Re: The true crackpots

mluttgens@xxxxxxxxxx wrote:
> PD wrote:
....
> > > > > 5. That means that we will have both physical length contraction and
> > > > > expansion. Questions: How is B know when to physically contract and when
> > > to
> > > > > physically expand??
> > > > >
> > > >
> > > > You are assuming that length is a true physical property and not the
> > > > result of the projection of two spacetime events projected onto the
> > > > observer's frame.
> > >
> > > It was you who said that length contraction is physical and you said that
> > > many experiments have been performed to confirm this assertion.
> >
> > There have been many experiments that have verified that length, by any
> > reasonable definition of the same, depends on the motion of the
> > observer. This does NOT mean that length contraction is a physical
> > process, nor does it mean that length is an intrinsic physical property
> > of an object.
....


> > > > SR says that length is not an intrinsic physical property of an object.
> > >
> > > This is just a bogus assertion. You have no proof of that.
> >
> > I have no proof of what SR says? How about reading a few books on the
> > subject?

Proper length is an invariant. It can be regarded as an intrinsic
property of a material body.

>
> Length contraction has been variously explained as
>
> 1. true but not really true
> 2. real
> 3. not real
> 4. apparent
> 5. the result of the relativity of simultaneity
> 6. determined by measurement
> 7. a perspective effect
> 8. mathematical.
>
> (CF. http://perso.wanadoo.fr/mluttgens/sapere.htm#to )
>
> The one I prefer is "true but not really true". In fact,
> it is a mathematical ephiphenomenon with no physical reality
> whatsoever. If you want to convince yourself, just use time
> dilation to explain the MMX.

Physical theories NEVER deal with absolute true or real. They deal with
appearances. So, one could say: effectively true but not really true
(according to a particular theory)



>
> Marcel Luttgens

Don't use the word 'real' unless you include with it a definition of it
that will disambiguate its many possible meanings down to just one ---
the one you mean to use in this context. It's the theory and its basic
suppositions that tells you what's 'real' and what's 'illusion'.

The ST explanation of length contraction is the relativity of
simultaneity, and its obvious when presented on a Minkowski diagram.
IIRC, French uses this apparent contraction to expain the magnetic
field around a current-carrying wire.

.

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