« first day (1618 days earlier)      last day (3305 days later) » 

12:20 AM
@ACuriousMind Wait...
That's an indefinite integral...
 
@0celo7 Sigh...you can also use $\int_a^x f' = f(x) - f(a)$ and make a similar argument
 
@ACuriousMind :,( you sighed at me
 
@0celo7 It wasn't even in italics ;P
 
@ACuriousMind My brain has mushified.
 
@0celo7 It happens^^
 
1:21 AM
@ACuriousMind The VTC queue is empty...
 
Well, good^^
 
hey guys
is there any way that we can automatically close questions that start with could dark matter/energy be
 
1:41 AM
@Jimmy360 No, there might be an interesting one.
 
maybe one day
 
The correct answer to the question would seem like a crackpot theory today.
 
1:54 AM
@0celo7 0celo7: "My inner crackpot says that since E=m, dark energy = dark matter."
quick publish before it's too late
 
XD according to @0celo7 , E = mc
 
please don't kill us.
 
My inner crackpot also says that quantum mechanics is BS.
 
don't worry it's all in the interpretation of it.
 
He also says that the black hole information paradox is trivial -- information is not conserved.
@ACuriousMind I BEAT LUBOS
Only 173rd for all-time rep though
 
2:10 AM
@0celo7 Hi
 
@ᴇʏᴇs Hi
 
@Jimmy360 Well c=1, so that's okay ;)
 
@KyleKanos I was 8 orders of magnitude off though :D
 
:D Sometimes, but he used SI. @KyleKanos
 
2:32 AM
@0celo7 Hmm, well why didn't you use natural units then? You'd not need to worry about powers of c and get the right answer ;)
 
@KyleKanos I'll do that on the AP tests
I'll cite Dr. Kanos :D
 
2:53 AM
Gah..stupid = vs +=
 
On the AP tests just leave the Scanton blank and say "We once thought that Newton was right. Maybe modern physics is wrong."
 
3:13 AM
@Jimmy360 Explain exactly what part of AP Physics is modern?
 
3:24 AM
XD
fair enough
 
4:00 AM
Would a question about the spectral response of rust, similar to my question here opendata.stackexchange.com/questions/4936/… be on topic here?
 
yes
chemistry SE might also help
 
yes, I have asked them as well
 
Did you cross post?
 
no, I have that post on open data, but are not a member here or at chem yet
and a question I make here (or chem) will take a considerably different angle to the one on open data
@StanShunpike i meant, I asked on their chat
as it would be on topic here, I'll get into writing the question (after, of course, I read the Tour page)
 
4:43 AM
@santiago makes sense. I do the same thing. Its good to ask before spending time writing a question that might get downvoted. It also means I learn what questions are appropriate ans write better ones.
 
exactly, I make a point of reading the tour page and look at some of the questions before I dive in
 
 
1 hour later…
5:50 AM
Facepalm:
It is not an answer, but another question. They will delete your this answer, but it is not because they are evil (they are), but here you can write exclusively answers. — peterh 22 mins ago
What else are people supposed to write in an "Answer"?
 
 
1 hour later…
7:10 AM
hello!
 
7:25 AM
hi
does anyone know what roe is in matlab? roe - that p shape symbol
 
7:56 AM
@usukidoll you mean rho?
Rho (/ˈroʊ/; uppercase Ρ, lowercase ρ or ϱ; Greek: ῥῶ) is the 17th letter of the Greek alphabet. In the system of Greek numerals, it has a value of 100. It is derived from Phoenician letter res . Its uppercase form is not to be confused with the Latin letter P, although both are typeset using the same glyph. == Uses == === Greek === Rho is classed as a liquid consonant (together with lambda and sometimes the nasals mu and nu), which has important implications for morphology. In both Ancient and Modern Greek, it represents a trilled or tapped r. In polytonic orthography a rho at the beginning of a...
 
8:37 AM
0
Q: How do I recycle my earlier question which is flagged?

user6760Earlier I posted a question which is flagged as it is inappropriate and I could not delete it due to answered. Now I changed both the title and content see link below, my question is since the new question is entirely different from the original flagged question is this recycling of question allo...

