The h Bar

Mew

1:00 PM

here is my new theory:

user228700

It started to rain and I needed to take the clothes off the clothesline.

user228700

@JohnRennie Yeah.

user228700

@JohnRennie Yes, yes.

Mew

@heather, (1) Happiness is having the CONFIDENCE that you can overcome forseeable obstacles/threats (2) Pleasure is overcoming obstacles/threats

Human motivation is therefore to increase confidence of being able to overcome a survival threat/obstacle

Secret

ok, ignore what I said "maxwell equation break down". however the magnetic components DO double in 4 +1 D

19

Q: Maxwell in multiple dimensions: What happens to curl?

I read this answer a while ago, and while thinking about $\nabla$, I realized something. Since the cross product can be written as a determinant, in higher dimensions we require extra vector inputs. IIRC it's called the "wedge product" in higher dimensions. Alright, how does this work when we ge...

heather

1:01 PM

@Mew, hmm, that's...intriguing

John Rennie

@Kaumudi OK. If you calculate the pressure difference just due to the liquids in the tube in middle it is $\rho_1 g 40 - \rho g 40$. Still make sense?

Mew

@heather we aim to learn because it increases our confidence to overcome a variety of threats (e.g. employment, health etc.)

Jim

@heather not a bad answer. I'm a bit hesitant about endorsing the microwave food example you used, but it's not a big deal. Your explanation might have been slightly above a 6 year old level. But I'm not entirely sure how to explain the concept of a non-physical entity like a field or current to a 6 year old anyway

Mew

@heather we seek "meaning" because this helps us overcome the ultimate threat of death

user228700

@JohnRennie Nope. This is where I lose it.

user228700

1:02 PM

Gimme a second to think about it again...

Sanya

@heather I think you nailed the problem with the question, so yeah - I think it's good

Mew

@heather if there is a threat we feel we don't have the confidence to overcome, we have a motivation to tackle that (e.g. seeking meaning)

heather

@Jim, okay. I'll try to think of a better example at the end.

Mew

@heather, Maslow's hierachy si then just a simple application of my more fundemental idea

heather

@Mew, that doesn't explain lack of motivation.

Mew

1:03 PM

of course it does

John Rennie

@Kaumudi Suppose we replace the water by air (or vacuum) so the middle tube only contains liquid in the hatched area. Is that OK?

Mew

One has a lack of motivation when one doesn't have a perceieved existential threat

and everyone can "quench" a threat in different ways

e.g.

user228700

@JohnRennie Wait, what? OK...

Mew

one person overcomes the threat of dying with seeking meaning in family

while another overcomes the threat by seeking medicines for immortality

John Rennie

@Kaumudi is that OK I can carry on with this approach?

user228700

1:05 PM

Yep!

Mew

oops meant to edit it not delete

Secret

@heather So to summarise, because we saw 3 components of the magnetic field, electromagnetism might be most likely 3 dimensional classical speaking. Acuriousmind MAY have the answer to the question in the quanutm level.

Mew

everyone tries to seek the confidence to overcome a threat in different ways

and psychologyically one MUST overcome the threat or face feeling "fear"

John Rennie

OK. We'll ignore the air so the pressure difference comes from the fact one side of the tube has more water than the other. Specifically it has 40cm more water than the other. Yes?

user228700

"Hatched area"?

Mew

1:06 PM

so to avoid "fear" one can either (A) directly overcome the threat or (B) rationalise why the threat isn't real

so a lack of motivation is often due to (B)

Jim

@heather you could try to use an example like a river. You can define the width of the channel or the length of a river, but what are the dimensions of the actual flowing water in general? It depends on the river, you might say. Similarly, electricity is the current of electrons. You can give dimensions of a specific conductor, but there's no point in giving dimensions of electricity, it's like flowing water, the number is only good for the exact part of wire you refer to

John Rennie

@Kaumudi the bit I've outlined in red

user228700

@JohnRennie There's only air in both the glasses and the liquid is still there?

John Rennie

@Kaumudi what I'm working up to is calculating the pressure difference if the pipe and liquid were momentarily in that state. It wouldn't be stable because the liquid would start to flow out of the pipe. But that's OK because I want the difference at that moment in time.

user228700

Oh, alright, OK. (Sorry :-/)

John Rennie

1:09 PM

Does it now make sense that the pressure difference would be $\rho_1 g 40$ ?

