The h Bar

Slereah

1:00 PM

Print a nice label

Bam

It is fancy cider

just slap a label with a handsome peasant and some apples on it

John Duffield

@JohnRennie : I can back up what I say. See for example this : "I arrived at the result that the velocity of light is not to be regarded as independent of the gravitational potential. Thus the principle of the constancy of the velocity of light is incompatible with the equivalence hypothesis". I'm not making it up.

Secret

Here be numbers...

John Rennie

@ACuriousMind it is good answer isn't it, though I doubt Crothers will be impressed, assuming of course that he can understand it.

Secret

John Rennie

@Slereah that doesn't look good to me. It looks insufficiently filtered.

ACuriousMind

1:06 PM

@JohnRennie I like it because it starts by doing what so many questions we get on GR and QM ignore: What do words like "speed of a wave" actually mean in the non-classical setting?

John Duffield

@John Rennie : a gravitational field is a place where the speed of light varies. Einstein said it, and optical clocks say it. A gravitational wave is a gravitational-field-variation propagating through space. As it does so, the speed of light varies, which is why your local optical clocks go slower and those distant pulsars do not. So saying that this wave propagates at the speed of light is saying nothing.

Slereah

@JohnRennie Maybe I should filter with some fabric next time

ACuriousMind

Mathematicians are good at recognizing that we must first fix the meaning of words before we can talk about them. Physicists, amateurs as well as the trained ones, often fail at that, or purposefully sidestep it to make questions sound more profound than they are

John Rennie

@ACuriousMind Is the speed the norm of the four-wavevector?

Or do I mean wave-fourvector?

Slereah

I should do some online shopping before the second batch

I don't think I'm gonna find what I want at the shops

I looked high and low but even the kitchen utensils shops didn't have much useful

John Rennie

1:09 PM

@Slereah amazon.co.uk/s/…

Slereah

a bit much, perhaps

I just have a flat

Don't want something too big

- Height 58cm (1ft 10¾in)
- Diameter 27cm (10½in)

John Rennie

@Slereah 6 litres isn't that much ...

Slereah

Hm, I guess maybe the 6L one

We'll see

Secret

1

Q: Confusion about Conservation of energy

I getting a problem regarding law of conservation of energy. Suppose there is a hypothetical gravitational field which you switch on/off.you take an object to the opposite direction thus working and giving the object some potential energy. But keeping the object on h height from the ground level...

Slereah

I guess maybe some coffee filters might be enough to do the filtration

Secret

1:12 PM

Assume it is possibel for the sake of argument, more simply, it takes energy to switch off the gravitational field

(my attitude to unicorn type questions: Assume the unicorn exists, derive a contradiction, or estimate its dynamics using known models)

This is why it is rare for me to say something as nonsense, because there are too many ways to make sense of it

Slereah

I did see a big glass jug at one of the store, tho

Might be good

It even has a little faucet

I can drink my cider out of a jug like some hillbilly

Hm, what would be the hyperreal value of a series that doesn't converge or diverge

Like $(1,-1,1,-1,...)$

probably depends on the ultrafilter, I guess

Secret

I don't see how hyperreals will change the conclusion of that one, the standard part of this series is going to oscillate indefinitely between -1 and 1 anyway...?

Slereah

Because it is an element of the hyperreals

Hyperreals are just sequences of reals

Slereah

1:32 PM

Why won't the normies stop talking about hyperreals

We don't need your opinions on it

Danu

From this paper:

Secret

Fix 8 and the mathematicians will be happy

Slereah

That's what I'm working on

Well, the terms will still be divergent

But they will be correctly divergent

Secret

Actually for step 5, do anyone try to inivestigate if there are any patterns in the way the integrals diverge...?

We hate divergences, but perhaps the way they diverges might mean... something...?

Slereah

Yes, it's called power counting

John Rennie

1:39 PM

Shirley the fix for step 8 is to realise that you have an effective field theory that becomes inconsistent at some (hopefully high) energy level?

Slereah

I am serious. And don't call me Shirley.

My propertyyyy

John Rennie

The in jokes are the best jokes

Slereah

I don't think jokes from Airplane! count as injokes

ACuriousMind

@JohnRennie If I read Khavkine's answer right, he defines "speed" to be the norm of the vector tangent to the boundary of the domain of dependence, which is the "speed" of how the wavefront spreads, I guess.