 
 
1 hour later…
9:57 AM
@ACuriousMind I got a response from Davy Jones.
@ACuriousMind It's...unsatisfactory.
 
 
1 hour later…
11:11 AM
hmmm I am wondering if I should delete my question here physics.stackexchange.com/questions/175231/… and repost it on chem.se
 
11:28 AM
ah, I just flagged it for migration
 
 
2 hours later…
1:19 PM
@0celo7 't Hooft replied??
 
1:35 PM
@Icosahedron Yes.
 
1:55 PM
0
Q: How active is research on non-relativistic quantum mechanics?

user119264Is are topics in non-relativistic quantum mechanics an active/relevant research field? For instance, is any form of SUSY quantum mechanics used in places like CERN, Fermilab etc?

list question? too broad? primarily opinion-based?
 
I saw that and thought it was opinion based
 
@Qmechanic I think the latter of the three
 
Why so? I don't think it's that bad. Maybe it is more of a meta Physics question?
 
It'd be better asked here in chat than on the main
 
2:10 PM
To the mod who facilitated my iron rust question migration to chem - thank you for the speedy response :)
 
2:55 PM
@santiago : You're welcome.
 
 
2 hours later…
4:27 PM
0
Q: How should I ask a question to understand the answer I will get?

CalmariusI'm very curious and like to understand physical concepts. So I search the internet and ask questions on the site. But there is a problem: my understanding isn't complete about the subject sometimes I don't even know what concepts I need to look up. The internet is running low on easy to under...

 
4:40 PM
@0celo7 And? What did he say?
 
@ACuriousMind I'll share that when I'm not in a lecture.
That came out wrong. I'll just post it when I get home.
 
No rush^^
 
5:27 PM
20 first post reviews in a day, for the second day running :D
:: Feeling Victorious ::
 
In contrast, exhausting my close votes every day does not make me feel victorious :(
2
 
Haha :)
 
@TheDarkSide Still some distance to go though ;)
 
I don't have the heart to VTC well-phrased homework-like questions.
 
@KyleKanos Some day! But its been like a race, both me and peterh chiefly are hunting for it these days. (Except for he's way above :P)
 
5:37 PM
@0celo7 Well, you don't have to. It's your vote.
 
While most others hunt for rep, I hunt for first post reviewing :P
 
@ACuriousMind Milord, you own my votes.
 
@ACuriousMind - How does this work? When I flag something as a duplicate (or likewise) during FP, does it enter your VTC review section?
 
@TheDarkSide Like every flag, it should enter the review queue. I don't think the fact that it's cast during a FP review changes anything.
 
@TheDarkSide FP?
 
5:44 PM
@0celo7 First Post
 
Ohhh
 
@0celo7 Yup.
 
@ACuriousMind When you say "high rep users", what's the lower cutoff?
 
@ACuriousMind Good to realize I'm not increasing your workload :P
 
@0celo7 Depends on the context, but generally I'd associate "high-rep" with >10k
 
5:48 PM
I tend to say high-rep with the intention of >3k (i.e., those with close votes)
 
That's just a show of power! (both of you)
rep = 2 > rep = 1 and hence higher rep.
 
@TheDarkSide Hah, you shouldn't worry about that. All participation here is voluntary, remember? :)
 
7:31 PM
@0celo7 what is the most fundamental definition of force in classical mechanics?
 
F = mA
 
no.
 
@Icosahedron Written as $F := \frac{\mathrm{d}p}{\mathrm{d}t}$, this is indeed the most basic definition of force, imo.
 
@ACuriousMind is there anything more fundamental than that? not exactly basic
 
What do you mean by "fundamental"?
 
7:38 PM
I don't know? most rigorous or general i guess?
 
What's not general or rigorous about force being the time-derivative of momentum?
 
though can it be generalized even further?
 
