The h Bar

Abcd

9:42 AM

@JohnRennie then why have they even kept the upvote comment option?

John Rennie

@Abcd I suspect there isn't a logical reason for this :-)

Abcd

@JohnRennie Okay :). But one thing I truly hate is that saying thank you is not allowed :(.(to the person who answers your question)

John Rennie

If you want to add a comment saying thank you I doubt anyone will care much :-)

We aren't supposed to do it, but I doubt the moderators spend their time searching for thank you comments to delete.

Abcd

true! but before I type thank you there's a rude warning "Avoid thank you".

Mithrandir24601

@Abcd You say that, but I still remember the first comment I got: "Wow. Nice. Welcome to SFF, and +1" from a mod

David Z

9:47 AM

@JohnRennie cc @Abcd Yeah, we've got better things to do with our time. Just don't be surprised if such comments get deleted after a while.

John Rennie

If someone posts a rude warning just ignore it.

Abcd

@Mithrandir24601 SFF?

@JohnRennie lol it's inbuilt. Don't you see the warning.

Mithrandir24601

@Abcd Sci-Fi and Fantasy

John Rennie

Science Fiction and Fantasy SE

Abcd

"Avoid +1, thanks etc." This is a warning message I get before typing any comment.

Mithrandir24601

9:48 AM

@JohnRennie doesn't see the warning and avoids it, the warning sees @JohnRennie and avoids him

John Rennie

@Abcd ignore it. Smash the system!! :-)

David Z

@Abcd I'd think about it like this: there are many rules which you can break from time to time without being disruptive, and thus the people in charge of enforcing those rules are not inclined to care about violations of them. The warning against "thank you"s is one of those rules.

If you do it a lot, though, then you might attract some unwanted attention.

Abcd

Ohkay.

ACuriousMind

10:04 AM

@Semiclassical Epistemology and philosophy of science - which is what I think you're talking about - are not usually thought of to be part of metaphysics.

ACuriousMind

10:38 AM

I typed "CSCO" into google and hoped for "complete set of commuting observables". I got the graph of the stock price of Cisco Inc., with google not even asking if I meant cisco or csco.

Anonymous

@ACuriousMind It seems CSCO is the abbreviation for Cisco. finance.yahoo.com/quote/CSCO

ACuriousMind

Why would I need to "abbreviate" a five-letter word by a four-letter word?

I mean, stock markets have sophisticated computers these days, can't they handle an identifier longer than four characters? :P

Anonymous

Ticker symbol

A ticker symbol or stock symbol is an abbreviation used to uniquely identify publicly traded shares of a particular stock on a particular stock market. A stock symbol may consist of letters, numbers or a combination of both. "Ticker symbol" refers to the symbols that were printed on the ticker tape of a ticker tape machine. == Interpreting the symbol == Stock symbols are unique identifiers assigned to each security traded on a particular market. For example, AAPL is for Apple Inc.; OODH is for Orion DHC, Inc.; and HD is for Home Depot, Inc. A stock symbol can consist of letters, numbers, ...

Anonymous

Historical reasons I guess :P

Anonymous

"Cisco (ticker symbol: CSCO)"

Anonymous

10:48 AM

By the way how could you even expect Google to turn up with "Complete Set of Computing Observables" for CSCO! :D It's not that intelligent yet

ACuriousMind

I guess I expected the wiki article to have that abbreviation as an alternative title, so google would show it

Maybe I just expect more of ~~other~~ AIs than is reasonable, though :P

Anonymous

Ah, I see your point. :) Heh

Secret

11:09 AM

Complete set of commuting observables

In quantum mechanics, a complete set of commuting observables (CSCO) is a set of commuting operators whose eigenvalues completely specify the state of a system. Since each pair of observables in the set commutes, the observables are all compatible so that the measurement of one observable has no effect on the result of measuring another observable in the set. It is therefore not necessary to specify the order in which the different observables are measured. Measurement of the complete set of observables constitutes a complete measurement, in the sense that it projects the quantum state of the system...

Ask and you shall receive

lılostafa

@JohnR What is a rigorous (in the physics sense, compared to chemistry) chemistry book that treats the covalent bonds quantum mechanically?

ACuriousMind

@Secret Do you really think I was unable to find the article on my own?