I'm not sure what exactly you mean by "wave-four-vector"

Slereah

IIRC there's some theorem in Hawking that states that if some form of matter obeys the DEC the domain of dependance only grows at the speed of light tops

That's probably the theorem you want for gravitational wave speed

ACuriousMind

1:45 PM

Had you read the MO answer, you'd know that it already cites theorems that this speed is always the same for gravitational and electromagnetic waves, so gravitational waves propagate at the "speed of light".

Slereah

Reading is for nerds

John Rennie

@ACuriousMind I did read the answer and I even understood some of it.

Slereah

just pretend spacetime is toothpaste

ACuriousMind

@JohnRennie That comment was directed at @Slereah, not you

John Rennie

Just because you're paranoid doesn't mean that ACM isn't out to get you :-)

ACuriousMind

1:51 PM

lol, I vote for that to be the unofficial motto of the election

John Duffield

@Secret : I've answered the question. There's no mystery to it. The point to remember is that gravity is not a force in the Newtonian sense, in that it doesn't add any energy to the falling brick. Instead you add energy to the brick when you lift it up. Then turning off the field just doesn't matter.

Secret

user116211

@Secret inductive

Secret

@MAFIA36790 Are these two $A$ s different, as otherwise I don't see how $\mathbb{Z}^+ = D \cap S_{n+1}$?

Slereah

Danu

1:57 PM

Sport, there is a wii

LOL

Slereah

All you need baby

user116211

@Slereah WTH is physics ;/

Slereah

Star Wars

user116211

Math is not all about numerical analysis that you can make it all with calculator ;P

Danu

→ 3 messages moved to Trash

→ 1 message moved to Trash

Maybe it's not worth it to get rid of obsolete comments like that at the cost of producing those ^

ACuriousMind

2:03 PM

I'd say if the comments in question are just obsolete, leave them where they are, chat isn't a paragon of relevant comments to begin with :P

Slereah

yeah, people keep talking about physics

Instead of cider brewing

"although we cannot explicitly construct one, we can use Zorn's Lemma to prove their existence."

Yeah apparently it cannot be constructed at all

bloody axiom of choice

John Rennie

Your cider looks to me like a flocculated dispersion.
There - physics and cider.

Slereah

I tried going on the homebrewing stack exchange chat but there's nobody there

user116211

@Slereah All busy in ~~buying~~ making wine.

user116211

@Secret What do you think $\{1,2,\ldots,n\}$ is? Is it same as $\mathbb Z_{+}\,?$ ...

Secret

2:10 PM

Definitely not

(Why does Murnkres love to use the same symbols for completely different things...?)

Secret

Writing Strong Induction Principle as a C program:

user116211

@Secret What do you think set of all positive integers is...?

Slereah

"Consider once again the sequences a = 0; 1; 0; 1; ... and b = 1; 0; 1; 0; .... Multiplying pointwise still gives us the zero sequence. However, by property 4 of free ultrafilters, an ultrafilter U must contain either the set of even numbers or the set of odd numbers, but not both. Therefore one of the sequences a and b must be equivalent to 1 modulo U, and the other must be equivalent to 0 modulo U."

Danu

-1

Q: Majumder-Papetroue metric in multi black hole

What is the expression of velocity and acceleration of a neutral particle of mass m in a nearby black hole ?

general-relativity

This could be an interesting question

user116211

There is an easier proof of this theorem in Royden, BTW; @secret.

Danu

2:12 PM

The asker is SUPER bad at asking questions apparently, though.

Secret

@MAFIA36790 The proof by contradiction works fine for me, will check other books later to keep focused

user116211

@Secret He also basically applies method of contradiction too; but sure; check it later.

Secret

@MAFIA36790 Well, he bound it up to n for the definition of A, thus it is not necessary $\mathbb{Z}^+$, thus we still need to prove it as the proof goes. But I guess now I recognised the two A's are different, the proof flows for me

---
(This is a ramble) Writing Strong Induction Principle as a C program:

(still typing lol)

user116211

@Secret For this, you need the Archimedian Principle....

Slereah

Archimedean principle is good for the weak archimedean fields

user116211

2:21 PM

What? What? Googling weak Archimedian fields...

