Fine-structure constant (nonfiction): Difference between revisions
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In physics, the '''fine-structure constant''', also known as '''Sommerfeld's constant''', commonly denoted by α (the Greek letter alpha), is a fundamental physical constant characterizing the strength of the electromagnetic interaction between elementary charged particles. It is a dimensionless quantity related to the elementary charge e, which characterizes the strength of the coupling of an elementary charged particle with the electromagnetic field, by the formula 4πε0ħcα = e2. As a dimensionless quantity, its numerical value, approximately | In physics, the '''fine-structure constant''', also known as '''Sommerfeld's constant''', commonly denoted by α (the Greek letter alpha), is a fundamental physical constant characterizing the strength of the electromagnetic interaction between elementary charged particles. It is a dimensionless quantity related to the elementary charge e, which characterizes the strength of the coupling of an elementary charged particle with the electromagnetic field, by the formula 4πε0ħcα = e2. As a dimensionless quantity, its numerical value, approximately 1/137, is independent of the system of units used. | ||
While there are multiple physical interpretations for α, it received its name from [[Arnold Sommerfeld (nonfiction)|Arnold Sommerfeld]] introducing it (1916) in extending the [[Bohr model (nonfiction)|Bohr model]] of the atom: α quantifies the gap in the fine structure of the spectral lines of the hydrogen atom, which had been precisely measured by [[Albert A. Michelson (nonfiction)|Albert Michelson]] and [[Edward W. Morley (nonfiction)|Edward Morley]]. | |||
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== Recent findings == | |||
Improved technology at the dawn of the 21st century made it possible to probe the value of α at much larger distances and to a much greater accuracy. In 1999, a team led by [[John K. Webb (nonfiction)|John Webb]] of the University of New South Wales claimed the first detection of a variation in α. Using the Keck telescopes and a data set of 128 quasars at redshifts 0.5 < z < 3, Webb et al. found that their spectra were consistent with a slight increase in α over the last 10–12 billion years. Specifically, they found that TO_DO: math. | |||
In other words, they measured the value to be somewhere between −0.0000047 and −0.0000067. This is a very small value, nearly zero, but their error bars do not actually include zero. This result either indicates that α is not constant or that there is experimental error that the experimenters did not know how to measure. | |||
== Links == | == Links == | ||
* [https://en.wikipedia.org/wiki/Fine-structure_constant Fine-structure constant] @ Wikipedia | * [https://en.wikipedia.org/wiki/Fine-structure_constant Fine-structure constant] @ Wikipedia | ||
* [[Diary_(May_4,_2020)#Cosmic_Uncertainty]] | |||
Latest revision as of 09:44, 4 May 2020
In physics, the fine-structure constant, also known as Sommerfeld's constant, commonly denoted by α (the Greek letter alpha), is a fundamental physical constant characterizing the strength of the electromagnetic interaction between elementary charged particles. It is a dimensionless quantity related to the elementary charge e, which characterizes the strength of the coupling of an elementary charged particle with the electromagnetic field, by the formula 4πε0ħcα = e2. As a dimensionless quantity, its numerical value, approximately 1/137, is independent of the system of units used.
While there are multiple physical interpretations for α, it received its name from Arnold Sommerfeld introducing it (1916) in extending the Bohr model of the atom: α quantifies the gap in the fine structure of the spectral lines of the hydrogen atom, which had been precisely measured by Albert Michelson and Edward Morley.
Recent findings
Improved technology at the dawn of the 21st century made it possible to probe the value of α at much larger distances and to a much greater accuracy. In 1999, a team led by John Webb of the University of New South Wales claimed the first detection of a variation in α. Using the Keck telescopes and a data set of 128 quasars at redshifts 0.5 < z < 3, Webb et al. found that their spectra were consistent with a slight increase in α over the last 10–12 billion years. Specifically, they found that TO_DO: math.
In other words, they measured the value to be somewhere between −0.0000047 and −0.0000067. This is a very small value, nearly zero, but their error bars do not actually include zero. This result either indicates that α is not constant or that there is experimental error that the experimenters did not know how to measure.