9 ms·

Because he didn't know anything about electrons, and the experiment he did involving rubbing amber and glass rods on fur and silk cloth only showed that somethi

by throwway120385 2y ago

Because he didn't know anything about electrons, and the experiment he did involving rubbing amber and glass rods on fur and silk cloth only showed that something was transferred between the two materials, and that when the material containing the substance was brought near to the other material containing the other substance, the property conferred by the substances appeared to negate. If you read Teaching Introductory Physics the author very clearly points out that there is no way of knowing the direction of the charge. It must instead be decided by convention. And Franklin simply chose a convention that we stick with. This is where the need to use mathematical formalism to describe physical concepts becomes clear. Numbers and numeric quantities aren't a real thing that exists in the world. They exist only in our minds. And so does the concept of negation. Calling electrons "negative" is simply a tool for us to model how the substance behaves when it interacts with an "opposing" substance using numbers. We could just as easily have called it "black" or "white" charge, except that we then need to adapt arithmetic and algebra and calculus and so on to work with the concept of "black" or "white" quantities if we are to use them to understand the substance of charge.

akira2501 2y ago
It really seems like had a rationale: "We suppose as aforesaid, That Electrical Fire is a common Element, of which every one of the three Persons abovementioned has his equal Share before any Operation is begun with the Tube. A who stands on Wax, and rubs the Tube, collects the Electrical Fire from himself into the Glass; and his Communication with the common Stock being cut off by the Wax, his Body is not again immediately supply’d. B, who stands upon Wax likewise, passing his Knuckle along near the Tube, receives the Fire which was collected by the Glass from A; and his Communication with the common Stock being likewise cutt off, he retains the additional Quantity received. to C, standing on the Floor, both appear to be electrised; for he having only the middle Quantity of Electrical Fire receives a Spark on approaching B, who has an over-quantity, but gives one to A, who has an under-quantity. If A and B touch each other, the Spark between them is stronger, because the Difference between them is greater. After such Touch, there is no Spark between either of them and C; because the Electrical Fire in all is reduced to the original Equality. If they touch while Electrising, the Equality is never destroyed, the Fire only circulating. Hence have arisen some new Terms among us. We say B (and other Bodies alike circumstanced) are electrised positively; A negatively: Or rather B is electrised plus and A minus. And we daily in our Experiments electrise Bodies plus or minus as we think proper. These Terms we may use till your Philosophers give us better. To electrise plus or minus, no more needs to be known than this; that the Parts of the Tube or Sphere, that are rub’d, do, in the Instant of the Friction, attract the Electrical Fire, and therefore take it from the Thing rubbing: the same Parts immediately, as the Friction upon them ceases, are disposed to give the Fire they have received, to any Body that has less. Thus you may circulate it, as Mr. Watson has shewn; You may also accumulate or subtract it upon, or from any Body, as you connect it with the Rubber or with the Receiver; the Communication with the common Stock being cut off." from Benjamin Franklin's letter to Peter Collison, May 25, 1747.
- throwway120385 2y ago
  But his choice of "positive" or "negative" are entirely a convention of how he wanted to think about things. There's nothing special about the sign other than it made it easier for him to reason about what was happening.
- wycy 2y ago
  It’s really strange reading the words of such an intelligent person beginning to understand something back then that is so fundamental today that even laypeople understand it more scientifically. Really weird, but really cool to get a peek back into a scientific mind in the 1700s.
  - jstanley 2y ago
    > even laypeople understand it more scientifically Laypeople use more scientific-sounding words, sure, but what more scientific way is there to understand something than to have discovered it yourself through experiment?
    - utensil4778 2y ago
      Experimentation brings knowledge, not understanding. Franklin did not understand electricity, but merely observed it. It wasn't until we discovered the electron proper and Maxwell did his work that we-- anyone-- understood electricity. Understanding comes from scientific and academic rigor after the discovery.
      - OJFord 2y ago
        Or just separately from, like Higgs understanding and theorising a boson years before it was actually 'discovered'/detected experimentally.
      - neuralRiot 2y ago
        > It wasn't until we discovered the electron proper I’d even say that we don’t yet fully understand the electron!
pdonis 2y ago
> there is no way of knowing the direction of the charge But there is--otherwise we wouldn't know that Franklin got it backwards. He thought the charge carriers were going one way, and chose the convention he did because he thought it matched the way the charge carriers were going, but it turns out they were going the other way. The signs of the charges are a convention--and the fact that we still use Franklin's convention and it works just fine attests to that--but the direction the charge carriers move is not.
- 2muchcoffeeman 2y ago
  How would you have known this at first from rubbing rods and playing with static electricity?
  - pdonis 2y ago
    I didn't say we can know it just from rubbing rods and playing with static electricity. The post I was responding to said there is no way of knowing it, period. Which is clearly false since we do know it now.
