The h Bar

0celo7

00:38

poor quiz writing skills are once again apparent

pretty sure there's multiple right answers here

ACuriousMind

@0celo7 I take it you can only choose one?

0celo7

yes

the one I picked (shown in the picture) was correct

at least they haven't asked "is gravity a vector force" yet

ah, an astro nerd

@HDE226868 how many right answers to that question?

punkerplunk

three

0celo7

even GR is an approximation, so yes

I think there's a Kepler's law for GR

punkerplunk

one is only slightly less ambiguous than the others

0celo7

00:42

I dunno, that might be worth telling the profs about.

@punkerplunk Only one is mentioned in the text, and this was a reading check quiz.

punkerplunk

it might be a rouse to see if any students are actually thinking

HDE 226868

@0celo7 Well, it could be argued that 3) is just a version of 2). Kepler's laws are approximations because they're typically only applied to two-body systems.

1) is probably correct because of the famous test of Mercury's precession.

0celo7

I could argue that Keplers laws are wrong because of quantum gravity

HDE 226868

All three are correct, from a certain viewpoint.

punkerplunk

and have you actually SEEN his observatory?

it was, quite the literal hole in the wall

0celo7

00:46

string theory predicts corrections to the Einstein equations, so the Schwarzschild geodesics are wrong

it would appear, to first order, $$R_{ab}+\frac{\alpha'}{2}R_{adce}R_{b}{}^{cde}=0$$

there you have the first order quantum Einstein equations

in a vacuum

HDE 226868

@0celo7 $\alpha'=?$

0celo7

that one string constant

er

Regge slope?

ACuriousMind

Yes.

0celo7

inverse string tension

punkerplunk

i suspect it'll take me a while to ungolf that equation

0celo7

00:52

can someone please solve the quantum Einstein equations for $\mathrm{SO}(3)$ symmetry and find the geodesics?

thanks

and do it before my physics lecture tomorrow?

@ACuriousMind I have an idea for your thesis :)

ever wanted to solve some PDEs :)

Secret

What's your view on neutrino oscillation and superposition then?
(This question has a hidden purpose)

0celo7

conversing with yourself, eh?

classic, won't work

punkerplunk

SO(3) incorrectly assumes quantum forces are strictly subject to euclidean space?

0celo7

in fact, this deepens the suspicion

@punkerplunk what?

$\mathrm{SO}(3)$ just means rotational symmetry for each "time slice"

ACuriousMind

@0celo7 If I ever want to, shoot me.

punkerplunk

01:00

about an axis

0celo7

@ACuriousMind pls

pls solve the quantum Einstein equations

help me Bajoran, you're my only hope

Secret

Here's a way to prove it, try reporting me as being abusive to the internet to the ISP. If I and JD are the same person, then both will vanish after I am being blocked form internet access (this is because even proxies use your own ISP in your country)

but if JD still stays, it means we are in different geographical locations and we cannot be the same person

0celo7

not true

you could have multiple internet connections, obviously.

amateur

you think I'm fresh on the block

ACuriousMind

@Secret: You know 0celo7 is just joking, right?

@0celo7 You are joking, right?

0celo7

as serious as I was about AK

::stares::

still not convinced of that

ACuriousMind

01:02

lol

punkerplunk

is AK alaska?

i tried to internet in alaska once, it's hard.

ACuriousMind

No, Alicia Keys. Long story.

0celo7

not long enough

::gets out file::

Secret

@ACuriousMind I am not really sure, he is really serious that I am JD (he said I fabricate JD just to act dumb).
I have seen in the past if there are sock puppets, they can usually managed to trace to the same computer or talking style.
I think only the mods can work out this one

Ever since I post my first weird picture on this chat, 0celo7 has been suspicious on me

HDE 226868

This is starting to sound a bit like the Moriarty-Holmes showdown in Sherlock.

0celo7

01:06

can't fool this sleuth

ACuriousMind

@HDE226868 Question is - who is who?

punkerplunk

the real question, why attempt to attribute a self, and all requisite restrictions to, to a brain such as yours, able to communicate in ways such as this/

HDE 226868

@ACuriousMind Good question, Lestrade.