Jim

@Mew Pleasure is not simply overcoming obstacles. I'd say pleasure is derived from a combination of 1) chemistry and 2) attaining goals we perceive as set for us by either others or, more potently, by ourselves. Happiness can also come not simply from confidence that we can attain these goals, but even in the knowledge that if we are doomed to fail to attain them, we pursued them in a way that makes the most logical sense to us. But that is a derivative of attaining a goal

John Rennie

i.e. just $\rho g h$ as usual but the density is now $\rho_1$ and the height difference is 40cm.

user228700

But u said:

user228700

8 mins ago, by John Rennie

@Kaumudi OK. If you calculate the pressure difference just due to the liquids in the tube in middle it is $\rho_1 g 40 - \rho g 40$. Still make sense?

Mew

@Jim overcoming an obstacle doesn't necessarily require directly overcoming it, but even coming to terms with it

@Jim e.g. if one knows they will inevitbly die, but is able to rationalise it by knowing they are a part of the universe, they have in overcome it in their minds

user228700

1:11 PM

(I'm really sorry :-/)

Mew

@Jim someone else may find a miracle cure for death, and they have overcome the obstacle in a more direct way, but both can lead to happiness

John Rennie

@Kaumudi to try and simplify how i got to that I'm approaching it in two steps. The first step assumes there is liquid only in the hatched area and we have air or vacuum in the unhatched 40cm bit on the left.

Mew

@Jim pleasure is derived from chemistry, and indeed my theory is based on the workings of the limbic system

@Jim the human body for instances desires food, and when food is eaten pleasure is felt (mediated by the release of chemicals)

John Rennie

@Kaumudi So the pressure difference due to the just liquid in the hatched area is $\rho_1 g 40$.

user228700

Sigh. OK, I guess, although my head is not wrapped around the idea yet.

Mew

1:13 PM

@Jim of course one could simulate the release of chemicals but the body is designed to release them when particular goals are attained (usually physiological)

I believ however happiness is distinct from pleasure as i outlined

John Rennie

Look at this this way (diagram incoming)

Mew

@J+

Jim

@Mew what theory? Saying that happiness is the result of accepting/overcoming the things that might make you unhappy (which is more or less the defining attribute of a problem) is a tautology

John Rennie

Mew

@Jim my theory is for human motivation

John Rennie

1:15 PM

@Kaumudi Now is it obvious that the pressure difference would be $\rho_1 g 40$ ?

Mew

@Jim as an alternative to Maslow's heirachy of needs

Jim

@Mew we are motivated to rationalize our existence and cope with our mortality in a desperate, but mostly civil, search for our own version of meaning in our life?

Mew

@Jim Maslow's hiearchy fails in that people can seek needs higher in the pyramid than predicted by Maslow

@Jim it's not just about mortality, that is just one obstacle

@Jim any threat to our survival is an obstacle

user228700

@JohnRennie: No :'-( I seem to have some fundamental problems understanding this.

Mew

@Jim so not eating and drinking, preditators etc.

@Jim now when we eat we feel pleasure

user228700

1:17 PM

I'll watch some videos, do some more learning and then try to solve it again.

Mew

@Jim But when we see as bancquet prepared just for us, we feel happy (confident we can soon feel pleasure)

Jim

@Mew without mortality, there could be no threats to survival. So that, again, boils down to coping with mortality

John Rennie

@Kaumudi The pressure due to a column of liquid of height $h$ is $\rho g h$. Yes?

user228700

Yeah...

Mew

@Jim yes but I mean it isn't necessarily us conciously thinking about mortality. The brain is hardwired to eat even withotu thinking of death

user228700

1:19 PM

Hang on.

ACuriousMind

@DanielSank You're right, I find that amusing :)

2

user228700

I get why that difference would be $40 \rho g$ but not why the pressure is equal at a level.

