The h Bar

4:00 PM

@0celo7 add garlic fried in butter to it. Plain pasta with butter, garlic and some black pepper is really nice. Add some finely chopped fresh chillis if you want some extra bite.

0celo7

@JohnRennie A garlic cream sauce does sound good. I will research

@JohnRennie Oh, I'm including the pound+ of sauce in there

John Rennie

Yesterday's lunch was pasta with chopped Polish sausage, butter, tomato and yes garlic. Very nice too.

0celo7

@JohnRennie to appease you I will make garlic chicken tonight

Sid

Garlic paste or sauce is much better than raw or cooked garlic.

Slereah

Finding the Boltzmann distribution with EM in it isn't helped by the fact that the full name is the Boltmann-Maxwell distribution

John Rennie

4:07 PM

@0celo7 If I hadn't just eaten 11 parathas the thought of garlic chicken would make me hungry

Sid

... 11 parathas?

:O

John Rennie

Shrug :-)

0celo7

@Sid I am going to make a sauce

I looked up a recipe

John Rennie

@Sid They were shop bought ones and they are quite thin. More like chapatis really.

Sid

@0celo7 Sounds good. and hopefully for you, they would be tasty..

@JohnRennie I.. didn't actually know that Parathas are available in UK. I thought they were a regional thing..

0celo7

4:10 PM

UK $\cong$ India

John Rennie

@Sid these days the choice of food in the UK is very good. There are lots of firms run by Indians (various states) producing their regional food for the UK market

0celo7

@JohnRennie I have been having a lot of success with just grilled chicken with no BS

Slereah

I think you mean India $\subset$ UK

Balarka Sen

Used to be.

John Rennie

@Sid the parathas were made by these guys

Sid

4:12 PM

@0celo7 UK and India are about as far apart culturally as they are geographically

Balarka Sen

@Sid Well, India was a British colony. There's certainly some cultural traits we (well, perhaps not all of India, but the capitals) inherited from the Brtis, but I am not sure of the other direction.

0celo7

@Sid so?

Sid

Which means they are surely not congruent. :)

0celo7

@JohnRennie do I need a garlic crusher?

@Sid that does not mean "congruent"

@JohnRennie not having parent's stuff is hard

Sid

Really? I thought I knew Mathjax stuff..

0celo7

4:15 PM

@Sid it means isomorphism

John Rennie

@0celo7 no, crush it with the blade of a knife

Sid

Isn't that same as congruent? Or am I terribly mistaken?

0celo7

@Sid I don't know what congruent means

Slereah

Congruent means of the same size

Balarka Sen

isometric objects in R^n

The Dark Side

4:17 PM

WTF

5

Q: Were 25% of newly-infected HIV-positive gay men actively seeking infection in 2003?

Rense quotes a 2003 Drudge Report article, that previewed an apparent Rolling Stone magazine article titled "Bug Chasers: The Men Who Secretly Long To Be HIV+." The men who want the virus are called 'bug chasers' [...] "At least twenty-five percent of all newly infected gay men fall into...

0celo7

the globe is not $\Bbb R^n$

OR IS IT

I am actually flat earth agnostic

The Dark Side

Well it can be taken as locally flat ...

0celo7

I have 0 (zero) evidence that the Earth is not flat

Slereah

well yes, but that's true of all manifolds

@0celo7 Never took a plane?

0celo7

Ok, physicists need to stop saying "locally flat"

Slereah

4:19 PM

Or got on top of a very tall building

Sid

OF course the Earth is flat. I mean, how hard is it to understand that we are all living on a giant pancake

0celo7

it's a technical term

@Slereah you can't see the curvature of the Earth from a very tall building

@Slereah I have, but do what?

Cruising altitude is not high enough to see the curvature

Slereah

Look out the window, see the horizon move?

0celo7

@Slereah atmospheric effects

but it moves so slowly anyway

Slereah

I mean the horizon business doesn't guarantee sphericality, but it means that it's not flat at least

0celo7

4:20 PM

and plane windows could be bulged as to give the effect of a fisheye lens

Slereah

Open the window then

0celo7

They don't let you open plane windows. Wonder why.

The Dark Side

Not conclusive though.

0celo7

@TheDarkSide That's a fisheye lens

I mean come on

Slereah

You can do like erathosthene

Measure shadows at noon in Athen

then travel for a few months south

And measure the shadow there as well

0celo7

4:22 PM

Ok, so we take our evidence that the Earth is round from Erathosthenes?

Seriously?

Balarka Sen

I think the Greeks guessed theatricality by checking out the shadow of Earth on the moon on an Eclipse.

The Dark Side

Oh dear Lord. So now, we have to prove that the Earth is curved.

again.

Balarka Sen

sphericality damnit

autocorrect

Slereah

@0celo7 He was the first to check it, yes

0celo7

@Slereah I know he was

Slereah

4:23 PM

Although there have been many other experiments in between

0celo7

But there are explanations for his experiment that avoid a spherical topology.

Slereah

Sure but this was to disprove a flat earth

For which this works

The model of the world prior to this was

0celo7

What?

