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.
"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.
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.
> 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?
Along similar lines, I recently learned about an early nuclear physics textbook written by George Gamow. The first edition came out in 1931, and the preface of the second edition in 1937 describes how the book had to be completely written because the state of knowledge had changed so radically in those few years -- most notably, by the discovery of the neutron and of induced radioactivity.
It's fun to think about a time when this stuff that we now take for granted as basic physics was not just new and poorly understood, but the forefront of knowledge was advancing so rapidly.
I haven't been able to find an online copy of the 1931 edition, but the 1937 edition is called Structure of Atomic Nuclei and Nuclear Transformations, and it's available through the Internet Archive: https://archive.org/details/in.ernet.dli.2015.501245
Is that official? In spanish, decades ago, the word for battery was "Pila"
"Pila" is a heap of countable physical units, either stacked or disordered. But pila is commonly a fixture for liquids, like septic tank is pila séptica
And batteries were mostly lead-acid. Hence, a pile for/of acid.
The main way that inductors function is by storing energy in a magnetic field, exactly analogous to the way capacitors store energy in an electric field.
If you apply a constant current to a capacitor, the voltage across the capacitor will increase linearly as the capacitor stores energy in the electric field.
If you apply a constant voltage to an inductor, the current through the inductor will increase linearly as the inductor stores energy in the magnetic field.
Perhaps part of why the intuition can break down is that in real life, inductors tend to be much "leakier" energy storage devices than capacitors. If you store some energy in an inductor and then change the voltage across it to zero (practically: short its terminals together), in theory a perfect inductor will maintain a constant current forever and the energy stored does not change. In practice inductors (with an exception for things like superconducting magnets) are made from wire that has a resistance, and so the current in a real shorted inductor will eventually decay to zero. This means that in practical terms inductors are mostly only useful for short term energy storage. On the other hand, real-life insulating materials (like air, vacuum, or Teflon) can can be pretty close to perfect insulators allowing real capacitors to store energy more or less indefinitely... certainly on timescales of years.
Seems like capacitors, inductors and batteries differ only quantitively in their response curves, not in qualitatively? As in they all do different things to the circuit on the voltage, amperage and time axis? We would need separate words for them, but accumulators seems like a decent umbrella.
Indeed! I love reading Benjamin Franklin for exaclty that. If you haven't read it, Walter Isaacson's biography on Franklin is absolutely fascinating. Brilliant, hilarious, driven, and wildly accomplished. The dude was (IMHO) one of the most interesting humans to have ever lived. Highly recommend.
This was how the 18th Century worked. In the 19th Century mathematical language became rigorous and formal, better able to handle more complex constructions accurately, but harder for lay people to learn, as it became a new language.
Well... going by the Fermi biography and the first few chapters of The Idea Factory (about Bell Labs) I would think this is what it always sounds like in the early stages of humans discovering a new part of nature.
It's just that our most recent theories have been so rich that we have happened to discover many things theoretically before we find them in real life. (Theory has preceded practice in recent decades, rather than the other way around which is historically more common.) I'm not sure this will always be so, it might be a temporary leap.
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.
>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.
Sounds like he leaves it open for future "Philosophers" to update the convention as our understanding of the phenomena that he had documented improved. Smart guy in not assuming that he got it right the first time. Franklin sounds like he wasn't a "my way or the highway" type of guy.
Hmm. "We rub our Tubes with Buck Skin", he says in the same letter. I was trying to work out whether the tube gets a positive or negative charge. I think it depends on what material is being rubbed with what:
I had ChatGPT-4o translate this to contemporary english
> We assume, as stated earlier, that electrical fire is a common element, equally shared among the three mentioned individuals before any operation with the tube begins. Person A, who stands on wax and rubs the tube, transfers the electrical fire from his body into the glass tube. Since his connection to the common stock is cut off by the wax, his body is not immediately replenished. Person B, also standing on wax, passes his knuckle near the tube and receives the electrical fire collected by the glass from A. B’s connection to the common stock is also cut off, so he retains the additional amount received. To person C, who is standing on the floor, both A and B appear electrified. C, having the normal amount of electrical fire, gets a spark when approaching B, who has an excess, and gives a spark to A, who has a deficit. If A and B touch, the spark between them is stronger because the difference in their electrical fire is greater. After they touch, there is no spark between either of them and C, as the electrical fire in all three is equalized. If they touch while being electrified, the equality is maintained, and the fire circulates continuously.
