The h Bar - 2015-02-26 (page 4 of 6)

« first day (1575 days earlier) ← previous day next day → last day (3361 days later) »

4:00 PM

Back now

Jimdalf the Grey

it takes a couple of minutes for the main page to properly recognize the existence of a new question

sometimes they flit in and out of existence in the meantime

4:21 PM

There is almost no snow on the ground (less than 1 inch) here on campus, yet they closed the university for the day (originally to open at noon)

Jimdalf the Grey

@KyleKanos You serious!? What a wussy campus

I'm in South Carolina

They don't understand "snow" down here

Jimdalf the Grey

What's not to understand? It's cold, wet, and slippery

Our campus won't close until we get a meter of snowfall in half a day, and sometimes not even then

My son reflected on the snow last week (when the public schools were closed, though the Uni wasn't), saying something to the effect of, "We live in where there isn't snow, but we have a lot of snow now"

(he's 5)

Hi all.

Jimdalf the Grey

4:27 PM

hi Dr. Nick!

There really wasn't any accumulated snow when he stated this. It had snowed maybe about 0.5 inches

Does anybody know a software to capture a trajectory from a video?

Jimdalf the Grey

::faints::

@mikeonly pasco.com/blogs/physics/capstone-video-analysis.cfm

@JimdalftheGrey I know. But note that he was raised in SC (while the waifu & I in NJ) where we literally went 3 full years without snow (all of those whilst the boy was alive)

@KyleKanos Thanks!

Jimdalf the Grey

4:29 PM

@KyleKanos Meanwhile I'm used to seeing snowdrifts taller than me

I haven't seen real snow in about two years :(

I am not sure that what I've seen counts as snow

Jimdalf the Grey

but you've seen fake snow?

I'll upload a pic real quick

@JimdalftheGrey Well, there was one day where the water that fell from the sky was frozen, but it melted as soon as it touched the ground. That's kinda fake snow indeed.

Jimdalf the Grey

4:32 PM

not snow at all

Then I simply haven't seen snow in two years

Is anyone else concerned that the best references that John Rennie's answer to energy conservation in GR has are two blogs, namely Philip Gibbs' and Lubos Motl's?

Jimdalf the Grey

I was concerned that he linked to viXra

And the other two guys also cite a blog

Jimdalf the Grey

I'm also concerned that he cast Philip Gibbs and L.M. as having equally valid opinions

Are there no frigging established papers on this, or have the "professional" people just decided that that question is essentially nitpicky and uninteresting?

4:34 PM

Well both have PhDs, no?

@KyleKanos Yeah, but one has basically declared war on science by opening the "used toilet paper repository", remember?

Jimdalf the Grey

Everyone knows energy conservation isn't a law globally. Only conservation of the stress-energy-momentum tensor is a law

@JimdalftheGrey Right, that's what I thought, too

So what the heck are Lubos and Philip disagreeing about?

And why does John think that this is a legitimate debate?

Though Gibbs still publishes on arxiv: arxiv.org/find/all/1/au:+Gibbs_Philip/0/1/0/all/0/1

Jimdalf the Grey

Lubos is saying what we say. Philip is saying something weird

@KyleKanos because he knows better than to use his creation for serious works

but that question is definitely a dupe. There are a hundred questions asking how expansion and energy conservation get jiggy with it. All closed as dupes

4:38 PM

@JimdalftheGrey I posted a link yesterday where he stated that explicitly

Also, four people "answer" the question and nobody edits the body? Arrrgh!

11

A: Hubble's law and conservation of energy

Update 1: I edited the answer a little to make it more accessible. Update 2: Based on the discussion with Sklivvz I'll elaborate a bit more why the concept of conservation of energy is problematic in General Relativity. First one has to note that conservation of some quantity means that the q...

I think this is probably the best answer we have for this question

Jimdalf the Grey

-2

A: Is the accelerated expansion of the universe consistent with conservation of energy?

This energy comes from God!This is something difficult to explain like the derivation of the Big Bang explosion!THis is how we prove that God exists!

::headdesk::

@ACuriousMind what's the "used toilet paper repository"??

@glance viXra

As so eloquently described by Jimeese

@ACuriousMind I found that, but I'd never heard of it. How does it differ from the arXiv?

