The h Bar

barrycarter

19:00

@Obliv They are the entirety... what do you think is missing?

@JohnRennie trig > geometry

That's the 2 word summary.

John Rennie

@manshu I feel like you're feeding me tiny snippets of the question then expecting me to provide insightful answers :-)

barrycarter

@JohnRennie Hey, I do that too

John Rennie

@barrycarter Really, I hadn't noticed :-)

skill patrol

arithmetic > trig

Obliv

@barrycarter it doesn't form the partition of the entire set $\mathbb{Z}$ right? they said they will call the set of the equivalence classes under this equivalence relation $\mathbb{Z}/n\mathbb{Z}$.

manshu

19:01

barrycarter

@skillpatrol Well, trig depends on arithmetic...

manshu

That was the question

barrycarter

@Obliv OK, so what element of Z do you feel is not included?

manshu

And I think that we should consider rotational energy.

Obliv

like say $n$ is 10. There would exist equivalence classes for 0-9

barrycarter

19:02

@manshu It appears to have an answer.

Obliv

wait..

barrycarter

@Obliv Yes, equivalence classes

Obliv

makes sense lol..

manshu

@barrycarter yeah.

but I am not convinced

John Rennie

@manshu it seems clear to me that no rotation is involved. Why did you think rotation might be an issue?

barrycarter

19:03

@manshu That mass looks like it was intentionally chosen not to rotate.

@manshu Now if it where spherical, maybe.

manshu

It's because the mass is revolving with the center as the center of hemisphere

John Rennie

Actually I suppose if it's a cube it will rotate by 90 degrees during it's trip to the bottom of the bowl.

barrycarter

@JohnRennie that's just orientation though

Iota

Hi

barrycarter

@Iota Greetings, Greek letter person

John Rennie

19:05

@manshu right, but the cube is not rotating about its own axis, so it's angular kinetic energy is zero.

Iota

I wanted to know, why are book/resource reference questions closed so quickly on this site?

barrycarter

@manshu In this case, I think they want you to regard the mass as a point mass.

@Iota It's too much a matter of opinion.

Iota

There are many great people here, who know their stuff, who also know from where they learnt it.

barrycarter

@Iota Yes, but this site is more for questions that have specific answers.

John Rennie

@Iota see:

18

Q: Are resource recommendations allowed?

What is the policy on asking for recommendations of books or resources on Physics Stack Exchange? What is a resource recommendation question? What sort of resource recommendation questions are allowed here? How should I answer a resource recommendation question? As a community member, how shoul...

Iota

19:06

Yes, it's opinion based, but it's quite valuable as well

barrycarter

@Iota EG, "what's the capital of Bolivia" as opposed to "where's a good place to build a summer home"

@Iota Try quora.com

ACuriousMind

Newer thread:

12

Q: Book recommendations: On-topic, on-topic but community wiki, or off-topic?

Yes, we've had this debate before. Unfortunately, there's no definite consensus to be found about their community wiki status: Good list, bad list (from July 2013) has the top voted answer (with a meager +11/-2) saying that book recommendation questions need to be actively moderated by the comm...

discussion policy books

Resource recommendation questions are not off-topic, I'm not sure why you say they are "closed so quickly"

Iota

@barrycarter Quora is bit low on the amount of actually talented people it has

compared to SE

barrycarter

My interpretation of the stackexchange guiding protocol: if someone asks "is there a book that talks about X", you can answer it, but "what's the best book about X", you can't.

ACuriousMind

What gets closed are vague requests where it isn't clear what the asker is actually looking for.

John Rennie

19:07

@Iota that's certainly true. For all its faults the Physics SE is an unparalleled resource.

2

barrycarter

@Iota I'm trying to bring the average down here.. I'm actually not sure that's true though. Quora has famous physicists hanging out.

@JohnRennie Cough cough cough. I respectfully disagree.