- dotnet00 2y ago
  I think they don't mean it in the literal "you physically can't tell the direction of charge at all" sense. As you say, the very fact that we know the real direction counters that. They mean that within the abstract context of electronics presented in introductory physics, the real direction of charge doesn't matter and cannot be determined. As long as you pick one consistent convention and stick to it, the math will always work out the same, since depending on convention, all the directions and signs are equally flipped. The real direction of charge only matters when you get deep into the details (eg semiconductors). At the level of detail of introductory physics, it's effectively a symmetry, similar to how given the simultaneous flipping of charge, parity and time, you cannot tell the difference.
  - im3w1l 2y ago
    I think there might be a difference. From our experience with air we know that blowing and sucking are not quite the same. Blown air has a much greater capacity for direction than sucked air. I would assume that this is because the when we blow we add additional molecules and we get to decide the inertia of those molecules, but when we suck we take away molecules and they have the inertia they have. I would suspect that the same goes for electrons. An electron gun would (as used in old CRT monitors), would be a very striking example of this - I doubt we could make an electron-hole gun (though shooting positive ions could work, but that's not quite the same thing) - but it may be possible to observe in more normal conditions too?
deleted 2y ago
[deleted]
tzs 2y ago
Suppose that they had realized back then that electricity was going to become one of the most important technologies humans have in the future and decided that they should make a major effort to figure out the direction of the charge so future generations wouldn't get stuck with the wrong convention. All the top scientists, engineers, inventors, and crackpots in the world try to come up with some way to tell. Was there some method reasonably within their reach that would have worked? I'd guess the first thing they would try is weight. The body gaining the charge carriers should gain weight and the body supplying charge carriers should lose weight. That would probably fail because the mass of electrons is very low, and I don't think they had anything that could resolve weights that small. (I'm not even sure we have anything now that can do it). The second approach might again use weight, but with the realizing we don't have to measure what the weight is, just whether it has increased or decreased. So take two weights that are as identical as you can make them and put them on a balance. Seal the balance in an airtight container to prevent random air currents from disturbing it (or pump out the air--the vacuum pump was invented around 100 years earlier), and put it someplace very cold and with very little temperature variation, and adjust the masses until the balance shows no apparent movement for months. Then charge one of the masses and see if the balance can still remain apparently still for months. If it can't, and consistently goes out of balances toward the charged side conclude that side probably has the charge carriers. If it consistently goes toward the other side conclude that the charged side gave up charge carriers. I think that this too would probably fail. The mass difference is too small and isolating the balance sufficiently from outside disturbances is probably too difficult. Could they produce a stream of charges in a vacuum? Let's say they can. Considering the material they had to work with if those were negative they would probably be electrons and if they were positive they would probably be atoms or molecules with a missing electron. They would probably quickly discover that streams of charge in a vacuum are deflected when they bring a magnet near them and figure out that lighter charged things deflect more. They would then discover that all the negative charge streams they produce have carriers of the same mass, but the positive charge stream carries have different masses depending on how they are produced and they all have mass much greater than that of the negative carriers. I think they might lead them to conclude that the negative charge carriers are the fundamental ones.
- deleted 2y ago
jonny_eh 2y ago
In a way he was right, if he was describing the movement of "holes", or the lack of an electron.
- hn_throwaway_99 2y ago
  This is exactly why I think he was wrong. Normally, pretty much everywhere else we use the terms, "positive" denotes the presence or addition of something, while "negative" denotes the absence or subtraction. So while I agree with the GP's comment that Franklin didn't know anything about electrons, so he arbitrarily picked one as negative and the other as positive, now that we do know about the movement of electrons, it kinda sucks because I think Franklin just "picked wrong". I.e. it would make much more sense to me if the absence of electrons (i.e. holes) were negative by convention and an abundance of electrons were denoted as positive.
  - throwway120385 2y ago
    This is pretty much spot on. It sucks after 250 years of hindsight, but I would encourage anyone who wants to think like Franklin to buy an amber rod, a glass rod, a piece of real fur, and a piece of silk, and try experimenting with them and see if you can intuit from physical experiment what the fire is made of and how it passes from one material to another. You can't without the benefit of future knowledge. This is what it feels like to stand on the shoulders of giants.
    - hammock 2y ago
      What is an amber rod?
      - mindcrime 2y ago
        Just what it sounds like: a rod made of amber[1]. [1]: https://en.wikipedia.org/wiki/Amber https://en.wikipedia.org/wiki/Amber