4:49 PM

@glance No endorsement, and thus it's full of crackpots

You're lucky if what you find there is in TeX, and even then, it's mostly garbage

Jimdalf the Grey

@glance viXra is truly arXiv backwards

2

@ACuriousMind Hey! That's not even close to being the most popular. Let's cut that out right now

@JimdalftheGrey Way to point out an error by using a lie though

@JimdalftheGrey Sorry, JimNoSperm

@glance: E.g: Best. Abstract. Ever

Jimdalf the Grey

@ACuriousMind Once again, I should stop saying things

@ACuriousMind hahahahaha that's awesome!

4:52 PM

Or: Genetic memory nonsense, classified as quantum physics

It's basically this over and over again, though most stuff is less funny and more incomprehensible, or simply wrong

@ACuriousMind "As a software designer of medical devices(...)" well that explains a lot of things

@glance I didn't look into the paper, it simply couldn't get better after that abstract

@JimdalftheGrey Nooo, your snark must be spoken loud and clear

Jimdalf the Grey

Everything, including photons, seems to be decelerating

@ACuriousMind I was searching for some hidden gems. In the second paragraph he states his background, which explains everything else I think

Jimdalf the Grey

First article under cosmology

4:56 PM

@ACuriousMind that's what too much playing Assassin's Creed produces

@glance Lol, 0celo7 said basically the same thing

I fear AC is scientifically more accurate, though

::shudder::

@JimdalftheGrey Ah. That explains everything!

ROFL abstract yes !!!!! watafak

Jimdalf the Grey

So, then there's this obvious one. I read the first sentence and a half of the abstract and could not contain my laughter: Falsification of Einstein Theory of Relativity

ϒ was fraudulently smuggled into SR without mathematical proof applying it to relative velocities which gives wrong results.

user image

@JimdalftheGrey (in vector notation) now that was a useful parenthesis

Damn, now I'm reading viXra again :D

Jimdalf the Grey

5:02 PM

I wish viXra had a comment section so that I could make high school children cry with "This is all garbage and BS and you're garbage and BS for not seeing how stupid it is"

@JimdalftheGrey I'm not sure if I should tell you, but it has a comment section

Jimdalf the Grey

:D

It's right there under the article pages

Its still snowing

The things that appear in the title when you open the pdfs are really funny

Many have just "Microsoft Word" there, but this one has "Java Based Distributed Learning Platform": vixra.org/abs/1412.0040

And it's so much gibberish that I wonder if that was actually an attempt at automatically generating a paper

Jimdalf the Grey

5:05 PM

I want to leave a single comment. "I hope one day in the future when you actually go out and learn what relativity is that you think back to this moment and this paper and you feel ashamed that you were so utterly wrong and blinded by pride"

@JimdalftheGrey "You are equally welcome to be positive or negative about any paper but please be polite. If you are being critical you must mention at least one specific error, otherwise your comment will be deleted as unhelpful."

Jimdalf the Grey

damn

@ACuriousMind that's what snarXiv is for

that's clever

Specific errors are hard to find in these things

Jimdalf the Grey

General errors, that's another thing

@ACuriousMind Ah, I just knew someone was talking about me :-)

5:08 PM

@JohnRennie :O Are you psychic or something?

I was just about to leave a comment asking for better references

Jimdalf the Grey

psychic is close to physic

I suspect busy general relativists are too busy to argue about boring questions that have been thrashed out a million times.

I think you're being unfair to Phil Gibbs though.

He started Vixra because he felt that Arxiv was being unfairly restrictive on who is allowed to post.

@JohnRennie That's a noble cause, but it's obviously gone horribly wrong, hasn't it?

My view is that he is wrong and the arxiv management are right, but Phil's motives were pure and he is a respected physicist.

Just not especially well respected by Lubos :-)

@JohnRennie This is true. But he also readily admits that (a) it has a higher percentage of crank work and (b) that if you want your work accepted by the mainstream, his repository is not the place for it

Jimdalf the Grey

5:10 PM

@JohnRennie I have no objections with his motives and I think it's a tragedy that his creation has been so warped and twisted. But good intentions are not enough to vindicate Frankenstein's monster

Yes, I agree with you both. Vixra is a cesspool.

