We already know how to measure one of the most elusive universal constants (and it can help us understand the universe better)

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The conversations that Albert Einstein had with some of his colleagues and pen friends have bequeathed to us a handful of very valuable reflections. Her former student Ilse Rosenthal-Schneider was also a highly valued confidant and collaborator of the German physicist, which led him to share with her some ideas that were swarming through her mind during the decades of the 40s and 50s of the last century. .

“There are two types of constants: apparent and real. Apparent constants result simply from introducing arbitrary units, but they can be eliminated. Real constants are authentic numbers that God must have chosen arbitrarily when he deigned to create this world,” Einstein asserted in a of the letters he sent to Rosenthal-Schneider during the stay of the German physicist and philosopher at the University of Sydney.

This reflection invites us not to overlook the enormous importance of universal constants in our effort to understand a little better the rules that govern nature. In fact, in the domain of science, a physical constant is the value acquired by a certain magnitude involved in physical processes that has a fundamental characteristic: it remains unchanged over time.

The fine structure constant shapes (and permeates) the entire universe

Some fundamental constants with which we are all familiar to some extent are the speed of light in a vacuum, the elementary charge or the gravitational and Planck constants, but there are others. Many others. And one of the most elusive is precisely the fine structure constant. It is elusive in the sense that it is very difficult to measure precisely in a direct way. In fact, until now scientists have calculated its value in an indirect way, which requires inferring it from other physical magnitudes.

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Sommerfeld’s constant quantifies the electromagnetic interaction that takes place between electrically charged particles.

Before going any further, it is worth making a brief stop on the way to inquire into this fundamental physical quantity. I propose that we leave aside the formal definition of the fine structure constant in order not to overcomplicate this article, but what we cannot ignore is that Sommerfeld’s constant, as it is also known, quantifies the electromagnetic interaction that takes place between electrically charged particles. No more no less.

Curiously, if its value were slightly different (it is approximately 1/137.0360 ≃ 0.00729735) our universe would not be as it is. In fact, it would be completely different. The structure of the atoms would be different, the interaction between the particles would be different, and even the nuclear fusion reactions that take place in the core of the stars would occur in a different way. The conditions necessary for them to take place may not even be in place, and in that case the “nuclear furnace” would not ignite. That’s how important this constant is.

Another very relevant characteristic that we cannot ignore is that is a dimensionless quantity. This simply means that it is independent of the unit system we use, and therefore is not paired with any unit. It is simply a number. A value. In any case, given its involvement in some fundamental physical phenomena, quantifying it accurately is essential to better understand and characterize them.

As we have seen, the procedures commonly used by scientists to calculate the value of Sommerfeld’s constant allow it to be quantified indirectly. Until now. And it is that a team of researchers from the Vienna University of Technology has devised an experiment that, according to Professor Andrei Pimenov, who is the leader of these physicists, has allowed them to calculate it directly. And approaching this constant like this, without other calculations, presumably gives us a more precise measurement.

The procedures commonly used by scientists to calculate the value of the Sommerfeld constant allow it to be quantified indirectly.

If you are curious to know how they did it and you are not intimidated by experimental physics, I suggest you take a look at the scientific article that these researchers have published in Applied Physics Letters. It’s complex, but it’s also extremely interesting and shows how resourceful some scientists are when forced to develop original strategies to overcome the barriers that stand between them and the purpose of their research.

Very broadly, what they have done has been to polarize a laser beam and direct it towards an extremely thin sheet of a material only a few nanometers thick so that the latter modifies the direction of polarization of the light. During their tests, they used various materials with different compositions and thicknesses until, bingo, they found one that “forces” the laser light to oscillate in a different direction.

What surprised them the most is the same thing that has brought us here. “This experiment gave us direct access to something very unusual: the measurement of a rotation in the realm of quantum mechanics. And from there the fine structure constant immediately emerged in the form of an angle”, explains Andrei Pimenov. It sounds complicated, and it is, but it is also exciting. And when this complexity can help us understand a little better how nature works, welcome.

Cover image: Arek Socha on Pixabay

More information: Applied Physics Letters

The conversations that Albert Einstein had with some of his colleagues and pen friends have bequeathed to us a handful…

The conversations that Albert Einstein had with some of his colleagues and pen friends have bequeathed to us a handful…

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