Mew

@Jim as we age, our minds learn what "goals" are useful in maintaining and improving our confidence to always overcome existential "threats"

our limbic system actually stores these learnings in the same part of the brain associated with true physiological needs

John Rennie

@Kaumudi if you're happy the pressure difference is $\rho_1 g 40$ I can move on to the next step in my fiendish description :-)

user228700

But I don't really get that. I can't "feel it in my spleen" :-P

Jim

1:22 PM

@Mew it's also hardwired to breathe but I get no happiness from knowing that I'll be able to breathe a minute from now (I get no unhappiness from it either, it's mostly neutral). It matters not whether that is what drives us to do something; that is still the root of the sentiment. Evolution has made the continuation of genetic line a biological imperative. This translates always to the derivation of positive emotions from actions we see as fulfilling related goals and coping with mortality

John Rennie

@Kaumudi On the left you have a column of liquid of height $h$, so the pressure is $\rho_1 g h$. And on the right you have a column of height $h-40$ so the pressure is $\rho_1 g (h-40)$. Make sense so far?

Jim

@Mew however we define this set of moral values (preservation of self, of others, of all, etc), that's what it usually all boils down to

user228700

@JohnRennie: How about I go learn some more and then try again? I haven't done enough on my part.

John Rennie

@Kaumudi we are literally one step away from the answer ...

user228700

@JohnRennie Yeah...

Jim

1:25 PM

@Mew although the Law of Exceptions mandates that a few individuals would derive pleasure from the exact opposite: Destruction of self/others/all/etc

John Rennie

@Kaumudi shall I take that one step?

user228700

Sure...

ACuriousMind

@Jim "This translates always to the derivation of positive emotions from actions we see as fulfilling related goals and coping with mortality" [citation needed] Evolution is not a purposeful mechanism, and human pleasures are far from uniform across the population.

John Rennie

@Kaumudi OK. Considering just the hatched liquid the pressure difference is $\rho_1 g 40$. But now we put the water back. Specifically we put 40cm of water back, so the pressure of the water is $\rho g 40$. So with the water the pressure difference is $\rho_1 g 40 - \rho g 40$.

Mew

@Jim I think there are 2 ways we overcome physiological threats

(1) Action them

user228700

1:27 PM

@JohnRennie Yeah, I guess...

Mew

(2) Rationalise them

Jim

@ACuriousMind true, because some see continuation of genetic line more ambiguously than others. I define it as continuation of intelligent society. You might define it as continuation of all life. Bob from Chicago might only care about himself. And, there is the Law of Exceptions, as I mentioned

Mew

but either way we must overcome them because the psychological pain of not overcoming them is too great

Secret

@GRB she would understand electricity as a flow of electrons. In much the same way as a flow of water might turn a wheel, a flow of electrons down a wire might light a bulb. Initially, that's how I started my answer to her. However, to a six year old, an electron is then a 'thing' which must have physical dimension - whereas I was leaning towards heather's answer (but not quite so well described !) — Harry 2 mins ago

Mew

Now we seek to maximize the chance of actioning them, and this forms the basis for goal setting

Secret

1:28 PM

Now that's a HARD question

from all we knew, electron behaves point like

John Rennie

@Kaumudi But rmember when I started out I ignored the bit in the middle and calculated the pressure difference due to the tanks at the sides. I said it was (John scrolls up) ... $P_1 - P_2 = (P_a + \rho g h_1) - (P_a + \rho g h_2)$

Mew

and as we attain the physiological needs, we then need to maximize our confidence that we will continue to attain them in the future by building larger hierachial protection structures

but some problems just can't be solved

e.g. our complex brains realize everyone will die

in a famine we realize we might not be able to eat no matter what

in thses cases to avoid the pyschological pain of not meeting a need we have to

(B) rationalise

which means thinking of ways we can trick our brain into stopping the negative emotional response (which causes pain)

user228700

@JohnRennie Yes, u did...(It's a little weird when u reference urself in 3rd person :-P)

Secret

nvm, does not work

John Rennie

@Kaumudi and if the system is in equilibrium, i.e. nothing flows anywhere, the two pressure differences must be equal so they balance out: $$ (P_a + \rho g h_1) - (P_a + \rho g h_2) = \rho_1 g 40 - \rho g 40 $$

Mew

1:30 PM

@Jim ultimately our goal is to reduce the pyschological pain, whether that be combating the threat directly or just tricking our brain to stop the pain

user228700

Yes, and that's how we get the equation, OK...

