"Electric charge is a theoretical given . . ."

AmagicalFishy

Hi, folks. First, I'd like to say that although I plan to major in physics next semester, I know very little of it now. My lack of posts doesn't reflect how often I frequent this forum, though. While browsing a thread asking what "charge" is, I read this reply:
. . . to which people seemed to offer a negative reaction to. My assumption for the reason is that it's more on the philosophical side and less on the physical side, but could someone explain why this answer was looked down upon? It made sense to me, but that may be my ignorance nodding. Do we know what charge is, what causes it, etc., and not just its effects—or are they one in the same?

(And, if you don't mind, I'd like someone who didn't post the original quote to answer; that'd defeat the purpose. )

DragonPetter

I'm not going to go back into that thread, but I think the phrase "theoretical given" is a bit dangerous, because nothing in science is a "given" as if it were made up to set the groundwork for the theory. It takes credit away from the math and observations that confirm charge's existence. The explanation is in the math of the quantum state of particles, and all of the experimental evidence that supports it, it is not a given.

Also, the answer was rather speculative, contradictory, and obscuring. It was redirecting the question to other speculative topics while flat out contradicting others who have given more mainstream concrete answers. Speculation is fine and fun to talk about, but it has its place and when someone is trying to teach another what a concept is, they can get annoyed if their point is being obfuscated. We can be humble about our understanding of things and still give explanations from what we know without having to mystify it.

AmagicalFishy

I know the answer is speculative, but I guess I don't see where it's contradictory. I assumed "theoretical given" implies something like the following: Although we know precisely what constitutes charge, how it affects everything around it, and how it reacts—we don't know exactly what charge is, though it's a given that it exists." Does that make sense?

I very much understand the fault in giving a speculative point, and neglecting the copious amounts of surrounding knowledge, which does indirectly mystify the subject, so I guess my question is this:

Is the original quote incorrect? Do we know what charge is? If so, can someone explain it to me?

Drakkith

The problem with the post you quoted, is that by saying we don't know WHAT charge is, only it's effects, we are immediately giving up a fundamental view of what something is according to the scientific method and science. This is because asking WHAT something is happens to be meaningless without describing how it works and what it's effects are.

For example, if someone asks me what a cat is, I can tell them it is an animal with four legs and fur and is sitting in my lap right now. (Which he is...) "Well ok, that describes a cat, but WHAT is a cat?" Umm...a cat is a mammal, a member of the animal kingdom, which is a category of life. "But what IS a cat?" *Facepalm*

The ONLY way to define something, to say WHAT it is, is to describe it's effects and properties. The definition of Charge does exactly that. So ignoring that definition and asking "Well, what is charge REALLY?" is to immediately take a non-science view.

Now please don't take this as me saying that asking questions about something is wrong. There is absolutely nothing wrong with asking "Is there anything else that charge might be or that describes it's effects in a better way?". That is what science is all about. There are still plenty of unknowns in science and the only way to get answers is to ask questions!

Studiot

Don't let them get to you ...and you will go far young man, woman or piscean.



In mathematics we use the notion of 'Axioms'

These are statements or assertions made without proof.
The best a mathematician can do is to take a particular bunch of axioms and establish that their interaction does not lead to inconsistencies.

In physics ( and other sciences) we (should) actually operate the same process, although we do not call them axioms.
We use these fundamental statements to establish models of reality.

Within classical physics we need five fundamental quantities that are asserted not 'proved'
These are usually taken as Mass, Length, Time, Temperature, Charge.

But classical physics is not a complete model of reality. Other models (none are complete either) use different fundamental basics.

Whatever model we are using a most important matter, often forgotten or ignored, is to work within the limitations or conditions set out for that model and not to try to apply it blindly outside those conditions. There have been many spectacular misconceptions and arguments as a result of this error down the centuries.

go well

AmagicalFishy

Ah! Those answered my questions quite well. Thank you all.

DragonPetter

It is contradictory to what others post because the statement said charge is unexplained, while everyone else has given an explanation for charge. That is what I meant by contradictory. Its one thing to be contradictory with evidence/logic to support your argument, but its another just to throw out contradiction without any way to back it up.

Studiot

If everyone else knows exactly what charge is why can't I find said explanation on Google?

DragonPetter

I didn't say everyone knows exactly what it is in a zen-like enlightened aspect, I said the people of that thread were giving an explanation of what it is while he said there is no explanation.

I googled "What is charge" and found some pretty good explanations of what the concept is.