  - mensetmanusman 2y ago
throw0101d 2y ago
> Numbers and numeric quantities aren't a real thing that exists in the world. They exist only in our minds. Is math invented or discovered? * https://www.sfu.ca/~rpyke/cafe/livio.pdf https://www.sfu.ca/~rpyke/cafe/livio.pdf See also "The Unreasonable Effectiveness of Mathematics in the Natural Sciences" by Wigner: * https://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness_of_Mathematics_in_the_Natural_Sciences https://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness...
- lazide 2y ago
  Was ‘Blue’ invented or discovered? Fundamentally, it’s the same type of problem - and really more of a philosophical thing.
  - gavmor 2y ago
    We're using the term "Blue" ambiguously. The term was invented; its assignment and scope were invented, too. The wavelengths themselves were discovered. So there are two different "Blues;" signifier and signified.
  - gavmor 2y ago
    We're using the term "Blue" ambiguously. The term was invented; its assignment and scope were invented, too. The wavelengths themselves were discovered. So there are two different "blues;" sigmifier, and signified.
  - crote 2y ago
    The interesting part is that perception is shaped by language. The Ancient Greeks did not have a word for blue, which led to things like the sky being described as "wine-colored" or "bronze". Similarly, the English "blue" is split into two in Russian: light blue (голубой – goluboy) and deep/dark blue (синий – siniy), a speaker has to choose between them when describing something. The wavelengths may have always existed but colors only become a thing when we draw the arbitrary lines between them.
    - labster 2y ago
mensetmanusman 2y ago
“Numbers and numeric quantities aren't a real thing that exists in the world.” How did your mind gain access to this universal truth? ;)
philipov 2y ago
> We could just as easily have called it "black" or "white" charge And when we found a charge system that had 3 charges rather than just two, we did.
- lynndotpy 2y ago
  Where can I learn more on this? Searching yields nothing.
  - tekno45 2y ago
    https://youtu.be/AOtUo25GB3c?list=TLPQMjEwNjIwMjQajcfSE5215w https://youtu.be/AOtUo25GB3c?list=TLPQMjEwNjIwMjQajcfSE5215w Kinda
  - warhorse10_9 2y ago
    Read up on “color charge.”
  - frutiger 2y ago
    Quarks and gluons, or quantum chromodynamics
  - bradboimler 2y ago
    I imagine they're referring to https://en.m.wikipedia.org/wiki/Quantum_chromodynamics https://en.m.wikipedia.org/wiki/Quantum_chromodynamics
- mr_mitm 2y ago
  It's either six vs two, or three vs one, depending on what you mean by charge. The quarks and gluons can be red, blue, green, antired, antiblue, or antigreen.
  - philipov 2y ago
    I was hoping someone would catch that ;)
adrian_b 2y ago
The reason why which charge is named positive and which is named negative does not matter is because in all the equations that relate electric charge with other measurable physical quantities we never have an electric charge alone, but we always have the product of two electric charges. The value of the product of two electric charges is invariant to the convention chosen for the sign of the electric charge. Numbers and numeric quantities are actually a real thing that exists in the world. They do not exist only in our minds (and in the minds of many other animals who are also able to count until some small number). And so does the concept of negation, which clearly is a property of the world, independent of humans or animals. For other physical quantities, the sign of a quantity is not arbitrary, like for the electric charge, because those are used in expressions that are not invariant to sign changes.
- lupire 2y ago
  Numbers do not exist in the world. Umbers exist outside the world.
  - adrian_b 2y ago
    I do not know if this is a joke about shadows that I did not get, or just a typo, but numbers exist in the world. The world is composed of things. The things are grouped in sets. Numbers are equivalence classes of sets. The set of the medium-sized planets of the Solar System is equivalent in number with the set of the big planets of the Solar System and also equivalent in number with the set of the big satellites of Jupiter (i.e. 4). Such equivalences between sets of things exist regardless if there are any sentient beings that recognize those equivalences and there are circumstances when for instance the evolution in time of some sets of things is determined or influenced by the relationship between the numbers of things that compose each set.
    - juliushuijnk 2y ago
      > The things are grouped in sets. By who?
kabouseng 2y ago
Similar reason why the earth north pole is actually a magnetic south pole :) It was decided by convention / definition. For those whom it isn't clear what I mean. Compass magnet's north poles point north, which is only possible if the earth's north pole is magnetically a south pole.
- janto 2y ago
  If anything, it's an issue with a magnet's naming. My understanding is that the North pole/direction got its name first.
scotty79 2y ago
> rods I think the origin might be phallic. Rod obviously gains positive charge when rubbed, for a man from 300 years ago.
deleted 2y ago
[deleted]
mandeepj 2y ago
> If you read Teaching Introductory Physics the author very clearly points out that there is no way of knowing the direction of the charge The author is wrong and you also. If people don't know about things then I'd rather have them stay quiet and learn about them rather than spreading misinformation. DC Current flow: https://energyeducation.ca/encyclopedia/Direct_current#:~:text=Direct%20current%20is%20defined%20by,positive%20terminal%20of%20the%20battery https://energyeducation.ca/encyclopedia/Direct_current#:~:te.... AC Current flows both ways: https://energyeducation.ca/encyclopedia/Alternating_current https://energyeducation.ca/encyclopedia/Alternating_current

