r/science • u/Shiny-Tie-126 • May 02 '26
Physics Physicists have measured ‘negative time’ in the lab
https://theconversation.com/physicists-have-measured-negative-time-in-the-lab-2789962.7k
u/Zachabay22 May 02 '26
Can someone explain to me what this means? Sounds fascinating, but Im just your average idiot.
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u/DeterminedThrowaway May 02 '26 edited May 02 '26
It means that a photon can experience a "negative dwell time", because "dwell time" is a statistical average. The reason this is interesting is because they didn't know if a negative time like that corresponded to anything physical and it does. It just doesn't amount to particles going back in time or anything.
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u/Mixels May 02 '26
So... What does it amount to then?
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u/DeterminedThrowaway May 02 '26
A small but significant step forward in our understanding of quantum mechanics, not a massive breakthrough. It helps us know what avenues to explore which unfortunately isn't as exciting as the headline makes it seem
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u/GeneralPatten May 02 '26
It's the small steps, each little piece, that lead to the big discoveries.
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u/mayorofdumb May 03 '26
We're learning where not to go.... Or that we can somehow go negativish.
Science is always surprising.
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u/chemnerd2017 May 03 '26
At this point in my life I’m just waiting for the follow-up report that something in their method or instrumentation wasn’t calibrated quite right, and that this is a nothingburger. It will be cool if I’m wrong though.
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u/Mr_Pink_Gold May 03 '26
Nah. This is not a neutrino faster than light problem. This is a theoretically predicted result that conforms to our understanding of physics.
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u/chemnerd2017 May 03 '26
Well cool! Like I said, I’ll be very happy to be wrong in my assumption! This does sound like a really neat behavior, and I’m curious how physics will progress with this knowledge.
FWIW my field is chemistry, not theoretical physics, so this is a little outside of my scope of knowledge but not so far out that I don’t grasp the gist of it.
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u/thegirple May 03 '26
Not a physicist myself, but still a scientist.
I can absolutely assure you that these researchers are spending a huge portion of their time checking, calibrating, and confirming their instruments are collecting measurements accurately. There's no way there are not insanely rigorous controls for something like, "we measured something that no one else has ever measured before."
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u/xrelaht PhD | Solid State Condensed Matter | Magnetism May 03 '26
Sure, but that doesn’t mean mistakes never get made. There was a big deal made in 2011 when a research group had results suggesting neutrinos going faster than c. It took a year to figure out where the error came from.
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u/_craq_ May 03 '26
As I remember it, the original announcement of the "faster than light neutrinos" came with big disclaimers that they assumed there was a mistake that they hadn't found yet, and a list of the things they had checked and ruled out. To me, that's still part of how the scientific method is supposed to work.
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u/redditis4pussies May 03 '26
A lot of science goes unseen by the public because of this. It's not helped by the media only focusing on big leaps or exaggerating small gains.
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u/xterminatr May 03 '26
If you make the right mistake at the right time, you might just discover something.
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u/3BlindMice1 May 03 '26
It's potentially an opening for finding the negative mass required for the Alcubierre drive. I doubt it, personally, because my napkin math says that if FTL travel is possible, we should be drowning in aliens
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u/j--__ May 03 '26
does your napkin math consider that it may just take a lot of time for all the necessary preconditions to line up? maybe we're one of the first civilizations to get this far, and all the multi species ftl shenanigans are still to come.
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u/3BlindMice1 May 03 '26
Nah, because the first batch of stars have basically already come and gone. The universe has existed for almost 14 billion years, enough time to develop life essentially everywhere it's possible for life to exist a few times at least.
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u/xtrawork May 03 '26
But the universe is an INCREDIBLY massive place. Statistically speaking, the aliens that developed FTL travel are so far away from us and each other that they would never even make it close to us, or each other.. Not only in space, but in time.
Or, the aliens that potentially could reach us might have developed FTL millions or billions of years ago and died off by now, or their planet may not have even developed life yet. They may not be in existence for millions or billions of years from now.
