The h Bar

6:19 AM

@JohnRennie I have a really crappy idea about something. If 15V are required for a really small cell, and I need 1500V for my big cell, can I just hook many small conducting plates on both sides of my big cell, each with ~15V across them? You get the idea.

John Rennie

@NovaliumCompany sadly not. You would still just have a potential difference of 15V across the whole cell.

Novalium Company

6:54 AM

@JohnRennie Well, that's a bit... weird. What if I just make 100 small cells, glue them together and put 15V across each one?

nvm I think I get it

What if I make a cell with y = 0.01 cm and x and z = 1 cm, and put 15V across the 0.01 cm part?

I'll have a big but thin cell, which should work with 15V?

Avnish Kabaj

Are you specifying the dimensions of a hypothetical cell

Or just applying potential across a metal conductor

Novalium Company

The former

I'm pretty sure a cell 0.01x1x1 should work with ~15V.

Avnish Kabaj

I mean

If you've defined a cell like that

Then we can't argue with that

Are you asking is it possible to make a cell in real lofe

Novalium Company

Yes

I'm asking would a cell 0.01x1x1 work properly with 15V, instead of making a 1x1x1 which will require 1500V.

Avnish Kabaj

7:10 AM

What are you running using these cells

It would depend on that?

Novalium Company

An e-paper cell

Avnish Kabaj

No idea

Novalium Company

Alright, it's not that important anyways

I'm making a 8mm x 5mm cell.

Thanks for the help anyways

Loong

8:41 AM

> This is the power of dimensional analysis. We can get answers to questions, even if we do not understand the underlying principles of the problem, merely by observing the physical units of the quantities under inspection.

I think this is not the power but the main problem of dimensional analysis.

PM 2Ring

9:31 AM

@Loong Ok, so you get a few false positives. But at least it doesn't give you false negatives.

But speaking of dimensional analysis abuse, I like to quote fuel consumption in picohectares instead of litres per 100 km.

Loong

The fuel consumption of my car is $6.5\times10^{-8}\ \mathrm m^2$.

PM 2Ring

Imagine a stream of fuel, with that cross-section, running parallel to your car.

Loong

and my car is eating it like Pac Man

PM 2Ring

9:46 AM

Americans may find it hard to relate to this conversation, since they talk about fuel consumption in miles per gallon, and I guess seeing that as an inverse area is a bit of a stretch. Whereas volume / distance is virtually inviting you to do the division and obtain an area.

Slereah

morning

Slereah

10:12 AM

Trying to write an article on symmetries of the Lagrangian, but it's mildly annoying as $\phi$ can be both the field or the chart atlas

Gonna have to go with $\psi$

Secret

10:40 AM

Really really really long line:

Take the union of the following:

$\alpha \times [0,1)$ where $\alpha \in \mathbf{On}$
This line is SO LONG that there's a point which all increasing sequences of any ordinal length will not converge to it
Probably a nice impression on how large Cantor's Absolute Infinite is

PM 2Ring

@Secret I think you'd enjoy Rudy Rucker's Infinity & the Mind. I haven't read that edition, I have the 1st edition, in paperback.

Secret

Well, I actually almost finished reading the 3rd edition

I am near the excursion section

In fact, it is that book that inspired me to think about Cantor's Absolute Infinite

before then, I have no idea how to comprehend it and the more general philosophical and mystical concept called the Absolute

PM 2Ring

10:58 AM

@Secret Ah, ok. :)

I should probably re-read it. It's been a few years, and my memory isn't as good as it was back then.

Slereah

11:46 AM

lix.polytechnique.fr/Labo/Ilan.Vardi/jesus.html

I wonder what's the Erdos number of Jesus

Abhi

12:10 PM

Hey everyone

Anyone care to help me pls?

So no-one I presume?

PM 2Ring

@Abhi If you have a question, you should ask it. Then people who can (& who want to) help you will respond. You shouldn't expect people to commit to helping you when they have no idea what your problem is.

PM 2Ring

12:25 PM

@Slereah I don't think Jesus ever co-authored any mathematics papers.

Slereah

Well he was acknowledged apparently

Does that count

From looking into those authors, I conclude that God has an Erdos number of at most 4

lix.polytechnique.fr/Labo/Ilan.Vardi/pi-exists.html

proof that $\pi$ exists

ABC

1:18 PM

Hi guys, there are anyone that can help me?

Hi have a little fast problem about mechanics

PM 2Ring

1:47 PM

2 hours ago, by PM 2Ring

@Abhi If you have a question, you should ask it. Then people who can (& who want to) help you will respond. You shouldn't expect people to commit to helping you when they have no idea what your problem is.

