Time travel has long captured the human imagination, from its appearances in science fiction fantasies to its profound implications in modern theoretical physics. Now, a recent study by Dr. Lorenzo Gavassino, a theoretical and mathematical physicist at Vanderbilt University, delves into the enigmatic nature of time travel involving time loops to examine their profound implications for quantum mechanics, entropy, and human experience.
Dr. Gavassino’s findings, published in Classical and Quantum Gravity, present a strikingly different picture of time travel. They reveal that traveling through such time loops would prevent many classical time travel paradoxes, including the infamous “grandfather paradox.”
“It is often assumed that, in a Universe with Closed Timelike Curves (CTCs), people can ‘travel to the past,'” Dr. Gavassino writes. “On the surface, this seems to be an obvious implication, since (on sufficiently large scales) one may view a timelike curve as the worldline of a hypothetical spaceship traveling across the spacetime. However, to confirm that this is an actual journey to the past, we must first discuss what happens to the passengers (i.e., to macroscopic systems of particles) as they complete the roundtrip.”
“For example, consider the following question: ‘Can Alice meet her younger self at the end of the journey?’ Answering this and similar queries ultimately boils down to determining the statistical evolution of non-equilibrium thermodynamic systems on CTCs.”
Einstein’s theory of general relativity proposes that time travel to the past might be theoretically possible under specific conditions, such as exotic spacetime geometries like traversable wormholes, cosmic strings, or faster-than-light travel.
However, even if such phenomena were achievable, scholars have long grappled with the logical contradictions time travel introduces. In particular, the paradoxes associated with foreknowledge of the future render time travel implausible.
The consistency paradox is often considered the cornerstone of these time travel conundrums, which asks what happens if a time traveler alters the past in ways that prevent their existence.
Commonly known as the “grandfather paradox,” the consistency paradox has been a staple of science fiction, frequently explored in stories about time travel. For example, in the 1985 film Back to the Future, the main character, Marty McFly, accidentally creates a paradox that prevents his parents from meeting, jeopardizing his own existence.
In his recent paper, Dr. Gavassino offers a provocative solution to time travel’s biggest logical challenges. According to him, in a universe with closed timelike curves (CTCs), the laws of quantum mechanics would inherently erase many time travel paradoxes.
Dr. Gavassino’s study reveals that any system traveling through a time loop experiences a reset in entropy and memory, ensuring that causality remains intact and preventing contradictions like the grandfather paradox from arising.
At the core of Dr. Gavassino’s research lies the concept of closed timelike curves (CTCs), theoretical paths within spacetime that loop back to their origin.
Closed timelike curves could only exist under highly exotic conditions predicted by Einstein’s general relativity. These conditions include phenomena such as traversable wormholes, where a stable tunnel between distant points in spacetime is maintained using negative energy or exotic matter to prevent collapse.
Similarly, rotating spacetimes, like those described by the Gödel metric, suggest that intense angular momentum on a cosmic scale could create paths that loop back in time.
Cosmic strings, hypothesized one-dimensional defects formed during the early universe, could also theoretically generate CTCs if they moved past each other at near-light speeds or rotated rapidly, distorting spacetime enough to permit time loops.
Another possibility involves Kerr black holes, where the extreme rotation near their event horizons could theoretically enable closed paths in time, though such regions are likely unstable due to singularities and quantum effects.
These scenarios require conditions far beyond what is naturally observable or technologically achievable, including negative energy density or exotic spacetime geometries. Likewise, these theoretical constructs face significant challenges, such as energy requirements, stability issues, and the potential invalidation of causality, making the natural or artificial creation of CTCs an extraordinary challenge.
Nevertheless, Dr. Gavassino used a mathematical model of a spaceship traveling on a CTC to examine such a journey’s physical and quantum dynamics. His analysis revealed that systems traveling along these curves undergo a spontaneous quantum restructuring, including discrete energy level adjustments and entropy inversions. This ensures that all internal states and systems reset to their original configuration by the end of the loop.
One of the study’s most remarkable discoveries is the erasure of memories for individuals or systems traveling on a CTC. Memory formation, closely tied to the increase of entropy over time, is inherently unstable on a CTC due to the reversal of the entropic arrow of time.
As entropy decreases during the journey’s second half, all processes—including memory retention—reverse, leaving the traveler unable to recall their experiences within the loop.
This phenomenon ensures that no observer within the loop can interfere with their past or create causal paradoxes, as their memory and internal states are effectively “reset” upon completing the journey.
In simple terms, time travel may be theoretically possible, but Dr. Gavassino’s findings reveal that altering the past is fundamentally impossible.
Entropy plays a pivotal role in understanding the physics of time loops. In ordinary systems, entropy—the measure of disorder—steadily increases, providing a clear arrow of time.
However, Dr. Gavassino’s findings show that CTCs impose a periodic constraint on entropy, requiring it to return to its minimum value at specific points along the loop.
This phenomenon aligns with the Poincaré recurrence theorem, which predicts that finite, isolated systems will eventually return to their initial states. In the case of CTCs, this return occurs at regular intervals, dictated by the curve’s properties.
Dr. Gavassino’s research demonstrates how quantum mechanics ensures the self-consistency of time loops. The study shows that the energy levels of systems traveling on CTCs are quantized so that all processes remain coherent and self-correcting.
For example, an unstable particle that decays into smaller components during the journey is observed to spontaneously reassemble into its original form as the journey nears its end. While counterintuitive in ordinary thermodynamics, this behavior is a natural consequence of the quantum constraints imposed by the CTC.
The implications of these findings could be profound. Unlike the chaotic and paradoxical time travel scenarios often depicted in science fiction, the findings suggest that time travel via CTCs operates under strict quantum mechanical rules that prevent disruptions to causality. Any deviations in entropy are reversed, memories are erased, and the system returns to its starting state without contradictions or inconsistencies.
This framework provides a stable, albeit unsettling, model of time travel in which classical paradoxes such as meeting a younger version of oneself or altering the past are inherently avoided.
The study also delves into the nature of reality within a time loop. At the point of minimum entropy on a CTC, causality appears to break down entirely. Complex systems, including living organisms, can seemingly “fluctuate into existence” without a clear origin, consistent with quantum statistical mechanics.
For example, a book might appear without an author, or a person might possess memories that have no logical basis in the system’s macroscopic history. These low-entropy states exist in isolation, disconnected from traditional causal chains, yet they fit within the broader framework of quantum mechanics.
While the study does not claim that interacting with one’s future or past self is impossible, it frames such encounters unconventionally. Any older version of a person encountered in a time loop would likely have no causal relationship to the younger version due to the resetting of entropy and memory. Such an “older clone” might emerge from the random fluctuations at the loop’s minimum entropy point, carrying no verifiable link to the timeline of the younger self.
Dr. Gavassino’s work offers a unique perspective on time travel, grounding these speculative ideas in the rigorous framework of quantum mechanics.
While closed timelike curves remain purely theoretical, their implications challenge and expand our understanding of time, causality, and the laws of the universe.
This research highlights that if time travel were ever possible, it would not resemble the whimsical journeys of popular culture but instead operate as a highly constrained and self-consistent quantum process.
Ultimately, while the possibility of traversing through time may not be as far-fetched as once thought, one crucial takeaway is clear: the past is permanent.
No matter how advanced our understanding of spacetime becomes, the laws of physics appear to safeguard causality, ensuring that history remains unchangeable. Time travel may one day allow us to observe and experience the past—but rewriting it will forever remain out of reach.
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com