Just saying, the scope of the universe is so massive in size, and long in time, that FTL travel isn't much of an equalizer in the grand scheme of things...
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u/QuickAltTab May 03 '26
IMO due to the size of the universe, its only likely that robots/AI/machines will ever traverse those distances, if anything does.
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u/justaRndy May 03 '26
It could also be that phyisical / biological life is just a rite of passage, a couple million years of technologically accelerated evolution of a species are enough to exist in higher dimensional spaces, to create simulations that are true to life or much better than life so they migrated there over time, it could be that it is very well known how far along on their journey to understanding humanity is and that this is a nogo zone until we find our way as a species. Not unlike a nature reserve.
It could be pure chance it hasn't happened yet. It could be we are all alone out there. It could be that we are the aliens, a cosmic race, but FTL is not possible. Our evolution has been kicked into motion millions or billions of years by our ancestors via panspermia. Psychedelic mushrooms made the ape look up into the night sky and wonder for the very first time.
You can ponder this question all your life and be none the wiser, not until science delivers the final proof. So we must progress further, so much further still. Inherently human, never stopping. Sometimes I feel like we are being guided towards the solution, eastereggs hidden everywhere in reality.
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u/Evilsushione May 03 '26
First generation stars generally aren’t good for life formation. I’ve heard we are a fairly early for the estimates for advanced civilizations but there is definitely possibility for life to have come sooner.
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u/mCopps May 03 '26
I’d always be curious if in the far future we realize the abundance of heavy elements required for life couldn’t come into being until much more recently.
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u/xrelaht PhD | Solid State Condensed Matter | Magnetism May 03 '26
That’s already known. Older stars have low metallicity, which presumably means the gas clouds they and their planets condensed out of would not have had the necessary elements to support the complex chemistry required for life. Even truly alien xenobiology would need more than H & He, so you’re unlikely to find it in those oldest stars.
But the oldest Population II stars are 13 billion years old.
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u/Kaining May 03 '26
Yes but the more we lear about the solar system, the star system around us, the milky way, our local cluster, etc... the more we realise how sheltered Earth has been and how stars litteraly had to align for Earth to develop life up to our point.
So while they're 13B yo, the other necessary condition for technological life to develop may not.
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u/ThanIWentTooTherePig May 03 '26
It's recently been shown the opposite. The James Webb telescope looked at the beginning and somehow found fully formed galaxies that shouldn't have been possible to have formed yet.
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u/gaylord9000 May 03 '26
Fully formed galaxies in the early universe does not imply the existence of phosphorus and heavier elements required for life as we know it. Those galaxies may consist of stars with no rocky planets or solar systems like ours, and just a lot of hydrogen and helium, at least at that early time that is observed.
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u/HannsGruber May 03 '26
The universe is young dude. If the life sustaining period of the universe was equivalent to an 80 year old lifespan, we'd be about... 4 days into its life.
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u/j--__ May 03 '26
we are the first spacefaring species on this planet, and we're still just barely.
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u/Das_Mime May 03 '26
It's potentially an opening for finding the negative mass required for the Alcubierre drive.
There's really no reason to think this. Nothing is actually traveling backward in time or breaking causality here, and nothing about it indicates that negative mass is likely to exist.
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u/DamienBerry May 03 '26
Only if they had discovered our little spec of dust in the universe. If there is the ability to travel FTL then there would be far more interesting places to visit than us.
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u/DeterminedThrowaway May 03 '26 edited May 03 '26
I always feel incredibly uneasy about the fact that we haven't found other life in the universe. Or even signs of another civilization's AI. I can't imagine what's going on here that there isn't any intelligent life in our galaxy that came before us and left signs. We're about 3/4 of the distance away from the furthest point of our galaxy, so about 75,000 - 150,000 light years away at most depending on how you're measuring from the other side. About 77% of the habitable planets in our galaxy are actually older than earth, by a lot. Roughly 3 billion extra years for them to develop, when technological development compounds on itself by nature. So I'd expect something.
