wu :: forums - Print Page


    
      
        wu :: forums
        (http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi)
      

        riddles >> what happened >> 3 NEARLY IMPOSSIBLE RIDDLES
        
(Message started by: srn347 on Aug 29^th, 2007, 11:08am)

Title: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Aug 29^th, 2007, 11:08am

A person flips a coin with you and he says"heads I win tails you lose". You agree to it. How do you win?

Yugi and Atem are playing yugioh against many people in a row. Yugi has a 50% chance of winning and Atem has a 50% chance losing. For those of you who don't know, they switch which soul/mind is used and they share a body. Why/when would they switch.

When you say no, do you mean yes?

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by mikedagr8 on Aug 29^th, 2007, 5:08pm

1. Give him a double sided tails coin to flip or you flip that coin.

2. Pardon, it shouldn't matter when or if ever, they have the same relative chance it seems.

3. When I say no, I mean no.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Aug 29^th, 2007, 5:11pm

One of those answers is correct.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by mikedagr8 on Aug 29^th, 2007, 5:12pm

When you say one of those answers are correct, do you mean that I think that these are lame?

This should be in the easy section, if I can fluke it. Seriously.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Aug 29^th, 2007, 5:16pm

All you got was the third one. If you can fluke them, do it!

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by mikedagr8 on Aug 29^th, 2007, 5:17pm

No I mean that if I can look at them for 10 seconds and still be correct, they're not hard.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Aug 29^th, 2007, 5:19pm

The last one may have been kind of easy(I wanted to trick you into saying no, which would have meant yes), but you still can't solve the other ones.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by mikedagr8 on Aug 29^th, 2007, 5:23pm

Given time and logical understanding anything I do can be solved. Just now, I don't have the time. I'm trying to finish reading through all the updates so I can start doing my logs assignment.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Aug 29^th, 2007, 5:27pm

Then why call it easy without time to prove it?

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by towr on Aug 30^th, 2007, 12:51am

on 08/29/07 at 11:08:47, srn347 wrote:

A person flips a coin with you and he says "heads I win tails you lose". You agree to it. How do you win?

Cheat
e.g. Make it come up on its side. (Some soft underground like clay might help with that, although some coins can be balanced well enough on the side).
Coins without a head or tail would work as well.

Quote:

Yugi and Atem are playing yugioh against many people in a row. Yugi has a 50% chance of winning and Atem has a 50% chance losing. For those of you who don't know, they switch which soul/mind is used and they share a body. Why/when would they switch.

Yugi has at least as high a chance of winning as Atem, so he should always play.
And isn't the game properly called "duel monsters" or something?
(Of course prolonged playing might tire Yugi, dropping his successrate; so once it drops below Atem's, he should take over.)

Yugi and Atem always win when it counts though.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by Grimbal on Aug 30^th, 2007, 2:08am

- A person flips a coin with you and he says"heads I win tails you lose". You agree to it. How do you win?
~~- By chance.~~
Oops, I see the trick now. Shame on me.
Maybe:
- By saying: "I bet you'll win!"
- By saying: "More specifically: heads we both win tails we both lose."
- You examine the coin, say: "OK, you won", and pocket it.

- Yugi and Atem are playing yugioh against many people in a row. Yugi has a 50% chance of winning and Atem has a 50% chance losing. For those of you who don't know, they switch which soul/mind is used and they share a body. Why/when would they switch.
- They both win with 50% chance, so it doesn't matter who plays. A switch could be considered cheating by other players, so don't.

- When you say no, do you mean yes?
- Noooo! Absolutely not! How can you think such a thing of me? ::)

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by rmsgrey on Aug 30^th, 2007, 2:34am

1) "A strange game. The only winning move is not to play. How about a nice game of chess?"

2) Is it possible to draw in Yugioh?

3) No.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 3^rd, 2007, 9:03pm

on 08/30/07 at 02:08:29, Grimbal wrote:

Good answers, but no, grimbal. Rmsgrey, you must play, and you usually can draw in yugioh, but in this riddle no. Here's a hint, if you play n games, you win n-1 or n with 50-50 probability. And grimbal, it isn't considered cheating.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by hiyathere on Sep 4^th, 2007, 11:35am

on 08/29/07 at 11:08:47, srn347 wrote:

A person flips a coin with you and he says"heads I win tails you lose". You agree to it. How do you win?