Though I think Phil Gibbs still believes there may be gems floating amidst all the ordure.

Does Lubos have some sort of feud with him? I had not heard of this.

Jimdalf the Grey

21 hours ago, by Jimdalf the Grey

@Sofia viXra is an online repository, like arXiv, but they have no standards for accepting submissions, and so they have become the standard place where people with crackpot theories and awful science/math/etc post garbage papers. I'm sure not all papers are garbage on their own, but a delicious piece of chocolate cake, when found among garbage, becomes garbage

Well, Lubos has a feud with half the world, so that's not saying much

@JohnRennie I think he does believe that as well. And it's not really an irrational thought (if you have 5000+ items on record, a handful of them might actually be useful).

5:13 PM

@StanShunpike Hi Stan. I don't think so. They differ on this particular issue, but I don't think there is any animosity. The only person Lubos really seems contemptuous of is Peter Woit.

And I can understand his reasons though I don't necessarily sympathise with them.

Jimdalf the Grey

@JohnRennie Really? But there's so many other people to hold in contempt as well!

Everyone who knows Lubos personally reports that he's a really nice guy. I wouldn't judge from his online antics.

I speak as one who has never met him, though he has been quite kind about some of my worst offences against physics on this site.

What I actually came to chat for was to moan that I'm out of close votes. It's been a busy day! :-)

@JohnRennie Ha. We've been saying the same thing!

It seems no one has any votes left

Cripes, that doesn't bode well for the next few hours!

@JohnRennie Me too

5:17 PM

Is there some known reason to dislike Peter Woit? Lubos always seems helpful when I've read his posts. He doesn't seem like a guy who would be arbitrary about who he dislikes.

@StanShunpike It think Woit, um, "dislikes" String Theory, and therefore, Lubos "dislikes" Woit, basically, though it might also be more personal

@StanShunpike He feels that Peter Woit is critical of string theory when he doesn't understand it well enough to make a valid judgement of it.

And I have some sympathy with this.

Ah. Well, that could be said for a lot of people lol

Peter Woit is vastly more skilled at physics than I will ever be, but he's never going to trouble the upper echelons of the theoretical physics world.

Woit feels he is in a sound position to judge the current string theory programme, while Motl feels he is not and is doing harm to a valuable area of science.

My guess, an one ideally positioned to judge neither, that the truth lies somewhere in between.

As an analogy, when ACuriousmind criticises my answers on QM I take this as an opportunity to learn more (just don't do it too often OK :-)

But when some spotty 13 year old who knows b*****r all about QN criticises my answers that makes me angry. I suspect Motl sees Woit as the ignorant 13 year old.

Is Lubos considered part of the upper echelons of theoretical physics?

5:23 PM

He is now retired from physics, but yes he was up there with the best of them.

@JohnRennie Oh, I don't think I've done that too often, have I? (I really only recall one or two nitpicks :) )

@ACuriousMind :-)

Qmechanic criticised my concept of centre of angle. Just because he's correct is NO EXCUSE! :-)

But he's 41, isn't that a bit early to retire? I mean, you wouldn't see LeBron James hang up his sneakers in his prime. I'm surprised he's retired so young.

massey.ac.nz/~rmclachl/overthehill.html

@StanShunpike When you start as an eager young academic working stupid hours on hard problems is great because it's just so much fun.

But as time goes by you want to get into roles where you have a team of fanatical young scientists to order around.

And ultimately end up as a head of department. Generally, as scientists get older they focus more on planning and strategy and less on active research.

sigh. I had a good comment response going and the answer on which I was commenting got deleted. Oh well

5:30 PM

But there are only a small number of senior academic posts, and getting them is as much about politics and schmoozing people as raw talent.

If you are a genius, but without stunning interpersonal skills, then there comes a time when you have to decide. Are you happy with endless postdocs or junior staff positions,

or is it time to pack your bags and leave academia. I think Motl chose the latter.

@KyleKanos What can I say. An answerer on the same thread just told me he hasn't time to play with me :(

@ACuriousMind I don't think we're talking the same thread. I was talking about the Snow-fall Frozen one

@KyleKanos What was the question? I was composing a truly awesome reply to a question about the recent 12 billion solar mass black hole when the OP deleted it. Very annoying.

