What happens to SR if velocity of light is not constant?
Martin Korhorn
throughout the history of the universe, what will happen to space/time
dillitation,
E= mc^2/V(1-v^2/c^2) en E = mc^2? Of course it will become the
universe according to Moffat then, but i wondered if SR could be
redefined to hold under the variable speed of light assumption?
Greetings,
Martin.
Bill Hobba
Special Relativity applies to inertial reference frames. One property of
such frames is that they are homogeneous in time i.e. if an experiment is
conducted at a certain time then if the same experiment is conducted at
another time the same result will occur. If the speed of light is not
really constant then we are not dealing with an inertial frame so, strictly,
SR does not apply. However the fact that strictly inertial reference frames
do not exist in reality is hardly news - we know that already. Providing
the speed of light is not changing too quickly then, for all practical
purposes, we can still consider many frames of reference as inertial so SR
can be applied.
Bilge
What happens to SR if velocity of light is not constant? to usenet:
Sure. The `c' in the lorentz transforms need not refer to the speed of
light. If it doesn't, the photon has very small mass and charge is not
conserved. While this is not likely, it's more of a problem for maxwell's
equations than special relativity.
reticher
and being " a constant". Being "a constant" means that when measured locally it
has the same value even if its absolute value has changed. For the velocity of
light to be "a constant" between all velocity reference frames for exasmple,
all that is required is that the Lorentz Transformations for Length and Time be
reciprocal, which they are. For the velocity of light to be "constant" between
velocity reference frames, it is nercessary that the Lorentz Transformations fo
Length and Time be unchanged, which is not the case for reference frames having
a relative velocity. Physics has gone through some insane gyrations because
phyhsicists fail to make the distinction. The velocity of light, for example,
can be shown to decrease as elevation is lowered. See
http://www.members.aol.com/reticher1/gravs.htm
josX
> You are filing to distinguish the difference between an entity being
> "constant" and being " a constant". Being "a constant" means that
> when measured locally it has the same value even if its absolute value
> has changed. For the velocity of light to be "a constant" between all
> velocity reference frames for exasmple, all that is required is that
> the Lorentz Transformations for Length and Time be reciprocal, which
> they are.
?
"For the velocity of light to be a constant...all that is required is...
the Lorentz Transformations ..." ?
Do you mind telling me how this is supposed to work?
--
jos
Etherman
"Martin Korhorn" <Martin...@cs.com> wrote in message
news:cf11ef8d.02081...@posting.google.com...
The two postulates would remain unchanged. The laws of physics would still
be the same in all inertial reference frames and the speed of light would
be independent of the relative velocity of the source and observer. There
would be some differences though. The velocity addition law would change,
for example.
--
Etherman
AA # pi
EAC Director of Ritual Satanic Abuse Operations
AMTCode(v2): [Poster][TÆ][A5][Lx][Sx][Bx][FD][P-][CC]
Bill Hobba
> Sure. The `c' in the lorentz transforms need not refer to the speed of
> light. If it doesn't, the photon has very small mass and charge is not
> conserved. While this is not likely, it's more of a problem for maxwell's
> equations than special relativity.
Another possibility I did not consider. I think such changes may have
something to do with cosmological effect. My undemanding is that some
models predict larger velocities of light during the big bang. This may
just be a 'left over' so to speak of that. Either way I think SR and GR are
pretty safe.
Thanks
Bill
David Evens
You might try reading the bits that you neither quoted nor read.
josX
You SRists (you are an SRist aren't you?) might want to try something
else then endless evasions.
--
jos
Robert J. Kolker
josX wrote:
>
> You SRists (you are an SRist aren't you?) might want to try something
> else then endless evasions.
What evasion? SR and Quantum Theory are tested and re-tested thousands
of times a day.
Bob Kolker
Eugene Shubert
with a variable speed of light?
I'm intrigued by this mathematical question and will work on it when I get
some free time.
Eugene Shubert
http://www.everythingimportant.org
F. Kuik
Bill Hobba <bho...@bigpond.net.au> schreef in berichtnieuws
4aD79.4805$7V6....@news-server.bigpond.net.au...
Ofcourse they will be safe now.... but if it's really true that the speed of
light is changing, might it not be possible this changing would speed up
over time?
When you would make a long high speed space flight I think SR would have to
be modified cause the speed of light has an other value at the beginning of
the trip than at the end of the trip right?
Thanks
Floris
dlzc@aol.com (formerly)
> Ofcourse they will be safe now.... but if it's really true that the speed
of
> light is changing, might it not be possible this changing would speed up
> over time?
It is not so much that c is changing over time, but the Universe may be
"speeding up" around it. Light from distant/ancient objects would be red
shifted... without the need for velocities approaching c. However, the
standard unit of length is now (since 1983) defined in terms of c * time, so
a change in c will never be observed directly.
> When you would make a long high speed space flight I think SR would have
to
> be modified cause the speed of light has an other value at the beginning
of
> the trip than at the end of the trip right?
If you make a flight over a distance of 1,000 light years travelling at
0.5c, the value of c may have changed by 1 part in 10^7. Since your meter
will have changed also, what would it matter?
SR is a little like pulling an inventory in a company. Everything "real"
has to stop while these specific measures are applied, and they apply for
that "instant". Not to discount the effort required for either tool, nor
the validity of the results. "Real" being defined as gravity and secular
time for SR, and receipts&shipments-of-product and work-in-progress for an
inventory.
David A. Smith
William Bliss
[...]
> "For the velocity of light to be a constant...all that is required is...
> the Lorentz Transformations ..." ?
>
> Do you mind telling me how this is supposed to work?
The LT is composed of three simple conceptual ideas.
If you learn what they are and how to apply them correctly
you will get your answer.
If you show me you understand these three ideas then
I might be willing to show you how they are applied,
but I'm disinclined due to your demonstrated
unwillingness to work step-by-step with the basics.
Jos, you will need to thoroughly understand SR before
you will ever be able to disprove it.
Wm
josX
>"josX" <jo...@mraha.kitenet.net> wrote
>[...]
>> "For the velocity of light to be a constant...all that is required is...
>> the Lorentz Transformations ..." ?
>>
>> Do you mind telling me how this is supposed to work?
>
>The LT is composed of three simple conceptual ideas.
>If you learn what they are and how to apply them correctly
>you will get your answer.
I'm always ready to learn, let me guess:
timedilation, lengthcontraction and the voodoo factor? No? i give up,
please tell me.
>If you show me you understand these three ideas then
>I might be willing to show you how they are applied,
>but I'm disinclined due to your demonstrated
>unwillingness to work step-by-step with the basics.
I even read Einstein's book directly, so don't give me that.
>Jos, you will need to thoroughly understand SR before
>you will ever be able to disprove it.
"thoroughly" as in the loop:
[new to SR]
|
V
<agrees with SR>---no--->[doesn't understand it]
| ^ |
| | |
| | <feed more books/material>
| | |
yes +--------------------+
|
|
V
[has basic understanding]
--
jos
William Bliss
news:ajopt9$m9s$1...@news1.xs4all.nl...
> William Bliss wrote:
> >"josX" <jo...@mraha.kitenet.net> wrote
> >[...]
> >> "For the velocity of light to be a constant...all that is required
is...
> >> the Lorentz Transformations ..." ?
> >>
> >> Do you mind telling me how this is supposed to work?
> >
> >The LT is composed of three simple conceptual ideas.
> >If you learn what they are and how to apply them correctly
> >you will get your answer.
>
> I'm always ready to learn, let me guess:
> timedilation, lengthcontraction and the voodoo factor? No? i give up,
> please tell me.
From the assumption of time dilation we can derive the necessary
correcting term (vx/cc) found in the LT. A simple situation can
show why we need this term.
An observer standing along the train tracks sees the train's
conductor walking slowly forward from car to car while setting
each car's wall clock from his pocket watch. This observer will
measure the conductor's speed as slightly faster than the train
and thusly his pocket watch will be running slightly slower than
the car's wall clocks. The net result is that, from the observer's
pov, the train's wall clocks won't agree with each other but will
show a "time-gradient", often called Esync in this ng. The same
thing will happen if the conductor starts at the first car and
walks backwards. Now his pocket watch will appear to be running
slightly faster than the wall clocks. The actual point here, is
that no matter how the people or machines on the train attempt to
synchronize their clocks there will always be this linear error
in the direction of motion.
If we use Einstein's velocity composition rule we can easily
derive the value of this "time-gradient" to be gamma*v*x/cc.
This all important LT term is the cause of the infamous simultaneity
"problems" in SR. It is why the x' line in a Minkowski diagram
is drawn sloping upwards.
Wm
josX
>"josX" <jo...@mraha.kitenet.net> wrote in message
>news:ajopt9$m9s$1...@news1.xs4all.nl...
>>William Bliss wrote:
>>>"josX" <jo...@mraha.kitenet.net> wrote
>>>[...]
>>>> "For the velocity of light to be a constant...all that is required is...
>>>> the Lorentz Transformations ..." ?
>>>>
>>>> Do you mind telling me how this is supposed to work?
