Re: gEDA-user: smd challenge board status

[Steve Meier <smeier@xxxxxxxxxxxxxxxxxxx>]

Bill,

Thanks for the reference.

Steve M.

On Wed, 2006-11-01 at 16:40 +0100, Bill Sloman wrote:
> At 05:25 1-11-2006, you wrote:
> >I think I will drop into this group a brief passage fom Heisenberg's
> >"Quantum Theory" translated into English in 1930.
> >
> >"Dirac has set up a wave equation which is valid for one electron and is
> >invarient under the Lorentian transformation. It fulfills all
> >requirements of the quantum theory, and is able to give a good account
> >of the phenomena of the "spinning" electron, which could previously only
> >be treated by, ad hoc assumptions. The essential difficulty which arises
> >with all relativistic quantum theories is not eliminated however. This
> >arises from the relation
> >
> >1/c^2 = u^2C^2  + p^2 in x + p^2 in y + p^2 in z
> >
> >between the energy and the momentum of a free electron. According to
> >this equation there are two values of E which differ in sign associated
> >with each set of P in z, P in  y and P in Z. The classical theory could
> >eliminate this by arbitrarily excluding the one sign, but this is not
> >possible according to the  principles og quantum theory. Here
> >spontaneuos transitions may occure to the states of negative energy; as
> >these have never been observed, the theory is certainly wrong. Under
> >these conditions it is very remarkable that the positive energy-levels
> >(at least in the case of one electron) coincide with those actually
> >observed."
> >
> >So what was wrong? What occured that proved both theories were correct?
> 
> Dirac solved the problem by hypothesising the positron,
> 
> http://www.siam.org/siamnews/03-03/dirac.pdf
> 
> which was then sought and found by the experimental physicist Carl 
> David Anderson in 1932
> 
> http://en.wikipedia.org/wiki/Carl_D._Anderson
> 
> It is one of the nicer stories from the early days of quantum physics.
> 
> Dirac's normal interaction with experimental physicists is described 
> by the Dirac Effect - which, in the classic version of the story - 
> had Dirac's presence in Cologne (sitting in a stationary train for a 
> couple of hours) as a necessary and sufficient explanation for a 
> couple of hours of temperamental behaviour by a sensitive quadrant 
> electrometer.
> 
> Bill Sloman, Nijmegen
> 
> 
> 
> 
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