The h Bar

Avnish Kabaj

04:59

in The Periodic Table, Dec 6 '18 at 11:00, by orthocresol

“Professor Dumbledore. Can I ask you something?"
"Obviously, you've just done so," Dumbledore smiled. "You may ask me one more thing, however."

user400188

07:50

So, I have a friend who is working in the wrong field of physics at the moment (not enjoying it.) They are still undergraduate however and have time to change this.

They are currently working on a summer project which will soon end. If they leave now it will be time (and a scholarship) wasted on them, because most of the summer project was teaching them the basics of what to do (a 6 week project.)

They are about to start their final year in undergraduate physics, and in this year the university offers a project based unit, with a similar structure to a summer work project, but with assess…

I was wondering if anyone here has experienced or seen anything similar to this before, and what their advice to my friend would be. My normal advice to them would be to take your time to find the right supervisor/field of physics, and work under them regardless of the current work. (After all, they are still undergraduate and are allowed to make a mistake.)

However, due to the deadline for the project choice, it might not be easy to find the right supervisor. Which is why I’m asking online for any advice.

If this is the wrong place to ask, please let me know and I’ll remove it.

Anonymous

@user400188 It's fine.

user400188

Thanks

Anonymous

@user400188 So what's this "wrong field of physics" you're talking about?

user400188

Currently they are working in experimental physics on ultra cold atoms (BEC creation). They have never shown an interest in the field however, and I think they only took the summer work because they thought it would be like any other job.

Their actual interest is in particle physics as a theorist.

Anonymous

From what I've discussed with my seniors, "undergraduate" projects don't really matter much if you manage to find go ahead and find good supervisors for your graduate school. Also, if they're learning some computation/programming stuff in that project, that'll be helpful no matter which field of physics they transition to.

Anonymous

08:01

That said, it is of course best to take some time to find a project that they'll enjoy, as the learning the basics of the field they're going to transition to, during the undergraduate project might give them a minor head-start.

Anonymous

@user400188 Why not ask this on Academia? There are several experienced folks there who can guide you.

user400188

I thought about it, but I wasn’t sure if it’s the same deal in every discipline or just physics, and if there were many physics there.

I probably will ask it now that you have suggested it.

Slereah

08:49

morning

ACuriousMind

mornin'

Anonymous

morni'

Novalium Company

09:26

morn'

Slereah

mor

Novalium Company

This picture shows how much of a certain part of the EM spectrum the sun emits and I was wondering, in order for the sun to be white, shouldn't R, G and B be equal amounts?

I mean, the sun should appear mostly green and yellow and the light that shines should be mostly green and yellow but it's not?

The sun is white and for it to be white it must emit equal amounts of R, G and B, but according to the picture it doesn't. Soo, what is going on?

John Rennie

@NovaliumCompany the sun is actually slightly yellow, but since the sunlight is everywhere our eyes adjust and see it as white.

Slereah

Also the eyes aren't perfect detectors

in sunlight they tend to saturate

(TIP : Do not look at the sun)

John Rennie

If you sit in a room with very blue lights, e.g. arc lights, for a while then look out of the window the sunlight outside will look noticeably yellow.

Remember that colours are just human perception.

Slereah

09:40

Hell your eyes don't even need to be stimulated to see colors!

ACuriousMind

@Slereah Talking about 'shrooms? :P

John Rennie

@ACuriousMind not working today?

ACuriousMind

@JohnRennie Nope, took the day off

Slereah

@ACuriousMind Well serotonin agonists in general :p

or even $\kappa$-opioid agonists!

Brain's a giant mess really

Those poor guys at the neurology stack exchange

John Rennie

@Slereah mine certainly is :-)

But then life is far more entertaining that way.

Slereah

09:50

Why does serotonin act on reward, vision and diarrhea

That's not a proper separation of tasks

ACuriousMind

@Slereah That's nature telling us life's basically shitty

Slereah

When I read about the human body I just think of some intern in charge of a huge mess of a software changing things at random until it works

thank you evolution

ACuriousMind

@Slereah Ah, so you're a believer in Unintelligent Design

Slereah

Unfortunate!