Secret

I don't know, cause I knew of simialr scenarios where the user is not sacratic or makeing a humour. another reason is probably I naturally match-make the first query I see as a weird type of humour

John Rennie

@lılostafa The undergrad books I was recommended were The Chemical Bond by Murrell, Kettle and Tedder and Molecular Quantum Mechanics by Atkins. I don't know if these are still in print.

Secret

to be fair, I think :P implies a joking statement, so I made a response which I expect to be joking but may not be to most people

ACuriousMind

11:16 AM

@Secret Where's the joke in your response?

Secret

I forgot to put that ":P" sorry about that

Anonymous

Lol

ACuriousMind

...what?

Putting ":P" at the end of sentences that contain no humor doesn't magically make them contain humor

Secret

but at least it informs readers that I am not being serious

John Rennie

@lılostafa The Atkins is still in print. I guess molecular bonds haven't changed much in the last forty years :-)

amazon.co.uk/Molecular-Quantum-Mechanics-Peter-Atkins/dp/…

lılostafa

11:19 AM

@ACuriousMind I don't agree with this. It contradicts your statement here too:

Jul 17 at 16:18, by ACuriousMind

@Mostafa You'll note that either there's a clear indication it's a joke (like ';)' or ';P') or the people talking to each other have a rather long rapport with one another. Obviously 0celo7 didn't think you were joking at all, and nothing in your message indicates that you are. If you want to make jokes, maybe you should try to make them a little more obvious

John Rennie

@ACuriousMind smile. Breathe deeply. Think happy thoughts (in my case that would be food)

Secret

"insert pics of a bowl of salad"

Anonymous

@ACuriousMind Secret means that he posted that Wikipedia article as if you wouldn't be able to find it yourself. That in itself is the joke. Well, it is weird humor. :P :p :d

lılostafa

@JohnRennie Yeah, thanks, found it. I was just about to give the link here :)

ACuriousMind

@lılostafa No, it doesn't contradict it. If you think it does, you're commiting the fallacy of affirming the consequent.

Anonymous

11:21 AM

':d' I suppose means "trying to lick my nose"

4

ACuriousMind

@Blue lol

Secret

Actually, on a more serious note, does the phase "Ask and you shall receive" commonly used in jokes?

I knew I heard that in movies and TV shows invovling waiters but I am not sure the full scope

ACuriousMind

@JohnRennie Now I'm hungry. Thanks for that ;P

lılostafa

@Blue That's a healthy thing to eat.

John Rennie

@ACuriousMind I'll post a picture of my latest meal if you want. That should rapidly suppress any appetite you might have :-)

ACuriousMind

11:23 AM

@lılostafa Wikipedia's choice of image on point as always, I see.

Secret

lılostafa: eww

ACuriousMind

@JohnRennie Dear god, was it something British?

John Rennie

@lılostafa I find myself, for the first time in many years, tempted to flag a post :-)

Anonymous

@lılostafa I was an expert in that

John Rennie

@ACuriousMind actually I haven't eaten yet. In fact I'm about to shower then cycle off in search of food. Possibly some form of beefburger though my mind isn't made up yet.

lılostafa

11:27 AM

@Blue Great. From the article:

"That being said, mucophagy could improve the immune system of those who practice it. According to the hygiene hypothesis, the recent increase in auto-immune diseases and allergies could be because of lower exposure to pathogens during early life and into adulthood. An effective way to transfer germs from the outside world into the body is through mucophagy, and some scientists postulate that the germs in mucus are weakened and therefore train the immune system without causing disease."

Do it folks.

ACuriousMind

@JohnRennie How's that supposed to make me less hungry?

John Rennie

@ACuriousMind Mental image of me showering?

2

ACuriousMind

Urgh, I didn't even think to think of that! Thanks, that worked.

Secret

I am not going to eat a JohnRennie thanks :P

John Rennie

With that I think I'll quit for lunch. I do hope I don't return to find myself suspended again :-)

Secret

11:33 AM

hi skullpatrol long time no see

2

user685252

11:51 AM

hi pal

Abcd

@user685252 Are you skullpatrol?

@user685252 why did you create a new account?

user55789

Hi all, could anyone elaborate on a small General Relativity question for me? According to Carroll it is "straightforward to show"

user84215

Hi

Anonymous

@user55789 Look at the top right of your screen "Don't ask about asking, just ask."

Abcd

@user685252 what's wrong dude?