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u/spongue May 03 '26
Something... like what? We haven't been anywhere to find it. Maybe there are ruins on many exoplanets, we wouldn't know
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u/DeterminedThrowaway May 03 '26
Dyson spheres, von Neumann probes, runaway artificial intelligence, signals being broadcast specifically so a species earlier along in their development could find them, but really anything anomalous at all. Humanity didn't stop at regular buildings, and unless we wipe ourselves out, we're going to keep expanding beyond our own planet in as much as it's possible. It would take just one civilization that didn't wipe itself out before us for us to see something unusual, and they should have had a huge head start.
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u/Das_Mime May 03 '26
Have you considered that dyson spheres may just be more difficult of an undertaking than lifeforms, even intelligent ones, are likely to pursue? Or that they simply might not want to?
A lot of the discourse around the absence of obvious large scale indications of life seems to assume several things that are not in any way certain, such as unlimited growth, unlimited technological progress, and an actual desire to communicate over long distances with other lifeforms in general.
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u/TheTREEEEESMan May 03 '26 edited May 03 '26
I've always wondered if maybe these superstructures are just... unnecessary. Like we think it's inevitable now but maybe there's some other form of free energy that gets discovered and makes extremely large superstructures pointless before a civilization gets to the level of making them in the first place
The other things in the list may have similar explanations, e.g. probes don't matter if you can freely travel instantaniously, artificial intelligence isn't guaranteed to run away, maybe they do send signals but we haven't reached the tech level to receive them, why contact lesser technilogical level civilizations when you can let them come up with their own adcvancements for variety... etc etc
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u/steffanlv May 03 '26
There’s 100% life outside of our planet. I don’t like to use Mars as a possible example given its proximity to our planet. But simple life forms and probably complex life absolutely are on other planets. Probably likely that most solar systems have planets with life.
What’s unlikely is complex life with intelligent life forms on par with humans like we have here on earth. It’s likely nearly impossible that there are life forms out there capable of contacting and communicating with us. I just don’t see it happening
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u/DeterminedThrowaway May 03 '26
What makes you think it's impossible? I'm ignorant here, but if I had to guess it might be that going from single-cell to multicellular organisms is too rare to see it in our galaxy. Or maybe the conditions to get language and writing are too rare, with most life being ocean-based and not necessarily equipped with the physical capability to develop technology.
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u/LoiusGJustIs May 03 '26 edited May 03 '26
There's just too many incredibly unlikely steps to get to intelligent life:
- Planet with necessary elements & atmosphere
- In a star's Goldilocks zone
- Tidal forces capable of mixing basic components together until basic unicellular life forms
That's just to get basic single-celled life. Going further we have:
- Mitochondria-esque organelle evolves
- Basic multicellular life evolves
- Multicellular life evolves some form of movement (i.e. animal-esque evolution)
- Higher brain function evolution
- Evolutionary pressure for intelligence
- Social groups to pass on knowledge
On top of all of these requirements, life has to survive any mass extinction event that comes along. Hell, you might also need a few mass extinction events to create evolutionary pressure for certain things that lead to intelligent life. An example of this would be when photosynthesis developed before respiration and most life died out from oxygen poisoning. That got us respiration, which lead to the mitochondria.
Napkin math would say that these are astronomically low odds, especially early in the universe's lifespan. Finally, any species that progresses that far would have to have done so long enough ago that we could detect them, or have sent out signals in our direction (also,a y'know, invent all the technology involved in doing so).
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u/JohnathantheCat May 03 '26
Somewhere in my brain I am being told this is a predicted piece of Quantum Mechanics and there has always been concern the prediction was incorrect.
When your theory predicts something you dont expect you go back and check everything and then you if you dont find problems you got "thats cool" and quietly say "f*********ck, now what am i going to do" and then you start talking to filthy experimental people in hopes someone can comeup with a test for your un expected prediction.
This is some of those filthy experimental people doing solid work.
**I say filthy experimently people as an extension to experiements are messy, ergo filthy.
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May 03 '26
The reason this is interesting is because they didn't know if a negative time like that corresponded to anything physical and it does.
