Video: Hear the sound of the little bang

The hottest material ever created in the laboratory makes an eerie drone. A similar sound may have pervaded the universe just after the big bang, when space was a seething cauldron of matter.

The lab-made material was created at the Relativistic Heavy Ion Collider in Upton, New York. The particle smasher slams gold ions together, breaking the atoms and their constituent protons and neutrons into even smaller bits called quarks and gluons.

The resulting fireball – called a quark-gluon plasma – is trillions of degrees and mimics conditions when the universe was a millionth of a second old. As the fireball created in this “little bang” cools, the individual quarks and gluons combine into a zoo of larger particles.

Physicist Ágnes Mócsy of the Pratt Institute in Brooklyn, New York, and colleagues have calculated what this fireball of quarks and gluons would sound like to an observer embedded within it.


Expanding fireball

By analysing measurements made using roughly 3 million collisions, the team determined the general lumpiness of the fireballs – how closely spaced their particles were.

Fluctuations in density correspond to sound waves. So the researchers studied how the distribution of particles evolved in time to see how the sound changed. They then had to multiply the wavelengths of the sound by roughly 10 billion billion to be audible to the human ear.

In the resulting soundtrack, lower tones become more and more prominent as the fireball expands and the speed of sound changes due to the resulting drop in the fireball’s density.

About halfway through, a wiggle in the tone signals the point at which quarks and gluons recombine to form particles from protons to pions. Watch a longer video narrated by the researchers here.