John Rennie

@Kaumudi I guess you probably ought to have a think about it on your own time because I rushed through the last bit.

Mew

It is through (B) that we see weird behaviours that may be counter productive to (A)_

e.g. hunger strikes

laziness

depression

user228700

@JohnRennie Yes, I definitely do. I can tell that u can tell that I'm not fully convinced :-)

Jim

@Mew again, evolution selected organisms with instinctual tendencies towards preserving the self. This is obvious. Those more likely to preserve the self, or with that predisposition, are more likely to survive to propagate the replication of DNA/RNA. The things you describe may not be explicitly caused by this, but you can trace them all back to said tendency. In humans, at least

Again, the Law of Exceptions always applies

user228700

1:33 PM

Thank you :-) _/\ _

John Rennie

@Kaumudi if it helps I'm kind of mentally putting valves in the tubing where the dashed line is and calculating what the pressure differences would be at those valves if the valves are closed so no liquid can flow.

ACuriousMind

@Jim 1. I highly doubt such a high-level abstract goal can be acted upon by genetic natural selection because I know of no genes that encode such concepts. 2. I don't see what the selection pressure for "continuation of intelligent society" or "continuation of all life" would be.

John Rennie

@Kaumudi If nothing flows when I take the valves away that must mean the pressure differences balance out.

user228700

Yeah, OK, that makes some sense...

Mew

@Jim the tendancy natural selection chose was for the limbic system to produce pain when physiological needs aren't met and in response to survival threats

ACuriousMind

1:34 PM

What can reasonably be selected for is a desire to procreate, but not out of an awareness that this continues your genetic line but merely as a hard-wired instinct.

Mew

@Jim but then we built these complex brains that actually send signals to the limbic system and can have some control over it

user228700

@JohnRennie Thank you :-)

Mew

@Jim and when we feel pain we try to control it by supressing or tricking the limbic system

John Rennie

@Kaumudi The pressure differences on the bottom sides of the valves are due to the tanks, and the pressure differences on the top side of the valves are due to the water in the middle pipe.

Mew

this is where rationalising comes in

and goal setting too

John Rennie

1:35 PM

That's why I calculated the two bits separately.

user228700

@JohnRennie Yeah...

John Rennie

Anyway I'm going to get lunch now ...

Mew

Goal setting again is to increase the confgidence that threats (which can cause physiological pain )can be overcome

Jim

@ACuriousMind That's personal selection. To me, it's equivalent to continuing my genetic line, which makes it easy for my subconscious to rationalize those types of actions. And the instinctual preservation of self is what drives fear, etc. I'm pretty sure it's well understood that self-preservation is encoded genetically, or wherever instincts are built into an organism

user228700

@JohnRennie OK, bye :-)

Mew

1:36 PM

@Jim of courss self preservation is genetically selected

John Rennie

We'll leave the psychologists to analyse their fundaments, or whatever it is psychologists do when they're pretending to work :-)

Mew

@Jim but this theory is about how the prefrontal cortex (rational brain )interacts with the limbic system (instinctual brain that causes pyschological pain response to threats)

ACuriousMind

@Mew What theory?

Jim

@Mew I saw we test this by having 2 controls and 2 test subjects. For the test subjects, we remove most of the prefrontal cortex of one and most of the limbic system of the other. Not so much that they die, but enough to make a noticeable difference

Any volunteers?

ACuriousMind

@Jim Huh? Sure, basic self-preservation and procreation are selection for. "Continuing intelligent society" is not, and neither is the abstract goal of "continuing my genetic line". What can be selected are inclinations for specific actions, not such goals (otherwise we humans would have to have an inborn awareness of what a genetic line is).

Mew

1:41 PM

@ACuriousMind that motivation is governed by increasing one's CONFIDENCE of overcoming physiological threats. When this confidence is icnreased, the cortex tells the limbic system and happiness ensues. When a physiological threat is actually overcome pleasure ensues.

The theory also states when the cortex can't actually directly overcome a threat (e.g. knowing one will eventually die) the cortex will rationlise (e.g. deciding family is important) in order to tell the limbic system to avoid psychological pain.

