Re: The true crackpots


mluttgens@xxxxxxxxxx wrote:
> PD wrote:
> > mluttgens@xxxxxxxxxx wrote:
> > > PD wrote:
> > > > kenseto wrote:
> > > > > "PD" <TheDraperFamily@xxxxxxxxx> wrote in message
> > > > > news:1128718724.713401.183220@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> > > > > >
> > > > > > kenseto wrote:
> > > > > > > "PD" <TheDraperFamily@xxxxxxxxx> wrote in message
> > > > > > > news:1128626695.040370.318360@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> > > > > > > >
> > > > > > > > mluttgens@xxxxxxxxxx wrote:
> > > > > > > > > I presume that you recognize that the Fermilab experiments couldn't
> > > > > > > > > prove "length contraction". Indeed,
> > > > > > > > >
> > > > > > > > > "In a tevatron, those collisions occur of course head-on.
> > > > > > > > > Or, according to SR, physical bodies set in motion only shorten in
> > > > > the
> > > > > > > > > direction of their motion, meaning that a proton colliding head-on
> > > > > > > > > with an anti-proton will not observe "length contraction" of the
> > > > > > > > > anti-proton."
> > > > > > > > >
> > > > > > > > > Now you are referring to HERA papers. Please give me a *specific*
> > > > > > > > > reference where such contraction has been demonstrated. I am pretty
> > > > > > > > > well convinced that there are none, unless in your imagination, like
> > > > > > > > > with Fermilab :-)
> > > > > > > > >
> > > > > > > > > Marcel Luttgens
> > > > > > > >
> > > > > > > > What I'm doing is comparing jet cross sections in two environments:
> > > > > one
> > > > > > > > where the source is stationary in the lab (Tevatron) and one where the
> > > > > > > > source is moving in the lab (HERA). I don't think you're getting that
> > > > > > > > point.
> > > > > > > >
> > > > > > > > Let me see if I can find something that is a little more direct for
> > > > > > > > your tastes. Since this will be a bit older in the literature, I'll
> > > > > > > > have to search a little harder.
> > > > > > > >
> > > > > > > > At least you are willing to read in the library, which is commendable
> > > > > > > > and more than what folks like TomGee or Seto are either willing or
> > > > > able
> > > > > > > > to do.
> > > > > > >
> > > > > > > ROTFLOL....You don't even understand what length contraction means in
> > > > > SR. In
> > > > > > > SR the length contraction is not physical. It is an apparent geometric
> > > > > > > effect. It is the geometric projection of the moving rod onto the
> > > > > observer's
> > > > > > > frame.
> > > > > >
> > > > > > That's right. Because length itself is a projection of the interval
> > > > > > between two spacetime events onto the observer's frame. It is therefore
> > > > > > natural that two different observers will see two different lengths.
> > > > > > But SR also says there is no deeper or hidden meaning to length.
> > > > >
> > > > > So you agree that in SR length contraction is not physical.....right??
> > > >
> > > > In SR, length is not an intrinsic physical property. It is the result
> > > > of a measurement procedure, which intrinsically produces results that
> > > > depend on the motion of the observer.
> > > >
> > > > > >
> > > > > > > From the moving rod point of view the space in the direction of
> > > > > > > motion is contracted but the physical length of the rod remains the
> > > > > same.
> > > > > > > BTW your bogus premise of physical rod contraction has the following
> > > > > > > problem:
> > > > > > > 1. Two identical rods A and B and B accelerated away and becomes initial
> > > > > > > again.
> > > > > > > 2. A sees B is physically contracted during B journey.
> > > > > > > 3. B turns around and rejoins A. B's physical rod length returns to the
> > > > > same
> > > > > > > length as A.
> > > > > > > 4. That means that during the return trip B's physical length is
> > > > > physically
> > > > > > > expanded.
> > > > > > > 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.
> > > >
> > > > >
> > > > > >Assuming that is what would force the mental picture
> > > > > > of something physically happening to the rod to change its length or to
> > > > > > produce a distorted illusion of something physical that is not really
> > > > > > changing. Since the assumption is wrong, the mental picture is
> > > > > > misplaced.
> > > > >
> > > > > I didn't made that assumption. You did. You said that length contraction is
> > > > > measurable.
> > > >
> > > > Yes, indeed. Length is the result of a measurement. When you make this
> > > > measurement, however, you are not measuring an intrinsic property of
> > > > the object.
> > > >
> > > >
> > > > > All the experiments you cited are based on that space in the
> > > > > direction of motion is contracted. This is not the same as that a moving rod
> > > > > is contracted as you said.
> > > >
> > > > No, those experiments do NOT say which, or indeed if either, of space
> > > > or the rod in space is contracted. Those experiments just verify that
> > > > the measurements will produce what SR says the measurements will
> > > > produce. SR is what says there is no deeper physical meaning to the
> > > > length than what the experiment measures. No experiment is capable of
> > > > verifying that, though the experiments are capable of verifying every
> > > > *measurable* prediction of SR.
> > > >
> > > > > BTW space contraction is just a different way of describing that the moving
> > > > > frame has a higher state of absolute motion. Higher state of absolute motion
> > > > > produces a higher light path length for a physical rod. That, in turn,
> > > > > causes the rate of a moving clock to run slower than a stationary stay at
> > > > > home clock. That, in turn, means that a moving clock second has a longer
> > > > > duration (absolute time) than a stay at home clock second. That's why a fast
> > > > > moving moving upper atmosphere muon is able to reach the earth's
> > > > > surface......the (2.2 us) lifetime of the fast moving muon (in the fast
> > > > > muon's frame) represents (gamma*2.2 us) lifetime on the earth clock.
> > > > >
> > > > > >
> > > > > > 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?
> > > >
> > > > >
> > > > > Ken Seto
> > >
> > > 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.
> >
> > I don't care to try to fit my explanation into any of these categories,
> > nor defend any of the categories above. The way I explained it is, to
> > the best of my knowledge, an accurate representation of the truth. If
> > you find that this clashes with other explanations you've heard, this
> > (sadly) is not my problem nor anything I can help you with.
> >
> > >
> > > (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.
> >
> > As an example of what I said above, I don't even know what "true but
> > not really true" means. I maintain there is indeed a physical reality
> > to the measurement, and that the effect on the measurement due to the
> > motion of the measurer is very real. However, the attribution of the
> > measurement to some deeper physical attribute of an object is what is
> > unwarranted, unneeded, and (as it turns out) wrong to boot.
> >
>
> Wrong to boot? How do you know?

