Grumpy, the coordinate speed of light varies in a non-inertial reference frame. Such as a gravitational field. I'm not lying to you about all this.
At Rest with our Hubble view
- Thread starter quantum_wave
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While I'm no fan of Farsight's ideas in general, on this one matter of light speed I have to agree. Those quotes given in #1250 of AE's own words on the subject are either accepted for what they say, or rejected as 'the ravings of a crackpot'. And who is willing to say that AE was a crackpot viz-a-viz his own theory?!
Much fuss has been made over the invariance of c, without clearly indicating or admitting that when gravity is involved, this invariance is restricted to that determined in a local inertial frame. It should be obvious that Shapiro delay is proof that gravity slows the coordinate speed of light:
https://en.wikipedia.org/wiki/Tests_of_general_relativity#Light_travel_time_delay_testing
https://en.wikipedia.org/wiki/Shapiro_delay
And via ubiquitous YouTube:
https://www.youtube.com/watch?v=nkFZayu4kuQ
How about an admission from some here that Einstein's quoted words have real and meaningful applicability - as tested.
Much fuss has been made over the invariance of c, without clearly indicating or admitting that when gravity is involved, this invariance is restricted to that determined in a local inertial frame. It should be obvious that Shapiro delay is proof that gravity slows the coordinate speed of light:
https://en.wikipedia.org/wiki/Tests_of_general_relativity#Light_travel_time_delay_testing
https://en.wikipedia.org/wiki/Shapiro_delay
And via ubiquitous YouTube:
https://www.youtube.com/watch?v=nkFZayu4kuQ
How about an admission from some here that Einstein's quoted words have real and meaningful applicability - as tested.
Reading back over the last few posts makes me think that maybe we are conflating maps with territory. The speed of light in a vacuum is a real property, no matter if we say it is 300,000k/s or 186,000mi/s or don't bother to measure it at all, it's still a real property(territory)that our description(map)quantifies in terms our brains can work with. A particle or photon has no map, they simply obey the laws that are built into their substance and the spacetime they exist in. And lightspeed is in there, too. No matter how or in what terms we describe it with.
Grumpy
Grumpy
Coordinate-dependent entities, such as the coordinate speed of light are not measurable. So, your fake "horizontal clock experiment" is not explained by the "coordinate speed of light". I have already debunked your crackpot idea, you waited a few weeks, hoping that I'll forget and you came back with the same crank stuff. Give it a rest, Duffield.
It is hilarious to see you aligning yourself with the resident crank, Farsight.
Einstein wrote about "variable speed of light" in 1911, before he developed GR, when he was trying to shoehorn gravitation into SR. Unlike you and Farsight, Einstein realized his error and he did not repeat the 1911 statement.
The above is the standard fare crackpot claim. To correct your misconception, the Shapiro delay is proof of gravitation affecting the light velocity (as in gravitational lensing), not the light speed. You are making the same crank claims as John Duffield (Farsight), this should give you some pause.
You the fool, and you the crackpot. Go read those quotes again - AE held to that '1911 position' up to 1916 (that's after full GR was finalized in 1915 btw) and beyond. But crackpot's won't admit that. Nor will they accept the context in which those statements of Einstein rightly and accurately apply. Invariance of c locally is essentially a triviality that ignores the need to usefully compare 'here' with 'there' whenever gravity enters the picture. Hence Shapiro delay etc.
You the fool, and you the crackpot. Go read the first quoted wiki article I provided, and actually learn something:
Unfortunately, and i regret to have to say this, the world will be that much a better place when bitter, egotistical and combative-by-default Tach is finally laid to rest.
It is entertaining to see that you are using the same arguments as your fellow crackpot, Farsight. The calendar reads 2013, Einstein changed his position once he published his GR papers. Only cranks like you hold tight on the quote from the 1911 paper.
Err, Shapiro delay is proof of varying light velocity, not varying light speed. You are dutifully regurgitating the same crank arguments as Farsight. You obviously do not understand the difference.
Since the discussion is circling the same familiar crank talking points Farsight likes the always wheel out this is going to pseudo
Well, its not surprising that you fail to understand what Lao Tzu was saying. Lao Tzu did not understand it, and neither does anyone else. The only sentence that has real meaning in the verse is the one where he explains that we can't talk about the Tao. It is outside of our experience. We don't have the language, or even the concepts in our mind to talk about the "Creation" of the universe. We can only use words that don't fit.