Secret

0celo7 conspiracy goes like this:
He said the mastermind behind JD is me, and that I fabricate JD (including having a false bio of computer science, cannot do maths, has controversial views on some physics topics, pretty much everything you know about JD)

But the question is, if the conspiracy is true, why will I waste so much resource doing that, what will be my gain?

You guys knows more about sock puppets than I do, but I never knew of any sock puppet that can keep separated talking styles for more than months

punkerplunk

so how does alicia figure into this? and how can she?

HDE 226868

01:11

@Secret Yep, that's Sherlock, all right.

But the question is, if the conspiracy is true, why will I waste so much resource doing that, what will be my gain? - Simple: you're a sociopath.

Secret

Currently, the only internet proof way I can figure out that might show we are two different people is we all meet up face to face.

But is this worth us all to fly to one location just to prove our identities?

HDE 226868

Problem solved.

punkerplunk

I takes more than one person in a mother's basement to qualify for 'conspiracy'

0celo7

wow

you think I'm in my mother's basement?

I moved out over a month ago, asshat.

punkerplunk

i moved out a decade ago

moved in last year

0celo7

01:13

I was 7 a decade ago

punkerplunk

~sigh

i am asshat

0celo7

I like velvety ass hats

none of this wool BS

punkerplunk

I suggest you solve this by meeting irl, preferably around a hottub. i'm going to stay here cause i'm grounded :(

Secret

Where's JD living in?
for me, I live in Sydney Australia

user54412

@HDE226868 Of course, the GR effect is much smaller than the deviations that come from Newtonian pulls by the other planets (this is the part of the story that always gets left out). And to first order the GR effect is to make the ellipse precess at constant eccentricity, which means it only changes eccentricity to like 2nd order.

user54412

01:22

Not that I'm saying it was a good question.

Secret

Actually, thinking more deeply about this, it is possible even face to face meeting cannot solve it:

For example, suppose I, JD, and 0celo7 all met up
How do we know that we are indeed I, JD and 0celo7?
A: Show that we can enter our passwords and logged into our own accounts?
Q: But if 0celo7 is really skeptical, he could also say that the "JD" he is meeting is actually me prearranged with a friend and I told him the password to JD's account

Basically, 0celo7 has open a very disturbing can of worms, on how difficult it is (than I initially expected) to prove your identity is linked to you…

HDE 226868

@ChrisWhite Thanks; I didn't know how powerful the effects were relative to one another.

dmckee

@ChrisWhite In particular even where it makes the biggest difference (that is for Mercury) the GR precession is still less than the classical perturbative precession from the other planets.

The hardest part about checking GR with the precession of Mercury's orbit was subtracting off the foreground from the other planets.

user54412

@HDE226868 It's actually quite remarkable that pre-computers astronomers were able to calculate the residual deviation.

Secret

So my conclusion is, either the mods have a way (and is bother enough) to resolve this conspiracy, or we all cannot do anything about it

HDE 226868

01:25

@ChrisWhite Man, I'm not sure I'd find astronomy so appealing if I lived back then.

user54412

I think Mercury is the planet with the most uncertainty in its long-term stability. It gets yanked around so much it could just get ejected from the system, or crash into the Sun or something.

Secret

In fact, the "I, JD, and 0celo7" scenario I analysed above can go in many directions, the "0celo7" I am meeting might not be 0celo7 himself, or that JD is 0celo7 or that I am 0celo7

This is getting messy...

*BSOD and get back to work on my honours project*

HDE 226868

Whenever I read about the stability of the Solar System, Mercury is always put forth as Exhibit A.

punkerplunk

Imagine kepler compiling all of tycho's life long observations. BY HAND.

HDE 226868

Wikipedia lists 2500 different simulations by this group. I would not want to do that without a computer. Heck, I don't think anyone could, within a reasonable amount of time.

user54412

01:29

@punkerplunk Imagine him doing that hurriedly, in secret. Since Tycho specifically didn't want his data falling into his estranged assistant's heliocentric hands. And Kepler just made off with the data anyway when Tycho died.

user54412

@dmckee Astronomy is often subtracting off large foregrounds. When you can't set up your own experiment, you take what little signal to noise you can get I guess.

punkerplunk

I like the word metastable

0celo7

@Secret what are you talking about

ah I see

yes JD could just be your accomplice

Secret

01:54

I cannot really see any way out of this
In fact, using that findings above, how do other users know that you are not just another fabricated account of mine, or maybe it was you who fabricated me?

