Search found 3699 matches

by PM 2Ring
Wed May 06, 2009 3:41 pm UTC
Forum: Science
Topic: Childhood (not so) crackpot theories
Replies: 435
Views: 78728

Re: Childhood (not so) crackpot theories

Did anyone else here believe that there was a quantum string attached to everything, and that it would be very bad for these strings to be tangled? I think I like this theory, or at least a modified version thereof. :) Like one where it's desirable to minimize the tangling as much as possible, and ...
by PM 2Ring
Wed May 06, 2009 2:40 pm UTC
Forum: Science
Topic: Childhood (not so) crackpot theories
Replies: 435
Views: 78728

Re: Childhood (not so) crackpot theories

I used to believe and still do that we are all part of a virtual reality, but really nothing is real. This concept has been investigated extensively in science fiction (not just The Matrix series). For a more serious discussion, you may be interested in Stephen Wolfram's A New Kind of Science and t...
by PM 2Ring
Wed May 06, 2009 1:56 pm UTC
Forum: Science
Topic: Time Travel and Speed
Replies: 24
Views: 2171

Re: Time Travel and Speed

* mumbles something about time dilation being due to velocity differences, not acceleration, per se... *
by PM 2Ring
Wed May 06, 2009 12:33 pm UTC
Forum: Science
Topic: Space Martial Arts
Replies: 45
Views: 3819

Re: Space Martial Arts

Tass wrote:What? Vacuum tubes? In space?

Well, there's no shortage of vacuum to "fill" them with. :)

Some stories from the Golden Age of sci-fi had circuits using vacuum "tubes" that weren't actually sealed. And I recall one short story where a giant CRT was used as a makeshift weapon.
by PM 2Ring
Wed May 06, 2009 11:41 am UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2958
Views: 722472

Re: Common Questions - Now With Extra Relativity!

Long before the discovery of lighter than air gases (and indeed before it was clearly understood that their were different gases, not just "airs" of different quality), it was speculated that a lighter than air craft could be made by evacuating a copper sphere. I'm pretty sure this idea wa...
by PM 2Ring
Wed May 06, 2009 10:54 am UTC
Forum: Mathematics
Topic: Favorite math jokes
Replies: 1452
Views: 489643

Re: Favorite math jokes

Kurushimi wrote:You'd think 2 would give a hand to his prime compatron.

What a back stabber.


The primes are scattered all over the place, with no riem an' reason. Whereas the binary powers form a nice progression. Besides, they are much rarer than primes, so they tend to behave in a more exclusive fashion.
by PM 2Ring
Sun May 03, 2009 4:23 pm UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9990
Views: 2007580

Re: Coding: Fleeting Thoughts

I have finally dug up how to make a function that returns a pointer to an array in C! I've been trying to find an answer to this puzzle for ages, and nobody (you guys, ##c on freenode, etc.) have been able to answer my query. See K&R, 2nd edition, page 122 "5.12 Complicated Declarations&qu...
by PM 2Ring
Fri May 01, 2009 8:32 pm UTC
Forum: Mathematics
Topic: Your favourite calculator
Replies: 43
Views: 5679

Re: Your favourite calculator

I did use some of the very early HP calculators, like the 35, 45 & 25, but I never owned one. I fell in love with RPN almost instantly. :) When I get an urge to do something using RPN, I write programs in PostScript. They're easy to write, but not necessarily easy to read... I find it takes abou...
by PM 2Ring
Fri May 01, 2009 5:14 pm UTC
Forum: Mathematics
Topic: Sierpenski
Replies: 6
Views: 1154

Re: Sierpenski

wow, where did those glider streams come from? Thats why I love Life, always surprising me. I think I've been spending far too much time on Life lately: I've even started dreaming about it. :o anyone have a good algorithm without nested for loops? besides the chaos game of course, it delivers infer...
by PM 2Ring
Fri May 01, 2009 1:23 pm UTC
Forum: Coding
Topic: Coding: Hacks and Snippets
Replies: 434
Views: 784386

Re: Coding: Hacks and Snippets

Another use of the XOR exchange technique is to allow data lines to cross in 2D hardware. I was actually playing around with this earlier this week, doing logic circuits in Conway's Life, using p30 glider streams. Unfortunately, the resultant circuit was far too bulky & I decided to use p60 glid...
by PM 2Ring
Sat Apr 25, 2009 3:38 pm UTC
Forum: Coding
Topic: python program ideas for beginners?
Replies: 10
Views: 9840

