5 ms·

The Electromagnetic Force of Fridge Magnets

77 points by dnetesn 5y ago

thunderbong 5y ago
https://archive.is/q60yY https://archive.is/q60yY
BenjiWiebe 5y ago
According to https://www.theguardian.com/science/blog/2010/jun/09/science-cake-baking-andy-connelly https://www.theguardian.com/science/blog/2010/jun/09/science..., the rising action of cake is mostly from water boiling and leavening agents producing CO2: "Carbon dioxide and water vapour account for approximately 90% of the subsequent expansion of the batter, the remaining 10% being due to thermal expansion."
- gerdesj 5y ago
  Tell that to my mother! She was an absolutely belting cook but always ended up with a caldera in her sponge cakes. She was able to make clotted cream from first principles - she was Devonian. She also introduced pasties to several parts of West Germany in the 1970s/80s. The food traffic went both ways in Germany and I have a massive fondness for schnitzels - "Zigeuner" (gipsy, I think) and "Jager" (hunter - deffo). Mum was also a soldier as well as dad (they were both Captains when they met in Scotland) but she was told to get out what with her being a woman and hanging out with a male Army occifer. That was back in the late 1960s. Times have changed a lot since then. Anyway, cakes. mmmm cakes.
  - emmelaich 5y ago
    Caldera you say? Some cheeky person has put Penn and Teller's recipe up on epicurious ... https://www.epicurious.com/recipes/member/views/swedish-lemon-angels-1209952 https://www.epicurious.com/recipes/member/views/swedish-lemo...
gerdesj 5y ago
The OP is a lovely work and beautifully illustrated. I recently spent 18 months working from our dining room table. I regularly have to worry about swapping out broken hard discs in my work data centre. I took a 3.5" SMART failed SAS drive apart fairly recently and turned the two magnets into fridge magnets. My wife cannot physically pull them off (ooerr missus) the fridge directly. She has to slide them to an edge or use a lever. The grandkids' latest artistic efforts stay stuck to the fridge and so do appointment cards etc. My step-mum grabbed at one of those because she thought it was falling off and the door opened instead and then the painting ripped. Calamity! We got the little darling to do a copy and great granny calmed down a bit. It's a shame that more people aren't commenting on this page. It is lovely.
- amelius 5y ago
  > It's a shame that more people aren't commenting on this page. It is lovely. The illustrations are nice, but they often make so little sense: the topic is mostly about molecular interactions, yet the illustrations show macroscopic scenery. Also, the entire article reads like a grab-bag of Wikipedia entries, and only the first paragraph of each entry. I thought this was going to be an in-depth article about magnets! Furthermore, the entire page including the text is an image, which is not how the web is supposed to work.
  - CamperBob2 5y ago
    Also, their induction hob appears to be on fire.
- duffyjp 5y ago
  I use hard drive magnets as key hooks. Keys themselves don't stick, but the keyring does and holds great. I put my business card under mine and the wife's under hers both to label and to have a way to eventually remove them from the fridge. I also superglued two to a pair of old Xeon CPUs that look really cool and have enough lip to be easily removed. They make ideal fridge magnets!
- Fezzik 5y ago
  You reminded me of an old trick (now expired) that my grandma taught me: take the magnet out of used Sonicare toothbrush heads, wrap the magnet in electrical tape creating a pull-tab, and you have a rather powerful refrigerator magnet! Sonicare removed the original magnet vibrating mechanism quite a while ago so this no longer works, but I love creative reuses like this for items.
kragen 5y ago
Typically fridge magnets are made of ferrite, which is ferrimagnetic, not ferromagnetic, as has been known since 01948; though, if you recycle some hard-disk voice-coil magnets, you will have truly ferromagnetic fridge magnets. And this illustrates a problem with all of these explanations: none of them is precise enough to yield falsifiable predictions. (The fact that this one is wrong is, by comparison, minor. Incorrect reasoning from evidence can be corrected. Erroneous observations can be corrected with correct observations. But vague explanations can always be lawyered to fit the evidence.) Although these explanations are written with scientific words, they are not scientific explanations; they belong to the same genre as Kipling's Just So Stories or quantum-healing pseudoscience. Or, in some cases, Life Hacks: if you drip drops of water on your "hob" and they just sit there because it's an induction "hob", you've at least empirically validated that you don't see the Leidenfrost effect. (Let's hope you know how to reseason your cast-iron skillet after you successfully reproduce the Leidenfrost effect on that.) But you'll never be able to falsify the Leidenfrost effect working from this bullshit picture, because it could always just be that your "hob" isn't hot enough; to have a falsifiable prediction, you'd need to know that water's Leidenfrost point is 193°C normally, but can be as high as 210° or as low as 150° depending on circumstances. If you have your skillet at 250° and water drops are still not floating around in a spooky way, you have falsified the prediction. (The text, "When a liquid is on a surface hotter than its boiling point, drops float on a layer of vapor," could be read as claiming that the Leidenfrost point is the same temperature as the boiling point, which is wrong.) Science is what comes with a demonstration. How would you tell, for example, if your cake is frothing up because of Charles's Law, because water is vaporizing, because dissolved gas is coming out of solution, because baking soda is being decomposed by heat, or because baking soda is being neutralized by an acid? How would you tell if your saliva is missing amylase, or your bread is missing starch? It's possible to do it, but you need more than a Just So Story that says "fluffy texture" or "aids digestion". What's worse is the kind of "science" classes that consist of memorizing and regurgitating this kind of discourse; essentially the exams are testing your ability to memorize (or guess) the teacher's password, reducing science to the level of slogan-shouting politics. Feynman had a wonderful story about how this disease had taken over the Brazilian university system, to the point that his physics students were surprised that sunlight reflected off the ocean was polarized. I think this kind of "science" popularization is to blame for the rise of quantum healing and the like (not to mention the devastation of the curent pandemic, as I sort of argue in https://news.ycombinator.com/item?id=28332889 https://news.ycombinator.com/item?id=28332889). Once you remove the evidence and empirical grounding from a scientific explanation, you can't expect the vulgar to magically intuit that the evidence is really there, behind the scenes; they won't be able to tell the difference from Deepak Chopra bullshit. Because the difference is the part that's been intentionally left out.
irrational 5y ago
For anyone else who didn’t know, a hob is the British word for the top of a stove (the stovetop). Though, according to 2 dictionaries I checked, it more usually means hobgoblin in British English. I wonder if they have puns about these two meanings.
- kragen 5y ago
  I was thinking maybe they shared a common origin, but apparently not: https://www.etymonline.com/word/hob https://www.etymonline.com/word/hob I think speaking of stovetops is around two orders of magnitude more common than speaking of hobgoblins among BrE-speakers nowadays.
- PaulDavisThe1st 5y ago
  birth BrE here, 32 years of AmE ... never ever heard "hob" as related to "hobgoblin".
_Microft 5y ago
The article is nice but the title could be better. I, for one, expected the content to be about Halbach arrays. This is a particular way of arranging magnets that increases the magnetic field on one side of the array while decreasing it on the other. It is often used for fridge magnets. https://en.wikipedia.org/wiki/Halbach_array https://en.wikipedia.org/wiki/Halbach_array

