Search found 114 matches

by ST47
Fri Jul 19, 2013 4:12 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1240: "Quantum Mechanics"
Replies: 201
Views: 46296

Re: 1240: "Quantum Mechanics"

CocoaNutCakery wrote:Te sheer level of militant atheism in this thread is absurd.


And there's another phrase that you can safely ignore!
by ST47
Mon Oct 31, 2011 1:03 am UTC
Forum: Mathematics
Topic: Average circle intersection - an integral
Replies: 12
Views: 2295

Re: Average circle intersection - an integral

Make sure you weight it. There isn't an equal probability of x=0.1 and x=0.9, the latter is much more likely. Never mind, you did that. Those are both pretty complicated, but wolfram alpha will work them out for you (click show steps if they aren't already expanded): First term: http://www3.wolframa...
by ST47
Sat Oct 29, 2011 10:25 pm UTC
Forum: Coding
Topic: Need help with simple program.
Replies: 7
Views: 1965

Re: Need help with simple program.

Try sprintf(). That's certainly the "basics".
by ST47
Fri Sep 30, 2011 4:51 am UTC
Forum: Hardware
Topic: What's the Big Deal with Alienware®?
Replies: 23
Views: 10878

Re: What's the Big Deal with Alienware®?

A research lab I work in recently bought an alienware laptop for basically a portable 3D/LabVIEW/Haptics rig. I offered a very similar rig for a fraction of the price, and was overruled because of the Alienware accidental damage protection, which no one else is crazy enough to offer (and apparently ...
by ST47
Fri Sep 23, 2011 6:22 pm UTC
Forum: Science
Topic: Well, this could change things (neutrinos)
Replies: 289
Views: 45760

Re: Well, this could change things

They KNOW they haven't disproved physics. In SN1987A, a pulse of neutrinos arrived several hours before the light was detected. SN1987A is located 168,000 light years from Earth. If neutrinos travel at 40,001c/40,000, then the neutrinos from SN1987A should have arrived 4 years before they did. Your...
by ST47
Fri Jul 29, 2011 4:21 am UTC
Forum: Mathematics
Topic: 4 color theorem with multiple regions
Replies: 12
Views: 2061

Re: 4 color theorem with multiple regions

This may be a bit off-topic, but is there a generalization for maps on manifolds other that a sphere? No. Some specific cases can be made. For example, a map on a sphere can be transformed to a map on a plane, and so it will take at most four colors in either case. A torus, however, will require 7....
by ST47
Sat May 28, 2011 3:23 am UTC
Forum: Mathematics
Topic: A criminal hides in a room with 99 innocent people...
Replies: 13
Views: 4526

Re: A criminal hides in a room with 99 innocent people...

I followed all the probability here so far, but I'm not sure what to make of this: What if, instead of gathering the evidence before making rash decisions, we decide to have a good old-fashioned witch hunt, test people until we get a positive, and then burn that person at the stake. What is the prob...
by ST47
Thu May 26, 2011 4:19 am UTC
Forum: School
Topic: Saying "gay" is now illegal at school?
Replies: 6
Views: 4289

Re: Saying "gay" is now illegal at school?

Are we actually going to be calling it "bulling" now? Because thats...cows...and not for children...
by ST47
Mon May 23, 2011 2:47 am UTC
Forum: Mathematics
Topic: alternative mathematics
Replies: 128
Views: 15415

Re: alternative mathematics

My reactions to this thread: Oh, its this guy again... From this and his previous thread, he seems to have poor English and is using diagrams to communicate worse Fixed that for you. I've heard rumours of a math professor that once proved something significant and then went mad and keeps posting ab...
by ST47
Sun May 22, 2011 10:28 pm UTC
Forum: Science
Topic: colour of the sky
Replies: 28
Views: 9854

Re: colour of the sky

To bed pedantic, it isn't exactly correct. The Sun is not white. It isn't nearly hot enough at its surface. Yellow is what you have left over when you remove blue from white, but the Sun still emits plenty of blue anyway, just not enough to fully balance the lower wavelengths. Of course the sun is ...
by ST47
Wed May 11, 2011 7:00 pm UTC
Forum: Coding
Topic: PHP Encryption Class - Any flaws?
Replies: 6
Views: 3093

Re: PHP Encryption Class - Any flaws?

