Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > sci.physics.relativity > #422962 > unrolled thread

Valid and Invalid Arguments in Special Relativity

Back to article view | Back to sci.physics.relativity

Contents

  Valid and Invalid Arguments in Special Relativity Pentcho Valev <pvalev@yahoo.com> - 2017-06-19 03:57 -0700
    Re: Valid and Invalid Arguments in Special Relativity Rhett Doucet <ttdh@etoe.ee> - 2017-06-19 13:30 +0000
    Re: Valid and Invalid Arguments in Special Relativity Gary Harnagel <hitlong@yahoo.com> - 2017-06-19 06:35 -0700
    Re: Valid and Invalid Arguments in Special Relativity Pentcho Valev <pvalev@yahoo.com> - 2017-06-19 07:47 -0700
      Re: Valid and Invalid Arguments in Special Relativity Gary Harnagel <hitlong@yahoo.com> - 2017-06-19 09:19 -0700
    Re: Valid and Invalid Arguments in Special Relativity Tom Roberts <tjroberts137@sbcglobal.net> - 2017-06-19 22:51 -0500
      Re: Valid and Invalid Arguments in Special Relativity Ned Latham <nedlatham@woden.valhalla.oz> - 2017-06-20 02:36 -0500
        Re: Valid and Invalid Arguments in Special Relativity Gary Harnagel <hitlong@yahoo.com> - 2017-06-20 04:06 -0700
          Re: Valid and Invalid Arguments in Special Relativity Ned Latham <nedlatham@woden.valhalla.oz> - 2017-06-20 06:51 -0500
            Re: Valid and Invalid Arguments in Special Relativity Odd Bodkin <bodkinodd@gmail.com> - 2017-06-20 08:26 -0500
              Re: Valid and Invalid Arguments in Special Relativity Ned Latham <nedlatham@woden.valhalla.oz> - 2017-06-20 09:09 -0500
                Re: Valid and Invalid Arguments in Special Relativity Odd Bodkin <bodkinodd@gmail.com> - 2017-06-21 11:12 -0500
                Re: Valid and Invalid Arguments in Special Relativity Odd Bodkin <bodkinodd@gmail.com> - 2017-06-21 16:56 +0000
            Re: Valid and Invalid Arguments in Special Relativity Gary Harnagel <hitlong@yahoo.com> - 2017-06-20 07:07 -0700
              Re: Valid and Invalid Arguments in Special Relativity Ned Latham <nedlatham@woden.valhalla.oz> - 2017-06-20 10:38 -0500
                Re: Valid and Invalid Arguments in Special Relativity Gary Harnagel <hitlong@yahoo.com> - 2017-06-20 09:53 -0700
                  Re: Valid and Invalid Arguments in Special Relativity Ned Latham <nedlatham@woden.valhalla.oz> - 2017-06-20 19:50 -0500
                    Re: Valid and Invalid Arguments in Special Relativity Gary Harnagel <hitlong@yahoo.com> - 2017-06-20 19:45 -0700
                      Re: Valid and Invalid Arguments in Special Relativity Lipek Mniak <iluka@sskwpiw.pp> - 2017-06-21 12:18 +0000
                Re: Valid and Invalid Arguments in Special Relativity Odd Bodkin <bodkinodd@gmail.com> - 2017-06-21 11:12 -0500
              Re: Valid and Invalid Arguments in Special Relativity Nicolaas Vroom <nicolaas.vroom@pandora.be> - 2017-06-21 13:22 -0700
                Re: Valid and Invalid Arguments in Special Relativity Gary Harnagel <hitlong@yahoo.com> - 2017-06-21 18:08 -0700
                  Re: Valid and Invalid Arguments in Special Relativity Nicolaas Vroom <nicolaas.vroom@pandora.be> - 2017-06-22 02:10 -0700
                    Re: Valid and Invalid Arguments in Special Relativity mlwozniak@wp.pl - 2017-06-22 02:52 -0700
                      Re: Valid and Invalid Arguments in Special Relativity Nicolaas Vroom <nicolaas.vroom@pandora.be> - 2017-06-22 03:47 -0700
                        Re: Valid and Invalid Arguments in Special Relativity mlwozniak@wp.pl - 2017-06-22 04:16 -0700
                    Re: Valid and Invalid Arguments in Special Relativity Gary Harnagel <hitlong@yahoo.com> - 2017-06-22 06:17 -0700
                      Re: Valid and Invalid Arguments in Special Relativity mlwozniak@wp.pl - 2017-06-22 06:40 -0700
                      Re: Valid and Invalid Arguments in Special Relativity Nicolaas Vroom <nicolaas.vroom@pandora.be> - 2017-06-23 02:30 -0700
                        Re: Valid and Invalid Arguments in Special Relativity mlwozniak@wp.pl - 2017-06-23 03:49 -0700
                        Re: Valid and Invalid Arguments in Special Relativity Odd Bodkin <bodkinodd@gmail.com> - 2017-06-23 07:32 -0500
                          Re: Valid and Invalid Arguments in Special Relativity mlwozniak@wp.pl - 2017-06-23 05:53 -0700
                        Re: Valid and Invalid Arguments in Special Relativity Gary Harnagel <hitlong@yahoo.com> - 2017-06-23 06:38 -0700
                          Re: Valid and Invalid Arguments in Special Relativity Valok Planek <lkupuu@kwklewan.oo> - 2017-06-24 10:27 +0000
                Re: Valid and Invalid Arguments in Special Relativity Tom Roberts <tjroberts137@sbcglobal.net> - 2017-06-23 09:43 -0500
        Re: Valid and Invalid Arguments in Special Relativity Odd Bodkin <bodkinodd@gmail.com> - 2017-06-20 11:20 +0000
          Re: Valid and Invalid Arguments in Special Relativity Ned Latham <nedlatham@woden.valhalla.oz> - 2017-06-20 06:54 -0500
            Re: Valid and Invalid Arguments in Special Relativity Odd Bodkin <bodkinodd@gmail.com> - 2017-06-20 08:29 -0500
              Re: Valid and Invalid Arguments in Special Relativity Ned Latham <nedlatham@woden.valhalla.oz> - 2017-06-20 09:17 -0500
                Re: Valid and Invalid Arguments in Special Relativity Odd Bodkin <bodkinodd@gmail.com> - 2017-06-21 11:12 -0500
                Re: Valid and Invalid Arguments in Special Relativity Odd Bodkin <bodkinodd@gmail.com> - 2017-06-21 17:11 +0000
        Re: Valid and Invalid Arguments in Special Relativity Tom Roberts <tjroberts137@sbcglobal.net> - 2017-06-20 09:03 -0500
          Re: Valid and Invalid Arguments in Special Relativity Ned Latham <nedlatham@woden.valhalla.oz> - 2017-06-20 10:24 -0500
            Re: Valid and Invalid Arguments in Special Relativity Eshiki Orakut <usa@iwikuh.ki> - 2017-06-20 16:54 +0000
            Re: Valid and Invalid Arguments in Special Relativity Tom Roberts <tjroberts137@sbcglobal.net> - 2017-06-20 20:05 -0500
      Re: Valid and Invalid Arguments in Special Relativity Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-06-20 18:56 +0200
        Re: Valid and Invalid Arguments in Special Relativity Tom Roberts <tjroberts137@sbcglobal.net> - 2017-06-20 20:17 -0500
          Re: Valid and Invalid Arguments in Special Relativity Eshiki Orakut <usa@iwikuh.ki> - 2017-06-21 09:38 +0000
    Re: Valid and Invalid Arguments in Special Relativity JanPB <filmart@gmail.com> - 2017-06-20 02:48 -0700
      Re: Valid and Invalid Arguments in Special Relativity Eshiki Orakut <usa@iwikuh.ki> - 2017-06-20 13:05 +0000