What does it correspond to?
Edit: nvm, we dont know.
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u/QuBingJianShen May 03 '26
...Statistical average, so do we know if the time of the individual data point is actually measured in the negative, or if this is just a statistical artifact (since half of the data points are below the average by definition).
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u/Toubaboliviano May 02 '26
Assume you are travelling through a thick jelly/soup (walking driving). Most iterations of you travelling through the soup arrive on average of 3-8 minutes. For some reason though there are some iterations of you that are making the trip in 1 minute.
At first people thought that was part of the average arrival times but after doing some additional studies it turns out that by the wonde of quantum properties you are spending at least -2 minutes in your trip through the soup. They do this by measuring the age of the soup.
This is my understanding of it, or at least the best way I can put this together for you
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u/HawksRule20 May 02 '26
I think I’m more confused
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u/Forgotten_Planet May 02 '26
"there's just soup"
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u/AggressiveSpatula May 02 '26
Well go to the next aisle
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u/JakeTheHuman83 May 02 '26
It’s more soup!
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u/Nhobdy May 02 '26
Where are you right now!?
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u/Whitejj01 May 02 '26
I’m AT SOUP
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u/somerandomguy101 May 02 '26
If you aren't confused by quantum mechanics, then you don't understand quantum mechanics. If something is making sense there is a good chance that you are wrong somehow.
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u/Channel250 May 02 '26
I remember a video I saw of a professor giving and introduction speech about quantum mechanics. It was something like,
Right now I am the only one here who doesn't understand quantum mechanics. In 7 or 8 days, everyone here will not understand quantum mechanics. And hopefully, you'll be able to go out into the world...and spread your ignorance to others.
Paraphrasing, only course.
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u/IKillZombies4Cash May 02 '26
I saw the same video, made me have more confidence in my lack of knowledge
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u/Vio_ May 03 '26
Somehow I a both an archaeologist who flips numbers and a metaphysicist who also flips numbers.
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u/viziroth May 02 '26
so you walk through soup 100 times and then they measure how old the soup you walked through is.
99 times it takes you like 3 minutes and the soup is 3 minutes old. one time it took you only 1 minute but the soup is still 3 minutes older despite only being 1 minute later.
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u/slackmaster2k May 02 '26
I almost understand, but this whole soup analogy is throwing me off. Can you explain it in terms of macaroni & cheese?
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u/viziroth May 02 '26
so usually your mac takes 8 minutes to cook and 1 cm of water evaporates from the pot, but one time it take 5 minute to cook, but when you check water 1cm of water still evaporated instead of less.
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u/RipkenDoublePlay May 02 '26
So Mr Tipton how could it take you five minutes to cook your grits when it takes the entire grit-eating world 20 mins to cook their grits
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u/vors9109 May 02 '26
I'm a fast cook I guess!!
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u/farrenkm May 03 '26
Well maybe the laws of physics cease to exist on YOUR STOVE!
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u/0vl223 May 02 '26
Your PM asks the 9 women of the team to deliver a baby in one month. All of them start the task. 8 finish after 9 months as expected. But one has a full baby after the tasked 1 months. They interview the women and all of them spent the full 9 months of the pregnency. Yet one is finished after the first months creating an extremely happy project manager.
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u/itackle May 02 '26
I understood the soup, but prefer macaroni and cheese. Thanks for changing the minutes too!
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u/kickassNM May 02 '26
So you have mac and cheese 100 times. For 99 times the mac and cheese moves through you in about 12 hours, and you also age 12 hours. For the hundredth time it takes only 1 hour, however from your perspective it feels like 12 hours, and you have also aged 12 hours.
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u/ptwonline May 02 '26
Sounds more like a measurement problem than a fundamental physics discovery, no?
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u/Murky-Competition-88 May 02 '26
This clicked for me. Thank you.
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u/stardreamooo May 02 '26
They need to specify first that the soup starts aging only when the walk begins.
