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From: Inertial on 13 Mar 2010 03:19

"Bruce Richmond" <bsr3997(a)my-deja.com> wrote in message
news:a7f0a513-521d-4b37-a746-104e419dd704(a)g4g2000yqa.googlegroups.com...
> On Mar 12, 10:56 pm, mpc755 <mpc...(a)gmail.com> wrote:
>> On Mar 12, 9:02 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote:
>>
>>
>>
>>
>>
>> > On Mar 11, 7:42 am, mpc755 <mpc...(a)gmail.com> wrote:
>>
>> > > On Mar 10, 11:30 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote:
>>
>> > > > On Mar 10, 9:18 pm, mpc755 <mpc...(a)gmail.com> wrote:
>>
>> > > > > On Mar 10, 8:45 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote:
>>
>> > > > > > On Mar 10, 8:10 pm, mpc755 <mpc...(a)gmail.com> wrote:
>>
>> > > > > > > On Mar 10, 7:45 pm, Bruce Richmond <bsr3...(a)my-deja.com>
>> > > > > > > wrote:
>>
>> > > > > > > > On Mar 10, 9:36 am, mpc755 <mpc...(a)gmail.com> wrote:
>>
>> > > > > > > > > On Mar 10, 8:05 am, "Inertial" <relativ...(a)rest.com>
>> > > > > > > > > wrote:
>>
>> > > > > > > > > > "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au>
>> > > > > > > > > > wrote in message
>>
>> > > > > > > > > >news:4b970c19$0$8039$afc38c87(a)news.optusnet.com.au...
>>
>> > > > > > > > > > > I know I still have a long way to go but my goal here
>> > > > > > > > > > > is to truely
>> > > > > > > > > > > understand SR, not to just parrot explainations. LET
>> > > > > > > > > > > helped me see
>> > > > > > > > > > > that the math of SR is correct, but I also realize it
>> > > > > > > > > > > has become a
>> > > > > > > > > > > hiderence in understanding SR.
>>
>> > > > > > > > > > > ________________________________
>> > > > > > > > > > > Good. There is one key insight which makes the jump
>> > > > > > > > > > > from LET to SR a
>> > > > > > > > > > > little easier (in my opinion).
>>
>> > > > > > > > > > > For all the talk of relative motion against the ether
>> > > > > > > > > > > in LET, the
>> > > > > > > > > > > equations work out exactly the same whatever you
>> > > > > > > > > > > choose as the rest frame
>> > > > > > > > > > > of the ether. So the actual rest frame of the ether
>> > > > > > > > > > > cannot be detected
>> > > > > > > > > > > within LET.
>>
>> > > > > > > > > > That's right. That's what Dono doesn't get.
>>
>> > > > > > > > > > > Its only a small hop, skip and jump from saying that
>> > > > > > > > > > > "it cannot be
>> > > > > > > > > > > detected" to "it doesn't exist".
>>
>> > > > > > > > > > Or at least 'it doesn't matter'.
>>
>> > > > > > > > > > Once you go beyond just the aether frame, and relating
>> > > > > > > > > > frames directly to
>> > > > > > > > > > it, LET becomes more of a hinderance than a help
>>
>> > > > > > > > > > LET tells you (for instance) that even though objects
>> > > > > > > > > > at rest in frame A may
>> > > > > > > > > > be more length compressed and time slowed than those in
>> > > > > > > > > > frame B (where A
>> > > > > > > > > > moves faster in the aether frame than B) .. yet A will
>> > > > > > > > > > see objects at rest
>> > > > > > > > > > in B as being more contracted and time dilated than its
>> > > > > > > > > > own. Which really
>> > > > > > > > > > confuses those who use the simple 'motion in the aether
>> > > > > > > > > > shrinks and slows
>> > > > > > > > > > things' idea of LET as a way to 'understand' into a
>> > > > > > > > > > spin. You end up with a
>> > > > > > > > > > strange combination of real compression and apparent
>> > > > > > > > > > contraction, real
>> > > > > > > > > > slowing and apparent time dilaton. Its not really
>> > > > > > > > > > helpful :):)
>>
>> > > > > > > > > It is helpful in that it gets 'us' closer to
>> > > > > > > > > understanding what occurs
>> > > > > > > > > to objects as they move with respect to the aether.
>>
>> > > > > > > > > The issue with LET is everything is relative.
>>
>> > > > > > > > > For example, "the state of the [ether] is at every place
>> > > > > > > > > determined by
>> > > > > > > > > connections with the matter and the state of the ether in
