sci.physics.electromag

On Sun, 16 Mar 2008, Vince Morgan wrote:

> "Szczepan Bialek" wrote:
>> And what do you think about such like this:
>> http://bourabai.narod.ru/inertia-e.htm

Ugh! Bad English - makes it hard to read. At first read, it looks like
somebody wants to regress physics by about 400 years. At second read (not
this late at night!), perhaps there will be a second opinion.

> However, "for example, the photon, having inertia (momentum and moment of
> momentum(inertia?)) has no gravitational mass" has always struck me as
> ludicrous. A little "I can't understand this so I must be damaged" has
> helped me cope somewhat. Seeing that I am not alone in my damaged state is
> comforting.
[cut]
> "Actually inertia, as it was shown by Nikolay Umov [11,12], is an effect of
> a causality, continuity of process of transmission of momentum and energy in
> a material medium without dependence from a concrete nature of a material."
> makes absolute sense to me.

Umov's papers are quite worthwhile reading. Alas, I don't know of any
English translation, and I have to read the Russian reprints. Since I
don't read/speak Russian, this is painful - it takes me a day or so to get
up to speed with Cyrillic alphabet.

But the heart of Umov's contribution, c. 1874 iirc, is that energy has
inertia. If you're moving energy around, as, e.g., waves, whether
mechanical waves or thermal waves or whatever, an energy flux of E
requires a momentum flux of E/v. If you can do work on something distant,
you must be able to apply a force, and change its momentum. ("Moment of
momentum is "angular momentum".) Inertia of photons (or electromagnetic
waves, if you want to be non-quantised classical) follows as a result. The
truly cool thing is that Maxwell's formula for radiation pressure agrees
exactly with Umov, despite their fundamentally different origins.

Possibly even more odd is that Umov's result is in complete agreement with
special relativity, providing the reconciliation between light as
particulate photons and light as waves.

--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html