Well, technically you could manipulate how you say it. For example, if it is heads, you can say "You said heads I win!" , the "I" meaning yourself, and the "You" meaning the other person. If it is tails, then you do the opposite of that. That way, you win either way.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 4^th, 2007, 5:21pm

So close.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by mikedagr8 on Sep 5^th, 2007, 4:36am

You repeat the statement of "heads I win, tails you lose". This way you win every time, if they argue you just repeat the statement proclaiming that they agreed to it, proving that you always win.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by Roy on Sep 5^th, 2007, 4:39am

1. You punch the guy and run off with his wallet, or you lose the coin down a drain or something before you get the chance to flip it.

2. Why is because they are fighting in the shadow realm and yugi can't hold his own very long, or like the series, they end up playing Pegasus and use the switch strategy so he can't read their mind/s

3. In response to that question or another?

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by hiyathere on Sep 5^th, 2007, 4:54pm

I put the words in the wrong order in my last post. I edited it. see if it works now

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 5^th, 2007, 6:13pm

On the first one, if it's heads you say"If it was tails I would have lost, but it wasn't so I don't" and vice-verca. For the yugioh thing, after the first game if you won, switch. Since that was 50%, the other 50%(you losing)won't happen, so you switch every match starting after your first win(which occurs after 1 or 2 matches). The third answer is anything that implies no without saying it(like nope, or negative).

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by FiBsTeR on Sep 5^th, 2007, 7:00pm

on 09/05/07 at 18:13:42, srn347 wrote:

??? There seems so many things wrong here I don't know where to begin.

"If it was tails I would have lost, but it wasn't so I don't"

Let: p = tails comes up, q = I lose, ~p = not p, ~q = not q

You're saying that: (p --> q) --> (~p --> ~q), or that the statement implies the inverse. That doesn't work.

"Since that was 50%, the other 50%(you losing)won't happen"

This argument came up before (http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_hard;action=display;num=1184422609;start=4#4) (edit: found it!), about how a "1-in-2" chance means that if it doesn't happen the first time, it must happen the next time. This isn't how probability is defined, assuming these games are independent of each other.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 5^th, 2007, 10:57pm

I was assuming they were dependant. And what is with that arrow thing? I've seen it before, but what does it represent.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by towr on Sep 6^th, 2007, 12:33am

It doesn't help to switch, even if the chances are strictly dependent, you'd still overall lose half the games. Because if Yugi switches after having won, then if Atem wins the second round, whoever plays the third round will lose again. And it would continue win-lose-win-lose etc

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by hiyathere on Sep 6^th, 2007, 10:53am

on 08/29/07 at 11:08:47, srn347 wrote:

A person flips a coin with you and he says"heads I win tails you lose". You agree to it. How do you win?

I misread the question...

I thought it was "Heads I win tails I lose".

i guess I'm too used to that...

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 8^th, 2007, 7:43pm

on 09/06/07 at 00:33:09, towr wrote:

No, because it was 50% I win and I won so the next 50% won't happen and that is me losing if I switch(which I do).

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by towr on Sep 9^th, 2007, 7:26am

on 09/08/07 at 19:43:59, srn347 wrote:

No, because it was 50% I win and I won so the next 50% won't happen and that is me losing if I switch(which I do).

That makes absolutely no sense.

Besides, if if that nonsensical bit of reason held true, Atem could still loose after switching, then of course you wouldn't switch so he'd win the next round, but then you'd have to switch again. And then why wouldn't Yugi lose?
Or are you proposing both Yugi and Atem always win the first round in a series?

