The h Bar - 2019-12-18

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2:10 AM

-2

Q: What if in hindsight a Nobel Prize is wrongly awarded (for example, after the concerning theory has been proven wrong)?

I read in an article in the New Scientist (maybe popular, but I think they didn't tell nonsense)that there was much evidence collected by a group of researchers that maybe after all dark energy doesn't exist. See, by example, this video or this article Does anything happens for the winner(s), i...

2:37 AM

Is it just me being too picky or does this edit seem pretty pointless to anyone else? physics.stackexchange.com/posts/150356/revisions It seems like a strange edit to approve to me, especially on a 5 year old question.

2:49 AM

@JMac It's marginal, but it does make the question marginally more readable, so I probably would have approved it as well.

3:42 AM

@JMac i'd have not approved it, but they could be going for physics.stackexchange.com/help/badges/79/archaeologist or other similar badges

2 hours later…

5:38 AM

whoop

Handol got whooped

3 hours later…

8:54 AM

@bolbteppa Riddle me this bob

what is the simplest SUSY rep

Is it the super vector space $\mathbb{R}^2 \times _mathbb{C}^2$?

oops

bad latex

$$\mathbb{R}^2 \times \mathbb{C}^2$$

5 hours later…

1:44 PM

physics.stackexchange.com/a/520290/127931 Is this some sort of cryptic riddle?

Hi

Consider that I have an inclined plane with $\theta=53\text{degrees}$.

There is mass $M$ on the point $A$, and there is a point $B$. The static friction coefficient of that inclined plane is $k=12N/m$.

Point $A$ is higher than Point $B$.

Distance between $A-B$ is $3.6m$.

Direction of the position vector is downward to the inclined plane and direction of the static friction force is upward to thr inclined plane.

So, the work done by the static friction force must be negative. Am I correct?

That was my first question.

My second question is about finding work done by the friction force.

$W_{f}=\int_{A}^{B}\vec{F}_{f}dx=\int_{A}^{B}(k\vec{N})dx=\int_{A}^{B}(kmg\cos{\theta})dx=kmg\cos{\theta}\int_{A}^{B}dx=kmg\cos{\theta}(B-A)$.

Here what should I set $A$ and $B$.

2:10 PM

@AaronStevens they deleted it themselves after I suggested that it wasn't an appropriate topic of discussion and a good strategy would be deleting irrelevant comments and letting the discussion rest

1 hour later…

Novalium Company

3:14 PM

How does google feud have access to more than 5 autocomplete results?

3:29 PM

Fake breaking physics news: Scientists discover that the photon has a half-life of 3.82 million years. The purported daughter product of photon decay is a photon with the exact same polarization, phase, and momentum vector

3:52 PM

@Jim I think it might have been a mod too though. Some of my comments were deleted not by me. They probably agreed with your comment of the conversation getting out of hand (which is why I stopped commenting)

@JMac Use your critical thinking

4:11 PM

0

Q: Why is the name 'propylene oxide' preferred for epoxypropane?

This is the molecule I know as epoxypropane: In my neck of the woods (example), this molecule is used as one of the standard examples of small chiral molecules. The name 'epoxypropane' makes a heck of a lot of sense to me $-$ an epoxy bridge spanning a single bond of what would otherwise be p...

nomenclature hydrocarbons chirality

for the chemists in the room

4:32 PM

@EmilioPisanty no-one in industry uses IUPAC nomenclature.

In my early days I had to try and work out what names like dobs (dodecyl bensene sulphonate) and sles (sodium lauryl ether sulphate) where. The name nspa completely defeated me.

In the unlikely event anyone is interested, this is what nspa means.

5:08 PM

@EmilioPisanty You seem to usually be knowledgeable on SE data (or how to obtain it if it is obtainable). I feel like after a question obtains an accepted answer the question ends up being not as "popular" (like fewer views, votes, etc.). Is this actually the case? Would there be a way to confirm this? It is just a random think I have been wondering for a while, but it isn't a pressing question.