ACuriousMind

Uh

I have no idea what you just said.

Mew

oh k

it is an alternative theory of motvation to Maslow's Hierachy of needs (although much of the hierachy can be deduced from this theory)

Jim

@ACuriousMind Making babies is a continuation of genetic line. We instinctively want to do that. Higher level brain functioning allow individuals to recognize the driving motivation behind this and broaden it as the wish, that is what I was trying to say. For me, I broaden it to realize the scope of continuing all of us, not just myself. I'm saying basic self-preservation is coded for as is procreating, but we also extend those in ways that allow broader application but mimic the underlying concept

I'm talkin 'bout SEX, baby!

ACuriousMind

@Jim I'm seriously not convinced that a disposition to "preserve humanity" follows from us recognizing the evolutionary origin of the urge of self-preservation and abstracting that to the goal of preserving the "human line". In particular, not a single moral philosopher known to me has ever argued that.

Our higher brain functions have no issue leading us to do things that are detrimental with respect to fitness/procreation

Mew

correct the higher brain functions are detached from physiological needs

the higher brain functions are connected to the limbic system, but they can think independently of it

ultimately the higher brain functions are servants of one's emotions however

ACuriousMind

1:49 PM

1

Q: How many dimensions does electricity have?

My six year old daughter asked me this morning, 'how many dimensions does electricity have ?' What would be the best answer bearing in mind the age !?

electricity dimensions

Jim

@ACuriousMind I agree, I'm not convinced of that either. The disposition is for self-preservation. Preservation of humanity is a conscious choice of some individuals to extend this disposition based on what they deem to be logically consistent reasonings

ACuriousMind

Can someone give me a reason I should not close this as unclear what you're asking?

Jim

@ACuriousMind Because it's clear what they are asking

ACuriousMind

It's got three answers and a lot of comments because people don't want to discourage a six-year old child, but I don't see how it's a meaningful question

@Jim it is?

I have genuinely no idea

Mew

@Jim many people actually do "feel" the need to preseve humanity not just think it though

Jim

1:51 PM

How do you answer to a six-year-old the question about what the length-width-depth dimensions of electricity are?

Seemed clear to me

Not a terribly great question, but clear

ACuriousMind

Okay, that's a clear question. But what's the physics question here?

"How do I tell my child their question doesn't make sense?" is not a physics question :P

Jim

@Mew Yeah, I'm willing to say that's attributable to the social creature mentality we have. Kind of like being pack animals, we want to maintain our societies. But I'd have to give myself a [citation needed] on that one

Secret

The physics is the number of dimensions of electricity (which in a sense is the number of dimensions of electromagnetic phenomenon in terms of current flow given various conditions)

Mew

@ACuriousMind the question should be closed in my opinion

It's nonsense

Sanya

@ACuriousMind big bad mod :<

Jim

1:54 PM

@ACuriousMind It's a grey-zone. I'll give you that. But the way you explain it is by explaining the physics concept of electricity as not a definite physical entity of its own. That's kind of physics-y

@Sanya Shhh. He might hear you

Mew

@ACuriousMind if this question is on topic, i have 1000 similar style questions to ask

I can't wait

Secret

For me, I do find the question interesting, probably because I automatically filtered nonsense away when I read questions in general thus nonsense are invisible to me

ACuriousMind

@Sanya Well, I just think about what would have happened if the question didn't mention that this is a six-year old's question

The question "How many dimensions does electricity have?" would have been downvoted and closed almost certainly.

Sanya

@ACuriousMind of course it'd be closed as gibberish

Mew

well really there is no 6 year old

ACuriousMind

1:56 PM

Yeah, and we (well, at least I and those who read the manual :P) always say that it's the question, not the asker that matters

Mew

he should be honest us

ACuriousMind

In part because we're not a forum, but also because we can't really verify any sort of information about askers.

Sanya

as could this be - but I find it a good sign for our community that it's not :p and you can consider that even if there was no real child, the answer adresses a different issue ...

Jim

Would it have been closed?

Can counsel cite precedence?