I don't know what you would generalize it to. For conservative forces, you might also choose force as the gradient of the potential.
But forces act on objects, and objects have momenta, so I don't know what would be more general
 
is there any way of proving that $F = ma$ without proving that $ma = - \nabla V $ ?
 
Using which defintion of $F$ and $V$?
 
7:49 PM
3
 
What do you mean by that?
 
@Icosahedron I mean, if you want to prove $F=ma$, then you need to have defined $F$ another way. If you define $F$ as $-\nabla V$, then it is obvious that you dont get $F=ma$ without $-\nabla V =ma$.
So I ask you what way you want to define $F$, if you want to choose neither $ma$ nor $-\nabla V$.
 
For a spring you can show the relation found here: pasteboard.co/2t5wytOI.png
Is there any other way of doing that?
 
$ma = -\nabla V$ is really just the Euler-Lagrange equation of motion (in "actual" coordinates").
So, it's rather that you can have $ma = -\nabla V$ without ever even defining "force" at all
 
@ACuriousMind Yes that answers my question, thanks.
 
8:06 PM
@Icosahedron: how do you measure force?
 
8:30 PM
@Marcel is that a rhetorical question?
 
@Icosahedron: depends on wheter or not you know the answer
 
@Marcel what are you trying to say?
 
force is "measured" due to an observer seeing a displacement of a system
therefore F:=ma is the inherent definition of force
 
are you implying that it is not fundamental?
 
actually anything you give reason to, depends on the fact that one is able to somehow seperate two "different things" in space and time
 
8:38 PM
@Icosahedron What does fundamental even mean?
 
@ACuriousMind Who knows? I've been using that word in different context a lot.
 
@Icosahedron If you don't know the definition of the word, why (possibly also how) are you using it?
 
I do know the definition.
Though I'm misusing it due to lack of more appropriate terms.
 
Then why did you say, Who knows, which necessarily implies that you also do not know
 
Who knows
 
8:45 PM
good one :)
 
@Icosahedron Perhaps the derivative of the Lagrangian wrt. the generalized coord
 
@0celo7 That's $\nabla V$, only in fancy speak.
 
agreed
 
Is the Lagrangian not more fundamental than the potential?
 
@0celo7 What is the Lagrangian if not "kinetic energy - potentials"?
 
8:50 PM
actually you can get the euler-lagrange equations for Lagrangians from $F=ma$ with d'Alamberts principle
 
@ACuriousMind Is that the only definition?
 
Can you not alter the definition of the lagrangian?
 
By adding arbitrary gauges that cancel
 
@Marcel Which principle is that?
 
well, in the end they'd cancel
 
8:51 PM
@0celo7 Oh, well, otherwise you go to an axiomatic treatment where you start with "A theory is defined by giving a Lagrangian..."
 
D'Alembert's principle, also known as the Lagrange–d'Alembert principle, is a statement of the fundamental classical laws of motion. It is named after its discoverer, the French physicist and mathematician Jean le Rond d'Alembert. It is the dynamic analogue to the principle of virtual work for applied forces in a static system and in fact is more general than Hamilton's principle, avoiding restriction to holonomic systems. A holonomic constraint depends only on the coordinates and time. It does not depend on the velocities. If the negative terms in accelerations are recognized as inertial forces...
 
Is axiomatization the best construction of any theory?
 
@ACuriousMind My initial answer would have been F=ma, but then I saw he didn't like that. I'm simply offering an alternative.
 
But the only way to talk about the Lagrangian as something other than "thingy which gives the correct equations of motion" is to derive it from Newtonian mechanics (by d'Alembert, as Marcel says), and then $L = T - V$.
@Icosahedron Define best.
 
@ACuriousMind I didn't know that I was a dictionary today.
 
