Search found 2071 matches

by jaap
Fri Aug 31, 2018 8:51 am UTC
Forum: Logic Puzzles
Topic: Train station Puzzle Interview Question
Replies: 3
Views: 1027

Re: Train station Puzzle Interview Question

It's easy once you see it.

Spoiler:
His wife is obviously also home twenty minutes early.
This means she saved 10 minutes drive both ways to/from the station.
So she met him when she had still 10 minutes to go to the station, i.e. at 5:50pm.
He was walking from 5 till 5:50, so 50 minutes.
by jaap
Thu Aug 23, 2018 6:22 am UTC
Forum: Science
Topic: Science fleeting thoughts
Replies: 89
Views: 15172

Re: Science fleeting thoughts

Millisecond-precision timing is very impressive, and this type of thing is also necessary for throwing accurately at long distances. It is something we as humans seem to be almost uniquely good at. Humans are also very good at recognising and following patterns. I reckon that by getting a regular s...
by jaap
Mon Aug 20, 2018 11:25 am UTC
Forum: Mathematics
Topic: Cross-continuousness in higher dimensions,
Replies: 4
Views: 356

Re: Cross-continuousness in higher dimensions,

Interesting thoughts. Just a quick quibble: ... and a stellation of a cube is just an octahedron, ... No, the octahedron is the dual of the cube. The cube, does not have any stellations : There are no stellations of the cube, because non-adjacent faces are parallel and thus cannot be extended to mee...
by jaap
Tue Jul 24, 2018 6:40 am UTC
Forum: Logic Puzzles
Topic: Tower of Hanoi Variant
Replies: 2
Views: 591

Re: Tower of Hanoi Variant

There's a very detailed book "The Tower of Hanoi - Myths and Maths" from 2013 which has a whole chapter devoted to this. The four-peg version is also called Reve's Puzzle, given that name by H.E. Dudeney who was the first to write about this generalization in his 1908 Canterbury Puzzles. T...
by jaap
Thu Jun 21, 2018 3:55 pm UTC
Forum: Mathematics
Topic: Repetitive Coin Flip Probability
Replies: 16
Views: 2246

Re: Repetitive Coin Flip Probability

Seems like that kind of bias would have to be in the method of flipping rather than the coin itself. Quite so. Here's a demonstration of tossing a coin ten times in a row, getting heads each time. (For full disclosure: that is me, and it took me only about 7 or 8 takes. Sorry, I couldn't resist pos...
by jaap
Wed May 30, 2018 9:46 am UTC
Forum: Science
Topic: How much is 1e340 j of energy?
Replies: 19
Views: 1921

Re: How much is 1e340 j of energy?

What I was thinking is that there are some very large numbers that are useful, or at least used, in various types of mathematical explorations, ponderings or theories, perhaps used in things like cryptography (eg: very large primes) or other esoteric fields, even if its just exploring the nature of...
by jaap
Thu Feb 01, 2018 6:48 am UTC
Forum: Logic Puzzles
Topic: Rubrics Cube of Doom
Replies: 3
Views: 2350

Re: Rubrics Cube of Doom

I plan on painting over the squares of a rubrics cube It's called a Rubik's Cube, named after its inventor Ernö Rubik. Such maze cubes have been designed before. The standard maze cube design was made by Christoph Lohe, and he explains the reasoning behind it here: The Maze Cube You can buy sticker...
by jaap
Tue Jan 02, 2018 7:32 am UTC
Forum: Language/Linguistics
Topic: Is this logical statement true or false?
Replies: 9
Views: 3318

Re: Is this logical statement true or false?

[...] or that it does have meaning, and it is simply false, since there are no colorless green ideas, and therefore there can't be any sleeping, furiously or otherwise. In mathematical logic such a statement would be considered true. Non-existent objects have any property you can name because to pr...
by jaap
Fri Nov 24, 2017 9:55 am UTC
Forum: Fictional Science
Topic: How do you define..."you"?: Question about Infinite Universe
Replies: 22
Views: 3711

Re: How do you define..."you"?: Question about Infinite Universe

andykhang wrote:The alternate self idea? That's there is infinite version of you when you have infinite universe?