Slereah

I am only using "weak" to denote my disdain for archimedean fields

Hyperreal all the way baby

Secret

S_0="emptyset";
for i=1
{
n=i;
A[i]=S_{i-1};
A[i+1]=i;
i++;
}

user116211

WTH!

user116211

I got a philosophy book ._.

Secret

(It seems my C programming is very rusty due to prolonged disuse)

user116211

2:23 PM

I mean philosophical logic book that mentioned weak Archimedian field ....

Secret

But basically what I want to ramble is that the strong induction property start with a seed, then absorbs successors into a set continuously by induction, thus the set must grow into the positive integers

John Duffield

@Danu : LOL, this answer is obviously wrong. When it isn't.

user228700

@MAFIA36790: Given the state of the education system in India, I was wondering exactly how you came to be passionate about physics. Minutephysics is my reason and if any amateur is passing by, I highly recommend his videos:(although they are a bit fast, what with him having to do all the explanation in one minute and all):

user228700

Is it Better to Walk or Run in the Rain?

►

user116211

@KaumudiHarikumar Star Wars ;P

Secret

2:32 PM

Contradiction is convinced, now to see if there's a direct proof

user228700

(This video isn't exactly about physics but it's absolutely wonderful anyway)

user228700

@MAFIA36790 Oh :-)

Secret

user218912

my reason to study physics was @0celo7, but now he doesn't like physics so it's depressing for me.

ACuriousMind

Why the hell do I have about a dozen ethernet cables?! Maybe I should've looked in this cupboard before buying new ones...

Danu

2:34 PM

@IceLord That's terrible motivation, if you're serious :P

Secret

My reason to study physics is because I want to realise scifi. Only QM I dared to say that I will still study it even if it does not help me realise scifi

user218912

@Danu I'm 100% serious.

user3183724

Stupid technical question. Say I have some power in terms of mega photons per second, how would I write this? MPhotons/s ? I understand that photons have a frequency dependent energy, but in the context it is clear what its frequency is

user218912

why is it terrible motivation?

Danu

@IceLord You decided to study a topic because someone else was interested in it?!

user228700

2:35 PM

@JohnDuffield: In reply to your request to find a TED talk about physics that truly inspired me, I must admit that I've never watched very many talks on physics in particular because most of them are either too simple or too complicated. I was talking about all the other types of talks.

Danu

That doesn't sound like a questionable idea to you?

user116211

But I'm serious about maths more than physics; thanks to Bourbaki; he really motivated me ;P

user218912

@Danu nah it was more like, I wanted to study it but didn't really know where to begin or what to do, before @0celo7 helped me.

user228700

@MAFIA36790 Ah, I see...

Sanya

@user3183724 hmm, that's not nice because you don't know how much power a photon has as long as you don't know the wavelength/frequency - just write the power down, why not?

Danu

2:36 PM

@IceLord Then your motivation should be pretty much unchanged by 0celo7 jumping ship, no?

user3183724

@Sanya well, because we are talking about 10^6 microwave photons, so you get into very ugly energies

Sanya

@user3183724 ??? I don't see the point

user116211

Is it a one-liner answer:

user116211

0

A: How do i calculate the force acting on a body when it hits the ground from free fall?

This is bcoz mass of body do not effect the gravity

Sanya

anyway, as long as it is not for publication, I think most people will understand the MPhotons notation

user116211

2:38 PM

?

user3183724

@Sanya it is, I am afraid

user218912

@Danu well, my motivation hasn't changed but I am kind of sad about it.

Secret

@MAFIA36790 It's a one liner that is not even relevant to the OP's question

Sanya

@user3183724 then I'd stick to energies and only mention the number of photons in the text

Danu

@IceLord Oh well...

Sanya

2:40 PM

@MAFIA36790 bcoz sense this makes!#

user218912

@Danu same for you xD

user3183724

@Sanya maybe it helps if I motivate it a bit. We start from the Mollow triplet of a single two level system, which has a clean format: you know that (without pure dephasing and nonradiative decay) the center peak is 1 photon of the energy used to excite the two level system. So you have a power spectral density with a y-axis in number of photons. If I then integrate this, you get photons per second.

I need to also show the power spectral density, which is always done in photons in this field. So then it isn't consistent to write the integrated version in an actual power instead of photons per second

user218912

I am losing all my physics friends to math.

user116211

@IceLord Should I say good ;P

Secret

nytimes.com/2016/09/27/science/…

Sanya

2:43 PM

@user3183724 what's your supervisor's idea on it?