0celo7

they don't

Secret

Of course we (me and 0celo7) know we are two separate people, but from the perspective of other people in the chat, there is really nothing tell you apart if you allow the fabricate account to act like a different person with a different personality

0celo7

do we know that

maybe you're imagining me

punkerplunk

i cannot be imagining you without also imagining mercury

however i do not know you are not all well timed chatterbots

0celo7

what does mercury have to do with anything

obe

02:08

What is the point of this discussion?

0celo7

hush

punkerplunk

filler till someone conjures a scientific sounding problem

0celo7

conjecture: human spin statistics theorem

we're essentially identical particles

no way to distinguish us

obe

We're all JD, JD is all of us.

0celo7

@obe I'm probably going to order Arnold

gotta do some geometry problems that aren't GR

obe

02:15

Didn't you read the important parts?

0celo7

yes

did not do exercises

and did not read 400 pages of it

obe

what about that mechanics book I linked a while back

0celo7

dunno

is it springer?

I'm only getting Arnold because it's 25 bucks

obe

It is not.

0celo7

for me it is

oh

are you saying it's not springer or not 25 bucks?

who is will

are you my physics TA

obe

02:19

Lol that would be embarrassing.

0celo7

why

obe

Idk, forget what I said.

perhaps it's only me.

0celo7

seems like you want a fight

are you saying my actions are embarrassing

obe

D:

@0celo7 first one.

0celo7

what about the second

also Dr. Freire told me I should read Arnold

so

obe

02:24

Dry cleaner is the coolest job right?

0celo7

what?

you're insane

obe

You sit there and chill all day.

Dry cleaners are always bored.

0celo7

sigh

the best job is the job that impacts the world

dry cleaners don't

obe

wow.

0celo7

Stop sitting around and go make me a fucking iPhone

+100 points for reference get

obe

02:33

Dry cleaners launder the world's clothes.

0celo7

they don't produce value

sitting around all day does not produce value

obe

You're missing the point.

Dry cleaners are able to do whatever they want all day.

0celo7

actually, I think the quote is

obe

Therefore they can learn physics in their free time.

0celo7

sigh

you're missing the point

there's more to life than learning physics

obe

02:36

Life is depressing.

0celo7

@obe please verify that gravitational acceleration at the surface of a planet is $4\pi Gr\rho/3$

wait a moment

damn, no one who knows physics aroudn

obe

02:55

D:

0celo7

done with homework

Secret

03:26

$$|\mathbf{F}_g|=\frac{GmM}{r^2}$$
$$|\mathbf{g}|=\frac{|\mathbf{F}_g|}{m}=\frac{GM}{r^2}$$
$$V_{planet}=\frac{4}{3}\pi r^3$$
$$\rho \propto \frac{M}{r^3}$$
$$|\mathbf{g}|_{planet}=|\mathbf{g}|V_{planet}=\frac{GM}{r^2}\frac{4}{3}\pi r^3$$
$$=\frac{4GM\pi r}{3}=\frac{4\pi G r^4\rho}{3}$$
Why I am off by powers of 3 ($r^4$ instead of the required $r$)?

punkerplunk

order of operations?

Secret

"please verify that gravitational acceleration at the surface of a planet is $4\pi Gr \rho /3$" that's the problem statement

punkerplunk

look at the part of the equation with rho

is that mass divided by radius cubed?

I'm guessing that cancels out three of the r's in the r^4 portion somehow

because your standing on the surface, and you're at exactly one R

r8

r*

Gravity, one R, and than you have some jumbo about mass density.

Also, is the equation for (rho = m/r^2), not (rho = m/r^3)

the133448

04:54

Hello I just found this awesome device at a toy store its a plastic tube which has an led strip and a buzzer inside, and when you hold two conductive plates at the end it lights up. How does this work?

Huy

05:08

a flashlight?

Pies

So...question

What kind of questions belong here and what kind on the Chemistry site?