And to nitpick: That's what a for loop is for :wink: I know, but I wanted it to always run at least once (something a for loop doesn't do). Sure, with it now it will always run 5000 times, but if someone edited the code and reduced that number to 0, it would still run once. I don't know much about ...
by ST47
Wed May 11, 2011 6:35 pm UTC
Forum: Mathematics
Topic: Formal mathematical definition of area
Replies: 10
Views: 2307

Re: Formal mathematical definition of area

That would be the integral of the prepositional function, taken to have value 0 outside the shape, and 1 inside, over the plane. Of course, no one uses this in practice. Far more useful would be to have a function that gives the border of the shape. If the boundary (which is defined as the set of po...
by ST47
Tue May 10, 2011 2:08 pm UTC
Forum: Coding
Topic: Macro Ethics
Replies: 17
Views: 2976

Re: Macro Ethics

WarDaft wrote:
Yakk wrote:I want strong static Hindley–Milner ducktyping! Quack.


So, basically, Haskell?


There are ducks in Haskell?

Great, another language to learn.
by ST47
Sun Apr 24, 2011 3:06 am UTC
Forum: Science
Topic: Unification of forces in early universe
Replies: 13
Views: 2894

Re: Unification of forces in early universe

So, there's a field description and a particle description of both weak and EM. If you want to talk about weak in terms of W+, W- and Z, then you should compare to the chatter about EM in terms of photons. They are analogous. Ok, I understand what you mean there, so it's time for some more reading....
by ST47
Sun Apr 24, 2011 2:39 am UTC
Forum: Science
Topic: Unification of forces in early universe
Replies: 13
Views: 2894

Re: Unification of forces in early universe

I am an Actual Physicist! The gravitational and em forces very much do not have scalar potentials. The potential for electromagnetism is the 4-vector A. Alternatively, you can consider it to be a 1-form. The differential forms version of e&m is much neater. Then, the field strength tensor is F=...
by ST47
Sun Apr 24, 2011 2:21 am UTC
Forum: Coding
Topic: Python question
Replies: 9
Views: 1855

Re: Python question

No, you need to check that the evaluation process doesn't do anything bad, step by step. E.g. you don't want to eval shutil.rmtree('/') ; that would be bad. Okay, I'll take your word for it. another related question: I got the initial question answered and I wanted to make a function that will tell...
by ST47
Sun Apr 24, 2011 1:41 am UTC
Forum: Science
Topic: Unification of forces in early universe
Replies: 13
Views: 2894

Re: Unification of forces in early universe

I'm going to chime in and hope that an Actual Physicist can clear some things up for me on a similar topic. See, the gravitational and electromagnetic forces appear to be described by a scalar potential field. The gradient of this is a vector field, and this multiplied by a relevant 'charge' (mass o...
by ST47
Wed Mar 23, 2011 5:49 am UTC
Forum: Coding
Topic: Perl problem, change PP: first occurrence to HL:
Replies: 16
Views: 2118

Re: Perl problem, change PP: first occurrence to HL:

You could do it with a single regex replacement by: $filename = "input.txt"; open (FILE,"<$filename"); @fileinput=<FILE>; $fileinput=join("\n", @fileinput); $fileinput=~s/PP:/HL:/; which will only change the first PP: it finds to HL:, as your example says. You can, inci...
by ST47
Wed Jan 19, 2011 5:07 am UTC
Forum: Individual XKCD Comic Threads
Topic: 0849: "Complex Conjugate"
Replies: 96
Views: 24864

Re: 0849: "Complex Conjugate"

Google it.

