The h Bar

12:48 AM

@Obliv/ @William yes "interpretations" can be a 4-letter "dirty word" around here. but agree with you both that its quite meaningful and actually very substantial work has been done by greats who concur. (bell/ bohm/ 't hooft et al) much more here vzn1.wordpress.com/category/physics & feel free to drop by this room sometime/ anytime for deeper inquiry/ analysis... a small cyber-QUODS =)

theory salon

theoretical computer science. highlight reel vzn1.wordpress.co...

@BernardMeurer a very advanced area/ very active research... what algorithm(s) are you using?

0celo7

1:16 AM

0

Q: Geodesics in geodesic balls

It is well-known that in a geodesic ball containing points $p$ and $q$, the radial geodesic between them is the unique minimizing curve. I'm trying to follow the proof of this given in Cheeger & Ebin (AMS Chelsea edition, page 8). They seem to take a slightly different approach than usual. Let $...

Bernard Meurer

@vzn For face detection I'm using cascade classifiers

for nose approximation I'm using a guess that has been working well

@0celo7 Halp nao?

0celo7

@BernardMeurer let's skype

I'm doing things

Bernard Meurer

@0celo7 I'll call you in a sec

0celo7

@skillpatrol my dumbass roommate left lemonade out

holy god there's a billion of them now

@BernardMeurer well?

vzn

1:56 AM

@BernardMeurer like this? en.wikipedia.org/wiki/Cascading_classifiers (article seems not that great) ... sounds like a good blog topic :)

Bernard Meurer

@vzn Yep Viola Jones algorithm

My blog or yours? I can't fix links on mine so I've left it aside for now

user218912

fuck it math is too difficult i'm gonna do physics ._.

0celo7

lol

what changed your mind

user218912

reading that orbifolds book.

0celo7

well it's a hard book

user218912

2:12 AM

@0celo7 my mind changes every few hours so don't mind me.

user218912

I can go from definitely wanting to study physics to every field in science in a week.

vzn

@BernardMeurer what language are you writing it in? are you using any libraries?

Bernard Meurer

@vzn C++ 11 with OpenCV

vzn

@BernardMeurer not too familiar but it apparently already has facerec built in!

Bernard Meurer

2:28 AM

@vzn It's awesome!

vzn

@BernardMeurer does it have viola-jones built in?

Bernard Meurer

Yep, you just need the cascade files

which I found on the internet

and it had a Python wrapper if you're lazy

vzn

are the cascade files in c++?

its the algorithm?

Bernard Meurer

Cascades are in XML

@vzn github.com/opencv/opencv/blob/master/data/haarcascades/…

vzn

2:50 AM

@BernardMeurer it would be cool to compare the viola jones algo with the built in one for accuracy, wonder what the builtin version uses

Sir Cumference

This is one of the worst (best) things I've ever seen

Bernard Meurer

@vzn Builtin on OpenCV you mean?

The default OCV algo is Viola Jones

vzn

@BernardMeurer uh but thought you had to install files for that, so how is it then default?

Bernard Meurer

They distribute some Cascades with OpenCV

you can train your own or download some if you want

for specific features like nose and so on

vzn

@BernardMeurer cool stuff man are you gonna customize it somehow

(half here, my young cohort is asking me to look up magic the gathering stuff, eg ps4/ps3 game etc)

jyotishraj thoudam

3:09 AM

anyone online?

-2

Q: Constancy of the speed of light in the hypotenuse of the triangle in the Michelson and Morley experiment

In Michelson and Morley experiment, Michelson calculated that the total time traveled by light with respect to the stationary observer standing at ether field was $2L/c$. Here, Michelson followed the Galilean Theory of relativity, i.e., since light was travelling not a vertical path but a lon...

special-relativity experimental-physics speed-of-light galilean-relativity aether

could some clear my doubts?

user116211

Hey @vzn, have you thought about the next AMA?

jyotishraj thoudam

MAFIA, could you help me understand with the question ?

vzn

@MAFIA36790 yeah DS is up & says hes ready (alas kinda scarce lately) but @DavidZ hasnt gotten back to me yet on timing (thx for interest)

btw how do you think the last one went?