Iota

Sometimes, the request may look like, I have so and so background in the subject, I want to learn it fully, may be a person, who was in a similar position in the past could help. Instead of closing, shouldn't we just mark it down as protected

barrycarter

SE overall is a great resource, but Physics isn't really. Most of the help I've gotten is here, in this chat room.

John Rennie

@barrycarter in what sense. What did I say that you disagree with?

barrycarter

@JohnRennie I've mentioned it before: too many questions closed, too much desire to appeal to high end physicists.

Iota

19:09

@barrycarter It's not just the intelligence of the person who answers. It's also the intelligence of the person who asks the question, that matters.

By intelligence, you could mean previous knowledge about the subject etc.

barrycarter

@Iota Yes, to a point, but I don't think SE should be a site purely for professional physicists. Amateurs should ask questions too

John Rennie

All I demand of the OP is that they have thought about what they want to ask, done the obvious research on it (Google/Wikipedia) and have taken the trouble to write their question clearly.

Iota

Those are entertained here, to a reasonable extent

barrycarter

Physics is unusual in how badly it discourages student physicists.

manshu

@barrycarter I just asked :p

John Rennie

19:11

I have answered some really basic questions quite happily where the OP has complied with these simple requirements.

John Duffield

@barrycarter : I agree that too many questions are closed, but I don't think it's due to a desire to appeal to high-end physicists.

barrycarter

@JohnRennie But technically, you were breaking site policy, no? The other part of the policy says something about concept?

@JohnDuffield You think it's just the inherent bitterness physicists feel in realizing that physics is nothing more than mathematics?

John Rennie

@barrycarter no I don't think so. All my answers are conceptual in that I try to explain principles that can be applied to lots of problems.

barrycarter

@JohnRennie I remember a comment thread where I said we can answer questions if you show your work, but someone else said homework questions also had to have something else.

@JohnRennie I got into an argument about whether the "and" in the policy meant "and" or "or".

John Rennie

The trouble is that there is a homework gradient.

If someone just types in the questions from their worksheet i think few of us would object to closing the question.

barrycarter

19:14

Agreed, provided we gave them a link to other sites that might help.

Some people might say posting the worksheet is a first step in what the OP hopes becomes a dialogue.

John Rennie

@barrycarter dialogue

Iota

I'd really like if the book recommendation policy is toned down slightly. Sometimes, advice from great people regarding a resource greatly helps. It saves the time, and also assigns certain credibility to the resource. Imagine from the perspective of a person, who is stuck on a concept, for a lot of time because of referring to books, that don't discuss it thoroughly. Some resource recommendation could really help in that scenario, where you can't explain it in an answer.

John Rennie

This site is not designed for discussions.

In fact it is expressly designed to disafvour discussions.

barrycarter

@JohnRennie I know, but maybe the OP doesn't. That's why sites like openstudy.com exist (and this chat in some sense)

John Rennie

The chat is for discussions.

@barrycarter ignorance of the law is no defence

barrycarter

19:15

@JohnRennie Yes, but on many other SE sites, people sometimes give hints to the answer (as one would in a dialogue)

@JohnRennie Actually, it virtually always is.

Mens rea

Mens rea (/ˈmɛnz ˈriːə/; Latin for "guilty mind") in criminal law, is viewed as one of the necessary elements of some crimes. The standard common law test of criminal liability is usually expressed in the Latin phrase, actus reus non facit reum nisi mens sit rea, which means "the act is not culpable unless the mind is guilty". Thus, in jurisdictions with due process, there must be an actus reus, or "guilty act", accompanied by some level of mens rea to constitute the crime with which the defendant is charged (see the technical requirement of concurrence). As a general rule, criminal liability does...

John Rennie

I have been known to give hints in comments

Iota

For example, I've learnt certain things from certain notes from MIT OCW. Like coefficient of restitution, I found it after a lot of googling and none of the general phyiscs books seem to spend any time upon it. I'd really like to recommend that link to someone if they need it.

barrycarter

@JohnRennie Right. That's my point. a hint is sort of a first step of a dialogue.

