The Speed of Light is Not Constant

dmoe said:
Farsight, according to what I was taught and learned of Einstein's theory, I have to agree with your Post #754.

However, some SciForum Members possibly do not completely understand or simply misinterpret Einstein's theory.
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Just as Farsight is wrong in his inference, so are you dmoe, I'm sorry to say....

This definition only makes sense because the speed of light in vacuum is measured to have the same value by all observers; a fact which is subject to experimental verification
from....
http://math.ucr.edu/home/baez/physic...measure_c.html

In any case, there is good observational evidence to indicate that those parameters have not changed over most of the lifetime of the universe.

It is a basic postulate of the theory of relativity that the speed of light is the same in all inertial frames. This can be broken down into two parts:

The speed of light is independent of the motion of the observer.
The speed of light does not vary with time or place.

http://math.ucr.edu/home/baez/physic..._of_light.html
 
Einstein uses the word velocity in his 1905 paper rather than speed, because even for an expanding spherical wave of light, the part of the wavefront that reaches a moving frame will have a velocity like a ray of light.

The difference between spped and velocity is easy to visualise: draw an arbitrary curve and consider a perticle moving along this curve at a constant speed. Its velocity changes as its direction changes, so it accelerates along this curve.

Now imagine a spherical wave is emitted at the start point of the curve, which propagates at a constant speed and whose wavefront intersects the curve, and there's an observer moving along the curve too. The physical restriction is that the moving observer cannot have a greater velocity (speed in any direction), than the speed of propagation of this wavefront.
 
Einstein uses the word velocity in his 1905 paper rather than speed, because even for an expanding spherical wave of light, the part of the wavefront that reaches a moving frame will have a velocity like a ray of light.

The difference between speed and velocity is easy to visualise: draw an arbitrary curve and consider a particle moving along this curve at a constant speed. Its velocity changes as its direction changes, so it accelerates along this curve.

Now imagine a spherical wave is emitted at the start point of the curve, which propagates at a constant speed and whose wavefront intersects the curve, and there's an observer moving along the curve too. The physical restriction is that the moving observer cannot have a greater velocity (speed in any direction), than the speed of propagation of this wavefront.
 
Why is this even being discussed? Farsight has his view, and most people have another that corresponds to what we learn from following Paddoboy's links, if we didn't know it already from classes..
 
paddoboy said:
dmoe said:
Farsight, according to what I was taught and learned of Einstein's theory, I have to agree with your Post #754.

However, some SciForum Members possibly do not completely understand or simply misinterpret Einstein's theory.
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Just as Farsight is wrong in his inference, so are you dmoe, I'm sorry to say....

This definition only makes sense because the speed of light in vacuum is measured to have the same value by all observers; a fact which is subject to experimental verification
from....
http://math.ucr.edu/home/baez/physic...measure_c.html
Click to expand...

paddoboy, the following is from : http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html
(highlights by dmoe!)
Updated 2014 by Don Koks. Original by Steve Carlip (1997) and Philip Gibbs 1996. said:
The Speed of Light as Measured by Non-Inertial Observers

So consider the question: "Can we say that light confined to the vicinity of the ceiling of this room is travelling faster than light confined to the vicinity of the floor?". For simplicity, let's take Earth as not rotating, because that complicates the question! The answer is then that (1) an observer stationed on the ceiling measures the light on the ceiling to be travelling with speed c, (2) an observer stationed on the floor measures the light on the floor to be travelling at c, but (3) within the bounds of how well the speed can be defined (discussed below, in the General Relativity section), a "global" observer can say that ceiling light does travel faster than floor light.