Sorry for the typos on my above message. I am doing many things at once right now :P

1 hour later…

6:18 PM

@AaronStevens most of the data you need for that is available on SEDE

or at least for some of that

'after acceptance, questions get fewer views' is untestable

view data is not recorded

total views are

but view timestamps are not

(to the best of my knowledge)

@EmilioPisanty Got it. Thanks :)

SE seems to feel that that's just too much data

votes, on the other hand, do come with timestamps

however

the timestamp information on votes, as made publicly available on SEDE, is rounded down to the nearest day

as a privacy measure to protect against people tracking down who downvoted them

SE does have that data, but you won't see it

Makes sense

acceptances should have full timestamps, but I can't recall checking

anyways, with those caveats in mind, yes, it should be possible to write a query with that analysis

'on average, threads get less votes once an answer is accepted' should be very testable

... and I'm looking forward to seeing you write that query!

;-)

I'm happy to help if you get stuck, but I have basically no time at all right now

(it feels more like I have negative time tbh, but what can you do)

Ah. This explains why a bunch of old Physics.SE posts got trivial edits yesterday. — PM 2Ring Dec 10 at 9:19

6:25 PM

@EmilioPisanty Oh I feel the same exact way. It really isn't important enough for me to get into all of that at the moment. Thanks for all of the information though.

@PM2Ring Ugh I was noticing that too. I flagged the behavior just in case

Except it was someone else more recently

On SO, questions with accepted answers definitely get less views because the FGITW answerers know they're unlikely to get upvotes. But I think the FGITW effect is less pronounced on Physics.SE.

@PM2Ring Yeah I think that is how I feel. If a question already has an answer then it is less likely I will be able to contribute anything more useful. It is one of my pet peeves on this site when a new answer is posted that doesn't add anything more to what has already been posted.

If it's a popular question, some people will post an answer hoping to pick up a vote or two from the passing traffic. I don't have enough rep to see deleted Physics answers, but on SO the high scoring questions often have a huge number of low quality deleted answers, many of them literally duplicate code from existing answers, with no accompanying text (or very little).

There was a question about that a month or two ago on MSO: meta.stackoverflow.com/q/390907/4014959

6:40 PM

@PM2Ring Yeah that sounds frustrating. I have seen that happen here too, but not that bad.

Some people just don't get the idea that Stack Exchange sites aren't discussion forums, and they want to add their 2 cents to the discussion.

@PM2Ring Yeah, makes sense. I sometimes have to refrain from making a snide remark when I see a new answer that doesn't say anything different from an answer I have already posted. There are specific users that are worse than others with "copying" answers too, I have noticed :)

On a related note, I wish that more people made an effort to look for dupes before writing an answer, especially when they themself have answered a very similar question in the past...

@PM2Ring Ah yes definitely. I try to do my best to avoid doing that, although I probably am not perfect at it. I think there have been some times where I convinced my self the question was not a duplicate when it really was :P

OTOH, I do sympathise when someone sees a decent question they can answer, and in the enthusiasm to write an answer they neglect to do a dupe search.

6:54 PM

It is especially annoying though when it is a question that has most likely been asked before

Yeah that's true

@PM2Ring In this case, the person making the edits almost definitely has made many edits since winter bash started, so it doesn't appear to me to be an attempt at getting a WB hat.

However, if you find yourself copying images & large slabs of text from your old answers, you probably need to consider that maybe the new question could be a dupe. ;)

@PM2Ring I definitely feel like there are a lot of "potential energy" dupes out there, but the variations in the questions are just large enough to not make them exactly duplicates.

Questions about lifting an object, the work being done, the change in potentia lenergy, etc.

@JMac Oh, ok.

@AaronStevens Very true. And it depends on the knowledge level of the OP.

@PM2Ring Not to imply it's anything malicious either. I just recognize the user as someone who has been making a lot of edits lately, so I assume it's just their regular behaviour, not an attempt to get a WB hat.

7:00 PM

@JMac Or maybe they were practicing for when WB came around

To get those hats

@AaronStevens I mean I think they've already earned the hat since WB started, so they likely aren't doing it for the hat. As Kyle mentioned last night though, they might be doing it for the badges.