We get stuck with the intern

I mean I guess it makes sense why he slapped it together in 6 days

We get stuck with Azathoth the blind idiot god

Playing his accursed flute

that jerk

ACuriousMind

Careful, while Azathoth worship has a rather abysmal survival rate, I'm not sure taunting him is any better

Slereah

10:00

Well that's the nice thing about the Elder Gods

They are indifferent to humanity

Think they're too good for us

Except Nyarlathotep I guess

He has gone native

John Rennie

First thing this morning I logged a call that disk 2 had failed in a customer's server. But being half asleep (it was around 5 a.m.) I put in a call that dick 2 has failed. The day I stop finding these things funny you can place the order for my coffin.

ACuriousMind

@Slereah For being indifferent they always seemed to me to be strangely reactive to cultists

I think they're just playing hard to get

Slereah

@ACuriousMind Well to paraphrase some post I've seen

If you heard a bunch of ants calling you, what would you do?

ACuriousMind

@Slereah Freak out, then start rolling in the biology grants to study this exceptionally gifted tribe of ants?

Slereah

@ACuriousMind A real ant apocalypse!

Ant alien abduction

That's what happens in the Mythos when you're transported in a strange land from beyond the stars, I guess

just a bunch of those guys poking you with sticks

ACuriousMind

10:09

@Slereah Hm, I guess that's an accurate way to look at it

Slereah

I like the great race of the Yiths because they look kind of goofy but also creepy?

Best design of the Mythos imo

Just look at those guys

Novalium Company

What the hell has happened to this chat room... :D

Slereah

Novalium Company

@JohnRennie So humans have adapted to perceive yellow as white? Wut??

Slereah

just look at those guys

with their little notebook

@NovaliumCompany sorry we are all under the influence of the old ones now

Human sacrifice is just around the corner

John Rennie

10:13

@NovaliumCompany well what does white actually mean? It means the colour that humans call white. It is purely human perception.

Novalium Company

Nope, white is the sum of all colors (of equal amounts)?

John Rennie

@NovaliumCompany nope.

Slereah

@NovaliumCompany have you ever seen an optical illusion

The brain's pretty easy to trick

Novalium Company

ye I kno, I is confusededed.

John Rennie

Yes we can write a definition of white light, but that definition basically comes down to light that humans perceive as white.

Novalium Company

10:15

Yes, colors are just interpretations of the human brain.

Slereah

I mean "white" isn't even a proper physical notion

there are no white photons

One context where I like to bring up Azathoth is cosmology because I remember a friend of mine making a joke about "if the universe is closed then what is inside?" and the answer was "Azathoth"

It's my go to answer to that question ever since

John Rennie

I read all the Lovecraft stories as a kid and I loved them. These days I'm a bit more conscious of the racial stereotypes he used, but I still love them.

Slereah

They are quite jarring

John Rennie

I'm not going to attempt to justify Lovecraft's prejudices, I'll just say he was of his time. Because I love his stories of elder gods, etc, etc does not mean I approve of him as a person.

Slereah

oh he was even racist by his era's standards

He was one of the first person to try to make really alien creatures, though

Novalium Company

10:26

Every color is associated with a wavelength right?

Slereah

@NovaliumCompany Define "color"

Novalium Company

An EM wave with a specific wavelength and a name that people have given it.

Slereah

Well your definition is exactly the same as your question, so yes

But there is no wavelength for pink or brown

John Rennie

@NovaliumCompany have a look at:

65

Q: Is it possible that there is a color our human eye can't see?

Is it possible that there's a color that our eye couldn't see? Like all of us are color blind to it. If there is, is it possible to detect/identify it?

ACuriousMind

@NovaliumCompany Not really - the spectral colors are, but you can see in that horseshoe diagram a lot of colors not associated to a single specific wavelength

John Rennie

10:28

The answers give a pretty good description of what it means for the eye to see a colour.

Slereah

oh and by the way

There are also these

Impossible color

Impossible colors or forbidden colors are supposed colors that cannot be perceived in normal seeing of light that is a combination of various intensities of the various frequencies of visible light, but are reported to be seen in special circumstances. == Types == These impossible colors are of two types: Colors that would be seen if the output strengths of the human eye retina's three types of cone cell (red, green, blue) could be set to values which cannot be produced by exposing the eye in normal seeing conditions to any possible combination of strengths of the frequencies of visible light...

