## Search found 38 matches

Mon Feb 17, 2014 7:37 am UTC
Topic: 1331: "Frequency"
Replies: 148
Views: 39143

### Re: 1331: "Frequency"

The flashing also wasn't happening when I viewed the image as part of my RSS feed. I was confused until I looked at the rollover text and saw the mention of "gif format".
Mon Dec 10, 2012 11:20 pm UTC
Topic: 1145: "Sky Color"
Replies: 211
Views: 66925

### Re: 1145: "Sky Color"

This is the first time I've seen the mirror writing thing connected to Feynman, but I've seen it described as inspiration for Lewis Carroll. Before I read the full comment thread, here's what I wrote about it: The answer is that the mirror of course doesn't treat left-right any different from up-dow...
Wed Aug 22, 2012 10:06 pm UTC
Forum: Logic Puzzles
Topic: Troll Science: Pi
Replies: 45
Views: 25927

### Re: Troll Science: Pi

The first time I saw this fallacy, it involved a diagonal line rather than a circle. The lesson I took away from it: you can't just assume in general that the limit of a property of a sequence is equal to the property of the limit of the sequence. Really, this should be obvious. Consider the sequenc...
Fri May 18, 2012 5:53 am UTC
Topic: 1057: "Klout"
Replies: 84
Views: 43533

### Re: 1057: "Klout"

It's actually a pretty appropriate request, when you consider the word's other meaning.
Mon Jan 16, 2012 5:07 am UTC
Topic: 1002: "Game AIs"
Replies: 251
Views: 99853

### Re: 1002: "Game AIs"

Computers have a higher probability of winning against humans in a Snakes and Ladders tournament if there are more computers than humans. And since computers are easier to create than humans... This has already been disputed several times, but I'd just like to add: No one has ever created a compute...
Mon Mar 21, 2011 12:04 pm UTC
Forum: Logic Puzzles
Topic: Troll Science: Pi
Replies: 45
Views: 25927

### Re: Troll Science: Pi

I recall seeing the stair-step square-root-of-two version in one of Martin Gardner's anthologies as a child. As far as I'm concerned, the lesson here is that, given an infinite sequence s and a function f that operates on the sorts of things in that sequence, \lim_{i\to\infty}f(s_i) does not...
Wed Dec 15, 2010 1:42 am UTC
Forum: Logic Puzzles
Topic: Programmer problem
Replies: 18
Views: 4276

### Re: Programmer problem

Robozzle is also very much along these lines.
Fri Oct 01, 2010 1:21 am UTC
Forum: Logic Puzzles
Topic: Simple number pattern
Replies: 18
Views: 2777

### Re: Simple number pattern

Well, there's a number in there beginning with a 0. I take that as a pretty clear sign that we should regard this as a series of digit-triplets, rather than as a series of magnitudes.

Also, there are some 1's in there, so it's unlikely to be based on the telephone letter-to-number mapping.
Fri Sep 17, 2010 4:35 am UTC
Topic: 0794: "Inside Joke"
Replies: 131
Views: 33390

### Re: ''Inside Joke'' Discussion (#794)

This makes me think of Dante in particular. Half the people in Hell seem to be either local politicians or characters in novels Dante liked.
Wed Jun 30, 2010 4:23 am UTC
Topic: 0760: "Moria"
Replies: 113
Views: 25261

### Re: "Moria" Discussion

The fools! They went into the depths of Moria without a scroll of Word of Recall?
Tue Oct 20, 2009 6:31 pm UTC
Forum: Mathematics
Replies: 66
Views: 8058

In my mind, it should be analogous to the following game: roll a 4-sided die. If it lands on one, the chance of winning is x. If it lands on two, the chance of winning is x. If it lands on 3, the chance of winning is x. If it land on 4, the chance of winning is x. Does knowing the outcome of the ro...
Mon Oct 19, 2009 9:47 am UTC
Topic: 0651: "Bag Check"
Replies: 206
Views: 52284

### Re: "Bag Check" Discussion

2) Blast and concussion effects from explosives in the open follow an inverse cube law, not an inverse square. Really? Huh. How does that work? Surely the energy is still expanding in a sphere, which means dispersing over an area that increases as the square of the radius. Or is it that it somehow ...
Mon Oct 05, 2009 6:35 pm UTC
Forum: Logic Puzzles
Replies: 217
Views: 65101

### Re: The surprise exam paradox

So the students do their inductive proof. What happens on Monday? The students tell the teacher "We have proved that you will give the exam today! We have eliminated Friday, Thursday, Wednesday, and Tuesday, so it must be today." And the teacher says "No, not today." Then on Tues...
Sun Sep 27, 2009 1:44 am UTC
Forum: Logic Puzzles
Topic: A probability challenge
Replies: 28
Views: 5880

### Re: A probability challenge

Another observation: Questions of this form don't necessarily have answers. This particular question does, but it wouldn't take much to change it so that it doesn't. Suppose your friend's probability function is not uniform. For example, suppose that instead of asking your friend to choose a num...
Mon Sep 21, 2009 10:34 pm UTC
Forum: Logic Puzzles
Topic: A probability challenge
Replies: 28
Views: 5880