Re: python program ideas for beginners?

err, when I attempt to run that program, nothing happens. Isn't def WebHelp(): supposed to be def main(): or something of that sort? Cleverbeans didn't post a complete program, just a function definition. So you have to call it to make things happen. Use of main() is just a convention. Even a Pytho...
by PM 2Ring
Sat Apr 25, 2009 1:16 pm UTC
Forum: Mathematics
Topic: Dimension of magic square vector spaces
Replies: 26
Views: 4976

Re: Dimension of magic square vector spaces

that's great and all, but i'd rather see a program that generates a basis for all odd size magic square vector spaces. Sorry, I don't have the linear algebra skillz for that. FWIW, the first 5x5 magic square I ever found I did by hand, solving the simultaneous equations. Once I'd found one, I notic...
by PM 2Ring
Fri Apr 24, 2009 4:50 pm UTC
Forum: Mathematics
Topic: Simple trig function
Replies: 10
Views: 977

Re: Simple trig function

I am trying to find the length of a chord that intersects a circle such that the area of the sector created is a set fraction of the total circle area. Long story short I've arived at an equation of the form: y=x-sin(x) Is there an explicit solution to this or must it be solved by some other method...
by PM 2Ring
Fri Apr 24, 2009 3:39 pm UTC
Forum: Mathematics
Topic: Looking for a website for sequences
Replies: 6
Views: 850

Re: Looking for a website for sequences

I saw a webpage (a year or so ago) that accepts a list of reals & it tells you a function from the integers that generates the given list. I tested it on the cumulative sum of the Fibonacci reciprocals & it worked ok. Unfortunately, I can't remember the page address, but I might have it book...
by PM 2Ring
Fri Apr 24, 2009 3:19 pm UTC
Forum: Mathematics
Topic: Dimension of magic square vector spaces
Replies: 26
Views: 4976

Re: Dimension of magic square vector spaces

Here's a simple Python program I wrote a year or so ago for generating random magic squares of odd size > 3. Usage: python MagicSquare2.py [size] [seed] Size will be rounded up if less than 5 or even. Randomizer seed can be a number or string. #!/usr/bin/env python ''' Build random magic squares of ...
by PM 2Ring
Fri Apr 24, 2009 1:38 pm UTC
Forum: Coding
Topic: Bash arrays-several (potential) problems
Replies: 9
Views: 605

Re: Bash arrays-several (potential) problems

It's a good man page, and bears repeated reading, IMHO. I almost always refer to it when writing bash scripts. You may also like to have a look at the Bash Guide for Beginners by Machtelt Garrels. Also see Rute User's Tutorial and Exposition , which has a lot of good info about linux in general, alt...
by PM 2Ring
Wed Apr 22, 2009 7:24 am UTC
Forum: Mathematics
Topic: Factorial and Googol
Replies: 9
Views: 2648

Re: Factorial and Googol

Here's some Python code for inverting log factorials I originally posted here a while ago. It's part of a program for calculating e to arbitrary precision. LR2P = .5 * math.log(2.*math.pi) #Log Root 2 Pi L10 = math.log(10.) #Log 10 def invlfact(n): """ Inverse Stirling's approx for lo...
by PM 2Ring
Wed Apr 15, 2009 4:00 pm UTC
Forum: Science
Topic: Is this possible: a bird landing in a moving truck?
Replies: 24
Views: 3378

Re: Is this possible: a bird landing in a moving truck?

No. We are letting these threads die so we can move on to better questions. * decides not to ask what happens if we put a treadmill in the back of the truck * :) I'd heard of Project Pigeon before, but it was interesting to learn that Skinner was behind it. I've seen birds caught in chaotic crosswi...
by PM 2Ring
Wed Apr 15, 2009 2:41 pm UTC
Forum: Science
Topic: Gyroscopic Effect?
Replies: 8
Views: 1716

Re: Gyroscopic Effect?

