Quantum physics and Einstein's theory of general relativity are the two pillars upon which our understanding of the Universe is based, each excelling in describing phenomena at its own scale. However, these two theories seem incompatible when it comes to linking the quantum world to that of gravity. An international team of researchers has taken a significant step towards solving this puzzle by measuring the gravitational force at the microscopic scale for the first time.
Gravity, the force that anchors us to Earth and governs the motion of the planets, has long eluded a quantum description, unlike the Universe's three other fundamental forces. By succeeding in detecting a weak gravitational force acting on a tiny particle, scientists are paving the way toward a theory of "quantum gravity."
This breakthrough is not just technical; it carries the potential to answer some of physics' deepest questions. How did the Universe begin? What happens inside a black hole? Can all the fundamental forces be unified into a single theory?
The challenge of measuring gravity at such a reduced scale required the use of superconducting magnetic traps and extremely low temperatures, nearing absolute zero. It was under these conditions that the gravitational force, unprecedentedly weak at 30 attoNewtons, was detected on the particle.
An illustration showing a quantum experiment investigating gravity at a small scale.
Credit: University of Southampton
This meticulous work is just the beginning of a scientific journey that promises to push the boundaries of our knowledge. Researchers are already planning to further reduce the mass of the studied particles, inching ever closer to the world of quantum physics.