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In a new paper, a group of physicists claims to have confirmed the existence of “negative time.” I had never heard of this, but I had a look at the paper. And I think I have figured it out.
Paper: https://arxiv.org/abs/2409.
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This result challenges our fundamental intuition about how time flows, but that is what makes physics beautiful. The fact that photons can exhibit negative group delay in a transparent medium has been theoretically predicted for a while, but seeing it confirmed experimentally with such precision is exciting. It reminds me of how AI image generators can now create visuals that seem to defy conventional spatial constraints. Both fields are pushing boundaries of what we thought was possible.
The idea of ´negative time´ is doubtful/wrong
Because every object on earth is transported by its rotation, is moved by the earth around the sun — and the sun-system is part of a rotating galaxy in an expanding universe
All these movements are an essential property of every object — and to stop or even reverse time does mean that all these dynamic movements have to be stopped or even reversed too.
This is not possible
Physicists have not delivered a definition for TIME up to now!
Therefore all statements about TIME are of very poor quality.
And as long we do not know what TIME is — we can not measure TIME
Bishop Augustine distinguished in CONFESSIONS (book 11, chap. 13–29) already 1600 year ago — three different types: the a) divine, b) physical, c) human time / time-perception.
When we want to understand what TIME is, then we have to discuss these three types of TIME — each seperately
Interesting article — the “negative time” claim is a great reminder that physics often sounds stranger than it really is. The discussion around group delay versus actual time travel is especially important, because headlines can make a subtle result feel much bigger than it is. I also like how the post helps separate the experimental effect from the interpretation. For anyone who enjoys this kind of boundary-pushing idea, I’ve been experimenting with creative tools like phonk maker to turn abstract concepts into something more vivid and memorable.
It’s interesting how a lab measurement about photon group delay gets framed as “negative time” in the headline. The article does a good job clarifying what the experiment actually shows.
her trees puzzle dream
It’s interesting how a lab measurement about photon group delay gets framed as “negative time” in the headline. The article does a good job clarifying what the experiment actually shows.
The distinction between group delay and actual time travel is easy to blur, so I appreciate how clearly the article walks through the physics.Her Trees
The article’s mention of physicists claiming “negative time” is intriguing, especially how the author broke down the paper’s reasoning. For a lighter topic, I sometimes watch movies online to take a mental break from these dense concepts.
The clarification here about group delay versus any literal reversal of time is the part worth keeping, because the headline does a lot of heavy lifting that the experiment itself does not support. Photon group delay emerging from absorption and re-emission in a transparent medium is a well-understood interference effect, not a signal travelling backwards through causality. What I appreciate about this piece is that it separates the measurement from the metaphor without dismissing the result as uninteresting. For those of us who like turning abstract physics into something tangible, it is a bit like how a complex image can be reduced to a single-layer silhouette; I have used a free printable stencil library for science-communication posters and lab outreach boards, and the process of stripping a concept down to its essential lines is oddly similar to isolating what an experiment actually demonstrates versus what the press release claims.
Good piece, and the point about group delay versus actual time travel is the one most headlines skip. What the experiment measures is a subtle phase effect in a transparent medium, not a reversal of causality, and it helps to keep that distinction sharp before the interpretation runs away with the result. Something similar happens when you follow the citation trail on a dense physics topic: the individual paper is narrow, but the web of linked context around it is what actually teaches you the idea. If you enjoy that kind of link-following, I’ve been killing time with a free Wikipedia link-racing game that turns article-hopping into a timed daily challenge, and it is a surprisingly effective way to learn how connected these concepts are.
The distinction this piece draws between group delay in a transparent medium and any genuine reversal of temporal ordering is the part most headlines skip, so it is refreshing to see it spelled out. What strikes me is how often a precise but narrow measurement gets promoted into a sweeping claim about time itself — the same thing happens whenever people cite raw numbers without asking what the underlying distribution actually looks like. In game communities, for instance, players constantly misread probability tables, which is why a data-driven clan tier list with published roll odds and a calculator tends to settle arguments faster than screenshots ever do. If the effect here is really just a phase shift that looks negative on a plot, the lesson is the same: always check what the metric is measuring before drawing conclusions about reality.
I’m still trying to wrap my head around how those physicists are actually tracking negative time, especially since you already dove into the paper yourself. Sometimes breaking down dense concepts just takes steady practice, which is why I usually turn to quick puzzle drills—similar to how you’d casually check a face score without overcomplicating it. What part of their methodology do you think holds up best?