@Blue Can I ask here? (about hinge reaction)

Anonymous

11:57 AM

@Abcd You can ask, but I'm a bit busy at the moment

Abcd

hello! Could anyone help me understand certain aspects of hinge reaction force?

I drew a diagram above^.

It's given that hinge reactions are equal from both hinges.

So now, their vertical components should be equal and should should add up to $Mg$.

But what I can't understand is how to sketch their horizontal components.

Sir Cumference

Nucular

"Nucular" is a commonly used metathetic form of the word "nuclear". While no dictionaries list this particular pronunciation as correct, several make mention of it because of its increased usage. == Notes in dictionaries == Merriam-Webster Dictionary receives enough questions about their mention of this mispronunciation in the dictionary that it is one of two mispronunciations which receive particular mention in their FAQ: Though disapproved of by many, pronunciations ending in \-kyə-lər\ have been found in widespread use among educated speakers, including scientists, lawyers, professors...

ACuriousMind

Not sure whether I find it funny or sad when a new user calls me "sir" in a comment given my current profile picture. Perhaps a bit of both.

2

Anonymous

@Abcd Search "hinged door physics" on YouTube. There are some good videos

Secret

Nucular Weapon

Semiclassical

12:07 PM

The colloquium speaker accidentally called me olf yesterday in the course of answering the question I asked

ACuriousMind

@Semiclassical They called you a unit for measuring stinkiness? oO

Semiclassical

My question was regarding undergraduate vs grad students, so it made sense in context

Abcd

@Blue Seen galaxy physics' video already....

Semiclassical

Tsk. She. :p

heather

@ACuriousMind plenty of people have called me "sir" - i thought my username was fairly obviously female.

ah, well.

Anonymous

12:10 PM

@Abcd So what's the problem you're facing?

Anonymous

@heather Well it's definitely not obviously for the eastern part of the world

Abcd

@Blue Can't understand the horizontal components of hinge force and their the torques due to them..

ACuriousMind

@heather Only obviously female to people from a culture where "heather" is a common name at all, I guess. (as an example how such things can vary, 'Andrea' is parsed as female in Germany, but as male in Italian) But it still shows the same default assumption.

Semiclassical

@ACuriousMind Given how long ive been in grad school...yes?

Stickiness sounds like a pretty good label for that

Anonymous

@Abcd The direction of horizontal components are already shown in the video

Abcd

12:12 PM

@Blue I didn't get why he chose those directions.

ACuriousMind

@Semiclassical Not stickiness, stinkiness - the olf is a unit for strength of smell

Anonymous

@Abcd Easy. Find a door or window near you. Break the top hinge and observe the motion of the window. Then fix the top hinge and break the bottom hinge and then observe the motion of the door or window again. The hinge forces prevent such motions. So you can easily guess the directions of hinge forces. (Try imagining it at least :P)

Semiclassical

Ohh. I’m on my phone and didn’t notice I’d written olf not old

That makes more sense

ACuriousMind

Oh, lol

This confused conversation makes a little bit more sense now :D

Semiclassical

Olf would work as a metric for some students, though

ACuriousMind

12:17 PM

"How long have you been working on this problem?" - "Oh, about 10 Olf"

Abcd

@Blue Okay, if I remove upper hinge the door will move in clockwise direction about the lower hinge?

Anonymous

@Abcd Right

Abcd

@Blue So what can I say about the direction of the horizontal force of upper hinge?

I wonder why skullpatrol creates new accounts...The "long time no see" message has been starred too lol.

Anonymous

@Abcd You say

Anonymous

It should be camman sansa

user55789

12:23 PM

Abcd

@Blue No. Please give a hint.

user55789

So in "Spacetime and Geometry" by Carroll, the author gives the first statement and the last

The above computation is what I came up with between the two, but I'm not sure whether the contraction (in red) is an allowed operation

The reason for my doubt is that I have a repeated index (lambda) over which I already sum

peterh

@EmilioPisanty I've tought a little bit about the moderation. I agree that the opinion of the more worthy contributors (=professionals) should be handled with higher weight in the site.

user55789

Am I simply allowed to left contract with a metric of my choice here?

ACuriousMind

@user55789 Yes, but you're not allowed to use an idex that's already being contracted for it.

Anonymous

12:25 PM

@Abcd Well, horizontal component of upper hinge force should prevent that clockwise rotation. So, it has to act towards left in your diagram.

ACuriousMind

I.e. you should simply choose any other index than $\lambda$.

user55789

@ACuriousMind So what I just did (outlined in red) is illegal?