Bernard Meurer

@vzn I already am customizing it :)

I'm adding some logic so I don't have false positives

@jyotishrajthoudam You asked your question, your answers shall come in time (or not) don't go asking people to answer your question

jyotishraj thoudam

@berna

thats very helpful

thats so kind of you

Bernard Meurer

3:28 AM

@jyotishrajthoudam I'm not trying to be kind. I'm trying to show you how to abide by chat guidelines.

vzn

@BernardMeurer it will be impressive if you can improve accuracy in any way, plz update on that... actually theoretically any accuracy improvement would nearly be a scientific advance...

Bernard Meurer

@vzn Well, I had this idea for false positive filtering, but it's barely anything yet...

vzn

@BernardMeurer usually published algos are highly tuned & not easy to improve on...

jyotishraj thoudam

ok

Bernard Meurer

It's not the algo I'm messing with, it's where the algo is being run

where in the image that is

jyotishraj thoudam

3:31 AM

I thought I could ask question.

vzn

@BernardMeurer oh yeah face location so to speak, probably lots of other algorithms for that, its common in cameras now...

jyotishraj thoudam

But Is there any chance you could help me in some way? @Ber

0celo7

@BernardMeurer Better album art?

Bernard Meurer

@0celo7 IV by badbadnotgood

0celo7

No, I mean I changed mine

Bernard Meurer

3:32 AM

@jyotishrajthoudam Not a physicist, sorry. @0celo7 Help him out

I'm not a physicist

@0celo7 What's that?

diamonds

@vzn Yeah, but I'm only using magic numbers, no extra detection

0celo7

"What a Time to be Alive"

"Diamonds Dancing" is pretty godly

Top 20 song

jyotishraj thoudam

3:34 AM

@0celo7 I kinda need some help from you. If you have some minute to spare, maybe we could discuss something?

0celo7

depends what it is

@BernardMeurer this sphere cover is so bool

The only issue is that the cover has nothing to do with Riem. geo.

Bernard Meurer

@0celo7 It really is

@0celo7 Not good

jyotishraj thoudam

@0celo7 Its this physics.stackexchange.com/questions/269246/…

user116211

@vzn Of course; I was excited and equally interested from the very moment DavidZ put forward the idea ;)

user116211

@vzn Well, beyond my scope to judge; but yeh more new users than the first session; and as well, I love @yuggib. Came to know he has some interest in writing a book; well maybe when he is sorta Emeritus Prof ;))

jyotishraj thoudam

3:48 AM

Mafia mind helping me out?

user116211

@jyotishrajthoudam sorry, kinda busy; but you can leave your query; any interested one would help you.

jyotishraj thoudam

Its Ok.

Thanks. I'll wait for someone

vzn

@MAFIA36790 everyone here is welcome to give feedback. "over my head" could be feedback :) ... do you have a physics degree?

what did he say about a book? missed that

user116211

4:18 AM

@vzn I'm about to enter college this fall; either undergraduate in maths or physics but I'm inclined in the latter. Letters to come yet.

user116211

Jul 12 at 16:31, by MAFIA36790

Have you considered writing any book?

user116211

Jul 12 at 16:32, by yuggib

@MAFIA36790 It would be nice, but also very time consuming. I think I have a good expertise on some topic where a nice overview is missing (the classical limit of quantum theories of course)

user116211

Jul 12 at 16:33, by yuggib

but it would take a huge amount of time and effort to collect everything in a book

user116211

Jul 12 at 16:33, by yuggib

maybe when I am older... ;-P

user116211

Morning @johnR.

John Rennie

4:29 AM

Morning :-)

@jyotishrajthoudam what did you want to ask?

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

Top of the morning :-)

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

4:41 AM

Well, it looks like the Russians lost their appeal on the doping ban.

Shing

4:58 AM

@DavidZ Thanks for the help and hint, I figure it out how the trick works! It is quite smart to take the advantage of the addition law of power to simulate the rolling dice.

jyotishraj thoudam

5:09 AM

-2

Q: Constancy of the speed of light in the hypotenuse of the triangle in the Michelson and Morley experiment

In Michelson and Morley experiment, Michelson calculated that the total time traveled by light with respect to the stationary observer standing at ether field was $2L/c$. Here, Michelson followed the Galilean Theory of relativity, i.e., since light was travelling not a vertical path but a lon...

special-relativity experimental-physics speed-of-light galilean-relativity aether

John Rennie

@jyotishrajthoudam I'm not sure I understand what you are asking.