ACuriousMind

@Jim Yes, but preferably precedence from the last two years

Secret

1:58 PM

@ACuriousMind I actually have a split second thinking about this when I first read the question, so you can say I (like most people) are being influenced/framed by that "six year old phrase. That said, "to not discourage a six year old" never occured in my thought

ACuriousMind

I have the impression the site was more lenient in the beginning, mostly because traffic was lower and there wasn't so much of a need to discourage bad questions flooding the site.

Mew

this question sux is it closed yet?

Jim

@ACuriousMind I was actually asking for precedence, not offering it

Secret

It also have to do with me that I have a habit of finding sense no matter how nonsensical some information is, which is why I end up finding it interesting after interpreting it in a different way

ACuriousMind

@Jim Oh. You want me to cite other nonsense question that were closed? :P

Jim

2:00 PM

Or someone else

user123733

0

Q: causes of entropy change

My sir told me entropy change due to two reasons 1) entropy created 2) entropy due to heat exchange But I do not understand how they both are different . I am getting confused . Can anybody explain me this with an example each.

entropy

Help need in this

Jim

If I'm the one on the fence, I shouldn't be the one citing precedence

Secret

^ VTC as lack of research effort

Sanya

@user123733 we all saw your post - if someone decides to take it up, they will even without you asking in chat ;)

user123733

Okay

Mew

2:01 PM

@user123733 I didn't see your post

Jim

^ that

Mew

my six year old just asked me how much time there is in one meter

may I ask here?

user123733

@Mew then can you help me in that. Please

Mew

@user123733 I have my own question to post first

Sanya

@ACuriousMind I'd claim the bad questions that flood the site are "I don't understand XYZ, plz xplain" which usually stay open (I do flag them for fun from time to time) - not the few questions "how can this be explained adequately at level xy" which happen rather seldom anyway

Secret

2:03 PM

(Potentially dangerous comment. Please delete if this is found offensive) The entropy question above cannot be asked by a six year old as no known six year old know about entropy to that degree

Mew

think of the children

user123733

@Mew after that can you help

Jim

@Mew such a simple answer should be obvious to anyone. That question has separate problems

Mew

@Jim what problems?

Jim

@Mew anyone knows the difference between time and distance and can say "They aren't the same thing". Sometimes it's hard to explain how electricity has no definite dimensions

ACuriousMind

2:04 PM

@Sanya Good point. Thinking about what you and Jim said, I think the question is acceptable, although I would preferr the question itself elaborated a bit more on what "how many dimensions does electricity have" is supposed to mean.

Jim

Lack of effort applies to your question

Mew

@Jim but she actually asked how much time in 1 m^3

and i'm not sure if there is a finiite or infintite amount of time in such a box

Jim

and you said...?

Mew

like does the universe have a a certain amount of time allocated to each bit of space?

I dunno

I think I should ask here

Jim

think like a child

Sanya

2:06 PM

@ACuriousMind I think in the end the elaboration at an age-adequate level is actually already the answer, so I think if OP could elaborate, he'd not have asked :D

Jim

"They're two different things. Time and volume aren't the same. I won't tell you to wait a litre nor use a minute of salt."

ACuriousMind

@Jim Well, but you can use a minute amount of salt!

And you can also take seconds if there's still food left

Jim

an hour of salt then

I'll use a different language if you're going to do that

ACuriousMind

Hm, I have to admit I got no stupid response for "hour" :)

My fingers are not good at typing today :P

Secret

0

Q: relativistic ship collision

the question goes as so: two ships are measured to travel towards each other at 0.6c and 0.8c respectively with respect to earth. they are measured from earth to be at a distance of 2.52 x 10 ^11 m. the crews have escape pods that can be launched in 5 minutes. do they live? I did it by first calc...

special-relativity

am i right= off topic

Mew

2:11 PM

@Secret looks more like a question for physics.qandaexchange.com

Secret

Speaking about qanda exchange, you need more high level questions there to attract high level users

Mew

@Secret ok I look forward to your questions

Secret

I usually don't have homework questions, and I am currently mostly in maths anyway

there might be a possibility that I will start to populate the sites with questions again when I return to QM and QFT studying

right now my productive wavefunction is mostly in the maths chat

Mew

ok cool

yeah I hope to learn QFT too

so when I do I will have some questions myself aswell

@ACuriousMind what text do you recommend for learning Lie algebra/Lie groups

ACuriousMind

I can't recommend any text because I haven't read any

I think the standard is Fulton & Harris, though

Mew

2:15 PM

ok ty

Secret

physics.stackexchange.com/questions/297163/…

nonmainstream= off topic

The question itself, however requires quantum gravity to answer

Mew

I think it's ok

he should however say that "a six year old asked him ..."