77 points by dnetesn 5y ago

https://archive.is/q60yY https://archive.is/q60yY

According to https://www.theguardian.com/science/blog/2010/jun/09/science-cake-baking-andy-connelly https://www.theguardian.com/science/blog/2010/jun/09/science..., the rising action of cake is mostly from water boiling and leavening agents producing CO2: "Carbon dioxide and water vapour account for approximately 90% of the subsequent expansion of the batter, the remaining 10% being due to thermal expansion."

gerdesj 5y ago
Tell that to my mother! She was an absolutely belting cook but always ended up with a caldera in her sponge cakes. She was able to make clotted cream from first principles - she was Devonian. She also introduced pasties to several parts of West Germany in the 1970s/80s. The food traffic went both ways in Germany and I have a massive fondness for schnitzels - "Zigeuner" (gipsy, I think) and "Jager" (hunter - deffo). Mum was also a soldier as well as dad (they were both Captains when they met in Scotland) but she was told to get out what with her being a woman and hanging out with a male Army occifer. That was back in the late 1960s. Times have changed a lot since then. Anyway, cakes. mmmm cakes.
- emmelaich 5y ago
  Caldera you say? Some cheeky person has put Penn and Teller's recipe up on epicurious ... https://www.epicurious.com/recipes/member/views/swedish-lemon-angels-1209952 https://www.epicurious.com/recipes/member/views/swedish-lemo...

gerdesj 5y ago

The OP is a lovely work and beautifully illustrated. I recently spent 18 months working from our dining room table. I regularly have to worry about swapping out broken hard discs in my work data centre. I took a 3.5" SMART failed SAS drive apart fairly recently and turned the two magnets into fridge magnets. My wife cannot physically pull them off (ooerr missus) the fridge directly. She has to slide them to an edge or use a lever. The grandkids' latest artistic efforts stay stuck to the fridge and so do appointment cards etc. My step-mum grabbed at one of those because she thought it was falling off and the door opened instead and then the painting ripped. Calamity! We got the little darling to do a copy and great granny calmed down a bit. It's a shame that more people aren't commenting on this page. It is lovely.

