Einstein: Concerning the Aether

[Rasalhague]

I first learned of this paper in a FAQ by Benjamin Crowell which gave a link to Einstein's handwritten manuscript, but no English translation, so I had a go at making http://www.oe.eclipse.co.uk/nom/aether.htm . Some of the physics is above my head, especially the stuff on radiation and magnetism towards the end and in the 2nd footnote, so all advice welcome, linguistic or physics-related. I've linked to two other sites where the original can be read more conveniently:

Digitised German text: Wikilivres

Scans of German text as published:
SEALS (Swiss Electronic Academic Library Service): Retrodigitized Journals

 

[turbo]

The paper was previously translated by Saunders, and is Chapter One in "The Philosophy of Vacuum" by Saunders and Brown. The book is quite pricey, but you can find clean used copies pretty reasonably.

 

[bcrowell]

Cool! Thanks, Rasalhague, for making your translation publicly available!

Please consider dedicating it to the public domain or putting it under a license such as CC-BY or CC-BY-SA that would allow it to be saved permanently on wikisource ( http://en.wikisource.org/wiki/Author:Albert_Einstein ) and reused freely by others.

In case anyone is interested, here is the FAQ that Rasalhague referred to:

Didn't Einstein say that general relativity was an aether theory?

No. Einstein wrote a 1924 paper in which he made the philosophical point that although relativity killed off the luminiferous aether as the supposed medium of electromagnetic vibrations, it still imbued the vacuum with specific physical characteristics, such as curvature and energy. The basic point of the paper is that we can't decide, purely based on philophical ideas like Mach's principle, whether the vacuum has its own properties; we actually have to go through the usual scientific cycle of theory and experiment in order to find out the answer. Internet kooks love to misinterpret and overinterpret this paper, or to misrepresent it by saying that Einstein referred to GR in general, throughout his career, as an aether theory.

A. Einstein, "Über den Äther," Schweizerische naturforschende Gesellschaft 105 (1924) 85
original text - http://www.wikilivres.info/wiki/Über_den_Äther
English translation - http://www.oe.eclipse.co.uk/nom/aether.htm
commentary by John Baez - http://web.archive.org/web/20070204022629/http://math.ucr.edu/home/baez/RelWWW/wrong.html

 

[Rasalhague]

You're welcome! And thanks for all material you've put online that's made my world so much more intersting of late. I certainly have no objection to anyone copying, sharing or, if need be, improving on my translation. I've just added a note to that effect.

 

[Mentz114]

Rasalhague, nice job. I look forward to reading it again.

 

[turbo]

I just took the time to read through your translation and Saunders' translation side-by-side, and they are quite consistent, varying primarily in nomenclature as opposed to substance. Good job!

 

[Rasalhague]

Thanks, turbo-1. That's a relief!

 

[Saw]

I am also amazed by the quality of the job, Rasalhague. If there was another translation, better for us, thus we can compare, but for sure the fact that yours was uncontaminated by the previous one is an advantage of it, it endows your work with more added value.

On the other hand, as to the contents of the paper, I am even more amazed at the fact that some people can interpret it in the sense that Einstein declared that there was no aether. Here, like in the 1920 lecture at the university of Leyden (http://www.tu-harburg.de/rzt/rzt/it/Ether.html ), he makes it clear that, in his opinion, "some aether" that is "physically real" is a logical necessity to sustain the propagation of EM waves. Ok, he also claims that this aether is not mechanical, it is quite different from ponderable matter, as opposed to the air-sound analogy prevailing in the XIXth century; furthermore, he also claims that this aether, unlike Lorentz's, is deprived not also of mobility (it cannot be dragged) but also of immutability (since it is affected by the presence of ponderable matter). But existing..., of course it does exist, he says. Or not?

 

[turbo]

Ok, he also claims that this aether is not mechanical, it is quite different from ponderable matter, as opposed to the air-sound analogy prevailing in the XIXth century; furthermore, he also claims that this aether, unlike Lorentz's, is deprived not also of mobility (it cannot be dragged) but also of immutability (since it is affected by the presence of ponderable matter). But existing..., of course it does exist, he says. Or not?

Einstein said:

The ether of general theory of relativity therefore differs from that of classical mechanics or the special theory of relativity respectively, in so far as it is not 'absolute', but is determined in its locally variable properties by ponderable matter.

He specifically claimed that "empty space" had properties that were conditioned by the presence of mass and energy. Lately, Thanu Padmahnaban has toyed with an ether model, but his model is hampered, IMO, because he claims that the ether is an immutable entity, such as the Lorentz model that you cite. Such an ether might allow the development of a kinetic model of quantum gravity, but certainly not a dynamic one. Einstein's view was that the ether of GR was not a background against which gravitational and inertial effects play out passively, but is itself a player in the emergence of such effects.