There are colors not even associated with any combinations of wavelengths!

cf also

What if what *I* see as blue, *you* see as a slightly different blue because you're using Chrome instead of Firefox and despite a decade of messing with profiles we STILL can't get this right somehow.

Novalium Company

All I wanted to know is what is the color of the sun lol

Slereah

well look at it

Novalium Company

@JohnRennie I read it.

Slereah

(LEGAL WARNING : I do not advise looking at it)

It's not rocket science

Novalium Company

10:31

@Slereah I can't, the atmosphere is f*cking with me.

Unless I go to space of course.

Slereah

I mean you know, if you want to know the color of something, looking at it is still the simplest way to determine it

depending on how you define color 'course

Novalium Company

So colors are just an intepretation of the individual, so colors are different for everyone?

Slereah

but if you want to know the relations between EM wave wavelengths, eye color detectors and the brain interpretation

that's a whole 'nother can of worms

Novalium Company

So, nothing in this world really "has color"?

Slereah

that's more of a question for the philosophy stack exchange :p

Novalium Company

10:34

I was just arguing with a girl in my class that the sun is white, and she said that the sun is yellow, and we asked the geography teacher and she said the sun is burning red, and I'm like wetefe is goin onnn?

I tell them that the atmosphere has effects on how people on Earth perceive the color of the sun and if we went to space, the sun will be white, but here I'm told it's not white.

WETEFEE

Slereah

it's one of those questions you can't answer unless you define properly what you mean

ACuriousMind

@NovaliumCompany Well, you can determine the wavelengths something emits and then determine the response of a "standard" human eye. But there's lots of non-standard human eyes around (e.g. colorblind people, tetrachromats), so whether or not you want to call that "having color" is a question of how you define your words, not a question about physics or biology.

Novalium Company

So it all comes down to what is "yellow", "white"... "color"...?

Slereah

yes

and of course there's the old philosophy chestnut

Is the yellow you see the same as someone else's yellow

$$\Huge{🤔}$$

ACuriousMind

Can't argue about incomparable subjective perceptions, aka qualia.

Slereah

10:40

I just use my qualia detector

Novalium Company

So asking the question "What is the color of the sun?" is like asking "What is the pain when someone hits you?" wow the best analogy I've ever made.

Slereah

Well there too you can define it differently

you can measure it with brain activity etc

or consider the subjective experience

ACuriousMind

@NovaliumCompany Sure, but consider that for both color and pain we have established cultural norms of how to talk about it. Specific pain is often described as "stinging", "searing", or some other adjectives, and we feel we understand what these words mean, just like we feel we understand what someone means when they call the sky blue.

Novalium Company

So since colors are different for everyone (e.g colors are just interpretations of the brain), starting an argument on what is the color of the sun really doesn't make sense?

ACuriousMind

When someone asks you what color the sky is and you start going on about how color perception is subjective and there really is no objective notion of color, that's not what they wanted to hear and you're committing a cultural faux pas

Novalium Company

10:46

Lol

I don't give a duck what they want to hear. :D

Slereah

@ACuriousMind you may get tarred and feathered as a huge dork

ACuriousMind

@Slereah Ah, well, dork feathers can be stylish

Slereah

Man reading Reichenbach on GR was basically 200 pages of discussions like that

about what it means to take measurements

Very interesting but a bit abstract

and it was pretty ahead of its time for the 1920's

It's a bit weird that it had a discussion of closed timelike curves but nothing on singularities

ACuriousMind

13:26

Gnnnh, I hate it when a one-liner about basic mechanics nets me more rep than my last few answers together

Curse you, HNQ!

Slereah

that's the way it goes

Abcd

14:05

We omit constants in Big O notation whether they are in product or addition.

Now consider $f = \text{(10000 million)} x^3 + ....$

And $g = x^4 + .... $

So f is $O(n^3)$

And g is $O(n^4)$

Slereah

correct

Abcd

If one compares complexities one will say f is more efficient.But by looking at the functions, g appears to be more efficient!

ACuriousMind

What does it mean for a function to be "efficient"?

