From: Androcles on

"dlzc" <dlzc1(a)cox.net> wrote in message
news:61cef5d0-9103-4e95-b9bb-a81eeb738aab(a)b1g2000prc.googlegroups.com...
Dear Ste:

On Feb 16, 6:46 am, Ste <ste_ro...(a)hotmail.com> wrote:
> On 16 Feb, 03:40, mpalenik <markpale...(a)gmail.com> wrote:
....
> > You've brought the detector at rest with respect
> > to the source. They're now both in the same
> > reference frame. The only way SR says that you
> > should observe anything "unusual" is if the
> > source and detector are moving with respect to
> > each other.
>
> Perhaps. But what is confusing me is this
> "constant speed of light" postulate.

This postulate is superfluous. The constancy of the speed of light is
the result of Maxwell's equations (the laws of physics that are the
same, regardless of source speed), and has good agreement with
reality, with the proviso that only the two-way speed of light can
ever be measured.

David A. Smith
===========================================
I checked the dictionary for 'ridiculous', and 'superfluous' didn't come up.


absurd, preposterous laughable , ludicrous, comic, comical





From: Androcles on

"dlzc" <dlzc1(a)cox.net> wrote in message
news:61cef5d0-9103-4e95-b9bb-a81eeb738aab(a)b1g2000prc.googlegroups.com...
Dear Ste:

On Feb 16, 6:46 am, Ste <ste_ro...(a)hotmail.com> wrote:
> On 16 Feb, 03:40, mpalenik <markpale...(a)gmail.com> wrote:
....
> > You've brought the detector at rest with respect
> > to the source. They're now both in the same
> > reference frame. The only way SR says that you
> > should observe anything "unusual" is if the
> > source and detector are moving with respect to
> > each other.
>
> Perhaps. But what is confusing me is this
> "constant speed of light" postulate.

This postulate is superfluous. The constancy of the speed of light is
the result of Maxwell's equations (the laws of physics that are the
same, regardless of source speed), and has good agreement with
reality, with the proviso that only the two-way speed of light can
ever be measured.

David A. Smith

From: Peter Webb on

"dlzc" <dlzc1(a)cox.net> wrote in message
news:61cef5d0-9103-4e95-b9bb-a81eeb738aab(a)b1g2000prc.googlegroups.com...
Dear Ste:

On Feb 16, 6:46 am, Ste <ste_ro...(a)hotmail.com> wrote:
> On 16 Feb, 03:40, mpalenik <markpale...(a)gmail.com> wrote:
....
> > You've brought the detector at rest with respect
> > to the source. They're now both in the same
> > reference frame. The only way SR says that you
> > should observe anything "unusual" is if the
> > source and detector are moving with respect to
> > each other.
>
> Perhaps. But what is confusing me is this
> "constant speed of light" postulate.

This postulate is superfluous. The constancy of the speed of light is
the result of Maxwell's equations (the laws of physics that are the
same, regardless of source speed), and has good agreement with
reality, with the proviso that only the two-way speed of light can
ever be measured.

David A. Smith

________________________________
Huh? The one way speed of light has been measured many times. The first
reasonably accurate measurement of the speed of light was in fact a one way
measurement; the timing of the occultations of Jupiter's moons.