8:55 PM
Well you keep choosing to use arbitrary words to try defining things
 
@Icosahedron I'm mainly doing this (saying "Define X") because I don't think there's a "best" or "most fundamental" way of doing physics. There's "abstract" and "hands-on", but even full theoretician that I am, I wouldn't say that abstract or axiomatic is always the best thing to do. It depends on what you want to do with the theory
 
I tried to ask whether or not axiomatization is the most consistent way to construct a theory considering the godel incompleteness theorems.
For example can physics be constructed in the same way as euclid's axioms? (or hilberts axioms)
 
usually physics is not deductive. but one can try to get some axioms and test them by deduceing a result which can then be compared with experimental data
 
@Icosahedron No, there is no full axiomatization of physics
 
@ACuriousMind: of quantum physics ;)
 
8:59 PM
This is Hilbert's sixth problem, by the way.
 
What does "full axiomatization" mean?
 
@0celo7 I'd say: A set of axioms (and logical rules) from which the outcome of every possible experiment can be in principle deduced in a rigorous fashion.
 
@ACuriousMind It cannot exist?
 
@Icosahedron Uh, I have no idea whether it can exist, but it has hitherto not been found.
 
@ACuriousMind Tell us when you've found it.
:|
 
9:11 PM
Oh, full axiomatization of all of physics?
 
0
Q: Refreshing your question

BenichiwaIs there a way to make your question pop back up in the front/top again, so that more people see it? I get upset because if your question is not answered in the first second it will never get answered.

 
10:15 PM
Additionally, most Stack Exchange sites still don't require registration for asking questions. Only the ones where much of the incoming questions were very low quality and that have requested it do (5 out of ~140, physics being one of the 5). — Oded ♦ 9 hours ago
Interesting.
Is there evidence that the amount of low quality questions here dropped after we made that change?
 
10:34 PM
@ACuriousMind: I think this can be answered one a physical basis though physics.stackexchange.com/questions/175396/…
e.g maybe someone knows half-life times for usual nuclear fallout
and the difference between "dirty" and "clean" bombs
 
Sure you need physics to answer it, but it's not actually about physics, in my opinion. YMMV, of course.
 
I'd say nuclear bombs are too much high-tech to be called engineering stuff. or why is it off-topic?
 
Well, I'd there's no conceptual question here - it's essentially a homework-like problem: Look up what is in the typical fallout of a nuclear bomb, look up the half-lives and the "safe" level of radiation for humans, compute the time when radiation has dropped below that.
 
well this would appy to something like this too. learn GR and apply it to your problem
essentially every question can be answered like this. learn stuff and apply it
 
10:50 PM
Learning GR would consist of more than just looking up numbers. I'm not against clueless questions, I'm against questions asking for computations without any insight.
 
@Marcel As a future nuclear engineer, I don't know how to feel about that statement.
 
about which?
 
The one I referenced. (You on mobile?)
 
ah, no. just didn't know about that referencing feature
 
It's surprisingly difficult to realize it's there :D
 
10:53 PM
@0celo7: hm. well. I'd call you a physicist :)
 
But you don't want to miss it once you've discovered it ;)
@0celo7 I don't say anything about the truth or falsity of the statement, but I sure hope you don't go into nuclear engineering to work on nuclear bombs :P
 
@Marcel Just because engineers don't need to know what insert random math concept here, doesn't mean their work isn't incredibly complex.
@ACuriousMind I picked a school with an excellent nuclear fusion program.
 
@0celo7 exactly
 
well. I didn't say that
 
@Marcel You said it's "too high tech" to be engineering.
 
10:57 PM
@0celo7 Ah, you'll blow us all up in the pursuit of energy for all, then :)
 
yeah, that saying, it still call it experimental physicist stuff
 
@ACuriousMind My friends joke that I'll get my nuts irradiated.
 
nothing wrong with experimental physics :)
 
@ACuriousMind It's physics related and not profoundly off-topic but not particularly interesting (to me). In my not so humble opinion, the question should be left open in case someone else finds it interesting. If no one does, it will simply wither on the vine.
 
@0celo7 Well, I don't know what to say to that :D
 
11:00 PM
@0celo7 LOL
 
@AlfredCentauri I don't have any close votes left, anyway, and I'll not come back to close it since I also don't feel strongly about it.
 
@ACuriousMind yep, there are more deserving targets of your close vote sabre.
 