ACuriousMind

@Secret Unless you want to get input on your opinion about questions, just flag them instead of posting them to chat.

Mew

1

Q: entropy change in isolated system

In my there is a topic named as 'Entropy change in isolated system' as given below . I could not understand anything in this . Could anyone explain me the concept behind this.

thermodynamics entropy

^is that off topic?

Secret

but most off topicness is generally not serious enough to bother moderators with too many flaggings...?

@Mew Lack of research effort, how to fix that question I have no idea

ACuriousMind

2:20 PM

@Secret what?

Secret

well, perhaps I have mistaken, seriousness is evaluated on the level of something disruptive like a flame war or something similar?

ACuriousMind

1. Off-topic flags don't go to moderators, just into the close review queue. I didn't mean you should use a custom mod flag, just the standard "this is off-topic because..." flags. 2. Never hesitate to flag anything because it would "bother" the moderators. If there is some sort of issue with it, flag it.

Secret

ok noted

Jim

8

A: Is Einstein's theory really challenged by the recent paper in news?

Magueijo came up with the variable speed of light idea nearly twenty years ago. The motivation was as a way of explaining the homogeneity of the universe. At that time inflation was still somewhat controversial (perhaps it still is) and Magueijo's theory was mainly intended as an alternative to i...

Nice job @JohnRennie

Might only have worded it slightly different myself, but you gave a great review of the work

Secret

Is Webb telescope going to space on 2018?

Mew

2:23 PM

@ACuriousMind are there any QM theories where the speed of light is uncertain or is the speed of light always well defined?

ACuriousMind

I can't exclude with certainty that there isn't some theory where it's variable, but all relativistic quantum theories are Lorentz invariant and therefore have constant speed of light.

Mew

@ACuriousMind they are pre defined to be Lorentz invarient aren't they?

ACuriousMind

(with the usual caveat that in GR/curved scenarios "speed of light" becomes a bit more difficult to define and depending on which you choose you can say it "changes")

@Mew Yes

Mew

this is probably the assumption holding modern physics back

Secret

This is information entropy, but is it a bit more maths related?

0

Q: How to compute entropy of networks? (Boltzmann Micro-states and Shannon Entropy in network systems)

(I also asked in SO here a few days ago, thought it may be also interesting for physics-related answers) I would like to model a network as a system. A particular topology (configuration of edges between vertices) is a state-of-order of the system (a micro-state). I am trying to compute the ent...

thermodynamics entropy complex-systems scale-invariance network

that is, do entropy in networked systems in IT considered to be part of physics?

(and actually there's a serious problem with this question otherwise: As it is a direct cross post)

flags

Jim

2:30 PM

@Secret google james webb space telescope and you can immediately see the scheduled launch is in october 2018

Secret

ok cool, my memory had not failed me. By that time there will be more information on VSL (cariable speed of light) experimental checks

my uni also has a couple of groups working on VSL models and experimental detections

Jim

@ACuriousMind yeah, that might mean that it's only variable in very early times and that other times fall under the special case scenario where it's constant (or approximately so)

ACuriousMind

@Jim Hmm? Lorentz invariance is crucial, if you drop it the whole machinery for particle interpretations and causality in QFT falls apart.

In particular, you lose the ability to say what the mass and spin of a "particle"/state are

QFT without Lorentz invariance as a fundamental theory is rather infeasible

Jim

The funny thing is that the co-author of this paper, Niayesh Afshordi, was one of the people I approached about supervising my PhD. I'd be working with him on related research right now but, in his words, "You're a great student and I'd like to take you on except I already have 8 graduate students and can't possibly handle another". Damn my luck

ACuriousMind

(though there is of course no problem with it as an effective theory, as in many condensed matter scenarios)

Mew

2:34 PM

@ACuriousMind so QFT has no room to handle a lorentz invariance violation?

