# What is the fine structure constant

## Fine Structure Constant Quotes (74 quotes)

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Physicists measure the values of basic quantities like the speed of light and the charge of the electron. Cosmologists use the results in studies of the origin of the universe, some 12 billion years ago, and they assume the numbers have not changed over this time. But now comes a result that could stand this assumption on its head. Admittedly, the increase is only one part in ,pretty small-but that's enough to be plenty unsettling. Alpha specifies how strongly electromagnetic waves like light or x-rays affect charged particles like electrons and protons. Alpha is actually a dimensionless ratio-all units cancel out-involving three quantities:. The idea that one or more of these quantities changes over time is generally most unappealing, although a few theories actually have suggested that it might happen.

Does the Universe around us have a fundamental structure that can be glimpsed through special numbers? The brilliant physicist Richard Feynman famously thought so, saying there is a number that all theoretical physicists of worth should "worry about". He called it "one of the greatest damn mysteries of physics: a magic number that comes to us with no understanding by man". What's special about alpha is that it's regarded as the best example of a pure number, one that doesn't need units. It actually combines three of nature's fundamental constants - the speed of light, the electric charge carried by one electron, and the Planck's constant, as explains physicist and astrobiologist Paul Davies to Cosmos magazine.

Current advances: The fine-structure constant and quantum Hall effect. It is the "coupling constant" or measure of the strength of the electromagnetic force that governs how electrically charged elementary particles e. Sommerfeld in and in the past has often been referred to as the Sommerfeld fine-structure constant. In order to explain the observed splitting or fine structure of the energy levels of the hydrogen atom, Sommerfeld extended the Bohr theory to include elliptical orbits and the relativistic dependence of mass on velocity. Sommerfeld's theory had some early success in explaining experimental observations but could not accommodate the discovery of electron spin. Consequently, the name "fine-structure" constant for the group of constants below has remained:. Our view of the fine-structure constant has changed markedly since Sommerfeld introduced it over 80 years ago.

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The each s orbital red , each of the p orbitals yellow , the d orbitals blue and the f orbitals green can contain only two electrons apiece: one spin up and one spin down in each one., By using our site, you acknowledge that you have read and understand our Cookie Policy , Privacy Policy , and our Terms of Service.

It is one of the most important of our system of fundamental constants. Powers of the fine structure constant times the rest energy of the electron give the size of the various transition energies in atoms. This fundamental constant also determines the Josephson effect and the quantum Hall effect in condensed matter physics. The experimental uncertainty is 0. This determination of the fine structure constant is 12 and 20 times more accurate than are the next most accurate independent determinations Rb and Cs The small corrections labeled as a x with various subscripts are small corrections that are believed to be well-understood within the standard model of particle physics. In a recent review we tabulate the best values for these constants and the calculations from which they came.

Then the expression of the fine-structure constant, as commonly found in older physics literature, becomes. This has a relative standard uncertainty of 0. For reasons of convenience, historically the value of the reciprocal of the fine-structure constant is often specified. This value and uncertainty are about the same as the latest experimental results. On the other hand, the large value of the corresponding factors in quantum chromodynamics makes calculations involving the strong nuclear force extremely difficult. In quantum electrodynamics , the more thorough quantum field theory underlying the electromagnetic coupling, the renormalization group dictates how the strength of the electromagnetic interaction grows logarithmically as the relevant energy scale increases.

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atomic physics - Where does the fine structure constant come from? - Physics Stack Exchange