Page 2 of 3 — ← Prev page 1 [2] 3  Next page →

#423215

On Tuesday, 20 June 2017 16:07:30 UTC+2, Gary Harnagel  wrote:
> On Tuesday, June 20, 2017 at 5:51:52 AM UTC-6, Ned Latham wrote:
> >
> > 
> > So it's not a physical theory.
> 
> wrong xxxxxxxx.  It is deduced from four postulates.  The
> invariance of the speed of light is experimentally confirmed, as is the
> principle of relativity as well as the other postulates.

The central question towards the speed of light is, if this speed is 
the same everywhere in the universe.
IMO this physical means that the time for a light pulse going from A to B, 
being a distance d0, is always the same for any two points A and B when
the distance is d0.
IMO this is in general very difficult to establish experimental.
One "accepted" rule is that the speed of light is always the same in vacuum.
The problem with this rule is first exactly what is a vacuum and secondly is 
there eveywhere in the universe a vacuum. Specific if the second condition 
is not fullfilled how usefull is this accepted rule?  

One experimental condition of how light pulses travel is not accordingly
to straight lines i.e. they are bended when an object (mass) interfers
in the path going from A to B. More general this path is influenced
by a gravitational field. 
When that is true the next question is: does such a gravitaional field
also influence the speed of a light pulse?
To be more specific is the speed of light from a lightpulse emitted by the 
Sun towards the earth always exactly the same?  
There are two reasons which can influence the answer: as caused by the Sun
as caused by the Earth. 

