What Are Quark–Gluon Plasmas?

At the heart of atomic nuclei lie protons and neutrons, which are themselves composed of fundamental particles called quarks. These quarks cling together through the strong interaction, facilitated by force carriers known as gluons.

The Cosmic Connection: A Glimpse Post-Big Bang

During high-energy collisions of heavy atomic nuclei, these tightly held particles can break free, creating a state of matter known as quark–gluon plasma. This exotic substance flows with remarkable ease, resembling a liquid flowing through our everyday world, but it exhibits a stunningly low energy loss—behaving much like a near-perfect fluid.

Why Are Scientists Excited?

Scientists are keenly interested in quark–gluon plasmas because they dominated the universe just moments after the Big Bang, before the formation of matter as we know it today.

CERN's Groundbreaking Experiment

Researchers from the CMS Collaboration at CERN have successfully recreated this elusive state of matter, albeit for a brief period, by colliding large atomic nuclei. To probe this quark–gluon plasma’s essential characteristics, they employed sound waves.

Sound Waves: A Key to Understanding

Sound waves, which create alternating compressions and rarefactions through the medium they travel, can reveal much about that medium's properties. By analyzing these waves, the researchers uncovered that the speed of sound in their quark–gluon plasma was nearly half the speed of light—a groundbreaking measurement achieved with unprecedented precision.

Implications for Physics and Our Understanding of the Universe

These findings not only enhance our understanding of the fundamental forces that bind matter together, but they also provide crucial insights into the behavior of matter in the early universe. As we continue to explore particle colliders, this knowledge could pave the way for revolutionary discoveries in particle physics and cosmology.