Regarding atomic physics and quantum mechanics

Oh wow, just realized why the room was called "the h bar" XD

dmckee

@Pies There is a broad region of overlap between the disciplines. Problems that are worked on by people educated under both names. As long at that is true they are on topic on either site.

Pick the one that you think is mostluy likely to give you a good answer fast.

Pies

Er...K?

Which is more popular?

dmckee

If a few days pass without an acceptable answer flag the question and request migration.

Physics is older.

Pies

How about astrophysics? Does that go here or the astronomy site?

dmckee

05:15

Don't know which one has more active users, though.

Same deal. Big overlap. Take your best guess.

Pies

Okay...

So...ya wanna hear a joke?

dmckee

10

Q: Are sophisticated Astrophysics Q's better asked in the Physics SE or Astronomy SE?

My interests primarily pertain to Astrophysics (and Astrochemistry). This subject appears to have two masters: Physics SE and Astronomy SE. How do I decide where to post, and how would you characterize the astrophysics sub-community on each SE? Does double posting of Q's make sense? I will be pos...

Pies

Why did the photon want to lose weight?

To stay light!

Wait...photons don't have mass, so...

Huy

:/

Pies

Anyway, I have a legitimate question

Is mass just an object's resistance toward going at lightspeed, or is it the amount of matter that an object is made of?

Huy

05:19

@dmckee it was a joke. :D

Pies

.-.

dmckee

@Pies In modern parlance? It's the norm of the energy-momentum four vector.

Or it's inertia.

Pies

Isn't inertia just a form of mass?

dmckee

Or it's strength in affecting the shape of space-time.

Pies

And there's other types beside inertial mass, like gravitational mass, etc.

dmckee

05:21

@Pies Inertia is a property.

Mass is a way to quantify that property.

@Pies In GR it is axiomatic that they are the same.

Pies

A'right. But now a bigger question. Is gravity caused by mass, or by energy and momentum?

dmckee

Yes.

Pies

.-.

Which?

dmckee

To be more precise it is caused by the "Stress-energy tensor".

The compoents of the tensor are affected by all three.

Pies

Ohhhh...

dmckee

05:23

At low speeds and energy densities you can safely think of it as caused by mass with maybe a small perturbation from energy and momentum.

Generally too small to measure.

Pies

So, I guess one more question: is mass an illusion? I mean, particles are normally massless, and most react with the higgs field. So is mass not a fundamental property?

Rather just created by some effect?

dmckee

"particles are normally massless, and most react with the higgs field" is only partly true. It applies to certain fundamental particles, but protons and neutrons are not fundamental, and much of their mass comes from their binding rather than from the Higgs field.

Pies

Sorry, meant elementary particles

dmckee

That's a line that science writer like to trot out because it sounds deep, but...

Any way. Late here, so I'm for bad. Night.

Pies

All right, 'night

Forever alone... ;-;

Huy

05:28

sory

Pies

Oh howdy

Uh...ya in high school or...?

Sigh...

Huy

university

sorry you need to ping

if you want me to pay attention

:D

Pies

Call me a moron but...how do I ping?

Huy

write @username

then the user will get a notification

Pies

Ah, got it

Huy

05:35

so they know someone's talking to them

Pies

So...you wanna hear a joke?

Huy

try telling me one I don't know yet

Pies

Where do bad photons end up?

In a prism.

OH!

...

Huy

-.-

Pies

.-.

Huy

05:38

=_=

so you're in high school? US?

Pies

Yep

Huy

oki

Pies

Trying to learn the stuff they don't teach ya in high school physics

Huy

and I suppose you wanna study physics at uni?

Pies

like QM and GR

Astrophysics

Huy

05:39

got a solid math knowledge?

Pies

Well, I did...my calc teacher just left last week

and we don't got anyone else to teach it...so

Huy

lol

so you don't have any calc anymore?

Pies

-.-

I guess not

Huy

hilarious

Pies

To who?

Huy

05:40

to me

Pies

Yeah, I can't take the only subject I looked forward to. So "haha" funny...

Huy

what topic is that?

Pies

Calc

Huy

do you already have some knowledge of it?

I doubt you can understand any QM or GR otherwise

Pies

Well...considering how I skipped precalc and we were summarizing some of that subject's ideas...