ACuriousMind

Yep

peterh

@EmilioPisanty But, there were many active, professional contributors, with a more inclusionist view as the current moderation practive, and most of them aren't between us any more.

@EmilioPisanty The question is, how to handle this.

user55789

@ACuriousMind In that case, any hints on how to get from the first step to the last? :P

ACuriousMind

12:27 PM

@peterh Name three, and provide evidence they left because of their "inclusionism" and not other differences with site policy or simply unrelated personal reasons.

Secret

@pZombie To address that, we need to think about philosophically what happens when two different worldviews are allowed to interact with each other. Is there an objective reality, or is everything subjective and each of us individuals are living in our own subjective realities and our friends are just porjections of our minds

Abcd

@Blue Okay, how can torque provided by both hinge reactions be clockwise? He takes both negative in the answer.

ACuriousMind

@user55789 Contract with $g_{\alpha \mu}$ instead?

Anonymous

@Abcd Hmm, torque provided both the hinges is indeed in same direction. Try finding it about COM.

user55789

@ACuriousMind Ah I'm stupid.. I can just do \alpha -> \mu and \mu -> \rho and get the result

Thanks..

Sigh..

peterh

12:35 PM

@ACuriousMind Talking about it is problematic, because I don't want to re-raise old fights, particularly if I wasn't part of them and don't know all circumstances. I am thinking further.

ACuriousMind

Don't beat yourself up - index computations are annoying ;)

Secret

Had we were $n^m$ dimensional creatures, we won't need to be in index hell for tensors

because we could have just laid out whatever physical object we use to represent a tensor, and do the whole thing geometrically

ACuriousMind

@peterh Well, but how am I supposed to evaluate your claim, then? I can't come up with a single user off the top of my head who I'd say primarily left for reasons related to "inclusionism", rather than our stance on rudeness, suspensions, or non-mainstream physics. If there is a significant number of experts who do not visit this site because we disallow homework questions, or vague and unclear questions, then that would undercut my main reason for supporting these policies

And it is good you don't want to re-raise old fights - I'm not asking you to. If you are so certain these users left for the reasons you say, then they have to simply have stated that somewhere in an unambiguous manner, otherwise you shouldn't be certain of it.

@MathematicsAminPhysics No user from this room has shown up there last week, so you have no reason to assume anyone here is interested in this. Please consider us as opting out from being notified further of these courses of yours.

user84215

@ACuriousMind How do you claim that "No user from this room has shown up there last week"? Maybe some users visited those courses during last week.

lılostafa

12:51 PM

@ACuriousMind If you know no one showed up, then you're wrong. It's self-contradictory ;)

Abcd

@ACuriousMind If I am unable to use right hand rule easily because obtuse angle is there, is it allowed to turn the notebook and then use it? Will it yield the same result?

ACuriousMind

@MathematicsAminPhysics None of them has posted anything in the room. Okay, maybe they looked at it, but clearly, no one participated.

Anonymous

ACM bombarded with pings

user84215

@lılostafa Interesting point

ACuriousMind

@lılostafa lol (you're technically correct, the best and worst kind of correct)

@Abcd I'm afraid I don't understand the problem - between what is there an obtuse angle, and how would that impede the right hand rule?

Abcd

12:53 PM

@ACuriousMind Here's an example. blue is $\vec{r}$ and red is $\vec{F}$

I have to find $\vec{r}\times \vec{F}$

user84215

@ACuriousMind It is not necessary that people should post messages in those rooms to show that they are interested in the courses.

Abcd

How do I use right hand rule there? I am just unable to place my right hand properly on the $\vec{r}$

ACuriousMind

@MathematicsAminPhysics It's not necessary for people to leave any sort of evidence of their interest to be interested? How do you determine whether people are interested at all, then?

lılostafa

@ACuriousMind I was actually waiting for you to refer me to another logical fallacy

Abcd

However if I tilt the notebook I get the thumb in upward direction = +ve

ACuriousMind

12:57 PM

@Abcd You don't need to mimick the obtuse angle with your hand - your two fingers just need to be in the same plane and order as the two vectors, i.e. you can treat this as if the angle was a right angle - all the right hand rule gives you is the direction of the cross product, and the direction does not depend on the angle

lılostafa

@peterh We clearly need a New PSE Order here.

