Neeum Zawan wrote:
> Could be - I never studied QED. However, it's not plain old
> electromagnetics. 

OK. I don't know the difference between QED and electromagnetics. I thought 
"electromagnetic" was the pre-quantum formulation of electrical and magnetic 
field interactions, i.e., the interaction of electrons with photons.

 > What Dyson showed was that the electromagnetic
> interactions between/among nuclei and electrons is not sufficient to
> explain the volume of matter - it would be smaller without the exclusion
> principle. 

That seems obvious to me. :-) Clearly I'm not educated enough to understand 
why that's surprising.

> One aspect that keeps particles apart is the exchange interaction, which
> is purely due to quantum mechanics (i.e. not, AFAIK, related to
> electromagnetics). This was one of those oddities of the quantum world
> in undergrad quantum mechanics - that two such particles would prefer to
> stay apart even though there is no actual force interaction between them
> (even for uncharged particles). 

I understand the math of why they try to stay apart. I'll have to re-read 
the bit that talks about that and see if I can understand what leads to the 
math.

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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