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Sue...
science forum Guru

Joined: 08 May 2005
Posts: 2684

Posted: Tue Jul 11, 2006 5:20 pm    Post subject: Re: puzzle in relativity

cafei...@msn.com wrote:
 Quote: I found this here: http://www.geocities.com/ResearchTriangle/System/8956/problems/probs.htm "Five stuntmen are riding upon a large sled across an icy pond. In the center of the pond is a hole exactly the same size as the sled, and the stuntmen are travelling towards it at near the speed of light. When they reach the hole, a man standing beside the hole hits the sled with a sledgehammer to drive it into the hole. According to the stuntmen, the hole decreases in length due to the effects of special relativity, and thus they slide over and do not fall in. But the man standing beside the hole sees the length of the sled decrease due to relativity, and so the sled slips easily into the hole. Clearly the stuntmen or the hammer man cannot both be right, so what happens?"

If the inertia of the hammer is equvalent to the specific gravity of
the water in the pond, I'd say their wrist watches will probably
shatter. )

"Retarded potential"
http://farside.ph.utexas.edu/teaching/em/lectures/node50.html

Sue...
Phineas T Puddleduck
science forum Guru

Joined: 01 Jun 2006
Posts: 759

Posted: Tue Jul 11, 2006 5:21 pm    Post subject: Re: puzzle in relativity

<cafeinst@msn.com> wrote:

 Quote: I found this here: http://www.geocities.com/ResearchTriangle/System/8956/problems/probs.htm "Five stuntmen are riding upon a large sled across an icy pond. In the center of the pond is a hole exactly the same size as the sled, and the stuntmen are travelling towards it at near the speed of light. When they reach the hole, a man standing beside the hole hits the sled with a sledgehammer to drive it into the hole. According to the stuntmen, the hole decreases in length due to the effects of special relativity, and thus they slide over and do not fall in. But the man standing beside the hole sees the length of the sled decrease due to relativity, and so the sled slips easily into the hole. Clearly the stuntmen or the hammer man cannot both be right, so what happens?"

This is a form of the barn, or pole paradox

http://www.oberlin.edu/physics/dstyer/Einstein/SRBook.pdf

--
Relf's Law? -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
"Bullshit repeated to the limit of infinity asymptotically approaches
the odour of roses."
Corollary -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
³It approaches the asymptote faster, the more Œpseduos¹ you throw in
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
³Gravity is one of the four fundamental interactions. The classical
theory of gravity - Einstein's general relativity - is the subject
of this book.² : Hartle/ Gravity pg 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Jaffa cakes. Sweet delicious orange jaffa goodness, and an abject lesson
why parroting information from the web will not teach you cosmology.
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Puppet_Sock
science forum Guru Wannabe

Joined: 17 May 2005
Posts: 124

 Posted: Tue Jul 11, 2006 5:37 pm    Post subject: Re: puzzle in relativity cafeinst@msn.com wrote: [very old chestnut, often dealt with] The real puzzle is why so few people can discover the difference between sci.physics.relativity (where such is on topic) and sci.physics (where it is not). Socks
Dirk Van de moortel
science forum Guru

Joined: 01 May 2005
Posts: 3019

Posted: Tue Jul 11, 2006 5:38 pm    Post subject: Re: puzzle in relativity

 Quote: cafeinst@msn.com wrote: [very old chestnut, often dealt with] The real puzzle is why so few people can discover the difference between sci.physics.relativity (where such is on topic)

Even there it should be off topic by now.

Dirk Vdm

 Quote: and sci.physics (where it is not). Socks
Timo Nieminen
science forum Guru Wannabe

Joined: 12 May 2005
Posts: 244

Posted: Tue Jul 11, 2006 7:49 pm    Post subject: Re: puzzle in relativity

On Wed, 11 Jul 2006, cafeinst@msn.com wrote:

 Quote: I found this here: http://www.geocities.com/ResearchTriangle/System/8956/problems/probs.htm "Five stuntmen are riding upon a large sled across an icy pond. In the center of the pond is a hole exactly the same size as the sled, and the stuntmen are travelling towards it at near the speed of light. When they reach the hole, a man standing beside the hole hits the sled with a sledgehammer to drive it into the hole. According to the stuntmen, the hole decreases in length due to the effects of special relativity, and thus they slide over and do not fall in. But the man standing beside the hole sees the length of the sled decrease due to relativity, and so the sled slips easily into the hole. Clearly the stuntmen or the hammer man cannot both be right, so what happens?"

