For decades, quantum physics has predicted the spontaneous creation of particles from seemingly empty space—a concept known as virtual particles. Now, for the first time, scientists at the Relativistic Heavy Ion Collider (RHIC) have traced the evolution of these “something-from-nothing” particles, confirming their existence and behavior in a groundbreaking experiment. The findings, published in Nature, provide direct evidence of particles originating from the quantum vacuum and shed light on fundamental questions about mass and the nature of reality.
The Quantum Vacuum: Not So Empty
The universe, at its most basic level, isn’t filled with nothing. Instead, quantum theory suggests a restless “vacuum” teeming with virtual particles that blink in and out of existence due to the inherent uncertainty in quantum mechanics. These particles don’t last long, as Heisenberg’s uncertainty principle dictates that energy and time cannot both be precisely known. This allows particles and their antimatter counterparts to briefly “borrow” energy from the vacuum, existing for fleeting moments before annihilating.
Traditionally, the effects of these particles have been indirect—observed through their influence on other phenomena. But RHIC researchers have now observed the process directly.
Collisions and Entanglement: Making the Invisible Real
At RHIC, physicists collide protons at nearly the speed of light, creating conditions of extreme energy. These collisions provide the necessary “push” for virtual particles to become real. When a virtual particle pair arises within this high-energy environment, it can draw on the collision’s energy to stabilize and persist.
The experiment focused on pairs of “strange” quarks—fundamental particles that, when created, quickly combine with others to form lambda hyperons. These hyperons are short-lived, decaying almost instantly into detectable particles. By tracking the decay products, physicists were able to deduce the spin direction of the original lambda hyperons and, crucially, the correlated spin of their constituent strange quarks.
The key observation was that these quarks consistently exhibited parallel spins. This alignment suggests they originated as an entangled pair from the quantum vacuum, retaining their connection even as they flew apart after the collision.
Confirming a Long-Held Prediction
The findings validate a 30-year-old theoretical prediction made by physicist Dmitri Kharzeev and colleagues. “It’s exciting to see that nature follows this prediction,” Kharzeev stated, highlighting the significance of experimental confirmation for long-standing theoretical ideas.
The ability to observe this process opens new avenues for understanding one of the biggest mysteries in nuclear physics: the origin of proton mass. The quarks inside protons only account for a tiny fraction of their total mass; the remaining 99% is believed to come from interactions with virtual particles in the vacuum. By tracing the journey from virtual to real particles, scientists hope to unravel how this mass is generated.
End of an Era, Dawn of New Research
RHIC is set to conclude its 25-year run this week, with parts of the machine repurposed for the upcoming Electron-Ion Collider. This new facility promises to build on these discoveries, further exploring the hidden dynamics of the quantum vacuum and the fundamental building blocks of matter.
The direct observation of particles emerging from nothing represents a major step forward in our understanding of the universe, bridging the gap between theory and experiment in the realm of quantum physics. The implications of this research will continue to unfold as scientists push the boundaries of what we know about the nature of reality.
