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Relativity Video Course By Brian Greene

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#1 ralfcis

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Posted 17 February 2019 - 02:50 PM

https://www.youtube....1bNhVUgDLTwVbFc



#2 Moronium

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Posted 17 February 2019 - 03:09 PM

Well, nothing conclusive there.

 

Einstein said the speed of light was constant regardless of the speed of it's source.  In the eariler video, Greene says more than that.  He says it's also independent of the speed of the receiver.   But Einstien's own examples claim otherwise.  The GPS proves otherwise.

 

It is my understanding that the speed of ALL waves (sound waves, water waves, etc.) is independent of the speed of it's source, so light is nothing unique in that sense.

 

In his binary star example, you obviously can't directly compare light emitted from the "top" of the orbit with that emitted from the "bottom" of the orbit, anyway.  They are emitted at different times. How would you even know when the the light you are seeing "now" actually left the star?

 

P.S.  Put "youtube"in front of your link, and "/youtube" behind it, but put it in brackets  That way the video itself will appear here.


Edited by Moronium, 17 February 2019 - 03:29 PM.


#3 Moronium

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Posted 17 February 2019 - 03:47 PM

Here's a link to an exhaustive article that was published in the General Science Journal which deals with the binary star issue.  Different theories can explain what we see in different ways, equally well.  De Sitter proposed the explanation which Greene offers in 1913.  However, this article claims that:

 

It follows, therefore, that de Sitter's conclusion that the existence of spectroscopic binary stars is a strong proof for the constancy of the speed of light is unwarranted and incorrect; because it's based entirely on the treatment of two instants of light traveling at (c + v) and two instants of light traveling at (c – v), emitted by the binary star in one single orbital period, and neglecting everything else emitted by the same binary star before or between or after these four special instants.

 

 

The author's ultimate conclusion is:

 

All in all, in conclusion, therefore, it is not the assumption of additive speed of starlight that might be in danger of being falsified by binary stars. Contrary to the aforementioned de Sitter's demonstration, it is the current astronomy that may well be compelled, in the foreseeable future, to relabel half of its inventory of real objects as mere optical manifestations of the other half.

 

 

 

http://www.gsjournal...s/Download/5693

 

That's why you can't prove a scientific hypothesis--there are always alternative explanations for the phenomena.


Edited by Moronium, 17 February 2019 - 03:56 PM.


#4 ralfcis

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Posted 17 February 2019 - 03:54 PM

 "But Einstien's own examples claim otherwise.  The GPS proves otherwise. " false. This course is 100% faithful to einstein so you are mistaken, not einstein or greene. You can approach a sound wave and the relative velocity between you will inclrease. But if you approach a light wave it will not increase because you can't have a relative velocity higher than c. This is the relativistic velocity combo law.

 

Yes The course may be faithful to Einstein but it's not faithful to science. His idea that light, being a wave, moves like a particle is absurd. No wave's velocity  is affected by the speed of the source, it's velocity is only dependent on the elasticity and inertia of the medium. His example has nothing to do with relativity and it's wrong anyways.



#5 Moronium

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Posted 17 February 2019 - 04:55 PM

I might also add that De Sitter was basically arguing against a ballistic theory of light.  One that is different from Ritz's theory.

 

But, either way, even assuming that De Sitter was correct, that would just defeat the ballistic theory.  It would not "prove" that the speed of light is invariant.  That speed could vary for a number of other reasons, such as light extinction.

 

Many modern theorists are playing with theories which posit that light speed varies.  Hell, even GR says it varies.


Edited by Moronium, 17 February 2019 - 04:58 PM.


#6 Moronium

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Posted 17 February 2019 - 05:19 PM

Here's an excerpt from a recent academic paper:

 

In 1908 Walter von Ritz suggested that the speed of light is equal to the constant c only when measured relative to the source. Ritz systematically redeveloped Maxwellian electrodynamics bringing it into agreement with this hypothesis....

 

The Ritz theory came to an end with the work of W. de Sitter (1913) who claimed to have a convincing argument for showing that the hypothesis of Ritz was inconsistent with the results of spectroscopic observations of binary stars.