Are you talking about a multiverse (i.e. parallel universes) rather than a single infinitely large universe?
by jaap
Tue Nov 21, 2017 7:11 pm UTC
Forum: Mathematics
Topic: periodicity in LCGs
Replies: 2
Views: 2097

Re: periodicity in LCGs

You have X_{t+1} = (aX_t + c) mod 2^k You can simply look at it mod 2^1: X_{t+1} = (aX_t + c) mod 2 The resulting lowest bit of X_{t+1} does not depend on any of the higher bits of X_t, only on the lowest bit. Therefore, this reduced PRNG essentially has an internal state consists only of a single b...
by jaap
Fri Nov 17, 2017 11:12 am UTC
Forum: Mathematics
Topic: Maximizing 2 Variables
Replies: 19
Views: 3808

Re: Maximizing 2 Variables

Eebster the Great wrote:Again, you are maximizing the objective function, not "two variables". You can certainly maximize a function of multiple variables (if it has a maximum).

I'm not disagreeing, just explaining why you need such a function and giving a simple example.
by jaap
Fri Nov 17, 2017 9:50 am UTC
Forum: Mathematics
Topic: Assassin Problem over the Internet
Replies: 40
Views: 6866

Re: Assassin Problem over the Internet

Hmm, watching the videos, I don't like the solutions presented. The originating person's proposal is, with the extraneous stuff removed: 1. Number all the people 1-8. 2. Get cards numbered 1-8, in order. Cycle the deck (move top card to bottom) a random number of times. 3. Give the first ca...
by jaap
Fri Nov 17, 2017 9:16 am UTC
Forum: Mathematics
Topic: Maximizing 2 Variables
Replies: 19
Views: 3808

Re: Maximizing 2 Variables

Yeah, with x(t) and y(t) plotted on an x-y plane, maximizing x and y at the same time means having a cusp that "points" toward the top-right. cusp.png Such a cusp is not a general feature of parametric plots, and it's irrelevant (to the general case) that if your graph is just a line segm...
by jaap
Thu Sep 07, 2017 1:13 pm UTC
Forum: News & Articles
Topic: Bedfordshire Professor Claims Voynich Breakthrough
Replies: 9
Views: 8955

Re: Bedfordshire Professor Claims Voynich Breakthrough

**BUMP**

Another reasonably convincing interpretation:
https://www.the-tls.co.uk/articles/publ ... -solution/
by jaap
Wed Sep 06, 2017 5:55 am UTC
Forum: Logic Puzzles
Topic: 538 hats riddle
Replies: 20
Views: 4573

Re: 538 hats riddle

With 7 people you can use two rules. Rule one - If you see four people with the same color, then you must guess that you have the opposite color. Win - 70/128 Lose - 42/128 Rule two - If you see six people with the same color, then you must guess that you have the opposite color Win - 14/128 Lose -...
by jaap
Mon Sep 04, 2017 3:14 pm UTC
Forum: Logic Puzzles
Topic: 538 hats riddle
Replies: 20
Views: 4573

Re: 538 hats riddle

It is not stated clearly in the question, but I assume that each hat's colour is chosen independently, 50:50 either colour. What you say is true if you make a fixed choice beforehand about who is going make a guess. However, you don't have to do that. For example, consider the smaller version of the...
by jaap
Sat Sep 02, 2017 1:59 pm UTC
Forum: Language/Linguistics
Topic: Miscellaneous language questions
Replies: 570
Views: 82373

Re: Miscellaneous language questions

Maybe at some point the y spelling had dots added because as I wrote before the letter y is not used much normally. In cursive handwriting the ij is essentially identical to y apart from the dots, and it is very hard to resist the urge to automatically add them. That is really interesting. Is this ...
by jaap
Sat Sep 02, 2017 11:53 am UTC
Forum: Language/Linguistics
Topic: Miscellaneous language questions
Replies: 570
Views: 82373

Re: Miscellaneous language questions

Non-English 26ers include Dutch (Ij directly replacing Y, it seems, a detail to which I would clearly defer to any Dutch forumite who cared to comment) I'm Dutch, so let me wade in here about the Dutch "IJ". It represents a vowel sound, one of the many diphthongs spoken Dutch has. It is n...
by jaap
Fri Sep 01, 2017 2:27 pm UTC
Forum: Mathematics
Topic: Possible "Spot it!"-like decks
Replies: 30
Views: 7037

Re: Possible "Spot it!"-like decks

See I thought that when you made cards like these it was what he was asking about. I thought these worked, Meets all his conditions. 1376524 1745632 1234567 1472635 1563472 1625743 All your cards have the same symbols. We don't care about their order on each card, so every pair of cards in your set...
by jaap
Thu Aug 31, 2017 9:40 am UTC
Forum: Language/Linguistics
Topic: Miscellaneous language questions
Replies: 570
Views: 82373

