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 <[email protected]
> <javascript:>> wrote:
>
>> On Wed, Jan 9, 2019 at 5:01 PM Bruce Kellett <[email protected]
>> <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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