Going back into your own history is impossible across a wide range of theoretical universes, according to research published by a researcher at the University of Jinan.
Hongsheng Zhang grounded the argument in a single feature of relativity.
light can never point sideways to a traveller’s direction in time,
Hongsheng Zhang, researcher at the University of Jinan
Through a recent study, Jinan University physicist Hongsheng Zhang in China presented a straightforward mathematical rationale regarding why going backward in time cannot happen physically. Within such a universe, progression is restricted solely ahead — akin to a one-way highway offering zero opportunity to turn around.
This investigation supplements three established scientific frameworks that researchers utilize to rule out time loops: Universal time, denoting a global clock’s existence that perpetually advances; energy constraints, which entail banning negative energy alongside exotic matter; and topological criteria, focusing on the characteristics governing spacetime’s connectivity and geometry.
What sets this new approach apart is its capacity to dismiss time travel concepts via basic algebraic computations, avoiding the complexities of intricate cosmic models.
The proof requires no exotic matter, quantum effects, or assumptions about what fills the universe.
Journeys to the past are known to physicists as closed timelike curves, which are paths through spacetime that loop back to the place and moment of their beginning. Einstein’s equations allow such paths in a handful of scenarios.
🔴 Physicist claims time travel to past impossible in most universes Hongsheng Zhang, a researcher at the University of Jinan in China, demonstrated that in a broad class of theoretical universes, travelling into the past is impossible. The argument rests on relativity: the… pic.twitter.com/gBnH4RKJbB
Suppose you wanted to shake hands with your younger self,
Hongsheng Zhang, researcher at the University of Jinan
To do that you would need a path through spacetime that loops back on itself without ever exceeding the speed of light.
Hongsheng Zhang, researcher at the University of Jinan
The research outlines two theoretical exceptions where the restriction could be circumvented. Twist represents the initial exception, happening when light beams intertwine like rope fibers rather than traveling parallel to one another.
Under Einstein’s theory, a spinning mass drags space and time along with it. Physicist Brandon Carter demonstrated in 1968 that such loops exist inside spinning black holes. Zhang noted that twist alone does not create a closed curve.
Twist on its own does not create a closed curve. It only blocks my argument,
Hongsheng Zhang, researcher at the University of Jinan
The second route relates to the shape of the universe itself, known as topology. Most time machines designed on paper, including wormholes, depend on this geometry. Zhang himself emphasizes that what the theorem does not say is whether nature allows any of these phenomena, noting that remains an open question.
The loophole that could matter is topology, and that is exactly the one that looks least likely to arise without deliberate engineering,
Hongsheng Zhang, researcher at the University of Jinan
Trips to the future are already well established through relativity, as moving fast or sitting in strong gravity slows a clock relative to everyone else. Whenever someone travels at immense velocities or encounters intense gravitational pull, their personal clock lags behind those watched by different observers.
Data from the European Space Agency indicates that crew members on the International Space Station arrive back on Earth a few thousandths of a second younger relative to what would have occurred otherwise.
This is not a claim that time travel is impossible,
Hongsheng Zhang, researcher at the University of Jinan