akira2501 2y ago

It really seems like had a rationale: "We suppose as aforesaid, That Electrical Fire is a common Element, of which every one of the three Persons abovementioned has his equal Share before any Operation is begun with the Tube. A who stands on Wax, and rubs the Tube, collects the Electrical Fire from himself into the Glass; and his Communication with the common Stock being cut off by the Wax, his Body is not again immediately supply’d. B, who stands upon Wax likewise, passing his Knuckle along near the Tube, receives the Fire which was collected by the Glass from A; and his Communication with the common Stock being likewise cutt off, he retains the additional Quantity received. to C, standing on the Floor, both appear to be electrised; for he having only the middle Quantity of Electrical Fire receives a Spark on approaching B, who has an over-quantity, but gives one to A, who has an under-quantity. If A and B touch each other, the Spark between them is stronger, because the Difference between them is greater. After such Touch, there is no Spark between either of them and C; because the Electrical Fire in all is reduced to the original Equality. If they touch while Electrising, the Equality is never destroyed, the Fire only circulating. Hence have arisen some new Terms among us. We say B (and other Bodies alike circumstanced) are electrised positively; A negatively: Or rather B is electrised plus and A minus. And we daily in our Experiments electrise Bodies plus or minus as we think proper. These Terms we may use till your Philosophers give us better. To electrise plus or minus, no more needs to be known than this; that the Parts of the Tube or Sphere, that are rub’d, do, in the Instant of the Friction, attract the Electrical Fire, and therefore take it from the Thing rubbing: the same Parts immediately, as the Friction upon them ceases, are disposed to give the Fire they have received, to any Body that has less. Thus you may circulate it, as Mr. Watson has shewn; You may also accumulate or subtract it upon, or from any Body, as you connect it with the Rubber or with the Receiver; the Communication with the common Stock being cut off." from Benjamin Franklin's letter to Peter Collison, May 25, 1747.