Slereah

Flat landmass on a giant ocean

0celo7

You are assuming that light goes in a straight line.

Slereah

4:23 PM

With a spherical sky

0celo7

Why would you make that assumption?

Slereah

@0celo7 That's actually an old argument against curved space

Even before relativity existed

0celo7

The prroblem with round Earth is that there are so many assumptions that are absolutely ridiculous

Slereah

I think it was... Poincaré who came up with it?

0celo7

You have not proved that light always goes in a straight line

Slereah

4:25 PM

He said that assuming a curved space could be done away simply by assuming that light does not go in a straight line instead

0celo7

Well, that's Einstein's old argument.

Slereah

Einstein and the evidence

0celo7

If light does not go in a straight line, might as well assume curvature and then it does go in a "straight" line.

Slereah

That is also by the way a big part of Reichenbach's book

0celo7

And we know it doesn't go in a "straight" straight line...so curvature.

Slereah

4:25 PM

The definition of a straight line

0celo7

How does one even define a straight line

Slereah

Well that is the issue

You have to make assumptions as to how you measure something

0celo7

I guess it's like porn

Slereah

Because you can't guarantee that the process of measuring a line with a ruler, for instance, guarantees a straight line

Same with congruence

0celo7

The ruler might be crooked

Slereah

4:27 PM

In the end the definition of "straight line" is intrinsically linked to the process by which you measure it

And you just have to put it in your pipe and smoke it if you don't like it

Of course that means you can redefine all that in a different way

Which is basically what Pauli Fierz GR does

All flat space but the gravitational field curves the path of light

The Dark Side

popsci.com/10-ways-you-can-prove-earth-is-round

Come on @0celo7 - start trashing this out one by one.

Slereah

Or string theory, I suppose

since it is also on a fixed background

0celo7

@TheDarkSide Look, my basic argument will be that I have not verified anything in that article myself. Pictures are worthless nowadays.

I have no reason to believe that the Earth is round other than hearsay.

Fake news.

Slereah

do some amateur astronomy mb

I did some of it back in the days

Abcd

In dot product of vectors through components we only get a magnitude because $ \hat i. \cap i=1$(sameforjandk)icap.icap so how is that possible that we ain't getting any direction?

Slereah

4:32 PM

what

0celo7

@Abcd cross product gives a vector

what are you talking about

The Dark Side

@0celo7 OK. I get it now.

Abcd

Sorry for the poor formatting. I am trying to edit

The Dark Side

Have you seen an electron @0celo7?

0celo7

@TheDarkSide That's why I said I'm agnostic.

I have no reason to believe the Earth is round or flat.

@TheDarkSide No.

The Dark Side

4:33 PM

So, do you believe in Chemistry?

:P

0celo7

Some of it.

Abcd

Guys please help.

If you didn't understand the question I can explain.

John Rennie

@Abcd it's hard to know what you are getting at

0celo7

@Abcd your question is unintelligible

Abcd

@JohnRennie Alright. See: There's a method of finding dot product through the orthogonal components, am I right?

The Dark Side

4:36 PM

@0celo7 Hey, what happened to agnosticism there, pal?

John Rennie

@Abcd the dot product rule you're used to is a bit of a simplification.

Abcd

Now when we follow this method, we arrive at an answer which has no direction in terms of i, j or k.

How is this possible @JohnRennie?

John Rennie

The dot product is really $g_{ab}x^a x^b$ where $g$ is the metric tensor.

But in flat 3D Euclidean space this simplifies to give the rule we all get taught at school for the dot product.

The dot product is a scalar, or alternatively a rank zero tensor.

Abcd

@JohnRennie Okay. Understood. Thanks.

John Rennie

I think you just have to accept that it is a scalar unless you want to go into exactly what it is in more depth than is really justified at school level maths.

@Abcd: try calculating the dot product in polar coordinate form and you'll quickly discover it's more complicated than you thought.

The Dark Side

4:42 PM

@JohnRennie - How will frozen garlic help you in a vampire apocalypse? #ACuriousDarkSide

0celo7

@TheDarkSide I have verified some of it myself

but I have no reason to believe in atoms, for instance

The Dark Side

@0celo7 bwahahaha ...

@0celo7 BWAHAHAHA ....

John Rennie

@TheDarkSide you defrost it, fry it with butter and fresh chilli, toss with pasta cooked al dente then eat it. Does it work? Who cares :-)

The Dark Side

@JohnRennie And eventually all of that gets sucked up by a vampire ...

John Rennie

@TheDarkSide vampires don't like the taste of physicist and garlic

The Dark Side

4:46 PM

@JohnRennie especially when they are spewing GR ??

So, that's basically conceding that garlic tastes yuck

John Rennie

@TheDarkSide iff you're a vampire

Sid

You are a vampire if garlic doesn't taste yuck to you.

The Dark Side

@JohnRennie :P

John Rennie

Right I'm off to (a) slump into my armchair (b) read this weeks New Scientist and (c) drink a cold beer

0celo7

@JohnRennie (d) read Wald

Abcd

5:00 PM

Where does $\hati - j^$ lie? According to me it should be in 4th Quadrant but my book says its in 3rd Quadrant.