> 
> > >           QED does.
> > 
> > QED is an interpretation of QM,
> 
> Completely wrong, xxxx.
> 
> > which is inconsistent with Einsteinian relativity.
> 
> Nope, xxx, QED is based on special relativity.
> 
> > That's what the kerfuffle over the loss of "String Theory"
> > is all about, remember?
> 
> No, xxx , string theory is based on QED with the assumption
> that particles aren't points and gravity is produced by gravitons.  The
> "kerfuffle" (commotion) over string theory is its inability to make 
> concrete predictions.
> 
> > > BTW, light travels in "vacuum" not "vacuum."
> > 
> > Really? I always thought it was vacuum, myself.
> > 
> > > Do you believe that "vacuum" is nothing?
> > 
> > Nope. Do you?
> 
> Nope.

Nicolaas Vroom
http://users.pandora.be/nicvroom

[toc] | [prev] | [next] | [standalone]

#423225

On Wednesday, June 21, 2017 at 2:22:24 PM UTC-6, Nicolaas Vroom wrote:
>
> On Tuesday, 20 June 2017 16:07:30 UTC+2, Gary Harnagel  wrote:
> >
> > wrong xxxxxxxx.  It is deduced from four postulates.  The
> > invariance of the speed of light is experimentally confirmed, as is the
> > principle of relativity as well as the other postulates.
> 
> The central question towards the speed of light is, if this speed is 
> the same everywhere in the universe.

It may not be since we haven't been anywhere but in our own solar system.
But it would not make sense to assert that it IS different without good
evidence.

> IMO this physical means that the time for a light pulse going from A to B, 
> being a distance d0, is always the same for any two points A and B when
> the distance is d0.

That's a very constrained view.  What it REALLY means is that the ratio of
the distance to the time it takes light to cover that distance is a constant.

But in fact, it is much more convenient to measure the round-trip time and
multiply the ratio by 2.

> IMO this is in general very difficult to establish experimental.

Not really.  It is more difficult to measure the case where the distance
between A and B is changing.

> One "accepted" rule is that the speed of light is always the same in vacuum.
> The problem with this rule is first exactly what is a vacuum

Again, not really.  The effects of index of refraction vs. pressure are well-
characterized.

> and secondly is there eveywhere in the universe a vacuum.

We're not all over the universe, so that's irrelevant.

> Specific if the second condition is not fullfilled how usefull is this
> accepted rule?  

It is consistent with spacecraft throughout the solar system.

> One experimental condition of how light pulses travel is not accordingly
> to straight lines i.e. they are bended when an object (mass) interfers
> in the path going from A to B. More general this path is influenced
> by a gravitational field.

This is also well-known: it's called Shapiro delay, and it can only
be detected when e/m radiation passes very close to a mass.

> When that is true the next question is: does such a gravitaional field
> also influence the speed of a light pulse?

Yes, see "Shapiro delay."

> To be more specific is the speed of light from a lightpulse emitted by the 
> Sun towards the earth always exactly the same?  
> There are two reasons which can influence the answer: as caused by the Sun
> as caused by the Earth. 

The sun is by far the largest contributor.

[toc] | [prev] | [next] | [standalone]

#423239

On Thursday, 22 June 2017 03:08:51 UTC+2, Gary Harnagel  wrote:
> On Wednesday, June 21, 2017 at 2:22:24 PM UTC-6, Nicolaas Vroom wrote:
> > The central question towards the speed of light is, if this speed is 
> > the same everywhere in the universe.
> 
> It may not be since we haven't been anywhere but in our own solar system.
> But it would not make sense to assert that it IS different without good
> evidence.

That is the same in both "directions". When you make either claim you need
evidence. 

> > IMO this physical means that the time for a light pulse going from  
> > A to B, being a distance d0, is always the same for any two points 
> > A and B when the distance is d0.
> 
> That's a very constrained view.  What it REALLY means is that the ratio of
> the distance to the time it takes light to cover that distance is a constant.

In that view you always need a clock.
 
> But in fact, it is much more convenient to measure the round-trip time and
> multiply the ratio by 2.

In that view you calculate the average speed. The physical process that 
describes how photons move can be more subtle. 
 
> > IMO this is in general very difficult to establish experimental.
> 
> Not really.  It is more difficult to measure the case where the distance
> between A and B is changing.
> 
> > One "accepted" rule is that the speed of light is always the same in 
> > vacuum. The problem with this rule is first exactly what is a vacuum
> 
> Again, not really. The effects of index of refraction vs. pressure are 
> well-characterized.

Sorry, IMO that does not clarify what a vacuum is.
 
> > and secondly is there eveywhere in the universe a vacuum.
> 
> We're not all over the universe, so that's irrelevant.