Another great man, Stephen Hawking said that asking about time before the big bang was like what is north of the north pole. You are probably going to parse those words in your way and make them mean what you want them to mean, just as you did the Tao Te Ching. Well, we are now in Pseudoscience so anything goes. Enjoy.
You haven't debunked anything, Tach. And this is not my idea. It's Einstein's.
Well said Q-reeus.
Guys, see this article on John Baez's website. Look at the general relativity section.
"Einstein went on to discover a more general theory of relativity which explained gravity in terms of curved spacetime, and he talked about the speed of light changing in this new theory. In the 1920 book "Relativity: the special and general theory" he wrote: . . . according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [. . .] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Since Einstein talks of velocity (a vector quantity: speed with direction) rather than speed alone, it is not clear that he meant the speed will change, but the reference to special relativity suggests that he did mean so. This interpretation is perfectly valid and makes good physical sense"
This backs me up. Note however the next sentence is this:
"but a more modern interpretation is that the speed of light is constant in general relativity".
And the last sentence is this:
"Finally, we come to the conclusion that the speed of light is not only observed to be constant; in the light of well tested theories of physics, it does not even make any sense to say that it varies".
So this article says Einstein thought the speed of light varied and that this makes good sense, and then says it doesn't make sense. Duh!
Sadly, what you've been taught is not in accord with Einstein.
There is no way you can get around the facts. Einstein said "velocity of light" in every statement you quoted. You said "speed of light" when you summed it up. Those are different concepts. You can't use those quotes to justify the idea that Einstein said the "speed of light is variable". Sorry it just can't work for you. It does not matter that curvature and delta v are the same thing. It is what Einstein said, and I thnk he knew full well what he was saying. If he had meant the speed of light, then that is what he would have said.
But we are in Pseudoscience now. Believe what you want. Enjoy.
Or so you believe.
He talked about it, you talked about, and I replied to those comments.
Infnite non-occupied space is outside of experience of a finite Universe of occupied space. If you think that is beyond our ability to comprehend then your mistaken. imho.
Lots of "great" men state things in their lives and may even revise their previous statements over time. I've read at least one of his books and seen many quotes attributed to him. I was referencing Brian Greene's book Elegant Universe and my interpretation of what is meant with his words.
Sure Cheezle, find me someone who does not parse comments of other and have offer their interpretations thereof. I addressed your comments as you specifically stated them. If I'm in error with any of my comments then please state my error and give your rationale for stating your claims.
My statements stand as stated until such time some other can address them as specifically stated, and offer a counter argument and their rationale for their statements.
r6
Q-reeus
Shapiro may be wrong. Simple geometry could be a better explanation, a curved path is longer than a straight one, giving different transit times even with identical speeds. I'll wait for further confirmation for Shapiro's idea. I would note that the vectors for the light approaching and leaving the gravity well are part of his equations, like I said, geometry.
Farsight
You are simply wrong about that, frequency changes, speed does not. THERE IS NO SUCH THING AS SLOW LIGHT IN A VACUUM, even within gravity fields, no such thing has ever been measured, just one exception would make all light move at different speeds, yet we see no light that does not move at exactly lightspeed in a vacuum. A curved path will give you longer transit times between two points(as opposed to a path that is not curved)even with identical speeds. Close to a Black Hole there is a point where transit time between the surface of an Event Horizon and all points outside of that EH will approach infinity(giving infinite transit times)because the curvature of all possible vectors through spacetime only lead inward, but the speed of the light will still be the same. After time stops we have no clue what occurs, if anything. Einstein called them "frozen stars" for a reason. But the light from or passing through even the deepest gravity wells will move through spacetime at lightspeed.
Grumpy
Shapiro may be wrong. Simple geometry could be a better explanation, a curved path is longer than a straight one, giving different transit times even with identical speeds. I'll wait for further confirmation for Shapiro's idea. I would note that the vectors for the light approaching and leaving the gravity well are part of his equations, like I said, geometry.
Farsight
You are simply wrong about that, frequency changes, speed does not. THERE IS NO SUCH THING AS SLOW LIGHT IN A VACUUM, even within gravity fields, no such thing has ever been measured, just one exception would make all light move at different speeds, yet we see no light that does not move at exactly lightspeed in a vacuum. A curved path will give you longer transit times between two points(as opposed to a path that is not curved)even with identical speeds. Close to a Black Hole there is a point where transit time between the surface of an Event Horizon and all points outside of that EH will approach infinity(giving infinite transit times)because the curvature of all possible vectors through spacetime only lead inward, but the speed of the light will still be the same. After time stops we have no clue what occurs, if anything. Einstein called them "frozen stars" for a reason. But the light from or passing through even the deepest gravity wells will move through spacetime at lightspeed.