>>>
>>>The LT is composed of three simple conceptual ideas.
>>>If you learn what they are and how to apply them correctly
>>>you will get your answer.
>>
>>I'm always ready to learn, let me guess:
>>timedilation, lengthcontraction and the voodoo factor? No? i give up,
>>please tell me.
>
>From the assumption of time dilation we can derive the necessary
>correcting term (vx/cc) found in the LT. A simple situation can
>show why we need this term.
'correction term' ?
>An observer standing along the train tracks sees the train's
>conductor walking slowly forward from car to car while setting
>each car's wall clock from his pocket watch. This observer will
>measure the conductor's speed as slightly faster than the train
>and thusly his pocket watch will be running slightly slower than
>the car's wall clocks.
...and slower then his own watch, in contradiction with what the
conductor computes, which is that the watch of the man on the tracks
is running slow...
> The net result is that, from the observer's
>pov, the train's wall clocks won't agree with each other but will
>show a "time-gradient", often called Esync in this ng.
I smell a paradox in the making. The conductor's pov is that the clocks
are moving, thus the clocks on the wall are running slow while he's
moving from clock to clock. That results in an Esync that has clocks
he reaches later run ahead of clocks he has adjusted earlier, the
earlier clocks run more behind (every time the conducter moves, the
wallclocks are timedilated).
But the pov of the wall clocks is that the conducters watch is running
slow when he moves, therefore clocks that he reaches later will be
running more behind then clocks he reached early (every time the
conductor moves his watch is timedilated).
> The same
>thing will happen if the conductor starts at the first car and
>walks backwards. Now his pocket watch will appear to be running
>slightly faster than the wall clocks.
Why is that, from which pov.
> The actual point here, is
>that no matter how the people or machines on the train attempt to
>synchronize their clocks there will always be this linear error
>in the direction of motion.
Actually, there is a paradox if you look a little further.
>If we use Einstein's velocity composition rule we can easily
>derive the value of this "time-gradient" to be gamma*v*x/cc.
>This all important LT term is the cause of the infamous simultaneity
>"problems" in SR. It is why the x' line in a Minkowski diagram
>is drawn sloping upwards.
No, it's just another paradox disproving SR, sorry to burst the bubble.
--
jos
Bill Hobba
"Eugene Shubert" <eug...@everythingimportant.org> wrote in message
news:3d5f...@sys13.hou.wt.net...
> What would be the modified Lorentz Transformation equations in a universe
> with a variable speed of light?
>
> I'm intrigued by this mathematical question and will work on it when I get
> some free time.
>
It might be a bit hard Eugine. Remember the principle of SR on which these
transformations are based implies time is homogeneous in an inertial
coordinate system. Shine a torch an a certain time and measure the speed of
light. This principle implies (the same experiment conducted at a different
time will give the same results) that if you shine a torch at a different
time you would measure the same speed. A variable light speed would seem
inconsistent with inertial frames of reference. However what you come up
with might be interesting.
Thanks
Bill
William Bliss
You're starting to catch on. The conductor does in deed see the
train station contracted, its clocks running slow and the wall
clocks along the station house displaying a synchronization gradient.
The LT works both ways, but there isn't any "contradiction", just
mutual observations.
>
> > The net result is that, from the observer's
> >pov, the train's wall clocks won't agree with each other but will
> >show a "time-gradient", often called Esync in this ng.
>
> I smell a paradox in the making. The conductor's pov is that the clocks
> are moving, thus the clocks on the wall are running slow while he's
> moving from clock to clock.
This is true too. But the effect is rather small as his relative
speed is only a few kph.
> That results in an Esync that has clocks
> he reaches later run ahead of clocks he has adjusted earlier, the
> earlier clocks run more behind (every time the conducter moves, the
> wallclocks are timedilated).
These are second order effects that do change when the conductor
rechecks the clocks by moving backwards. The actual derivation
of time-gradient uses a very slow walking conductor. :)
>
> But the pov of the wall clocks is that the conducters watch is running
> slow when he moves, therefore clocks that he reaches later will be
> running more behind then clocks he reached early (every time the
> conductor moves his watch is timedilated).
Like the twin "paradox", the elapsed time depends on acceleration
history.
>
> > The same
> >thing will happen if the conductor starts at the first car and
> >walks backwards. Now his pocket watch will appear to be running
> >slightly faster than the wall clocks.
>
> Why is that, from which pov.
From the stationary observer's pov. The conductor's total speed
is slower when he walks toward the train's caboose.
> > The actual point here, is
> >that no matter how the people or machines on the train attempt to
> >synchronize their clocks there will always be this linear error
> >in the direction of motion.
>
> Actually, there is a paradox if you look a little further.
Nope! No paradox! When you attempt to spell it out for me you
may discover that SR works quite well.
>
> >If we use Einstein's velocity composition rule we can easily
> >derive the value of this "time-gradient" to be gamma*v*x/cc.
> >This all important LT term is the cause of the infamous simultaneity
> >"problems" in SR. It is why the x' line in a Minkowski diagram
> >is drawn sloping upwards.
>
> No, it's just another paradox disproving SR, sorry to burst the bubble.
Your illusion of paradoxes will go away as you learn to work
with SR math correctly. Now that you know the third idea inherent
in the LT you should have an easier time of it.
Wm
David Evens
You mindless idiots (you are a mindless idiot aren't you?) might want
to try learning something instead of making bizarre gramatical errors.
josX
You too :) ?
> The conductor does in deed see the
>train station contracted, its clocks running slow and the wall
>clocks along the station house displaying a synchronization gradient.
>The LT works both ways, but there isn't any "contradiction", just
>mutual observations.
Is SR about visual illusions?
No it isn't, they work differently.
It is about real clocks and real length, but an object can only
have one length, not multiple. Hence all the paradoxes that are
invented to bring this to the attention of the SRists.
>>> The net result is that, from the observer's
>>>pov, the train's wall clocks won't agree with each other but will
>>>show a "time-gradient", often called Esync in this ng.
>>
>>I smell a paradox in the making. The conductor's pov is that the clocks
>>are moving, thus the clocks on the wall are running slow while he's
>>moving from clock to clock.
>
>This is true too. But the effect is rather small as his relative
>speed is only a few kph.
Does that disproof the qualitative problem ?
>> That results in an Esync that has clocks
>> he reaches later run ahead of clocks he has adjusted earlier, the
>> earlier clocks run more behind (every time the conducter moves, the
>> wallclocks are timedilated).
>
>These are second order effects that do change when the conductor
>rechecks the clocks by moving backwards. The actual derivation
>of time-gradient uses a very slow walking conductor. :)
Doesn't help in principle.
Here is Einsteins FUNDAMENTAL mistake: he failed to realize that you can
have visual illusions, but that reality exists and is computable independant
of any direct observations, and this works very nicely.
Do i need to construct a spaceship for you in thought that has this
timegradient produce yet another totally impossible paradox ?
Think about a ship that has behind every clock a long iron rod, leading
to a device. When a clock reaches the full hour it gives a pulse to
the device. The clocks are numbered 1 to 10. Do you see the paradox ?
>> But the pov of the wall clocks is that the conducters watch is running
>> slow when he moves, therefore clocks that he reaches later will be
>> running more behind then clocks he reached early (every time the
>> conductor moves his watch is timedilated).
>
>Like the twin "paradox", the elapsed time depends on acceleration
>history.
Then you have chosen a preferred frame, it's the frame that "didn't
accelerate".
You have also defined an absolute frame: the frame that never accelerated
in the history of the universe.
Do you realize this flies directly against the face of the principle of
relativity ? (probbaly not so i tell you: it does fly directly in the
face of the principle of relativity). :-)
>>> The same
>>>thing will happen if the conductor starts at the first car and
>>>walks backwards. Now his pocket watch will appear to be running
>>>slightly faster than the wall clocks.
>>
>> Why is that, from which pov.
>
>From the stationary observer's pov. The conductor's total speed
>is slower when he walks toward the train's caboose.
Do you spend much work on trying to find little snippits and examples
that seemingly work out under SR ?
>>> The actual point here, is
>>>that no matter how the people or machines on the train attempt to
>>>synchronize their clocks there will always be this linear error
>>>in the direction of motion.
Nonsense. That is only from the stationary coordinate system. The trains
coordinate system says it depends upon conductor direction, and so
does the conductors coordinate system, and these two are in contradiction
as well (oposite direction of gradient).
>> Actually, there is a paradox if you look a little further.
>
>Nope! No paradox! When you attempt to spell it out for me you
>may discover that SR works quite well.
I think i found even more then 1 paradox here.
>> >If we use Einstein's velocity composition rule we can easily
>> >derive the value of this "time-gradient" to be gamma*v*x/cc.
>> >This all important LT term is the cause of the infamous simultaneity
>> >"problems" in SR. It is why the x' line in a Minkowski diagram
>> >is drawn sloping upwards.
>>
>> No, it's just another paradox disproving SR, sorry to burst the bubble.