That might sound strange, so let's take it in stages. Begin with the relativity idea that an inertial observer does measure the speed of light to be c. Suppose I want to measure the speed of light that is distant from me. Even though I can't physically interact with a distant photon (if I could, it would no longer be distant), I can employ a continuum of inertial observers placed throughout spacetime, and ask them to make measurements for me of everything happening only in their vicinity. (That's the normal textbook procedure in special relativity.) I do this not because I'm simply employing other people to do my job, but rather because it's possible to set these observers up in such a way that they all agree with me on the distances between objects, and which events are simultaneous. That is, we share a "common ruler" and a "common clock". That way, when I ask myself what "velocity" means (distance travelled over time taken), I have a well-defined set of events to measure, and a well-defined global set of rulers and clocks with which to do it: a job that I can pass on to the band of observers without getting tangled up in ideas of measuring things at a distance, with all the difficulties related to signal-travel times which that would entail.

Only the observer who is close to the photon will interact with it and measure its speed. Assuming the basic postulates of relativity are correct——which tie in with assuming Maxwell's equations are correct (they predict a speed of c for inertial observers)——the observer nearest the photon will measure a speed of c. But because all of the accelerated frame's observers share the same standards of distance and simultaneity (i.e. we all agree on when the stopwatches were started and stopped), I can take the measurement made by my distant associate as "the" speed of light.

Now here's the crucial point. If an observer is sitting up at the ceiling of this room and another is sitting on the floor, and they each have their own identical factory-set clocks and rulers, the ceiling observer measuring light in his vicinity will measure c, and so will the floor observer. But if I now ask these observers to set their clocks and rulers up so that they agree with me on distances and simultaneity——which can be done, although it's not an obvious thing——then things change. I collate their measurements and find that in this "global" uniformly accelerated frame, ceiling light travels faster than floor light, because the clocks involved are actually running at different speeds locally in order for their measurements to be agreed upon by all of the observers who make up the frame. Does this come down simply to an arbitrary setting of clock speeds? No; the clocks must be set to run at different speeds in order for us all to assign the same times to events, and everything is set up in such a way that we all agree on the lengths of rulers. The reason for that lies in special relativity itself, and is not just some artificial thing. The clocks really do reflect the different flows of time on ceiling and floor. It's a nice set-up, but one that can be accomplished only for inertial and uniformly accelerated frames.
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- the ^^above quoted^^ from : http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html

Like I stated in My Post #760 - I only present this as "assistance" for any Members or Readers that would aspire to further learned knowledge of the full aspects of understanding and interpretation of Einstein's theory.

Dr_Toad said:
Why is this even being discussed? Farsight has his view, and most people have another that corresponds to what we learn from following Paddoboy's links, if we didn't know it already from classes..
Click to expand...
The "quoted" information that I Posted above is from the very same Link that paddoboy repeatedly Posted...or you possibly know it already from classes..
 
Farsight said:
No, he'd be turning in his grave at the way general relativity has been traduced. He said what he said about the speed of light varying with position, and he isn't the only one who says it. See what PhysBang said, see the OP, and see the Baez website:
Click to expand...

All this is a set of lies and distractions from the facts that you have a crazy idea that the speed of light varies with position in a manner that diverges violently from GR. You believe that the speed of light differs even at the level of the manifold.

You tell people that you have some special physics knowledge, but you haven't been able to demonstrate that you can do any physics. The evidence says that you are a fraud.
 
Dr Toad said:
Why is this even being discussed? Farsight has his view, and most people have another that corresponds to what we learn from following Paddoboy's links, if we didn't know it already from classes..
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Exactly. Farsight and his his supporter know what is being said, but Farsight and his supporter are trying to reflect some form of "look at me!, I'm rewriting history, by purposely misinterpreting and insidiously ignoring what is actually being said.....
I repeat.....
http://math.ucr.edu/home/baez/physic...measure_c.html

In any case, there is good observational evidence to indicate that those parameters have not changed over most of the lifetime of the universe.

It is a basic postulate of the theory of relativity that the speed of light is the same in all inertial frames. This can be broken down into two parts:

The speed of light is independent of the motion of the observer.
The speed of light does not vary with time or place.

http://math.ucr.edu/home/baez/physic..._of_light.html

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dmoe said:
paddoboy, the following is from : http://math.ucr.edu/home/baez/physic..._of_light.html
(highlights by dmoe!)
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Highlights not needed. They are only put there to reinforce your own lack of knowledge and misinterpretation......