As far as I know we don't live in a vacuum, so for us it is relevant.
 
> > More general this path is influenced
> > by a gravitational field.
> 
> This is also well-known: it's called Shapiro delay, and it can only
> be detected when e/m radiation passes very close to a mass.
>
> > When that is true the next question is: does such a gravitaional field
> > also influence the speed of a light pulse?
> 
> Yes, see "Shapiro delay."
>

And is this in agreement with the concept of the:
    "invariance of the speed of light"? 
I have my doubts.

Nicolaas Vroom 

[toc] | [prev] | [next] | [standalone]

#423240

W dniu czwartek, 22 czerwca 2017 11:10:32 UTC+2 użytkownik Nicolaas Vroom napisał:

> And is this in agreement with the concept of the:
>     "invariance of the speed of light"? 
> I have my doubts.

Learn the newspeak of a relativistic moron.
When screaming "SPEED OF LIGHT IS INVARIANT!!!!!"
he means "in inertial frames", i.e. nowhere.

[toc] | [prev] | [next] | [standalone]

#423241

On Thursday, 22 June 2017 11:52:03 UTC+2, mlwo...@wp.pl  wrote:
> W dniu czwartek, 22 czerwca 2017 11:10:32 UTC+2 użytkownik Nicolaas Vroom napisał:
> 
> > And is this in agreement with the concept of the:
> >     "invariance of the speed of light"? 
> > I have my doubts.
> 
> Learn the newspeak of a relativistic moron.
> When screaming "SPEED OF LIGHT IS INVARIANT!!!!!"
> he means "in inertial frames", i.e. nowhere.

Sorry, I'am not screaming.
I only try to understand what people in this newsgroup mean
Sorry.

Nicolaas Vroom

[toc] | [prev] | [next] | [standalone]

#423242

W dniu czwartek, 22 czerwca 2017 12:47:12 UTC+2 użytkownik Nicolaas Vroom napisał:
> On Thursday, 22 June 2017 11:52:03 UTC+2, mlwo...@wp.pl  wrote:
> > W dniu czwartek, 22 czerwca 2017 11:10:32 UTC+2 użytkownik Nicolaas Vroom napisał:
> > 
> > > And is this in agreement with the concept of the:
> > >     "invariance of the speed of light"? 
> > > I have my doubts.
> > 
> > Learn the newspeak of a relativistic moron.
> > When screaming "SPEED OF LIGHT IS INVARIANT!!!!!"
> > he means "in inertial frames", i.e. nowhere.
> 
> Sorry, I'am not screaming.
> I only try to understand what people in this newsgroup mean
> Sorry.

I understand, and that's why I'm explaining you what
they mean.

[toc] | [prev] | [next] | [standalone]

#423254

On Thursday, June 22, 2017 at 3:10:32 AM UTC-6, Nicolaas Vroom wrote:
>
> On Thursday, 22 June 2017 03:08:51 UTC+2, Gary Harnagel  wrote:
> >
> > On Wednesday, June 21, 2017 at 2:22:24 PM UTC-6, Nicolaas Vroom wrote:
> > >
> > > The central question towards the speed of light is, if this speed is 
> > > the same everywhere in the universe.
> > 
> > It may not be since we haven't been anywhere but in our own solar system.
> > But it would not make sense to assert that it IS different without good
> > evidence.
> 
> That is the same in both "directions". When you make either claim you need
> evidence. 

Not really.  If you claim without evidence that the laws of physics are
different from what they are locally, you are violating the law of
parsimony (Occam's razor).  It amounts to sheer speculation.

> > > IMO this physical means that the time for a light pulse going from  
> > > A to B, being a distance d0, is always the same for any two points 
> > > A and B when the distance is d0.
> > 
> > That's a very constrained view.  What it REALLY means is that the ratio
> > of the distance to the time it takes light to cover that distance is a
> > constant.
> 
> In that view you always need a clock.

For your approach, you at least need a distance tool, else you can't set
up a distance d0.  And you need an assumption that d0 doesn't chance when
you move it.  And you need TWO synchronized clocks since you can't directly
compare time of flight at different locations and you're only measuring
one way.  It's much easier to measure round-trip time since you only need
one clock.  But you still need a distance tool.

> > But in fact, it is much more convenient to measure the round-trip time and
> > multiply the ratio by 2.
> 
> In that view you calculate the average speed. The physical process that 
> describes how photons move can be more subtle. 

Without evidence it is sheer speculation.  If you want that, one might claim
that any "physical process" occurs on the sub-picosecond level and thus
averages out over even very short distances.  One might also speculate
that the "physical process" involves the virtual particle sea or quantum
foam.