The light travels at $c$ with respect to the ether.

So if the ether is moving with respect to the Earth that changes the speed of light with respect to the Earth.

jyotishraj thoudam

Since the earth is moving horizontally with velocity "u" with respect to the ether, the speed of light in the vertical direction as seen from the ether should change right?

@JohnRennie Consider this, if the earth was still, the speed of light in the y-axis as seen from the ether would be "c". But as the earth is moving with "u" in the x-axis, the light as seen from the ether would be going in a longer line, with different speed.

John Rennie

5:26 AM

Yes. That's exactly what Potier and Lorentz calculated. That's the calculation described in the Wikipedia article.

Oh hang on, no.

The speed of light as seen by someone stationary wrt the ether is always $c$.

So the speed of light as seen by someone on the Earth changes.

Potier and Lorentz calculated the changed speed as seen from the Earth.

jyotishraj thoudam

5:44 AM

So, what you're telling me is that "The speed of light as seen by someone stationary with respect to the ether even if the light was inside a moving earth frame"?

@JohnRennie

John Rennie

"The speed of light as seen by someone stationary with respect to the ether is $c$ even if the light was inside a moving earth frame"

Look at it this way. Suppose you are floting in a river rushing along at some velocity $u$.

The speed of sound in water is a constant, $v$, so if you're floating stationary wrt the water you'll always measure the speed of sound to be $v$.

Someone standing on the bank will measure the speed of sound to be different to $v$ because the water is moving wrt the bank.

jyotishraj thoudam

so, that someone standing in the bank is the observer standing in the stationary ether. so wouldn't he measure the speed of light a bit different from c? Since, in case of sound the person standing at the bank would measure the speed of sound different?

@JohnRennie

John Rennie

6:04 AM

@jyotishrajthoudam someone standing in the bank is the observer standing in the stationary ether - no, the water/ether is moving relative to the bank. The person standing on the bank is moving relative to the water/ether.

But you're correct that the person on the bank will measure the speed of sound to be different.

The point is that if you're moving relative to the ether you measure the speed of light to be different from $c$.

And if the ether is flowing past the Earth then observers on Earth are moving wrt the ether and therefore will measure the speed of light to be different to $c$.

jyotishraj thoudam

@JohnRennie What I understand so far is this... Light as seen by the person on the stationary ether will be constant regardless of the motion of the motion of the source and regardless of the motion of the earth because light travels in all 360 degrees at constant speed "c".

John Rennie

@jyotishrajthoudam by the person on the stationary ether - does this mean an observer stationary with respect to the ether?

jyotishraj thoudam

yes

John Rennie

In that case the answer is yes - someone stationary wrt the ether always measures the speed of light to be $c$ regardless of whatever speed the source of the light was moving at. Just like the speed of sound in water.

jyotishraj thoudam

So, when earth moves away from its original position and since light is traveling in all direction in the ether field, light in the direction of the moved mirror hits the mirror in the vertical direction, in the michelson and morley experiment.

@JohnRennie

John Rennie

6:19 AM

Let's go back to the analogy of the river.

If send a pulse of sound out exactly normal to the bank then when it reflects back to you it will have been swept downstream a bit, so you won't get the echo. If you want to get the echo you have to angle the sound slightly upstream.

jyotishraj thoudam

Ok

John Rennie

And this is the same in the MM experiment. The lateral arm isn't excatly at right angles to the flow of the ether otherwise it wouldn't get the light back.

However the angle it deviates is so small that it couldn't be measured, so we normally just assume it's normal to the flow.

jyotishraj thoudam

So, the earth moving in space would be like a boat travelling downstream faster than the river flow?

and the stationary observer in the ether field is a person in floating in the river going with the same speed as the river?

John Rennie

Yes, that's a reasonable analogy

Hmm, good question!

0

Q: Does gravity cause the gravity of another mass to curve?

For example say star 1 is at position x, however star 2 causes gravitational lensing on star 1's light that is traveling toward you and you now see star 1 at position y. Will star 1's gravity move you toward position x or y? Please use layman terms

general-relativity gravity spacetime gravitational-lensing

My immediate response is yes, though I'm not sure how to go about proving it.

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

6:50 AM

I believe it's unreasonable to ask for "layman terms."

