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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.
 
@NovaliumCompany sadly not. You would still just have a potential difference of 15V across the whole cell.
 
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?
 
Are you specifying the dimensions of a hypothetical cell
Or just applying potential across a metal conductor
 
The former
I'm pretty sure a cell 0.01x1x1 should work with ~15V.
 
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
 
Yes
I'm asking would a cell 0.01x1x1 work properly with 15V, instead of making a 1x1x1 which will require 1500V.
 
7:10 AM
What are you running using these cells
It would depend on that?
 
An e-paper cell
 
No idea
 
Alright, it's not that important anyways
I'm making a 8mm x 5mm cell.
Thanks for the help anyways
 
 
1 hour later…
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.
 
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.
 
The fuel consumption of my car is $6.5\times10^{-8}\ \mathrm m^2$.
 
Imagine a stream of fuel, with that cross-section, running parallel to your car.
 
and my car is eating it like Pac Man
 
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.
 
morning
 
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 $\psi$
 
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
 
@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.
 
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
 
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.
 
11:46 AM
I wonder what's the Erdos number of Jesus
 
12:10 PM
Hey everyone
Anyone care to help me pls?
So no-one I presume?
 
@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.
 
12:25 PM
@Slereah I don't think Jesus ever co-authored any mathematics papers.
 
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
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
 
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.
 
2:41 PM
6
Q: Links to tinypic.com are about to become permanently broken

Ray ButterworthI 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 websitesJan 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 ¬¬
 
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?

turnipI 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...

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)

DavidTo 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

user113606This 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...

35
A: How does gravitational lensing account for Einstein's Cross?

Ron MaimonThe 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?

Ron MaimonSince 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?

John MThis 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...

 
40
Q: When is one 'Ready' to make Original Contributions to Mathematics?

TomThis 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 ...

 
3:57 PM
@bolbteppa that one also has broken tinypic links?
=P
 
4:08 PM
@EmilioPisanty Well, the link in that one has been dead since 2012 anyway per Qmechanic's comment
 
@ACuriousMind yeah, I know
I still think it's a problem, though
 
Sure, dead links are always a problem
 
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
 
Did SE not have native image upload back then or did the poster just prefer tinypic for inscrutable reasons?
 
@ACuriousMind not sure
doesn't look like it
42
A: Please allow image uploads directly onto the site

wafflesThanks 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.

image upload looks like it dates from 2010
the stack.imgur.com domain looks like it dates from 2011
alas, John M looks long gone and unlikely to return, so it's hard to confirm anything
ah, no
there's an explicit link on page 2 of the PF thread
 
 
1 hour later…
5:31 PM
Hm
Can every extended object Lagrangian be expressed as a field theory on a lower dimensional manifold
Hm, I'm not sure
Like say a system of two point particles with an interaction
Seems hard to describe that way
Though I think both fields and extended objects can be described by some section of a vector bundle on either the manifold or a submanifold
Point particles are just a section of some $\mathbb{R}^3$ bundle on $\mathbb{R}$
 
 
2 hours later…
7:10 PM
It's surprisingly hard to find a proper proof of Birkhoff's theorem
One with the real spherically symmetric metric
$$ds^2 = -e^{\lambda(r,t)} + e^{\nu(r,t)} + Y(r,t) d\Omega^2$$
Most of them assume $Y = r^2$ outright
 
Yeah it really gets huge
 
well space is huge, unfortunately
Many points
 
7:49 PM
@Slereah on a similar note, you should write up kk-reduction nicely
 
8:11 PM
7 Easy Hacks to Improve Your Math Skills http://karagila.org/2019/quick-hacks/

> 1. Get a graduate-level degree in mathematics!
5
 
Well he's not wrong
 
'4. Spend less time reading about quick hacks to improve whatever.'
 
Unfortunately the proper way is to sit down with a math book and work out the theorems
Much less glamorous
 

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