In the first fractions of a second after the Big Bang, the universe was a stage of rapid change. A stretched rubber sheet that cools quickly becomes covered with microscopic cracks. A similar process on a cosmic scale could have given rise to cosmic strings — ultra-thin but super-dense threads of energy stretching across the entire universe.
These strings are not just defects in space. Their tension, a kind of 'stiffness,' depended on a special field that smoothly rolled toward its minimum, like a ball rolling into a pit. But physicists discovered a curious nuance: the 'ball' didn't just slip past the pit. It was slowed by friction created by the background 'noise'—gravitational waves emitted by the strings themselves as they decayed. This is like a cyclist coasting downhill: they don't crash into a wall but smoothly come to a stop by applying the brakes.
The study showed that different types of strings behaved differently. Some, like ephemeral 'bubbles,' disappeared quickly, creating that braking background. Others, more stable, lived longer and decayed only when the field was oscillating around its minimum. At that moment, they contained nearly a third of the universe's total energy. Their mass decay produced a characteristic 'burst' of gravitational waves — not one, but several, at different frequencies.
Thus, the ancient 'ring' of cosmic strings, like an echo, could bring us the story of how the fabric of the cosmos was forged in the very first instant.
A cosmic string as thick as a proton would weigh as much as a mountain range. If such a string passed through your room, you wouldn't notice its thickness, but you'd feel the floor shift by a fraction of a millimeter for an instant.