ACuriousMind

@lılostafa I tried, but since the chat transcript does not record who was present at a time, you're actually correct :)

Abcd

Oh, in my book it's written "place the right hand on the first vector and then curl the fingers into the second vector". That's what I always tried

lılostafa

@peterh The first step is getting one of the goodfellas elected as a mod. AFT is the obvious choice.

user84215

@ACuriousMind You may read many articles on the Wikipedia while you may not post any article there. This means that you are not interested in the Wikipedia?

Secret

1:00 PM

0

Q: Spaceship engine - particle accelerator

Let's say you build a strong particle accelerator in space. One that can accelerate particles to near the speed of light. Can you use such an accelerator as a spaceship engine just by shooting out particles in a steady stream for a long time? How much time will it take for such a spacecraft to re...

Now that's rocket science

ACuriousMind

@MathematicsAminPhysics All this seems to go back to that you don't actually ever define what your courses are supposed to be. Usually, a "course" implies some sort of participation from all sites (like asking questions or handing in homework). Wikipedia is an encylopedia, of course the reader of an encylopedia leaves no sign of having read it!

3

That is, given the ordinary notion of "course", your "courses" have a grand total of one participant, namely you. If you want to pretend there's more, you're just kidding yourself.

Secret

businessinsider.com/…

The above is something I might ping vzn on. (still deciding whether to @ )

But here's what I think:

ACuriousMind

@Abcd That's a weird way of phrasing the right hand rule and I'm not sure I even understand what it's supposed to mean. The right hand rule to me is "Put your thumb along the first vector and the index finger along the second vector. Extend your middle finger, that is the direction of the cross product"

Secret

I recall that in an issue of NewScientist that one major issue of AI is not whether they will take over our world, but whether they are competent in carrying out their task and we are able to understand how it works within

user84215

@ACuriousMind As I said in the instruction of my rooms, the nature of these course is self-study. If participants have any problems or questions, they can post them in the rooms. Please first read the instruction.

Secret

1:07 PM

I guess with things like AlphaGoZero and AutoML, it seems us humans being the gatekeepers we need to be better at understanding how an AI perceive the world

ACuriousMind

@MathematicsAminPhysics Your instructions say: "and the participants discuss them here till the next week". Given that all you do in the room is post materials, not discuss them, it appears actually the number of participants is zero.

Secret

Luckily there's a panel event on 11/11/2017 on AI I might be able to raise this topic to the speakers

user84215

@ACuriousMind Even in the first days of physical schools and universities students are usually reluctant to participate in their courses.

Anonymous

What? Are you talking about playschools and nursery?

lılostafa

@ACuriousMind Wow I've never used the right-hand rule that way! I always bend all my fingers inward instead of using the middle finger.

But if you prefer it that way, be careful as it can turn into an insulting hand gesture if you accidentally change the role of the index and the middle finger ;)

@MathematicsAminPhysics I think it's actually the exact opposite.

ACuriousMind

1:13 PM

@MathematicsAminPhysics Yeah, alright, I'm done with this conversation. Continue your "courses" however you like, but don't expect me to leave your misleading advertisments for courses with no participants here.

→ 2 messages moved to Trash

user84215

@ACuriousMind Why have you moved them to the Trash?

ACuriousMind

@MathematicsAminPhysics Because they are misleading advertisements. What you offer is no course, it has no teacher, no participants, and presently simply consists of materials from a book (posted with questionable obeisance of copyright, I might add!) that someone wanting to self-study could also read on it their own.

lılostafa

@MathematicsAminPhysics Why are you insisting on this math/physics courses idea? The chat is not a good platform for online courses. Also, people are mostly here to ask/answer questions. For online courses, they go to Coursera, edx, etc..

user84215

@ACuriousMind What? Violating copyright? Can you show me?

bolbteppa

There are plenty of online group study things, e.g. reddit.com/r/dgatp

user84215

1:22 PM

@ACuriousMind So many math professors violate copyright since their lecture notes are very similar to math textbooks.

lılostafa

@ACuriousMind But I think they should be free to do it here, even if (others think) they're wasting their time.

Anonymous

I guess it's fine to conduct informal courses when you have a few willing participants. But first of all it is important to develop a good relation with the participants and other chat users. No one will trust a random low rep user who claims to conduct courses in chat rooms created by them. Spamming other rooms with (click-bait) advertisement and annoying all the mods is not the way to go.

user84215

I have to go.