Ah, the rod-and-hole paradox, a close relative of the pole-and-barn

There are three events (that is, events in the (t,x,y,z) sense) to note:

A: front of sled reaches far side of hole
B: hammerblow
C: rear of sled reaches near side of hole

In the rest frame of the hole, B happens before A and after C. In the rest
frame of the sled, A happens even earlier before B, no problems there, and
C happens later - in the paradoxical situation, even later than B. The
effect of the hammer can't travel along the sled faster than the speed of
light, so before the effect of the hammerblow is felt at the rear of the
sled, it's already over the hole.

For more fun, replace the hammer with a plug equal to the hole in size,
and in the hole frame, lower it to plug the hole when the sled is over the
hole. In the hole frame, all parts of the plug are lowered simultaneously,
and the bottom of the plug is horizontal. In the sled frame, the far end
of the plug comes down first, and by the time the near end of the plug
comes down, the rear end of the sled is over the hole.

--
E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html
xxein@bellsouth.net
science forum Guru Wannabe

Joined: 12 Sep 2005
Posts: 272

Posted: Wed Jul 12, 2006 2:14 am    Post subject: Re: puzzle in relativity

cafeinst@msn.com wrote:
 Quote: I found this here: http://www.geocities.com/ResearchTriangle/System/8956/problems/probs.htm "Five stuntmen are riding upon a large sled across an icy pond. In the center of the pond is a hole exactly the same size as the sled, and the stuntmen are travelling towards it at near the speed of light. When they reach the hole, a man standing beside the hole hits the sled with a sledgehammer to drive it into the hole. According to the stuntmen, the hole decreases in length due to the effects of special relativity, and thus they slide over and do not fall in. But the man standing beside the hole sees the length of the sled decrease due to relativity, and so the sled slips easily into the hole. Clearly the stuntmen or the hammer man cannot both be right, so what happens?"

cafeinst@msn.com wrote:
 Quote: I found this here: http://www.geocities.com/ResearchTriangle/System/8956/problems/probs.htm "Five stuntmen are riding upon a large sled across an icy pond. In the center of the pond is a hole exactly the same size as the sled, and the stuntmen are travelling towards it at near the speed of light. When they reach the hole, a man standing beside the hole hits the sled with a sledgehammer to drive it into the hole. According to the stuntmen, the hole decreases in length due to the effects of special relativity, and thus they slide over and do not fall in. But the man standing beside the hole sees the length of the sled decrease due to relativity, and so the sled slips easily into the hole. Clearly the stuntmen or the hammer man cannot both be right, so what happens?"

xxein: If you want an absolute answer, then you have to find the
absolute.

The universe is expanding. Why?

There is a gravity. Why?

way, you will satisfy yourself without being subject to some of the
moronic opinions presented by this group.

Iow, even at it's best, this ng is just an opinion fostered mainly by
the Einsteinian, but it is in no way referrential to what is objective
or subjective in thought.

Expansion and gravity aside, why would relative velocity be non-linear?
Why is time and length different between frames of measurement? What
is the correct concept that will support everything we measure and
reflect outward with a simple relationship to an objective universal
activity?

Simple subjectively-based one-liners cannot make the connection. Nor
can a subjectively-based soup.

The only thing that should satisfy you is to build an objectively-based
physic from scratch.
If you are successful, you will recognise the subjectively-based
theories as subsets.

Fear not. The universe has only one set of laws. Seek them and all
other questions can be anawered (not really, but to the extent our
present science can let us determine).

So which is larger? The sled or hole? I prefer barn and pole to make

Which is really and absolutely moving faster than the other along the
axis of consideration?

If you answer this, you are well beyond a willy-nilly relativity and
into an absolute consideration of how a relativity exists.

I won't tell you how to do your examination of all this (other than the
above) because I want to see your thought process at work.

