Time Jam: Can Meaning Travel Backward Through Time?

On the second day of a conference about time machines in San Diego, a walk up a hill became a physics problem. Julia Mossbridge, a cognitive neuroscientist, had been thinking about her colleague Avshalom Elitzur, a physicist and philosopher, when she rounded a bend and saw him standing on the path above her. In "Time Jam," a video recorded at a Quantum Time Machines meeting in July 2022, the two of them take that small human moment and push on it until it becomes a question about information, meaning, and whether time runs in only one direction. What unfolds is less a lecture than a live experiment in thinking: Mossbridge proposes a model, Elitzur objects, and both keep correcting each other as they go.

What happened on the hill, and why does Mossbridge treat it as physics?

Mossbridge frames the story with a playful bit of shorthand. She casts herself and Elitzur as two particles, "the Julia particle" and a second particle standing in for him, and describes their exchanges as signals passed between them. The sequence starts the day before the hill. Walking to the conference site, Elitzur told her she looked wonderful. She read his face as sincere, answered with a thank-you, and the exchange stuck with her as a meaningful signal.

The next day, she saw him on the path above her. In her account, information moved one way: she saw him, and the sight gave her meaning. He did not see her at all, so nothing came back. Yet he was having a similar experience of connection and gratitude, and neither of them had sent it to the other. Mossbridge's word for this is "shared meaning," arising separately in two places but matching. She calls it simultaneous rather than transmitted.

Later that day, they met by the coffee table and talked about what had happened. That conversation was a two-way exchange: each sent and each received, and the meaning now moved between them in both directions. Mossbridge uses this sequence to make a point about how physicists tell the story of quantum experiments. In her words from the video, when we look at experiments like entanglement and delayed-choice setups, "we often stop here," at the measurement, and start talking about impossibilities. If you add the later, fully local exchange, she argues, the picture changes. Information may be conserved across the whole sequence, and the apparent "information coming from the future to the past" becomes a question of which part of the story you count.

"I just think this might have something to do with the fact that when we look at experiments like entanglement and time or delayed-choice experiments we often stop here." (Mossbridge, Time Jam, 2022, around 4:30 to 5:00)

Her claim is careful. She is not saying the hill proves anything about physics. She is saying that the frame of a physics experiment, where you draw the boundary and decide what counts as a signal, may hide information that a fuller frame would capture. Then she asks whether the no-signaling rule, which forbids faster-than-light messaging, needs to be reconsidered once the whole context is included. Elitzur's reply is that he understands the logic. The conversation moves on from there.

Why does Elitzur draw a hard line at synchronicity?

Elitzur is clear about where he stands. He says he is a physicist and what he does is physics, and he stays away from parapsychology. He is usually uncomfortable, he says, when people attach too much meaning to synchronicities. He does not wave the experience away, though. In the video he recounts a personal moment from the conference, looking out over the valley and feeling ashamed of his bitterness, and he describes being moved to tears. He treats that as human experience, separate from the physics claims he is willing to make.

His preferred bridge between the personal and the scientific runs through his thermodynamic work on biology. He argues that evolution can be understood as a process in which information accumulates within living systems. Darwin described adaptation, Elitzur says, and adaptation requires information about the environment. That information does not have to sit in a brain. DNA, and tissues generally, carry it too. He points viewers to his published papers on this topic, which he says can be found online.

This is the most useful tension in the conversation. Mossbridge is willing to let an experience of meaning serve as data for a model. Elitzur wants the model to answer to physical constraints first. Both positions are visible in the exchange, and neither dissolves the other.

Can you really travel backward through time?

Elitzur's contribution to the time-machine question is blunt. He calls himself the killjoy of the conference, because he does not think time travel of the kind being discussed is possible. His reasoning starts from what he considers one of the great riddles of physics: "there is something very strange about time." In space, you can stay where you are, move forward, or move backward. Time doesn't work that way. You can stop going forward, but you cannot go backward. In his words from the video, "time seems to have a direction," and physics has not yet fully explained why.

He draws on special relativity to show how deep the puzzle goes. Relativity treats time and space as parts of a single four-dimensional continuum, and the two of them mix under changes of motion. Elitzur refers to Lorentz contraction as a case where that mixing becomes concrete. Once you accept this picture, the everyday distinction between past, present, and future becomes harder to hold on to. The conversation takes up the claim that this distinction may be a kind of illusion, and the discussion grows more uncertain from there.

What does the photon reveal about the limits of our language?

The conversation's most uncertain stretch comes when they turn to photons. Elitzur calls the photon's behavior "very crazy," and the two of them spend time asking whether the ordinary language of motion, cause, and time can describe what happens in such systems. Neither claims to have the answer. Their habit of testing each other's language is the point. They ask how a concept would be stated in a different framework, whether it survives the change, and where it breaks.

A note for viewers: the auto-generated transcript is rough in places, so some exchanges are hard to follow word for word. Read the photon section as a sketch of an idea in progress rather than a settled argument.

Why does an open-ended conversation matter more than a conclusion?

The video's own description gives the frame. The two scientists say they query and correct each other as they search for an answer, and they acknowledge that they are probably wrong about some of it. The aim they state is to keep the conversation in a spirit of free idea sharing rather than competition or one-upsmanship. That stance is why the video is worth watching. A reader does not get a verdict on whether time travel is possible or whether meaning can cross time. What the reader gets is a demonstration of how two trained minds can take an intuition seriously, test it against physics, and admit where it fails.

Mossbridge's hill story is valuable because it is ordinary. A glance, a gesture of gratitude, a later conversation: these are exactly the moments most people would never think to examine. By treating them as data, she asks whether our frameworks for information, signaling, and time are wide enough to hold them. Elitzur's objections keep the question honest. The result is a dialogue that is more useful as a model of inquiry than as a finished theory.

Where to go from here

• Watch "Time Jam" with the moments in mind: the hill story around the early minutes, Mossbridge's conservation-of-information argument, Elitzur's time-direction riddle, and the photon section near the end.
• Look up Elitzur's published work on the thermodynamic view of evolution and adaptation, which he points to in the video.
• Read an introductory account of entanglement and delayed-choice experiments, so you can see exactly where Mossbridge says physicists tend to stop the story.
• Explore the arrow of time and special relativity's four-dimensional picture of space and time, the two frameworks at the center of Elitzur's objections.
• Try the conversation's method yourself: take a personal experience, state the claim plainly, and invite a friend to correct it.