John Duffield

7:32 AM

The answer is no. You can work it out by imagining a big cannonball in a rubber sheet, with a big depression representing the gravitational field. The light from the big cannonball passes by a small cannonball which puts a little dimple in the slope, and bends to reach your eye. But you're a long way from the small cannonball. It doesn't affect your local slope. You fall towards the big cannonball regardless of the fact that the light from it was bent by the small cannonball.

@jyotishrajthoudam : don't forget the wave nature of matter. In the river analogy, it's like you're made out of sound waves. If you're made out of sound, you always measure the speed of sound to be the same. See the other meaning of special relativity by Robert Close.

David Z

8:05 AM

@vzn I didn't know there was anything to get back to you about. I haven't seen any pings or other contact from you.

DanielSank

9:10 AM

Any mods around?

I has question about comments.

David Z

@DanielSank for the moment

DanielSank

groovy

The comment close reasons involve rudeness, not being constructive, obsolescence, and a few others.

Nowhere is there anything about being... misleading.

David Z

You can't close comments... I guess you mean flag reasons?

DanielSank

Yeah that.

How would you advise a well-meaning Physics.SE user to deal with comments that, in strong, confident language, tell the OP something really misleading?

David Z

And there's no "misleading" flag reason because being misleading (or wrong) is not a reason a comment should be flagged.

DanielSank

9:14 AM

^ Ok right

But what to do then?

Danu

@DanielSank Why not just tell them?

DanielSank

@Danu I'm getting to that.

Can't type fast enough.

In some cases it's easy enough to just point out why the comment is wrong, but this requires the comment to actually make an identifiable false claim, and it requires me to either write another comment or make the (large) investment of writing a good answer.

However, long back-and-forths in the comments is discouraged and often removed, so even "just telling them" seems to fail.

Let me show you why I'm bringing this up again:

David Z

@DanielSank this could be considered a way to get the comment deleted ;-)

DanielSank

@DavidZ You don't really mean that though, do you?

David Z

Yes, I do... why wouldn't I?

It's somewhat indirect, but if you have the patience, it does work.

DanielSank

9:17 AM

@DavidZ You're saying I should try to start a back-and-forth in the comments section to get attention and have everything removed? :\

Danu

That's like... gaming the system though

DanielSank

^ That

And it sounds laborious for me and the mod who has to run cleanup.

See here

1

Q: Why are the electric and nuclear forces which hold an atom or molecule together insufficient to cause decoherence during an experiment?

My understanding is that anything that qualifies as an "observation" or "measurement" will cause the "fuzziness" of the superposition to disappear to the local observer, and the results of said experiment will appear in the classical form that we are intuitively used to. So let's take the double...

quantum-mechanics double-slit-experiment decoherence

David Z

I'm not saying you should, but I'm saying you can if you want to. It's not laborious for the mods; we can move the whole thing to chat with about 3 clicks. (Heck, the system even gives you a prompt to move it to chat without mod intervention at some point.)

Danu

So what should one do

David Z

Anyway, here's something else to consider: comments are meant for suggesting improvements, requesting clarification, and (to some extent) linking to related resources. Anything that doesn't fall under those categories could be considered not constructive, and you could probably flag it as such.

DanielSank

9:20 AM

@DavidZ I see.

Is that spelled out somewhere?

Danu

@DavidZ But this leaves one with no way to counter bad content

David Z

I'm not sure. I think it probably is, somewhere, but I don't know where.

@Danu I've just given two methods: respond, or flag as not constructive (if that applies)

Or there's a third method: wait a week and flag it as obsolete.

@DanielSank we're already looking into that issue.

DanielSank

@DavidZ I see.

I suppose I'm mostly concerned with the ill effects imparted on the curious but less well informed users who are met with misinformation posed so confidently. Then again, I suppose this isn't quite a classroom site.

Thanks for looking into that comment thread.

hi, @Danu.

David Z

@DanielSank just doing my "job"

@DanielSank that's understandable. The thing is, if people can pose misinformation so confidently, other people can also pose the right information confidently. That's why responding is the normal recommended course of action to misleading comments.

Danu

@DavidZ But you just told us that such kind of comments would probably be "not constructive"

(and hence flaggable)

David Z

9:31 AM

Right. The recommended normal course of action is to respond; the recommended backup course of action (when you don't want to respond) is to flag.