### Re: A probability challenge

To put it another way that might be more convincing to your friend: Consider it in terms of your second example, the two people who both guess a number and have a .01% chance of both picking 43. Well, there's also a .01% chance of them both picking 44, isn't there? And also a .01% chance tha...
Sat Sep 05, 2009 5:25 pm UTC
Forum: Logic Puzzles
Topic: Guessing in minesweeper
Replies: 7
Views: 2164

### Re: Guessing in minesweeper

Assuming that this is the Microsoft standard Minesweeper, the setup rule is well-known: there are a fixed number of mines placed at random on a fixed board. "Beginner" level is a 9x9 board with 10 mines, "Intermediate" is 16x16 with 40 mines, and "Expert" is 30x16 with ...
Mon Dec 22, 2008 12:22 pm UTC
Forum: Logic Puzzles
Topic: Man & Chair
Replies: 22
Views: 5793

### Re: Man & Chair

Except, if he forgot his chair, why would he go into the lion cage? I can't believe that a lion tamer would just go "Whoops, forgot my chair today, but I'll be just fine in the cage." rather than, say, "Hey, anybody got a spare chair?" I think the idea is that he forgot ...
Fri Dec 05, 2008 6:56 am UTC
Topic: 0513: "Friends"
Replies: 914
Views: 218839

### Re: "Friends" Discussion

I mean, only one person could have the most beautiful hazel eyes you could ever look into, so she has to know you are talking about her. Well, sure. She'd look at everyone else and say "No one else has the most beautiful hazel eyes you could ever look into, therefore it must be me." And t...
Mon Jul 21, 2008 8:26 pm UTC
Topic: Web Tricky!
Replies: 36
Views: 3817

### Re: Web Tricky!

Actually, now that I look at it again: level 4 is in fact the first page that references wt-std.css. Prior pages use wt_std.css, with an underscord instead of a hyphen. But wt_std.css doesn't exist. I didn't notice the difference at first, because I was looking at the pages under Opera, and ...
Mon Jul 21, 2008 8:08 pm UTC
Topic: Web Tricky!
Replies: 36
Views: 3817

### Re: Web Tricky!

I haven't managed to figure out level 4, but skipped ahead to level 14. The clue leading to 14 is accessible from the very beginning -- maybe this is a mistake, and it's not supposed to be there? As it is, the only reason I hadn't looked there before I got to level 4 is that I didn't get stuck befor...
Fri Jul 18, 2008 5:47 pm UTC
Topic: 0451: "Impostor"
Replies: 381
Views: 108012

### Re: "Impostor" Discussion

And it's not as if the so-called "hard sciences" are without their crackpots, in fact quite the opposite. Anyone whose been to an unvetted APS poster session knows what I'm talking about. And while most practitioners in the field find it comforting that it relatively easy to distinguish a...
Fri Jul 18, 2008 4:58 pm UTC
Topic: 0451: "Impostor"
Replies: 381
Views: 108012

### Re: "Impostor" Discussion

"'In our world,' said Eustace, 'a star is a huge ball of flaming gas.' 'Even in your world, my son, that is not what a star is but only what it is made of,'" the star replies. Yes! That's exactly it! This expresses perfectly the reason why midichlorians never bothered me the way they seem...
Thu Apr 17, 2008 1:19 am UTC
Forum: Science
Topic: The Problems with Teleportation
Replies: 55
Views: 9500

### Re: The Problems with Teleportation

I like the idea of a hypothetical teleporter swapping the thing teleported with whatever is contained in the space it's teleported to, but it wouldn't completely eliminate the 'pop' effect sue to pressure differential (particularly if you teleported into space, or the bottom of the Mariana Trench). ...
Thu Apr 17, 2008 12:56 am UTC
Forum: Logic Puzzles
Topic: AK47 CARD PROBLEM - REALLY IMPORTANT
Replies: 28
Views: 6268

### Re: AK47 CARD PROBLEM - REALLY IMPORTANT

To elaborate on that first point, I'm imagining a conversation something like this: Him: ...So you see, you only have to turn over the A, to see if it has an even number on the other side, and the 7, to see if it has a vowel on the other side! You: What about the K? Shouldn't you flip that over to s...
Thu Apr 17, 2008 12:40 am UTC
Forum: Logic Puzzles
Topic: AK47 CARD PROBLEM - REALLY IMPORTANT
Replies: 28
Views: 6268

### Re: AK47 CARD PROBLEM - REALLY IMPORTANT

If the problem as stated is all that you've been told, then the answer he's probably expecting is wrong. He's probably leaving out the implicit premise that every card has a letter on one side and a number on the other. Don't let him get away with that. Also, saying "the human brain is not equi...
Tue Apr 08, 2008 8:06 pm UTC
Forum: Logic Puzzles
Topic: 3 door problem
Replies: 88
Views: 28787