> This has led to new terms. We say B and similar bodies are positively electrified, and A is negatively electrified; or rather, B is electrified plus, and A minus. In our experiments, we electrify bodies as plus or minus as needed. These terms are used until philosophers provide better ones. To electrify plus or minus, it’s essential to know that the parts of the tube or sphere being rubbed attract the electrical fire from the rubbing object during friction. Once friction stops, these parts are ready to give the received fire to any body with less. Thus, the fire can be circulated, as Mr. Watson demonstrated, or accumulated or subtracted from any body, depending on the connection with the rubber or receiver, while cutting off communication with the common stock.
There's no rationale, merely a decision. He chose Earth as the source of electric fire, instead of a sink. It's a completely arbitrary choice, as light source vs dark sucker.
He could have thought instead that A is collecting Electric Fire from the glass rod. And when B touches the rod they recharge it losing some of their Electric Fire.
“These Terms we may use till your Philosophers give us better.”
Yes he had a rationale, the question is why it didn’t change once we knew better; he even called for it.
I mean, I think I know why it didn’t change at any given point - the standard was already in place and it always looks too difficult. But in retrospect, the effort in the 1800s would have been small compared to the effort 100 years later.
Maybe it’s still true that we should change the convention starting now, because the confusion and cost of not changing it in the future will continue to grow?
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.
It didn't matter in Franklin's time, but it came to matter later, due to the discovery or invention of devices in which it matters which charge carrier is moving.
For example, in naming the parts of a NPN bipolar junction transistor, the negatively connected terminal is the "emitter", and the positive one the "collector". The base-emitter diode arrow points toward the emitter.
It helps me visually when looking at a circuit diagram if I can think about the current flowing "down", like most rivers do in the Northern Hemisphere. It's just a vague association in my mind, but it is based in physical reality.
That convention is the result of identifying current flow as being the movement of that which we identified as positive charge.
It's not a convention that like charges repel.
If we agree that current is the flow of positive charge, then it has to go away from positive, toward negative.
Using positive quantities for current and charge is a good thing; we aren't constantly dealing with negative numbers to measure common situations like how much current is flowing through a wire.
Negation, being a concept, exists only in the mind. Same with "things". A thing is a noun; a part of speech. The "real world" is undifferentiated quanta.
I have an hard time coming to terms with this platonic view of the mind, as if our minds where some kind of extradimensional aliens playing with this sandbox of "undifferentiated quanta" sometime called reality.
I understand how it make sense saying that the concept of spedrunning is completely absent in Ocarina Of Time and only exists in the player playing the game, but I do not see how this would be a good philosophy to apply to ourselves.
I confess that I have a particular aversion to this specific philosophy/POV because I feel like it is riding on the respectability and "coolness" of science to sound more serious while being just another metaphysics without (IMHO) any* particularly good qualities.
* Ok, I admit that it has at least a good quality: it is a good example of a non-religious metaphysics to give to people that cannot imagine a non-religious metaphysics.
Philosophies are tools for reasoning. I don't literally go through my life thinking "oh here's an undifferentiated quanta, time to apply some nouns to it." But if I want to adopt a scientific mindset it's beneficial to think in terms of the physical experience versus my mental model of it because I can write my mental model down, whereas I can't write physical experiences or undifferentiated quanta down. That's what makes them quanta.
We have tons of sayings for this like "the map is not the territory," "wherever you go that's where you are."
While in the mathematics of the later part of the 19th century and of the 20th century there have been developed many theories with very abstract concepts for which it may be claimed that those concepts have been invented in the minds of some mathematicians without a direct correspondence with the world experienced by them, such a claim would be false about almost any concept in the mathematics developed until the 19th century, because almost all older mathematical concepts are just abstractions of properties of the physical world.
