Physicists just found a tiny flaw in time itself

Now, with support from the Foundational Questions Institute, FQxI, an international group of physicists has taken a closer look at alternative explanations known as quantum collapse models. Their findings suggest these ideas could have surprising consequences for how time itself behaves, including tiny limits on how precisely it can be measured. The research, published in Physical Review Research, also offers a possible way to test these models against standard quantum theory.

"What we did was to take seriously the idea that collapse models may be linked to gravity," says Nicola Bortolotti, a PhD student at the Enrico Fermi Museum and Research Centre (CREF) in Rome, Italy, who led the study. "And then we asked a very concrete question: What does this imply for time itself?"

Spontaneous Collapse and Testable Quantum Models

In the 1980s, researchers began developing theories in which wavefunction collapse happens spontaneously, without requiring observation or measurement. Unlike traditional interpretations of quantum mechanics, which mainly offer different ways of thinking about the same equations, these collapse models make predictions that could, in principle, be tested experimentally.

"What we did was to take seriously the idea that collapse models may be linked to gravity. And then we asked a very concrete question: What does this imply for time itself?" says Nicola Bortolotti.

Bortolotti and colleagues Catalina Curceanu, Kristian Piscicchia, Lajos Diósi, and Simone Manti examined two leading versions of these models. One is the Diósi-Penrose model, which has long proposed a connection between gravity and the collapse of the wavefunction. The other is Continuous Spontaneous Localization. In their new work, the researchers established a quantitative relationship between this second model and fluctuations in spacetime caused by gravity.

Tiny Time Uncertainty and Clock Precision Limits

Their analysis shows that if these collapse models accurately describe reality, then time itself cannot be perfectly exact. Instead, it would contain an extremely small level of inherent uncertainty. This would set a fundamental limit on how precise any clock could ever be.

"Once you do the calculation, the answer is clear and surprisingly reassuring," said Bortolotti.

Importantly, this effect is far too small to impact any current technology. Even the most advanced atomic clocks would not detect it. "The uncertainty is many orders of magnitude below anything we can currently measure, so it has no practical consequences for everyday timekeeping," says Curceanu. "Our results explicitly show that modern timekeeping technologies are entirely unaffected," adds Piscicchia.

Quantum Mechanics, Gravity, and the Nature of Time

For decades, physicists have been trying to unify quantum mechanics with gravity. Each theory works extremely well within its own domain. Quantum mechanics describes the behavior of particles at microscopic scales, while general relativity explains how gravity shapes the large-scale structure of the universe, including stars and galaxies. However, the two frameworks treat time in very different ways.

"In standard quantum mechanics, time is treated as an external, classical parameter that is not affected by the quantum system being studied," explains Curceanu. In contrast, general relativity describes time as something that can stretch and bend under the influence of mass and energy.

"The uncertainty is many orders of magnitude below anything we can currently measure, so it has no practical consequences for everyday timekeeping," says Catalina Curceanu.

By building on earlier ideas that quantum mechanics might be part of a deeper theory, the new research points to possible links between quantum behavior, gravity, and the flow of time itself.

Curceanu emphasized the importance of exploring unconventional ideas in physics. "There are not many foundations in the world which are supporting research on these types of fundamental questions about the universe, space, time, and matter," says Curceanu. "Our work shows that even radical ideas about quantum mechanics can be tested against precise physical measurements, and that, reassuringly, timekeeping remains one of the most stable pillars of modern physics."

This work was partially supported through FQxI's Consciousness in the Physical World program. You can read more about the team's grants in the FQxI article: "Can We Feel What It's Like to Be Quantum?" by Brendan Foster.