>
>Your illusion of paradoxes will go away as you learn to work
>with SR math correctly. Now that you know the third idea inherent
>in the LT you should have an easier time of it.
+ +
|\________________________________________________________/|
|____________________________O_____________________________|
tube filled with liquid Clock
Sorry, i invented the measuring device which uses only 1 clock.
Tell me how your timegradient helps you when this device is placed
on the moon, and the speed of light is measured in both directions
while a spaceship is traveling past it along the length of the measuring
device.
--
jos
William Bliss
> William Bliss wrote:
[...]
> > The conductor does in deed see the
> >train station contracted, its clocks running slow and the wall
> >clocks along the station house displaying a synchronization gradient.
> >The LT works both ways, but there isn't any "contradiction", just
> >mutual observations.
>
> Is SR about visual illusions?
> No it isn't, they work differently.
> It is about real clocks and real length,
That is correct.
> but an object can only have one length, not multiple.
That is also correct.
> Hence all the paradoxes that are
> invented to bring this to the attention of the SRists.
You are confusing "illusions" with mismeasurments. SR works
because all observers are forced into the conclusion that all
other moving observers are, in essence, mismeasuring things.
Each observer believes himself to be "stationary" and sees
that the moving observers are shrunk, dilated and using badly
synchronized clocks. It is for these three reasons that the
moving observer is seen to measure light's speed as c.
>
> >>> The net result is that, from the observer's
> >>>pov, the train's wall clocks won't agree with each other but will
> >>>show a "time-gradient", often called Esync in this ng.
> >>
> >>I smell a paradox in the making. The conductor's pov is that the clocks
> >>are moving, thus the clocks on the wall are running slow while he's
> >>moving from clock to clock.
> >
> >This is true too. But the effect is rather small as his relative
> >speed is only a few kph.
>
> Does that disproof the qualitative problem ?
No, it just makes it much harder to derive the time-gradient.
The fast walking conductor would notice the discrepancy and see
the need to walk the train's length a couple more times to correct
for his varying pocket watch. The final result would be the same.
>
> >> That results in an Esync that has clocks
> >> he reaches later run ahead of clocks he has adjusted earlier, the
> >> earlier clocks run more behind (every time the conducter moves, the
> >> wallclocks are timedilated).
> >
> >These are second order effects that do change when the conductor
> >rechecks the clocks by moving backwards. The actual derivation
> >of time-gradient uses a very slow walking conductor. :)
>
> Doesn't help in principle.
>
> Here is Einsteins FUNDAMENTAL mistake: he failed to realize that you can
> have visual illusions, but that reality exists and is computable
independant
> of any direct observations, and this works very nicely.
Jos, Einstein (and any possible mistakes he might have made)
doesn't interest me. My interest is in modern SR/GR and mistakes
(or oversights) that currently living theorists might be making.
> Do i need to construct a spaceship for you in thought that has this
> timegradient produce yet another totally impossible paradox ?
Yes! You will absolutely need to solve problems like this before
it will become clear how it all works. (I even did one for you at bottom)
>
> Think about a ship that has behind every clock a long iron rod, leading
> to a device. When a clock reaches the full hour it gives a pulse to
> the device. The clocks are numbered 1 to 10. Do you see the paradox ?
Nope! Probably because I don't understand your problem.
>
> >> But the pov of the wall clocks is that the conducters watch is running
> >> slow when he moves, therefore clocks that he reaches later will be
> >> running more behind then clocks he reached early (every time the
> >> conductor moves his watch is timedilated).
> >
> >Like the twin "paradox", the elapsed time depends on acceleration
> >history.
>
> Then you have chosen a preferred frame, it's the frame that "didn't
> accelerate".
I'm only interested in one "preferred" frame, namely, my frame.
From my frame I can see that equipment in other inertial frames will
always measure the speed of light to be c. It's simple geometry.
>
> You have also defined an absolute frame: the frame that never accelerated
> in the history of the universe.
>
> Do you realize this flies directly against the face of the principle of
> relativity ? (probbaly not so i tell you: it does fly directly in the
> face of the principle of relativity). :-)
Millions of amateur and professional scientists have looked for
violations of the principle of relativity for hundreds of years
and nobody has yet published such a discrepancy. This is why I seriously
doubt that *you* will be able to "tell" me about such a violation.
>
> >>> The same
> >>>thing will happen if the conductor starts at the first car and
> >>>walks backwards. Now his pocket watch will appear to be running
> >>>slightly faster than the wall clocks.
> >>
> >> Why is that, from which pov.
> >
> >From the stationary observer's pov. The conductor's total speed
> >is slower when he walks toward the train's caboose.
>
> Do you spend much work on trying to find little snippits and examples
> that seemingly work out under SR ?
Nope! I "spend much work on trying to find little snippits and
examples that seemingly work out under" *GR*.
>
> >>> The actual point here, is
> >>>that no matter how the people or machines on the train attempt to
> >>>synchronize their clocks there will always be this linear error
> >>>in the direction of motion.
>
> Nonsense. That is only from the stationary coordinate system. The trains
> coordinate system says it depends upon conductor direction, and so
> does the conductors coordinate system, and these two are in contradiction
> as well (oposite direction of gradient).
I repeat. No matter how the train occupants synchronize their
clocks a moving observer will see a time-gradient. In another
post (to dseppala) I even outlined a pool table camera metaphore
that can be instrumental in understanding this principle.
> >> Actually, there is a paradox if you look a little further.
> >
> >Nope! No paradox! When you attempt to spell it out for me you
> >may discover that SR works quite well.
>
> I think i found even more then 1 paradox here.
Fine. Spell them out.
> >> >If we use Einstein's velocity composition rule we can easily
> >> >derive the value of this "time-gradient" to be gamma*v*x/cc.
> >> >This all important LT term is the cause of the infamous simultaneity
> >> >"problems" in SR. It is why the x' line in a Minkowski diagram
> >> >is drawn sloping upwards.
> >>
> >> No, it's just another paradox disproving SR, sorry to burst the bubble.
> >
> >Your illusion of paradoxes will go away as you learn to work
> >with SR math correctly. Now that you know the third idea inherent
> >in the LT you should have an easier time of it.
>
> + +
> |\________________________________________________________/|
> |____________________________O_____________________________|
> tube filled with liquid Clock
>
> Sorry, i invented the measuring device which uses only 1 clock.
>
> Tell me how your timegradient helps you when this device is placed
> on the moon, and the speed of light is measured in both directions
> while a spaceship is traveling past it along the length of the measuring
> device.
One thing at a time. The proof only needs to show what one observer
will see when observing one moving experiment. If the proof is general
enough it will apply to the other situations in turn.
In this situation the stationary observer (O) needs to see not only
the photons being measured but also the signal traveling from your
detectors to the central clock. Let's say this signal is also light.
Now, because the device is moving, to the right let's say, it will
be shorter and the clock will be running slower. The time-gradient
comes into play in that the signal from the left detector will take
longer to travel to the center clock than the signal from the right
detector (as seen by O). The clock's measurement of time passage
between detections will be L/c. But O will measure this time as being
much shorter L/(gamma*(c + v)).
Here's how O sees it. Capital "T"s will show his timings.
1) The light triggers the right side detector at time T0 which emits a
signal.
2) This left moving signal takes time T1 = L/(2*gamma*(c + v)) to reach
the clock. Notice that the original light and this signal have traveled
side by side from the detector to the clock.
3) The clock detects the signal from the right and calls it t0 = 0.
4) The light takes time T2 = L/(gamma*(c + v)) to travel the length L.
5) The light triggers the left detector which emits a light signal.
6) The right moving light signal from the left detector takes time
T3 = L/(2*gamma*(c - v)) to reach the clock.
7) The clock detects the second signal at time t1 = L/c.
Observer O only needs to sum T2/2 + T3 in order to calculate the
difference in time between the clock seeing the two signals.
Here it is.
T(total) = L/(gamma*(c + v))/2 + L/(2*gamma*(c - v)).
This simplifies to (L/[2gamma])*(2c/[c^2-v^2]) = gamma*L/c.
Finally! Because the clock is running slow by a factor of gamma. It
will display an elapsed time of L/c just as one might predict.
Be careful Jos. If you repudiate the above solution to your own problem
then absolutely everyone will believe you are a complete nut case.
Review:
All three LT ideas come into play, (length contraction, time dilation,
and time-gradient). The time-gradient, in this case, was masked by the
simple fact that the signal from the left detector took so much longer
to get to the clock than the signal from the right hand detector. This
is the same effect that causes an array of clocks to be unsynchronized.
Homework:
Do this again, but use Fizeau's twin-spinning-disks to measure light's
speed. (hint: it should work with light in both directions)
Wm
josX
>"josX" <jo...@mraha.kitenet.net> wrote in message
>news:ajr359$2b9$7...@news1.xs4all.nl...
>> William Bliss wrote:
>[...]
>>> The conductor does in deed see the
>>>train station contracted, its clocks running slow and the wall
>>>clocks along the station house displaying a synchronization gradient.
>>>The LT works both ways, but there isn't any "contradiction", just
>>>mutual observations.
