sci.astro
[Top] [All Lists]

Re: Ballistic Theory and the Sagnac Experiment

Subject: Re: Ballistic Theory and the Sagnac Experiment
From: ""
Date: 29 Mar 2006 19:20:40 -0800
Newsgroups: sci.astro, sci.physics.relativity, sci.physics
Jeff Root wrote:
> Jim Greenfield replied to Jeff Root:
>
> >> George Dishman wrote:
> >>
> >> > (3) AND (4) ARE QUESTIONS, NOT REASONS.
> >>
> >> Actually they're scenarios, which were described in order
> >> to pose and answer the questions.
> >
> > Agree. George is running interference
>
> I can't even guess what you mean by that remark.
>
> >> Of course, a scenario doesn't cause Doppler shift, any
> >> more than a question does.
> >>
> >> The question is:
> >> What causes the Doppler shift in scenario (3)?
> >
> > Make that question (a)
> > Answer: Change in position at instant of firing
>
> That's good.  Since the position at the instant of
> firing is the only thing that changes, that must be
> what causes the Doppler shift in this scenario.
>
> > Question (b)
> > What causes the Doppler shift in scenario (4)?
>
> Good question.  I should have included it in my post.
>
> > Answer: Increased bullet velocity
>
> Okay, that's interesting.  You say that the cause of the
> Doppler shift in scenario (4) is different from the cause
> in scenario (3).
>
> > .........(for an extra 1/2 mark, the position change
> > is incidental)
>
> Yes.  Scenario (4) has both a change in position and a
> change in speed at the instant of firing.
>
> Compare the amount of Doppler shift in the scenarios.
> In my animation, the times between bullet hits on the
> targets are:
>
> 1) 15.0 frames
> 2) 15.0 frames
> 3)  7.5 frames
> 4) 10.0 frames
>
> So the frequencies are:
>
> 1) 0.066 per frame
> 2) 0.066 per frame
> 3) 0.133 per frame
> 4) 0.100 per frame
>
> Cases (1) and (2) have no Doppler shift.  Case (3) has
> the most Doppler shift, and case (4) has some Doppler
> shift, but less than case (3).
>
> Case (4) has exactly the same change in position that
> case (3) has.  Shouldn't that change in position cause
> Doppler shift?  Since the position changes by the same
> amount in both cases, shouldn't it cause the same amount
> of Doppler shift in both cases?
>
> Why is the Doppler shift in case (4) less than that in
> case (3)?  The only difference between the two cases is
> that case (4) also has an increase in speed.  Somehow,
> the increased speed in case (4) caused the amount of
> Doppler shift to be less than it is in case (3).
>
> > Question (c)
> > Which of the two ACTUALLY caused the Doppler shift, and
> > where is the evidence?
> > Answer: (4), because it demonstrated increased kinetic
> > energy delivered to the target, whereas (3) did not.
>
> Again, (4) is a scenario, not a cause of Doppler shift.
> Scenarios do not cause Doppler shift.  If you mean that
> a change of speed causes Doppler shift, then say so.
>
> Sticking the word "ACTUALLY" into the sentence doesn't
> accomplish anything.  We agree that the Doppler shift in
> case (3) is caused by the change in position.  We haven't
> quite figured out yet what is going on in case (4).
>
> You say that the change in speed in case (4) causes the
> Doppler shift.  I point out that, if change in position
> causes Doppler shift in case (3), then it must also cause
> the same amount of Doppler shift in case (4).
>
> But case (4) has less Doppler shift than case (3), even
> though the only difference between the two is that there
> is an increase in speed in case (4).
>
> If an increase in speed causes Doppler shift, shouldn't
> there be more Doppler shift in case (4) than in case (3)?
>
> And if an increase in speed causes Doppler shift, why is
> there no Doppler shift at all in case (2)?

Most covered before, except to comment that your "belief" in the
animation
that it is a true representation of reality. I disagree!
 As v=frequency X wavelength, an increase in bullet v = corresponding
increase in frequency, and NO CHANGE indicated for wavelength.

I couldn't be bothered responding more to (3). My original analogy had
the machine
gun mounted on an aircraft. To discuss a "scenario" where a plane stops
to fire
is nothing short of pathetic.
The reason for the doppler is (4), as presented.

Jim G
c'=c+v

PS: Are you one of these individuals, who because they "saw it" on a
computer animation, is convinced they are looking at reality?
Hint: We are NOT about to be invaided by aliens.


<Prev in Thread] Current Thread [Next in Thread>