### Re: 3 door problem

I've introduced some people to this problem myself, and I'm always careful to state the oft-unstated assumption that the host will always open an unchosen empty door after you make your first choice. Making the premise ambiguous only hurts the puzzle. The solution is still unintuitive and argument-e...
Fri Mar 07, 2008 9:36 pm UTC
Forum: Mathematics
Topic: Simple maths problem ......
Replies: 16
Views: 2055

### Re: Simple maths problem ......

Actually, let's take this all the way: If no one was born on Feb 29, then there are 365 possible birthdays, all equally likely. To simplify things, we'll calculate the probability that everyone has different birthdays and subtract 1. Taking them one by one, the chance of the nth person not match...
Fri Mar 07, 2008 8:32 pm UTC
Forum: Mathematics
Topic: Simple maths problem ......
Replies: 16
Views: 2055

### Re: Simple maths problem ......

I think your handling of the leap year is a bit off -- yes, there are 366 possible dates, but February 29 is 1/4 as likely as the others. If you want a completely accurate answer you'll have to handle that case separately. If not, you'll probably get a more accurate answer than you've got by ignorin...
Fri Feb 29, 2008 10:43 pm UTC
Forum: Logic Puzzles
Topic: PuzzleUp 2007 questions
Replies: 22
Views: 5169

### Re: PuzzleUp 2007 questions

Chess Board, reply to Strilanc: Surely not all of the tiles can take optimal paths to their destintions? At some point, you're going to have to swap the corner tiles out of their initial positions, and the corners are not between anything and its destination (taxicab-wise). So the first ...
Tue Feb 19, 2008 9:57 pm UTC
Forum: Logic Puzzles
Topic: The Line Game
Replies: 17
Views: 3964

### Re: The Line Game

OK, here's an operational definition of "know with certainty" that enables the original problem: Immediately after each player's turn, the referee will ask them the question. The player can either answer it or say "I don't know." If any player gives an incorrect answer, YOU FAIL....
Tue Jan 15, 2008 7:08 pm UTC
Forum: Mathematics
Topic: Mathematical Busking
Replies: 50
Views: 4817

### Re: Mathematical Busking

Maybe slip in Carroll's proof that all triangles are isosceles. Just to keep the the audience on their toes.
Wed Dec 19, 2007 9:34 pm UTC
Forum: Mathematics
Topic: Some simple proof
Replies: 11
Views: 1682

### Re: Some simple proof

If someone asked me to prove this for the natural numbers, I'd do something more like: n n = n*n*...*n (with n terms). n! = 1*2*...*n. This also has n terms. If we compare the terms in the two series, we see that every term in the former is larger than the corresponding one in the latter, except for...
Tue Dec 04, 2007 1:46 am UTC
Forum: Mathematics
Replies: 367
Views: 83202

### Re: Division by Zero ([s]3[/s] 4 merged threads)

The thing that people seem to forget when they talk about division by zero is that, quite apart from what mathematicians think, it just plain doesn't make sense in intuitive terms. The common-sense idea of division is taking something and splitting it up into equal pieces. "5/3" means 5 sp...
Sun Nov 18, 2007 9:44 pm UTC
Forum: Logic Puzzles
Topic: Another economics puzzler
Replies: 31
Views: 7456

### Re: Another economics puzzler

The question "Who paid for the knives?" is a misleading one. It's kind of like asking "A man gathers berries growing on public land. No money exchanges hands. Who paid for the berries?", or possibly "A man steals a loaf of bread. Who paid for it?"
Wed Oct 31, 2007 2:12 am UTC
Forum: Logic Puzzles
Topic: The Case of the Missing Dollar
Replies: 44
Views: 16389

### Re: The Case of the Missing Dollar

This problem always reminds me of a trick from elementary school. "You have eleven fingers!" proclaims one child. "I can prove it. Count them." The other child obediently counts to ten on their fingers. "Now count them backward, but stop after one hand." The other child...
Tue Oct 30, 2007 12:57 am UTC
Forum: Mathematics
Topic: Is the geometry of higher dimensions considered euclidean?
Replies: 16
Views: 2444

### Re: Is the geometry of higher dimensions considered euclidean?

For what it's worth, most of Hilbert's axioms for three-dimensional Euclidean geometry hold in R4. The only one that doesn't is the 7th axiom of incidence: If two planes have a point in common, they must have another point in common.
Sat Oct 27, 2007 5:13 am UTC
Forum: General
Replies: 10922
Views: 2299110

### Re: POST HERE FIRST - INTRO THREAD THE THIRD

I don't really want you to know about me. I only joined to post something to the math jokes thread on the math board, and then realized that I'd have to post here to risk violating etiquette. But knowing that I'm unfriendly and secretive is something about me, so now you know something about me.
Sat Oct 27, 2007 5:10 am UTC
Forum: Mathematics
Topic: Favorite math jokes
Replies: 1452
Views: 480667

### Re: Favorite math jokes

My favorite one that hasn't been done here yet: lim(sqrt(3)) = 2 3->4 -- An alternate phrasing of the mathematician in the "prove that all numbers are prime" joke that you might find more satisfactory: 3 is prime, 5 is prime, 7 is prime... well, the pattern is clear, there's obviously a pr...