@JMac Badges are why I get up in the morning

@JMac Maybe they were doing it for the rep. But it looks like they're on a "holiday" for a little while.

@AaronStevens I've never put effort towards them really. Some of them are cool; like I enjoy getting tag badges; but for the most part I don't really try for them. For example, the Electorate badge, it took me over a week to get cast those ~6 votes on questions I needed for the badge, even though I could have gone and searched for questions easy enough.

Bam, cranked out another tech radar article on large language models...now I am not sure what my current task is...hmmm...

7:09 PM

@JMac Yeah, I understand. I used to somewhat be conscious of the badges the site automatically said I should go for. But now I am at the point to where they are so far out of reach it doesn't matter.

I suppose an easy one I could get is something about asking enough well-accepted questions, but I don't have any physics questions that Physics SE would be useful for at the moment

@AaronStevens My problem with asking questions is that I typically know how to find the information I would be asking about anyways. It doesn't help that I don't actually do much physics anymore except for random little personal calculations, and obviously thinking about questions here. If I were studying something I might be able to come up with good questions; but right now I basically just come up blank.

@JMac Yeah that is understandable. I have been thinking about formulating a question about the Heisenberg Uncertainty Principle, as I feel like it is loosely thrown around on this site without much understanding behind what it actually says (thanks to a lot of pop-sci sources), but I haven't had the time to really put the question together and to make sure it isn't already explained in some other question that has already been posted

But I feel like there is so much misinformation, and it makes me feel like I don't really understand it either.

@AaronStevens Speaking of which, physics.stackexchange.com/questions/520183/…

@AaronStevens Yeah, if I were to ask about something it would probably be related to relativity or QM, because I don't know them well at all, so it's not like an easy google search to figure out what I'm missing. On the other hand, I know so little about those topics that if I tried to ask a question with my current understanding, it would be a poor question (and I haven't studied them enough to really have any questions I want to ask anyways).

@PM2Ring Yep, that is the most recent culprit! I made a comment, but I am unsure if it is actually correct :P

I feel like Semoi's comments are not a correct use of the HUP.

So here is the fast and loose version of my question...

The HUP can be derived from the axioms of QM without making an references to "disturbing the system", etc. The derivation doesn't come out of how one measures a system (or what the system is), but it does tell you a characteristic guaranteed to exist in the statistics of your measurements of the system

that $\Delta x\Delta p$ cannot be smaller than some value

However, there are "derivations" of the HUP specifically dealing with measuring the position/momentum of electrons using photons

And you can arrive at the HUP in that way (I believe you can anyway)

7:26 PM

@AaronStevens CC @JMac got you covered

26

Q: How I learned to stop worrying and start asking questions

As has been noted in the past, particularly in Question self-destruction: why don't experts ask more questions? and in Does reputation correlate with the question-to-answer ratio?, and also here, this site has the peculiarity that, in overwhelming proportion, our 'expert' users, by multiple measu...

discussion questions

So then it makes it seem like the HUP is related to the measurement... so I am wondering if this is just a "self-consistency thing"... or if it is just a huge coincidence. A coincidence like how you can derive the Schwarzschild radius of a black hole by setting the escape velocity in Newtonian gravity to be equal to the speed of light

@EmilioPisanty When my available time switches to positive I will take a look (as I gain more time debt by chatting here)

indeed

I think I just get annoyed with descriptions of the HUP of "If you measure the position of a particle then you no longer know its momentum because of uncertainty". Which I think can be correct as long as you qualify what you mean by it. But certainly the pop-sci version of that statement is not correct (I think)

@AaronStevens after a while you don't even notice badges anymore. I got a new gold badge a few weeks ago and was like "Oh, yeah I guess. Didn't expect to get that one. What else is going on though". I assume the same is true about rep. Does @JohnRennie even notice if he gets a new viral answer? I assume he hits close to the cap every day anyway

@EmilioPisanty I've read that one before, and there were quite a few good bases to cover. I've been tempted to do some self Q&A's about some fairly common misconceptions; but there's typically already a question that covers it well for the types of questions I come up with. Part of the issue is that I just have a bachelors in mechanical engineering. I'm not much of an "expert" on most topics. Most of the stuff I have a good grip on is pretty basic and often already well covered.