 

To refute de Sitter's argument, it would be sufficient to assume that the speed of light adjusts to the value of c at the vicinity of Earth and other celestial bodies. The authors show that this assumption added to the Ritz hypothesis explains well spectroscopic observations of the binary stars.

 

This combined hypothesis: the Ritz ballistic hypothesis and the adjustment of the speed of light to c near celestial bodies (in particular near the Earth), also explains experiments performed at CERN in 1964. An additional argument in favor of the suggested hypothesis is the derivation of the formula for the transverse Doppler Effect presented in this work.

 

 

http://wiki.naturalp...elestial_Bodies

 

Maybe it all aint quite that simple. Mr. Greene.


Edited by Moronium, 17 February 2019 - 05:20 PM.


#7 marcospolo

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Posted 17 February 2019 - 09:49 PM

Here's a link to an exhaustive article that was published in the General Science Journal which deals with the binary star issue.  Different theories can explain what we see in different ways, equally well.  De Sitter proposed the explanation which Greene offers in 1913.  However, this article claims that:

 

 

The author's ultimate conclusion is:

 

 

 

http://www.gsjournal...s/Download/5693

 

That's why you can't prove a scientific hypothesis--there are always alternative explanations for the phenomena.

Wow, Moronium, are you learning from me?

The bold bit is exactly what I say, but when I say it everyone jumps on me.

The difference is maybe that I gravitate towards the explanation that requires the least suppression of my skepticism.



#8 Moronium

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Posted 26 February 2019 - 03:59 PM

 "But Einstien's own examples claim otherwise.  The GPS proves otherwise."  false. This course is 100% faithful to einstein so you are mistaken, not einstein or greene. 

 

The GPS rejects SR and adopts a preferred frame theory of relativity.

 

Einstein repeatedly assumes absolute motion, and even uses it to "prove" that simultaneity is relative.

 

Not that you could be expected to know any of that, but, still.....


Edited by Moronium, 26 February 2019 - 04:03 PM.


#9 Moronium

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Posted 17 March 2019 - 07:20 PM

Measurement of Differences and Relativity between Speeds of Light from Various Stars

©2014 The Physical Society of Japan

 

To check whether the speed of light is influenced by the relative motion between the source and the observer or by the travelling time, we must find a system with a very long transmission path and a large relative motion between the light source and the receiver end.

 

The speed of light is dimensional and expressed in terms of length per unit time. To measure the speed of light, we need a ruler and a watch. Especially to measure the speed of light emitting from a moving source, we encounter the simultaneity problem. Here we design a system accordingly to directly measure the speeds of light from the distant moving sources. Because we compare the speed of light from the distant moving sources with the well-known value, c, which is the speed of light from a resting source and measured on the Earth, we can avoid the previously mentioned problems.

 

Conclusion:  We have accomplished a simple method for measuring the speeds of light from extraterrestrial sources, namely Aldebaran, Capella, Arcturus and Vega. This method compares the travelling time intervals of these starlights and the local light from the transmitter to the receiver. Such that definitions of dimensional units problem can be avoided. We also analyze the possible errors which are likely tolerable. In our measurement, the results show that the speeds of starlights are different from the speed of terrestrial light.

 

 

 

https://journals.jps.../JPSCP.1.014019

 

The hypothesis is merely that the speed of light will be measured to be the same in all inertial frames, while they are in fact different.

 

The only reason a moving frame measures the speed of light to be the same is because it is using distorted measuring instruments, i.e. clocks whose tick rates have been retarded, and rods whose lengths have been contracted.


Edited by Moronium, 17 March 2019 - 07:52 PM.


#10 Moronium

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Posted 17 March 2019 - 08:49 PM

Greene should have known better than to use De Sitter's arguments.  They were rejected long ago.

 

...De Sitter established an upper limit of k < 0.002, but extinction effects make that result suspect.[4]  De Sitter's experiment was criticized because of extinction effects by J. G. Fox. That is, during their flight to Earth, the light rays would have been absorbed and re-emitted by interstellar matter nearly at rest relative to Earth, so that the speed of light should become constant with respect to Earth, regardless of the motion of the original source(s).[8]  In 1977, Kenneth Brecher published the results of a similar double-survey, and reached a similar conclusion....

 

 

https://en.wikipedia...star_experiment