throwway120385 2y ago
But his choice of "positive" or "negative" are entirely a convention of how he wanted to think about things. There's nothing special about the sign other than it made it easier for him to reason about what was happening.
wycy 2y ago
It’s really strange reading the words of such an intelligent person beginning to understand something back then that is so fundamental today that even laypeople understand it more scientifically. Really weird, but really cool to get a peek back into a scientific mind in the 1700s.
- jstanley 2y ago
  > even laypeople understand it more scientifically Laypeople use more scientific-sounding words, sure, but what more scientific way is there to understand something than to have discovered it yourself through experiment?
  - utensil4778 2y ago
    Experimentation brings knowledge, not understanding. Franklin did not understand electricity, but merely observed it. It wasn't until we discovered the electron proper and Maxwell did his work that we-- anyone-- understood electricity. Understanding comes from scientific and academic rigor after the discovery.
    - OJFord 2y ago
      Or just separately from, like Higgs understanding and theorising a boson years before it was actually 'discovered'/detected experimentally.
    - neuralRiot 2y ago
      > It wasn't until we discovered the electron proper I’d even say that we don’t yet fully understand the electron!

pdonis 2y ago

> there is no way of knowing the direction of the charge But there is--otherwise we wouldn't know that Franklin got it backwards. He thought the charge carriers were going one way, and chose the convention he did because he thought it matched the way the charge carriers were going, but it turns out they were going the other way. The signs of the charges are a convention--and the fact that we still use Franklin's convention and it works just fine attests to that--but the direction the charge carriers move is not.

2muchcoffeeman 2y ago
How would you have known this at first from rubbing rods and playing with static electricity?
- pdonis 2y ago
  I didn't say we can know it just from rubbing rods and playing with static electricity. The post I was responding to said there is no way of knowing it, period. Which is clearly false since we do know it now.
dotnet00 2y ago
I think they don't mean it in the literal "you physically can't tell the direction of charge at all" sense. As you say, the very fact that we know the real direction counters that. They mean that within the abstract context of electronics presented in introductory physics, the real direction of charge doesn't matter and cannot be determined. As long as you pick one consistent convention and stick to it, the math will always work out the same, since depending on convention, all the directions and signs are equally flipped. The real direction of charge only matters when you get deep into the details (eg semiconductors). At the level of detail of introductory physics, it's effectively a symmetry, similar to how given the simultaneous flipping of charge, parity and time, you cannot tell the difference.
- im3w1l 2y ago
  I think there might be a difference. From our experience with air we know that blowing and sucking are not quite the same. Blown air has a much greater capacity for direction than sucked air. I would assume that this is because the when we blow we add additional molecules and we get to decide the inertia of those molecules, but when we suck we take away molecules and they have the inertia they have. I would suspect that the same goes for electrons. An electron gun would (as used in old CRT monitors), would be a very striking example of this - I doubt we could make an electron-hole gun (though shooting positive ions could work, but that's not quite the same thing) - but it may be possible to observe in more normal conditions too?