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 9^th, 2007, 10:13am

I already explained it. If every two games are dependant on each other, the 50% thing happening means the other 50% thing won't.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by towr on Sep 9^th, 2007, 10:43am

And I explained why that doesn't make any sense.
It's not how probability works. If by some strategy someone always wins, then there isn't a 50% chance they lose.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 9^th, 2007, 11:44am

If they were independant of each other. But I said they were dependant on each other.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by towr on Sep 9^th, 2007, 12:20pm

How do you figure that applies here? If he never loses he has no probability of losing. Period.
It doesn't depend on how well he played the last time, so statistical dependence doesn't play a role.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 9^th, 2007, 6:28pm

He does have a probability of losing, but I manipulate that probability. I could apply the inverse to make him always lose.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by towr on Sep 10^th, 2007, 12:05am

on 09/09/07 at 18:28:42, srn347 wrote:

He does have a probability of losing, but I manipulate that probability. I could apply the inverse to make him always lose.

If you're so sure, use Bayes to prove it.
That should keep you busy till the end of eternity, because your conception of probability is patently nonsensical..

Ever heard of the law of large numbers? What a probability X means, is that in the long run, it will happen a fraction X of the time, no matter what strategy you employ.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by Roy on Sep 10^th, 2007, 5:06pm

srn347, just how do you know that yugi/Atem will win their first match to begin with? They have as much chance of winning as they do of losing at any time, just because they would win one, doesn't mean that if they switch they would win again, does it? The correct answer is that you don't know when to switch, the writers do ;D :P

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 11^th, 2007, 4:53pm

Who is Bayes? And you can't prove that I am not a writer.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by towr on Sep 12^th, 2007, 12:02am

on 09/11/07 at 16:53:19, srn347 wrote:

Who is Bayes?

Google it.
If you knew half of anything about probability you should already know him though.

Quote:

And you can't prove that I am not a writer.

You're not on the ending credits like every other writer.. Nevermind that they don't have 13 year olds on their writing staff.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES+one more riddle
Post by srn347 on Sep 13^th, 2007, 9:46pm

How about another riddle instead of long tedious debate over probability manipulation? Two people battle. One has every weapon in existance(and some only on tv), and the other one has nothing. Why does the other one win? Hint:even though the other one wins, he might have been destroyed along with the other person(or maybe not)...

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES+one more riddle
Post by mikedagr8 on Sep 14^th, 2007, 4:22am

on 09/13/07 at 21:46:00, srn347 wrote:

The other for some strange reason ponders the same thing as he has the ability to see the future, giving time for the other person to push them over the edge of the elevated platform they were fighting on.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 14^th, 2007, 7:20pm

No, but good try. Hint:the second person doesn't need to do anything to win.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by thecow135 on Sep 17^th, 2007, 8:52pm

obviously the first person has the so many weapons that he gets crushed beneath them... just like obviously the riddle is greatly worded

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 17^th, 2007, 8:57pm

Creative, but no.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by towr on Sep 18^th, 2007, 1:18am

My guess would be a nuclear weapon, or something similar.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by srn347 on Sep 19^th, 2007, 6:38am

Something similar. A bomb that the first guy has explodes, but the second person might be hit by the explosion.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by iono on Oct 25^th, 2007, 6:18pm

if you flip a coin, it has a 50% chance of coming up heads. If it does, that doesn't mean the next flip is guaranteed to come up tails. heads has a 50% chance of coming up the first time, and 50% the 2^ndtime, regardless what happened the first time. Same thing with the second qustion. ;)

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by shasta on Jan 19^th, 2008, 9:03am

[quote author=FiBsTeR]
"If it was tails I would have lost, but it wasn't so I don't"

Let: p = tails comes up, q = I lose, ~p = not p, ~q = not q

You're saying that: (p --> q) --> (~p --> ~q), or that the statement implies the inverse. That doesn't work.
[/quote]

[quote author=srn347]I was assuming they were dependant. And what is with that arrow thing? I've seen it before, but what does it represent.[/quote]

Ah, good ol' symbolic logic. The arrows are best translated as meaning "implies", though I think it would translate a little better into standard English if he had used a "therefore" symbol instead of the middle arrow. The best way to do it using the standard qwerty keyboard that I know of would look like this...