These are very weak recommendations, of course; it's not like anybody is going to check whether you tried responding before you cast a flag.

Danu

To flag a comment/answer for being misleading? You just told us not to, right.

I guess the bottom line is that there is nothing to do against misleading comments, and misleading answers can only be downvoted

lucas

11:00 AM

@ACuriousMind Hi :-)

ACuriousMind

mornin'

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

hi

ACuriousMind

@MAFIA36790 Did you even read the question before voting to close here? You VTC'd as "homework-like", but the question is not asking us to solve the quoted problem (it even says the asker has worked them out already). The question is unclear, in my opinion, but certainly not off-topic as homework-like. Not every question that quotes an exercise text is off-topic as homework-like.

user116211

11:16 AM

Well, my mistake, I read it; the last line was really vogue; so yeh, mistake though; but of course, if it is closed, which I'm sure, then the reason would be unclear .... Would remember to scrutinize minutely in the future reviews.

Physics Meta

0

Q: Do we need a canonical question linking photons and light beams?

It seems to me that we get lots of questions from people baffled about the way light behaves given that it's made up of photons. For the latest example see: How does a photon 'know' when to reflect in case of refraction? Do we need a canonical Q/A explaining the relationship between light beams...

discussion

user116211

Is this you @lucas who stars ACM's greeting every-time ;P

gebra

If you really want to discuss this you could ask in the chat, but do you really care that much? — John Rennie 3 mins ago

woops

If you really want to discuss this you could ask in the chat, but do you really care that much? — John Rennie 4 mins ago

lucas

@MAFIA36790 Although this is a secret and personal stuff, but yes I am ;-)

John Rennie

Is the statement If it accelerates, it produces gravitational waves correct? I would have thought not.

gebra

11:21 AM

1

Q: Why are there so many 'crackpots' doing research in physics these days?

I have seen countless instances such as these, where 'crackpots' seem to spend their entire lives trying and failing to promote incorrect physics. Where do these people come from? How come there are so many who all seem equally convinced about their field changing 'theories'? Most importantly, ho...

research-level physics-careers

user116211

@lucas ah! secret, yes ;P

John Rennie

@gebra Hi.

ACuriousMind

Stars were actually not secret until certain bugs/features were fixed, cf. this meta.SE thread.

John Rennie

Are you really interested in understanding the mentality of crackpots? Many years experience would suggest it's an unrewarding field to study!

lemon

I personally find them fascinating creatures, having conversed with several in the past.

gebra

11:24 AM

i don't know. Call me naive but how likely is it to end up being one if you pursue a career in physics?

John Rennie

@gebra The vast majority of crackpots did not formally study physics, or if they did they flunked out along the way.

lemon

They seem to be little more than conspiracy theorists who happen to latch to physics rather than, say, 9/11.

John Rennie

Indeed. It's a common symptom of the syndrome that they believe physicists are conspiring to supress the truth.

ACuriousMind

@JohnRennie I think that it is a rewarding field of study for psychologists. Understanding how the human mind latches onto believing things and how/why it holds onto them does strike me as interesting. I don't believe that physics crackpots are much different from other delusional people in that respect, though

gebra

oh aha

but is some poor soul responsible for checking through all of their work? how do you know if something is worth reading then

lemon

11:29 AM

gebra, crackpots almost never get their work past peer-review. So if you stick to respectable journals then it's unlikely you will ever come across their work.

John Rennie

@gebra no. You ignore their work unless it has been published in a peer reviewed journal.

lemon

The way I'm exposed to their ideas is primarily through mass emails that they send to anyone with a publicly-available academic email address.

Usually claiming that some recent major discovery is actually a lie. Oh, and while they're at it, black holes don't exist.

John Rennie

@lemon Stephen Crothers where are you now? :-)

gebra

I was under the impression that these were people trying and failing to get phds..?

John Rennie

@gebra no, they are typically outside the academic establishment.

gebra

11:33 AM

ok

that's odd

lemon

Also, the overwhelming majority of academics work on very esoteric problems, whereas crackpots are drawn towards extremely broad problems - usually revolutionising all of physics with high school level algebra.

John Rennie

They generally feel that if something is incomprehensible that must mean it's wrong, as opposed to just being complicated and requiring a lot of work to learn.