There is no way to access an inherent physical length of an object. It
is therefore a sterile concept, inherently not measurable and with no
bearing on any physics.

>
> > > If you want to convince yourself, just use time
> > > dilation to explain the MMX.
> >
> > Just a brief comment on this. You are apparently under the impression
> > that SR says that length contraction and time dilation happen
> > independently or under different circumstances. This is not the case.
> > In fact, what SR says is that the quantity
> > I^2 = t^2 - l^2 (where t is the measured time difference between two
> > events, and l is the measured spatial difference between two events)
> > will remain constant independent of the motion of the observer. Thus,
> > if in going from one observer to the other and length contraction is
> > observed (that is, l^2 changes), then *necessarily* time dilation is
> > also observed (that is, t^2 changes). A more in-depth explanation of
> > this point is available in Spacetime Physics, by Taylor and Wheeler.
> > Your claim that MMX is better explained as time dilation rather than as
> > length contraction would cause physicists to scratch their heads,
> > because they know that it is not a choice between one or the other, as
> > *both* happen as indeed they must.
> >
> > PD
>
> I am sorry to disagree, because a choice has to be made between time
> dilation and length contraction. *Both* can not happen!

I stand by the explantion that I just gave. If I^2 = t^2 - l^2 is
invariant, then one cannot have a change in l^2 in going from one frame
to another and not have also a change in t^2. The two are necessarily
coupled. A number of worked examples in Spacetime Physics illustrate
this beautifully. The length contraction is *always* accompanied by
time dilation in the *same* example.

>
> I said elsewhere that length contraction is a mathematical
> epiphenomenon.
> Take for instance the relation z = axy. Mathematically, you can claim
> that z=ax*y or z=x*ay, but physically, you are wrong if a only applies
> to x or to y. This is here the case, because the factor sqrt(1-v^2/c^2)
> applies to time (we are pretty sure of this, cf. for instance the time
> "dilation" of cosmic muons), not to length.

That is incorrect. The factor of sqrt(1-v^2/c^2) applies to both length
and time. Moreover, the phenomenon of the increased survival of cosmic
muons is understood *equivalently* as a time dilation or as a length
contraction. It is not one or the other. It is both.

> If an experimenter claimed
> that he detected length contraction, he would be wrong, because he
> would in fact have indirectly detected time slowing. I trust that you
> can understand this, in spite of what Taylor and Wheeler supposedly
> claimed.
>
>
> Marcel Luttgens

.

Relevant Pages

  • Re: The true crackpots
    ... >> depend on the motion of the observer. ... This does NOT mean that length contraction is a physical ... Length is the result of a measurement. ... this point is available in Spacetime Physics, ...
    (sci.physics.relativity)
  • Re: The true crackpots
    ... >>> Length contraction has been variously explained as ... >> to the measurement, and that the effect on the measurement due to the ... >> this point is available in Spacetime Physics, ... >> Your claim that MMX is better explained as time dilation rather than as ...
    (sci.physics.relativity)
  • Re: The true crackpots
    ... length is not an intrinsic physical property. ... This does NOT mean that length contraction is a physical ... Length is the result of a measurement. ... > this point is available in Spacetime Physics, ...
    (sci.physics.relativity)
  • Re: The true crackpots
    ... >>> depend on the motion of the observer. ... This does NOT mean that length contraction is a physical ... Length is the result of a measurement. ... > this point is available in Spacetime Physics, ...
    (sci.physics.relativity)
  • Re: The Constancy of Metres and Seconds
    ... Before we accept the contraction hypothesis of Lorentz we must ask a ... is the metre that has physically contracted according to the Lorentz ... (and also consistent with the laws of physics), ... Relativity postulates time dilation, a slowing of ...
    (sci.physics.relativity)