> > > IMO this is in general very difficult to establish experimental.
> > 
> > Not really.  It is more difficult to measure the case where the distance
> > between A and B is changing.
> > 
> > > One "accepted" rule is that the speed of light is always the same in 
> > > vacuum. The problem with this rule is first exactly what is a vacuum
> > 
> > Again, not really. The effects of index of refraction vs. pressure are 
> > well-characterized.
> 
> Sorry, IMO that does not clarify what a vacuum is.

Then you must explain yourself more carefully.

> > > and secondly is there eveywhere in the universe a vacuum.
> > 
> > We're not all over the universe, so that's irrelevant.
> 
> As far as I know we don't live in a vacuum, so for us it is relevant.

Only locally.  Saying we don't live in a vacuum is obvious, but most of
space is pretty empty.

> > > More general this path is influenced
> > > by a gravitational field.
> > 
> > This is also well-known: it's called Shapiro delay, and it can only
> > be detected when e/m radiation passes very close to a mass.
> >
> > > When that is true the next question is: does such a gravitaional field
> > > also influence the speed of a light pulse?
> > 
> > Yes, see "Shapiro delay."
> >
> 
> And is this in agreement with the concept of the:
>     "invariance of the speed of light"? 
> I have my doubts.
> 
> Nicolaas Vroom

The invariance of the speed of light is local.  If you were in a g field
and measured the speed of light over a distance short enough so the g
field didn't significantly vary, you would measure it as c.  The Shapiro
effect occurs when the light passes through a changing g field.

[toc] | [prev] | [next] | [standalone]

#423257

W dniu czwartek, 22 czerwca 2017 15:17:29 UTC+2 użytkownik Gary Harnagel napisał:

> The invariance of the speed of light is local.  If you were in a g field
> and measured the speed of light over a distance short enough so the g
> field didn't significantly vary, you would measure it as c.

And walking  street, you would see trees and buildings
running around you. It's obvious, isn't it? If it isn't
you're stupid and you don't understand, that great Galileo
said...
The same situation you have with measurements. You
can geat any result, but if your results won't match
the mumble of relativistic moron, he will scream and
spit until you deliver proper results to him.

[toc] | [prev] | [next] | [standalone]

#423302

On Thursday, 22 June 2017 15:17:29 UTC+2, Gary Harnagel  wrote:

> Not really.  If you claim without evidence that the laws of physics are
> different from what they are locally, you are violating the law of
> parsimony (Occam's razor).  It amounts to sheer speculation.

Sorry, I'am not claiming anything.
I'am only asking the question if the speed of light is constant.
What you are saying (my interpretation): Yes locally.
My reply would be: that is not a full answer.
IMO a better answer would be: it depends.
 
> 
> For your approach, you at least need a distance tool, else you can't set
> up a distance d0.  And you need an assumption that d0 doesn't chance when
> you move it.  And you need TWO synchronized clocks since you can't directly
> compare time of flight at different locations and you're only measuring
> one way.  
This text is in agreement with my understanding that to measure the speed
of light, in order to answer my question is difficult.
> It's much easier to measure round-trip time since you only need
> one clock.  
In that case you get an average speed. 
> But you still need a distance tool.
Ofcourse.

> > > But in fact, it is much more convenient to measure the round-trip time and
> > > multiply the ratio by 2.
> > 
> > In that view you calculate the average speed. The physical process that 
> > describes how photons move can be more subtle. 
> 
> Without evidence it is sheer speculation.  

That is correct, but you "close the book" by calling the speed of light
a physical constant (locally), stopping all possible future experiments. 

> > > > and secondly is there eveywhere in the universe a vacuum.
> > > 
> > > We're not all over the universe, so that's irrelevant.
> > 
> > As far as I know we don't live in a vacuum, so for us it is relevant.
> 
> Only locally.  Saying we don't live in a vacuum is obvious, but most of
> space is pretty empty.

This is also a reason to assume that the speed of light is not every where
the same.
 
> > And is this in agreement with the concept of the:
> >     "invariance of the speed of light"? 
> > I have my doubts.
> 
> The invariance of the speed of light is local.  If you were in a g field
> and measured the speed of light over a distance short enough so the g
> field didn't significantly vary, you would measure it as c.  The Shapiro
> effect occurs when the light passes through a changing g field.

