A team from TU Dortmund University recently succeeded in producing a highly durable time crystal that lived millions of times longer than could be shown in previous experiments. By doing so, they have corroborated an extremely interesting phenomenon that Nobel Prize laureate Frank Wilczek postulated around ten years ago and which had already found its way into science fiction movies.

The results have been published in Nature Physics.

Paper abstract – Robust continuous time crystal in an electron–nuclear spin system:

Abstract
Crystals spontaneously break the continuous translation symmetry of free space. Analogously, time crystals lift translational invariance in time. Here we demonstrate a robust continuous time crystal in an electron–nuclear spin system of a semiconductor tailored by tuning the material composition. Continuous, time-independent external driving of the sample produces periodic auto-oscillations with a coherence time exceeding hours. Varying the experimental parameters reveals wide ranges in which the time crystal remains stable. At the edges of these ranges, we find chaotic behaviour with a lifted periodicity corresponding to the melting of the crystal. The time crystal state enables fundamental studies of nonlinear interactions and has potential applications as a precise on-chip frequency standard.

In the movies, time travelers typically step inside a machine and—poof—disappear. They then reappear instantaneously among cowboys, knights or dinosaurs. What these films show is basically time teleportation.

Scientists don’t think this conception is likely in the real world, but they also don’t relegate time travel to the crackpot realm. In fact, the laws of physics might allow chronological hopping, but the devil is in the details.

[…]

If a person were to hang out near the edge of a black hole, where gravity is prodigious, Goldberg says, only a few hours might pass for them while 1,000 years went by for someone on Earth. If the person who was near the black hole returned to this planet, they would have effectively traveled to the future. “That is a real effect,” he says. “That is completely uncontroversial.”

Going backward in time gets thorny, though (thornier than getting ripped to shreds inside a black hole). Scientists have come up with a few ways it might be possible, and they have been aware of time travel paradoxes in general relativity for decades. Fabio Costa, a physicist at the Nordic Institute for Theoretical Physics, notes that an early solution with time travel began with a scenario written in the 1920s. That idea involved massive long cylinder that spun fast in the manner of straw rolled between your palms and that twisted spacetime along with it. The understanding that this object could act as a time machine allowing one to travel to the past only happened in the 1970s, a few decades after scientists had discovered a phenomenon called “closed timelike curves.”

“A closed timelike curve describes the trajectory of a hypothetical observer that, while always traveling forward in time from their own perspective, at some point finds themselves at the same place and time where they started, creating a loop,” Costa says. “This is possible in a region of spacetime that, warped by gravity, loops into itself.”

“Einstein read about closed timelike curves and was very disturbed by this idea,” he adds. The phenomenon nevertheless spurred later research.

Science began to take time travel seriously in the 1980s. In 1990, for instance, Russian physicist Igor Novikov and American physicist Kip Thorne collaborated on a research paper about closed time-like curves. “They started to study not only how one could try to build a time machine but also how it would work,” Costa says.

[Article continues…]

Link to study paper: Nonclassical Advantage in Metrology Established via Quantum Simulations of Hypothetical Closed Timelike Curves

Abstract:

We construct a metrology experiment in which the metrologist can sometimes amend the input state by simulating a closed timelike curve, a worldline that travels backward in time. The existence of closed timelike curves is hypothetical. Nevertheless, they can be simulated probabilistically by quantum-teleportation circuits. We leverage such simulations to pinpoint a counterintuitive nonclassical advantage achievable with entanglement. Our experiment echoes a common information-processing task: A metrologist must prepare probes to input into an unknown quantum interaction. The goal is to infer as much information per probe as possible. If the input is optimal, the information gained per probe can exceed any value achievable classically. The problem is that, only after the interaction does the metrologist learn which input would have been optimal. The metrologist can attempt to change the input by effectively teleporting the optimal input back in time, via entanglement manipulation. The effective time travel sometimes fails but ensures that, summed over trials, the metrologist’s winnings are positive. Our Gedankenexperiment demonstrates that entanglement can generate operational advantages forbidden in classical chronology-respecting theories.

Physicists have shown that simulating models of hypothetical time travel can solve experimental problems that appear impossible to solve using standard physics.

We are not proposing a time travel machine, but rather a deep dive into the fundamentals of quantum mechanics. – David Arvidsson-Shukur

This report on experiments into time travel and extra sensory perception during the 1960s and 70s deserves a read.

It relates to non-physical time travel which, after years of research, I’m personally leaning towards as far as feasibility.

Assuming time is a separate dimension from the 0th-3rd, we wouldn’t be able to move in it in the third dimension (the physical) any more than we can physically move with our bodies in the 1st or 2nd.

If consciousness can move in higher dimensions, though (and we know it does, because it moves in time every moment; that’s how we perceive time), it isn’t constrained to the third like our bodies are. We already move through time, so the task would be moving consciously instead of being dragged along.

