🚀 go-pugleaf

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:
>
> |     |     |     |     |     |     |     |
>
> |    |    |    |    |    |    |    |
>
> |   |   |   |   |   |   |   |
>
> |  |  |  |  |  |  |  |
>
> | | | | | | | |
>
> ||||||||
>
> ||||
>
> ||
>
> |
>
> (|) = (|     |     |    |     |     |     |     |)
>
> -----------------------------
>
> 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:

http://groups.google.ca/group/sci.physics.relativity/browse_frm/thread/8034dc146100e32c?
Tom Roberts, Feb 1, 2006: "If it is ultimately discovered that the
photon has a nonzero mass (i.e. light in vacuum does not travel at the
invariant speed of the Lorentz transform), SR would be unaffected but
both Maxwell's equations and QED would be refuted (or rather, their
domains of applicability would be reduced)."

Pentcho Valev
pvalev@yahoo.com