ACuriousMind

@lılostafa They're free to inform people about what goes on in their chatrooms, but not in such a misleading manner.

0celo7

@ACuriousMind obeisance?

ACuriousMind

1:26 PM

@0celo7 I guess that's not the right noun for "obey"?

Ah, it's indeed apparently not quite the meaning I intended. Oh well

Secret

@ACuriousMind @Abcd perhaps the book is referring to the right hand grip rule/curl rule in electromagnetism?

ACuriousMind

@Secret Abcd said explicitly this is about finding the cross product of two vectors.

0celo7

I find this situation hilarious

Abcd

@Secret cross product of two vectors. The same wordings have been written in two books.

@ACuriousMind Please guide me through application of right hand rule in above case.

Secret

Actually, one can use the grip rule to do cross product. In my uni, we were taught to rest our hands horizontally on the first vector, (e.g. F) then curl your fingers towards the direction of the second vector (e.g. r) and then your thum will point up (out of screen) and that's the cross product (e.g. torque)

But usually in electromagnetism, the right hand rule is the flemming's right hand rule mentioned by Acuriousmind

Abcd

1:32 PM

I think grip rule = right hand rule according to my books.

Secret

Like so:

so the curling direction is the order you should cross product the vectors

Anonymous

Just use this...what's the problem

Secret

That works too

Abcd

@Blue I am unable to apply it to above problem.

Anonymous

1:34 PM

@Abcd Turn your right hand upside down.

Abcd

Index finger in r direction. Middle in F's direction. But it seems impossible to orient the fingers that way.

Anonymous

Say, your index finger is $r$

Anonymous

And middle finger is $F$

Abcd

@Blue Is clockwise the right answer?

Wrichik Basu

@dmckee need your help: can you visit here: chat.stackexchange.com/rooms/67358/…

Anonymous

1:35 PM

Then $r\times F$ is given by the thumb.

Abcd

@Blue downward right?

Anonymous

(After you turn your right hand upside down)

Anonymous

@Abcd Yes

Abcd

Physicists should come up with a better method to find the direction of cross product. :p

What about the disabled people?

They can't use right hand rule...

Anonymous

Just set up a coordinate system....

Anonymous

1:36 PM

i,j,k

Anonymous

i*j=k and so on

0celo7

@Secret looool

@Abcd what?

@Abcd use your mind

Secret

yeah, I misremebered the formula of torque, it should be r x F not F x r

Anonymous

@0celo7 That ^

Semiclassical

I think it helps to think of your coordinates as x1,x2,x3

Secret

1:38 PM

in such case that curly drawing will point down, consistent with Blue's

Abcd

yeah...

Semiclassical

then the cross products amount to e1 x e2 = e3, e2 x e3 = e1, e3 x e1 = e2

(writing e_k as the unit vector along the positive x_k axis)

lılostafa

Is there a right-hand rule for this?

Secret

@lılostafa well for starters, you need to be able to visualize a 7 dimensional object.

Semiclassical

so in that case the cross product just comes down to whether the indices are an even permutation or an odd permutation

Secret

1:40 PM

and 4 is my limit

I like to remeber semiclassical's as 123,231,312

Semiclassical

right

Secret

just keep pushing the string to the left as if it is a loop

Semiclassical

and really you just need 123. the rest are either cyclic permutations or reflections thereof

e.g. 213 is a cyclic permutation of 321 which is the reversal of 123

Abcd

but there can certainly be a better method, I hope one will be discovered someday....

0celo7

Permutations are where I figured out algebra wasn't for me

Semiclassical

1:42 PM

i think we've had time to figure out whether there's a better method

0celo7

For physics it was renormalization, for algebra it was permutations, for literature it was poetry.

Semiclassical

and the right-hand rule is, for most purposes, entirely sufficient

0celo7

Nothing like that for analysis thus far!

Semiclassical

I think for me it was field extensions in algebra? Not sure.

0celo7

But tbh I don't enjoy analysis, I just go crazy if I don't see some norms in a 24 hour period.

lılostafa

1:43 PM

@Secret OK, imagine a 7D human. Can he have a right-hand rule for both a 7d and 3d cross product? If yes, how?

Semiclassical

But I'll assent to renormalization stuff being one of the reasons I didn't want to continue doing field theory.