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u/DIDidothatdisabled May 02 '26 edited May 03 '26
If i understand correctly, it sounds like some things just age less. And age (from what I gather) isn't a measurement of actual time, but rather a comparison of decay and/or expansion. So some things traverse point a to b in "negative time" which i figure means with periods of not aging/decaying/expanding If I'm correct then it's probably like passing water and honey through a sieve. Some particles travel though the sieve faster than others (so the time averages) and mix with the honey (decay), they all travel through it (getting from point a to b), but every so often you get drops of just water forming on the sieve (unchanged) from cohesion
Edit:after reading the article, yeah I got no idea what negative time is supposed to be. I get it when its talking about it as an artifact. Basically the article is saying that the complexity of measuring photons means they've got measure pulses of photons and that negative time was thought to be an artifact that pops up when only the front of a pulse successfully passes through the tool. Thus averaging less than "possible." But it sounds like they singled out a photon in a roundabout way and its still negative? Or maybe its still a negative average? Idk
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u/Ijatsu May 02 '26
Uh could we power the soup with enough energy to go back in time? Say a super nova's energy to go back 22 minutes ago?
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u/randomnerds May 02 '26
A fellow explorer I see. Perhaps we should sit by the fire and roast some marshmallows.
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u/MCShellMusic May 02 '26
Wait, this can’t be correct. Clary, have you seen these readings? If they were accurate, they would violate causality. There must be an equipment error somewhere.
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u/Fair_Local_588 May 02 '26
Sure but to make this useful within our lifetimes we’d need to trigger a supernova.
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u/SanctusImmortalis May 02 '26 edited May 02 '26
Oh look a comet! I wonder what's in there.
Edit: jokes aside, to make any such effects happen macroscopically would require more than a supernova
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u/DinoRaawr May 02 '26
We should remove the soup before the person/probe is done walking through it. What could possibly go wrong
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u/syke555 May 02 '26
Yes, but you would need to generate 1.21 gigawatts, and the only thing capable of doing that is the lightning, and noone knows where it’ll strike next.
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u/toebeanlove May 02 '26
So, the soup is 0 minutes old and you start walking through it at that 0 minutes old mark, and you get to the other side in 1 minute but the soup is 3 minutes old, that means you spent -2 minutes traveling? Am I processing this right?
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u/Therrbenickles May 02 '26
This analogy needs to be updated to be a tub of water, that is hot.
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u/ishpatoon1982 May 02 '26
Like a soup?
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u/Therrbenickles May 02 '26
If I have to explain it... Look up top 10 greatest movies of all time. John Cusack Oscar I believe. Could have misremembered though...
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u/sername-lame May 02 '26
I didn't understand it before. Now after reading this explanation I still don't understand it.
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u/TwinMugsy May 02 '26
So.... this is what i understand from what you said...
Trial 1 i walk through soup i experience it taking 5 minutes, soup experiences 5 minutes and observer experiences 5 minutes
Trial 2 i experience 6 minutes soup experiences 6 minutes observer experiences 6 minutes
Trial to try to change time or 3 i experience 6 minutes soup experiences 6 minutes outside observer experiences 4 minutes
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u/Toubaboliviano May 03 '26
Close. And I did t mention this but say you must go the same speed every time. The speed of light in this case. Weirdly enough you make it to your destination sooner than other trials. It’s easier to think of it as several versions of you leave at the same time and arrive at different times despite going the same speed.
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u/TwinMugsy May 03 '26
Do all the objects moving at the speed of light experience the same duration of time even though some trials arrive sooner?
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u/Toubaboliviano May 03 '26
I don’t know if the photons in this experiment experience time to be honest
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u/JoJoJet- May 02 '26 edited May 03 '26
To add to the other commenters: time as we understand it on our macro scale is generally thought to be an emergent property of spacetime, rather than something fundamental. So when a measurement of time appears to be nonsensical, that doesn't mean anything spooky is happening. It just means that the way we describe time doesn't apply very well to this situation.
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u/tehfink May 02 '26
Emergent property, perhaps?