2physics

hello everybody.

user3183724

@Sanya so the way I see it can I write the PSD in 10^-25 joules or something, or 10^-6 eV, but then I diverge from the standard there. Or, I get the weird powers. My supervisor told me to look at what is typically done in other papers, but I can't find any that integrate PSDs, not from our field

Sanya

@user3183724 :| maybe post it on the main site to be honest

2physics

how do you get the papers you need? do you pay for everyone of them??

user3183724

@Sanya Hmm, yeah, although its such a non-interesting thing..

Sanya

2:45 PM

@2physics university licences

ACuriousMind

What is this for a type of connector?

Sanya

@user3183724 it is, but it is a relevant question that you have done research on, about standard physics notation

ACuriousMind

the other end is USB

2physics

@Sanya what about when you are not a student or not at school?

ACuriousMind

I have no idea where I got this

Sanya

2:46 PM

So I think it's valid

@2physics sucks :< the next university library and their wifi?

Secret

The residential computer nerd is asleep, might have to left that a few hours later

Sanya

@ACuriousMind it's for connection to e.g. a printer

user3183724

@Sanya Okay, that is true. I'll write up a post, thanks! Also as an aside, it is already ugly in terms of units anyway.. The x-axis in in units of atto weber^2 per Hz..

Sanya

it has a name that I have forgotten

John Duffield

@KaumudiHarikumar : there's plenty of inspirational material out there. I think though that when you learn more, you realise that some material is good stuff, and other material isn't.

ACuriousMind

2:47 PM

@Sanya Hmmm...that makes sense

My printer is currently connected by WiFi, so it makes sense I'd have the cable from that lying around

Sanya

posh kid you are ... an own printer as a student :o

ACuriousMind

It's not particularly fancy, but it does its job and I don't have to go to the university every time I need to print something, I don't think that's posh :P

Sanya

@user3183724 I hope there's someone from the optics community who's better qualified then me :)

@ACuriousMind ;) even though a wifi connection is cool, I've never seen that yet

ACuriousMind

Cable connection would be rather annoying since my flatmate also used the printer

And the cheap standard router certainly doesn't have a way to connect a printer to it by cable

Sanya

that's an argument

user218912

2:53 PM

@JohnDuffield when will you learn enough to make the distinction?

2physics

@Sanya and when there isn't any "next university" which you do study at?

Sanya

@2physics hmm, here university libraries are public

so I'd expect to somehow gain access to the wifi :|

John Duffield

@IceLord : I have. That's why we have such interesting discussions here.

0celo7

@ACuriousMind Ok I had a weird dream, why is a global section of a vector bundle diffeomorphic to the base?

Secret

Short question, is it possible to show/prove that without the cancellation property we can only prove 0.0=0 but not 0.x=0? This is because in a typical proof of 0x.0, we often get to the result 0.x=0.x+0.x, and we typically either add the additive inverse for 0.x (for rings) or simply use the cancellation property (for integral domains) to get rid of 0.x to get the result?

2physics

3:05 PM

alright. here 1- most of the universities don't have access to the famous publishers. 2- you have to be a student of a university to be able to use its services as well as its library and wifi.

Secret

I knew one can prove 0.0=0 by 0=1.0=(0+1).0=0.0+0=0.0

ACuriousMind

@0celo7 Because it's a smooth right inverse to the projection, and when you restrict the domain of the projection to the image of the section, it becomes a left inverse as well.

0celo7

@ACuriousMind Good. That's how I proved it in the dream, too.

ACuriousMind

I'm still amazed that you do coherent math in your dreams

user116211

Now this is what is left in my bucket: prove maths correctly in dream....

0celo7

3:07 PM

@ACuriousMind Well, it was bugging me last night when I went to bed, so I was thinking about it

Maybe I proved it right before I feel asleep, but all I know is I woke up 15 mins ago and knew the proof.

Newmann

@0celo7 I just want to say hello. I am reading the message only... . By the way she is here (and her close friend ice...) ;)

0celo7

I know she is here

ACuriousMind

@0celo7 I dreamt I was married with three kids and angry because they all dropped out of school to do...something undefined, which was definitely not what I was thinking about when I went to bed!