 

[Rasalhague]

How does Saunders treat the equation in note 2? Out of ignorance, I played safe and left it as it appears in the German, complete with fraktur letters:

$$d\mathfrak{h} = -C \, dm \, \frac{\left [ \mathfrak{v},\mathfrak{r} \right ]}{r^3}$$

But I was wondering whether it would be correct, and clearer, to replace $\left [ \mathfrak{v},\mathfrak{r} \right ]$ with $\textbf{v} \times \textbf{r}$ by analogy with

$$\textbf{B} = C q \frac{\textbf{v} \times \textbf{r}}{r^3}$$

 

[Saw]

Einstein's view was that the ether of GR was not a background against which gravitational and inertial effects play out passively, but is itself a player in the emergence of such effects.

Yes, that is true. It is reciprocal: Einstein's ether is affected and it affects, too. But the point of my comment was not so much dwelling on the various features of Einstein's ether, but only remarking that it does exist, in his opinion!

Of course, you can call it "empty space" if you wish, as long as you admit it has properties. But if you admit it has properties, if you admit that it is "something" that interacts with mass and energy, what is the point of calling it with a name that suggests that it is "nothing"?

In any case, clearly that was not Einstein's intention. He never claimed that the ether is "nothing". Do you agree to that?

 

[turbo]

In any case, clearly that was not Einstein's intention. He never claimed that the ether is "nothing". Do you agree to that?

I certainly agree that that was Einstein's intent. It is clear that he thought that the ether is a dynamic player in the emergence of gravitational and inertial effects.

 

[JesseM]

Yes, that is true. It is reciprocal: Einstein's ether is affected and it affects, too. But the point of my comment was not so much dwelling on the various features of Einstein's ether, but only remarking that it does exist, in his opinion!

It's really just a matter of semantics, but I'd say the major difference between Einstein's "ether" and the classical ether was that the classical version was an actual physical medium, so at any point in spacetime an object would either be at rest relative to the local ether or in motion relative to it, whereas there'd be no way to assign meaning to the idea of being locally at rest or in motion relative to Einstein's ether.

 

[granpa]

Many people may not realize that the classical aether could not have been a simple elastic.
In fact it would have needed pretty miraculous properties to
explain the behavior of classical electric, magnetic, or gravitational fields

 

[Saw]

I certainly agree that that was Einstein's intent. It is clear that he thought that the ether is a dynamic player in the emergence of gravitational and inertial effects.

I thought so, thanks for confirming.

It's really just a matter of semantics, but I'd say the major difference between Einstein's "ether" and the classical ether was that the classical version was an actual physical medium, so at any point in spacetime an object would either be at rest relative to the local ether or in motion relative to it, whereas there'd be no way to assign meaning to the idea of being locally at rest or in motion relative to Einstein's ether.

Well, as usual, I would not say it is “just” semantics if it has practical consequences. A better definition of a concept should enable us to make better predictions. For example, what you say about the difference between classical ether and Einstein’s ether is not irrelevant in practical terms. What Granpa says in the next post goes in the same line.

A different thing is which definition should we adhere to. What you point out is probably correct. It is impossible to measure a state of motion wrt the ether. It is no medium, like water or air, composed of parts of ponderable matter. But would you say it is not “physical”? Yes, thus we go into the ugly problem of defining what is physical, which is usually quite subjective. But if we choose to define “physical” as something that interacts with other physical things, would you agre that Einstein’s ether is physical?

 

[JesseM]

Well, as usual, I would not say it is “just” semantics if it has practical consequences.

Whether we use the word "ether" to describe the dynamical properties of spacetime in GR (as defined by the Einstein field equations) doesn't have any practical consequences that I can see.

A better definition of a concept should enable us to make better predictions.

Word definitions aren't really important in physics, it's all about the mathematical definitions. If one person uses the word "ether" to describe GR spacetime but the other doesn't, yet they both use the same equations to describe how mass/energy curves spacetime and what paths objects take through curved spacetime, they will make exactly the same predictions.

But if we choose to define “physical” as something that interacts with other physical things, would you agre that Einstein’s ether is physical?

This verbal definition still seems too ambiguous--for example, you could see spacetime as just part of a quantitative description of how different bits of mass/energy interact with one another gravitationally (similarly, is a 'force' in Newtonian physics a 'something' that 'interacts with' objects, or just part of our mathematical description of the rules of how objects interact with one another?)