This may all be pseudoscientific bullshit, but if we can find empirical ways to test these hypotheses, I believe it’s worth exploring.

Abstract

This paper is an enquiry into the logical, metaphysical, and physical possibility of time travel understood in the sense of the existence of closed worldlines that can be traced out by physical objects. We argue that none of the purported paradoxes rule out time travel either on grounds of logic or metaphysics. More relevantly, modern spacetime theories such as general relativity seem to permit models that feature closed worldlines. We discuss, in the context of Gödel's infamous argument for the ideality of time based on his eponymous spacetime, what this apparent physical possibility of time travel means. Furthermore, we review the recent literature on so-called time machines, i.e., of devices that produce closed worldlines where none would have existed otherwise. Finally, we investigate what the implications of the quantum behaviour of matter for the possibility of time travel might be and explicate in what sense time travel might be possible according to leading contenders for full quantum theories of gravity such as string theory and loop quantum gravity.

1. There is a large philosophical literature on the first two paradoxes (and others), see, e.g., the entry on time travel, Wasserman (2018), and Effingham (2020), but very little on the easy knowledge paradox (emphasized by Deutsch 1991, discussed further below). Our approach differs from the literature surveyed in these two books by focusing on the physical—rather than metaphysical—possibility of time travel.

2. Multiple collisions are handled in the obvious way by continuity considerations: just continue straight lines through the collision point and identify which particle is which by their ordering in space.

3. The dynamics here is radically non-time-reversible. Indeed, the dynamics is deterministic in the future direction but not in the past direction.

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Interesting discussion by Christopher Smeenk.

The first way we'll implement time travel will be sending data. First will be the equivalent of messages in a bottle – with no ability to choose the recipient – then we'll be able to send ordered data (the equivalent of texts, followed by voice/waves, then pictures/video, and eventually physical matter). We should currently be looking for rudimentary messages sent to us from the future, not trying to physically travel in time.

Adding dimensions to our understanding is a step towards navigating them. Time is the next logical dimension to understand (see, map, and navigate), and we can be fairly sure of this because we already travel in that dimension, though we don't yet have conscious control of our interactions within it. That means the time dimension interacts strongly with our native 3rd dimension (I mean strongly as opposed to weak interactions we can see with other particles in quantum physics).

Visualising that dimension will lead to navigation, though it won't become physically usable straight away. We should be looking for messages sent via data from the future, not trying to build a physical time machine.

A physical time machine as we've historically envisioned may not be possible, because the mechanism for moving through time in ways other than our standard vector may not have anything to do with the 3rd dimension that we're embedded within. Since time is likely a separate dimension from what we consider the third (and in which we're used to operating), a mechanism that allows us to travel in time will likely not be a 3rd dimensional 'machine'.

Visualising dimensions beyond our usual perception is the first step. If we can understand the structure of other dimensions and map out their rules, we increase the chance of being able to gain conscious control over them collectively. That would absolutely look like magic at first (in a similar way to lightning looking like magic to primitive people, but it's rooted in science that can be understood and manipulated), but it's nonetheless a real thing with properties and rules that we can understand and interact with. We already interact with it, albeit passively.

We move in one direction and see in the opposite. The first is our perception of the future; that's our normal vector. The second is our memory. We experience the highest fidelity at the point we call now, in which our local time point intersects strongly with at least 3 other dimensions. What we experience as the past is a perceptual gradient cone with less fidelity the farther it recedes from our 'current' perceptional point.

We should develop a receiver/detector first. We typically do this with properties of the universe which we observe, using physics and mathematics. Observation comes first, followed by documenting and testing rules, constants, variables, and formulas – that's how science works. Any observations and conclusions must make sense within the framework of existing physics.

Some preliminary questions include:

We each have a local reference frame as dictated by einsteinian physics in which time feels constant, and we know local perception isn't constant across the universe like, say, causality. We can define our local time using mathematical formulas, and we've explored some of its rules. We need to increase the fidelity of our understanding, defining more time rules, constants, variables, and formulas so we can properly design experiments.

Are there particles that link strongly to the time dimension? How are they structured? What are their underlying wave structures? What are their constants and properties? How can we express them using formulas? How do they interact with the other closest dimensional intersections or interfaces? How can we see or visualise them? How can we manipulate them?

What are the constants associated with our current vector? What formulas define our location and movement, and how can they be manipulated?

We need a receiver, like an analogue to the radio. We usually develop rudimentary receivers before we can fully map our understanding of a phenomenon. We likely already have enough knowledge to build one, like any other sensor we've developed. We just need to know what signal we're looking for. Assuming we've worked this out in the future, what's the simplest signal we should be looking for and how would we detect it? That should be our first step.

So the most intriguing question we can answer right now is: What would a message from the future look like, and how would we receive it?

E: I'm terrible at spelling apparently