against the glass or the lower plate due to magnetic dip, and you don't need to tilt the case to keep the pointer free. The compasses' imbalance is tailored for the intended latitude.

And then there are universal compasses that use a little trick to solve this problem...

Is the imbalance in an angled plane of magnetization?

 

[Swamp Thing]

Yes, they add a bit of weight that opposes the effect of dip (inclination).

 

[pinball1970]

T.I.L An eclipse and supernova visible in the same year?

EDIT: Nova not supernova

https://blogs.nasa.gov/Watch_the_Skies/2024/02/27/view-nova-explosion-new-star-in-northern-crown/

 

[Orodruin]

T.I.L An eclipse and supernova visible in the same year?

https://blogs.nasa.gov/Watch_the_Skies/2024/02/27/view-nova-explosion-new-star-in-northern-crown/

Nova, not supernova.

A star that goes supernova will not do so again.