In 1922, two researchers, Stern and Gerlach, conducted an experiment that later became one of the keys to quantum physics. Their goal was to measure the magnetic properties caused by the movement of electrons on orbit. However, at that time they were unaware of the existence of quantum spin – a quantum property of particles associated with angular momentum. Despite the experiment clearly demonstrating manifestations of quantum spin, physicists took years to realize this groundbreaking discovery.
In the experiment, scientists heated silver foil so that atoms flowed through a small hole. Silver was chosen for its simple structure: silver atoms have one electron on the outer shell. Passing through a magnetic field, silver atoms deviated, creating an image on a film where this deviation depended on their magnetic moment.
If the electrons moved randomly around the nucleus, a blurry line would have appeared on the film. If their orbits were fixed, the picture should have consisted of several clear points. However, the result was completely unexpected: the image resembled the contour of lips.
Further observations revealed that horizontal deviation was present even without a magnet. This indicated the existence of two possible electron orientations, but the explanation of this phenomenon only became possible later with the advent of Schrödinger’s equations. These calculations suggested that the experiment’s results should have been presented at one point, but instead, Stern and Gerlach’s experiment confirmed the existence of quantum spin.
Remarkably, this success was somewhat accidental. The initial goal of the experiment was entirely different, but the method perfectly showcased quantum spin – a phenomenon no one knew about at that time. This case underscores the amazing and unpredictable nature of the scientific process.
Today, quantum spin plays a crucial role in the development of quantum computers. It has become a fundamental concept in understanding quantum mechanics and has paved the way for new technologies.