ACuriousMind

@barrycarter We're not responsible for what other SE sites do.

John Rennie

@barrycarter I don't see that

barrycarter

19:17

@ACuriousMind What an attitude! Maybe not, but surely they represent the SE community in general?

ACuriousMind

And saying that mens rea implies that ignorance of the law is a defence misunderstands mens rea completely

barrycarter

@JohnRennie "using your hint, I found x and y, but am still stuck on..."

John Duffield

@barrycarter : no. I think it's because people who suffer from a strange mixture of intellectual arrogance and ignorance like throwing their weight around instead of contributing usefully to the site.

barrycarter

@ACuriousMind I obviously disagree, what do you mean?

John Rennie

@barrycarter at that point I'd say switch to chat

barrycarter

19:18

@JohnDuffield I can't disagree with that, unfortunately.

@JohnRennie Well, OK, but between timezones and stuff, not everyone is commenting at the same time.

This site is fairly arrogant, and that's coming from a mathematician.

Iota

Lol

skill patrol

try MathOverflow

John Rennie

There are physics forums for discussion and there have been since the early days of the Internet. The SE is not a forum and that's by design. Take it or leave it.

barrycarter

@skillpatrol Fair point, but that's not Mathematics

mathoverflow.net is explicitly for professional mathematicans

ACuriousMind

@barrycarter mens rea is the principle that certain acts require the will to commit them in order for them to be an offence. For instance, murder (instead of manslaughter) requires premeditation and the intent to kill. The absense of mens rea that makes what might be murder to manslaughter is not the lack of knowledge that killing is prohibited, but the lack of prior intent to commit the act.

barrycarter

19:21

@ACuriousMind I disagree with you there. If you break the law because you are truly ignorant (not just faking ignorance) that you were doing something wrong, you have a mens rea defense.

@JohnRennie My point is that it's really inconsistent with the overall theme of SE in general. There should be some consistency between the sites.

John Rennie

@barrycarter See:

78

Q: Is Stack Overflow a forum?

I was under the impression that Stack Overflow was a forum, or a forum-like object. And if it is not a forum: Why isn't it? What defines a forum?

discussion forum

This dates from the days before Stack Overflow evolved into the Stack Exchange

barrycarter

@JohnRennie OK, but isn't giving someone a hint making it a forum?

dmckee

@barrycarter Not in US jurisdictions. Sometimes the court will take ignorance in to account in setting sentence, but ignorance of the law is not a defense unless you can show that there was no way for you to have known (secret law or the like).

barrycarter

@ACuriousMind en.wikipedia.org/wiki/…

The general rule under common law is that "ignorance of the law or a mistake of law is no defense to criminal prosecution."[17][18] In some cases, courts have held if knowledge of a law, or the intent to break a law, is a material element of an offense a defendant may use ignorance as a defense to willfulness if his misunderstanding is in good faith:

ACuriousMind

@barrycarter Read the section on "Ignorance of the law and mens rea" in the article you linked. Ignorance of the law is only a mens rea defense if the law requires you to know it in order to break it. For instance I cannot have intent to not pay my taxes if I don't know I should be paying taxes.

barrycarter

19:24

@dmckee It's an affirmative defense, meaning you have to prove ignorance, but it's a defense.

John Rennie

@barrycarter yes, and I probably shouldn't give hints even in comments. However my better nature sometimes gets the upper hand.

barrycarter

a defendant may use ignorance as a defense to willfulness if his misunderstanding is in good faith

John Rennie

I probably wouldn't make a good supervillain

2

ACuriousMind

But in almost every case where an action is prohibited, ignorance that said action is prohibited is not a mens rea defense, since mens rea is the intent to commit the action, not the intent to commit a wrong action.

barrycarter

@JohnRennie So even you agree that the actual rules are bad.

John Rennie

19:25

The rules exist for a reason.