>> > > > > > > > > neighbouring
>> > > > > > > > > places" - Albert Einstein.
>>
>> > > > > > > > You like Einstein quotes about the ether so try this one:
>>
>> > > > > > > >http://www-groups.dcs.st-and.ac.uk/~history/Extras/Einstein_ether.html
>>
>> > > > > > > > "We may assume the existence of an ether; only we must give
>> > > > > > > > up
>> > > > > > > > ascribing a definite state of motion to it" - Albert
>> > > > > > > > Einstein.
>>
>> > > > > > > "If the existence of such floats for tracking the motion of
>> > > > > > > the
>> > > > > > > particles of a fluid were a fundamental impossibility in
>> > > > > > > physics - if,
>> > > > > > > in fact nothing else whatever were observable than the shape
>> > > > > > > of the
>> > > > > > > space occupied by the water as it varies in time, we should
>> > > > > > > have no
>> > > > > > > ground for the assumption that water consists of movable
>> > > > > > > particles.
>> > > > > > > But all the same we could characterise it as a medium."
>>
>> > > > > > > "[extended physical objects to which the idea of motion
>> > > > > > > cannot be
>> > > > > > > applied] may not be thought of as consisting of particles
>> > > > > > > which allow
>> > > > > > > themselves to be separately tracked through time."
>>
>> > > > > > > "The special theory of relativity forbids us to assume the
>> > > > > > > ether to
>> > > > > > > consist of particles observable through time, but the
>> > > > > > > hypothesis of
>> > > > > > > ether in itself is not in conflict with the special theory of
>> > > > > > > relativity. Only we must be on our guard against ascribing a
>> > > > > > > state of
>> > > > > > > motion to the ether."
>>
>> > > > > > > "But this ether may not be thought of as endowed with the
>> > > > > > > quality
>> > > > > > > characteristic of ponderable media, as consisting of parts
>> > > > > > > which may
>> > > > > > > be tracked through time. The idea of motion may not be
>> > > > > > > applied to it."
>>
>> > > > > > > Once you are willing to understand how Einstein defined
>> > > > > > > motion, as
>> > > > > > > particles which can be separately tracked through time, maybe
>> > > > > > > you can
>> > > > > > > advance from your statement.
>>
>> > > > > > > p.s. You still haven't answered how it is the train is length
>> > > > > > > contacted because it is moving relative to the aether and the
>> > > > > > > embankment is more at rest with respect to the embankment but
>> > > > > > > at the
>> > > > > > > same time LET has everything being relative. The answer is
>> > > > > > > both the
>> > > > > > > Observer at M and the Observer at M' will determine the train
>> > > > > > > to be
>> > > > > > > length contracted and for the clocks on the train to be
>> > > > > > > ticking slower
>> > > > > > > than the clocks on the embankment.
>>
>> > > > > > > > > This means the aether is more at rest with
>> > > > > > > > > respect to the embankment than it is with respect to the
>> > > > > > > > > train. The
>> > > > > > > > > train is moving relative to the aether so it will be
>> > > > > > > > > length contracted
>> > > > > > > > > while the embankment will not. The ruler the Observer on
>> > > > > > > > > the
>> > > > > > > > > embankment uses to measure the length of the train is not
>> > > > > > > > > length
>> > > > > > > > > contracted. The ruler the Observer on the train uses to
>> > > > > > > > > measure the
>> > > > > > > > > length of the embankment is length contracted. The
>> > > > > > > > > Observer on the
>> > > > > > > > > embankment and the Observer on the train conclude the
>> > > > > > > > > embankment is
>> > > > > > > > > longer than the train.
>>
>> > > > > > > > > The same holds true for the clocks on the train and on
>> > > > > > > > > the embankment.
>> > > > > > > > > Since the train is moving relative to the aether while
>> > > > > > > > > the embankment
>> > > > > > > > > is more at rest with respect to the aether there will be
>> > > > > > > > > a greater
>> > > > > > > > > pressure associated with the aether on the clock on the
>> > > > > > > > > train causing
