The Number That Defines the Universe

That's how it has been described in the press, for the most part. I'm not sure the Fine-structure Constant qualifies as the answer to "Life, the Universe, and Everything," but it is a good stand-in.

An important result in Physics was published at the beginning of December, but like so many people I was distracted. Physicists Nail Down the ‘Magic Number’ That Shapes the Universe

First a bit about the Fine-structure Constant.

As fundamental constants go, the speed of light, c, enjoys all the fame, yet c’s numerical value says nothing about nature; it differs depending on whether it’s measured in meters per second or miles per hour. The fine-structure constant, by contrast, has no dimensions or units. It’s a pure number that shapes the universe to an astonishing degree — “a magic number that comes to us with no understanding,” as Richard Feynman described it. Paul Dirac considered the origin of the number “the most fundamental unsolved problem of physics.”

The fine-structure constant, usually denoted as the Greek letter alpha, or α, describes the strength of the coupling between a charged particle, and a magnetic field. It has no units, so it is the same whether you are working in the International Units (or the metric system) or imperial measures (miles per hour, etc.). It is approximately 1/137. The research paper gives the best estimate yet of its actual value.

The fine-structure constant determines the strength of the electromagnetic force, and is central in explaining a number of phenomena including the interactions between light and charged elementary particles such as electrons. It is an important part of the equations of the Standard Model, a theory that predicts and describes all the known fundamental forces other than gravity—namely electromagnetism as well as the weak and strong nuclear forces.

Saïda Guellati-Khélifa and her team at the Kastler Brossel Laboratory in Paris have produced the best approximation to date.

The team measured the constant’s value to the 11th decimal place, reporting that α = 1/137.035999206.

With a margin of error of just 81 parts per trillion, the new measurement is nearly three times more precise than the previous best measurement in 2018