# Why the number 137 is one of the greatest mysteries in physics

The fine structure constant has mystified scientists since the 1800s. The number 1/137 might hold the clues to the Grand Unified Theory. The number connects relativity, electromagnetism, and quantum mechanics.

Is there a fundamental structure to the Universe that can be seen through special numbers?

The brilliant physicist Richard Feynman (1918-1988) 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”.

That magic number, known as the fine structure constant, is a fundamental constant with a value close to 1/137, or 1/137.03599913 to be precise. It is denoted by the Greek letter alpha – α.

What makes alpha unique is that it is regarded as the best example of a pure number, one that does not need units. According to physicist and astrobiologist Paul Davies in Cosmos magazine, it combines three of nature’s fundamental constants: the speed of light, the electric charge carried by one electron, and the Planck’s constant. 1/137’s allure comes from its appearance at the intersection of key fields of physics such as relativity, electromagnetism, and quantum mechanics.

Laurence Eaves, a physicist at the University of Nottingham, believes that the number 137 would be sent to aliens to indicate that we have some control over our planet and understand quantum mechanics. The aliens would also be aware of the number, especially if they acquired advanced sciences.

The number preoccupied other great physicists as well, including the Nobel Prize winning Wolfgang Pauli (1900-1958) who was obsessed with it his whole life.

“When I die my first question to the Devil will be: What is the meaning of the fine structure constant?” Pauli joked.

Pauli also referred to the fine structure constant during his Nobel lecture on December 13th, 1946 in Stockholm, saying a theory was necessary that would determine the constant’s value and “thus explain the atomistic structure of electricity, which is such an essential quality of all atomic sources of electric fields actually occurring in nature.”

This odd number can be used to measure the interaction of charged particles like electrons with electromagnetic fields. Alpha determines how fast an excited atom can emit a photon. It also has an impact on the specifics of the light emitted by atoms. Scientists have discovered a pattern of light shifts produced by atoms known as “fine structure” (giving the constant its name). This “fine structure” has been seen in sunlight and the light coming from other stars.

The constant figures in other situations, making physicists wonder why. What is the significance of this number in nature? Since the 1880s, it has appeared in many physics calculations, sparking numerous attempts to develop a Grand Unified Theory that would incorporate the constant. So far no single explanation has taken hold. Recent research also introduced the possibility that the constant has actually increased over the last six billion years, even though slightly.

If you’d like to know the math behind fine structure constant more specifically, the way you arrive at alpha is by putting the 3 constants h,c, and e together in the equation

The “pure” number of 137.03599913 is left behind as the units c, e, and h cancel each other out. Professor Davies explains that the inverse of the equation is employed for historical reasons: 2e2/hc = 1/137.03599913. If you’re wondering what the fraction’s exact value is, it’s 0.007297351.

Mathematics the language of the Universe!