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

crank

crackpot theory

ACuriousMind

11:50 AM

...why are you posting Wikipedia links explaining what crackpots are?

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

...I'm trying to educate :-)

lucas

@ACuriousMind Why the star has gone? I didn't cancel it!!!

ACuriousMind

Either a moderator or a room owner removed it, then.

Jim

12:07 PM

I just showed up to work. Let me say that being presented with a conversation about crackpots in physics is probably one of the best ways I've ever started my day. Thank you everybody!

user116211

@Jim If you want to really start your day with genuine crackpot questions, start your day opening YahOO or Quora. You'll be amazed!

Jim

@MAFIA36790 not crackpot questions. Good lord, that would be annoying. But talking about crackpots and where they come from. That is deliciously entertaining

@lemon you're talking about Gabor Fekete, aren't you

user116211

ah!

gebra

@MAFIA much thank

user116211

A recent user at PSE came claiming black holes don't exist.

gebra

12:12 PM

@Jim actually

user116211

That SR is hoax is quite famous among the crackpots.

Jim

Please, show of hands if you get emails from Gabor

lucas

Don't shy, mention me as next example :-( @MAFIA36790

0celo7

@ACuriousMind figure out the spinors yet?

user116211

@lucas Well, you don't actually throw crackpot question (till now)... your phase is like you are quite confused taking the transition; this happens to many one when they begin SR. So, I'm not counting you; crackpots are different. They believe in conspiracy theories and all that.

ACuriousMind

12:17 PM

@0celo7 Well, I found the abstract statements that I need, now I just have to prove them or hunt for references that actually prove them

0celo7

No time for balls I assume :(

gebra

@lemon

i guess that's true

that it's generally impossible to make modern breakthroughs solely using very primitive techniques..

lucas

I cannot imagine how one can ridicule the others while he/she has a great quote in his/her profile!!! "There will come a day, when all the lies will collapse under their own weight, & truth will again triumph."

0celo7

GUCCI MANE NEW ALBUM

gebra

i've noticed most of them are really long and tiring but nowhere complex

Jim

12:20 PM

rapiddiffusion.com/science/crackpots-bane-science

lucas

@MAFIA36790 I forgot to ping you in my previous comment. I meant you :-(

user116211

@lucas I'm not ridiculing anyone.

lemon

@Jim The one and only! You hear from him too? I actually tried to have a reasonable exchange with him once but it resulted in my inbox being flooded.

Jim

@lemon yes, he will do that if anyone responds. Gabor is a unique entity. He actually sifted through all of the university databases of over 84 countries and added the emails of all listed physics professors, pdfs, and grad students to his mailing list. He updates this periodically too.

That, good sir, is the definition of commitment and dedication

skill patrol

Wow! So thorough?

Jim

12:35 PM

yes

0celo7

Good god

What's a pdf

Post doc fellow

how do you know??

lucky guess ;-)

I read up on him. Apparently, many people in physics have been spammed by him and patterns have emerged. Plus he published a list of people who had read his paper as well as a list of countries he was contacting. 84 countries, thousands of physicists

additionally, the only way he could have gotten my email was through the university website. Since I was a new grad student at the time with a profile buried deep in the site, it stands to reason that he must have dug thoroughly through the database

0celo7

12:40 PM

What if he's right?

Jim

read his papers. He isn't right

The following is directly taken from one of his last emails to me:

> The Hungarian physicist Gabor Feket&#101 demonstrated that the modern physics is a full pseudo-science in hundred percent degree and he described with eight digit accuracy the electromagnetic physics of photons, X-ray-photons, gamma-photons, muons, electrons and all atoms, thus solving all the problems in particle and nuclear physics. He also gave a new interpretation for the full spectrum of the hydrogen and described the strengthening points of all photons in the hydrogen atom.

user116211

@Jim He thinks himself GOD ;/

ACuriousMind

Do I want to know what "strengthening points of photons" are?

Jim

@ACuriousMind If you don't know what that is, then you're obviously too clouded by the pseudo-science of modern physics to ever come to the light side

ACuriousMind

Damn. Back to suppressing the truth, then

Jim

12:46 PM

@MAFIA36790 Don't be silly, God could never be good enough to solve all problems to 8 digit accuracy

user116211

@Jim ah! point noted.