Craig Feinstein
science forum Guru Wannabe

Joined: 24 Mar 2005
Posts: 100

Posted: Wed Jul 12, 2006 4:20 pm    Post subject: Re: puzzle in relativity

xxein@bellsouth.net wrote:
 Quote: cafeinst@msn.com wrote: I found this here: http://www.geocities.com/ResearchTriangle/System/8956/problems/probs.htm "Five stuntmen are riding upon a large sled across an icy pond. In the center of the pond is a hole exactly the same size as the sled, and the stuntmen are travelling towards it at near the speed of light. When they reach the hole, a man standing beside the hole hits the sled with a sledgehammer to drive it into the hole. According to the stuntmen, the hole decreases in length due to the effects of special relativity, and thus they slide over and do not fall in. But the man standing beside the hole sees the length of the sled decrease due to relativity, and so the sled slips easily into the hole. Clearly the stuntmen or the hammer man cannot both be right, so what happens?" cafeinst@msn.com wrote: I found this here: http://www.geocities.com/ResearchTriangle/System/8956/problems/probs.htm "Five stuntmen are riding upon a large sled across an icy pond. In the center of the pond is a hole exactly the same size as the sled, and the stuntmen are travelling towards it at near the speed of light. When they reach the hole, a man standing beside the hole hits the sled with a sledgehammer to drive it into the hole. According to the stuntmen, the hole decreases in length due to the effects of special relativity, and thus they slide over and do not fall in. But the man standing beside the hole sees the length of the sled decrease due to relativity, and so the sled slips easily into the hole. Clearly the stuntmen or the hammer man cannot both be right, so what happens?" xxein: If you want an absolute answer, then you have to find the absolute. The universe is expanding. Why? There is a gravity. Why? Invoke your best-guess mechanism and solve down to your question. That way, you will satisfy yourself without being subject to some of the moronic opinions presented by this group. Iow, even at it's best, this ng is just an opinion fostered mainly by the Einsteinian, but it is in no way referrential to what is objective or subjective in thought. Expansion and gravity aside, why would relative velocity be non-linear? Why is time and length different between frames of measurement? What is the correct concept that will support everything we measure and reflect outward with a simple relationship to an objective universal activity? Simple subjectively-based one-liners cannot make the connection. Nor can a subjectively-based soup. The only thing that should satisfy you is to build an objectively-based physic from scratch. If you are successful, you will recognise the subjectively-based theories as subsets. Fear not. The universe has only one set of laws. Seek them and all other questions can be anawered (not really, but to the extent our present science can let us determine). So which is larger? The sled or hole? I prefer barn and pole to make an answer to this. Which is really and absolutely moving faster than the other along the axis of consideration? If you answer this, you are well beyond a willy-nilly relativity and into an absolute consideration of how a relativity exists. I won't tell you how to do your examination of all this (other than the above) because I want to see your thought process at work. Please keep me informed.

I now believe in relativity theory. I was completely convinced by
http://www.geocities.com/ResearchTriangle/System/8956/Bondi/intro.htm

This description puts relativity theory in line with common sense. In
fact, if relativity theory were not true, this would be
counter-intuitive.

Craig
PD
science forum Guru

Joined: 03 May 2005
Posts: 4363

Posted: Wed Jul 12, 2006 7:31 pm    Post subject: Re: puzzle in relativity

cafeinst@msn.com wrote:

 Quote: I now believe in relativity theory. I was completely convinced by http://www.geocities.com/ResearchTriangle/System/8956/Bondi/intro.htm This description puts relativity theory in line with common sense. In fact, if relativity theory were not true, this would be counter-intuitive.

A word of caution. Being able to follow a simple derivation is
wonderful. However, it's a mistake to think that if it's correct, it
will be intuitive. There is lots of behavior in nature that is simply
not intuitive. Quantum mechanics springs to mind here. The test for
correctness is not whether it is intuitive but whether it matches
experiment. There is no replacement test.

PD
Jeffâ€¦Relf
science forum Guru Wannabe

Joined: 03 Apr 2006
Posts: 114

 Posted: Thu Jul 13, 2006 12:21 pm    Post subject: It'd take a hypernova to pound the stunt-men into the hole. Hi Cafeinst, The Relativistic_Mass of the stunt-men would be astronomical, it'd take a hypernova to pound them into that hole in the ice; so the size of the hole is of no consequence... zip, zero, nada.
Phineas T Puddleduck
science forum Guru

Joined: 01 Jun 2006
Posts: 759

Posted: Thu Jul 13, 2006 12:24 pm    Post subject: Re: It'd take a hypernova to pound the stunt-men into the hole.

In article <Jeff_Relf_2006_Jul_13_f2bt@Cotse.NET>, Jeff’Ä¶Relf
<Jeff_Relf@Yahoo.COM> wrote:

 Quote: Hi Cafeinst, The Relativistic_Mass of the stunt-men would be astronomical, it'd take a hypernova to pound them into that hole in the ice; so the size of the hole is of no consequence... zip, zero, nada.

Oh shut up buffoon.

--
Relf's Law? -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
"Bullshit repeated to the limit of infinity asymptotically approaches
the odour of roses."
Corollary -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
³It approaches the asymptote faster, the more Œpseduos¹ you throw in
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
³Gravity is one of the four fundamental interactions. The classical
theory of gravity - Einstein's general relativity - is the subject
of this book.² : Hartle/ Gravity pg 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Jaffa cakes. Sweet delicious orange jaffa goodness, and an abject lesson
why parroting information from the web will not teach you cosmology.
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Bill Snyder
science forum beginner

Joined: 08 May 2005
Posts: 38

Posted: Thu Jul 13, 2006 1:08 pm    Post subject: Re: It'd take a hypernova to pound the stunt-men into the hole.