This implies that when the g field varies significant you can measure
the it as not being equal to c (to c0).
It also means that when you measure it more accurately in a g field 
that varies from place to place, you can measure different values for c.
(Even here on earth). This complies with my answer: it depends

Nicolaas Vroom

[toc] | [prev] | [next] | [standalone]

#423305

W dniu piątek, 23 czerwca 2017 11:30:07 UTC+2 użytkownik Nicolaas Vroom napisał:

> > The invariance of the speed of light is local.  If you were in a g field
> > and measured the speed of light over a distance short enough so the g
> > field didn't significantly vary, you would measure it as c.  The Shapiro
> > effect occurs when the light passes through a changing g field.
> 
> This implies that when the g field varies significant you can measure
> the it as not being equal to c (to c0).
> It also means that when you measure it more accurately in a g field 
> that varies from place to place, you can measure different values for c.
> (Even here on earth). This complies with my answer: it depends

Not quite. Real answer is: physics can't tell how
to measure it and can't tell what the result would 
be. It's beyond the range of its definitions.

Great job, isn't it?

[toc] | [prev] | [next] | [standalone]

#423319

On 6/23/17 4:30 AM, Nicolaas Vroom wrote:
> On Thursday, 22 June 2017 15:17:29 UTC+2, Gary Harnagel  wrote:
> 
>> Not really.  If you claim without evidence that the laws of physics are
>> different from what they are locally, you are violating the law of
>> parsimony (Occam's razor).  It amounts to sheer speculation.
> 
> Sorry, I'am not claiming anything.
> I'am only asking the question if the speed of light is constant.
> What you are saying (my interpretation): Yes locally.
> My reply would be: that is not a full answer.
> IMO a better answer would be: it depends.

Actually his answer is better than that, because it's less wishy-washy 
than "it depends". It is not true that the speed of light is constant in 
an absolute sense. But what IS true is that in any local environment 
where the curvature of spacetime is smaller than experimental resolution 
would be able to detect, the speed of light in vacuum will always be 
measured to be constant. That's as definitive as it gets.


-- 
Odd Bodkin -- maker of fine toys, tools, tables

[toc] | [prev] | [next] | [standalone]

#423321

W dniu piątek, 23 czerwca 2017 14:32:19 UTC+2 użytkownik Odd Bodkin napisał:
> On 6/23/17 4:30 AM, Nicolaas Vroom wrote:
> > On Thursday, 22 June 2017 15:17:29 UTC+2, Gary Harnagel  wrote:
> > 
> >> Not really.  If you claim without evidence that the laws of physics are
> >> different from what they are locally, you are violating the law of
> >> parsimony (Occam's razor).  It amounts to sheer speculation.
> > 
> > Sorry, I'am not claiming anything.
> > I'am only asking the question if the speed of light is constant.
> > What you are saying (my interpretation): Yes locally.
> > My reply would be: that is not a full answer.
> > IMO a better answer would be: it depends.
> 
> Actually his answer is better than that, because it's less wishy-washy 
> than "it depends".

:)
No, poor idiot. Your Shit has no answer for this case.
Assuming that common sense is a set of prejudices has
some side effects.


> It is not true that the speed of light is constant in 
> an absolute sense. But what IS true is that in any local environment 
> where the curvature of spacetime is smaller than experimental resolution 
> would be able to detect, the speed of light in vacuum will always be 
> measured to be constant. 

Or, if it isn't, a relativistic maron will
wave hands, spit and scream "UNPROPER!!!!!"

[toc] | [prev] | [next] | [standalone]

#423322

On Friday, June 23, 2017 at 3:30:07 AM UTC-6, Nicolaas Vroom wrote:
>
> On Thursday, 22 June 2017 15:17:29 UTC+2, Gary Harnagel  wrote:
> >
> > Not really.  If you claim without evidence that the laws of physics are
> > different from what they are locally, you are violating the law of
> > parsimony (Occam's razor).  It amounts to sheer speculation.
> 
> Sorry, I'am not claiming anything.
> I'am only asking the question if the speed of light is constant.

By asking the question you are making a claim by innuendo.

> What you are saying (my interpretation): Yes locally.
> My reply would be: that is not a full answer.
> IMO a better answer would be: it depends.

Locally (within the solar system), it does not "depend."

Observation of stars strongly imply that the same laws of physics which we
have discovered locally also apply in the observable universe.
 
> > For your approach, you at least need a distance tool, else you can't set
> > up a distance d0.  And you need an assumption that d0 doesn't chance when
> > you move it.  And you need TWO synchronized clocks since you can't directly
> > compare time of flight at different locations and you're only measuring
> > one way.
>
> This text is in agreement with my understanding that to measure the speed
> of light, in order to answer my question is difficult.

Two-way measurement is not so difficult.

> > It's much easier to measure round-trip time since you only need
> > one clock.
> 
> In that case you get an average speed.

You also get "an average speed" measuring one-way.  And you have not
specified why the speed would not be constant when traveling in different
directions, which I infer is what YOU mean by "average."  Measurements
of light-speed isotropy refute that idea.
 