>>
>>Is SR about visual illusions?
>>No it isn't, they work differently.
>>It is about real clocks and real length,
>
>That is correct.
>
>> but an object can only have one length, not multiple.
>
>That is also correct.
>
>> Hence all the paradoxes that are
>> invented to bring this to the attention of the SRists.
>
>You are confusing "illusions" with mismeasurments.
mismeasurements...
So how do you pseudoresolve this paradox:
a lead plate travels to the moon when the moon is half
a lead rectangle travels away from the sun such that the cube
and the rectangle will collide
The plate at rest is 1x1meter, the rectangle at rest is 1.001 meter
high and 1.001 meter wide (the gap, the surrounding lead is a bit bigger).
They both travel with their flat survaces pointing in the direction of
travel (like windscreens, but straight up). They are both very thin.
Now, the rectangle will measure the plate by bumbing into it and seeing
it the plate slides through or not.
According to the plate: the rectangle is lengthcontracted, therefore
they will collide.
According to the rectangle, the plate is lengthcontracted, therefore
the plate will slide through the rectangle.
Paradox, theory=useless/worthless.
> SR works
>because all observers are forced into the conclusion that all
>other moving observers are, in essence, mismeasuring things.
>
>Each observer believes himself to be "stationary" and sees
>that the moving observers are shrunk, dilated and using badly
>synchronized clocks. It is for these three reasons that the
>moving observer is seen to measure light's speed as c.
Now you say "see" again, suggesting visual illusions. You are startking
to become fuzzy.
That mistake and oversight is taking Einsteins nonsense seriously.
Then again, it's their ticket to a nice salary...
>> Do i need to construct a spaceship for you in thought that has this
>> timegradient produce yet another totally impossible paradox ?
>
>Yes! You will absolutely need to solve problems like this before
>it will become clear how it all works. (I even did one for you at bottom)
>
>> Think about a ship that has behind every clock a long iron rod, leading
>> to a device. When a clock reaches the full hour it gives a pulse to
>> the device. The clocks are numbered 1 to 10. Do you see the paradox ?
>
>Nope! Probably because I don't understand your problem.
There can be no time-gradient if all clocks communicate using sound and
synchronize at a central location at equal sound-distance. (You actually
have to think here, mere fantasy doesn't cut it).
>>>> But the pov of the wall clocks is that the conducters watch is running
>>>> slow when he moves, therefore clocks that he reaches later will be
>>>> running more behind then clocks he reached early (every time the
>>>> conductor moves his watch is timedilated).
>>>
>>>Like the twin "paradox", the elapsed time depends on acceleration
>>>history.
>>
>>Then you have chosen a preferred frame, it's the frame that "didn't
>>accelerate".
>
>I'm only interested in one "preferred" frame, namely, my frame.
>From my frame I can see that equipment in other inertial frames will
>always measure the speed of light to be c. It's simple geometry.
Then what if 'you' are the moving twin.
>> You have also defined an absolute frame: the frame that never accelerated
>> in the history of the universe.
>>
>> Do you realize this flies directly against the face of the principle of
>> relativity ? (probbaly not so i tell you: it does fly directly in the
>> face of the principle of relativity). :-)
>
>Millions of amateur and professional scientists have looked for
>violations of the principle of relativity for hundreds of years
>and nobody has yet published such a discrepancy. This is why I seriously
>doubt that *you* will be able to "tell" me about such a violation.
So you subscribe to the Aristotelian idea that that is true which is voted
true (that was Aristotle IIRC).
>>>>> The same
>>>>>thing will happen if the conductor starts at the first car and
>>>>>walks backwards. Now his pocket watch will appear to be running
>>>>>slightly faster than the wall clocks.
>>>>
>>>> Why is that, from which pov.
>>>
>>>From the stationary observer's pov. The conductor's total speed
>>>is slower when he walks toward the train's caboose.
>>
>>Do you spend much work on trying to find little snippits and examples
>>that seemingly work out under SR ?
>
>Nope! I "spend much work on trying to find little snippits and
>examples that seemingly work out under" *GR*.
>>
>> >>> The actual point here, is
>> >>>that no matter how the people or machines on the train attempt to
>> >>>synchronize their clocks there will always be this linear error
>> >>>in the direction of motion.
>>
>> Nonsense. That is only from the stationary coordinate system. The trains
>> coordinate system says it depends upon conductor direction, and so
>> does the conductors coordinate system, and these two are in contradiction
>> as well (oposite direction of gradient).
>
>I repeat. No matter how the train occupants synchronize their
>clocks a moving observer will see a time-gradient.
Now you talk about "see" again, visual illusions after all?
Or just a fuzzy mix of "visual illusions" where that takes care of an
argument, and "real length/time" where that is applicable.
There *is* or there *isn't* a timegradient, and i have the liquid filled
tube to force you to commit to one world situation.
> In another
>post (to dseppala) I even outlined a pool table camera metaphore
>that can be instrumental in understanding this principle.
>
>>>> Actually, there is a paradox if you look a little further.
>>>
>>>Nope! No paradox! When you attempt to spell it out for me you
>>>may discover that SR works quite well.
>>
>>I think i found even more then 1 paradox here.
>
>Fine. Spell them out.
I already did.
For instance: wall clocks predict a different time-gradient then
the conductor.
>>>>>If we use Einstein's velocity composition rule we can easily
>>>>>derive the value of this "time-gradient" to be gamma*v*x/cc.
>>>>>This all important LT term is the cause of the infamous simultaneity
>>>>>"problems" in SR. It is why the x' line in a Minkowski diagram
>>>>>is drawn sloping upwards.
>>>>
>>>>No, it's just another paradox disproving SR, sorry to burst the bubble.
>>>
>>>Your illusion of paradoxes will go away as you learn to work
>>>with SR math correctly. Now that you know the third idea inherent
>>>in the LT you should have an easier time of it.
>>
>>+ +
>>|\________________________________________________________/|
>>|____________________________O_____________________________|
>> tube filled with liquid Clock
>>
>>Sorry, i invented the measuring device which uses only 1 clock.
>>
>>Tell me how your timegradient helps you when this device is placed
>>on the moon, and the speed of light is measured in both directions
>>while a spaceship is traveling past it along the length of the measuring
>>device.
>
>One thing at a time. The proof only needs to show what one observer
>will see when observing one moving experiment. If the proof is general
>enough it will apply to the other situations in turn.
>
>In this situation the stationary observer (O) needs to see not only
>the photons being measured but also the signal traveling from your
>detectors to the central clock.
Huh?
Addition of fuzzpoints noticed.
He doesn't need to see the soundsignal travel to him, in fact he can't
see it. Can you see sound in the distance in a tube ?
> Let's say this signal is also light.
Alright, you are starting to piss me off.
>Now, because the device is moving, to the right let's say, it will
>be shorter and the clock will be running slower. The time-gradient
>comes into play in that the signal from the left detector will take
>longer to travel to the center clock than the signal from the right
>detector (as seen by O). The clock's measurement of time passage
>between detections will be L/c. But O will measure this time as being
>much shorter L/(gamma*(c + v)).
It is absolutely amazing how brainwashing works. I actually think you
mean what you say....
The signal is SOUND dude, it's not LIGHT. The signals from both detectors
take equal times.
>Here's how O sees it. Capital "T"s will show his timings.
>1) The light triggers the right side detector at time T0 which emits a
>signal.
He doesn't necesarily see this at all. If he did it has nothing to do with
the outcome.
>2) This left moving signal takes time T1 = L/(2*gamma*(c + v)) to reach
>the clock. Notice that the original light and this signal have traveled
>side by side from the detector to the clock.
You took the sting out by substituting a light-signal instead of a sound
signal. I think you realize by now you are a liar don't you.
>3) The clock detects the signal from the right and calls it t0 = 0.
>4) The light takes time T2 = L/(gamma*(c + v)) to travel the length L.
>5) The light triggers the left detector which emits a light signal.
>6) The right moving light signal from the left detector takes time
>T3 = L/(2*gamma*(c - v)) to reach the clock.
>7) The clock detects the second signal at time t1 = L/c.
>
>Observer O only needs to sum T2/2 + T3 in order to calculate the
>difference in time between the clock seeing the two signals.
>Here it is.
>
> T(total) = L/(gamma*(c + v))/2 + L/(2*gamma*(c - v)).
>
>This simplifies to (L/[2gamma])*(2c/[c^2-v^2]) = gamma*L/c.
>
>Finally! Because the clock is running slow by a factor of gamma. It
>will display an elapsed time of L/c just as one might predict.
>
>Be careful Jos. If you repudiate the above solution to your own problem
>then absolutely everyone will believe you are a complete nut case.
You are a liar.
>Review:
>All three LT ideas come into play, (length contraction, time dilation,
>and time-gradient). The time-gradient, in this case, was masked by the
>simple fact that the signal from the left detector took so much longer
>to get to the clock than the signal from the right hand detector. This
>is the same effect that causes an array of clocks to be unsynchronized.