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dmoe highlighted:
paddoboy, the following is from : http://math.ucr.edu/home/baez/physic..._of_light.html
(highlights by dmoe!)
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Ignoring the fact we are talking about Inertial frames.

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dmoe also highlighted:
Now here's the crucial point. If an observer is sitting up at the ceiling of this room and another is sitting on the floor, and they each have their own identical factory-set clocks and rulers, the ceiling observer measuring light in his vicinity will measure c, and so will the floor observer.
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dmoe also highlighted:
But if I now ask these observers to set their clocks and rulers up so that they agree with me on distances and simultaneity——which can be done, although it's not an obvious thing——then things change. I collate their measurements and find that in this "global" uniformly accelerated frame, ceiling light travels faster than floor light, because the clocks involved are actually running at different speeds locally in order for their measurements to be agreed upon by all of the observers who make up the frame.
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And we also have time dilation and length contraction.

My second post to Farsight this morning said the following:
Again, SR and Einstein show the validity of the assumption of the speed of light being constant.
This applies in all Inertial frames.

Einstein showed that SR was a logical, consistent framework that aligned with reality for all non relativistic speeds. . SR also confirmed many other effects including the lifetime of particles.

Your continued misinterpretation of Einstein, and the taking out of context of what he said and proposed, would have the great man turning in his grave.
If this ceiling and floor of this room were in a vacuum, and I was on the ceiling, and you were on the floor, we would both measure the speed of light in our own frames to be, guess what? "c"

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Farsight replied to that thus:
I measure it to be 299,792,458 m/s, and so do you. But your seconds aren't the same as mine. So your 299,792,458 m/s isn't the same as mine. "
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Physbang said:"
All this is a set of lies and distractions from the facts that you have a crazy idea that the speed of light varies with position in a manner that diverges violently from GR. You believe that the speed of light differs even at the level of the manifold.

You tell people that you have some special physics knowledge, but you haven't been able to demonstrate that you can do any physics. The evidence says that you are a fraud.
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The sad part is we have two frauds trying to insidiously distract...I'm not sure which one is the silliest. :shrug:
 
dumbest man on earth said:
paddoboy, the following is from : http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html
(highlights by dmoe!)

- the ^^above quoted^^ from : http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html

Like I stated in My Post #760 - I only present this as "assistance" for any Members or Readers that would aspire to further learned knowledge of the full aspects of understanding and interpretation of Einstein's theory.


The "quoted" information that I Posted above is from the very same Link that paddoboy repeatedly Posted...or you possibly know it already from classes..
Click to expand...

Be careful what you read, since you will tend to take away what you are looking for (that admonishment is mostly for the Farsights of the world. You have some leanings in that direction, which is why I mention it here).

This resurrects the long debated question of the meaning of "coordinate speed of light" which is pointless, other than to shore up the crap Farsight has been selling forever. It has no practical use. Every observer is constrained by his/her reference frame, and hence there is nothing else within a person's own definition of reality which has any meaning other than these two rules: (1) the speed of light is constant in my frame, and every other frame I will ever enter; and (2) every other frame looks to me like the projection of the hyperbolic rotation of the two axes of measurement (time and distance). That's it. There is no more. There is no "coordinate speed"; it's not even real. It's an artifact of introducing a Lorentz rotation by creating a second reference frame, then pretending to not know the frame diverged, and thus pretending that it shouldn't appear warped to me, and yet (of course) it is. This is a needless exercise in frivolous nonsense. So walk lightly here and take the first exit lest you be drawn into that black hole of ignorance that has sucked the Farsights and Reality Checks of the world into its singular compression of nonsense and error.

If you need any help spotting Farsight's cardinal sins, I can point to a recent post echoed by (paddoboy?) in which Farsight tries to claim that the observer's measurement of light speed is contaminated by "a second timeframe" (relative to an initial frame). But of course, if that were true, then length would be warped in the opposite direction, such that the quotient (c) comes out the same. Farsight continually omits this fact, in the manner of a true hardcore troll.