0celo7

@ACuriousMind Geodesic balls eye twitch

ACuriousMind

@0celo7 I have no idea what that means

0celo7

@ACuriousMind please just take a look at math.stackexchange.com/questions/1867093/…

ACuriousMind

@0celo7 It...looks like a nice question?

I'd suspect a typo, too, but I have no idea about geodesic balls and their curves at all

0celo7

12:51 PM

@ACuriousMind But you read Mi...oh screw it

What did you do in your Riemannian geometry course?

ACuriousMind

@0celo7 This, but I don't remember it all because I didn't find it very interesting :P

0celo7

You monster

gebra

https://www.youtube.com/watch?v=rcSykqN7-FM
Ah, but he has not considered the 'upward causality cone'

David Z

1:26 PM

@Danu sorry, I missed this earlier. Yes, I said don't flag a comment for being misleading. But the comment may be flaggable for other reasons, and you can certainly cast a flag for those. You shouldn't avoid flagging comments because they're misleading, either. I suspect that most of the comments of the type we're talking about are also not constructive.

So in summary, my recommendations are: (1) respond to point out the wrong information if you can productively do so; (2) if not, flag the comment as not constructive if it is not constructive (and remember, any comment that's not trying to improve the question could arguably be considered not constructive); (3) otherwise, wait a week and flag it as obsolete.

Danu

1:52 PM

@DavidZ I'm talking mostly about comments where people "explain" something to the OP (so superficially they're constructive) but actually are teaching them stuff that is wrong/very speculative

skill patrol

2:11 PM

Policing the comments sections would be a monumental task!

Danu

@JohnRennie No, don't think so. The power radiated is proportional to the third time derivative (to some power)

0celo7

2:31 PM

@Danu Would you happen to know of any Morse Theory books besides Milnor

Perhaps one with some...details

Danu

Nicolaescu; Audin & Damian

The latter is more about Floer Homology

but it does a brief run-through AFAIK

0celo7

What is Floer homology?

vzn

2:51 PM

Jul 13 at 21:58, by vzn

@DavidZ/ @JohnRennie et al thx for your effort re moderating the guest session and don't want to overthink that too much right now unless more volunteers show up... think that nearly-random or laughable stuff may inevitably show up in transcript & think its fine to throw out worst offender stuff. DZ are you ok with another scheduled session in 4wk? should we have more discussion on fmt etc?

David Z

@Danu yeah, I know. I'd say those can be considered not constructive, because they're not trying to improve the post.

vzn

@DavidZ how about jul26 standard mtg and then aug9 @DanielSank? ok w you? he says hes up for it

David Z

Any chance Daniel would be available to do it this coming Tuesday?

vzn

@DavidZ alas he says he needs substantial prep time & he hasnt said a lot about aug9 yet, hes been less active lately (with good reason! a newlywed!). plus, good to have some lead time for mounting publicity

David Z

In that case I suspect the following session on August 23 would be better

I think we may have other plans on the 9th

skill patrol

2:58 PM

There should be no need for "substantial prep time" for an informal ask me anything chat, no?

vzn

@DavidZ ok sounds good/ fine with me thx. @DanielSank DZ is saying Aug23 plz write up a meta post with that date asap thx

@skillpatrol (leaned toward same pov myself.) there was a long dialog about this in chat with DS emphasizing nec of/ preferring lead/ prep time. think it can vary with different guests.

skill patrol

Ok

vzn

@DavidZ (et al!) did you have any other thoughts/ feedback re last session? did read transcripts during/ aftwerwards, (saw the dialog re quieting newbie or fringe question(s) etc)

David Z

@skillpatrol It's always up to the speaker. I think Daniel has to check some NDAs or something.