Abcd

@ACuriousMind least time

Slereah

Big O notation is concerned with asymptotic behaviour

Not useful for small $x$

ACuriousMind

14:08

The point of big-O notation is that it tells you how the function grows, not how large its actual values are.

Slereah

Here's an example for instance

Standard matrix multiplication algorithms are $\mathcal{O}(n^3)$

ACuriousMind

Certainly, for small values of $x$, $g$ is smaller than $f$. but if you keep increasing the input value, at some point $f$ will be smaller than $g$, and stay that way after that

Slereah

There are more efficient algorithms, such as Copperhead, which are $\approx \mathcal{O}(n^{2.8})$

Abcd

@ACuriousMind but that value might be very very large not very large.

Slereah

But due to algorithm overheads, it's not actually more efficent unless $n$ is very large

ACuriousMind

14:09

Sure, depends on your notion of "very" :P

Abcd

@Slereah overheads means?

Slereah

@Abcd Calculations to do beforehand

Coppersmith–Winograd algorithm

In linear algebra, the Coppersmith–Winograd algorithm, named after Don Coppersmith and Shmuel Winograd, was the asymptotically fastest known matrix multiplication algorithm from 1990 until 2010. It can multiply two n × n {\displaystyle n\times n} matrices in O ( n 2.375477 ) {\displaystyle {\mathcal {O}}(n^{2.375477})} time (see Big O notation). This is an improvement over...

$n^{2.37}$ even

Anonymous

14:29

10

A: Is the common Computer Science usage of 'ignoring constants' useful when comparing classical computing with quantum computing?

The common Computer Science usage of 'ignoring constants' is only useful where the differences in performance of various kinds of hardware architecture or software can be ignored with a little bit of massaging. But even in classical computation, it is important to be aware of the impact of archit...

Secret

14:41

@vzn
"Modernismania":
Define n-modernism to mean postpostpostpost (n times)... postmodernism

Then we have the following:

-1 modernism: No such thing as truth
0 modernism: There exists universal truths
1 modernism: Truth is context dependent
2a modernism: If you believe, then it is true
2b modernism: "Truth is context dependent" is context dependent
2c modernism: Truth is what is not context dependent
2d modernism: Truth has no meaning
2e modernism: What is important is the relation between truth and its context

ACuriousMind

15:04

@Chair Meta voting is even stranger than HNQ voting sometimes :P

user351417

@ACuriousMind It's certainly more extreme and FGITW-influenced.

user351417

Like if something gets to -1, it frequently shoots down from there, but if it's positive, it won't stay in single digits for a long time.

user351417

Bam, it goes to 14, presumably though the chat-effect.

user351417

@Blue Yes please, go ahead! It would be nice if we could avoid giving him reasons to use other channels to communiate.

Anonymous

→ 17 messages moved to Trashcan

ACuriousMind

15:11

Yay, rep cap -.-

user351417

@Blue Interesting, I didn't know there was a mod-only trash chat. So when you're considering options for deletion of messages, what are the options? I'm quite sure there's a publicly visible trash, and clearly there's this hidden trash. Presumably there's a permanent obliteration option which doesn't even move the messages?

user351417

What else?

user351417

@ACuriousMind That escape velocity question was somewhat... surprising. Lots of "me too" comments

ACuriousMind

Well, a mod can either delete the message, or move them to any other room in the network

Some of the other rooms are intended to hold deletion-worthy messages, like the Trashcan, but there's really nothing special about them other than that

user351417

@ACuriousMind In terms of deletion, is there a deletion which leaves the message visible to room owners (since I've seen JR mention that in a meta discussion) and a different one which hides it from everyone?

ACuriousMind

15:14

@Chair There is redaction, which removes the message entirely and is intended only for e.g. PII leaks

Anonymous

@Chair Yeah, that's the normal deletion. Apart from that we can also redact messages, in which case no one else can see the history --- not even mods.

user351417

Cool, thanks!

Anonymous

I used redaction to delete a tetrathonk once. :P

user351417

What's a tetrathonk?

Anonymous

@Chair Click on the link. ^

user351417

15:18

Wow what the hell did I just see?

