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1. harima+(OP)[view] [source] 2020-04-27 00:02:35
I don't know if this would be my "one question" if I could ask the most brilliant minds in science, but something that always bothered me:

When I took physics they basically said "at first scientists were disturbed by the fact that magnets imply that two objects are interacting without any physical contact, but then Faraday came along and said 'the magnets are actually connected by invisible magnetic field lines' and that resolved everything."

How does saying "but what if there's invisible lines connecting them" resolve anything? To be clear, I'm not objecting to any of the actual electromagnetic laws or using field lines to visualize magnetic fields. It's just that I don't get how invoking invisible lines actually explains anything about how objects are able to react without physical contact.

(Also, it is not lost on me I that this question boils down to "fraking magnets, how do they work?")

replies(8): >>eranat+i1 >>Jabavu+C2 >>WhiteS+13 >>slazar+63 >>juped+T5 >>keldar+a6 >>rrss+2n >>rom163+7G3
2. eranat+i1[view] [source] 2020-04-27 00:10:52
>>harima+(OP)
This, gravity, and quantum mechanics, I think are things that people just accept as is, I don't think anyone really knows how or why it works, it just works. It could be that our brains are not wired to understand how two things can be pulling each other without anything physically connecting them. My knee jerk explanation is that we live in a simulation, and that the simulation is not in anything like a physical world, and we are just not wired to grasp it, just like an ant won't be able to learn learn calculus.
3. Jabavu+C2[view] [source] 2020-04-27 00:22:47
>>harima+(OP)
It changes the problem from one of action at a distance to local interaction. Instead of "field lines", I would say "field". Field lines are just one way of visualizing a field.

So, if we don't have the notion of fields, then we have a kind of situation of how does object A know about remote object B. Like how does one object know about the motions of literally every other object in the Universe. Perplexing.

Once you come up with the idea of a field, okay you have to at some level accept that there are fields that permeate all of space. But what this intellectual cost buys you is that now an object only has to sense the field local to it to respond to all objects in the universe.

Think of objects bobbing on the ocean. One way to conceptualize that is that any object anywhere could cause this object here to bob in some way. How does this object know about all the other objects? Instead we could say that there is ocean everywhere. Locally, objects bobbing put ripples into the ocean. Locally, ripples cause objects to bob. Each object no longer needs to "know about" every other object it just needs to react to the ripples at its location, and the ripples get sent out from its location.

Does this help?

4. WhiteS+13[view] [source] 2020-04-27 00:27:00
>>harima+(OP)
I'm no expert in the matter, but I guess the problem is somewhat solved as the magnet then interacts with the field lines and these with the other magnet. It depends on how real you believe these invisible magnetic lines are. The magnetic field turned out to be a very real entity, as when it is perturbed these perturbations travel at the speed of light, and the second magnet feels them with a slight delay. The perturbations also manifest themselves as EM radiation/light.
5. slazar+63[view] [source] 2020-04-27 00:28:35
>>harima+(OP)
Gravity and magnetism are two phenomena that I always imagined could actually be explained in higher dimensions (except we can't see those higher dimensions so it'd be just speculation).

Imagine two circles in 2D that repel each other the closest you get them together, like magnets do. In 2D it would look like they're interacting at a distance, but maybe in 3D they're two cylinders that are a bit flexible, that are actually touching at the ends, but not in the 2D plane you're observing. The interaction is "properly physical" in 3D but in the 2D plane it seems magical.

That's a way that I imagine it in 2D vs 3D, so this might be similar in 3D vs ND, where N > 3. Of course this is all baseless speculation, but it seems kinda plausible in my head.

Edit: bad drawing of what I meant: https://imgur.com/362tcHg

replies(2): >>OkayPh+LL >>aetern+7n1
6. juped+T5[view] [source] 2020-04-27 00:55:28
>>harima+(OP)
It's local (propagates continuously through space, no faster than the speed of light) and if you want you can view it as mediated by particles (photons), although just viewing it as the EM field is fine too (and certainly no less local). So is gravity, which was spooky action at a distance for even longer, once you invent GR.
7. keldar+a6[view] [source] 2020-04-27 00:58:39
>>harima+(OP)
I'm a physicist specifically working with magnetic systems, but I have very little pre-graduate teaching experience, so take this attempt to answer the question with a grain of salt.

The reason some people regard Faraday's original explanation of the eponymous law (it is worth noting that at the time it was widely regarded as inadequate and handwavy) as illuminating is because Faraday visualized his "lines of force" as literal chains of polarized particles in a dielectric medium, thereby providing a seemingly mechanistic local explanation of the observed phenomena. Not much of this mindset survived Maxwell's theoretical program and it has very little to do with how we regard magnetism today. Instead, the unification of electricity and magnetism naturally arises from special relativity, whereas the microscopic basis of magnetism requires quantum mechanics. There isn't really any place for naive contact mechanics in the modern picture of physics, so in that sense I would regard Faraday's view as misleading.