Also beware that all attempts to attack the constancy of c are probably rooted in the fundamentalist attempts to discredit radioisotope dating . . . so they can keep selling tickets to their knucklehead theme park which depicts humans walking the Earth in the Jurassic. My impression of you is that you are somewhat religious, but that you are not stupid enough to buy into the Young Earth fraud on science. But if you follow the Farsights of he world to their end game, odds are you will land up at the Young Earth farm, which is a very lonely place to be . . . for people with even half their wits about them.
 
Write4U said:
Perhaps this might be relevant and of interest,

http://www.youtube.com/watch?v=nByekIx7XXw
Click to expand...

Write4U, interesting yes, and further confirmation of Einstein's actual predictions.
I am fairly certain that most Members of SciForums will fail to see it's relevance to this Thread, though.

As a working Scientific Metrologist since the late 1970's, I fully understand that tying together the Macro- and Micro- Mechanics of the Universe into one Unified ToE is a Herculean task that will probably be many, many decades away, at the very least, and quite possibly never actually be fully accomplished.

Write4U, what did you think of the ABSTRACT at the Link in my Post #760 : Optical Clocks and Relativity by C. W. Chou*, D. B. Hume, T. Rosenband, D. J. Wineland : http://www.sciencemag.org/content/329/5999/1630.abstract , ?
 
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dmoe said:
Write4U, interesting yes, and further confirmation of Einstein's actual predictions.
I am fairly certain that most Members of SciForums will fail to see it's relevance to this Thread, though.
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Well of course most reputable members will see the relevance, but likewsie I'm sure the same reputable people will certainly see that it was not confirmation that you are desperately trying to get us to believe.


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dmoe said:
As a working Scientific Metrologist since the late 1970's, I fully understand that tying together the Macro- and Micro- Mechanics of the Universe into one Unified ToE is a Herculean task that will probably be many, many decades away, at the very least, and quite possibly never actually be fully accomplished."
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Working Metrologist, erh. One would then expect you to be far more scientific in your posts contribution to the forum.
But we don't really see that too often. So, yes doubt would exist in some minds as to those claims.


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dmoe said:"
Write4U, what did you think of the ABSTRACT at the Link in my Post #760 : Optical Clocks and Relativity by C. W. Chou*, D. B. Hume, T. Rosenband, D. J. Wineland : http://www.sciencemag.org/content/32.../1630.abstract , ?
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Except for the new precision with the measurements, it's SR, pure and simple.

from your link Abtsract:
Observers in relative motion or at different gravitational potentials measure disparate clock rates. These predictions of relativity have previously been observed with atomic clocks at high velocities and with large changes in elevation. We observed time dilation from relative speeds of less than 10 meters per second by comparing two optical atomic clocks connected by a 75-meter length of optical fiber. We can now also detect time dilation due to a change in height near Earth’s surface of less than 1 meter. This technique may be extended to the field of geodesy, with applications in geophysics and hydrology as well as in space-based tests of fundamental physics.
 
A question for dmoe.
Dmoe, instead of hanging on Farsight's coat tails, you need to take in the actual facts about SR.
The whole theory of SR rests on two postulates:-
[1] The laws of physics are the same in all FoR's:
[2] In any Inertial FoR, the speed of light "c" is constant, whether by a body at rest, or one in uniform motion


From those two postulates was deduced the facts of time dilation, and length contraction.

And briefly that sums it up from a layman's position which you and I should really have no qualms about, as it has stood up to all scrutiny for more than a 100 years.
To doubt those findings, you must have observational evidence.
Does that make it clearer?
 
The following reputable member, puts it far better than I can......

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rpenner said:
Experimentally, the locally-measured speed of light in vacuum remains the same no matter the velocity of the observer relative to the source or a third party and no matter the velocity of the source relative to the observer or a third party.