For instance, what happens when you connect the two electrodes of a battery to the pins of a semiconductor diode will differ depending on whether you negate the battery or not (i.e. you revert or not its connections). What happens with a ball (or with a thrown stone) will differ depending on whether its velocity is positive or negative, and so on.
Additions and subtractions of physical quantities, therefore also negation, happen in the physical world regardless of the presence of sentient beings.
Humans can recognize such properties of the world and give them names and integrate them in coherent mathematical models, but the base concepts are not inventions, they are the result of empirical observations.
> What happens with a ball (or with a thrown stone) will differ depending on whether its velocity is positive or negative, and so on.
The velocity of a ball is a vector. Using a positive or negative number to describe it is a manner of convention. When you say that you threw a ball with “positive 7 mph” velocity, you need to explain what you mean.
One might argue that there really is a ball and that it has a velocity and that the velocity really is an element in a vector field originating [0] at the center of mass of the ball. Debating to what extent this is fundamentally true or is just a useful concept that people came up with would be interesting.
[0] In general relativity, space is not Euclidean (nor is it a flat Minkowski space), and velocity vectors are only really meaningful in association with a point in spacetime. You can read all about tangent bundles in Wikipedia :)
There is a way in that it matters: in a vacuum tube you can have cathodic rays but (pragmatically) not anodic rays.
IIRC a Veritasium video claims that these where essentially discovered by mistake in lightbulbs, so I suspect that Franklin would have had a hard time finding them...
But a cathode is that terminal of the device where positive current escapes!
It's only a "cathode ray" because it's reversed inside the tube: the terminal where positive current comes out of the device is where the negative current emanates internally to go to the other terminal.
An electron beam shooting out of a device is an anode ray.
If we make an oscillating circuit by hooking up an inductor and capacitor and set it in motion, the devices are constantly switching their terminal designations between anode and cathode with each zero crossing. The terms are completely useless, except when talking about vacuum tube circuits and such.
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.
If one take the position tha minds are not part of the "real world" then you end up defining "reality" by some random model.
It is just as absurd as saying that the only thing that exists is my own perception and you are "just" a ghost my mind is "thinking into existence".
It sounds less crazy only because we are used to reductionism being generally more useful, but what is the usefullness of concepts like reality and existence when defined to mean that we and our minds (the only thing we perceive) are not "real" or do not really "exist"?
Even before the appearance of life, the things group in sets spontaneously, due to the interplay between attractive and repulsive forces and the positive feedbacks that appear in certain conditions.
The world is not made of a homogeneous substance, but there are various kinds of groupings at various levels, nucleons and electrons group in atoms, atoms group in molecules, molecules group in pebbles, stars group in galaxies and so on.
> 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.
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.
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?
An electron gun produces a beam that contains only electrons; there is no conductor, and I think holes can exist only in the presence of a conductor. So you can't shoot a beam of holes through a vacuum. But if the material between the gun and the screen were a semiconductor, maybe you could draw pictures on the screen using a beam of holes? I mean, I don't see why a beam of holes can't be focused just like a beam of electrons.
> I mean, I don't see why a beam of holes can't be focused just like a beam of electrons.
Wouldn't electrons rush in to fill the holes from every direction, rather than just the intended one? That's what my intuition says anyway. So yeah, my guess would be that it is in fact not possible.
That blade cuts both ways; the electron beam in a CRT travels through a vacuum, there's nothing to "rush in". A hole beam would have to travel through a medium with no free electrons.
Nobody seems to have mentioned Holes. Holes are positive charge-carriers. Yeah - they're virtual, they're not like positrons or protons. But they behave just like electrons going "the other way".
My understanding is that a hole represents the absence of an electron. If an electron is removed (e.g. by rubbing), there's remains a physical object bearing a positive charge: the proton that was originally associated with that electron.
I haven't heard anyone talking about holes for years. Are they now deemed an outmoded concept?
[Edit: should have read further down the comments :-)]
The concept of holes is important, but it doesn't have much practical use. It typically only comes up when you're discussing the physics of how semiconductors work, or doing similar electron-level analysis of a component.