 

[Austin0]

Yes, that is true. It is reciprocal: Einstein's ether is affected and it affects, too. But the point of my comment was not so much dwelling on the various features of Einstein's ether, but only remarking that it does exist, in his opinion!

Of course, you can call it "empty space" if you wish, as long as you admit it has properties. But if you admit it has properties, if you admit that it is "something" that interacts with mass and energy, what is the point of calling it with a name that suggests that it is "nothing"?

In any case, clearly that was not Einstein's intention. He never claimed that the ether is "nothing". Do you agree to that?

Hi saw Well I definitely agree with your interpretation.
His words seem clear and unambiguous in conceptual physical terms.
Spacetime may be purely emergent from the existence of matter yet still has properties , seemed to be the essence of his point.
I also saw no distinction being made between areas of relative concentration of matter.

The semantic ambiguity seems to arise through interpretation, whereby through suitable definition, the essential meaning somehow disappears entirely into the aether.

 

[Saw]

Whether we use the word "ether" to describe the dynamical properties of spacetime in GR (as defined by the Einstein field equations) doesn't have any practical consequences that I can see.

Word definitions aren't really important in physics, it's all about the mathematical definitions. If one person uses the word "ether" to describe GR spacetime but the other doesn't, yet they both use the same equations to describe how mass/energy curves spacetime and what paths objects take through curved spacetime, they will make exactly the same predictions.

This verbal definition still seems too ambiguous--for example, you could see spacetime as just part of a quantitative description of how different bits of mass/energy interact with one another gravitationally (similarly, is a 'force' in Newtonian physics a 'something' that 'interacts with' objects, or just part of our mathematical description of the rules of how objects interact with one another?)

Starting with the last point, I agree that in physics (and probably in all fields of knowledge) you do not really describe the objects themselves but only how they interact with one another. In this sense, you mentioned the concept of “force”, but you could have also referred to “mass”. Actually, the “mass” is not the object itself but the outcome of a competition between the same and another standard reference of similar kind, in terms of resistance to acceleration, given an interaction with a common challenge . The object itself is a piece of “matter”. Certainly, we don’t plug “matter” into the equations, only mass or other properties. However, we didn´t get rid of the concept of “matter”. Likewise, I do not see why we should dispense with the word “ether”. (Or maybe we should trascend both concepts, I don’t know…)

Spacetime (...) still has properties , seemed to be the essence of his point.

Yes, that is valid way to put it. But I still I find that it is advisable to distinguish, as a question of mental order, between the objects themselves and, as you mention, spacetime, i.e. a drawing representing the readings of clock and rulers placed along the path of an object.

Practical consequences? Better predictions? In my view, the problem of speaking only about spacetime is that then some people tend to think that this spacetime is “the object itself”, the ultimate answer to the why question and that leads to making absurd predictions or at least to accepting absurd possibilities, like time travel, but that is a subject for another thread. I do not want to high-jack this one, which was about the translation of Einstein’s paper and there was a new question by the OP:

How does Saunders treat the equation in note 2? Out of ignorance, I played safe and left it as it appears in the German, complete with fraktur letters:

$$d\mathfrak{h} = -C \, dm \, \frac{\left [ \mathfrak{v},\mathfrak{r} \right ]}{r^3}$$

But I was wondering whether it would be correct, and clearer, to replace $\left [ \mathfrak{v},\mathfrak{r} \right ]$ with $\textbf{v} \times \textbf{r}$ by analogy with

$$\textbf{B} = C q \frac{\textbf{v} \times \textbf{r}}{r^3}$$

 

[Rasalhague]

Thanks for resurrecting my question, Saw. I found it on Google books:

http://books.google.com/books?id=ZU...ce=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

It does indeed use bold Roman letters and the familiar cross product notation. I've changed mine accordingly. I also corrected a mistake I made in translating grössenordnung as "dimensional analysis" whereas it should have been "order of magnitude". I also followed Saunders' lead with the word "eigenvibrations", a technical term I didn't know, not having studied quantum mechanics.

 

[inflector]

Many people may not realize that the classical aether could not have been a simple elastic.
In fact it would have needed pretty miraculous properties to
explain the behavior of classical electric, magnetic, or gravitational fields

I've seen this stated elsewhere. Can you elaborate on this further?

What magical properties would it have to have and why?

 

[inflector]

I first learned of this paper in a FAQ by Benjamin Crowell which gave a link to Einstein's handwritten manuscript, but no English translation, so I had a go at making http://www.oe.eclipse.co.uk/nom/aether.htm .

Thank you for the translation. Very interesting.