Emilio Pisanty

2:41 PM

6

Q: Links to tinypic.com are about to become permanently broken

I notice that there is an image link that no longer works at the end of this recently updated page in Meta.SE. I suspect that this is only one example of many items that have links to tinypic.com. Can anything be done about this situation before that site shuts down? TinyPic is shutting do...

Gotta be quick; it looks like it's going to need an army of manual editors: August 26, 2019 - hosted images will no longer be viewable on 3rd party websites — Jan Doggen 1 hour ago

SEDE currently lists 21 posts with tinypic links

some of which have already been edited by Jan Doggen

we should probably get on it

¬¬ brilliant, a bunch of those links are by Ron Maimon and the images look unrecoverable ¬¬

Emilio Pisanty

3:36 PM

@JohnRennie the video link in this thread is also on the queue for the chopping block, I reckon you have a higher stake in recovering it

152

Q: Why do shadows from the sun join each other when near enough?

I was laying on my bed, reading a book when the sun shone through the windows on my left. I happened to look at the wall on my right and noticed this very strange effect. The shadow of my elbow, when near the pages of the book, joined up with the shadow of the book even though I wasn't physically...

visible-light everyday-life diffraction shadow

ah, speak of the devil =P

I can't get to that video at all

dunno if it's recoverable

@EmilioPisanty OK, most of them are now fixed, the remaining ones look unrecoverable:

0

A: Harmonic oscillator :Two masses are attached to one unfixed spring from both sides (vertically)

To help you with section a: Your approach in writing the differential equation for the two positions (http://oi62.tinypic.com/dfx6yq.jpg) is correct. Since we know gravity won't affect the resonant frequency, I'll ignore gravity when writing the equations. $$\ddot{y_1} = -(k/m_1)(y_1-y_2)$$ $$...

0

Q: Compressed length of a moving body

This question is on behalf of someone else without access to a computer so any further clarification or responses may be delayed. The question comes in the form of photos of the original questions as they were sent to me. I would transcribe them to text buy I am unable to write the pictures/diagr...

special-relativity

35

A: How does gravitational lensing account for Einstein's Cross?

The middle galaxy in Einstein's cross has an elliptical mass distribution which is wider in the direction of the short leg of the cross (originally, this said long leg), with a center of mass where you see the galaxy. The object is slightly to the right of the center of the ellipse, in the direct...

14

A: How to derive addition of velocities without the Lorentz transformation?

Since the Lorentz transformations are a consequence of the postulate of constancy of the speed of light, together with some homogeneity and parallel postulates, it is a little difficult to make precise the request for a Lorentz-transformation free demonstration. But I will interpret the question...

24

A: What are the precise statements by Shouryya Ray of particle dynamics problems posed by Newton which this news article claims have been solved?

This thread(physicsforums.com) contains a link to Shouryya Ray's poster, in which he presents his results. So the problem is to find the trajectory of a particle under influence of gravity and quadratic air resistance. The governing equations, as they appear on the poster: $$ \dot u(t) + \alpha...

bolbteppa

40

Q: When is one 'Ready' to make Original Contributions to Mathematics?

This is quite a philosophical, soft question which can be moved if necessary. So, basically I started my PhD 9 months ago and have thrown myself into learning more mathematics and found this an enjoyable and rewarding experience. However, I have come to realise how much further I still have to ...

soft-question

Emilio Pisanty

3:57 PM

@bolbteppa that one also has broken tinypic links?

=P

ACuriousMind

4:08 PM

@EmilioPisanty Well, the link in that one has been dead since 2012 anyway per Qmechanic's comment

Emilio Pisanty

@ACuriousMind yeah, I know

I still think it's a problem, though

ACuriousMind

Sure, dead links are always a problem

Emilio Pisanty

I reckon it's this picture, though

with pretty high certainty

there's no tinypic link in the source of the physicsforums thread

and that's the only explicit .jpg link

I suspect John M took that link from jugend-forscht-sachsen and uploaded it to a "safer" permanent hosting on tinypic

ACuriousMind

Did SE not have native image upload back then or did the poster just prefer tinypic for inscrutable reasons?

Emilio Pisanty

@ACuriousMind not sure

doesn't look like it

42

A: Please allow image uploads directly onto the site

Thanks to our awesome friends at http://imgur.com we now have built in image uploads, via the standard image upload button. This will be deployed to all our sites in the next few days, for the time being you can test on meta. More details on the blog: New Image Upload Support.