It's also usually brought up early on when teaching new students about circuit physics, but it's really not something that comes up in an EE's day to day.
Maybe it's more relevant if you're deep into analog or RF black magic, I wouldn't know.
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.
It means someone is paying attention. When introducing the topic, it's more effective to say that electricity has 2 charges while chromodynamics has 3, and let them discover that those numbers are using different units for "2" and "3" only after they decide to find out more.
Carefully qualifying every single statement causes people to stop listening, because they don't care. It's better to correct oneself after-the-fact. Make it a topic of discussion once people are hooked. Introducing a simple error for someone to unravel does that.
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.
Interestingly, this argument was weak before we ended up with truly elementary particles. Cause there’s no such thing as three apples or three people. They are unique objects with similarities defined by an observer, and then you go deeper and note that “object” is also a purely synthetic delineation. 3 is a model, not an element of reality. Even advanced maths define it as a set which contains nothing, 1 and 2 (which contains nothing and 1, which contains nothing and is preceded by nothing). Counting and measuring is equivalent to drawing lines — adding something that wasn’t there before.
The fact that particles have identity is also vague, afaiu, so existence of numbers or their non-biological origin is not as easy to prove by example as it seems.
> [sic]Cause there’s no such thing as three apples or three people.
I understand what you're saying. Occurrences like https://en.wikipedia.org/wiki/Ring_species demonstrate that the idea of "species" isn't firm and that what truly matters is each individual and their unique circumstances. But this seems to me to be more a limitation of language and philosophy than a repudiation of math.
As you pointed out, it's all equivalent to drawing tally lines, counting pebbles, sliding counters on an abacus, or counting fingers and toes. Despite the fractal nature of coastlines and the constant exchange of matter and energy between adjacent parts of the universe, it is possible to agree upon useful delineations. And there is not any alternative maths which happens to describe practical observations in a way which does not reduce to the maths with which we are familiar.
They are useful repeatedly because they derive from fundamental properties of the observable universe. We can imagine other sorts of universes - one with hyperbolic geometry as opposed to flat, for instance ( https://en.wikipedia.org/wiki/Shape_of_the_universe ). Parts of geometry would work differently there, and laws of motion as well. But interestingly, many fundamental rules of math would still apply. Just with different outcomes which are less useful for predicting results here.
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.
In English, speakers are forced to make the same light/dark distinction between pink/red and orange/brown as well. I don’t think most native speakers of English think of orange as the same as light brown.
You may be interested in https://blog.xkcd.com/2010/05/03/color-survey-results/ if not seen it yet. If you desaturate the main chart to around 70%, #8a3324 lands onto a red-brown-orange triangle. I think I agree with that someone, cause at 70% the whole orange region sort of bleaks away.
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.
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.
In semi-conductor design discussions around transistors and motion of electrons, it’s often much more convenient to talk about hole (bubble) migration than electron migration.
It’s really a moot point as to whether the abstraction used to solve problems matches with the physicalist interpretation of reality.
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.
If they even had a corpuscular theory of matter, they might have considered weight. But this was firmly back in the Enlightenment "Natural Philosophy" kind of thinking when materials were "imbued" with properties like gravity and levity or heat and cold. Some of the people working on these things also had a keen interest in alchemy and the search for a philosopher's stone.
Part of the problem we have in trying to put ourselves in their minds is that some or most of their reasoning is unrecognizable to us as "science." If you try reading EG Newton's Principia Mathematica it's laid out in prose from first principles using geometry and is essentially unrecognizable except with a strong education in Euclid.
Thermionic electron emission in a vacuum tube would let you distinguish between electron and element: the electrons are liberated much more easily then the source material and result in current flow through the circuit.
This lets you build diodes as a result, so assignment of electrical direction based on that phenomenon would get it correct.
EDIT: in fact with a cathode ray tube you can literally visualise charge direction from looking at a foil wheel being spun in a vacuum: https://m.youtube.com/watch?v=K2G6M3cYJZs
> 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.
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.