Grumpy
No he didn't, and you've already been proved wrong re your '1911 only'. See last link I provide in answer to Grumpy.
The nonsense is yours not mine. Gravitationally induced variation of velocity necessarily goes hand-in-hand with speed variation. And evidently you wish to deny validity of that wiki article I quoted from in #1266, which directly contradicts your position. So you deny the only rational and physically consistent explanation for Shapiro delay. Too bad. But as you will see, there are those that maintain your position - based on what I consider a strained definition.
Frustratingly Baez, after giving an unequivocal nod to Einstein's position there, never qualifies his following and apparently contradictory stance that |c| does not vary. My suspicion is he/they choose to interpret using some projection method that 'factors out' variation in coordinate length scale and clock-rate. Which amounts to saying the locally observed value is trivially going to always be c - on that basis. My second linked article in answer to Grumpy suggests that is the case.
If and it seems clear that 'by geometry' you mean simply a changed length of light path owing to deflection, well no the unequivocal answer is that cannot anywhere near explain the delay. Which as per that quoted wiki article, is overwhelmingly owing to varying clock-rate (and a part owing to varying length scale) en-route, and imo one is playing with words to interpret that other than 'light slows down' - naturally on a coordinate basis.
I was though surprised to find that argumentation over |c| varying or not owing to gravity is reflected at e.g.:
http://physics.stackexchange.com/questions/59502/does-gravity-slow-the-speed-that-light-travels
Methinks the nay crowd are using a particular definition, and the clue is given in this piece:
http://curious.astro.cornell.edu/question.php?number=266
Notice it boils down there to always referencing to the locally observed value, which logically and trivially must always be c. My vote goes strongly to the following, yay position, which btw shows that Einstein - late in his life, maintained that c does indeed vary in magnitude - obviously on a coordinate basis:
http://www.speed-light.info/speed_of_light_variable.htm
Given there are amazingly two different schools of thought here, it seems pointless arguing over which is the right one since it becomes a matter of preferred definition rather than basic physics.
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Communication Requires Integrity and Desire To Communicate. imho
I think I was clear on my points that addressed nearly every statement by you. That you have no reply, to even one of my comments, is your failure to to communicate, not mine.
I've always done my best to attempt communication with elaboration and clarifying and statements when asked or neccesary.
If you find some error in my comments please share/communicate as I'm here for you or any who are interested in having rationally logical conversation
You do not address my comments specifically as state, because I was not in error with any of my given statements.. Simple not complex.
r6
I think I was clear on my points that addressed nearly every statement by you. That you have no reply, to even one of my comments, is your failure to to communicate, not mine.
I've always done my best to attempt communication with elaboration and clarifying and statements when asked or neccesary.
If you find some error in my comments please share/communicate as I'm here for you or any who are interested in having rationally logical conversation
You do not address my comments specifically as state, because I was not in error with any of my given statements.. Simple not complex.
r6
Ah yes, I forgot how Einstein was infallible and all that.
For the record, I haven't dismissed anything by Einstein. I do, however, benefit from the insights of others, my own insights and understanding of GR, and the benefit of several decades of hindsight that Einstein never had.
There's nothing to dismiss. Your usual line of argument is always either: 1) This famous person said this, I like this explanation, therefore it's correct, or 2) Look at this experiment, here's an explanation for it I like, therefore it is the correct one. Neither of these is an acceptable argument in scientific discourse.
This is a blatant denial of GR. The principle of general covariance is still very much the heart of GR.
The link you provided cites the paper from 1911. Give it a rest, cranko, the calendar says year 2013, only you and Farsight are still stuck in 1911.
This nonsense is what you've learned at crank university? The very links you cite contradict your wacko claims.
"Why doesn't gravity change the speed of light?
How come that the speed of light "c" doesn't change at all, even slightly, when the light passes closely to a star or some similar big object. We know that light bends in those situations, but what about "c"?
Yep, although light bends around a massive object like a black hole, the speed of that light in a vacuum is always the same. This is because the speed of light is directly dependent on the speed of the interaction between the electric and magnetic fields (light is an electro-magnetic wave, after all!). That speed of interaction is the same no matter where the light is or who is watching it. Therefore, the speed of light is the same for all observers at all points in space-time.
In other words, the light bends around the massive object, but the graduate students all along the light's path will always measure it moving at the same speed: the speed of light. "