🚀 go-pugleaf

On 5 Mrz., 08:26, Pentcho Valev <pva...@yahoo.com> wrote:
> Hypnotists in Einstein criminal cult often hint that, by using
> Einstein's 1905 false light postulate, they can trap a long train
> inside a short tunnel:
>
> http://www.youtube.com/watch?v=VSRIyDfo_mY&mode=related&search
>
> and also a 80m long pole inside a 40m long barn:
>
> http://www.math.ucr.edu/home/baez/physics/Relativity/SR/barn_pole.html
> "These are the props. You own a barn, 40m long, with automatic doors
> at either end, that can be opened and closed simultaneously by a
> switch. You also have a pole, 80m long, which of course won't fit in
> the barn....So, as the pole passes through the barn, there is an
> instant when it is completely within the barn. At that instant, you
> close both doors simultaneously, with your switch. Of course, you open
> them again pretty quickly, but at least momentarily you had the
> contracted pole shut up in your barn."
>
> However in the end hypnotists always confuse the breathtaking news as
> in the above case where it is not at all clear why the doors should be
> reopened "pretty quickly" once the 80m long pole is safely trapped
> inside the 40m long barn. Only an extremely silly zombie can explain
> the miracle without any confusion:
>
> http://groups.google.com/group/sci.physics.relativity/browse_frm/thre...
> Tom Roberts, Mar 5, 2008:
>
> Dono wrote:
> > I am not denying length contraction,
>
> So take it one step at a time:
>
> Since you accept length contraction, in the barn frame the pole will
> be measured to be shorter than its proper length.
>
> In the barn frame, that measurement must be made simultaneously at the
> two ends of the pole (because the pole is moving relative to the barn
> frame).
>
> In the barn frame, at the instant when the two ends of the pole are
> measured, we know that the pole is located entirely between its two
> endpoints.
>
> Therefore, at the instant the measurement is made in the barn frame,
> there could be two closed doors at rest in the barn frame and outside
> the region between the pole's endpoints -- these doors would not
> intersect the pole at this instant.
>
> Since you accept length contraction, for a large enough speed of the
> pole relative to the barn frame, at the instant of measurement it is
> possible for the two endpoints plus the two closed doors to all be
> closer together than the proper length of the pole.
>
> Here is a drawing at the instant of measurement in the barn frame
> (note the pole is not at rest in this frame, so its proper length is
> for reference only):
>
>          proper length of pole (for reference only)
>   -------------------------------------------------------
>
>            |   -------------------------   |
>          Door1  measured length of pole  Door2
>
> Now it's just engineering to make the doors open and close fast enough
> to "trap" the pole in between the two closed doors, as in my earlier
> scenario. As this is a gedanken, we simply accept such engineering as
> possible and move on.
>
> Tom Roberts
> __________________________________
> [end of Tom Roberts' explanation]
>
> Pentcho Valev
> pva...@yahoo.com

I'm not good in understanding SR.
I only want to know if I look to the situation from the pole's frame:
So the distance between the barn doors is in any case too short, that
the pole can fit into the barn.
SR is symmetrical for time dilatation and length contraction, but not
for this situation.
Who can help me out.