@vzn Not that I remember

Sorry I didn't see your original message, by the way.

vzn

@DavidZ yeah he actually said he has done something that awhile back (looked into speaking guidelines etc) but maybe will add something more etc

skill patrol

3:06 PM

Perhaps adding a "C" for "Chat." AMAC Ask Me Anything Chat

vzn

@DavidZ np maybe pings are not reliable in here or you got busy that day. its all good am ok with the pace/ outcomes right now (eg think it was a small coup that Neumaier showed up for last one). seems sometimes late summer tends to slow down in cyberspace/ everywhere etc

David Z

I have been busy, but I'd still say I notice the majority of pings. Yours just slipped through the cracks, I guess.

vzn

@DavidZ & would still like to get you in a slot at some pt, maybe when other spkers not available or you think good timing etc

David Z

I'll keep that in mind

vzn

@skillpatrol yeah its a different fmt isnt it, nothing quite like it anywhere else™/ terra incognita =D

skill patrol

3:09 PM

:D

A Mac

David Z

By the way, a tip if you want to ping me: write your message so that it's clear from the first ~30 characters that it's something that needs my attention. I see the pings in the SE inbox but if it doesn't look like something that I need to respond to, I'm less likely to read the full message.

5

vzn

@DavidZ ok good advice wlil do that. anyway though generally do not ping you myself except re key stuff to coord the spker series

John Duffield

@Jim hey Jim: as you are to Gabor Fekete, so am I to you. ;)

skill patrol

What do you mean? @JohnDuffield

vzn

@skillpatrol did you make either of the 1st two sessions? what did you think?

skill patrol

3:15 PM

They were fun to watch @vzn

vzn

@skillpatrol =) yeah glad you think so, kind of the main raison d'etre... think its time to write colorful blog post on it all after DS announces his talk

whats new w you? are you in school? what major?

@gebra maybe your question might fly on meta better. or maybe not lol. have studied this some. physics is a very high profile field and has many big popsci heroes who still make front page of sci magazines & even tabloids (einstein, feynman etc). it has the staggering $1M nobel prize awarded nearly yearly, basically most prestigious prize in all of science. so crackpots are the "shadow side". there are other aspects etc.

John Duffield

@skillpatrol : come on, get your thinking cap on!

0celo7

@JohnDuffield good one

John Duffield

3:40 PM

@0celo7 : tsk. I've been looking at some of his answers, and Jim is pretty level headed. I must have been thinking of somebody else.

@Jim : I take it back. Humble apologies.

William Bulmer

Hi all

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

Hi again.

0celo7

Whoa @Semiclassical ???

Semiclassical

yes?

0celo7

wrong chat

Sᴋᴜʟʟ ᴘᴇᴛʀᴏʟ

3:43 PM

welcome

:-)

John Duffield

@WilliamBulmer : were you talking about energy the other day?

William Bulmer

@JohnDuffield I was. I was trying to someone whose name eludes me (...obliv?) with the concept

and momentum

He was having difficulty with the idea that you could have either without rest mass

*trying to help

I've noticed that I tend to miss whole words when I type lately. I guess I must be getting old in my 34 years of age

Jim

@JohnDuffield no worries. Water under the bridge

John Duffield

@WilliamBulmer : scalars and vectors apart, IMHO it's wrong to separate energy and momentum. It's better to talk of energy-momentum. You can't reduce the kinetic energy of a cannonball without reducing its momentum. Ditto for a photon, wherein E=hf and p=hf/c. You divide by c to go from one to the other.

William Bulmer

Also, I apologize if I stepped on anyone's toes with my strong opinions on the presentation of math yesterday. I'll try to keep those things to myself.

@JohnDuffield Yeah, I know. I actually mentioned that to obliv yesterday--that they are unified in both SR and QM, but that's a more advanced concept

@JohnDuffield don't want to pile on too many ideas at once. I figure she/he needs to get use to the concept of non-matter being able to carry momentum/energy in the first place

@JohnDuffield I haven't had much of a chance to read arxiv.org/pdf/1508.06478v1.pdf yet

John Duffield

3:55 PM

@WilliamBulmer : that's what waves do. Take all the energy-momentum out of a wave and the wave isn't there any more. That's what I was saying in this answer.

William Bulmer

@JohnDuffield Right. Also, I think that people are more comfortable with the idea that waves have energy, since the idea of light being "energy" pervades our society

John Duffield

@WilliamBulmer : it's just the photon in the mirror box. When you catch a massless photon in a mirror-box it increases the mass of the system. When you open the box it's a radiating body that loses mass, just like Einstein's E=mc² paper. Note Einstein's last line: "radiation conveys inertia between the emitting and absorbing bodies" Light has a non-zero "inertial mass". That's a measure of energy.

John Rennie

Cool stuff about black holes:

cam.ac.uk/research/news/…

theory salon

Transcript for