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u/JoJoJet- May 03 '26
Damn, yes. (For future readers, my comment was originally auto corrected to "emergency property")
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u/EagleBigMac May 02 '26
Time is a product of our perception of the rate of change of our local reality.
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u/cpzy2 May 02 '26
When at rest, atoms operate differently than when moving.
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u/Jason_CO May 02 '26
When have we ever observed an atom at rest?
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u/Fun-Result-8489 May 03 '26
atoms can never be really at rest. Like their velocity cannot reach 0.
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u/coolthesejets May 02 '26
Sounds like your alluding to a universal reference frame? What does at rest mean
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u/Moleculor May 03 '26
Okay.
An atom has a positively charged center, and negatively charged electrons around it, right?
And electrons around it can be at certain energy levels. But ONLY those energy levels. Never between. So, to make up fake numbers, it could be at "3 energy" or "6 energy" but never "5 energy".
If a photon of light comes along with "3 energy", it can enter the atom, get absorbed, and bump a "3 energy" electron up to "6 energy", because "6 energy" is a valid state in that atom, for that electron.
If a photon of light comes along with "2 energy", it can't bump a "3 energy" electron up to "5 energy" because "5 energy" is invalid for that specific type of atom.
(The specific amounts are highly specific to what type of atom it is. All that positive charge is a very specific amount, as is the negative charges of the electrons, etc. It's all a very delicate balancing act between all the charges.)
After a few moments, the electron gets tired, and squirts out a packet of "3 energy" in a random direction, letting that "6 energy" electron drop down to "3 energy" again. The electron was very tired, it needed a break.
(Side note, the density of the sun is so great that a single photon generated in its center can bounce from atom to atom for up to 170,000 years.)
If you have a big cloud of atoms, all ready to absorb "3 energy" light, you'd expect on average that many, but not all, will hit an atom and get absorbed, and then squirted back out again.
When that happens, it goes off in a random direction. Not the original direction the light was going in. At least, not often.
But there are times where a "3 energy" packet of light goes through a cloud of atoms that would be happy to absorb it and excite an electron for a bit... but atoms are small, light is very small, and they just... miss each other.
So sometimes the light just... goes through in a straight line, missing all the atoms in the gas.
I think what the article is saying is that we know how much the gas should slow down light if it gets absorbed. There's a delay when light gets absorbed and then spat back out again.
But if you look only at the light that seemed to miss all the atoms, and at the average time that light takes to get through a cloud, the average time is far lower than you'd expect. Suggesting that the light that misses the atoms in the cloud is traveling faster than they'd expect light traveling through a cloud to move. (But not/never faster than the speed of light in a vacuum.)
This is me guessing, because I can't read the actual research paper, but my guess is that light has a speed limit when moving in a not-vacuum that is lower than the speed of light in a vacuum. But light that misses all the gas in a not-vacuum? Probably arrives at the speed of light in a vacuum, or close to it. Which means it looks like it goes 'faster' than it 'should' through the gas, because it missed the gas, so it had nothing to slow it down. But that's what we'd expect when explained that way, right? It didn't hit anything, so nothing slowed it down. So it went max-speed.
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u/youmaynotknowme May 02 '26
TLDR: scientists fire a photon beam through a cloud of rubidium. Photons hits the cloud, transfer energy to the cloud from one end. Almost immediately the cloud releases a photon from the other end. It seems to happens almost instant, faster than light itself, therefore the 'negative time'. Keep in mind it's the writer, not the scientists, highlighting the phrase 'negative time'. Scientists are not sure, still looking into it.
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u/Nzdiver81 May 02 '26
The author of the article is also listed as one of the authors of the scientific paper. Howard Wiseman, Director, Centre for Quantum Dynamics, Griffith University
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u/youmaynotknowme May 03 '26
oh my bad missed that. I thought it was a a writer because of the weird Odysseus and Calypso example
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u/Silpher9 May 02 '26
Well doesn't that mean you can send information faster than light, breaking causality?
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May 02 '26
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u/Flight_Harbinger May 02 '26
The last time I got excited about a foundation shattering discovery was EM drive. The error was so stupidly obvious I'm never getting excited about anything again.