P ---> Q
Q ---> R
-----------
P ---> R

The horizontal line in the middle translates into "therefore". Thus this argument would be read aloud as "P implies Q and Q implies R. Therefore, P implies R." In logic, when one thing implies another it means that if it's true, than this other thing is true too. So another way to say the above statement is... "If P is true, then Q is true. If Q is true, then R is true. Therefore, if P is true, then R is true."

Note that "therefore" and "implies" are logical synonyms, but in English it's easier I think for most to understand it like this. Otherwise the statements get a little cluttered "If it's true that if P is true then Q is true and that if Q is true then R is true, then it's also true that if P is true then R is true.". It means the same thing, but it's just a more complicated way of saying it.

So getting back to the argument you presented...
P="The coin comes up heads."
Q="John, the coinflipper wins."

You're suggestion to win if the coin comes up tails symbolically looks like this, (remember that ~ means "not"),...

P ---> Q
~P
---------
~Q

...which can be read in English as "P being true implies that Q is also true. P isn't true. Therefore Q isn't true." This is a common fallacy of logic known as "denying the antecedent". The fact that one thing implies another does not mean that the opposite of that thing implies the opposite of the other. For example...

If my name is John, my name starts with J.
My name is not John.
Therefore my name does not start with a J.

This of course is wrong because my name could be Jim, Jeff, Jeremiah, and many others. Any argument that is set up in this same way is a fallacious argument, even if it's conclusion happens to be true! For examples...

If every day alien battleships fire hair tonic at my head, then my hair goes down to my knees.
It is not true that every day, alien battleships fire hair tonic at my head.
Therefore my hair must not go down to my knees.

It is true that my hair doesn't go down to my knees, but this argument is still false, (the conclusion is true for entirely different reasons).

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by tiber13 on Jan 20^th, 2008, 7:32am

2) when yugi is about to lose, switch to atem.
solves yugi's problem
3) Yes, which would mean no

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by towr on Jan 20^th, 2008, 7:35am

on 01/19/08 at 09:03:27, shasta wrote:

It is true that my hair doesn't go down to my knees, but this argument is still false, (the conclusion is true for entirely different reasons).

A slight comment on terminology, it's probably better to say that the argument is invalid, rather than false. (Or you could even say the inference rule used in the argument is invalid, and therefore the argument fails.)

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by shasta on Jan 21^st, 2008, 5:54pm

on 01/20/08 at 07:35:45, towr wrote:

Good catch. Thank you. :)

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by onlyme722 on Mar 5^th, 2008, 4:24am

FiFirstly...in reference to #1...UNLESS some unexpected, unpredictable, and factor unaccounted for comes in to play, I can't win. Bottom line is: mathematically and logically...according to the argument which you hath presented, I lose either way. You could choose to factor in ridiculous odds that include something BESIDES a regular coin with a heads & tails...otherwise your definition would contradict any other answer.

#2) To simplify it (more than you have done so yourself without realizing) if there are two people who oppose each other, and one of them has a 50% chance of losing, it would also imply that that same individual, as opposed to losing, has a 50% chance of winning. Unless you factor in some inanely ridiculous outside element to contradict this, such as..."one of them possesses a magic bean"....well, this is simply an inane riddle all around....Especially considering that, unless inside knowledge of "yugiho" (or whatever) comes into play, you can't simply ask this of any normal person who watches cartoons on adult swim ;) (yes, that's intended to come off as sarcastic and slightly insulting...my apologies).

And #3...anyone who studies and enjoys the English language (in this case) knows that there are paradoxes everywhere. Figure of speech, sarcasm, satire, exaggeration, allegory, irony, metaphor.....etc...all come in to play.

This(#3), however, is not a very convincing paradox.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by onlyme722 on Mar 5^th, 2008, 4:37am

also...i apologize for coming off as a total *itch,,,and isn't it funny that if you were you forget to hit the shift key (which I happened to have done) the word is still almost completely intact?

I will look over this again tomorrow, when I am in possession of a more sane mind :D.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by Icarus on Mar 5^th, 2008, 7:05pm

A sane mind isn't useful when dealing the ramblings of srn347.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by Roy on Mar 5^th, 2008, 7:10pm

truer words couldn't have been spoken.