Re: Miscellaneous language questions

Non-English 26ers include Dutch (Ij directly replacing Y, it seems, a detail to which I would clearly defer to any Dutch forumite who cared to comment) I'm Dutch, so let me wade in here about the Dutch "IJ". It represents a vowel sound, one of the many diphthongs spoken Dutch has. It is n...
by jaap
Wed Jul 26, 2017 12:06 pm UTC
Forum: Mathematics
Topic: Determining line of sight over time
Replies: 30
Views: 5744

Re: Determining line of sight over time

By the way, having the observers moving instead of stationary does not change the difficulty of this question. Are you dropping the implicit assumption that the objects in the space are stationary? I guess so, because I never really thought of the objects as stationary. *since the line end points r...
by jaap
Wed Jul 26, 2017 5:21 am UTC
Forum: Mathematics
Topic: Determining line of sight over time
Replies: 30
Views: 5744

Re: Determining line of sight over time

Sure. I'm trying to understand the point? Do you think her/his problem is solvable? The OP is not clear: If both points are stationary is it trivial to determine whether or not they can see each other. However, both points are moving. As you said, and I agree, that part is still essentially trivial...
by jaap
Tue Jul 25, 2017 2:40 pm UTC
Forum: Mathematics
Topic: Determining line of sight over time
Replies: 30
Views: 5744

Re: Determining line of sight over time

There are two points in a space. The space is filled with objects. If both points are stationary is it trivial to determine whether or not they can see each other. However, both points are moving. Luckily, they are moving in straight lines with a constant speed. How would I go about determining at ...
by jaap
Mon Jul 24, 2017 11:57 am UTC
Forum: Logic Puzzles
Topic: Arithmetic puzzle
Replies: 5
Views: 4347

Re: Arithmetic puzzle

It is not possible.

For n>1 we have:
log n! < log nn = n log n < n2

So n! always has fewer than n2 digits (except for 1! and 0!).
by jaap
Fri Jul 21, 2017 12:28 pm UTC
Forum: Logic Puzzles
Topic: Isosceles triangles and circles : puzzle connection
Replies: 15
Views: 3743

Re: Isosceles triangles and circles : puzzle connection

Read what was written in the picture : "At right you have samples of isosceles triangles connecting three circles" Is there any precision about right triangle or not? no. So triangles could be right or not. Just watch carefully my examples : you have right triangles and not right triangle...
by jaap
Sun Jul 16, 2017 5:27 pm UTC
Forum: Movies and TV Shows
Topic: Doctor Whom
Replies: 4917
Views: 658921

Re: Doctor Whom

charliepanayi wrote:We have a female Doctor

Jodie Whittaker
by jaap
Fri Jul 07, 2017 7:52 am UTC
Forum: Language/Linguistics
Topic: How to write in plain language
Replies: 32
Views: 6062

Re: How to write in plain language

Are you getting that 20 words/sentence average from your personal digital copy? I admit that is an awful lot. On the other hand, by Shane Snow's calculations , Hemingway's books have an overall Flesch-Kincaid reading level of 4, and reading ease of a startling 95. So clearly it matters which metric...
by jaap
Sun Jul 02, 2017 1:24 pm UTC
Forum: Language/Linguistics
Topic: Regional Dialect and Idiolect Oddities (pronunciation)
Replies: 941
Views: 234874

Re: Regional Dialect and Idiolect Oddities (pronunciation)

Question: Here in the US decimal numbers are written with a "decimal point " as e.g. 3.14, which is said out loud as "three point one four". I know that in some (many?) other countries decimals are written using a comma as 3,14. In this case how is the number said out loud? Is i...
by jaap
Sat May 27, 2017 5:29 am UTC
Forum: Language/Linguistics
Topic: “good big”
Replies: 7
Views: 3596

Re: “good big”

See also this language log post. It mentions some examples where the most common word order defies categorization, e.g. "ugly little"/"big ugly".
by jaap
Tue May 02, 2017 2:57 pm UTC
Forum: Mathematics
Topic: Halting Problem
Replies: 208
Views: 30931

Re: Halting Problem

This what I don't understand - my assumption (perhaps mistaken) is that the Oracle program must have the last move (i.e., it must say that whatever's been fed to it will halt or that what's been fed to it will loop forever). Is that assumption incorrect? That is correct. If you had a perfect Oracle...
by jaap
Thu Apr 27, 2017 7:22 am UTC
Forum: Coding
Topic: Coding: Fleeting Thoughts
Replies: 9862
Views: 1765796