> > But you still need a distance tool.
>
> Ofcourse.
> 
> > > > But in fact, it is much more convenient to measure the round-trip
> > > > time and multiply the ratio by 2.
> > > 
> > > In that view you calculate the average speed. The physical process that 
> > > describes how photons move can be more subtle. 
> > 
> > Without evidence it is sheer speculation.  
> 
> That is correct, but you "close the book" by calling the speed of light
> a physical constant (locally), stopping all possible future experiments. 

You seem to believe that two-way experiments are the only kind that have
been performed.  Two-way plus isotropy experiments (i.e., using the
Mossbauer effect) refute the idea that light travels at different speeds
when moving in different directions. 

> > > > > and secondly is there eveywhere in the universe a vacuum.
> > > > 
> > > > We're not all over the universe, so that's irrelevant.
> > > 
> > > As far as I know we don't live in a vacuum, so for us it is relevant.
> > 
> > Only locally.  Saying we don't live in a vacuum is obvious, but most of
> > space is pretty empty.
> 
> This is also a reason to assume that the speed of light is not every where
> the same.

No, it's not.  Communication with spacecraft tell us that the speed of
light throughout the solar system is quite constant, and any deviations
are well-explained by present theories.

> > > And is this in agreement with the concept of the:
> > >     "invariance of the speed of light"? 
> > > I have my doubts.
> > 
> > The invariance of the speed of light is local.  If you were in a g field
> > and measured the speed of light over a distance short enough so the g
> > field didn't significantly vary, you would measure it as c.  The Shapiro
> > effect occurs when the light passes through a changing g field.
> 
> This implies that when the g field varies significant you can measure
> the it as not being equal to c (to c0).
> It also means that when you measure it more accurately in a g field 
> that varies from place to place, you can measure different values for c.
> (Even here on earth). This complies with my answer: it depends
> 
> Nicolaas Vroom

Just what is your point?  It is a well-understood effect.  Your "it
depends" is an undefined, nebulous claim whereas the actual dependencies
are well-characterized.

[toc] | [prev] | [next] | [standalone]

#423351

Gary Harnagel wrote:

>> In that case you get an average speed.
> 
> You also get "an average speed" measuring one-way.  And you have not
> specified why the speed would not be constant when traveling in
> different directions, which I infer is what YOU mean by "average." 
> Measurements of light-speed isotropy refute that idea.

You too wrong. Light cannot have anything averaged. A propagation delay is 
either constant or wrong. Wrong timing. But is not. That's why we have 
Relativity, explaining that the event propagation delay is NOT wrong.

[toc] | [prev] | [next] | [standalone]

#423325

On 6/21/17 6/21/17   3:22 PM, Nicolaas Vroom wrote:
> The central question towards the speed of light is, if this speed is
> the same everywhere in the universe.

That's not really "central" in any useful or meaningful sense. But it is an 
interesting question.

Theoretically, of course, GR predicts that the LOCAL speed of light in vacuum is 
c everywhere and everywhen, and also that the non-local speed can vary.

Experimentally, that question is essentially impossible to answer directly, 
because we cannot place measuring instruments everywhere in the universe.

But there are indirect tests that shed light on the question. In particular, one 
can look at atomic lines in distant galaxies. Once an overall redshift is 
accounted for, the patterns are the same as we observe on earth, implying that 
the physical constants used in modeling them are the same. This includes both 
hbar and c, as well as the masses of electrons and nuclei.

> IMO this physical means that the time for a light pulse going from A to B,
> being a distance d0, is always the same for any two points A and B when
> the distance is d0.

This is essentially useless, without any method to measure distance and time 
LOCALLY.

	For instance, if you see two stars separated by a measured angle,
	and independently you can measure their distance from earth, you
	cannot reliably compute the distance between them using Euclidean
	geometry, as you don't know that the geometry actually is
	Euclidean. You cannot separate measurements of distance from the
	geometry.

> One experimental condition of how light pulses travel is not accordingly
> to straight lines i.e. they are bended when an object (mass) interfers
> in the path going from A to B. More general this path is influenced
> by a gravitational field.

Well known and unremarkable -- this is solidly established experimentally. Light 
follows a null geodesic path through spacetime, not a straight line in space.

> When that is true the next question is: does such a gravitaional field
> also influence the speed of a light pulse?

No, locally. Yes, when measured over a non-local distance or path. See the 
Shapiro time delay.

> To be more specific is the speed of light from a lightpulse emitted by the
> Sun towards the earth always exactly the same?

Hmmmm. One can calculate this in GR. Over time, the speed remains the same over 
a given path. At different radii, the speed varies, but by an amount that is not 
measurable by any solar orbiter or other spacecraft flown so far.