Hand powered gyroscopes are fun... and rather addictive. I have two: one with lights & one without. I use them almost every day. They may not help you to understand gyroscopic action, but they can't hurt. :)
by PM 2Ring
Wed Apr 15, 2009 2:13 pm UTC
Forum: Science
Topic: Pharmacological Auto-Bioassays
Replies: 2
Views: 1325

Re: Pharmacological Auto-Bioassays

xkcd != erowid
by PM 2Ring
Wed Apr 15, 2009 3:14 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9990
Views: 2007580

Re: Coding: Fleeting Thoughts

A goto breaking out of a loop IS a labeled break, just with a different keyword. On a side note, I find it hilarious that goto is a reserved, unused keyword in Java, meaning you can't even name a VARIABLE 'goto'. Yeah. I actually laughed when I found that out. And don't forget about C's entry reser...
by PM 2Ring
Tue Apr 14, 2009 3:28 pm UTC
Forum: Coding
Topic: Import problem with Python
Replies: 24
Views: 1989

Re: Import problem with Python

The ability to save an interpreter session (including '>>>' prompts), which can't be run as a Python script, to a .py file seems like bad design to me... It's handy if you use doctests. http://docs.python.org/library/doctest.html The doctest module searches for pieces of text that look like interac...
by PM 2Ring
Tue Apr 14, 2009 3:12 pm UTC
Forum: Coding
Topic: Bash arrays-several (potential) problems
Replies: 9
Views: 605

Re: Bash arrays-several (potential) problems

While bash may not be the perfect language for this task, it can certainly do it. I think that it's a good idea to develop some familiarity with bash, and the best way to do that is to use it. It certainly helps if you want to understand scripts on your system, many of which do string manipulation i...
by PM 2Ring
Fri Apr 10, 2009 2:18 pm UTC
Forum: Mathematics
Topic: Magnets and polyhedra
Replies: 15
Views: 6323

Re: Magnets and polyhedra

I also vote for polytope projections. The 600 cell is rather elaborate, but being based on tetrahedra, it shouldn't require extra bracing. The 120 cell is rather pretty, but I don't think it'd work well in this medium, due to all the additional bracing which would be required. From This Week's Finds...
by PM 2Ring
Fri Apr 10, 2009 12:54 pm UTC
Forum: Language/Linguistics
Topic: "off of"
Replies: 80
Views: 13248

Re: "off of"

I asked about this construction a month ago in Little editing/grammar mistakes that drive you up the wall . It seems that it's mostly en-US speakers that are doing this. What's up with the entire "off of" thing? I think you're right. It certainly not standard in British or Australian Engli...
by PM 2Ring
Thu Apr 09, 2009 7:43 pm UTC
Forum: Science
Topic: Theories that are right for the wrong reason
Replies: 32
Views: 4372

Re: Theories that are right for the wrong reason

Most of the laws of optics were discovered when the "propagation through an ether" theory was assumed to be the correct one. Not really. Newton did a lot of work in optics (and there had been some progress in the field before him), and he championed a particle view of light, a view which ...
by PM 2Ring
Thu Apr 09, 2009 7:12 pm UTC
Forum: Science
Topic: Scanning the brain
Replies: 9
Views: 1502

Re: Scanning the brain

Now's where it gets a bit off the rails but IF the peviously mentioned were possible would it be possible to implant/connect such a device to someone else's brain giving them a very crude form of telepathy? (assuming that there was a way to 'display' the incoming brain signals without interference ...
by PM 2Ring
Thu Apr 09, 2009 6:37 pm UTC
Forum: Mathematics
Topic: Complex Analysis
Replies: 8
Views: 1345

Re: Complex Analysis

I just learned today that sin and cos can be equal to a number larger than one. I'm not sure I am comfortable living in this world anymore. How do you all feel about this? It makes me want to plug in my electric guitar, turn the volume up to 11, and make some feedback sounds. :) My point is that th...
by PM 2Ring
Thu Apr 09, 2009 6:12 pm UTC
Forum: Mathematics
Topic: String sets by Kolmogorov complexity
Replies: 13
Views: 1031

Re: String sets by Kolmogorov complexity

Cleverbeans wrote:
Saul wrote:Cantor proved over 100 years ago that the set of transcendental numbers is larger than the set of real numbers. So.. hehe.. that's it.


???

I suspect Saul meant to write "rational" or "algebraic" rather than "real".
by PM 2Ring
Thu Apr 09, 2009 5:17 am UTC
Forum: Mathematics
Topic: Hyperboloid of one sheet: Doubly ruled?
Replies: 10
Views: 7908

Re: Hyperboloid of one sheet: Doubly ruled?