Jim

exactly. If it's an eft valid for all times after, say, $t=10^{-30}s$, then pretty much all QFT we know and love remains valid

Mew

what happens if we discover that lorentz invariance doesn't apply 100% at the quantum scale?

does this mean we need a completely new theory?

Secret

any cracks in our current models will point towards new physics, and it might point towards a way to reconcile gravity and quantum field theory

Jim

@Mew no, then we develop a theory which simplifies to the current one in special cases and use the generalized theory for when the special case one isn't a good enough approximation

The same thing we've done with pretty much every physics theory in history

Mew

sciencedirect.com/science/article/pii/0370269382908073

ACuriousMind

2:37 PM

Well...this is a subtle issue. QFT does not need to be Lorentz invariant per se. You can also have QFT in Euclidean spaces, and also non-relativistic QFT which is then Galilean-invariant.

But in order to have a QFT that is not Lorentz invariant as a fundamental theory, you'd need to explain the emergence of Lorentz symmetry in e.g. the SM from a theory where it is absent.

Mew

sounds challenging

but doable

ACuriousMind

@Mew How?

Jim

@ACuriousMind Physics!

Secret

Do lorentz symmetries have generators? Like how translation invariance implies conservation of momentum, time translation invariance implies conservation of energy?

Jim

so are you asking if there's a symmetry that implies the speed of light is conserved across boosts?

Mew

2:42 PM

@ACuriousMind I'd tell u but I don't want anyone to steal my ideas

ACuriousMind

@Secret Of course.

Jim

@Mew is it magnets?

Mew

@Jim wtf how did u know

Jim

magnets

Mew

lol

Secret

2:44 PM

So (rough guess as my background in particle physics is not QFT advanced yet) such a lorentz symmetry absent underlying model will need to somehow involve a mechanism that produce these generators which then give rise to the constantcy of the speed of light in the relativistic limit under inertial frames

Thta might mean new fields and hence new particles to be hunted by particle experiments

Mew

na just new maths

but yeah it's highly doubtful lorentz invariance holds completely

ACuriousMind

@Mew why?

Most people believe the exact opposite: Not only do we want our theory of everything to be Lorentz covariant, it should be generally covariant.

Mew

I guess it's the modern day ether

why should it be lorentz covarient?

why demand this of our theories?

user129412

Does anyone know of a paper that looks into what happens to the resonance fluorescence of an (artifical) atom placed inside a cavity under strong driving? In free space one observes the Mollow triplet. I'm wondering how the cavity changes this.

Mew

@user129412 no sounds trivial

Secret

2:51 PM

Publish or perish, and it seems the whole world is running out of funds

Mew

lol that guys desk

wow

papers are read by an average of 10 people?

what's the point?

82 percent of articles published in the humanities are not even cited once.

crazy

Reseach is too free for all these days

Secret

> One unfortunate effect of this specialization is that the subject matter of most articles make them inaccessible to the public, and even to the overwhelming majority of professors.

Mew

yeah it doesn't help anyone

Secret

I knew this feeling: Back in my honours, I sometimes need to read 10+ layers of paper via following the links in order to understand all the terminology used in that one paper

Mew

scientists need to work together and define the key areas of interest and research goals

and then work out whos going to work on what

and everyone report back

Secret

2:56 PM

There's collaboration, in fact, there's more collarboration than ever. The issue is this publish or perish culture, and the poor communication, as many of pointed out via sarxiv and arxiv, most of them are incomprehensible with poor abstracts

Mew

yeah I don't get it though

why is there pressure to publish something that only 10 people read

is this making the world a better place?

Secret

Some researchers are also mentioning about the issue of impact factor to rate a publication, and implications. Danielsank some year ago also talked about various things about the research environment that is not quite right

Mew

yeah it's terrible

great minds are being wasted on solving trivial tasks just for a publication

Secret

The article have mentioned that: They are trying to get funded. If you ask any random scientist, one of their greatest concern is getting funded

competition for funding proposals are fierce, at least for chemistry

Mew

and who is funding this BS research though?

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