There is a near infinite number of lazy physics students out there

barrycarter

@ACuriousMind Read the sentence I quoted.

Iota

@dmckee Since, you're a moderator here. Can you voice an opinion to implement something like a super-protected question, that falls in a category that if you have more than 1000 rep in that topic, you could answer, and make the resource recommendation questions fall in that category, if they aren't duplicates, and show a fair deal of hardwork done by the OP.

barrycarter

@JohnRennie So you break rules that you believe exist for a good reason? Have you considered running for politics?

John Rennie

and once they cotton on to the fact we will do their homework we would be inundated with do my homework questions.

ACuriousMind

@barrycarter Quote the conditional before it, please: "if knowledge of a law, or the intent to break a law, is a material element of an offense [...]"

barrycarter

19:27

@JohnRennie I think they're just looking for help (some of them), not always full answers.

ACuriousMind

The very sentence you quote says what I say, if you only read it in its entirety

dmckee

@Iota You'd need to appeal to the Stack Exchange authorities to create such a class of questions. But I doubt they'd go for it. Low barrier to entry is one of the design goals of Stack Exchange.

barrycarter

@ACuriousMind I'm quoting the second sentence of the Ignorance.. section.

John Rennie

Providing any help for homework questions encourages the asking of homework questions

barrycarter

@ACuriousMind You're quoting something different.

ACuriousMind

19:28

@barrycarter Yes. In full, it is: " In some cases, courts have held if knowledge of a law, or the intent to break a law, is a material element of an offense a defendant may use ignorance as a defense to willfulness if his misunderstanding is in good faith:"

dmckee

@JohnRennie I'm afraid you seem cut of superhero cloth. But at least that means you can get Edna Mode to do your suit. As long as it has no cape.

ACuriousMind

You quoted the second part of this

barrycarter

@ACuriousMind No, I quoted an entire sentence, do another search for it.

@JohnRennie But you admit you already do that, right?

John Rennie

@dmckee for the record, while I loved the film it's utterly wrong about the capes. Capes are cool!!! I want a cape :-)

barrycarter

In some cases, courts have held if knowledge of a law, or the intent to break a law, is a material element of an offense a defendant may use ignorance as a defense to willfulness if his misunderstanding is in good faith:

The proliferation of statutes and regulations has sometimes made it difficult for the average citizen to know and comprehend the extent of the duties and obligations imposed by the tax laws. . . . [T]he Court almost 60 years ago interpreted the statutory term "willfully" as used in federal criminal tax statutes as carving out an exception to the traditional rule."[19]

ACuriousMind

19:30

@barrycarter Are you kidding me? What you quoted appears exactly once in the entire article, and it is in that sentence.

barrycarter

@ACuriousMind You don't see that in the article?

ACuriousMind

What? I see it, I quoted that very thing

I'm not sure what the problem here is. You quoted only the "a defendant may use ignorance as a defense to willfulness if his misunderstanding is in good faith:"

And then I pointed out you left out the conditional before it

barrycarter

@ACuriousMind OK, you're right you did. I thought I quoted the whole thing earlier.

@ACuriousMind But I don't think the conditional changes the meaning.

John Duffield

@barrycarter : I don't mind if John Rennie votes to close a question. The guy writes a lot of answers. But there's others who don't. You know the sort of people. They like pulling the wings off flies.

barrycarter

@JohnDuffield Yes, I think Physics has deviated from the general standard set by other stack sites.

ACuriousMind

19:32

@barrycarter It's not saying that you can always use ignorance as a defense - only when the knowledge of or intent to break the law is part of the offence.

John Rennie

Gosh it's getting late (for me - I start work at six a.m.)

dmckee

@barrycarter The thing is that the courts sometime make exceptions to a basic rule that has been around since British Common law, and they set a high standard to apply it.

barrycarter

@ACuriousMind yes, a material part of the offense, not a statutory part.