deleted 2y ago

[deleted]

tzs 2y ago

Suppose that they had realized back then that electricity was going to become one of the most important technologies humans have in the future and decided that they should make a major effort to figure out the direction of the charge so future generations wouldn't get stuck with the wrong convention. All the top scientists, engineers, inventors, and crackpots in the world try to come up with some way to tell. Was there some method reasonably within their reach that would have worked? I'd guess the first thing they would try is weight. The body gaining the charge carriers should gain weight and the body supplying charge carriers should lose weight. That would probably fail because the mass of electrons is very low, and I don't think they had anything that could resolve weights that small. (I'm not even sure we have anything now that can do it). The second approach might again use weight, but with the realizing we don't have to measure what the weight is, just whether it has increased or decreased. So take two weights that are as identical as you can make them and put them on a balance. Seal the balance in an airtight container to prevent random air currents from disturbing it (or pump out the air--the vacuum pump was invented around 100 years earlier), and put it someplace very cold and with very little temperature variation, and adjust the masses until the balance shows no apparent movement for months. Then charge one of the masses and see if the balance can still remain apparently still for months. If it can't, and consistently goes out of balances toward the charged side conclude that side probably has the charge carriers. If it consistently goes toward the other side conclude that the charged side gave up charge carriers. I think that this too would probably fail. The mass difference is too small and isolating the balance sufficiently from outside disturbances is probably too difficult. Could they produce a stream of charges in a vacuum? Let's say they can. Considering the material they had to work with if those were negative they would probably be electrons and if they were positive they would probably be atoms or molecules with a missing electron. They would probably quickly discover that streams of charge in a vacuum are deflected when they bring a magnet near them and figure out that lighter charged things deflect more. They would then discover that all the negative charge streams they produce have carriers of the same mass, but the positive charge stream carries have different masses depending on how they are produced and they all have mass much greater than that of the negative carriers. I think they might lead them to conclude that the negative charge carriers are the fundamental ones.

deleted 2y ago

jonny_eh 2y ago

In a way he was right, if he was describing the movement of "holes", or the lack of an electron.

hn_throwaway_99 2y ago
This is exactly why I think he was wrong. Normally, pretty much everywhere else we use the terms, "positive" denotes the presence or addition of something, while "negative" denotes the absence or subtraction. So while I agree with the GP's comment that Franklin didn't know anything about electrons, so he arbitrarily picked one as negative and the other as positive, now that we do know about the movement of electrons, it kinda sucks because I think Franklin just "picked wrong". I.e. it would make much more sense to me if the absence of electrons (i.e. holes) were negative by convention and an abundance of electrons were denoted as positive.
- throwway120385 2y ago
  This is pretty much spot on. It sucks after 250 years of hindsight, but I would encourage anyone who wants to think like Franklin to buy an amber rod, a glass rod, a piece of real fur, and a piece of silk, and try experimenting with them and see if you can intuit from physical experiment what the fire is made of and how it passes from one material to another. You can't without the benefit of future knowledge. This is what it feels like to stand on the shoulders of giants.
  - hammock 2y ago
    What is an amber rod?
    - mindcrime 2y ago
      Just what it sounds like: a rod made of amber[1]. [1]: https://en.wikipedia.org/wiki/Amber https://en.wikipedia.org/wiki/Amber
- mensetmanusman 2y ago

throw0101d 2y ago

> Numbers and numeric quantities aren't a real thing that exists in the world. They exist only in our minds. Is math invented or discovered? * https://www.sfu.ca/~rpyke/cafe/livio.pdf https://www.sfu.ca/~rpyke/cafe/livio.pdf See also "The Unreasonable Effectiveness of Mathematics in the Natural Sciences" by Wigner: * https://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness_of_Mathematics_in_the_Natural_Sciences https://en.wikipedia.org/wiki/The_Unreasonable_Effectiveness...

lazide 2y ago
Was ‘Blue’ invented or discovered? Fundamentally, it’s the same type of problem - and really more of a philosophical thing.
- gavmor 2y ago
  We're using the term "Blue" ambiguously. The term was invented; its assignment and scope were invented, too. The wavelengths themselves were discovered. So there are two different "Blues;" signifier and signified.
- gavmor 2y ago
  We're using the term "Blue" ambiguously. The term was invented; its assignment and scope were invented, too. The wavelengths themselves were discovered. So there are two different "blues;" sigmifier, and signified.
- crote 2y ago
  The interesting part is that perception is shaped by language. The Ancient Greeks did not have a word for blue, which led to things like the sky being described as "wine-colored" or "bronze". Similarly, the English "blue" is split into two in Russian: light blue (голубой – goluboy) and deep/dark blue (синий – siniy), a speaker has to choose between them when describing something. The wavelengths may have always existed but colors only become a thing when we draw the arbitrary lines between them.
  - labster 2y ago

mensetmanusman 2y ago

“Numbers and numeric quantities aren't a real thing that exists in the world.” How did your mind gain access to this universal truth? ;)

philipov 2y ago

> We could just as easily have called it "black" or "white" charge And when we found a charge system that had 3 charges rather than just two, we did.

