If there is no Ether how can we talk about light being a wave?
Einstein wrote in one of his 1918 papers:
“There, empty space in the previous sense has physical qualities, mathematically characterized by the components of the potential of gravitation that determine the metrical behavior of that portion of space as well as its gravitational field. This situation can very well be interpreted by speaking of an ether whose state varies from point to point.”
He wrote in one of his 1920 papers:
”Recapitulating, we may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether. According to the general theory of relativity space without ether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense.”
Why do we need Ether to talk about light being a wave?
An “ether” is some kind of physical light-speed regulating mechanism in space. It tends to regulate light speed to “c” near the surfaces of astronomical bodies, or to lower than “c” at the surfaces of massive bodies.
When light leaves a star that is moving away from the earth, the light leaves the star at about “c”, relative to the star, but at c – v relative to the earth, but by the time the light gets to the earth it is regulated to “c” at the earth and c + v away from and relative to the star that emitted it. Thus, it’s obvious that the light changes relative speed while in route.
Some of Einstein’s papers expressed his later point of view that the fields of astronomical bodies, specifically the gravity fields, might act as a local ether near the surfaces of the bodies.
Re: Re: Ether
Interesting in light of SR.
Do you know what a wave is?
Light is not like sound (the typical analogy). It does not require a medium upon which to propagate (as Hurkyl insinuated).
Whether or not you believe that statement to be true, again, its all about the evidence: Hundreds, if not thousands of experiments have hypothesized about the ether and attempted to find it - and all have failed. You cannot assume an ether exists, contrary to such a massive body of evidence.
David, quite simply, Einstein's "ether" from those quotes is not the same as the ether protonman is talking about. That is abundantly clear from the second quote. Einstein's ether is simply space-time and the fact that it has measurable properties. It is not an acutal medium in which light propagates like sound in air.
Definition of a wave
It is utterly impossible to talk about a wave without a medium of propagation.
Re: Definition of a wave
2. Prove it.
Re: Re: Re: Ether
Einstein changed his “constancy” postulate in his 1911 paper. Not very many people realize that because they just don’t understand the GR theory. After 1911, his light speed was regulated locally by the gravity fields through which it moved, at and near the surfaces of astronomical bodies.
Light could actually be “self propagating”. That is, it could be little wiggling electric and magnetic fields that move through space. Not a “wave” action inside pre-existing electric and magnetic fields, but actually a movement through space of tiny little wigging electric and magnetic fields that are emitted from an atom, and the little fields might move through space.
If this happens, then light does not need a medium in which to propagate. However, it has been proven that light speeds up slightly in deep space, away from strong fields, and it slows down slighly near the surfaces of astronomical bodies. So, the gravity fields near bodies and in deep space tend to have light-speed regulating properties. Thus, gravity could act like a kind of “ether”, something like a “medium” like glass, water, and air, something that slows down the little moving wiggling electric and magnetic fields as they travel through space. In strong gravity they slow down, and in weak gravity they speed up.
But the original “constancy” postulate of the 1905 theory was changed with his 1911 theory.
Einstein’s original 1905 postulate was based on the Lorentz 1895 theory that light always moved at “c” in empty space. But Einstein later realized that light speed slows down in a strong gravity field.
Get yourself a copy of the 1895 Lorentz book, and you will see where Einstein’s 1905 SR theory came from. It was not his original idea. It is actually modified version of the 1895 Lorentz book.
Re: Re: Definition of a wave
If you don't know then I suggest you study high school physics.
Physics is well beyond the stage of validating or even discussing about SR. It is not even a controversial matter any more among professional physicists.
This is NOT because of any conspiracy, or a desire to "maintain the status quo" (come on! the very idea is laughable), but because it is now firmly established (via experiment) and well understood.
Nowadays, relativistic corrections are used in myriads of experiments, and of course each one of them is first calibrated and tested with known magnitudes, to make sure that the gadget (or the 100 ton detector) measures things correctly. Any discrepancy would have been detected and studied long ago.