@KyleKanos Interesting. Sorry, then, I can't read time stamps (facepalm)

Someone said it was rude for me to have posted the automatically generated "This is a comment..." because the OP CLEARLY wrote that was a comment and I didn't need to go reminding everyone

5:34 PM

@JohnRennie Well, if you have the answer already halfway (or more) done, why not ask the question yourself?

@JohnRennie It was an answer someone else posted that I was going to comment on, not a question

@ACuriousMind facepalm lol

The rep limitation on posting comments is there for a good reason, but I do sometimes feel it's harsh on enthusiastic newcomers.

@JohnRennie Why not vote to undelete it? It's actually an interesting question

For 10k+ rep, this is the link: physics.stackexchange.com/questions/167250/…

Uh, why did OP delete that? Did he think John's comment somehow meant that was a stupid question?

5:36 PM

Aha, yes, I have voted to undelete. But I suspect too few of us will see it to amass the required undelete votes.

@ACuriousMind I hope my comment didn't come across that way. It wasn't meant to.

How many are needed? I thought it was 3

It is done.

Well, we can't close the bad stuff anymore, but we can keep the good stuff :)

@dmckee - we need more close votes!

Or more active reviewers

@JohnRennie Do you mean that you need more close votes for each active high-rep user, or more people engaged?

5:40 PM

I'll answer the black hole question, but then I must go. I have to finish reading Shift by Hugh Howey for a reading group on Saturday morning. Life is all just work, work, work!

Ah ... I see you just answered that.

There was a suggestion of that kind on the mother meta once. Popular but not implemented as I recall.

@JohnRennie I knew mathematicians believed your best work is done at 20-25. But I didn't realize physicists held the same belief.

@JohnRennie Is that one of the sequels to Wool?

@dmckee I thought it was just me, so I joined the chat to moan and every else is out of close votes as well. It's been one of those days.

How are they? Worth my time.

5:42 PM

@dmckee Yes. It's not stunning literature but I enjoyed Wool and I'm enjoying Shift. I recommend them if you have the time.

@JohnRennie Shift is great!

Or rather, the series as a whole is a great story

@StanShunpike To all intents and purposes string theorists are mathematicians. This is one of the things that commentators moan about i.e. they have none of the physical insight that the greats like Einstein had.

'K. I like Wool, but I found myself wary about the follow ons for some reason.

@ACuriousMind Have you read Dust? Given how much I enjoyed Wool and Shift that will be high on my list of next books.

I see John's point, but I side with Woit over Motl. Probably just an opinion.

5:45 PM

@JohnRennie Yes, I've read all three (there are only three, right?), and liked them quite well

While we're doing literary review, I've just read Jon Butterworth's book Smashing Physics, and that was enjoyable.

I don't know about Physics, but I have followed the Climate Change stuff pretty well, and L.M. is a bit simplistic on that.

I'd vote to close something , but I don't think I have the rep.

@Jiminion Keep in mind that he is an expert in String Theory, no matter what his expertise in other topics may be.

@Jiminion Being a skilled string theorist does not make you a skilled meteorologist!

@JohnRennie Then why does he comment on it?

5:47 PM

@Jiminion Why do you comment on String Theory?

@Jiminion Same reason Woit comments on string theory?

Heh.

That's not an answer.

Yes it is. It's called being human.

Who amongst us can honestly claim they've never been sure they were right about an issue only to find they didn't know as much as they thought?

ST will sort itself out if it acts as it has for another 5-10 years. Or not...

5:50 PM

The advantage of being old (54) is that as I age I become increasingly convinced I know nothing about anything and therefore increasingly reluctant to venture an opinion.

Or at least reluctant to venture any opinion I can't write down as an equation.

@JohnRennie Ah ... only another 9 or 10 years before wisdom set in.

Phew! I was getting tired of waiting.

@JohnRennie The insight "I know that I know nothing" is at least as old as Socrates, so you're in good company ;)

Good.

They way L.M. comments on climate change and other areas makes me question his judgement in other areas, including string theory.

@dmckee You get a few years of wisdom before Alzheimers sets in :-)

5:53 PM

Gary Becker kept working until he passed away

Some people keep going and producing

Then there's Wald, Josephson, and Pauling....

