Fine-structure constant: Difference between revisions

Revision as of 16:56, 10 January 2025

Revision as of 19:34, 10 January 2025

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{{Quantum field theory}}

In [[physics]], the '''fine-structure constant''', also known as the '''Sommerfeld constant''', commonly denoted by {{mvar|α}} (the [[Alpha|Greek letter ''alpha'']]), is a [[Dimensionless physical constant|fundamental physical constant]] whichthat quantifies the strength of the [[electromagnetic interaction]] between elementary charged particles.

It is a [[dimensionless quantity]] ([[dimensionless physical constant]]), independent of the [[system of units]] used, which is related to the strength of the coupling of an [[elementary charge]] ''e'' with the [[electromagnetic field]], by the formula {{math|1=4''πε''{{sub|0}}''ħcα'' = ''e''{{sup|2}}}}. Its [[numerical value]] is approximately {{nowrap|{{physconst|alpha|round=13|ref=no}} ≈ {{sfrac|{{physconst|alphainv|round=9|ref=no}}}}}}, with a relative uncertainty of {{physconst|alpha|after=.|runc=yes}}