I doubt I know much

The non-mathematical explanations in QM are amazing

Huy

05:42

can you list some broad topics you are comfortable with?

Pies

I might not understand the math, but I keep finding new information

I guess

Subatomic physics (sorta), QM (trying to), special relativity, and a tiny bit of GR

Huy

I mean math wise

Pies

Oh

Well we just finished matricies, haha... ;-;

Huy

and what do you know about calc?

Pies

Here I thought I'd be going into cool stuff like hyperbolic functions

Huy

05:44

why are those cool

Pies

Because they explain more about the universe

Hell, that's the whole reason I like physics and math

Huy

do they?

Pies

I guess I never got to learn any calc stuff before she left. -.-

Huy

how?

Pies

Most things in mathematics relates to how the universe functions, no?

Huy

05:46

I can't really tell you that, I don't know most things in mathematics

Pies

Well, no one really does...

But I'm pretty sure the Universe does run on mathematics

Huy

but mathematics is just a fiction

and used to model stuff that happens

Pies

It's more of a description...

Huy

I think it's more of a model

if it was a description it would be correct at all times and can't change, no?

Pies

I kinda think that it could exist without humans...

Huy

05:49

maths?

Pies

Yep

Huy

how?

Pies

Well, maybe we don't invent math, per se, but discover it

Huy

I think it is invented

Pies

Everything can be described by an equation. We just gotta figure out what it is

Huy

05:49

I think modeled

Pies

Ya know, the fact that we can bring philosophy into this is awesome

But yeah, when I try to learn QM, I want to get by without the mathematics

Huy

how do you want to achieve that?

Pies

I gotta get more direct explanations, so I can imagine how these things work

Huy

do you think learning it is just knowing some things that happen but not knowing what could be the reason for it?

Pies

Reasons could be explained without math, no?

Huy

05:51

if that was the case, why would physicists use maths?

Pies

Because, if used properly, mathematics can be a reliable and undeniabble explanation

Other explanations can be misinterperated by the mind

If I told you an electron only has a probability of being somewhere, you'd have to rationalize what that means

Math is basic and fundamental

Huy

I don't see how you can explain any of that without maths

Pies

For example, give me something that can only be described via mathematics

Like "why ___ happens"

Huy

why does the earth revolve around the sun?

Pies

I'm sure I could find a non-mathematical equivalent

The Sun has more energy, momentum and mass than Earth. Its gravity distorts the geometry of spacetime and attracts the Earth.

Did I get that right?

Huy

05:55

what is energy, momentum, mass, gravity, geometry, spacetime and attraction?

Pies

Mass is an object's resistance toward going at lightspeed. All elementary particles naturally travel at c, but most are inhibited by the Higgs field

Huy

what is resistance, what is light speed? what is speed?

Pies

So the massless ones have no resistance, while the massive ones cannot achieve lightspeed because they have some resistance

Speed is a method of describing how much time an object takes to travel through space. It is a scalar property as opposed to velocity, which is vector.

Huy

scalar and vector?

so to measure speed you need maths, no?

Pies

Goddammit, that's where things get confusing for me...pretty sure vector has direction and magnitude, while scalar doesn't...

Of course. But you can explain what speed is without math

I'm trying to learn QM before I begin applying it

Anyway, it's 2:00am here...Gonna go to sleep. 'Night

Huy

05:58

but I need you to measure it. you claim that the sun has more "mass", and then you say mass is something related to "resistance" which is something that has to do with "light speed", and then you talk about "speed". now how can I possibly see that the sun has more "mass" if I can't measure "speed"?

Pies

I have no proof of these things, but I know why certain phenomena happen. I don't know how to mathematically prove it has more mass – that's what I lack. However, I am learning concepts, like how it does have more mass, and that's why other effects happen

Huy

you don't prove things in physics

you can't

Pies

All right, I gotta leave. 'Night

Huy

gn8

Secret

06:23

Why do users recently on this chat can be linked to 0celo7's conspiracy?
Part of Pie's approach to learning is quite similar to me

He pretty much spell out how my word versions of my picture works

Secret

HDE 226868 is right on one thing:
While I am not diagnosed as a sociopath, my low empathy means I can act like a sociopath

Given the conspiracy have open such a can of worms, it is possible to exploit the conspiracy itself to result in a lot of innocent people to get banned in the process for being accused of sock puppets, just to so how ridiculous the conspiracy is

My mind when frustrated by acussions is completely different from the sharing, usual personality I displayed.