Thereafter the dream morphed into random sequences with even less sense to them

user116211

@Newmann Who is she O.o

Secret

Last night I dreamt about a function that takes in the emptyset as an argument and spits out a union of 3 intervals

user116211

3:09 PM

Last night I couldn't sleep....

0celo7

@ACuriousMind Probably something useless. My greatest fear when I have children

I'm gonna get a Döner today :]

ACuriousMind

3:21 PM

@0celo7 bon appetit!

...I also have accumulated like 7 chargers, I should open an electrionics store

user116211

@ACuriousMind Why not sell them at Amazon or Ebay?

0celo7

@ACuriousMind Does second countable mean I can take any basis to be countable, or just that there exists a countable basis?

I think it's the second one, so I have to be more careful in this one proof

I'm trying to prove that a manifold has a countable basis of precompact open sets.

I think one should cover with precompact balls, then show that each ball has a countable basis.

Newmann

@0celo7 I hope that @ACuriousMind just gives an simple answer, and not ask a mass of imaginary additional questions (instead of answering) ;)

0celo7

Then a countable union of countable sets is countable, so that works.

@Newmann She always does that...

ACuriousMind

@0celo7 Don't know, I don't care about second countability

0celo7

3:29 PM

@ACuriousMind ...how do you prove anything in diff geo without it?

ACuriousMind

@Newmann The "additional questions" I ask are intended to narrow down questions sufficiently so that a precise and correct answer can be given. Vague questions where it is unclear whether a given answer actually answers them are of use to no one.

0celo7

@ACuriousMind Why do I distinctly remember you telling me that a countable union of countable sets is uncountable?

that's not true

ACuriousMind

@0celo7 I can't remember ever explicitly invoking it. I would also remind you that I don't do much differential geometry in the sense that you probably mean

Danu

> Stokes doe

0celo7

Aug 11 '15 at 1:49, by ACuriousMind

@0celo7 Oh, why didn't you say that earlier! A set is countable if there is a bijection from it to the natural numbers (i.e. it has "as many elements as there are natural numbers")

oh

2015

ACuriousMind

3:33 PM

@0celo7 In the absence of choice, it can even happen that the countable union of finite sets is uncountable

0celo7

whoa whoa whoa

countable choice or uncountable choice?

ACuriousMind

You probably remember me saying that from one of the times I tried to convince you to accept choice

0celo7

I accept countable choice.

ACuriousMind

@0celo7 I am not enough of a logician to appreciate these finer distinctions. Let's just say it can happen when the negation of the axiom of choice is true.

0celo7

@ACuriousMind You use it every time you use a partition of unity.

Danu

3:34 PM

@ACuriousMind also for the sake of other geometry---you need partitions of unity a lot in sheaf cohomology

ACuriousMind

That doesn't mean I have to care about what exactly "second-countable" means, it's enough to know it allows partitions of unity!

Danu

For instance in proving de Rham's theorem (via sheaves)

Yeah, sure

@0celo7 You can pass to a countable one

So you don't need care.

0celo7

@Danu Basic Mayer-Vietoris needs PoU.

ACuriousMind

I always say "As manifolds allow partitions of unity", I couldn't care less why exactly that is :P

Danu

@0celo7 Lol no

The Mayer-Vietoris sequence is defined on arbitrary topological spaces

0celo7

3:37 PM

Danu, you want things to be smooth.

Danu

@ACuriousMind That's an acceptable, pragmatic stance.

@0celo7 Yeah, but I also want correct statements.

0celo7

You need a PoU to make sure things are smooth on the intersection of your sets $U$ and $V$.

ACuriousMind

@0celo7 MV is essentially equivalent to the long exact homology sequence, so it works in all (co)homology theories

Danu

MV doesn't need partitions of unity

0celo7

For fuck's sake.

I'm clearly talking about de Rham cohomology.

Danu

3:37 PM

In particular MV is essentially an axiom of cohomology

TROLLKILLER

Would a question "what are the most interesting open problems in string theory?" be closed?

Danu

@0celo7 I view De Rham as mimicking singular cohomology

@TROLLKILLER yes.

ACuriousMind

@TROLLKILLER Yes, because it is open-ended and hence too broad

Also, "most interesting" is opinion-based

0celo7

Wait.

We're talking about different things.

Are you talking about the LES?

TROLLKILLER

what if i ask, what are the top 10 most prominent open problems in string theory?