Now then, i was away from these boards for a while, when was srn347 banned and under what violation (so i can smile to myself)?

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by SMQ on Mar 6^th, 2008, 5:13am

on 03/05/08 at 19:10:40, Roy wrote:

Now then, i was away from these boards for a while, when was srn347 banned and under what violation (so i can smile to myself)?

He was banned sometime in the early morning of 4 October (UTC) (http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_suggestions;action=display;num=1189630753;start=75#75), presumably for being his usual charming self, although no direct reason was given (and William doesn't need to give one--it's his board after all).

--SMQ

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by Ghost Sniper on Mar 6^th, 2008, 4:05pm

Now that srn347 is gone, could someone work on banning temporary?

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by SMQ on Mar 6^th, 2008, 4:37pm

Nah, temp may be pretty clueless, but he's no where near srm347's disruptiveness -- not even in the top five annoying characters I've seen around here. Banning should be an action of last resort, and I, at least, haven't had any problem simply ignoring temporary. Problem solved. ;)

--SMQ

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by temporary on Mar 11^th, 2008, 10:35pm

William owns the board? Now I know who banned srn347 and that he(or she) might have had no reason for doing it. But just because he is gone, doesn't mean his threads should be ignored. Don't let the flame die out! Since all the questions in this one have been solved, I might as well carry on for him. Next question:
what would happen if a person moved their shadow faster than light while the person is slower than light(this is possible depending on the light source and the distance)? Would the shadow predict the person's movement?

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by SMQ on Mar 12^th, 2008, 6:08am

on 03/11/08 at 22:35:01, temporary wrote:

William owns the board?

Well, technically the Open Computing Facility (http://www.ocf.berkeley.edu) of the University of California, Berkeley (http://www.berkeley.edu) owns the board, but Willian Wu (http://www.ocf.berkeley.edu/~wwu) is its founder and sole administrator.

Quote:

Now I know who banned srn347 and that he(or she) night have had no reason for doing it.

While William never commented directly on the ban, I think it's safe to assume he did it because one (or more) of the moderators asked him to and he agreed.

The moderators of this board (and until last year that was only towr and Icarus, so they deserve most of the credit) it seems have always tried to gently nudge the discussions around here toward a certain "character": one of openness to discussion and a willingness to learn. Very few regulars on this board seem to have much of an "ego" regarding their answers/opinions/ideas, and I think it's exactly that "character" that attracts the high caliber of regulars this board has. There are some very knowledgeable and intelligent folks hanging around here, and they're (almost) always willing to help out anyone who asks.

For over a month, srn347 did his best to completely obliterate that "character". He was belligerent and rude, insisting on the rightness of his position in the face of any argument to the contrary, and treating everyone who disagreed with him as beneath his contempt. Not only did he not have a willingness to learn, he actively resisted it; in his 700+ posts, not once did he admit to even the slightest error in judgment or understanding. He was the anti-wu :: forums, and the sheer volume of his ramblings (over 20 posts a day, on average) dropped the signal-to-noise ratio around here so low that several of the regulars simply stopped posting. That's why the moderators asked William to ban him; because he was quickly and callously destroying a "character" -- a community -- that had taken years to form. Believe me, he's not been missed.

The fact that you, temporary, hold him in such high esteem is quite frankly very troubling to me. However, so far you haven't been particularly rude, you've only posted a few times a week, rather than 20 times a day, and I seem to remember you even admitting a mistake or two. So long as you keep on like that I don't think there'll be any significant problems.

Quote:

Would the shadow predict the person's movement?

No, in fact, since the shadow is formed by the light that passes around the person, it will instead always lag somewhat behind the person's movements. An observer in the plane where the shadow is formed, rather than seeing the shadow predict the person's movements, would instead sometimes see the shadow moving backward relative to the person's movement!

--SMQ

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by temporary on Mar 13^th, 2008, 6:08pm

Interesting, but are you sure shadows move slower than the person or lag behind? I heard the shadow would move at speed of (the distance from the lamp to the wall)(the speed of the person)/(the distance from the lamp to the person).