amelius 5y ago
> It's a shame that more people aren't commenting on this page. It is lovely. The illustrations are nice, but they often make so little sense: the topic is mostly about molecular interactions, yet the illustrations show macroscopic scenery. Also, the entire article reads like a grab-bag of Wikipedia entries, and only the first paragraph of each entry. I thought this was going to be an in-depth article about magnets! Furthermore, the entire page including the text is an image, which is not how the web is supposed to work.
- CamperBob2 5y ago
  Also, their induction hob appears to be on fire.
duffyjp 5y ago
I use hard drive magnets as key hooks. Keys themselves don't stick, but the keyring does and holds great. I put my business card under mine and the wife's under hers both to label and to have a way to eventually remove them from the fridge. I also superglued two to a pair of old Xeon CPUs that look really cool and have enough lip to be easily removed. They make ideal fridge magnets!
Fezzik 5y ago
You reminded me of an old trick (now expired) that my grandma taught me: take the magnet out of used Sonicare toothbrush heads, wrap the magnet in electrical tape creating a pull-tab, and you have a rather powerful refrigerator magnet! Sonicare removed the original magnet vibrating mechanism quite a while ago so this no longer works, but I love creative reuses like this for items.

kragen 5y ago

Typically fridge magnets are made of ferrite, which is ferrimagnetic, not ferromagnetic, as has been known since 01948; though, if you recycle some hard-disk voice-coil magnets, you will have truly ferromagnetic fridge magnets. And this illustrates a problem with all of these explanations: none of them is precise enough to yield falsifiable predictions. (The fact that this one is wrong is, by comparison, minor. Incorrect reasoning from evidence can be corrected. Erroneous observations can be corrected with correct observations. But vague explanations can always be lawyered to fit the evidence.) Although these explanations are written with scientific words, they are not scientific explanations; they belong to the same genre as Kipling's Just So Stories or quantum-healing pseudoscience. Or, in some cases, Life Hacks: if you drip drops of water on your "hob" and they just sit there because it's an induction "hob", you've at least empirically validated that you don't see the Leidenfrost effect. (Let's hope you know how to reseason your cast-iron skillet after you successfully reproduce the Leidenfrost effect on that.) But you'll never be able to falsify the Leidenfrost effect working from this bullshit picture, because it could always just be that your "hob" isn't hot enough; to have a falsifiable prediction, you'd need to know that water's Leidenfrost point is 193°C normally, but can be as high as 210° or as low as 150° depending on circumstances. If you have your skillet at 250° and water drops are still not floating around in a spooky way, you have falsified the prediction. (The text, "When a liquid is on a surface hotter than its boiling point, drops float on a layer of vapor," could be read as claiming that the Leidenfrost point is the same temperature as the boiling point, which is wrong.) Science is what comes with a demonstration. How would you tell, for example, if your cake is frothing up because of Charles's Law, because water is vaporizing, because dissolved gas is coming out of solution, because baking soda is being decomposed by heat, or because baking soda is being neutralized by an acid? How would you tell if your saliva is missing amylase, or your bread is missing starch? It's possible to do it, but you need more than a Just So Story that says "fluffy texture" or "aids digestion". What's worse is the kind of "science" classes that consist of memorizing and regurgitating this kind of discourse; essentially the exams are testing your ability to memorize (or guess) the teacher's password, reducing science to the level of slogan-shouting politics. Feynman had a wonderful story about how this disease had taken over the Brazilian university system, to the point that his physics students were surprised that sunlight reflected off the ocean was polarized. I think this kind of "science" popularization is to blame for the rise of quantum healing and the like (not to mention the devastation of the curent pandemic, as I sort of argue in https://news.ycombinator.com/item?id=28332889 https://news.ycombinator.com/item?id=28332889). Once you remove the evidence and empirical grounding from a scientific explanation, you can't expect the vulgar to magically intuit that the evidence is really there, behind the scenes; they won't be able to tell the difference from Deepak Chopra bullshit. Because the difference is the part that's been intentionally left out.

irrational 5y ago

For anyone else who didn’t know, a hob is the British word for the top of a stove (the stovetop). Though, according to 2 dictionaries I checked, it more usually means hobgoblin in British English. I wonder if they have puns about these two meanings.

kragen 5y ago
I was thinking maybe they shared a common origin, but apparently not: https://www.etymonline.com/word/hob https://www.etymonline.com/word/hob I think speaking of stovetops is around two orders of magnitude more common than speaking of hobgoblins among BrE-speakers nowadays.
PaulDavisThe1st 5y ago
birth BrE here, 32 years of AmE ... never ever heard "hob" as related to "hobgoblin".

_Microft 5y ago

The article is nice but the title could be better. I, for one, expected the content to be about Halbach arrays. This is a particular way of arranging magnets that increases the magnetic field on one side of the array while decreasing it on the other. It is often used for fridge magnets. https://en.wikipedia.org/wiki/Halbach_array https://en.wikipedia.org/wiki/Halbach_array