🚀 go-pugleaf

On Feb 26, 10:34 am, "Androcles" <Headmas...@Hogwarts.physics> wrote:
> "PD" <TheDraperFam...@gmail.com> wrote in message
>
> news:80f87552-ff2f-40dd-b853-5efca2157bfb@t66g2000hsf.googlegroups.com...
> On Feb 26, 8:35 am, Pentcho Valev <pva...@yahoo.com> wrote:
>
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> > On Feb 26, 2:12 pm, "G. L. Bradford" <glbra...@insightbb.com> wrote:
>
> > > "Pentcho Valev" <pva...@yahoo.com> wrote:
> > > > I am shocked by the idiocies Tom Roberts has written below. It turns
> > > > out Roberts is sillier than his zombies, much sillier than Dono in
> > > > particular. I should not have paid so much attention to zombie
> > > > Roberts' writings.
>
> > > > Pentcho Valev
> > > > pva...@yahoo.com
>
> > > > Dono wrote in sci.physics.relativity: 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.
>
> > > > Tom Roberts wrote: 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, one could start with the front door closed and the rear
> > > > door open, and then close the rear door before opening the front door
> > > > -- so in the barn frame both doors can be closed with the pole inside
> > > > (opening and closing must be VERY fast (:-)). In the pole frame, the
> > > > front door opens before the rear door closes, and the pole is never
> > > > wholly inside the barn (which appears to be shorter than the pole to
> > > > the pole observer). This example is every bit as much a demonstration
> > > > of the relativity of simultaneity as it is of length contraction.
>
> > > > 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.
>
> > > > Tom Roberts: 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.
> > > > Consider these two spatially-separated events: A) front door opens
> > > > with front end of pole still inside barn B) rear door closes with rear
> > > > end of pole already inside barn It is possible, given the conditions
> > > > of the gedanken, for B to precede A in the barn frame; in the pole
> > > > frame A precedes B.
>
> > > > Dono also said: the only way the pole would fit inside the barn is if
> > > > the pole got compressed.
>
> > > > Tom Roberts: This is not true. The way the pole can fit into the barn
> > > > when moving rapidly is that the time-ordering of spatially-separated
> > > > events is frame dependent: in the barn frame B precedes A, but in the
> > > > pole frame A precedes B. There's no need for the pole to be
> > > > "compressed". As I have often said around here, attempting to argue
> > > > via exhaustive enumeration nearly always fails. It did for you in this
> > > > case. TomRoberts
>
> > > The pole would not be compressed:
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> > > ||||||||
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> > > (|) = (| | | | | | | |)
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> > > -----------------------------
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> > > The pole's velocity, though, might just be a value negative to
> > > (apparent)
> > > zero rather than positive.
>
> > > GLB
>
> > Bradford sillier than Tom Roberts? Impossible. Nobody, not even string
> > theorists Brian Greene and Thibault Damour, can be sillier than Tom
> > Roberts. See the following discovery and tell me if you find it
> > extremely silly or extremely clever:
>
> | Neither. It is simply correct.
>
> You are simply stupid.

I *LOVE* drunken hecklers. Endless source of material to keep the
crowd happy.

PD