ACuriousMind

You don't get away with offenses where the act regardless of intent is punished, not matter how ignorant you are

barrycarter

@dmckee I'm talking about true ignorance, not feigned ignorance.

dmckee

19:34

Not only must you have good faith, but you ignorance must be reasonable for a educated person who tries to obey the law.

John Rennie

I'm going to call it a night. At least I think BC finally understands relativistic acceleration. I will work on converting him to the joys of differential geometry.

barrycarter

@ACuriousMind Give me an example where a reasonable person would commit an illegal act, be ignorant of it, and still be guilty?

@dmckee Yes, in other words, true ignorance.

@JohnRennie Niters.

skill patrol

@JohnRennie cya later :-)

dmckee

@barrycarter Not just true ignorance, but ignorance that the court believes the average man has as well.

John Duffield

@barrycarter : I'm beginning to think physics has deviated from the general standard set by other sciences.

dmckee

19:36

That applies to the inner workings of tax law and other complicated administrative stuff, but not in general.

barrycarter

@dmckee To me, that is true ignorance.

@dmckee OK, like I said, give me an example of where an average person would ignorantly do something illegal and be guilty of it?

@JohnDuffield I'm not willing to condemn all physicists over this one site. For other reasons, perhaps ;)

dmckee

@barrycarter Fail to file your taxes because you believed someone who said there was no legal requirement to do so.

People have gone to jail over that.

It doesn't matter how sincere you are in that belief it the court finds it to be unreasonable.

barrycarter

@dmckee I did say a reasonable person, remember.

Slereah

Oh wait

ACuriousMind

@barrycarter Disobey a rare street sign because they have forgotten what it means?

Slereah

19:39

Hm

In perturbation theory

barrycarter

@dmckee Generally, the people who have gone to jail over that are aware that the person who told them that is at odds with the government.

dmckee

Jaywalking because they're from a small town where it is legal.

Slereah

The in and out states are defined at $\pm \infty$

barrycarter

@ACuriousMind No, but what about a missing street sign?

Slereah

But can we still talk about measurements in between

ACuriousMind

19:39

@barrycarter What?

barrycarter

@dmckee And there is no signage indicating otherwise?

dmckee

@barrycarter Chicago has jaywalking law and very few signs. They can still cite you for it.

barrycarter

@ACuriousMind No reasonable person would misunderstand a street sign. However, suppose there's a rule that applies but no street sign.

@dmckee And someone who is truly ignorant has been cited and not just warned?

If a sign says "no parking Tuesdays and Thursdays", and you park there Wednesday, but it turns out, for entirely different reasons, parking is always prohibited there, I'd say you've got a good mens rea defense.

For all its faults, the government does a pretty good job of making people aware of the law, at least the important ones.

dmckee

@barrycarter Ever been down to the law library and look at the code books?

The Federal code takes up more than a meter of shelf space.

barrycarter

@dmckee No, although I've tried to browse the Code of Federal Regulations before.

@dmckee You can do that online now you know :)

dmckee

19:44

Most state codes are roughly as long.

barrycarter

@dmckee Yes, but my whole point is that there is a lot of signage, paperwork, and bureaucracy that will make you non-ignorant.

dmckee

The point is that you haven't a clue about most of the laws to which you can be help liable and they mostly won't excuse you for that.

barrycarter

I disagree. I agree there are too many laws, but many of them are very specific to an industry or a situation where you are unlikely to be ignorant.

John Duffield

@barrycarter : sorry, me neither. There's a lot of good physicists out there. The problem seems to be with "theoretical physicists". It's like they've lost touch with reality and they're getting in the way of scientific progress.

dmckee

@barrycarter No there isn't. Try reading your state laws on weapons. You'll discover that you've committed felonies many times without noticing.

barrycarter

19:46

@dmckee Explain that, please?

Slereah

After all in the Heisenberg formalism, the state doesn't vary

So that state will be the same everywhere

barrycarter

@dmckee Every store has a huge sign indicating you can't bring a gun in.

dmckee

And if the police had happened to take you into custody one of those days you'd have been in serious trouble.

barrycarter

@dmckee Once again, example please.