Secret

@lılostafa Technically yes, because odd dimensions you can have a well defined axis

Semiclassical

that and field theory is really bloody confusing

@0celo7 on that note, did you ever track down the sign issue in your literature review?

Secret

and the 7D right hand will be basically some 5D subspace with a +ve orientation, and the left hand will have a -ve orientation

0celo7

@Semiclassical I quite enjoy classical field theory. I just wish there were a good math-oriented reference. All of the books either have QFT in mind or some awful bundle mess.

Secret

1:45 PM

and you cannot flip between the two orientations with any 7D rotations if I recall...

0celo7

@Semiclassical I was doing hw until 0:30 last night. I'll take a look this afternoon

Semiclassical

QFT is weird in that it's hard to explain what's really going on

if you approach it from the physics side, there's a ton you have to learn as prereq just to get the right standpoint

and if you approach it from the math side, it's not even clear what QFT actually is

0celo7

that's why GR is the best physics for mathematicians

Semiclassical

lol

0celo7

Very well defined, uses deep ideas from geometry and analysis

Semiclassical

1:46 PM

and entirely useless in the real world :P

0celo7

GPS (maybe)

Semiclassical

Yeah, I'm still not clear on whether GPS needs GR or not

0celo7

I wonder if I could write Garmin and ask

Someone there has to know.

Semiclassical

seems like, yeah

0celo7

Or are all the GPS satellites run by the gov't?

Semiclassical

1:49 PM

by contrast, QM---for all its weirdness---has been exceedingly successful as a useful physical theory

i'm not so sure about how to rank field theory. on the one hand QED, QCD, electroweak theory, etc

on the other i'm not sure how much impact that has had on actual technology?

Slereah

Laser has arrived

I'm ready to take the world hostage

It's a tiny ass laser

lılostafa

@Slereah power?

Slereah

Yes, I have the power

pZombie

mount it on a shark

0celo7

@Semiclassical to be fair QM is a close second. Lots of juicy math there

One can even prove -- completely rigorously -- that hydrogen doesn't implode

Slereah

1:51 PM

are we sure it doesn't

0celo7

@Slereah it's unlikely by the anthropic principle

Semiclassical

ugh, anthropic principle

haaate

0celo7

@Semiclassical I think such questions are banned on PSE

Doubting the QFT overlord is Not Nice

Slereah

Jesus it is pretty bright

Even just watching the dot on the wall

i'd better get some laser goggles

0celo7

Also some insane people think that predicting the magnetic moment of the electron is an application

Slereah

1:52 PM

My eyes feel weird already

Also there's no on off button

Semiclassical

well, it's an experiment. in that regard, it's certainly an application

Slereah

I might want to rig one up

0celo7

@Slereah pic?

Semiclassical

but relevance to technology...i dunno

0celo7

I got some Amazon money for my birthday. MTW time?

Semiclassical

1:54 PM

i'll admit, whenever I have access to a laser---even just a simple pointer---my first temptation is always to shine it on a slit :)

0celo7

@Semiclassical oh cmon

What's wrong with it

Semiclassical

depends on which version we mean

Anonymous

@0celo7 It's one of the reasons I stopped reading pop science

Slereah

The wiring seems to be pretty poor

lılostafa

@Slereah I meant the laser power (in Watts) :)

Slereah

1:55 PM

If I bend the cable a little it turns off

but that's what you get with a cheap chinese laser I guess

Secret

To be fair, no QM then no lasers and transitors and stuff

Semiclassical

as an example of the anthropic principle I can respect, there's the classic story about Hoyle

Slereah

It also doesn't seem very well collimated

pZombie

your keyboard is missing a row

Slereah

That's a CPC keyboard

Semiclassical

1:57 PM

"[Hoyle] is said to have reasoned from the prevalence on Earth of life forms whose chemistry was based on carbon-12 atoms, that there must be an undiscovered resonance in the carbon-12 nucleus facilitating its synthesis in stellar interiors via the triple-alpha process. He then calculated the energy of this undiscovered resonance to be 7.6 million electronvolts. Willie Fowler's research group soon found this resonance, and its measured energy was close to Hoyle's prediction."

An anthropic explanation for why our eyes see light in the visible spectrum also seems entirely reasonable.

Where I draw the line with anthropics is when it goes from conclusions about testable phenomena to metaphysical principles

Anonymous

@Semiclassical Yeah, it is a principle which I can agree to, but it sort of feels depressing to agree to it. :P

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