It was a sound-signal, not a light-signal. The soundsignal has a speed
defined relative to the liquid and the tube always, both signals from
both detectors take exactly the same amount of time, in all frames.
>Homework:
>Do this again, but use Fizeau's twin-spinning-disks to measure light's
>speed. (hint: it should work with light in both directions)
Homework:
Look again and don't take the sting out.
--
jos
William Bliss
I'm saddened to see that you don't wish to work with me to
solve even your own experimental setup. Until now, you hadn't
mentioned the requirement of using sound to collect the timing
information.
Why on earth would you want to use sound to measure the speed of
light. Even the slightest change in temperature and/or pressure
would greatly effect the measurement. But most importantly, the
period of any reasonable sound wave is going to be longer than
the transit time of the light beam. As you know, it is very
difficult to find the exact peak of a wave, as it is rather flat
up there. Long waves make this problem even worse. This is why
timing experts use high frequency modulated pulses. Of course,
using light (or electric) signals allows us to use much higher
frequencies.
Let me know if you don't agree, but I would think that splitting
the actual light beam in two, and having one beam proceed to the
clock while the other travels the length of the device would give
us a good experiment. In fact, we could put *both* light detectors
at the clock if we wished, by simply replacing the second detector
by a mirror.
The Fizeau (spinning disks) method for measuring the speed of light
is even simpler to work with as the light either does or doesn't
get through both holes. All one needs to do is measure the rpm of
the disks. :)
Wm
"josX" <jo...@mraha.kitenet.net> wrote in message
news:ajt0l1$787$1...@news1.xs4all.nl...
josX
>Jos,
>
>I'm saddened to see that you don't wish to work with me to
>solve even your own experimental setup. Until now, you hadn't
>mentioned the requirement of using sound to collect the timing
>information.
I have mentioned that setup before in other threads, we hadn't specified
it in ours perhaps, but we also hadn't specified we wouldn't do it like
that, with sound.
>Why on earth would you want to use sound to measure the speed of
>light. Even the slightest change in temperature and/or pressure
>would greatly effect the measurement. But most importantly, the
>period of any reasonable sound wave is going to be longer than
>the transit time of the light beam. As you know, it is very
>difficult to find the exact peak of a wave, as it is rather flat
>up there. Long waves make this problem even worse. This is why
>timing experts use high frequency modulated pulses. Of course,
>using light (or electric) signals allows us to use much higher
>frequencies.
Sound has the advantage that it's an harmonic resonance of the molecules,
they move *back AND forth*, thus traveling with and against the motion
of the moving frame, and this is similar on both direction of sound.
Chosing the moment at the central location where the molecule has
done one complete wave solves (perhaps) the problem of sound having
different speeds. Also sound pitch can be compared between directions
of sound, and a bomb can go off if they differ. If you need to change
the signal travel times for either direction of sound to come out on
c for light, you trigger the bomb.
Here in more detail what i thought about sound:
[repost]
In relativity, the extra speed of a molecule
to bumb into the next molecule if that next
molecule is in the direction of motion might
be harder to attain because of (bogus) addition
of velocity laws. However, a complete soundwave
consists of molecules moving back and forth:
| . . . .
| . . . .
|. . . . .
| . . . .
| . . . .
| . . . .
|
That means that sound moving in the direction
of motion might have, if it starts with a pressure
zone, a slower moving pressure zone, then sound
which goes against the direction of motion.
However, the pressure zone is followed by a depressure
zone, where the molecules move in the oposite direction
then with the pressure zone. A depressure zone, where
the molecules travel in the direction oposite then
before will have the oposite relativistic problem:
the soundpressure wave which went slow because it went
in the direction of travel and had to come closer to
c (as computed from a moving frame), will be followed
by a sounddepressure wave which goes fast (the molecules
find it easy to get sucked back to position with the
depressure wave if that direction is oposite the direction
of travel). So, you will end up on sound traveling in
the direction of motion with a pressure wave that goes
slow, which is followed by a depressure wave which brings
the molecules back to their original position rather
quickly:
^higher pressure of liquid
| . .
| . .t=1
| .t=0
| . .
| .
| . .
|
The Sound going against the direction of motion may have
another shape, the pressure wave going easy, and the
lowpressure wave going difficult, because the moleculs
start getting more speed direction motion:
^higher pressure of liquid
| ..t=1
| .
| . .t=0
|. .
| .
| .. .
|
For one molecule to go back and forth one time would take
the same time though, so the /entire/ soundwave would travel
at equal speeds with or against the relative motion of the
entire frame, the shape of the wave would just be different.
If the listening observer would therefore press his timer
at a moment the pressure has equalized again (between wave
crests), he will make a good timing. If he used wavecrests,
he would not make a good timing: the wavecrest from one
side in this measuring device:
+lightdetector lightdetector+
|\____________________________/|
|______________O_______________|
^clock ^liquid tube
might reach him earlier as computed from a moving frame (sic),
then the wavecrest from the other side. For a device as above
moving to the right, this would produce for light being measured
going with the direction of motion to go faster, because the first
pressure pulse would take a long time to reach the clock, while
the pressure pulse from the other side would be fast. Using not
the pressure-wave crest, but the balancing zero pressure point
in a wave (when a molecule has traveled back and forth one time)
resolves this potential problem. Waiting one complete back and forth
and back movement of a molecule is best as this is symetrical on
both sides.
>Let me know if you don't agree, but I would think that splitting
>the actual light beam in two, and having one beam proceed to the
>clock while the other travels the length of the device would give
>us a good experiment. In fact, we could put *both* light detectors
>at the clock if we wished, by simply replacing the second detector
>by a mirror.
Trying to make it a two way lightspeed experiment ?
>The Fizeau (spinning disks) method for measuring the speed of light
>is even simpler to work with as the light either does or doesn't
>get through both holes. All one needs to do is measure the rpm of
>the disks. :)
Well, that's two way isn't it, while SR is about one way light, and
these are theoretical examples, to see if the theory is selfcontradictory
or not (wrong or not).
<snip>
--
jos
William Bliss
I'm going to say something that is not exactly scientific, IOW
there is little theoretical or experimental support for this
idea, but none-the-less quite a few physicists "philosophically"
hold this opinion. The idea is that all matter (atoms, electrons,
etc) are made out of the same stuff that light (photons) are made
out of, whatever *that* is. If this is the case, and it seems to
be so, then all the internal components of matter should already
be moving at the speed of light.
I'm making this slightly less than professional remark because
the intuition that it provides, IMO, overcomes the technical lack
of theoretical support. For example: This idea helps to intuitively
explain time-dilation. If the components of an atom are already
"orbiting" at the speed of light, and light has only one speed,
then as the atom speeds up, from our pov, this orbital frequency
must slow down else the components would be now going faster than
light - which they can't because they *are* light. This is (sort of)
the philosophical pov that aetherists have. No one can say
definitively whether the pov is wrong or right, it's just interesting.
Now here's my point. If atoms are made of "light-stuff" and their
components only move at the speed of light, then properties of
groups of atoms, such as sound, will also be greatly affected by
the speed of light. IOW, if I see your experiment moving fast to
the right then I will predict that light will take longer to go from
the left detector to the right detector than from right to left.
BUT I will also see any moving things, that are made out of light,
to be taking longer to go from the left to the right.
So, if matter is composed of "little hard balls" then none of the
above is true but if matter is made of stuff that only moves at the
observed speed of light then using sound won't make much difference
in your experiment. You might as well use light to collect the timing
signals because that is, in essence, what you are doing with sound.
Of course sound still has other serious disadvantages.
Any way, it is fun to think about.
Wm
HenriWilson
<CUTw...@telocity.com> wrote:
>"josX" <jo...@mraha.kitenet.net> wrote in message
>From the assumption of time dilation we can derive the necessary
>correcting term (vx/cc) found in the LT. A simple situation can
>show why we need this term.
>
>An observer standing along the train tracks sees the train's
>conductor walking slowly forward from car to car while setting
>each car's wall clock from his pocket watch. This observer will
>measure the conductor's speed as slightly faster than the train
>and thusly his pocket watch will be running slightly slower than
>the car's wall clocks. The net result is that, from the observer's
>pov, the train's wall clocks won't agree with each other but will
>show a "time-gradient", often called Esync in this ng. The same
>thing will happen if the conductor starts at the first car and
>walks backwards. Now his pocket watch will appear to be running
>slightly faster than the wall clocks. The actual point here, is
>that no matter how the people or machines on the train attempt to
>synchronize their clocks there will always be this linear error
>in the direction of motion.
Not if they use instantaneous communication instead of EM.
>
>If we use Einstein's velocity composition rule we can easily
>derive the value of this "time-gradient" to be gamma*v*x/cc.
>This all important LT term is the cause of the infamous simultaneity
>"problems" in SR. It is why the x' line in a Minkowski diagram
>is drawn sloping upwards.
>
>Wm
>
>
>
Henri Wilson.
Applied Physicist.
www.users.bigpond.com/rmrabb/HW.htm
HenriWilson
Why the heck should the behavior of clocks be affected by how an observer
views them?
