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Re: Ballistic Theory and the Sagnac Experiment

Subject: Re: Ballistic Theory and the Sagnac Experiment
From: "George Dishman"
Date: 31 Mar 2006 01:08:45 -0800
Newsgroups: sci.astro, sci.physics.relativity, sci.physics
Henri Wilson wrote:
> On 30 Mar 2006 14:20:27 -0800, "jgreenfield@xxxxxxxxxxx" <jgreen@xxxxxxxxxxx>
> wrote:
> >George Dishman wrote:
> >> jgreenfield@xxxxxxxxxxx wrote:
> >> > George Dishman wrote:
> >> > > "jgreenfield@xxxxxxxxxxx" <jgreen@xxxxxxxxxxx> wrote in message
> >> > > news:1143605716.799659.97390@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> >> > > >
> >> > > > Jeff Root wrote:

<retaining only my argument for reference>

> >> > > >> What causes the Doppler shift in scenario (3)?
> >> > > >
> >> > > > Make that question (a)
> >> > > > Answer: Change in position at instant of firing
> >> > >
> >> > > Excellent, we can all agree on that. Since the
> >> > > change of position is the only difference between
> >> > > (1) and (3) we can say the change of position must
> >> > > be the cause of the Doppler shift in this case, but
> >> > > we cannot yet say it is the _only_ cause of Doppler
> >> > > shifts, there might be other effects that also have
> >> > > the same effect.
> >> > >
> >> > > > Question (b)
> >> > > > What causes the Doppler shift in scenario (4)?
> >> > >
> >> > > There are two _possible_ cause comparing (1) and
> >> > > (4), first the position has changed, which we know
> >> > > will cause a Doppler change, but also the bullet
> >> > > speed has changed and that might also have an effect.
> >> > > We need a way to test that.
> >> > >
> >> > > To find out if a change of bullet speed produces a
> >> > > Doppler shift, we would like a scenario in which it
> >> > > is the only possible cause and in particular change
> >> > > of position has been eliminated. We have that by
> >> > > comparing (1) with (2). In (2) the rifleman is
> >> > > moving forward when he fires so the bullet speed is
> >> > > increased but he runs back between shots so the
> >> > > firing position is constant. From Jeff's animation,
> >> > > the target hit rate is identical to the firing rate
> >> > > in (2) so there is _no_ Doppler shift in that case.
> >> > > We can therefore conclude that a change of bullet
> >> > > speed does _not_ cause a Doppler shift.

> >> > > ... the correct answer is that the Doppler
> >> > > shift is again caused by the change of position
> >> > > between shots. The rifleman's motion at the time
> >> > > of firing does also produce the change of impact
> >> > > energy which is therefore the "incidental" aspect.

> Jim, why don't you out George out of his misery by explaining the basis of his
> misconception.
>
> This is George's logic:
>
> 1) Bullet arrival frequency is dependent on the gun's velocity.
> 2) Bullet energy is dependent on gun's velocity.
> 3) Gun's change in position is dependent on gun's velocity.

Sorry Henry, you have completely failed to grasp
the argument. The logic goes like this:

 1) Comparing scenarios (1) and (3) we see that
    the bullet arrival frequency IS dependent on
    the change of the gun's location between
    shots since nothing else changes.

 2) Comparing scenarios (1) and (2) we see that
    the bullet arrival frequency IS NOT dependent
    on the bullet's speed since the bullet speed
    changes but the arrival rate doesn't and there
    is no other change that might mask the effect.

> Therefore, ACCORDING TO GEORGE, both bullet energy and bullet frequency are
> caused by the gun's change in position.

No, according to me we can separately attribute the
changed bullet arrival frequency to the change of gun
location between shots, and attribute the increased
target damage to the bullet speed, hence to the gun's
speed at the time of firing.

Summary:

 Doppler Shift:
  If there is no change of firing position then there
  is no change of arrival rate.

  If there is a change of firing position then there
  is a change of arrival rate and the amount of
  change depends on the bullet speed.

 Kinetic Energy:
  The target damage depends only on the speed
  of the bullet relative to the target at the time of
  impact, which in turn depends on the gun's
  speed at the time of firing.

George


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