Anonymous

I posted it in the Teacher's Lounge and some other mods were complaining that even after deletion it's visible for those who use the "view deleted messages" script. I didn't want it to stare them in face and finally redacted it. ;)

Anonymous

@Chair Lol XD

user351417

It looks like me doing math on the papers taped to the walls of my room.

user351417

Over three hours, there have been 51 votes on this thread

user351417

Must be some kind of a record.

Secret

15:26

The following [redacted] is [data expunged]

ACuriousMind

@Chair I have no actual data, but I don't think that's a record

Feels like a pretty "normal" HNQ to me :P

user351417

Do we want a set of rules resembling this or not? I think the meta discussion we had about rules a while back was not particularly firm about whether it's a good idea or not, if I recall correctly. I have some more time at my disposal now, so I may be able to put something together. Also, I imagine I'm more active on chat now than I was then, so it'd be less of a challenge :P

Anonymous

@Chair Yes, we do! I've been thinking about it for sometime, but didn't really get time.

Anonymous

It would be nice if you could put something together. I'd be happy to give inputs.

Anonymous

That math meta post is rather well written and I was thinking of following that pattern with perhaps some minor alterations.

user351417

15:38

I need a nice title, something related to food. "It's always lunchtime in the hbar" just sounds lame, but something in a similar vein to indicate that we don't want to be too formal is in order.

user351417

We also need a metaphysics pun to give our meta site's room an interesting name.

JMac

@Chair Seems quite normal for HNQ questions. Looking at my biggest HNQ question physics.stackexchange.com/questions/361679/… within 3 hours it got at least 40 votes between my answer and the question, and this was with only one answer to vote on. HNQ + accessible questions = easy votes for everyone

user351417

@JMac I wonder how things will change once SE does their thing which they've promised to do with HNQs. What if it suddenly becomes 'hard' to gain rep and all new 'experts' find themselves with less rep than people who answered easy HNQs and have lots of privilages?

JMac

@Chair To be frank, I don't think the experts should care, and I would hope they are the least likely to care, assuming they are still being treated well by the site in ways beyond arbitrary points. I'm pretty far from "expert"; but I wouldn't mind if HNQ didn't give so much rep. It's nice to have privileges, but I've always found answers like that aren't always personally satisfying.

it's nice to be able to say "oh good, it looks like a lot of people found this really useful" but at the same time, I'm often thinking, of all the things I post here, is stuff like that really worth the points it gets? I knew as soon as I read the pen question that it was going to go HNQ, so I basically made my answer really pretty, and what do you know, it's my most points on an answer

user351417

I dunno, those VtCs may go out of control, but there's no point in speculating since it's starting to look like the HNQ drama has died down and things will take a while to pick up again.

John Rennie

16:18

@Chair The h bar is always open ?

Anonymous

Relax...the h Bar is always open
We are programmed to receive
You can check out any time you like
But you can never leave!

Anonymous

:P

Anonymous

Something like that.

ACuriousMind

That sounds...creepy

John Rennie

The h Bar is always open in at least one universe

Anonymous

16:27

@ACuriousMind Trying to put together music and food references. :P

John Rennie

Collapse in the h Bar

John Rennie

16:58

@ACuriousMind that's OK, some spoilsport just closed it :-)

ACuriousMind

@JohnRennie Heh. I gave up looking for duplicates when the first tew hits for escape velocity didn't seem to work, apparently should've looked harder :P

Jasper

I see @ACuriousMind has another new picture. =)

ACuriousMind

"New"? This one's already getting a bit old again! ;)

Jasper

@JohnRennie I am sorry to bother you here, but I remember a long time ago we were discussing Dell Inspiron computers. I was wondering if you heard anything about the fact that many of them have their fans constantly spinning even though the computer is not under heavy load? Searching online tells this is a common problem.

John Rennie

@Jasper Most of the laptops I have are Latitudes, though I do have a couple of Inspirons. I've never had any of mine spin the fans continuously, and I've never heard that this was a common problem.

@Jasper is this something your own laptop is doing?

Jasper

17:08

@JohnRennie No, but it is the main reason I did not buy a Dell Inspiron in the end, because I read too many such negative reviews. Very often, the people with these problems could not solve them even after updating their BIOS and changing their thermal settings.

John Rennie

This is new to me.