Clocks tick away quite happily whether or not there is any light shining on
them.
Bilge
Re: What happens to SR if velocity of light is not constant? to usenet:
>What would be the modified Lorentz Transformation equations in a universe
>with a variable speed of light?
all that it implies.
--
Stephen Speicher
Hmm. It is rare indeed that I disagree with Bilge about anything
technical (because he is usually so right), but I do disagree
here. Most all varying speed of light theories have been
motivated for solution of cosmological problems, and in the
typical theory covariance and Lorentz invariance is broken.
Lorentz invariance follows directly from the principle of
relativity and the constancy of the speed of light. One can
maintain the indistinguishability of inertial frames, but a
varying speed of light leads to what is known as Fock-Lorentz
symmetry. See Fock's original work in "The Theory of Space-Time
and Gravitation," _Pergamon_, 1964, or more recently Bruce A.
Bassett et al., "Geometrodynamics of variable-speed-of-light
cosmologies," _Physical Review D_, Volume 62, 103518, 15 November
2000.
It is this break of Lorentz invariance which makes these varying
speed of light theories so difficult to apply to problems such as
black holes. It is interesting to note Bassett et al. develop a
Lorentz symmetry which is broken in a "soft" manner, analogous to
spontaneous symmetry breaking in particle physics. However,
there is some recent work by J. Magueijo who has developed a
varying speed of light approach in which it is claimed to be both
generally covariant and locally Lorentz invariant, and he does
apply this new concept to black holes. See J. Magueijo, "Stars
and black holes in varying speed of light theories," _Physical
Review D_, Volume 63, 043502, 18 January 2001.
--
Stephen
s...@compbio.caltech.edu
Printed using 100% recycled electrons.
-----------------------------------------------------------
Bill Hobba
I do not know the technical detail of most of what Stephen is talking about
but as a matter of principle I am forced to agree. A varying light speed
would break Lorentz invariance. His statement 'Lorentz invariance follows
directly from the principle of relativity and the constancy of the speed of
light. One can maintain the indistinguishability of inertial frames, but a
varying speed of light leads to what is known as Fock-Lorentz symmetry' is
right on the money. It expresses my view to a T. A varying light speed
contradicts the foundations of SR. I think it is also at odds with the
principle of SR and locality (ie no way to send information at infinite
speed). I am quite happy to debate this if anyone disagrees.
By the way 'ditto' about Bilge. Both you guys know more about relativity
that I do and I really enjoy reading your stuff.
Thanks
Bill
Stephen Speicher
>
> By the way 'ditto' about Bilge. Both you guys know more about relativity
> that I do and I really enjoy reading your stuff.
>
Thanks.
What is particularly nice about Bilge, is that much of what he
writes seems deceptively simple to some of the characters he
engages, and they do not even realize the depth that is in some
of his responses. Then, of course, every once in a while he takes
the stops out and presents something in its full technical glory,
sending them scurrying back to their books trying to figure out
what he means. Bilge has a great sense of humor.
Bilge
Re: What happens to SR if velocity of light is not constant? to usenet:
>On 22 Aug 2002, Bilge wrote:
>
>> Eugene Shubert said some stuff about
>> Re: What happens to SR if velocity of light is not constant? to usenet:
>> >What would be the modified Lorentz Transformation equations in a universe
>> >with a variable speed of light?
>>
>> No modification. light would simply propagate slower than `c' with
>> all that it implies.
>>
>
>Hmm. It is rare indeed that I disagree with Bilge about anything
>technical (because he is usually so right), but I do disagree
>here. Most all varying speed of light theories have been
>motivated for solution of cosmological problems, and in the
>typical theory covariance and Lorentz invariance is broken.
something more specific than I am. The disagreement is only apparent.
As below:
> Lorentz invariance follows directly from the principle of
>relativity and the constancy of the speed of light.
I am assuming that lorentz invariance consists only of the lorentz
transformation without any assumption about what `c' represents. From
what I see in an article I retreived from lanl by one of the authors you
listed (margueijo), the apparent difference is what one calls "dropping
the second postulate" and lorentz invariance. I dropped the second
postulate implicitly where I made the distinction between `c' and the
speed of light, so that the two are not synonymous. I intended lorentz
invariant and lorentz transform only to refer to the general linear
transform, independent of the physics, so that `c' is a speed (or
parameter) left to be determined. The article considers lorentz
invariance, special relativity and the second postulate to all be tied
to the the speed of light. "Dropping the second postulate" means
essentially the same thing, except the "new" second postulate leads to
an invariance called a "lorentz-fock" symmetry.
>One can maintain the indistinguishability of inertial frames, but
>a varying speed of light leads to what is known as Fock-Lorentz
>symmetry.
Well, this becomes a morass of semantics, since I wouldn't consider
inertial to necessarily have anything to do with the speed of light,
a priori. If your usage is the same as that of magueijo, then inertial
implies a connection to `c'. While the connection undoubtedly exists,
in my opinion the connection is a missing chunk of physics.
>spontaneous symmetry breaking in particle physics. However,
>there is some recent work by J. Magueijo who has developed a
>varying speed of light approach in which it is claimed to be both
>generally covariant and locally Lorentz invariant, and he does
>apply this new concept to black holes. See J. Magueijo, "Stars
>and black holes in varying speed of light theories," _Physical
>Review D_, Volume 63, 043502, 18 January 2001.
My impression based upon the article I have, is that I wasn't being
as restrictive (although, I didn't consider the possibility of speeds
faster than `c' (_not the speed of light here). The author tries
very hard to retain the speed of light without "officially" retaining
it.
Bill Hobba
> I do not know the technical detail of most of what Stephen is talking
about
> but as a matter of principle I am forced to agree. A varying light speed
> would break Lorentz invariance. His statement 'Lorentz invariance follows
> directly from the principle of relativity and the constancy of the speed
of
> light. One can maintain the indistinguishability of inertial frames, but
a
> varying speed of light leads to what is known as Fock-Lorentz symmetry'
is
> right on the money. It expresses my view to a T. A varying light speed
> contradicts the foundations of SR. I think it is also at odds with the
> principle of SR and locality (ie no way to send information at infinite
> speed). I am quite happy to debate this if anyone disagrees.
>
> By the way 'ditto' about Bilge. Both you guys know more about relativity
> that I do and I really enjoy reading your stuff.
>
I was a little concerned after I wrote this what I said may have been
misunderstood. I stated I did not know the technical detail of what Stephen
was talking about but later I agreed 'but a varying speed of light leads to
what is known as Fock-Lorentz symmetry'. I do not know the details of the
Fock-Lorentz symmetry; what I was agreeing with is that fundamental
considerations built into the foundations of SR really do imply that in an
inertial frame the speed of light is constant. I am sure other spotted this
glaring inconsistency and I do appreciate them not pushing the issue.
Thanks
Bill
Bill Hobba
> Not if they use instantaneous communication instead of EM.
And how do you propose to do that?
QM effects will not help - you can not control the sending state so what the
receiving state says is of not use, i.e. they can not be used to send
information.
Anyone able to do this will win a Nobel prize for sure.
Thanks
Bill
Bill Hobba
Bilge wrote;
> I am assuming that lorentz invariance consists only of the lorentz
> transformation without any assumption about what `c' represents. From
> what I see in an article I retreived from lanl by one of the authors you
> listed (margueijo), the apparent difference is what one calls "dropping
> the second postulate" and lorentz invariance. I dropped the second
> postulate implicitly where I made the distinction between `c' and the
> speed of light, so that the two are not synonymous. I intended lorentz
> invariant and lorentz transform only to refer to the general linear
> transform, independent of the physics, so that `c' is a speed (or
> parameter) left to be determined. The article considers lorentz
> invariance, special relativity and the second postulate to all be tied
> to the the speed of light. "Dropping the second postulate" means
> essentially the same thing, except the "new" second postulate leads to
> an invariance called a "lorentz-fock" symmetry.
Interesting view. Of course the principle of SR alone implies the Lorentz
transformations where the constant speed (c in the equations) is
undetermined. Standard arguments such as applying it to Maxwell's
equations, analysis of the MMX etc set it to the speed of light. In order
for it to be different from the speed of light the difference must be quite
small. This would seem to place tight bounds on how much it can change.
While I understand the above ok what concerns me is a simple consideration
as applied to inertial reference frames. They are homogeneous in time. As
I said in a previous reply shine a torch measure the speed. At a later
time shine the same torch and measure the speed again - you should obtain
the same speed. About the only way I can see out of it the torch at a later
time is, in some subtle way, not exactly the same so you would not have the
same experiment. Any comments?
Thanks
Bill
Stephen Speicher
> Stephen Speicher said some stuff about
> Re: What happens to SR if velocity of light is not constant? to usenet:
> >On 22 Aug 2002, Bilge wrote:
> >
> >> Eugene Shubert said some stuff about
> >> Re: What happens to SR if velocity of light is not constant? to usenet:
> >> >What would be the modified Lorentz Transformation equations in a universe
> >> >with a variable speed of light?
