In 2008, observations from the Very Large Telescope found that this quantity may have varied around 4 parts per million, though earlier, the Keck telescopes found it has changed by 6 parts per million. The first order anomalous magnetic dipole moment is approximately equal to this constant divided by two pi. This constant is squared in the Klein-Nishina formula, while the Lamb Shift depends on its fifth power. In cgs units, this constant is equal to the reciprocal of the quantity of the von Klitzing constant times the speed of light, making it easy to measure this with the Quantum Hall Effect. Corrections to the ratio of the spin and orbital 
In 2008, observations from the Very Large Telescope found that this quantity may have varied around 4 parts per million, though earlier, the Keck telescopes found it has changed by 6 parts per million. The first order anomalous magnetic dipole moment is approximately equal to this constant divided by two pi. This constant is squared in the Klein-Nishina formula, while the Lamb Shift depends on its fifth power. In cgs units, this constant is equal to the reciprocal of the quantity of the von Klitzing constant times the speed of light, making it easy to measure this with the Quantum Hall Effect. Corrections to the ratio of the spin and orbital angular momenta for an electron, or the Lande g-factor, use power series of this constant. It is the coupling constant for electromagnetic interactions. For 10 points, name this constant denoted alpha, which was mistakenly thought be exactly 1 over 137.
In 2008, observations from the Very Large Telescope found that this quantity may have varied around 4 parts per million, though earlier, the Keck telescopes found it has changed by 6 parts per million.
{fine}-{structure} constant [prompt on {alpha}]