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by ima1trkpny on Mar 13^th, 2008, 7:50pm

on 03/13/08 at 18:08:04, temporary wrote:

Interesting, but are you sure shadows move slower than the person or lag behind?

Positively... shadow's movements occur as a result of movement in the object (and the light source... but assuming that is constant, the only motion of the shadow will be in direct response to motion of the object and either way the shadow will lag behind whatever the change in position is)

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by SMQ on Mar 14^th, 2008, 4:08am

on 03/13/08 at 18:08:04, temporary wrote:

To clarify; the apparent speed of the shadow can be faster than the speed of the person, and yes even faster than light; your formula is accurate in that respect. However; if the person suddenly stops, the shadow will stop (slightly) after the person does because the shadow is caused by the light that passes by the person.

--SMQ

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by Master of Everything 42 on Mar 14^th, 2008, 6:40am

How does the shadow move faster than light, but it is the absence of light, so how would that work out?

As the shadow moves, Light takes the shadows place on one side, and is removed on the other, so the shadow moves at the speed of the incoming light, which is the speed of light?

Just tell me if i'm crazy, and ill try to reread this to make whatever sense we have put here.

************SMQ
am I high on your anoyance list?

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by SMQ on Mar 14^th, 2008, 12:18pm

on 03/14/08 at 06:40:03, Master of Everything 42 wrote:

How does the shadow move faster than light, but it is the absence of light, so how would that work out?

Consider an example with very slow light: ;)
http://www.dwarfrune.com/~smq/wu/shadow.gif

The light "waves" move outward from the center with a speed of http://www.ocf.berkeley.edu/~wwu/YaBBImages/symbols/c.gif, the speed of light. The red ball moves around the center with a speed of (1/2)http://www.ocf.berkeley.edu/~wwu/YaBBImages/symbols/c.gif, half the speed of light, but the center of the shadow appears to move around the outer wall with a speed of 2http://www.ocf.berkeley.edu/~wwu/YaBBImages/symbols/c.gif, twice the speed of light. Even though each ray of light only moves at the speed of light, the rays don't move "along" the wall to fill in the shadow; instead it's always the "next" ray that keeps filling in the edge of the shadow, and there's no constraint on how quickly the "next" ray can hit the wall after "this" ray does, so the shadow -- which is made up of "nothing" -- can appear to move at any speed at all without breaking the laws of physics.

Note also, how the shadow follows along the wall well behind the rotation of the ball. That's the time lag I was talking about above.

Quote:

am I high on your anoyance list?

As a moderator, it's probably best I don't name names on my mental annoyance list, but you've nothing to worry about. :)

--SMQ

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by Eigenray on Mar 14^th, 2008, 3:09pm

How does a shadow move, anyway? It's like talking about the hole of a donut.

Consider the opposite, for simplicity: I shine a flashlight at a wall that's very far away. If the wall is far enough away, I can make light on the wall move faster than light. But nothing is actually moving faster than light.

Or suppose you organize a bunch of people so that a person X meters away from you stands up at exactly X/1000000000 seconds past the hour. You will get a wave of people moving faster than light.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by temporary on Mar 15^th, 2008, 9:57pm

Getting matter such as people to move faster than light requires infinite time or infinite acceleration, both requiring infinite energy. With non-matter(not to be confused with anti-matter) it is a bit different; they can be manipulated to move faster than light in certain ways(like the one I mentioned earlier).

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by Eigenray on Mar 16^th, 2008, 12:23am

No, the wave is moving faster than light. The individual people aren't. Let the height of a particle at position x and time t be h(x,t)=A cos(at - bx). Then the wave speed is a/b, even though the speed of any given particle is |dh(x,t)/dt| http://www.ocf.berkeley.edu/~wwu/YaBBImages/symbols/le.gif a*A. We can simultaneously make the particles as slow as we want, and the wave as fast as we want.

Title: Re: 3 NEARLY IMPOSSIBLE RIDDLES
Post by temporary on Mar 25^th, 2008, 6:19pm

Sounds like a paradox that the wave is faster than each individual person, but I'll take your word for it anyway.