出典:Wiktionary
fine-structure constant (uncountable)
出典:Wikipedia
出典:『Wikipedia』 (2011/07/31 03:03 UTC 版)
In physics, the fine-structure constant (usually denoted α, the Greek letter alpha) is a fundamental physical constant, namely the coupling constant characterizing the strength of the electromagnetic interaction. The numerical value of α is the same in all systems of units, because α is a dimensionless quantity. Arnold Sommerfeld introduced the fine-structure constant in 1916.