From: Inertial on

"Ste" <ste_rose0(a)hotmail.com> wrote in message
news:e6adef4c-9c7e-421a-8a35-097ef868a9e4(a)k19g2000yqc.googlegroups.com...
> On 16 Feb, 03:40, mpalenik <markpale...(a)gmail.com> wrote:
>> On Feb 15, 6:49 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>>
>>
>>
>>
>>
>> > On 15 Feb, 23:05, "Inertial" <relativ...(a)rest.com> wrote:
>>
>> > > "mpalenik" <markpale...(a)gmail.com> wrote in message
>>
>> > >news:90a5859a-7eaf-41ef-bda5-133028662cf0(a)h17g2000vbd.googlegroups.com...
>>
>> > > > On Feb 15, 4:09 pm, PD <thedraperfam...(a)gmail.com> wrote:
>> > > >> On Feb 15, 2:41 pm, dlzc <dl...(a)cox.net> wrote:
>>
>> > > >> > Dear PD:
>>
>> > > >> > On Feb 15, 12:20 pm, PD <thedraperfam...(a)gmail.com> wrote:
>> > > >> > ...
>>
>> > > >> > > I'm sorry, I misrepresented the diagram. They would arrive at
>> > > >> > > different times but there would be no red/blue-shifting.
>>
>> > > >> > The emitters are in a rest frame, and the detectors are (later)
>> > > >> > in a
>> > > >> > frame with +v and -v. Better think again.
>>
>> > > >> > Same situation would obtain the S1 and D2 were stationary, D1
>> > > >> > and D2
>> > > >> > were moving at v, and the pulses were sent through some form of
>> > > >> > clock
>> > > >> > synchronization (no more complex than obtaining "rigid"
>> > > >> > geometry).
>>
>> > > >> > David A. Smith
>>
>> > > >> Perhaps I don't understand the (revised) picture, either.
>> > > >> My understanding was that S1, D1, S2 and D2 are initially all at
>> > > >> rest
>> > > >> in a common reference frame. Then, after emission, they are all
>> > > >> briefly accelerated in the same direction and in the plane of the
>> > > >> apparatus, and then brought back to rest in the initial reference
>> > > >> frame. In this case, the whole apparatus has been simply displaced
>> > > >> while the photons are in transit.
>>
>> > > > Yes, this is the revised picture. For some reason, I was thinking
>> > > > the
>> > > > motion was supposed to be perpendicular to the plane of the
>> > > > apparatus,
>> > > > but when I thought about it later, I specifically remembered a post
>> > > > from Ste where he said this was not the case (that he meant "up",
>> > > > as
>> > > > in "up on the screen"). This is how I understand the description
>> > > > as
>> > > > well.
>>
>> > > Its much simpler now. The pulses arrive at different times, because
>> > > the
>> > > detectors have been moved (one closer to where pulses was emitted,
>> > > the other
>> > > further way from it). And no doppler as the detectors are at rest
>> > > again by
>> > > the time the pulses gets to it.
>>
>> > So do we have a consensus on the matter then? The pulse has an
>> > independent existence from its source so that, once emitted, a
>> > translation of the actual source does not translate the 'apparent'
>> > source of a pulse already in flight?
>>
>> I'm not sure what you're trying to prove here.
>
> I'm not trying to prove anything. I'm trying to form some sort of
> consistent picture in my own head of how this setup behaves under
> different transformations.
>
>
>
>> You've brought the
>> detector at rest with respect to the source. They're now both in the
>> same reference frame. The only way SR says that you should observe
>> anything "unusual" is if the source and detector are moving with
>> respect to each other.
>
> Perhaps. But what is confusing me is this "constant speed of light"
> postulate.
>
>
>
>> Translations in relativity--or in fact, even in pure mathematics--are
>> very different things than rotations, and picking the detector up and
>> putting it somewhere else without changing the speed is a pure
>> translation. You don't even need relativity in this scenario, where
>> everything is at rest with respect to everything else.
>
> Yes, but we're going to get to the bit where relativity is required in
> a moment.
>
> Now, let us suppose we have two source and two detectors again:
>
> D1 D2 D3
>
>
>
> S1 S2 S3
>
>
> S1 and D1 are stationary in the frame, and do not move. D2 is also
> stationary in the frame. S2, S3, and D3 are all moving in the y+
> direction (i.e. same as the previous scenario) at a constant speed
> (which is close to 'c'). Just to be sure we understand, the same setup
> a few moments back in time would have looked like this:
>
>
> D1 D2
>
> D3
>
>
> S1
>
> S2 S3
>

Your diagram contradicts your description .. you show in the diagram that S1
and D1 have moved apart (as have S3 and D3), but you said they do not. D3,
S2 and S3 have also moved to the left. I think you need to draw your
diagram again.


From: dlzc on
Dear Peter Webb:

On Feb 16, 3:35 pm, "Peter Webb"
<webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote:
> "dlzc" <dl...(a)cox.net> wrote in message
> news:61cef5d0-9103-4e95-b9bb-a81eeb738aab(a)b1g2000prc.googlegroups.com...
> On Feb 16, 6:46 am, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > On 16 Feb, 03:40, mpalenik <markpale...(a)gmail.com> wrote:
> ...
> > > You've brought the detector at rest with respect
> > > to the source. They're now both in the same
> > > reference frame. The only way SR says that you
> > > should observe anything "unusual" is if the
> > > source and detector are moving with  respect to
> > > each other.
>
> > Perhaps. But what is confusing me is this
> > "constant speed of light" postulate.
>
> This postulate is superfluous.  The constancy of
> the speed of light is the result of Maxwell's
> equations (the laws of physics that are the
> same, regardless of source speed), and has
> good agreement with reality, with the proviso
> that only the two-way speed of light can
> ever be measured.
>
> ________________________________
> Huh? The one way speed of light has been
> measured many times.

Using a clock synchronization procedure that is equivalent to
Einstein's method, which establishes a "two-way light measured
experiment space". So all they can return is an average TWLS.

> The first reasonably accurate measurement of
> the speed of light was in fact a one way
> measurement; the timing of the occultations of
> Jupiter's moons.

Given a TWLS measurement of Juptier's orbital radius, Earth's, the
moon's, and angles Sun to Jupiter, and all the *inferred / impressed*
TWLS geometry...

David A. Smith