According to theories beyond the Standard Model, our best description of elementary particles and their interactions, pairs of magnetic monopoles were born in the first instants after the Big Bang. These hypothetical particles carry only one magnetic pole—'north' or 'south'—unlike familiar magnets where poles are inseparable. The monopoles sat at the ends of a cosmic string, a one-dimensional filament of pure energy left over from phase transitions in the early Universe. This string acts like a tight rubber band: one end pulls the 'north' monopole, the other pulls the 'south' one. The analogy simplifies the picture, as the real string is a quantum object with colossal tension. A single monopole weighs as much as billions of protons but fits within a volume smaller than an atomic nucleus, making it an extremely dense and massive micro-object.

Over time, the string contracts under its own tension, drawing the monopoles closer. When they merge, their annihilation releases energy, causing the string to snap. Across the fabric of spacetime, the geometric stage where all physical events unfold, ripples spread: gravitational waves, predicted by general relativity. Their frequencies lie in the audible range: from a low rumble to a piercing squeak, allowing the signal to be converted into sound for analysis. Detectors on Earth, such as LIGO and Virgo, which use laser interferometry to catch the tiniest vibrations of space, could pick up this unique signal. Detecting such waves would be direct proof of the existence of monopoles and strings, a step toward understanding the birth of the Universe.