Alternately, if you have a complex number a+bi, the complex conjugate is a-bi. So, multiplying these together gives (a^2+abi-abi-b^2*i*2)=(a^2+b^2). Which, as you'll note, happens to be real.
Therefore, shit just got real.
by ST47
Thu Jan 13, 2011 4:51 am UTC
Forum: School
Topic: Looking for good textbooks on critical thinking
Replies: 21
Views: 3655

Re: Looking for good textbooks on critical thinking

Science. All of science.
by ST47
Sun Jan 09, 2011 5:01 am UTC
Forum: Coding
Topic: C compiler for the PIC16 series microcontroller
Replies: 7
Views: 1844

Re: C compiler for the PIC16 series microcontroller

You mean like this: http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en542849 The free version works fine, the paid version has better optimization. I TA a class where we throw a PIC chip and this compiler at a bunch of freshmen and tell them to do somethi...
by ST47
Fri Jan 07, 2011 6:50 am UTC
Forum: Science
Topic: Aluminum foil in a microwave - when should you be worried?
Replies: 24
Views: 14151

Re: Aluminum foil in a microwave - when should you be worrie

Sparks mean some sort of electrical discharge, which probably means something is going to get oxidized and that looks ugly. It can also probably damage the metal in the front door, which as we all know is the thing that protects you from being cooked. In addition, covering your food entirely in foil...
by ST47
Sun Sep 27, 2009 5:18 am UTC
Forum: Science
Topic: Electric field inside a hollow sphere
Replies: 7
Views: 9909

Re: Electric field inside a hollow sphere

Question was copied n pasted.

So could perhaps the charges redistribute? By my calculations, that's a total charge of 8.042*10^-9 C over a volume of 3.28*10^-3 m^3 for charge density of 2.45*10^-6 C/m^3...which leads to lots of calculus which we aren't supposed to have to do...
by ST47
Sun Sep 27, 2009 4:29 am UTC
Forum: Science
Topic: Electric field inside a hollow sphere
Replies: 7
Views: 9909

Electric field inside a hollow sphere

So I'm having trouble conceptually understanding this problem: A hollow metal sphere has 6 cm and 10 cm inner and outer radii, respectively. The surface charge density on the inside surface is -100nC/m^2. The surface charge density on the exterior surface is +100nC/m^2. Find the strength and directi...
by ST47
Thu Sep 24, 2009 4:14 am UTC
Forum: Science
Topic: Diluting 18M Sulfuric acid to 6M in a volumetric flask?
Replies: 23
Views: 6221

Re: Diluting 18M Sulfuric acid to 6M in a volumetric flask?

I'm pretty sure it's the other way around. Say it in an accent so 'waata' rhymes with 'oughta'.

And by pretty sure, I mean absolutely sure. That way water splashes on you and you get wet rather than acid splashes on you and you get burned.
by ST47
Sun Aug 30, 2009 6:15 am UTC
Forum: Science
Topic: Faster Than Light Theory
Replies: 18
Views: 1512

Re: Faster Than Light Theory

Gravity isn't just there. Gravity is expected to propagate at the speed of light. This invalidates the remainder of your idea. Even if we could determine the gravitational force vector at a single location, we wouldn't be able to use this to detect the positions of atoms. There are too many variable...
by ST47
Fri Jul 31, 2009 4:03 am UTC
Forum: Mathematics
Topic: calculator stupidity
Replies: 3
Views: 932

Re: calculator stupidity

Oh, is it? I always figured it used radians for some part of the calculation, but never got why it couldn't use degrees as well. Now. I always liked wolfram alpha simply because it's able to take a decimal and tell me what that number actually IS, like entering 1.5708 gives you pi/2. It also stumble...
by ST47
Fri Jul 31, 2009 3:46 am UTC
Forum: Mathematics
Topic: calculator stupidity
Replies: 3
Views: 932

calculator stupidity

I don't think I've ever seen a topic on this, and I tried a few searches... Have any of you seen an example where a calculator's simplification system just breaks down? I was doing physics earlier, something about vector addition in cylindrical form, on my TI-89, and got the following as the magnitu...
by ST47
Sat May 23, 2009 5:32 pm UTC
Forum: Mathematics
Topic: New Mathematical Operation: Swagger
Replies: 19
Views: 2806

Re: New Mathematical Operation: Swagger

Swagger's domain is when x is inside reality maybe? Which leads to my next question: Anyone have any idea how swagger would deal with imaginary numbers? How about equations with variables? To answer this question, you need to give this "operation" some sort of meaning or context. It has a...
by ST47
Wed May 06, 2009 6:12 pm UTC
Forum: Mathematics
Topic: AP Calc BC 2009
Replies: 17
Views: 2818