"You are the mastermind"

Secret

My darkest personality is only being displayed when I am frustrated for being accused. It works by playing along the very thing I am accused of, so that the outcome is massive number of innocents get involved and harmed in the process (it will happen because there are no ways to resolve the conspiracy and to distinguish the truth and the fabricated)

All just to show that the conspiracy itself is ridiculous. Yes, when frustrated, I will show how ridiculous the conspiracy is if it is true, at the cost of other people's wellbeing

Secret

But anyway, back on topic:

As pointed out by many physicists in the field, it is dangerous to learn quantum without the maths.
Acuriousmind once remind that our mind tend to think classically. But quantum is not classical mechanics, thus interpretations and word description of quantum phenomenon can be easily interpreted and even controversial (as david Z reminds us how it is often debated between theoretical physicists on the reality of a quantum superposition, and then you have a lot of interpretation on quantum mechanics just to try to ascribe a physical meaning to the wavefunction

As an undergrad just graduated from my physics degree, you need at least a solid understanding of linear algebra to understand most of quantum. You said you have learnt matrices, that's a good start for you to go to linear algebra when you enter uni.

But you still need to sharpen up your calculus skills, as most of our physical models of reality are based on it

Secret

06:50

correction: easily misinterpreted

And if you want to do GR, you need to learn differential geometry. This implies you need to be pretty good at calculus because you will be doing all those derivatives in a more sophisticated form when you compute things like the tangent spaces of manifolds, and our current best model on gravity, GR, is spacetime, which is a pseudoriemann manifold

I don't have the luck to do differential geometry because of the time constraints of doing a double major, hence I need to catch up by reading books on it myself in my free time (and check my understanding of it at forums and with my peers)

Similar things might apply to your case when you catching up your calculus background given your teacher left before the course is finsihed

skill patrol

07:08

hmmm...interesting

:-)

@Secret do you keep a diary/journal?

Secret

Not really
The closest thing is I use Facebook as some kind of notebook
Otherwise I tend to summarise stuff I learnt in my course to prepare for my exams
That might be why I can remember the requirements of some subjects

I do keep a dream diary though, because I often consult for inspirations from it

John Duffield

@dmckee : I'm not wrong. I know my relativity. Gravity is not a force in the Newtonian sense. It doesn't add any energy to the falling brick, it doesn't do any work on it. You do the work when you throw it up in the air. Momentum is shared equally but KE is not. The brick gets the lion's share, and it's converted into PE. The energy is the brick, not in the planet or gravitational field or system. Ask a question and I'll elaborate.

Secret

@JohnDuffield What's your view/interpretation on neutrino oscillation and superposition? Perharps yours might be similar to mine

Correction: I forgot "Ask a question and I'll elaborate." at the top of my paragraph

John Duffield

07:24

@Secret : IMHO neutrinos oscillate because they're akin to the travelling breather. The washing line and pliers thing is an analogy wherein you twist the washing line and let go. Then a wave races away. This wave isn't a transverse wave, it's back-and-forth rotational. As the rotation occurs the washing line contracts and expands so the net wave speed increases and decreases slightly, so the effective mass changes. Superposition is just a wave thing. There is no magic.

Secret

what property of the neutrino is the rotation of the breather corresponds to?

John Duffield

Secret: spin. Twanging the washing line emulates a transverse-wave photon. The neutrino travels at much the same speed, but it isn't a transverse wave. Find a washing line and sight your eye down it before you twang it. You can see the wave race away. Then twist the washing line with your pliers and let go.

Secret

07:42

From particle physics experiments, we know of the values of the 3 neutrino mixing angles $\theta_{12}$, $\theta_{23}$ and $\theta_{13}$. We know that the first two are rather large but the last one is tiny. How can this be explained in you interpretation?

To the reader:

The above conversation has 3 purposes

Obtaining new ideas, check the interplay between experiment results and interpretations and a hidden purpose that only one person knows

Transcript for