ACuriousMind

@barrycarter Okay, this has somehow gotten out of hand. In the cases you're proposing, you have a mens rea defense because the violation of parking prescriptions requires you to be aware of the parking prescription. It's just wrong that "in general" ignorance of the law can exonerate you. That's not what mens rea does. It's about the intent to commit the offence, and many offences are built such that knowing they are an offence is necessary to commit them.

dmckee

19:47

@barrycarter It's not the gun they'll get you for. It's the innoculous item that will be treated as a weapon.

barrycarter

@ACuriousMind If you don't know something's illegal, you can't have an intent to commit ANY offense.

John Duffield

Innoculous.

barrycarter

@dmckee Once again, an example please?

John Duffield

The hypodermic syringe!

dmckee

@barrycarter Every carried a steak knife in a basket or other container to a cookout. That's probably a felony in your state. Certainly is in Virginia, Alabama and Texas.

barrycarter

19:49

The Post Office has huge signs telling you what you can't ship precisely for the reason we assume people won't know such things.

dmckee

The police might choose to overlook it, but if they report it to the DA and he has time on his hands he can make that a concealed weapon offense.

barrycarter

@dmckee Letting aside the fact it would be hard to get a jury conviction, do you have any case law or arrests on this?

@dmckee I just read the Texas law.

ACuriousMind

@barrycarter Okay, rephrase: It's about the intent to commit the action that is prohibited, regardless of whether or not you are aware that it is prohibited. In the case of parking laws, the action that is prohibited is "ignoring parking restrictions", so you can't commit that action if you don't know them - you cannot ignore what you are not aware of. But in the case of e.g. defamation, the action is possible whether or not you know that what you just said crosses the line to defamation.

barrycarter

A person commits an offense if the person intentionally, knowingly, or recklessly carries on
or about his or her person a handgun, illegal knife, or club if the person is not:

@ACuriousMind Right, but I said early on that you don't think you're doing anything wrong. If you're trying to skirt the edge of the law, that's not mens rea.

@dmckee I'm sure you can find some horror stories, but what I've seen is that there is a lot of work done to make sure people aren't ignorant of the law.

So, if a reasonable person is ignorant of a law, that's when there's a problem.

Remember, an affirmative defense doesn't have to appear in the body of the law, and it doesn't even mean you won't get arrested. It just means that you can use it as a defense at your trial.

ACuriousMind

@barrycarter Who says you're trying to skirt the edge of the law? Perhaps you honestly think that the defamatory things you're saying are factually true - but that won't make you less guilty if they're not.

barrycarter

19:54

@ACuriousMind Actually, I'm pretty sure they will.

@ACuriousMind Plus you get into the whole "reasonable reliance" issue.

If you observe someone robbing a bank, report it, and it turns out you'd actually witnessed some street art, no one would hold you liable for filing a false report.

ACuriousMind

@barrycarter Well, let me quote at you from the very Wikipedia paragraph you cited: It starts with "The general rule under common law is that "ignorance of the law or a mistake of law is no defense to criminal prosecution."" and also includes "Not all offenses require specific intent, and a misreading, even in good faith, may not excuse the criminal conduct"

If mens rea worked as you say, both of these statements would be utterly false

skill patrol

:-)

ACuriousMind

Which may well be, but then you can't use the middle part of that paragraph to support your view either

skill patrol

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barrycarter

@ACuriousMind I would say those statements actually aren't true, at least not in the USA. And the key word there is "MAY not excuse". Do you have something stronger than WP -- eg, case law?

@ACuriousMind OK, I guess I'm saying that I don't live in fear of violating an obscure law I don't know about, and I don't think any reasonable person does either AND I think they are correct in their beliefs.

Admittedly, you get cases like Bowers v Hardwick, but those are the exceptions.

ACuriousMind

19:59

@barrycarter I'm a physicist, not a lawyer!

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