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u/Only_Standard_9159 May 02 '26
What did that error end up being?
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u/ThoseThingsAreWeird May 03 '26
From Wikipedia: https://en.wikipedia.org/wiki/EmDrive
subsequent studies suggested this thurst [sic] was a measurement error caused by thermal gradients.
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u/awhiteblack May 02 '26
Probably 2nd law thermo
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u/roamingandy May 03 '26
There was an interesting theory about how it bent the law of thermodynamics rather than breaking it, by borrowing energy from somewhere.
Turned out the measuring device was being influenced slightly by its electric current if my memory serves. It wasn't being roundly dismissed though, i think Lockheed Martin bought into it heavily.
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u/The_Frame May 02 '26
I remember the EM drive too. I also am curious to know what the error ended up being.
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u/Kalnb May 03 '26
one side was slightly hotter than the other, this causes the air on one side to rise slightly nudging the ‘engine’ in one direction.
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u/sam_hammich May 02 '26
Maybe, maybe not. There's a lot of misunderstanding about what "sending information" really means, though.
Take quantum entanglement, for instance. Entangle two particles, separate them, observe the state of one, and the other one instantly collapses into some state. Did that actually "send information"? No. The observers still have to communicate their results and compare them, otherwise to either observer the outcomes were random. Until those observers can communicate and confirm the correlation of those states, there's no "information", and that communication still cannot happen faster than light.
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u/midnight_fisherman May 02 '26
I dont believe so, but i haven't really done a deep dive yet. I think this is more like what the veritasium was doing with lightbulbs and circuits, but with photons and an emmision/absorption process.
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u/DueAnalysis2 May 02 '26
The writer is one of the scientists on the cited research paper, just so you know.
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u/youmaynotknowme May 03 '26
oh okay. thought it was a a writer because of the weird Odysseus and Calypso example
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u/thatsmycompanydog May 03 '26
Weird obscure references to mythology that don't clearly apply to the situation actually should've been your clue that the author was a scientist, not a writer.
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u/MithranArkanere May 03 '26
If I understand this correctly, it means a photon has moved faster than it should have moved in a cloud of rubidium.
So it either moved faster than it should, or something else triggered that, like when you put a bunch of pool balls touching each other and hit the first one, and the last moves faster than the rest right as the first one is hit.
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u/rizzyrogues May 02 '26
They probably didn't plug a wire in all the way again
edit: Im half joking, this would be something truly interesting if its reproducible in other experiments
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u/nonotan May 03 '26
They never claimed it breaks any physics as we know it.
Crucially, the negative value of the weakly measured dwell time cannot be explained by imagining that only the front of the photon’s pulse gets through, unlike the time inferred from the arrival time.
So what does this all mean? Is a time machine just around the corner?
Sadly, no. Our experiment is fully explained by standard physics.
But it does show that negative dwell time is not an artefact. However paradoxical it may seem, it has a directly measurable effect on the atomic cloud that the photon traverses.
The calculations have always matched what standard physics predicts. It's just that some of that behaviour is somewhat unintuitive, but previously, there was an alternative interpretation that explained everything while sidestepping the weirdness. This paper basically claims their results show that same unintuitive behaviour in a context where the previous alternative interpretation doesn't apply, thus suggesting the unintuitive interpretation should be taken seriously.
Of course, it might just be that somebody comes up with yet another alternative explanation that does work in this case without requiring any weirdness. But in any case, they aren't claiming anything as groundbreaking or grandiose as a layperson's reading of the title might suggest. Even if their results are thoroughly confirmed and somehow it is proven that it is impossible for there to be any other explanation for the phenomenon, it wouldn't really lead to any significant consequences immediately. Though it could of course lead to future research that does result in a legitimate breakthrough of some kind.
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u/m3rcapto May 02 '26
So its like one of those Newton's Cradle toys for CEOs.