>> > > > > > > > > it to tick slower. If the Observers on the embankment and
>> > > > > > > > > on the train
>> > > > > > > > > where able to 'see' each others clocks as the M and M'
>> > > > > > > > > pass each other
>> > > > > > > > > both the Observer on the train and the Observer on the
>> > > > > > > > > embankment
>> > > > > > > > > would conclude the clock on the train ticks slower than
>> > > > > > > > > the clock on
>> > > > > > > > > the embankment.
>>
>> > > > > > You know for a while you were making progress. (I'm sure some
>> > > > > > here
>> > > > > > are thinking the same about me ;) You managed to get away from
>> > > > > > each
>> > > > > > frame having its own ether to having them share a single ether
>> > > > > > (for EM
>> > > > > > waves anyway). Now if you could just get away from trying to
>> > > > > > attach
>> > > > > > one of the frames to the ether...
>>
>> > > > > > Did you ever get anywhere with that diagram I made to explain
>> > > > > > RoS to
>> > > > > > you. Einstein presented the train experiment from the point of
>> > > > > > view
>> > > > > > of the tracks, but he never said that the tracks were at rest
>> > > > > > WRT the
>> > > > > > ether.
>>
>> > > > > > - Hide quoted text -
>>
>> > > > > > > > > - Show quoted text -
>>
>> > > > > > > > According to both SR and LET there is no experiment that
>> > > > > > > > can reveal
>> > > > > > > > which frame is at rest WRT the ether, so there is no way to
>> > > > > > > > know which
>> > > > > > > > frame is more at rest WRT the ether.
>>
>> > > > > > > The clock which ticks the fastest is most at rest with
>> > > > > > > respect to the
>> > > > > > > aether.
>>
>> > > > > > But you have no way of knowing which clock is ticking faster.
>> > > > > > To
>> > > > > > measure the tick rate of a moving clock requires more than one
>> > > > > > clock
>> > > > > > at rest. And then you end up making assumptions to sychronize
>> > > > > > them.
>> > > > > > Those assumptions affect your measurements.
>>
>> > > > > The two clocks are synchronized at some point in time. Then the
>> > > > > clock
>> > > > > at M and the clock at M' travel past one another. The Observer on
>> > > > > the
>> > > > > train and the Observer on the embankment have enough time to
>> > > > > determine
>> > > > > which clock is ticking faster. The clock which is ticking faster
>> > > > > when
>> > > > > M and M pass each other is the clock most at rest with respect to
>> > > > > the
>> > > > > aether.- Hide quoted text -
>>
>> > > > > - Show quoted text -
>>
>> > > > You need at least one more clock to measure a tic rate. Given
>> > > > clock
>> > > > B, you compare the time on clock M to that on clock M' when they
>> > > > pass. You cannot compare them a second time because M' is moving.
>> > > > So
>> > > > you compare M' to B when they pass. With that comparison you can
>> > > > decide whether the clock at M' has gained or lost time, but that
>> > > > calculation assumes the clocks at M and B read the same. And
>> > > > assumptions were required when those clocks were synchronized.
>>
>> > > Why can't you measure the clocks at M and M' a second time?- Hide
>> > > quoted text -
>>
>> > > - Show quoted text -
>>
>> > M'----->
>> > M
>>
>> > M'----->
>> > M
>>
>> > If M' just went by M when do you think they are going to be facing
>> > each other a second time?
>>
>> T1:
>>
>> M'-------->
>> -\
>> --\
>> ---\
>> ----\
>> -----M
>>
>> T2:
>>
>> -----M'-------->
>> -----|
>> -----|
>> -----|
>> -----|
>> -----M
>>
>> T3:
>>
>> ----------M'-------->
>> ---------/
>> --------/
>> -------/
>> ------/
>> -----M
>>
>> There is no difference between the clocks being directly across from
>> each other and one clock approaching, and then being directly across
>> from, and then moving past the other clock.- Hide quoted text -
>>
>> - Show quoted text -
>
> If they are not directly across from each other you are making
> assumptions about the speed of light carrying the signal. If you use
> two clocks you made assumptions about the speed of light when you
> synchronized the two clocks.