Drakkith

Maybe your view of "what something is" differs from others? If you do not view the answer to that question as an explanation of how it interacts with the universe, then science cannot offer you an answer.

Studiot

Yes maybe it does differ.

I do not sit around dreaming up quantum states and then look for experimental evidence to confirm my theory.

Rather I observe an effect and try to supply a theory to fit that effect or observation.

I have no knowlege of this other thread and there is no link to it here, but your responses seem to me to be rather hard on the OP, especially since in principle I agree with him.

DragonPetter

Well, that is how theory usually arises until they got to quantum physics and started predicting things in theory before observing them, but either way, don't you think theory to observation or observation to theory should be commutative and equally valid?

I don't think we're being hard on the OP at all. It wasn't he who said the original quote even, he was just curious why people responded negatively to the answer someone else gave.

If anything, we're being hard on the person who gave the original quote, but, even then, we're only hard on him in the context of the original thread, and what he actually said was not necessarily wrong and brings up good questions.

Drakkith

No one dreamed up quantum states and then looked for evidence afterwards. The creators of QM used lots of known math and known evidence as a stepping stone to figure out how QM works. Sure they had to come up with some new ideas, equations, and such, but that is because current math and ideas couldn't explain the anomolies. Their work had to explain existing experimental anomolies and it also predicted new things that no one had known before. In your words they "Observed an anomolous effect and attempted to supply a theory to fit the observations".

I challenge someone to give me a definition of ANYTHING that I cannot ask "But what is it REALLY" to.

Studiot

As I understand the OP's 'given', he means pretty much the same as as my use of the word axiom in post#5.

In any discipline we agree on a minimum set of axioms or givens and define everything else in terms of them.

So a complete explanation for everything beyond these givens can be provided and developed from them.

I think it an entirely reasonable question to ask if 'charge' is such a given or a derived quantity.

My answer is yes, at least in classical physics it is a given.

Further, charge and temperature have the property of being invariant under relativistic or quantum transformations, unlike the other three I mentioned in post#5.

No, the Ancient Greeks made that mistake.

AmagicalFishy

I think I understand what's going on; it seems to me a difference in perspective, which makes it look as if several viewpoints are at odds.

In the original quote you'll notice it was said, "We do know a great deal about its effects. Those effects are seen as patterns in changes of velocity. We know neither the origin of electric charge or of polarity." — It was stated that we do know a great deal about the patterns and effects of charge. I think Studiot makes a very good point; no one meant to imply we were ignorant in regards to charge, but that the existence of charge is an proven axiom of physics.

I admit that perhaps the only mistake was the way the original poster worded what he said, which did seem to mystify the subject more so than not—but I understand now what he meant by that.

So, back to the "difference in perspective": Would you agree that charge is a proven physical axiom of sorts? One that we know voluminous amounts about, but remains an axiom none the less?

DragonPetter

Your definition of given is different than mine. A given to me is something hypothetical that we take for granted and then use logic to derive conclusions/effects from it. Charge may have been hypothetical in the beginning, but it is not hypothetical anymore; it has been observed experimentally and validated mathematically. We may make new observations that cause us to modify our theory, but so far our explanation of charge matches what we observe, so I don't know how it can be considered a given.

The Ancient Greek's theories did not always match with observations, and so they became obsolete. What mistake did they make exactly? So far, the behavior predicted by quantum mechanics matches with observations and we modify as we find problems.

I'm just saying its a two-way street, and we don't have to observe everything before we can define something if logic and reason leads us to that definition before we observe it. We just need to observe something to prove the definition is a physical reality, which we have in the case of the definition of charge.

Consider if you were given Maxwell's equations in their most general form, and then you sat in a room for a few years and played around with the equations so long that you were able to derive Ohm's law, kirchoff's voltage law, and kirchoff's current law from them eventually without knowing or observing it beforehand. Even though you were only using maxwell's equations, would you call it dreaming up some impossibility by manipulating the equations until coming to those predictions, or is it possible that you would have used math and logic to predict physical reality, and it would turn out to be valid based on the assumptions you made? Maxwell's equations were a given in the example, but then you could observe that they are valid and do indeed result in the effects of the equations in the form of KVL,KCL, etc. Are maxwell's equations STILL a given, or have they graduated to a real explanation?

Drakkith

I agree completely. The issue is that the question being asked is NOT "is charge' such a given or a derived quantity?", the question keeps going back to "What is charge?", even after giving the definition, explaining why it is like that, etc.