Re: SR cannot determine Contraction

On Feb 25, 9:47 pm, Tom Roberts <tjroberts...@xxxxxxxxxxxxx> wrote:
Dono wrote:
There is a large class of thought experiments (the pole in the barn
being one of them) that rely on the misguided idea that length
contraction allows larger objects (like the pole) to fit inside
smaller enclosures (like the barn) as a byproduct ofrapid relative
motion. This is not the case.

I assume you intend "smaller" and "larger" to refer to objects' PROPER
length, along the axis of their relative motion.

Then you are wrong. The "pole and barn" gedanken is valid. Let me phrase
it without any accelerations -- a pole of length 2L can fit inside a
barn of length L, if it is moving faster than 0.866 c relative to the
barn, in this way: With pre-arranged timing in the barn frame,

This is not what I asked you. What I asked is can the pole fit in the
barn with both doors closed simultaneously in the barn frame?
In other words, do you , Tom Roberts, believe that uniform relative
motion makes objects shorter? Before you answer, I would like to
recommend the following reading (please pay close attention to the
reference from Michael janssen)

http://en.wikipedia.org/wiki/Length_contraction#A_trigonometric_effect.3F


Dono also said:

if you close both doors simultaneously in the barn frame, you
have trapped the pole inside the barn. This can only happen if the
pole has become physically shorter than the barn.

This is confusing, if not wrong -- you are using a PUN on "physically".
Yes, the pole itself is unchanged by measurements performed in the barn
frame, or doors closing, etc. But the PHYSICAL relationship between
front end of pole and front door, and the PHYSICAL relationship between
rear end of pole and rear door, can be such that in the barn frame the
pole fits in between the two closed doors for a (very) brief interval of
time. At least in a gedanken.


In a BAD gedanken , yes. In reality, no. This is the whole point.
Of course, we cannot run the experiment but your answer is key in
terms of understanding your position with respect to the nature of
length contraction.




.

Relevant Pages

  • Re: SR cannot determine Contraction
    ... frame without hitting the pole. ... The simultaneity of the doors closing ... In the frame in which the barn and the ...
    (sci.physics.relativity)
  • Re: Who hacked Kens presentation?
    ... pole does fit in the barn. ... interpretation of relativity, ...
    (sci.physics.relativity)
  • Re: Twin paradox with live webcams
    ... no constraint that the two twins be the same age. ... enough to fit completely in the barn, ... As far as he's concerned, the pole is indeed 80m long, is clearly ... close both doors simultaneously, with your switch. ...
    (sci.physics.relativity)
  • Re: On the physicality of length contraction
    ... physical accounts of what's going on, between the two frames. ... the barn, and the doors are shut simultaneously. ... the barn doors is experimentally verified in both frames. ... deny the claim the the pole was really shorter. ...
    (sci.physics.relativity)
  • Re: On the physicality of length contraction
    ... physical accounts of what's going on, between the two frames. ... the barn, and the doors are shut simultaneously. ... the barn doors is experimentally verified in both frames. ... deny the claim the the pole was really shorter. ...
    (sci.physics.relativity)