Tom Roberts

[toc] | [prev] | [next] | [standalone]

#423080

Ned Latham <nedlatham@woden.valhalla.oz> wrote:
> Tom Roberts wrote:
>> 
>> There are no valid ARGUMENTS against Special Relativity, as it is
>> a PHYSICAL THEORY.
> 
> Except that it doesn't have anything to say about how a waveform can
> travel in vaccuum.
> 

But quantum field theories do.  

-- 
Odd Bodkin -- maker of fine toys, tools, tables

[toc] | [prev] | [next] | [standalone]

#423084

Odd Bodkin wrote in <oib0ef$1jsb$3@gioia.aioe.org>:
> Ned Latham <nedlatham@woden.valhalla.oz> wrote:
> > Tom Roberts wrote:
> > > 
> > > There are no valid ARGUMENTS against Special Relativity, as it is
> > > a PHYSICAL THEORY.
> > 
> > Except that it doesn't have anything to say about how a waveform can
> > travel in vaccuum.
>
> But quantum field theories do.  

Irrelevant. SR and GR predate all of them, and they're inconsistent with
them anyway.

[toc] | [prev] | [next] | [standalone]

#423098

On 6/20/17 6:54 AM, Ned Latham wrote:
> Odd Bodkin wrote in <oib0ef$1jsb$3@gioia.aioe.org>:
>> Ned Latham <nedlatham@woden.valhalla.oz> wrote:
>>> Tom Roberts wrote:
>>>>
>>>> There are no valid ARGUMENTS against Special Relativity, as it is
>>>> a PHYSICAL THEORY.
>>>
>>> Except that it doesn't have anything to say about how a waveform can
>>> travel in vaccuum.
>>
>> But quantum field theories do.
> 
> Irrelevant. SR and GR predate all of them, and they're inconsistent with
> them anyway.
> 

It's not irrelevant. SR did not claim to have all the answers, nor does 
ANY theory. ANY theory is a set of propositions that apply to certain 
domains and not ALL domains. There is no theory to date that claims to 
be an explanation for any and all phenomena. Each theory is an 
INCREMENTAL step in answering a few more questions.

SR is not at all inconsistent with quantum field theory. QFT is FULLY 
Lorentz-covariant.

What is true is that no quantum field theory has been found that is 
compatible with GENERAL relativity. That's an increment that has yet to 
be made.

-- 
Odd Bodkin -- maker of fine toys, tools, tables

[toc] | [prev] | [next] | [standalone]

#423116

The Slow Bot, ala Odd Bodkin wrote:
> Ned Latham wrote:
> > The Slow Bot, aka Odd Bodkin wrote:
> > > Ned Latham wrote:
> > > > Tom Roberts wrote:
> > > > >
> > > > > There are no valid ARGUMENTS against Special Relativity, as it is
> > > > > a PHYSICAL THEORY.
> > > >
> > > > Except that it doesn't have anything to say about how a waveform can
> > > > travel in vaccuum.
> > >
> > > But quantum field theories do.
> >
> > Irrelevant. SR and GR predate all of them, and they're inconsistent with
> > them anyway.
>
> It's not irrelevant.

Wrong agaon. Skow Bot. SR and GR predate all quantum field theworues. IOW,
SR is NOT a physical theory.

----snip----

[toc] | [prev] | [next] | [standalone]

#423191

On 6/20/17 9:17 AM, Ned Latham wrote:
> The Slow Bot, ala Odd Bodkin wrote:
>> Ned Latham wrote:
>>> The Slow Bot, aka Odd Bodkin wrote:
>>>> Ned Latham wrote:
>>>>> Tom Roberts wrote:
>>>>>>
>>>>>> There are no valid ARGUMENTS against Special Relativity, as it is
>>>>>> a PHYSICAL THEORY.
>>>>>
>>>>> Except that it doesn't have anything to say about how a waveform can
>>>>> travel in vaccuum.
>>>>
>>>> But quantum field theories do.
>>>
>>> Irrelevant. SR and GR predate all of them, and they're inconsistent with
>>> them anyway.
>>
>> It's not irrelevant.
> 
> Wrong agaon. Skow Bot. SR and GR predate all quantum field theworues. IOW,
> SR is NOT a physical theory.
> 
> ----snip----
> 

What does presaging have to do with anything, other than indicating that 
one incremental step toward a better understanding was made before the 
next step?

-- 
Odd Bodkin -- maker of fine toys, tools, tables

[toc] | [prev] | [next] | [standalone]

Page 2 of 3 — ← Prev page 1 [2] 3  Next page →

Back to top | Article view | sci.physics.relativity

csiph-web