Yeup. Namely that it takes the same time to travel the same distance.



From: Peter Webb on 13 Mar 2010 03:30

If they are not directly across from each other you are making
assumptions about the speed of light carrying the signal. If you use
two clocks you made assumptions about the speed of light when you
synchronized the two clocks.

_____________________________
When solving problems in SR or LET, you don't have to assume the speed of
light is constant. You know it is.




From: mpc755 on 13 Mar 2010 09:57
On Mar 13, 3:30 am, "Peter Webb"
<webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote:
> If they are not directly across from each other you are making
> assumptions about the speed of light carrying the signal.  If you use
> two clocks you made assumptions about the speed of light when you
> synchronized the two clocks.
>
> _____________________________
> When solving problems in SR or LET, you don't have to assume the speed of
> light is constant. You know it is.

Light waves propagate at 'c' with respect to the aether.
From: ben6993 on 13 Mar 2010 09:59
On Mar 12, 11:56 pm, "Inertial" <relativ...(a)rest.com> wrote:
> "ben6993" <ben6...(a)hotmail.com> wrote in message
>
> news:716c1760-a5db-4ce8-b116-7a739eaae397(a)o30g2000yqb.googlegroups.com...
>
>
>
>
>
> > On Mar 12, 6:16 pm, PD <thedraperfam...(a)gmail.com> wrote:
> >> On Mar 12, 12:00 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> >> > On 11 Mar, 20:57, PD <thedraperfam...(a)gmail.com> wrote:
>
> >> > > On Mar 11, 2:15 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> >> > > > On 11 Mar, 15:12, PD <thedraperfam...(a)gmail.com> wrote:
>
> >> > > > > On Mar 11, 6:43 am, Ste <ste_ro...(a)hotmail.com> wrote:
>
> >> > > > > > On 11 Mar, 01:51, "Peter Webb"
> >> > > > > > <webbfam...(a)DIESPAMDIEoptusnet.com.au>
> >> > > > > > wrote:
>
> >> > > > > > > No, perhaps you didn't understand. As I say, this is *not*
> >> > > > > > > the twins
> >> > > > > > > paradox, because in the twins paradox only *one* twin leaves
> >> > > > > > > Earth.
>
> >> > > > > > > ________________________
> >> > > > > > > Its functionally the same. It is exactly the twins paradox,
> >> > > > > > > but with two
> >> > > > > > > twins apparently doing exactly the same thing.
>
> >> > > > > > > Even if you cannot see that, the explanation on the Wikipedia
> >> > > > > > > page of the
> >> > > > > > > Twins Paradox is trivially adapted for two twins.
>
> >> > > > > > > I assume that you do not understand the Wikipedia twins
> >> > > > > > > paradox page, or
> >> > > > > > > else you would know the answers to your questions already.
> >> > > > > > > Which parts don't
> >> > > > > > > you understand?
>
> >> > > > > > Let's just go through it step by step Peter, as we have been
> >> > > > > > doing.
> >> > > > > > It's pointless spending 10 more postings arguing about how the
> >> > > > > > Wikipedia page does or does not answer the question, or how it
> >> > > > > > is or
> >> > > > > > is not relevant. As I've just said in a post to Inertial, the
> >> > > > > > only
> >> > > > > > analogy between my scenario and the twins paradox is that, in
> >> > > > > > my
> >> > > > > > scenario, both twins leave Earth, and both return the same age
> >> > > > > > as each
> >> > > > > > other - hence no paradox, and hence bearing no resemblance at
> >> > > > > > all to
> >> > > > > > the twins paradox.
>
> >> > > > > First of all, let's establish what you think is paradoxical at
> >> > > > > all
> >> > > > > about the description of the twins in the twin puzzle. Then let's
> >> > > > > see
> >> > > > > whether this paradox is present in the case you mention.
>
> >> > > > As I understand it, the supposed "paradox" in the twins paradox was
> >> > > > that one returned younger than the other. It was, of course, not a
> >> > > > paradox at all, but that's besides the point.
>
> >> > > No, then you do not understand the paradox, because there is nothing
> >> > > contradictory in that statement at all. It may be surprising, but
> >> > > it's
> >> > > not contradictory, not paradoxical. Disagreement of clocks is not a
> >> > > paradox.
>
> >> > > The paradox, which is what is perceived (normally) by freshmen when
> >> > > first introduced to this statement, is embodied in their immediate
> >> > > classroom question: "But in the frame of the traveling twin, it is
> >> > > the
> >> > > earth twin that is moving away and returning. Since this is symmetric
> >> > > to the case of the traveling twin moving away and returning, then
> >> > > shouldn't the traveling twin expect the earth twin to be younger when
> >> > > they meet again?" Now perhaps the paradox is more apparent to you.
>
> >> > > However, the puzzle is specifically designed to emphasize the danger
> >> > > of oversimplifying. In fact, the two twins are NOT symmetric, because
> >> > > one unambiguously experiences acceleration and the other
> >> > > unambiguously
> >> > > experiences no acceleration. This then leads to a discussion of what
> >> > > produces the asymmetry in the time.
>
> >> > I know Paul. I know.
>