7:31 PM

@JMac fair enough

@Jim I thought the cap just got adjusted to what @JohnRennie gets each day. Isn't it built into the system that no user can get more rep than him each day?

@AaronStevens that might be a new feature. I know I've never gotten more than him in a day though. Couple times I went over 200 and he still got more

Turns out I beat him last May 25 when he lost over 500 rep from one user being removed. Think I got 0 that day. Last I checked, 0>-500

@Jim Wow... You would think at that point they wouldn't remove rep for that

@AaronStevens Ya, I would hate that to happen to me, but proportionally, it's like if they removed 5 rep from me. Whatever. Maybe they look at the percent

Anyone want to help point out a dumb math mistake I am probably making?

Nevermind, I think I know why I am wrong

Which brings me to a question actually...

So normally by the fundamental theorem of calculus we have $$\frac{\text d}{\text dt}\int_0^tf(\tau)\,\text d\tau=f(t)$$

However, what if we have $$\frac{\text d}{\text dt}\int_0^tf(t,\tau)\,\text d\tau$$

How does one do the derivative with respect to t in this case?

7:57 PM

@Jim That user must have just been below the threshold for "substantial". I also lost 30 points that day from a user removal; which is probably pretty close to John losing 500 points, proportionally.

must have

Leibniz integral rule

In calculus, Leibniz's rule for differentiation under the integral sign, named after Gottfried Leibniz, states that for an integral of the form ∫ a ( x ) b ( x ) f ( x , t ) d t , {\displaystyle \int _{a(x)}^{b(x)}f(x,t)\,dt,} where − ∞ < a ( x...

I think I found it

8:08 PM

Unfortunately going this route has not helped me solve the problem I was gong for. oh well

Novalium Company

8:28 PM

YEAH

8:45 PM

@Jim Generally, votes from users with "many" votes (I don't know the numbers here as they aren't known to anyone but the CM team) are not removed upon deletion unless they have been involved with voting fraud. So e.g. if a user is being deleted because they upvoted their own sockpuppet, the votes will be removed regardless of the overall impact.

9:16 PM

phys.org/news/2019-12-newton-elusive-three-body-problem.html

Ugh...

What is "regular math"?

@AaronStevens What did they even really do? "While the researchers stress that their findings do not represent an exact solution to the three-body problem..." Then it would be nice if your article actually explained why this is special and give us some clue on what they actually did. This article is basically "if you have any idea what we're talking about, then this is useless information.". Classic phys.org.

> Instead of accepting the systems' chaotic behavior as an obstacle, the researchers used traditional mathematics to predict the planets' movements. "When we compared our predictions to computer-generated models of their actual movements, we found a high degree of accuracy," shared Stone.

Are their "computer-generated models" not using "traditional mathematics"???

That website is also urging me to turn off my adblocker if I want to continue receiving their high-quality science journalism.

I'm...gonna leave it on.

@ACuriousMind Right? I didn't know that the three body problem involved some sort of exotic numerical methods which somehow defy "traditional" math. And yeah, I opened it on a broswer without adblocker. I love when most of the page is ads with a bit of relevant text sprinkled in.

I guess three-body math isn't traditional. Traditional math is between a man and a woman.

3

I also like their summary of Newton's laws

Too bad those laws do not contain Newtonian gravity in them

@ACuriousMind Also can't stop laughing

9:32 PM

@AaronStevens Who the hell are they even writing these for? Who would be that interested in science to care about solutions to the 3 body problem, but also not be familiar with Newton's laws? It just seems so weird.

@JMac They are probably trying to attract new readers by talking about a "three body problem"

hence ACM's comment lol

I like how the title and the second to last paragraph are essentially saying different things

The more I look at it the sillier it becomes

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