Due to the level of precision that current technology allows for experimental measurements, SR effects are extemely well tested. The current frontier of our knowledge is in a very different place.
Re: Re: Re: Re: Ether
I have read some of the history on SR and had heard the Lorentz was partially responsible from SR. Also, there is some speculation that Poinclare actually came up with a version of relativity using the same postulates as Einstein but before him. Either way, as it is presented it seems that Einstein suddenly came up with this idea all on his own which is unfortunate. Although this is mostly in the popular media and not so much in science texts.
I still think that based on the definition of a wave that you need a media and don't quite understand what you were saying about tiny electric and magnetic fields.
As I see it a wave is not something that exists independent of its medium of propagation. A wave is just a disturbance of that medium where each point moves up and down but there is no transverse displacement of particles.
Funny how no one has come up and tried to refute what you said. I notice that when they can't answer they ignore. When they address and you fight back they attempt to silence.
How about the Schwartz book on GR. Would you recomend it. I am very comfortable with SR although can't seem to find a good presentation of the covariant derivation and formulation of Maxwell's equations.
No, Lorentz theory and GR theory are well validated. What you are calling SR theory was invented by Lorentz in 1895. He invented “time dilation”, “length contraction”, mass increase due to motion, accelerative effects on oscillating atoms, a speed limit of “c”, atomic clock slowdowns. Einstein didn’t invent this stuff, he just modified the Lorentz theory in his 1905 paper. Einstein cultists attribute all this stuff to Einstein, but Lorentz actually invented it. I’ve got a copy of his rare 1895 book. Why do you think Einstein used the Lorentz Transformation equations in his SR paper? The Transformation equations were published in Lorentz’s 1895 book.
Ah, the self-proclaimed genius... Follow these simple steps to be your own self-procliamed genius!
(1) Go on a message board and profess to understand the subject better than the professionals who work in the field, because you aren't brainwashed by the orthodoxy (because academia is a giant corporate conspiracy to quell real knowledge and thinking).
(2) Be sure to only "publish" your revolutionary ideas on the web, because submitting them to journals is out of the question (the orthodoxy will not allow your theories to threaten the establishment).
(3) Always be sure to base your argument on a statement made in a paper which is at least 75 years old, but necessarily written by Einstein (or the father of the field in question). In doing so, you will immediately demonstrate the association of your ideas with those of the the paradigm-shifters.
(4) In light of (3), be careful to ignore any of the contradictory literature which was pubished in the years between then and now. It could serve to undermine your theory. Besides, the published results are clearly wrong.
(5) If you didn't mention it before, be sure to point out that you are a physics teacher, shaping the critical thinkers of tomorrow away from the poison of traditional academics. In the same paragraph in which you tout your pedagogical prowess, be sure to top it off with a grand-slam insult of your audience. Make 'em know who's the genius!
They said the same thing in Newton's time. Then again at the end of the 19th century when they thought they could explain all the forces in terms of gravity and E&M. No one to any reasonable degree has explained why the speed of light is constant to all observers...etc.
Did I say Einstein? No, I didn't. The point is that SR is extremely well tested.
Regarding authors, you have it wrong. Lorentz did indeed publish the transormation that have his name, but the interpretation he had for them was different from Einstein. That's a different discussion altogether.
The one person that almost got to what we call now SR, but didn't quite get there, was Poincare.
Most relativists are well aware of the origins of their field. I agree with you on one point, that Einstein receives too much "popular" credit for work which was not entirely his.
However, being as familiar with relativity as you are, I'm sure you realize the trivial typo you made by noting that mass increases with velocity... right?
Re: Re: Re: Re: Re: Ether
Here is a copy of a page from the 1895 Lorentz book, showing how he introduced the Lorentz transformation equations. In the old German text p = v and V = c.
Lorentz introduced time dilation on page 49 of that book.
So you would say that all experimental verifications of SR are just lucky coincidences? what about Quantum Field Theory and QED? (both of which are based on SR) do their fantastic accuracy also comes from sheer luck?
Separate names with a comma.