> >>
> >> No modification. light would simply propagate slower than `c' with
> >> all that it implies.
> >>
> >
> >Hmm. It is rare indeed that I disagree with Bilge about anything
> >technical (because he is usually so right), but I do disagree
> >here. Most all varying speed of light theories have been
> >motivated for solution of cosmological problems, and in the
> >typical theory covariance and Lorentz invariance is broken.
>
> That's because you are using the term "lorentz invariance" to mean
> something more specific than I am. The disagreement is only apparent.
> As below:
>
> > Lorentz invariance follows directly from the principle of
> >relativity and the constancy of the speed of light.
>
> I am assuming that lorentz invariance consists only of the lorentz
> transformation without any assumption about what `c' represents.
Yes, then we do have only an apparent disagreement, one which has
to do with terminology and the mathematical concepts that such
terminology represent. Historically the Lorentz transformation
was derived from physical arguments, and indeed incorporates the
constancy of the speed of light along with the principle of
relativity.
The general transformation from one set of Minkowski coordinates
in an inertial frame to another is known as the Poincare
transformation, and the set of all such transformations form the
Poincare group. The mathematical structure of the Poincare group
is based on the principle of relativity and is not restricted by
the constancy of the speed of light. The Lorentz group is a
subgroup of the Poincare group, and it consists of the set of
homogeneous transformations satisfying further restrictions.
Bill Hobba
> > Stephen Speicher said some stuff about
> > Re: What happens to SR if velocity of light is not constant? to usenet:
> > >On 22 Aug 2002, Bilge wrote:
> > >
> > >> Eugene Shubert said some stuff about
> > >> Re: What happens to SR if velocity of light is not constant? to
usenet:
> > >> >What would be the modified Lorentz Transformation equations in a
universe
> > >> >with a variable speed of light?
> > >>
> > >> No modification. light would simply propagate slower than `c' with
> > >> all that it implies.
> > >>
> > >
> > >Hmm. It is rare indeed that I disagree with Bilge about anything
> > >technical (because he is usually so right), but I do disagree
> > >here. Most all varying speed of light theories have been
> > >motivated for solution of cosmological problems, and in the
> > >typical theory covariance and Lorentz invariance is broken.
> >
> > That's because you are using the term "lorentz invariance" to mean
> > something more specific than I am. The disagreement is only apparent.
> > As below:
> >
> > > Lorentz invariance follows directly from the principle of
> > >relativity and the constancy of the speed of light.
> >
> > I am assuming that lorentz invariance consists only of the lorentz
> > transformation without any assumption about what `c' represents.
>
> Yes, then we do have only an apparent disagreement, one which has
> to do with terminology and the mathematical concepts that such
> terminology represent. Historically the Lorentz transformation
> was derived from physical arguments, and indeed incorporates the
> constancy of the speed of light along with the principle of
> relativity.
>
> The general transformation from one set of Minkowski coordinates
> in an inertial frame to another is known as the Poincare
> transformation, and the set of all such transformations form the
> Poincare group. The mathematical structure of the Poincare group
> is based on the principle of relativity and is not restricted by
> the constancy of the speed of light. The Lorentz group is a
> subgroup of the Poincare group, and it consists of the set of
> homogeneous transformations satisfying further restrictions.
>
Too true - this I actually know and understand as opposed to some of the
other stuff.
I have been thinking further about this interesting issue and it leads me to
a question Stephen or Bilge may be able to help with.
Apply the Lorentz transformations to Maxwell's equations and it is easy to
see the c it contains is the speed of light. This would seem to be in
direct conflict with a changing light speed, unless of course Maxwell's
equations are not quire correct. We know they a not due to quantum effects
but I am not sure if that is an allowable out here.
Thanks
Bill
Bilge
Re: What happens to SR if velocity of light is not constant? to usenet:
>Apply the Lorentz transformations to Maxwell's equations and it is easy to
>see the c it contains is the speed of light. This would seem to be in
>direct conflict with a changing light speed, unless of course Maxwell's
>equations are not quire correct. We know they a not due to quantum effects
>but I am not sure if that is an allowable out here.
That's my basic point. The second postulate of special relativity
identifies a constant velocity `c' as the the speed of light for the
simple reasons that special relativity sought to explain electrodynamics
from a more fundamental perspective and at the time, the only forces
known, e-m and gravity, appeared to have an infinite range, so that
einstein could just as well have called `c' the speed of gravity, if
he'd had a reason to do so and it wouldn't have mattered. There were
no forces known which had finite ranges. We now know of 2 forces which
do not have infinite ranges, the weak and the strong interactions and
that, in general, the fundamental forces (I'll exclude gravity), have
a potential of the yukawa form:
V = k exp(-r/a)/r
where `a' is the range of the interaction. If `a' is infinite, the
potential reduces to the form, k/r. The constant `a' may be written
in terms of the mass of the particle which mediates the force, which
in general is: a = \hbar/m c, so that r/a = mcr/hbar. For example,
nuclear forces were known to have a range of about 1.5 fm from scattering
experiments, which gives a pion mass of 131 MeV/c^2 (which is about
6 MeV low due to the crude approximation of 1.5 fm for the range).
In the other direction, the measured mass for the W gives about
0.002 fm for the range of the weak interaction.
At this point, one might ask what reason exists that light should be
special. For a very small photon mass, the range would be very close to
infinite and the effects simply too small to have been observed, however
the `c' above would be the speed of something other than light (perhaps
gravity, for example). While there exist lots of plausibility arguments
for a massless photon (and hence `c' == the speed of light), the photon
mass is not forced to be zero by any theory. The unification of the
electromagnetic force and weak interaction could have been accomplished
whatever the photon mass, but was chosen such that electric charge was
conserved (which is also equivalent to a photon mass of zero).
Probably the most compelling argument for light to propagate at `c' is
charge conservation (which really only changes the question), but we'll
assume that it's true, since in all likelyhood it is and stick to the
varying speed of light theories which appear to attempts to solve
cosmological problems. From the above, there is an immediate conflict in
simply allowing `c' to be variable: it can no longer be `c', but is
variable for the simple reason that all velocities for massive particles
are relative [the upper limit on the photon mass makes this irrelevant
from a practical standpoint, so you couldn't measure a difference without
more sensitive instruments). But, because it also implies charge isn't
conserved, a varying speed of light presents a problem. Here, it appears
what was done by the authors (magueijo) from one of stephen's references
(but possibly not the same article although it looks like a preprint):
http://arxiv.org/abs/gr-qc/0007036
is to reparameterize `c' in what he terms "generalized lorentz
invariance". You can read the paper for the details, which are rather
involved, but the upsot is that he gives a reparameterization which is
claimed to preserve the lorentz invariance although the value of `c', is
strictly speaking, variable. (I didn't distinguish between local and
global invariance, which may actually be the most important issue, but the
article does go into detail in that regard and doing so here wouldn't be
nearly as good as going to the source).
Essentially, the bottom line is the varying speed of light theories
seek to have a "constant speed of light" for aspects which matter to
things like conservation of charge, etc., while fixing some cosmological
issues by letting it vary in some limited way. While it may ultimately
prove to be true, all of it is rather speculative.
HenriWilson
wrote:
The fact humans know of no way to achieve instantaneous communication
should not prevent us from conceiving same.
I have previously suggested how an instantaneous measuring system can be
set up, using an infinite grid of synched clocks (synched whilst together
then moved into their positions). So why use light for communication?
>
>Thanks
>Bill
Bill Hobba
> That's my basic point. The second postulate of special relativity
> identifies a constant velocity `c' as the the speed of light for the
> simple reasons that special relativity sought to explain electrodynamics
> from a more fundamental perspective and at the time, the only forces
> known, e-m and gravity, appeared to have an infinite range, so that
> einstein could just as well have called `c' the speed of gravity, if
> he'd had a reason to do so and it wouldn't have mattered.
This has been a pet 'peeve' of mine for some time. As people know I an a
big fan of Rindler - Introduction to Special Relativity. Here he makes your
point in no uncertain terms. The existence of a speed the same in all
inertial reference frames is implied by the principle of SR alone. The role
of the second axiom to fix that speed. This must be done from experimental
evidence and consequences of well accepted theories. It may not be the
speed light actually travels at (of curse it would need to be very close in
order for Maxwell's equations to be valid within experimental error.)
Bilge wrote:
> Probably the most compelling argument for light to propagate at `c' is
> charge conservation (which really only changes the question), but we'll
> assume that it's true, since in all likelyhood it is.
As Stephen wrote you can send people scurrying back to their text books -
you did so with me here. I also seem to recall a rather amusing discussion
I read Feynman had with a certain professor X. He challenged Feynman to
produce evidence that the photon had zero mass. First he asked him to set a
limit on the accuracy and he came up worth an argument to that limit. He
next challenged him to come up with an argument to a greater limit of
accuracy and he did so. This went on until Feynman became upset and accused
the professor of breaking the rules of science - you can not keep changing
your rules as you go. But the bottom line is he gave an argument that
showed the mass of the photon must be close to zero to a very high level of
accuracy.