Danu

3:39 PM

@0celo7 Yeah, of course.

or rather the SES

Mayer–Vietoris sequence

In mathematics, particularly algebraic topology and homology theory, the Mayer–Vietoris sequence is an algebraic tool to help compute algebraic invariants of topological spaces, known as their homology and cohomology groups. The result is due to two Austrian mathematicians, Walther Mayer and Leopold Vietoris. The method consists of splitting a space into subspaces, for which the homology or cohomology groups may be easier to compute. The sequence relates the (co)homology groups of the space to the (co)homology groups of the subspaces. It is a natural long exact sequence, whose entries are the ...

0celo7

Bott & Tu call the SES the MV sequence. To show that's exact in dR cohomology, you need a PoU.

ACuriousMind

@TROLLKILLER Still opinion based, "most prominent" isn't an objective criterion. Pick a particular goal and ask what the current obstacles to achieving it are to get a question that asks for open problems, but is narrow enough to allow objectively correct answers.

0celo7

$0\to\Omega^\bullet(M)\to\Omega^\bullet(U)\oplus\Omega^\bullet(V)\to \Omega^\bullet (U\cap V)\to 0$.

Danu

@0celo7 Sure---but I happily apply MV in singular cohomology to a manifold as a topological space.

TROLLKILLER

most famous?

0celo7

3:41 PM

@Danu Agreed.

ACuriousMind

@TROLLKILLER Picking synonyms doesn't actually change the question :P

Danu

I learned yesterday how to prove the de Rham theorem nicely using sheaf theory---it also uses PoU to prove that the sheaves of differential $p$-forms have no cohomology in degree $\geq 1$.

Once you have this acyclicity it's just an immediate consequence of the existence of the resolution $\Bbb R\to \mathcal A^0\to \mathcal A^1\to\dots$

ACuriousMind

@Danu It's a general fact that sheaves with a partition of unity ("fine sheaves") have vanishing higher cohomologies

Danu

@ACuriousMind That's the point!

ACuriousMind

I hope it proved that general statement ;)

Danu

3:43 PM

That's exactly what I was referencing, yes.

ACuriousMind

Okay, nice

0celo7

Meanwhile, I am trying to figure out why one could or should define manifolds to be separable.

Danu

Though I must admit that I didn't learn a proof of that statement---I've seen in applied in the context of Riemann surfaces to the sheaves of forms of type $(1,0), (0,1)$ etc.

So it seemed pretty obvious to me that it can be generalized.

So I was satisfied with the idea without proof :)

Secret

Once again, I gone hyperdrive at the 0x=0 proof:

1

Q: It is possible to show/prove that the cancellation property is necessary to prove $0x=0$ for $x\not\in \mathbb{Z}^+ \cup \{0\}$?

For any algebraic structures with additive and multiplicative identity, and at least one sided distributive law holds, one can easily prove that 0 is an absorber, i.e. $0x=0$ for $x=\{0,1\}$ as follows: $$0\cdot 1=0 \tag{Multiplicative identity}$$ and \begin{align} 0 &=0\cdot 1 & (\text{Multipli...

abstract-algebra proof-writing

0celo7

@ACuriousMind @Danu Did you know that one needs at most $n+1$ charts to cover an $n$-manifold?

ACuriousMind

3:47 PM

@Danu I have a proof for general paracompact locally ringed spaces from my algebraic geometry course, one of the more interesting things we did. As an exercise.

TROLLKILLER

thats easy

Danu

@0celo7 I'm skeptical of this claim---how is it proven?

TROLLKILLER

ocelol : what about 1000 holed torus?

0celo7

@Danu "topological dimension theory." I don't know the proof

Danu

I have seen an exercise which already suggests a lower bound of $n+1$ (of course for $n=1$ this is optimal)

0celo7

3:50 PM

cf. Greub-Halperin-Vanstone p. 72

Danu

Which volume?

0celo7

1

Danu

Your page numbering differs from mine

0celo7

Seems like something Mike would know

@Danu I am quoting Kolár et al.

TROLLKILLER

proof : math.stackexchange.com/questions/92881/…

Danu

3:55 PM

@TROLLKILLER I guess that hides all the hard work in the quoted theorem.

dmckee

@ACuriousMind That's a USB type A connector. The one you call "USB" in your next comment is a USB type B. The one you put in your phone is a micro type B, but everyone just calls it micro because there is no smaller version of the type A.

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