Re: SR predictions for PD

From: N:dlzc D:aol T:com \(dlzc\) (net_at_nospam.com)
Date: 03/10/05 

Date: Thu, 10 Mar 2005 10:17:18 -0700

Dear Rudy Drabek:

"Rudy Drabek" <erdrXs@aon.at> wrote in message
news:4230717d$0$18792$91cee783@newsreader02.highway.telekom.at...
> N:dlzc D:aol T:com (dlzc) schrieb:
>> Dear Rudy Drabek:
>>
>> "Rudy Drabek" <erdrXY@aon.at> wrote in message
>> news:42300ca0$0$7582$91cee783@newsreader02.highway.telekom.at...
>>
>>>>>So in this special case, how the marking
>>>>>of the distance is done is of importance.
>>>>>
>>>>>
>>>>>You are making too much out of nothing.
>>>>>Besides, the physical length of a ruler
>>>>>at its rest frame will remain unchanged
>>>>>after it is drawn out. Also in SR length
>>>>>contraction is not real. It a the projection
>>>>>of a ruler that is foreshortened. A ruler will
>>>>>return to its physical original length after
>>>>>traveling. Besides we can mark the
>>>>>distances with a meter rod.
>>>>
>>>>You have no idea what SR says about
>>>> distance measurement.
>>>
>>>Dear PD pls explain, where I am wrong.
>>>If I take a 1m rod or a draw out ruler
>>>makes no difference.
>>
>> "return to its physical original length"
>> It never changed, Rudy. *Observations* of a given length are
>> frame dependent. There is no requirement *in SR* for the
>> length to have "physically changed"... only LET does this.
>> And there is no experimentally verifiable way to differentiate
>> between them.
>>
> snip
>
> Thanks for expl. But now I understand really as PD said.

OK.

> If I go e.g. to Sirius with Gamma = 3 = .94c the ship
> *experiences* not *observes* the length contraction.

0.94 c in the ship's frame? Assuming you get up to speed, and
pass Earth. You will find using parallax that Sirius is 1/3 the
distance published "in the books". You will find that the
duration of the flight is consistent with 1/3 the distance, at
the aforementioned speed. I don't think there is a meaningful
difference between "experience" and "observe" in this context.

> BTW, I can't see my thread, only yr answer.
> Hopefully I see this -which was always visible-.

Looks great!

David A. Smith

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