Almost any time physicists announced that they have discovered a new particle, whether it is a Higgs boson or a recently bagged particle tetraquark double predestination, what they actually detected was a small bump protruding from a smooth curve on a plot. Such a bump is an unmistakable sign of “resonance”, one of the most common phenomena in nature.
Resonance underlies such diverse aspects of the world as music, nuclear fusion in dying stars, and even the existence of subatomic particles. Here’s how the same effect manifests itself in such diverse contexts, from everyday life down to the tiniest of scales.
In its simplest form, resonance occurs when an object is subjected to an oscillating force close to one of its “natural” frequencies, where it readily oscillates. Natural-frequency bodies “are one of the fundamental properties of both mathematics and the universe,” says Matt Strassler, a particle physicist affiliated with Harvard University who is writing a book on the Higgs particle. A playground swing is a familiar example: “Hitting something like that around and it will always automatically pick out its resonant frequency,” says Strassler. Or flick a wine glass and the rim vibrates several hundred times per second, creating a distinctive sound as the vibrations travel through the surrounding air.
The natural frequencies of a system depend on its intrinsic properties: For a flute, for example, they are the frequencies of sound waves that fit exactly inside its cylindrical shape.
Swiss mathematician Leonhard Euler solved the equation describing a system that was continuously driven near its resonance frequency in 1739. He noticed that the system exhibited “different and wonderful motions” “, as he wrote it in a letter to the mathematician Johann Bernoulli, and that, when the system is precisely controlled at the resonant frequency, the amplitude of the motion “increases continuously and eventually grows to extremely.”
Manipulating a system too aggressively at the right frequency can have amazing effects: For example, a trained singer can break a glass with a steady note at a high frequency. its influence. A bridge that resonates with the footsteps of marching soldiers could collapse. But more often, the loss of energy, which Euler’s analysis missed, prevents the motion of a matter system from evolving unchecked. If the singer sings the note quietly, the oscillations in the glass will grow larger at first, but the larger oscillations cause more energy to be radiated to the outside in the form of sound waves than before, so eventually a The balance results in oscillations of constant amplitude.
Now, suppose the singer starts with a low note and continuously glides up in pitch. As the singer flipped through the frequency with which the glass of wine went, the sound momentarily became much louder. This improvement arises because the sound waves reaching the glass synchronize with the already existing oscillations, just as pushing the swing at the right time can amplify its initial motion. The plot of the sound amplitude as a function of frequency would plot a curve with a pronounced bump around the resonant frequency, a curve that particularly resembles the bumps that herald particle discoveries. In both cases, the width of the bump reflects how much loss the system has, for example, how long a glass vibrates after it is hit once, or how long a particle survives. before it decomposes.
But why do beads behave like wine glasses? In the early 20th century, resonance was understood as a property of vibrating and oscillating systems. Particles, moving in straight lines and scattered like billiard balls, seem far removed from this branch of physics.
The development of quantum mechanics has shown the opposite. Experiments show that light, considered an electromagnetic wave, sometimes behaves like a particle: a “photon”, possessing an amount of energy proportional to the frequency of the associated wave. Meanwhile, matter particles such as electrons sometimes exhibit vibration-like behavior with the same relationship between frequency and energy.