Finally, I can't end any "explanation" of magnetism without linking the famous Feynman interview snippet [1] where he's specifically asked about magnetism. It doesn't answer your question directly, but it's worth watching all the more because of it.

[1] https://www.youtube.com/watch?v=MO0r930Sn_8

replies(2): >>Jabavu+g7 >>carapa+S22
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8. Jabavu+g7[view] [source] [discussion] 2020-04-27 01:10:38
>>keldar+a6
That interview is so good! What a dick, but what a teacher!
replies(1): >>onioni+u41
9. rrss+2n[view] [source] 2020-04-27 04:38:10
>>harima+(OP)
I don't think the invisible 'lines of force' really resolved anything in the minds of the 19th century scientists, but what eventually did was acceptance of Faraday's speculation that the lines of force were physically real and existed as some change of state in some medium that existed throughout space.

Maxwell picked up this idea and ran with it, developing a mathematical theory for the dynamics of the electromagnetic field. Instead of one object somehow magically interacting at a distance, interactions between objects resulted from changes in the electromagnetic field that propagated through space.

The final paragraphs of Maxwell's "Treatise on Electricity and Magnetism" are somewhat relevant.

This is 30-40 years after Faraday first wrote about lines of force, and there still wasn't really consensus about how to explain electromagnetic phenomena.

[emphasis added by me]

> Chapter XXII: Theories of Action at a Distance

> ...

> There appears to be in the minds of these eminent men, some prejudice, or a priori objection, against the hypothesis of a medium in which the phenomena of radiation of light and heat, and the electric actions at a distance take place. It is true that at one time those who speculated as to the causes of physical phenomena, were in the habit of accounting for each kind of action at a distance by means of a special aethereal fluid, whose function and property it was to produce these actions. They filled all space three and four times over with aethers of different kinds, the properties of which were invented merely to 'save appearances,' so that more rational enquirers were willing rather to accept not only Newton's definite law of attraction at a distance, but even the dogma of Cotes, that action at a distance is one of the primary properties of matter, and that no explanation can be more intelligible than this fact. Hence the undulatory theory of light has met with much opposition, directed not against its failure to explain the phenomena, but against its assumption of the existence of a medium in which light is propagated.

> We have seen that the mathematical expressions for electrodynamic action led, in the mind of Gauss, to the conviction that a theory of the propagation of electric action would be found to be the very key-stone of electrodynamics. Now we are unable to conceive of propagation in time, except either as the flight of a material substance through space, or as the propagation of a condition of motion or stress in a medium already existing in space.

> Hence all these theories lead to the conception of a medium in which the propagation takes place, and if we admit this medium as a hypothesis, I think it ought to occupy a prominent place in our investigations, and that we ought to endeavour to construct a mental representation of all the details of its actions, and this has been my constant aim in this treatise.

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10. OkayPh+LL[view] [source] [discussion] 2020-04-27 10:07:09
>>slazar+63
There are models using higher-dimenions (and lower dimensions, and factional dimensions) to model physical phenomena, but the problem with a lot of them is that you end up with the "fitting n points to an n degree polynomial" problem. It's trivial to create a model that agrees with all observed data, it's a lot harder to make a model that accurately predicts unseen data.
replies(1): >>meesle+Nl5
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11. onioni+u41[view] [source] [discussion] 2020-04-27 13:29:37
>>Jabavu+g7
What I see at the beginning of that video is somebody who doesn’t want to spend the energy answering a complex question. Then, in the process of dismissing the question he gets drawn in and can’t help himself from really getting into it.

I don’t know anything about Feynman beyond vaguely associating his name with science, but watching this makes me want to seek out more from him.

replies(1): >>strgcm+X91
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12. strgcm+X91[view] [source] [discussion] 2020-04-27 14:10:32
>>onioni+u41
You're in for quite a treat then. It sounds like you might have more of an interest in his technical work and scientific contributions and teaching materials (of which there is plenty, and of high quality), but personally I quite enjoyed this book of his as well: https://en.wikipedia.org/wiki/Surely_You%27re_Joking,_Mr._Fe...!
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13. aetern+7n1[view] [source] [discussion] 2020-04-27 15:32:23
>>slazar+63
Gravity is explained that way, it is a curvature in spacetime (4D): https://www.youtube.com/watch?v=CvN13ZE544M
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14. carapa+S22[view] [source] [discussion] 2020-04-27 19:59:34
>>keldar+a6
That Feynman snippet was so awesome. Flawless. Thanks for sharing it.
15. rom163+7G3[view] [source] 2020-04-28 10:44:04
>>harima+(OP)
The answer is related to Relativity. Read this: https://ocw.mit.edu/courses/materials-science-and-engineerin...
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16. meesle+Nl5[view] [source] [discussion] 2020-04-28 21:09:22
>>OkayPh+LL
Fascinating thought! Makes sense though. Given n inputs and outputs, you could literally make an if-statement that solves nothing but gives you the 'right answer'. Actually understanding the fundamentals (often unseen) of a problem to then create an elegant, holistic solution that almost prophetically seems to predict the future is the current peak of human thought achievement, IMO.
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