Thanks
Bill
Eugene Shubert
modified Lorentz Transformation equations would be in a universe that had a
variable maximum possible speed.
Eugene Shubert
http://www.everythingimportant.org
William Bliss
> I believe my original question was misunderstood. I want to know what the
> modified Lorentz Transformation equations would be in a universe that had
a
> variable maximum possible speed.
My guess is the principle of covariance would apply, in this case
from the "top" down. IOW, no physical properties would change
locally. SR would continue to reign while cosmology would get more
funding.
Wm
Bilge
Re: What happens to SR if velocity of light is not constant? to usenet:
>modified Lorentz Transformation equations would be in a universe that had a
>variable maximum possible speed.
I'm not sure I understand the question, nor am I sure any answer is
possible. Are you asking about a case where the maximum is infinity
or one in which `c' is variable, but is in other respects, the same?
When I originally said that the transformation wouldn't change, what I
intended was that the transformation would still be written:
t' = cosh(A)[t - x tanh(A)]
x' = cosh(A)[x - t tanh(A)]
using coordinates in which t is normalized so that t and x have the same
units and the velocity is dimensionless:
So that the velocity is tanh(A) == (\beta) and runs from 0 to 1,
cosh(A) == \gamma, etc. You are free to parameterize the transform-
ation in any way you wish if it agrees with observation and makes
physical sense.
If you make the above differ from the usual lorentz transforms (i.e.,
c == speed of light == constant) you are going to quickly run up against
observations that contradict most any scheme you come up with and not
neccessarily in any immediately obvious way. I mentioned only the most
obvious change which is to just allow the photon to have a tiny mass so
that v_photon depends on the energy, just like any other particle. This
immediately runs into problems, most notable that the electric charge
on the electron depends upon the speed of light via \alpha:
e^2 = [4\pi]\alpha\hbar c
And so that scheme is seriously constrained by the upper limit of the
photon mass from the fact we don't see charge disappear within that limit.
To that extent, it would so far have been impossible to determine a speed
for any energy photon to differ from a constant with current experimental
capability. To get a much better answer to your question than I can give
you, much less present here, see the article I referenced at lanl. It's a
good starting point. It appears to be a preprint for the phys rev D article
stephen mentioned to me. My perspective is definitely not from cosmology.
Bill Hobba
> I believe my original question was misunderstood. I want to know what the
> modified Lorentz Transformation equations would be in a universe that had
a
> variable maximum possible speed.
Again Eugine remember the homogeneity of time in an inertial reference
frame. This implies the maximum speed (whatever value it takes) should be
the same at all instants of time. Unless you are dealing with a non
inertial frame there is no way out I can see. The only other way out is
what Bilge discussed - a very small mass to light. But this does not apply
to the maximum possible speed. Are you thinking of applying Lorentz
transformations to non inertial reference frames? That may be a possibility
but I would need to see the details before I can comment. My first reaction
is that the Lorentz transformations only applies to inertial reference
frames; but I am willing to look at what anyone comes up with.
I have downloaded the article Bilge referred to but have not gone through it
yet. It may provide some clues.
Thanks
Bill
Stephen Speicher
> I believe my original question was misunderstood. I want to know what the
> modified Lorentz Transformation equations would be in a universe that had a
> variable maximum possible speed.
>
I do not think your question was misunderstood, but rather the
discussion which ensued was more general in regard to Lorentz
invariance. Such a "modified" Lorentz transformation is very
much dependent on the physical assumptions you make regarding any
variability of light speed.
To give you a specific example -- a simple one -- let's take what
may be the most simple change to the physical assumptions and see
the effect they have upon the Lorentz transformation. A
generalization of the Lorentz transformation which maintains the
two-way speed of light -- and is therefore consistent with
experiment -- but allows the one-way velocity of light to vary in
terms of a directional parameter, was given by W.F. Edwards in
1963. In another post in an earlier thread I derived some of the
two-way and one-way relationships based on notions of
simultaneity and clock synchronization, and here I will just
state the results which apply to this Edwards generalization.
In the general direction r, the two-way speed of light along a
back and forth path is given by
2(c_r+)(c_r-)
c_r = ---------------
(c_r+) + (c_r-)
c_r+ is the one-way velocity of light along the forward path, and
c_r- is the one-way velocity of light along the return path, and
they are given by
c_r c_r
c_r+ = ------- , c_r- = -------
1 - q_r 1 - q_r
where q_r is the directional parameter in the direction r, given
by
-1 <= q_r <= 1.
So, for instance, in x-y-z coordinates, we would have
c_i c_i
c_i+ = -------, c_i- = -------
1 - q_i 1 + q_i
-1 <= q_i <= 1, i = x,y,z.
In these x-y-z coordinates, for simplicity sake, we will assume
the directional parameter is of the form (q, 0, 0), so that in
frame F we have
c c
c_x+ = ------, c_x- = ------, c_y+ = c_y- = c_z+ = c_z- = c,
1 - q 1 + q
where c is now a constant two-way speed of light. Likewise, for
another frame F', we have
c c
c'_x+ = ------, c'_x- = ------, c'_y+ = c'_y- = c'_z+ = c'_z- = c,
1 - q' 1 + q'
With this as a basis one can then derive, after a lot of algebra,
the Edwards' form of the generalized Lorentz transformation,
which result is
x' = G(x - vt),
y' = y,
z' = z,
t' = G{[1 + (q + q')v/c]t - [(1 - q^2)v/c + (q' -q)]x/c},
1
where G = -----------------------------
sqrt[(1 + qv/c)^2 - (v/c)^2
and v, as usual, is the relative velocity between frames F and
F'.
Note that if the directional parameter is identically zero,
meaning that there is no directional variability to the speed of
light, then this generalized Lorentz transform reduces to the
standard form.
Also, note that another level of complexity is introduced by
assuming that the two-way velocity of light is equal to the
one-way velocity, but allow that velocity to be generally
anistropic, though it remains independent of the motion of the
source. This is known as a Robertson inertial frame, for H.P.
Robertson who first formulated this 1949. And, just as using the
Edwards notion of simultaneity led to a generalization of the
Lorentz transformation with a one-way directional variability of
the speed of light, so the Robertson notion of simultaneity leads
to a further generalization of the Lorentz transformation. The
next level of complexity was introduced by R. Mansouri and R.U.
Sexl in 1977 where the introduced a directional parameter to the
Robertson formulation which leads to a further generalization of
the Lorentz transformation equations. The form of this
generalization is similar to the one I outlined above, but
obviously with somewhat more complicated expressions.
So one can arrive at various forms of an anisotropic
4-dimensional spacetime by relaxing the physical assumptions
imposed in the standard formulation. Below are references of
Edwards', Roberson's, and Mansouri & Sexl's initial work, as well
as a reference to an excellent book which contains these
formulations I have presented, and does so in the context of
experimental relativity.
W.F. Edwards, A. J. Phys. 31 (1963) pp. 482-489.
H.P. Robertson, Rev. Mod. Phys. 21 (1949) p. 378.
R. Mansouri and R.U. Sexl, Gen. Relativ. Grav. 8 (1977) p. 407.
Y. Z. Zhang, "Special Relativity and its Experimental
Foundations," _World Scientific, 1997.
HenriWilson
wrote:
>As Stephen wrote you can send people scurrying back to their text books -
>you did so with me here. I also seem to recall a rather amusing discussion
>I read Feynman had with a certain professor X. He challenged Feynman to
>produce evidence that the photon had zero mass. First he asked him to set a
>limit on the accuracy and he came up worth an argument to that limit. He
>next challenged him to come up with an argument to a greater limit of
>accuracy and he did so. This went on until Feynman became upset and accused
>the professor of breaking the rules of science - you can not keep changing
>your rules as you go. But the bottom line is he gave an argument that
>showed the mass of the photon must be close to zero to a very high level of
>accuracy.
In a fractal universe there is no upper or lower limit to size. A distance
of 10^100 metres is no more significant than one of 10^-100.
A mass of <<10-45 is just as important as one of 10^45.
It all depends on which 'fractal level' one is in..
Bill Hobba
Bill Hobba
> I have downloaded the article Bilge referred to but have not gone through
it
> yet. It may provide some clues.
>
I have had a chance to scan the article (not study, just scan) and as far as
I can see to accomplish the feat of a variable c extra space-time structure
is being proposed. Quite possibly a valid approach, but I am not sure this
is what posters are referring to when they talk about a varying light speed.
The c I mean here is in the sense of a maximum velocity which may or may not
be the speed of light.
thanks
Bill
Dennis McCarthy
>What would be the modified Lorentz Transformation equations in a universe
>with a variable speed of light?
>
The Galilean transformations -- and then we would just correct the measuring
instruments that are physically affected by their motion (like atomic clocks).
But we do this now anyway. Whenever we work with moving clocks (like with GPS)
and accuracy is important, we alter the clocks to keep them synchronized with
lab clocks and use a speed of light that varies with respect to the Earth-based
lab frame.
So not much needs be changed -- just the interpretation has to be tossed.
Dennis McCarthy