AP Calc BC 2009

So, the exam. It was I think far harder than I expected, and there was a significant amount of material I hadn't seen before. Actual question included for context but spoilered because we're not supposed to talk about it...I'm sure I got some details wrong anyway... One question gave us the taylor s...
by ST47
Sun Apr 12, 2009 12:52 pm UTC
Forum: Mathematics
Topic: The MOST comprehensive math reference poster one can purchas
Replies: 18
Views: 2741

Re: The MOST comprehensive math reference poster one can purchas

EDIT: almost forgot my favorite: http://imgur.com/IQ0S6.jpg What's that supposed to be? It seems to be a picture of science. What significance do the lines and dots have? Why do some fields have more or less lines or dots than others? I would imagine that the colored dots are subfields, identified ...
by ST47
Sat Apr 04, 2009 8:35 pm UTC
Forum: Coding
Topic: xkcd coding contest #2: NOPscotch
Replies: 87
Views: 6135

Re: xkcd coding contest #2: NOPscotch

Well done to entropy!

I'm considering various enhancements, but at this point my code is mostly brute force and very little enhancement. :(.

I have checked and found that every square is reachable via some combination of moves. So 703 is still the upper bound.
by ST47
Sat Apr 04, 2009 4:32 pm UTC
Forum: Coding
Topic: xkcd coding contest #2: NOPscotch
Replies: 87
Views: 6135

Re: xkcd coding contest #2: NOPscotch

Emu: Yep. I can also give you a solution to the sample 8x7 grid, if you'd like to test your algorithm. I don't think a solution has been posted yet.
by ST47
Sat Apr 04, 2009 4:20 pm UTC
Forum: Coding
Topic: xkcd coding contest #2: NOPscotch
Replies: 87
Views: 6135

Re: xkcd coding contest #2: NOPscotch

I have 621 with random jumps, I think, using the path with the md5sum 09d232a2444f47cfe7b1d1b408edf149 I think there's a bug somewhere, but I want lunch. Um. Yeah, there was a bug. I fixed it, but it means that md5sum was incorrect. I'll let it run a while... 631 with 92e2bc1a483e0973c11a73dd0fe77f7...
by ST47
Sun Mar 29, 2009 9:25 pm UTC
Forum: Science
Topic: eclipse=cloak-covered moon--how do I prove/disprove this?
Replies: 10
Views: 1871

Re: eclipse=cloak-covered moon--how do I prove/disprove this?

This is interesting. Let us briefly assume that the hypothesis is in fact plausible. Let us assume that we educated beings have been transported to the dark ages and must now convince the heathen anti-science zealots that we are in fact educated and that they are in fact zealots. How could we dispro...
by ST47
Wed Mar 11, 2009 12:44 am UTC
Forum: Mathematics
Topic: Graph: F(x)=x^∞
Replies: 25
Views: 3350

Re: Graph: F(x)=x^∞

He presumably is retracting his claim and saying instead that it does not converge for x<=-1
by ST47
Tue Mar 10, 2009 10:50 pm UTC
Forum: Science
Topic: Comical mistakes in your homework.
Replies: 144
Views: 17685

Re: Comical mistakes in your homework.

I had someone ask me if impulse and momentum had the same units today. And then argue that they didn't.

I also somehow managed to work out in a calorimetry lab that my cheeto was storing more chemical energy than your average country consumed in its lifetime.
by ST47
Tue Feb 24, 2009 2:10 am UTC
Forum: Mathematics
Topic: Traveling across a square
Replies: 24
Views: 6942

Re: Traveling across a square

You mathematicians always overthink everything. If you're walking strictly horizontally part of the time, and strictly vertically part of the time, sum all the displacement vectors with the same direction, and you get dx=1 and dy=1. 1+1=2.
by ST47
Tue Feb 17, 2009 7:04 pm UTC
Forum: Mathematics
Topic: Math Survey
Replies: 30
Views: 2705

Re: Math Survey

Are we assuming the first fool used all 40,000KM of the rope? I.e. that the Earth's circumference magically became 40,000km Yes, why else would that bit of information be there? I wonder how many sticks the second fool used? The assumption is that the rope was uniformly raised from the ground, but ...

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