There's a nice ruled hyperboloid on Mathworld that can be rotated. See http://mathworld.wolfram.com/Hyperboloid.html , about half way down the page. Maybe try building one yourself. It's not hard, and IME a hands-on approach really helps one to appreciate how this surface works. Edit: Here's PostScr...
by PM 2Ring
Thu Apr 09, 2009 3:57 am UTC
Forum: Mathematics
Topic: help to solve this
Replies: 15
Views: 1753

Re: help to solve this

I said largest to smallest. PM 2Ring said high to low as well. I think it was a typo when he said “cumulative sum from low to high in an array.” My cumulative sum array would have these values: cum\_sum[index] = \sum_{k=index}^{ENTRY\_COUNT} sorted\_values[index] . If (cum_sum[index] > desired_tota...
by PM 2Ring
Wed Apr 08, 2009 2:47 am UTC
Forum: Science
Topic: [Homework] Given a trajectory find velocity
Replies: 2
Views: 474

Re: [Homework] Given a trajectory find velocity

The velocity is a vector with components \frac{dx}{dt} and \frac{dy}{dt} , the magnitude of this vector is v_0 . You can use this relation to derive an expression for \frac{d\theta}{dt} in terms of x & y, which can then be combined with your expressions for \frac{dx}{d\theta} and \frac{dy}{d\the...
by PM 2Ring
Wed Apr 08, 2009 2:37 am UTC
Forum: Science
Topic: Perpetual Motion Device as a Time Machine
Replies: 10
Views: 968

Re: Perpetual Motion Device as a Time Machine

The connection between time machines & perpetual motion machines is a well-known consequence of Noether's Theorem . The law of conservation of energy is equivalent to saying that the laws of physics are invariant under time translation symmetry. Noether's theorem (also known as Noether's first t...
by PM 2Ring
Tue Apr 07, 2009 1:57 pm UTC
Forum: Coding
Topic: Your perfect language?
Replies: 87
Views: 7886

Re: Your perfect language?

However, when I saw this topic the first time i wanted to reply "English, because that's what they use on Star Trek," which seems relevant. I suspect that when computers are smart enough to be instructed in English (or any other natural language), they won't need humans to write programs ...
by PM 2Ring
Mon Apr 06, 2009 1:51 pm UTC
Forum: Coding
Topic: Java Question-Modifying loop variable inside the loop
Replies: 24
Views: 1644

Re: Java Question-Modifying loop variable inside the loop

Deliberatly avoiding a goto can be just as dangerous :P I tend to agree, although I've rarely found the need to use a goto in over 25 years of writing C. I used tons of them though, when I was writing in unstructured BASIC, or FORTRAN. :) IIRC, the very earliest BASIC dialects I used didn't have a ...
by PM 2Ring
Mon Apr 06, 2009 1:28 pm UTC
Forum: Mathematics
Topic: help to solve this
Replies: 15
Views: 1753

Re: help to solve this

I have a data base of 175 numbers which add up to around $40,000. I need to find the numbers in the data base which add up to $25,571 Is there a method to do this (preferably in excel)? Is this homework? If so, don't expect more than hints here. But if you show us what you've done so far, people wi...
by PM 2Ring
Sun Apr 05, 2009 1:29 pm UTC
Forum: The Help Desk
Topic: [solved] Shell cycle through files oldest to newest
Replies: 3
Views: 450

Re: Shell cycle through files oldest to newest

From man ls

-R, --recursive
list subdirectories recursively
by PM 2Ring
Sun Apr 05, 2009 5:13 am UTC
Forum: Coding
Topic: Java Question-Modifying loop variable inside the loop
Replies: 24
Views: 1644

Re: Java Question-Modifying loop variable inside the loop

What stephentyrone said. Modifying the loop control variable in the loop body is considered by many to be on a par with using goto , and we all know how dangerous that can be. :) It's expected that by reading the loop heading line one can see how the loop starts, terminates & progresses. So if y...
by PM 2Ring
Sat Apr 04, 2009 4:03 pm UTC
Forum: Coding
Topic: Python compiler?
Replies: 29
Views: 2610

Re: Python compiler?

It sounds like I'm going to have to get into emacs. I've never used it, but I did use MicroEmacs on the Amiga for a while, so it's not totally foreign to me. (I still miss Cygnus Ed, and all the ARexx scripts I wrote to enhance it). When doing Python on Windows, I mostly use IDLE. On Linux, I use Ka...
by PM 2Ring
Sat Apr 04, 2009 1:52 pm UTC
Forum: Coding
Topic: Python compiler?
Replies: 29
Views: 2610

Re: Python compiler?

I find the Python interactive mode rather annoying for anything longer than a line or two. So when I want to play around with something that's too small to bother putting in a file I often just use echo to pipe it into python. That way I can rerun multi-line things more easily, but it's still a PITA...

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