How do I make the cap symbol :(?

$\cap$

\cap

wot

@Abcd $\cap$

@heather I want the vector cap symbol

0celo7

5:01 PM

why do you need a cap for liner algebra

Jaime Gallego

$\hat$

0celo7

@Abcd 3rd

heather

@Abcd oh, $\hat{}, i think

$\hat{i}$

yep.

Slereah

$\widehat{\mathfrak{Hello}}$

Abcd

Where does $\hat{i} - \hat{j}$ lie? According to me it should be in 4th Quadrant but my book says its in 3rd Quadrant.

0celo7

5:02 PM

$\mathfrak H$ is an underrated character

@Abcd I already told you

Abcd

@heather thanks

Slereah

i think I've seen it used

heather

it's generally called a "hat", btw, not a cap, which can instead refer to an intersection in set theory @Abcd =)

Slereah

To express... Hilbert spaces?

Abcd

@0celo7 Can you explain why?

heather

5:03 PM

so we'd say "i-hat" or "j-hat".

0celo7

@Abcd draw a picture

Abcd

@0celo7 Done

Labelled i hat and j hat.

0celo7

@heather or a product in singular homology

Abcd

What next?

0celo7

@Abcd what does $i+(-j)$ look like

Abcd

5:04 PM

@0celo7 It looks like a diagonal in the 4th Quadrant

0celo7

yes, so move the base of the vector to the origin

now it points in the 3rd

Abcd

@0celo7 I didn't get you.

Anyone?

bolbteppa

Criticize: Dirac spinors are irreducible spin representations of the extended Lorentz group

Jaime Gallego

@Abcd It should be on the 4th quadrant, that must be a typo or some weird def'n.

Abcd

@JaimeGallego @0celo7 said it should be in the 3rd :(

Jaime Gallego

5:11 PM

I don't understand his argument either.

Abcd

Someone please help.

@JaimeGallego Same here.

Jaime Gallego

Maybe he's messing with you

0celo7

The result is (1,-1), which is clearly in the 4th quadrant

I don't know what you two are on about

Jaime Gallego

8 mins ago, by 0celo7

now it points in the 3rd

0celo7

@JaimeGallego ???

Abcd

5:14 PM

@0celo7 Why did you say this?

0celo7

@Abcd I don't know how to add vectors?

Abcd

What's happening?

Conclusion: It's in 4th Quadrant. End of story. Thanks.

Jaime Gallego

0celo7

the left panel is kind of random

it's the definition of a smooth manifold and then Clifford algebra?

Abcd

@JaimeGallego is that for me?

@JaimeGallego Might be true though

Jaime Gallego

5:19 PM

@Abcd Nope

That's for the topologer

Slereah

Maybe it's about the Clifford bundle

0celo7

and the picture seems to be about planetary orbits or Frenet-Seret geometry

bolbteppa

Putting spinors on manifolds in cartoon form, nice

Also the circular drawing indicates they are also compactifying dimensions ala string theory :p

Abcd

5:33 PM

In the determinant shouldn't there be -1 instead of 1?

0celo7

looks like it

what kind of crappy book is this?

Abcd

I apologise for asking apparently silly stuff but I am new to this topic so please please bear with me.

@0celo7 I know. Too many errors in the so called "solved examples"

0celo7

5:48 PM

@JohnRennie I need to talk about PCs

John Rennie

@0celo7 what's up?

0celo7

@JohnRennie I woke up with the crazy idea to build a PC

I need to see how much it will cost (approx) before I start doing specific research

John Rennie

For gaming?

0celo7

That would be the primary goal

but I definitely don't need overpriced gaming shit

I don't care about fancy lights and whatnot

John Rennie

Didn't we talk about this before?

bolbteppa

5:52 PM

@Abcd the $B$ in the problem has a minus sign, but in both parts of the solution it has a $+1$, so the $B$ in the problem is likely stated incorrectly.

John Rennie

As I recall my suggestion was to buy a second hand Dell and bung in a mofo video card.

0celo7

@JohnRennie Mhm. I need help with specifics. There are probably mobo compatibility issues

and the size of the case, PSU big enough for a mofo card

John Rennie

The size of the case may be an issue, but I doubt there will be compatibility issues and the Dell PSUs are generally pretty powerful.

0celo7

@JohnRennie Is future proofing the GPU a good idea?

John Rennie

Unless you're going for the ultimate gaming machine I suspect it's a lot simpler than you think.

0celo7

5:56 PM

"Ultimate gaming machine" sounds scary expensive.

But a GTX 1080 Ti is $720

Eek

John Rennie

@0celo7 I doubt you can. Things move so fast in the gaming world that future proofing is impossible.

0celo7

@JohnRennie Hmm.

Also, I only want 1080p. I might not need that huge of a GPU for that

John Rennie

$720 - Jesus!

If you pick the video card you want I can suggest a pc for it to go in.

Transcript for