Right, well that's answered - thanks for the undelete votes. Now I really must go. Bye all.

0

A: Is there a limit as to how fast a black hole can grow?

A 12 billion Solar mass black hole sounds massive, but actually it's not all that big. The radius of the event horizon is given by: $$ r_s = \frac{GM}{c^2} $$ and for a 12 billion Solar mass black hole this works out to be about $1.8 \times 10^{13}$m. This seems big, but it's only about 0.002 l...

@Jiminion I know what you mean about L.M. but his physics is usually amazing, he usually has really deep insight tbh

Why is string theory so controversial? People either seem to be for or against it. I don't see how an entire discipline can be that way. Usually it's just one idea within a field, not the premises on which the whole field is based.

Glen The Udderboat

@StanShunpike Hmm, economics perhaps?

6:06 PM

@GlenTheUdderboat what do you mean?

Glen The Udderboat

@StanShunpike I know nothing about it, but if there are differing entrenched opinions then people also have their livelihood at stake? Something like that? Perhaps?

@StanShunpike I think it is just as controversial as every other big new theory would have been, had they not all been at least tentatively validated by experiment relatively quickly. The problem is the lack of predictions that could feasibly be tested with the next years. So we have nothing to go on but aesthetics as to where research should go, and that leads to quite a lot of fighting about which approach is most beautiful/promising.

The whole of the 20th century, we were essentially in the reverse situation - the colliders (or the early quantum experiments) kept spitting out a ridiculous amount of data, and no one had a coherent picture how they fit together, so there was data to guide us. There is not enough unexplained data today to really have something to work with.

Oooh, only 18 unhandled reviews, it's decreasing!

6:23 PM

@ACuriousMind So is the mostmost pressing problem finding viable physical experimental tests so theories can be tested? I thought that's part of why they were upgrading LHC

@StanShunpike Yeah, but we are still below the scale at which we expect the Standard Model to stop working, so this cannot be a text for new theories yet, since they all reduce to the Standard Model in the low-energy limit. It would be very interesting if we found something, but so far the LHC has delivered no new physics. We hope to find something, but, essentially, all we're doing is making sure the SM is right so far.

The LHC is a QFT/theories beyond the SM-testing machine, not a GUT/TOE-testing machine

Well, perhaps a GUT, since any of them are QFT/extensions of the SM, too, but it doesn't help in the quest for quantum gravity.

Glen The Udderboat

@ACuriousMind Do the 'opponents' of string theory oppose in any way to LHC (wrong direction, misguided, whatever)?

@ACuriousMind Well below.

@GlenTheUdderboat The LHC is primarily looking for evidence of SUSY or dark matter IIRC, not ST directly.

@GlenTheUdderboat Only the crackpot variants. No serious physicist could think the LHC is misguided because we needed to find the Higgs, at least. And there's still the puzzle of neutrino oscillations and some other minor kinks in the SM which would be resolved by various types of new particles, so it's definitely worth looking no matter what your stance on the TOE programs is.

@0celo7 Right, but I thought that was the point. I thought if they could confirm or deny SUSY then they would be able to in effect assess the validity of string theory.

Glen The Udderboat

6:33 PM

@ACuriousMind Thanks.

@StanShunpike I don't know much string theory, but disproving SUSY would probably destroy our current understanding of it.

However, not finding anything is not proof either way.

@StanShunpike Mh, not finding any SUSY at all would be bad for ST, I think, but I don't think we have any reasonable expectation for the scale at which the stringy SUSY partners should sit, because we don't understand the possible string vacua/theories all that well.

@ACuriousMind Is it possible that sparticles only are observed near the Planck energy? If so, we won't see SUSY evidence anytime soon.

What the hell? NSFW: xkcd.com/631

@0celo7 I've no idea where the possible scales lie, but I think you can crank up at least the scale in ordinary SUSY models quite high. Can't tell you whether these are possible low-energy limits of ST though, and can't tell if anyone can tell

@0celo7 Heh, you mean, you don't have all xkcd memorized? ;)

@ACuriousMind We know the low-energy limit. It's called the standard model + GR.

6:40 PM

For more fun use of brainspace than formulae

@0celo7 + various residues of supersymmetry

@ACuriousMind Like?

