On Wednesday, January 9, 2019 at 6:49:05 PM UTC-6, Bruce wrote:
> On Thu, Jan 10, 2019 at 11:38 AM John Clark <johnk...@gmail.com 
> <javascript:>> wrote:
>> On Wed, Jan 9, 2019 at 5:01 PM Bruce Kellett <bhkel...@gmail.com 
>> <javascript:>> wrote:
>> *> Rubbish. The fine structure constant is not computable by Feynman 
>>> diagrams. What might be confusing you is that QED calculations of 
>>> physically measurable  things like the Lamb Shift and g-2 for the electron 
>>> depend on the value of the FSC.*
>> How is using Feynman diagrams to compute the Lamb Shift Shift (which 
>> depends on the Fine Structure Constant) different from using Feynman 
>> diagrams to compute the Fine Structure Constant?  After all physics 
>> didn't determine the Lamb Shift from the Fine Structure Constant, they 
>> determined the Fine Structure Constant by looking at the Lamb Shift, in 
>> fact the very very fine lines in the spectrum of Hydrogen is how the Fine 
>> Structure Constant got its name. 
>> The following 2012 article in Physical Review letters describes a QED 
>> calculation involving 12,672 tenth order Feynman diagrams used to 
>> calculate both the magnetic moment of the electron and the inverse of the 
>> Fine Structure Constant and obtaining a value of 137.035999173 which is 
>> almost exactly the same as the experimentally derived value:
> That is an experimentally derived value!!!!!
>> Improved Value of the Fine Structure Constant 
>> <https://arxiv.org/abs/1205.5368>   
>> John K Clark
> Your original claim was that the fine structure constant was computable. 
> But it is not computable from first principles, it is a physical constant 
> that must be measured. The fact that computations might be involved in 
> getting the value from measurements does not mean that the FSC is itself 
> computable.
> You have to define what you mean by "computable". The FSC is a measured 
> quantity, not computable in the way pi or e are computable from 
> mathematical formulae.
> Bruce 

Constants enter the vocabulary of physics by means of theories. *A constant 
is an entity of a theory,* but a constant is not an entity of nature. 
Nature may have *constancy*, but it's theories that have constants. 

           *Theory != Nature. *

- pt

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