@ACuriousMind I left a comment with a link for you.
 
@0celo7 Welp, that's disappointing.
 
What's your interpretation of it?
I left that as a comment because it has my email on it.
 
11:08 PM
@0celo7 Thought so. I'd say "stretching" then was one of the worst word choices possible, and that I still don't really know what the heck he wants to tell us with that paragraph.
 
@ACuriousMind Exactly...I also don't see what nonlinearity has to do with anything.
I thought the whole point is that nonlinear field theory has some pathological behavior that string theory somehow magically avoids.
 
Just goes to show that not every word in notes and textbooks is as carefully pondered as we would wish ;)
 
Should I copy-paste this and accept the answer?
 
Hm, good question. It would be the answer somewhat by definition, but I wouldn't accept that if it came from anyone other than the guy who wrote the text to be explained.
But since it essentially means there can't be a better answer, I guess it is the answer that should be posted and accepted.
Totally unrelated: Why the heck has math.SE a tag for limits-without-l'Hospital? That'd be like electromagnetics-without-integrals. You can do that, but why on earth would you?
 
@ACuriousMind GOTCHA
"Why the heck has math.SE a tag for limits-without-l'Hospital?" is German sentence structure!!
Warum hat...?
Your English is not perfect!!
 
11:18 PM
Arrrgh...this damned do/does :D
 
@ACuriousMind I don't think AP Calculus AB covers medical limits.
(AB is the lower of the two calculi usually taught at high schools in the USA.)
 
Heh... "medical limits"
 
@ACuriousMind I thought Davy Jones was pretty good too.
 
I only now realized that you were making a pun on Dutchman....
Well, lol :D
 
I can be punny too :D
@ACuriousMind My first thought was to call him Michael Jordan.
Get it? (It's an American thing.)
 
11:26 PM
@0celo7 No, I don't get it. Isn't Micheal Jordan a basketballer or something?
 
@ACuriousMind Michael Jordan --> Jordans --> Nike --> Foot Locker --> locker --> Davy Jones' locker --> Davy Jones --> Flying Dutchman --> Danu --> go back --> Flying Dutchman --> Gerard 't Hooft
 
@0celo7 Hahaha :D
 
@ACuriousMind Again!! The correct term is basketball player.
 
@0celo7 I guess the mixed German/English conversation I had with a psychologist today about information theory must've broken me :/
 
lol
Do you know anything about spin bundles and spinors in curved space?
 
11:33 PM
Not really. I'm taking a seminar on QFT in curved space this semester, but as of yet, I know nothing substantial about it
 
@ACuriousMind So the stuff in part two of the appendix to chapter 9 in Straumann is foreign to you?
 
@0celo7 I think I know the content of 9.5.1, but, unsurprisingly, not of 9.5.2
 
I worked out everything in 9.5.1 already.
I get some of the stuff in 9.5.2, but I'm not all the way through Nakahara's chapter on connections on bundles.
Hopefully that will help me.
 
I must say that I've no really mathematical view of connections on bundles, just what I needed for dealing with two-dimensional gauge theory, so I'm probably lacking some "important" theorems
 
11:50 PM
What do we have here? 20 pages on spin structures in Jost...
My reading list is ridiculous.
 
That's nothing new ;)
 
Once I finish Nakahara I have a list of topics to round off.
@ACuriousMind I deleted a whole bunch of books the other day.
Sadly, that didn't help much.
 
Why would you delete them? I just have an ever-growing folder of "Stuff to read" :D
 
I deleted them off my iPad.
Hi FBI!
 
Probably in the literal sense :P
lol, ninja edit
 
11:54 PM
Sadly, yes.
I hate pirating.
But I really have no alternative, as I don't have access to a university library yet.
 
::shrug:: Just be happy to be alive in the age of the internet ;)
Totally unrelated: I didn't know there was a German Language until I saw this in the HNQ.
...great, the parsing of [german.SE] makes that sentence sound weird.
 

« first day (1618 days earlier)      last day (3305 days later) »