Re: Androcles and Draper resume Einstein 1905

From: Androcles (dummy_at_dummy.net)
Date: 01/14/05 

Date: Fri, 14 Jan 2005 20:36:37 GMT

"Gregory L. Hansen" <glhansen@steel.ucs.indiana.edu> wrote in message
news:cs99n4$79r$1@rainier.uits.indiana.edu...
> In article <B0VFd.95629$C8.85428@fe3.news.blueyonder.co.uk>,
> Androcles <dummy@dummy.net> wrote:
>>
>>"PD" <pdraper@yahoo.com> wrote in message
>>news:1105729764.441171.196420@c13g2000cwb.googlegroups.com...
>>> Androcles wrote:
>>>> "PD" <pdraper@yahoo.com> wrote in message
>>>> news:1105722839.145822.145850@f14g2000cwb.googlegroups.com...
>
>>>>
>>>> > Androcles, your news reader seems incapable of indenting
>>>> > properly.
>>> Can
>>>> > you get that fixed?
>>>> Dunno. Sometimes it's fine. Other times it quits halfway through.
>>>> We need to trim some of the material that is already done with, I
>>> think.
>>>> No need for a list of who said what at the beginning.
>>>> I may be undergoing some medical procedures soon, so computer
>>>> diagnostics is not a current priority for me.
>>>> That means I may vanish, too. If I looks as if I'll drop dead, I'll
>>>> try to get a message through somehow.
>>>
>>> Fair enough. I did the same for you. Good luck.
>>>
>>>>
>>>> I'll try to leave the gist of the current sticking points evident.
>>>>
>>>>
>>>>
>>>>
>>>> >> >> Ok, so it can't be done for moving frames.
>>>> >> >> Why is Einstein even talking about it?
>>>> >> >
>>>> >> > It can be done for a moving frame. If you have a moving rod
>>>> >> > and
>>> you
>>>> >> > want to measure its length, simply go to the moving frame
>>>> >> > where
>>> it
>>>> > is
>>>> >> > at rest and repeat the same procedure.
>>>> >>
>>>> >> Oh, jump on the contracted length bus. Not easy, jumping
>>>> >> on a moving vehicle, y'know, but ok, it's a thought experiment.
>>>> >
>>>> > Not at all. The observer in k can measure the rod that is moving
>>>> > in
>>> K,
>>>> > because the rod is stationary in k. I didn't mean to imply that
>>>> > the
>>>> > observer in K becomes an observer in k, only that he goes to the
>>>> > observer in k for a consult. Not frame-jumping, just
>>>> > communication
>>>> > between the observers in the two frames.
>>>>
>>>> It is this very commnication that is the basis for our discussion.
>>>> Does the K-observer conclude the k-rod is shorter than the K-rod,
>>>> or not? Yes/No.
>>>
>>> Neither. K-observer says the moving rod is shorter than what the
>>> k-observer says it is. Each is following the procedure allowed to
>>> them
>>> for determining the length in their own frames. However, the
>>> K-observer
>>> cannot verify that the k-observer is following the procedure allowed
>>> to
>>> him in his frame. In fact, the K-observer observes that the
>>> k-observer
>>> is NOT following the procedure available to him in his frame, even
>>> though the k-observer insists that he is. And the converse is true
>>> as
>>> well: the k-observer cannot verify that the K-observer is following
>>> the
>>> procedure available to him for measuring length, even though the
>>> K-observer insists that he is.
>>>
>>> This is the nub of it. There IS no mutually agreeable procedure for
>>> measuring length that can be verified by all inertial observers. And
>>> hence length is not an intrinsic property of an object.
>>>
>>> This is all covered in the section in Einstein's paper in the
>>> section
>>> on the relativity of simultaneity.
>>
>>Does the K-observer conclude the k-rod is shorter than the K-rod,
>>or not? Yes/No.
>>There can be no ambiguity to the question.
>>"Neither" is not an acceptable answer.
>>I didn't ask you
>>"Does the k-observer conclude the K-rod is shorter than the k-rod?"
>>because I'm not interested in the answer at this time.
>>Now, please answer my question unanbiguously with a yes or a no.
>
> If I may *** in, I think Draper's point was that when K watches k
> measure
> the length, he won't agree that it was a measurement of the length!
> And
> vice versa. So when k gives K a measured length, K will say "Your
> number
> is smaller than mine, but I don't know what the hell it is. I watched
> you
> do it, and that's not how to measure a length."
>
That's fine, but k is carrying out an illegitimate procedure. I had
previously
agreed with Paul that the measurement can only be carried out when
the rod to be measured and the measuring rod were relatively at rest.
Observer K will not agree with observer k's guesstimate,
as you point out, but observer k himself will be uncertain.
Androcles.

>
> --
> "Then they placed the ark of the Lord on the cart; along with the box
> containing the golden mice and the images of the hemorrhoids."
> -- 1 Samuel 6:11

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