Re: Coding: Fleeting Thoughts

Microsoft Powerpoint is Turing complete:
https://www.youtube.com/watch?v=uNjxe8ShM-8
by jaap
Wed Apr 12, 2017 12:24 pm UTC
Forum: Logic Puzzles
Topic: Two secrets
Replies: 20
Views: 7701

Re: Two secrets

I think I have an O(log(N)) solution. Let A initially be {1, 2, 3, ..., N-1}. At all times, we know that at least one of the numbers is in A. Divide A into three roughly equal sets A 1 , A 2 , and A 3 , and ask about A 1 ∪ A 2 , A 1 ∪ A 3 , and A 2 ∪ A 3 . If we get a "yes" response to on...
by jaap
Mon Apr 10, 2017 2:11 pm UTC
Forum: Science
Topic: Does the geographical distribution of the northern and southern hemispheres affect the rotation of the Earth?
Replies: 8
Views: 2544

Re: Does the geographical distribution of the northern and southern hemispheres affect the rotation of the Earth?

Is the biggest effect to do with moving closer/further from the poles, thereby moving mass closer/further from the axis, and changing the moment of inertia?
by jaap
Thu Mar 30, 2017 9:23 am UTC
Forum: Mathematics
Topic: Futurama Puzzle Game
Replies: 5
Views: 2808

Re: Futurama Puzzle Game

That is an interesting question. Of course, in the episode the problem was fixed by adding two people who hadn't swapped yet, which adds enough available swaps to always make it solvable. It looks like there's some parity rule that forces complete paths to have an even number of steps, but I'm not s...
by jaap
Mon Mar 06, 2017 12:42 pm UTC
Forum: Science
Topic: How can we experminetly determine the acceleration due to gravity?
Replies: 20
Views: 4640

Re: How can we experminetly determine the acceleration due to gravity?

But for an object rolling without slipping, some of the gravitational potential energy is transformed into rotational energy. If I do the calculations right, the proportion depends on the ratio of the moment of inertia of the object and the product of its mass and the square of its rolling radius, ...
by jaap
Thu Mar 02, 2017 9:35 am UTC
Forum: Logic Puzzles
Topic: Escape the Frictionless Circle
Replies: 156
Views: 48077

Re: Escape the Frictionless Circle

LaserGuy wrote:If you fall outward,

That's a big if. How do you fall outward if your feet slide inward?
by jaap
Thu Feb 02, 2017 3:26 pm UTC
Forum: Science
Topic: Coincidence in Tycho's Model of the Solar System
Replies: 6
Views: 2679

Re: Coincidence in Tycho's Model of the Solar System

The model in that video is not to scale. The gaps between the orbits of neighbouring planets in that video are all the same, whereas in actuality the distances increase further out. Because the video uses equal distances, you will get such apparent coincidences as it makes sixth planet exactly twice...
by jaap
Wed Feb 01, 2017 4:22 pm UTC
Forum: Science
Topic: Newton's shell theorem with negative mass
Replies: 12
Views: 3218

Re: Newton's shell theorem with negative mass

I actually did my doctoral dissertation on negative mass, but mostly on cosmological scales. A matched pair of positive and negative mass particles would indeed accelerate forever. This doesn't violate conservation of energy, since the negative mass has negative kinetic energy. Generalizing, a gas ...
by jaap
Mon Jan 30, 2017 1:23 pm UTC
Forum: Science
Topic: Explosions and Unobtainium, as pertains to video game physics
Replies: 9
Views: 2911

Re: Explosions and Unobtainium, as pertains to video game physics

Here's another data point. The Mythbusters tested a scene from Lethal Weapon 2: https://en.wikipedia.org/wiki/MythBusters_(2011_season)#Episode_178_.E2.80.93_.22Toilet_Bomb.22 It turns out that that a rather heavy metal bathtub can protect you from a blast that would otherwise have been lethal (180 ...
by jaap
Wed Jan 11, 2017 4:44 pm UTC
Forum: Movies and TV Shows
Topic: Star Wars Episode VIII naming contest
Replies: 35
Views: 7386

Re: Star Wars Episode VIII naming contest

Just for larfs... What is your guess about what Episode VIII will be called? I'll lay down The Ways Of The Force I think they'll want to give a three-act structure to the new trilogy, so the middle film needs to be a slightly darker one where the Empire New Order strikes back. The title will probab...

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