If you ignore effects due to gravity, the measured speed of light in vacuum remains the same no matter the velocity of the observer relative to the source or a third party and no matter the velocity of the source relative to the observer or a third party. This has been tested with light from moving stars and fast-moving particles in the lab. This has been tested with moving observers to 8 digits of precision in one-way isotropy tests and 18 digits of precision with two-way tests. In 1978 it was discovered that we can measure the speed of light to a greater precision than we could the length of the meter under the old definition, so in 1983 the international definition of the meter was changed to be in terms of the duration of a second and the new definition of the accepted value of the speed of light.

So not only is light speed constant, in international trade it is defined to be constant. And relying on this has been useful.
http://www.sciforums.com/showthread...-constant-because-light-remains-a-certain-way
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dumbest man on earth said:
Farsight, according to what I was taught and learned of Einstein's theory, I have to agree with your Post #754.

However, some SciForum Members possibly do not completely understand or simply misinterpret Einstein's theory.

The "Internet" or SciForums is not the proper "classroom" for teaching nor learning Einstein's theory.

Since some 'reputable sources' are evidently needed, I supply the following in hopes that it will help to alleviate any possible misunderstanding or misinterpretation of Einstein's theory by any SciForum Members or Readers of this Thread...

I only present this as "assistance" for any Members or Readers that would aspire to further learned knowledge of the full aspects of understanding and interpretation of Einstein's theory.
Click to expand...
Thanks dmoe. But sadly looking at the responses, I don't think it's going to help. Nothing you say or refer to will make any difference. The forum is plagued with abusive dishonest ignorant trolls, and there's just no talking to them.
 
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Farsight said:"
Thanks dmoe. But sadly looking at the responses, I don't think it's going to help. Nothing you say or refer to will make any difference. The forum is plagued with abusive dishonest ignorant trolls, and there's just no talking to them.
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Sadly it's obvious that statement can be taken with a grain of salt, taking into account you also claim to have a ToE.
 
A couple of problems exist in this thread with regards to Farsight and dmoe.
Firstly both have issues with accepted cosmology in general. That is obviously blinkering their views of the problem at hand.
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rpenner said
However, if we take the general relativistic description seriously, then the explanation for the apparent slowing of the speed of light is that there is actually more space near the Sun than there would be if the spacetime there was flat, because in fact the spacetime is curved. The light therefore has further to travel, which takes longer, even though its speed through the vacuum remains constant.
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Quite logically obvious due to curved spacetime in the presence of mass....Longer distance to travel, and you would think that no one could have any problem with that.
Think again!

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Farsight replied to rpenner:
You've got it utterly wrong. Spacetime isn't space, it's an abstract mathematical model which is utterly static. The speed of light is not constant therefore your plot, your metric, is curved.
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Most should know that space is a 3 dimensional framework in which the mass/energy of the Universe exists.
This was later modified to 4 dimensional spacetime, with the advent of SR/GR.
And it has been shown that this same spacetime will bend, warp, twist in the presence of mass, and as shown by GP-B.

The other point that comes into contention is time dilation and length contraction, quite obvious at relativitic speeds but not so noticeable at normal speeds..
These have also been verified many times.

dmoe on the other hand, has shown and admitted he has trouble accepting the BB model.
So Farsight does not accept that spacetime is curved, and dmoe has trouble accepting the BB.


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dmoe said:
1. - Mainstream cosmology seems to have accepted the BB (though I have not!) - As far as I know the WH part has not even been given it's honest "day in court", let alone be accepted. Also it is not commonly accepted that the BB started from anything other than "nothing" - so would not require any "other" or "previous" state of "existence".
http://www.sciforums.com/showthread.php?135733-Black-holes-White-Holes-and-Baby-Universes
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So maybe both need to be reminded that this is not the "Alternative hypothesis" forum, and if they have Alternative models, bring them up in the appropriate section, using accepted scientific methodology and get them properly peer reviewed.
 
Now you're spouting total nonsense. I've referred to curved spacetime on many occasions.

You're just an ignorant naysayer, and you can't even work out how to quote somebody. You're back on ignore you troll.
 
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