Einstein and Lenard in Bad Nauheim

[Histspec]

After reading the Bad Nauheim debate (1920) between Albert Einstein and http://en.wikipedia.org/wiki/Philipp_Lenard" , there are three critical points raised by Lenard against relativity (see also the following descriptions of the debate by Hermann Weyl, Gehrcke, Körner):

http://en.wikisource.org/wiki/The_Bad_Nauheim_Debate

a) That for every physical process there must be a corresponding explanation in the aether, that is, there must be an "illustrative" explanation by "images of the second kind", as opposed to mathematical explanations by images of the "first kind".

b) Only forces that are produced by masses can exist, but not the fictitious gravitational forces in the accelerated frames of general relativity. Therefore, in the case of a decelerating train, it is in fact the train that accelerates, not the environment.

c) That in rotating frames the speed of light is not constant, for example, when the Earth is considered at rest, than the universe is rotating - especially at its rim - with superluminal velocity.

Einstein's response:
a) What we call "illustrative" or "common sense" has changed in time, and therefore it cannot be regarded as a criterion of the theory's correctness.

b) He argues that the "fictitious" gravitational forces in accelerated frames are the products of the "distant masses". (Einstein evidently was alluding to Mach's principle.)

c) He says that in rotating frames the speed of light is indeed not constant, but this is no problem as in general relativity other rules for the speed of light apply than for special relativity.

It's notable, that Lenard (who never understood relativity) became a member of the Nazi party, and was the founder of the racist http://en.wikipedia.org/wiki/Deutsche_Physik" .

Regards,

 

[hkyriazi]

I'm wondering if there was a mistake in translation, or if Lenard simply misspoke here: "For example, Mr. Weyl spoke in terms of images of the first kind, as he expressed all processes by equations. By images of the second kind, the equations can be interpreted as processes in space."

I suspect he meant to say "...as he expressed all phenomena by equations" [rather than "processes"]. The whole idea, if I understand the debate correctly, was that "images of the first kind" were highly abstract, with no process in mind at all, whereas images of the 2nd kind were mathematical descriptions of real, ongoing processes (interactions of lots of tiny, visualizable objects). But the way it is translated here seems to make images of the 1st kind the same as those of the 2nd kind (both being expressions of processes).

 

[A.T.]

there are three critical points

The first is philosophical, the other two would apply to Newtonian physics as well (inertial vs. non-inertial frames) and it's not clear what the problem is.

 

[vanhees71]

I hope, we won't discuss Lenard's idiosyncrasic ideas on PF. It's one of the sadest examples of a great scientist becoming completely off the scientific track in his later years. It's also an example for being careful with "anti-mathematicians" ;-).

 

[hkyriazi]

Any thoughts on whether the translation was bungled, or if he (Lenard) misspoke?

 

[Nugatory]

Any thoughts on whether the translation was bungled, or if he (Lenard) misspoke?

I'm not sure that question is meaningful; an imprecise thought cannot be precisely translated. Conversely, with Einstein's prose it's often hard to tell whether you're reading English that he wrote himself or a good translation from German; either way it's striking for its precision.

 

[hkyriazi]

I'd like to get a transcript of the original German, and have some German-speaking scientists I know translate it. But, it seems no such transcription exists.

I believe Lenard was expressing a thought along the lines of what had long been argued by the likes of Lord Kelvin and Ludwig Boltzmann - that one cannot be said to understand something unless one is able to make a model of it in one's mind (a model of the interactions of 3D objects), and against the view of those who scoffed at the mechanical worldview, such as Pierre Duhem (a vehement energeticist and devout Catholic, who thought such deep speculations were inappropriate for science, and the realm of theology). Duhem detested the 19th century British habit of model-building, despite its great success with Maxwell and company. Duhem was quite influential with Einstein and others of his era.

Basically, though, I think the distinction is between totally abstract mathematics (unvisualizable) and mathematics that describes the workings of a visualizable process.

 

[Dale]

there are three critical points

These are "critical points" in the sense that he is critical of relativity and these are his points. They are not "critical points" in the sense of a point of failure that is critical for the structural integrity of the theory. Basically, I think all three can be accepted without in the least contradicting the theory.

 

[A.T.]

I believe Lenard was expressing a thought along the lines of what had long been argued by the likes of Lord Kelvin and Ludwig Boltzmann - that one cannot be said to understand something unless one is able to make a model of it in one's mind (a model of the interactions of 3D objects), and against the view of those who scoffed at the mechanical worldview, such as Pierre Duhem (a vehement energeticist and devout Catholic, who thought such deep speculations were inappropriate for science, and the realm of theology).

Both views are wrong. The ability to visualise a theory well is neither necessary nor inappropriate for science.