When I say "low-energy limit", I mean "below the string scale", such that ST looks like a high-energy QFT

@ACuriousMind We're not all as obsessed as you are with xkcd.

I'm not only obsessed with xkcd, I think I also have much of smbc memorized, and that's thrice as much :P

@ACuriousMind I recall Zee saying something like: "These kids nowadays think anything below $10^{18}$ GeV "low energy" seems ridiculous to an old-timer CM physicist like me."

6:43 PM

@0celo7 Well, ST has SUSY in the string scale-regime, and depending how you compactify and take the low-energy/QFT limit, you get different "extensions" of the SM, but I'm not sure if we even know how to get the pure SM

As I said, the string vacua are not well enough understood to really make any kind of definite statements here

Quick check: I'm not that into GR, but this: "The center of a black hole is only a singularity when you apply relativity in a quantum regime." is totally false, right?

@ACuriousMind Are you asking me/hbar for quantum gravity??

No

I'm asking the hbar whether that statement is correct

It claims the center of a BH is classically not a singularity, that has nothing to do with QM

The center of a black hole is the singularity in GR.

Good

We need QG because of that.

6:46 PM

I was beginning to doubt my mind

We have no expectation of GR working at the singularity, but GR does predict one.

@ACuriousMind Ha! My question. And it hasn't even been closed/deleted in "The first 3 minutes...." (to paraphrase S. Weinberg).

@ACuriousMind Who said that?

@Jiminion You waited for the moment we're all out of votes, right? Because I'm kinda sure we've had that question before.

I don't really know how to search for it, though

So I can understand that you wanted to ask

I'm very puzzled that the answers all talk about quantum gravity

I looked, didn't see anything (the searching on SE kinda sucks, especially when they are so strident about no repeat questions.)

6:49 PM

The very premise is false - a singularity is an anomaly on the manifold - a "hole", and does not "by definition have infinite mass"

^^

@Jiminion It's often better to use google with site:physics.stackexchange.com behind your search

@ACuriousMind But isn't that mass occupying 0 volume?

@Jiminion "Volume" is not defined at the singularity.

@Jiminion Which mass? I don't know what you're talking about, all I see is an event horizon ;)

6:52 PM

The curvature is infinite, that's about all we can say (in GR).

@ACuriousMind Then how do you know there's even a singularity in there?

@ACuriousMind Wrong. You can't see the horizon.

@0celo7 Yeah, great, I see the stuff hanging in front of it, forever frozen in time but falling in in finite time or something like that

@0celo7 Space time curvature is infinite at a black hole? OK, I was wondering about that. (I had several questions, but I tried to stick to the practice of only asking one thing in one question.)

@ACuriousMind I don't know why people say this. The outgoing light is redshifted to oblivion, you won't see anything coherent.

You'd have to be right at the horizon to "see" anything, but the horizon is nonlocal, so it doesn't matter anyway!

6:54 PM

@0celo7 Right, so I see nothing, that's why it's black

Glen The Udderboat

What does it even mean to see something infinite?

Gotcha, I think

@Jiminion The curvature tensor and all invariants are infinite at $r=0$.

I'm much more at home with QM, I must say. This GR stuff is weird.

@ACuriousMind We can "see" black holes because of their accretion disks.

Those things are many times more energetic than nuclear fusion.

6:57 PM

Okay, this guy and his answers are getting on my nerves. Can anyone tell me whether that answer is true or not without me having to watch a 90min video on youtube that probably only has a distant relation to the topic?

Generally speaking, it's good practice to quote what they say in video and provide the link not ask others to watch the whole video lol

i don't think that's true; the curvature is infinite for schwarzschild metric. that's nothing to do with QM

@ACuriousMind Yeah, no need to invoke QM on this one

oh but does he just mean that gravity is strong, so you probably need quantum gravity. perhaps

« first day (1575 days earlier) ← previous day next day → last day (3361 days later) »

Transcript for

Feb '1526

The h Bar

General chat for Physics SE (physics.stackexchange.com). For M...

join this room
about this room

00:00

06:00

12:00

18:00

all times are UTC

site design / logo © 2024 Stack Exchange Inc; legal

mobile