lynndotpy 2y ago
Where can I learn more on this? Searching yields nothing.
- tekno45 2y ago
  https://youtu.be/AOtUo25GB3c?list=TLPQMjEwNjIwMjQajcfSE5215w https://youtu.be/AOtUo25GB3c?list=TLPQMjEwNjIwMjQajcfSE5215w Kinda
- warhorse10_9 2y ago
  Read up on “color charge.”
- frutiger 2y ago
  Quarks and gluons, or quantum chromodynamics
- bradboimler 2y ago
  I imagine they're referring to https://en.m.wikipedia.org/wiki/Quantum_chromodynamics https://en.m.wikipedia.org/wiki/Quantum_chromodynamics
mr_mitm 2y ago
It's either six vs two, or three vs one, depending on what you mean by charge. The quarks and gluons can be red, blue, green, antired, antiblue, or antigreen.
- philipov 2y ago
  I was hoping someone would catch that ;)

adrian_b 2y ago

The reason why which charge is named positive and which is named negative does not matter is because in all the equations that relate electric charge with other measurable physical quantities we never have an electric charge alone, but we always have the product of two electric charges. The value of the product of two electric charges is invariant to the convention chosen for the sign of the electric charge. Numbers and numeric quantities are actually a real thing that exists in the world. They do not exist only in our minds (and in the minds of many other animals who are also able to count until some small number). And so does the concept of negation, which clearly is a property of the world, independent of humans or animals. For other physical quantities, the sign of a quantity is not arbitrary, like for the electric charge, because those are used in expressions that are not invariant to sign changes.

lupire 2y ago
Numbers do not exist in the world. Umbers exist outside the world.
- adrian_b 2y ago
  I do not know if this is a joke about shadows that I did not get, or just a typo, but numbers exist in the world. The world is composed of things. The things are grouped in sets. Numbers are equivalence classes of sets. The set of the medium-sized planets of the Solar System is equivalent in number with the set of the big planets of the Solar System and also equivalent in number with the set of the big satellites of Jupiter (i.e. 4). Such equivalences between sets of things exist regardless if there are any sentient beings that recognize those equivalences and there are circumstances when for instance the evolution in time of some sets of things is determined or influenced by the relationship between the numbers of things that compose each set.
  - juliushuijnk 2y ago
    > The things are grouped in sets. By who?

kabouseng 2y ago

Similar reason why the earth north pole is actually a magnetic south pole :) It was decided by convention / definition. For those whom it isn't clear what I mean. Compass magnet's north poles point north, which is only possible if the earth's north pole is magnetically a south pole.

janto 2y ago
If anything, it's an issue with a magnet's naming. My understanding is that the North pole/direction got its name first.

scotty79 2y ago

> rods I think the origin might be phallic. Rod obviously gains positive charge when rubbed, for a man from 300 years ago.

deleted 2y ago

[deleted]

mandeepj 2y ago

> If you read Teaching Introductory Physics the author very clearly points out that there is no way of knowing the direction of the charge The author is wrong and you also. If people don't know about things then I'd rather have them stay quiet and learn about them rather than spreading misinformation. DC Current flow: https://energyeducation.ca/encyclopedia/Direct_current#:~:text=Direct%20current%20is%20defined%20by,positive%20terminal%20of%20the%20battery https://energyeducation.ca/encyclopedia/Direct_current#:~:te.... AC Current flows both ways: https://energyeducation.ca/encyclopedia/Alternating_current https://energyeducation.ca/encyclopedia/Alternating_current