> >> You can imagine my surprise, since what you said explicitly above was
> >> that the paradox was that the twins aged differently.
>
> >> > > Perhaps if you had started out by asking, "Since I don't see any
> >> > > obvious paradox here at all, perhaps someone could illuminate me as
> >> > > to
> >> > > why this is called the twin paradox?" Then at least you would have
> >> > > been on square one.
>
> >> > Really I just wanted to avoid going off on a long tangent about the
> >> > twins paradox. As I said, the scenario that were were addressing is
> >> > different from the twins paradox, in that we have three clocks, and
> >> > the two clocks with which we are now concerned (B and C) both return
> >> > to the origin point *synchronised* (albeit both lagging behind A),
> >> > whereas the twins' ages are not synchronised on the return of the
> >> > astronaut twin.
>
> >> Well, yes, it is a different result from the application of the same
> >> principle.
>
> >> If I calculate the angle that I can tip a TV tray before the coffee
> >> cup on it starts to slide, I find that I'm using the same principle
> >> (equilibrium of forces) that I would use to determine the tension in
> >> picture-hanger wire when mounting a photo on the wall.
>
> >> Different situation. Very same principle.
>
> >> Fine example of losing the forest for the trees. As you've done here.
>
> >> > So let me say again. The twins paradox would be applicable if we were
> >> > talking about A and B, or A and C. In the event, we are talking about
> >> > what B and C observe of each other from their own reference frames.
> >> > There is, therefore, no correspondence with the twins paradox, because
> >> > unlike the twins, B and C return synchronised with each other.- Hide
> >> > quoted text -
>
> >> - Show quoted text -- Hide quoted text -
>
> >> - Show quoted text -
>
> > I have written below a twin plank paradox of length.  I know the
> > explanation must really be very straightforward, but I don't see it
> > yet.  This is not a time paradox, but it looks to be a similar  issue.
>
> > A plank has four units of length (----) in its own frame and a garage
> > has two units of length (--) in its own frame.
> > There are two similar planks and garages in relative motion such that
> > plank P and garage G are moving fast towards the other plank p and
> > garage
>
> > g.  The relative speed is such that lengths are approximately halved
> > in relativistic contraction.
>
> >             <--- direction of motion
> > p  ----      G'  -
> > g  --        P'  --
>
> > Where ' sign indicates motion in the other twins' frame.
>
> > Here,  p does not fit within G', but P' fits approx. within g.
>
> > Looked at from the other frame, below, a similar result occurs:  p'
> > fits approx. within G, but P does not fit within g'.
> > ---->
> > p' --         G --
> > g' -          P ----
>
> > As the same two events are looked at twice, i.e. from two frameworks,
> > there are four outcomes in total.  The shed doors are destroyed in two
> > outcomes and the planks fit into the sheds in the other two outcomes.
> > So it looks like one of the two sheds is damaged and the other is
> > safe.  But that cannot be true as the motion is relative not absolute,
> > and the planks and garages are twins, and so the two outcomes should
> > be identical.
>
> They are identical if you do identical things .  If you do the 'close both
> garage doors simultaneously in the garage's rest frame of reference when the
> pole is fully within' for both garages, both are safe.
>
> If you close the door at different times in their frame, then they may not
> be safe (depending on when you do)- Hide quoted text -
>
> - Show quoted text -

Thanks very much for your help, Inertial.

I have introduced time into my calculations now and have relative
speed is approx. 0.866c; contraction is to half the length; and, time
slows to double for the moving plank and garage.

The time dilation for the moving garage enables the two planks to fit
through the garage doors in the appropriate, equivalent time
intervals.

I still need to work more on fitting the stationary plank within the
moving garage, but am resolving that by taking a break from physics
for a one week contract job! Physics paradoxes are very tiring!

From: Bruce Richmond on 13 Mar 2010 13:28
On Mar 13, 3:30 am, "Peter Webb"
<webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote:
> If they are not directly across from each other you are making
> assumptions about the speed of light carrying the signal.  If you use
> two clocks you made assumptions about the speed of light when you
> synchronized the two clocks.
>
> _____________________________
> When solving problems in SR or LET, you don't have to assume the speed of
> light is constant. You know it is.

In response to both you and Inertial, mpc755 wrote, "The clock which
ticks the fastest is most at rest with respect to the aether." So we
were not discussing SR. And since he thinks he can detect the ether
frame we are not discussing LET either.
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