Jasper

Anyway, thank you for your advice. Dell does have a fan troubleshooting guide written though, but of course it doesn't always solve the problem.

John Rennie

@Jasper this article?

Jasper

Some people had to return their units a few times for this and other problems. Oh well, maybe big companies have some quality control problems.

@JohnRennie Yes, I read it too! But if you search Dell fan always spinning in google or youtube you will see many examples of what I mean.

John Rennie

@Jasper I'd be cautious about what you find on the Internet. As a rule the many satisfied users don't post on the Internet saying My laptop is working perfectly.

Jasper

17:12

@JohnRennie Hmm OK. Maybe I will give it a try some day.

ACuriousMind

@JohnRennie And absence of bad reviews doesn't tell you anything, either - maybe just no one bought the thing!

John Rennie

@ACuriousMind true :-)

Sir Cumference

17:25

@ACuriousMind Let it be known ACM wants his HNQ answers to be downvoted :P

Avnish Kabaj

18:16

3 hours ago, by Chair

I need a nice title, something related to food. "It's always lunchtime in the hbar" just sounds lame, but something in a similar vein to indicate that we don't want to be too formal is in order.

Challenge accepted

Serving cats a flask of poison, a radioactive source and a gieger counter since 2010

Not very good but I'll be back later

Oh wow h bar and I share birthdays

enumaris

19:12

kachow

first day at SAP :D

ayyy y'alls icons are no longer censored

Anonymous

@enumaris Wohoo!

Anonymous

How is/was it?

enumaris

doing the onboarding thing right now lol

getting all the benefits explained and stuff like that

Anonymous

Yeah, benefits. Those are the things you should get cleared first. :P

Anonymous

Make sure they don't censor your web browsing!

enumaris

19:16

pretty sure I'm just gonna choose Kaiser

seems a lot better than the Aetna options

Anonymous

Do you get free lunch?

enumaris

nope

they provide some drinks and coffee and small stuff like that

Anonymous

Duh...I thought the Germans are more sensible.

Anonymous

@enumaris Not bad. ;)

ACuriousMind

At our German locations, you do get free lunch :P

enumaris

19:20

I can ask them lol, but it seems like no

there's like 10 people here...in an office for like 200 lol

apparently the salespeople don't show up often

dunno if this will change when we move to the new location next month

this stuff seems complicated -.-

still can't connect to outlook hmmm

PM 2Ring

20:06

Grrr. This stuff was recently posted on Astronomy as a question (now deleted). The OP didn't mention he'd already posted it as a Physics answer. physics.stackexchange.com/a/451249/123208

I briefly described Shapiro delay, linking the Wikipedia article & a couple of relevant Physics threads. But it looks like he still doesn't get it.

enumaris

this onboarding is taking longer than 2 hours...-.-

PM 2Ring

I said that despite Shapiro, all local measurements of lightspeed in a vacuum yield c. But he's locked into his belief that gravity causes light's speed to increase as it heads away from Earth.

Jake Rose

21:06

Is Alan gee a troll?

@Blue love the new profile pic

Anonymous

@JakeRose Heh, thanks. Found it on MO. Took some time to understand. :)

Anonymous

Tricolorability

In the mathematical field of knot theory, the tricolorability of a knot is the ability of a knot to be colored with three colors subject to certain rules. Tricolorability is an isotopy invariant, and hence can be used to distinguish between two different (non-isotopic) knots. In particular, since the unknot is not tricolorable, any tricolorable knot is necessarily nontrivial. == Rules of tricolorability == A knot is tricolorable if each strand of the knot diagram can be colored one of three colors, subject to the following rules: 1. At least two colors must be used, and 2. At each crossing, the...

vzn

in theory salon, 34 secs ago, by vzn

Machine learning reveals hidden turtle pattern in quantum fireworks / Uchicago

Jake Rose

21:25

Reminds me of the treyarch logo

still cool as hell

Physics Meta

21:45

0

Q: Is it ok to link my own questions from another SE site?

While I was suspended for low quality questions. I asked astronomy.SE if it would be ok to write some of my low quality questions from here to a higher quality there? They said yes and I did and they did well. Now that a better question exist what can I do with that here? https://astronomy.meta...