Physicists are nearing a crucial point in their quest to unify two of the most fundamental theories of the universe: Albert Einstein's general relativity, which describes gravity and space-time on vast scales, and quantum mechanics, governing the behaviour of matter and energy at the atomic and subatomic levels. The long-standing challenge lies in reconciling these two frameworks, with most proposed solutions attempting to 'quantise' gravity – breaking it down into discrete, fundamental particles.
However, a controversial new theory from University College London (UCL) offers a radically different approach. Dr Jonathan Oppenheim and his colleagues have developed what they call 'post-quantum gravity,' which posits that space-time and gravity are not quantum at all, but rather continuous and fundamental entities without constituent building blocks. This stands in contrast to the other three fundamental forces – electromagnetism and the strong and weak nuclear forces – which are definitively quantum.
The mathematical framework of post-quantum gravity leads to a surprising prediction: the flow of time itself would experience small, random fluctuations. While we perceive time as a steady, regular progression, this theory suggests it would become subtly 'wobbly' at scales far too minute for human observation. These unpredictable shifts in time are crucial, as they allow Oppenheim's non-quantum gravity to interact with the inherently quantum forces and particles within space-time.
Intriguingly, when these temporal fluctuations are incorporated into basic quantum-mechanical calculations, they reproduce several key behaviours observed in quantum systems. This includes the famous 'measurement problem,' which explains why a quantum system, existing in multiple states simultaneously, appears to 'collapse' into a single, definite state upon observation – a concept often illustrated by Schrödinger's cat paradox. While the exact source of this predicted randomness in time remains an area for further investigation, it emerges directly from the theory's core equations.
Despite its controversial nature among many physicists, the theory's most compelling aspect is its testability. Unlike many other speculative ideas attempting to merge relativity and quantum mechanics, post-quantum gravity generates specific predictions that can, for the first time, be rigorously investigated in laboratory settings. This potential for experimental verification lends the theory a serious scientific weight that many of its quantum gravity counterparts lack, according to experts like Giuseppe Fabiano at the Lawrence Berkeley National Laboratory.