On Thu, 13 Jul 2006 13:24:49 +0100, Phineas T Puddleduck

 Quote: In article , Jeff’Ä¶Relf Jeff_Relf@Yahoo.COM> wrote: Hi Cafeinst, The Relativistic_Mass of the stunt-men would be astronomical, it'd take a hypernova to pound them into that hole in the ice; so the size of the hole is of no consequence... zip, zero, nada. Oh shut up buffoon.

You can hardly expect a thought experiment to appeal to someone
incapable of thinking.
--
Bill Snyder [This space unintentionally left blank.]
Phineas T Puddleduck
science forum Guru

Joined: 01 Jun 2006
Posts: 759

Posted: Thu Jul 13, 2006 1:10 pm    Post subject: Re: It'd take a hypernova to pound the stunt-men into the hole.

In article <r8hcb2l1hbmq3m9qp31u8udt702um1f4dh@4ax.com>, Bill Snyder
<bsnyder@airmail.net> wrote:

 Quote: On Thu, 13 Jul 2006 13:24:49 +0100, Phineas T Puddleduck phineaspuddleduck@googlemail.com_NOSPAM> wrote: In article , Jeff’Ä¶Relf Jeff_Relf@Yahoo.COM> wrote: Hi Cafeinst, The Relativistic_Mass of the stunt-men would be astronomical, it'd take a hypernova to pound them into that hole in the ice; so the size of the hole is of no consequence... zip, zero, nada. Oh shut up buffoon. You can hardly expect a thought experiment to appeal to someone incapable of thinking.

Point taken We didn't take into account the PRESSURE of the hammer
did we ;-)

--
Relf's Law? -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
"Bullshit repeated to the limit of infinity asymptotically approaches
the odour of roses."
Corollary -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
³It approaches the asymptote faster, the more Œpseduos¹ you throw in
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
³Gravity is one of the four fundamental interactions. The classical
theory of gravity - Einstein's general relativity - is the subject
of this book.² : Hartle/ Gravity pg 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Jaffa cakes. Sweet delicious orange jaffa goodness, and an abject lesson
why parroting information from the web will not teach you cosmology.
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Jeffâ€¦Relf
science forum Guru Wannabe

Joined: 03 Apr 2006
Posts: 114

 Posted: Thu Jul 13, 2006 1:27 pm    Post subject: Re: It'd take a hypernova to pound the stunt-men into the hole. Hi Bill_Snyder, Including length-contraction but ignoring time-dilation and Relativistic_Mass is a Fuck_Up not a thought-experiment.
Phineas T Puddleduck
science forum Guru

Joined: 01 Jun 2006
Posts: 759

Posted: Thu Jul 13, 2006 1:56 pm    Post subject: Re: It'd take a hypernova to pound the stunt-men into the hole.

In article <Jeff_Relf_2006_Jul_13_SRuF@Cotse.NET>, Jeff’Ä¶Relf
<Jeff_Relf@Yahoo.COM> wrote:

 Quote: Hi Bill_Snyder, Including length-contraction but ignoring time-dilation and Relativistic_Mass is a Fuck_Up not a thought-experiment.

You really are a fucking idiot. The thought experiment is ALL to do
with length contraction.... Grow some brain cells.

--
Relf's Law? -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
"Bullshit repeated to the limit of infinity asymptotically approaches
the odour of roses."
Corollary -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
³It approaches the asymptote faster, the more Œpseduos¹ you throw in
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
³Gravity is one of the four fundamental interactions. The classical
theory of gravity - Einstein's general relativity - is the subject
of this book.² : Hartle/ Gravity pg 1
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Jaffa cakes. Sweet delicious orange jaffa goodness, and an abject lesson
why parroting information from the web will not teach you cosmology.
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Bill Snyder
science forum beginner

Joined: 08 May 2005
Posts: 38

Posted: Thu Jul 13, 2006 6:12 pm    Post subject: Re: It'd take a hypernova to pound the stunt-men into the hole.

On 13 Jul 2006 13:27:08 GMT, Jeff…Relf <Jeff_Relf@Yahoo.COM> wrote:

 Quote: Hi Bill_Snyder, Including length-contraction but ignoring time-dilation and Relativistic_Mass is a Fuck_Up not a thought-experiment. Hi Jerk_Wad_Underscore_Queen,

Then just assume that the hammer's speed in the rest frame results in
an identical time dilation and enough momentum for it to do the job.
Of course, this has the disadvantage that it doesn't allow you to
weasel out of examining the situation at all . . .
--
Bill Snyder [This space unintentionally left blank.]

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