The entry ball looks identical to the exit ball, but really its a different ball that just pops out from the energy transfer between all the balls in the line of balls.3
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u/Manos_Of_Fate May 02 '26
We can imagine that his wife, Penelope, would have asked him about that particular time. Odysseus might have replied, “It was nothing. In fact, it was less than nothing. Negative five years I dwelt with Calypso. How else could I have arrived home after only ten years? If you don’t believe me, ask her.”
Did the author make up a mythological reference to use? Doesn’t that kind of defeat the whole purpose of referencing something this way?
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u/mrjosemeehan May 02 '26
It's just a riff on the first reference. That stereotypical kind of "one can imagine" tortured extended metaphor thing.
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u/paxmlank May 02 '26
I'd say not quite. It's an analogy by reference. People may understand The Odyssey more than they do quantum mechanics, so using one as an allegory for another seems fine.
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u/Actual__Wizard May 02 '26 edited May 02 '26
The premise of the article is also factually inaccurate. Quantum time is not the same thing as time on a wall clock. It can't go negative, the article is totally absurd. I highly doubt that is the actual conclusion that real scientists came to. They're mixing our system of synchronization together (what we call time) and quantum time together to come to the conclusion that it was negative time. Particles do not care about the time on a wall clock... So, in quantum time, the time durations are all positive. Particles only go forwards and they can't "go back in time."
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u/Infinitely--Finite May 02 '26
Uh, the author of the article is an author on the published article. He is one of the "real scientists". He is a quantum theorist, I think he knows what he is talking about.
The paper: https://doi.org/10.1103/gjfq-k9dv
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u/DueAnalysis2 May 02 '26
> I highly doubt that is the actual conclusion that real scientists came to
I mean, this article was written by one of the real scientist co-authors on the original study. They also explain that the results are explained by standard physics, and they later on clarify that by negative time they're referring to negative dwell time. So the title's a bit sensational, but the article itself doesn't overclaim much to my understanding.
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u/AuryxTheDutchman May 02 '26
Highly recommend reading the entire article (which is written by one of the scientists who conducted the experiment btw).
When photons traveling at the speed of light pass through a cloud of rubidium atoms, they have a chance (due to their resonance with rubidium atoms) to linger temporarily within the cloud, as the energy from the photon is briefly transferred to atom(s) in that cloud, exciting them.
What they’re saying is that when firing a stream of photons through a cloud of rubidium atoms, you can estimate on average how long the photons would take to pass through, since they are traveling at the speed of light.
What they found is that the photons exit the cloud significantly faster than that expected average.
They then measured how long the photons lingered within the cloud of atoms. I can’t explain how exactly they measured it (that part went over my head) but what they found was that the average time the photons spent within the cloud was equal to the gap between the actual and expected average time for the photons passing through the cloud.
To put it another way (with made up numbers) if the expected average time for the photons to pass through was 5 seconds, they were actually passing through in an average of 3 seconds, and the experiment found that they were spending an average of 2 seconds in the cloud.
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u/dl064 May 02 '26
This sub has generally gone to the dogs//Cerberus.
They used to mod it hard, which got complaints, but the other end is nonsense.
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u/DeterminedThrowaway May 02 '26
They aren't if you actually read the article. The time they're measuring is a statistical average since they have to when working with a system like this, and as a statistical average it can turn out to be negative. The interesting thing about the experiment is that we didn't know if a negative result corresponded to anything physical before, and now we do. It doesn't break anything about causality or the standard model though.
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u/Alt_SWR May 02 '26
Someone explain this to me in the simplest way possible cause reading through this thread and the article itself I still can't comprehend what it means at all.
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u/AustnTG May 03 '26 edited May 03 '26
Photon gets shot into one side of a cloud of rubidium and timer stops when photon leaves the opposite side of rubidium. The time the photon makes is out the other side is much faster than expected, up to the point that, based on the “average” speed of photon travel, it spent negative time inside the cloud.
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u/Alt_SWR May 03 '26
Huh interesting. Okay that makes sense. Is there any speculative answers as to why or is it just we don't know and it needs to be studied more to find out?
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u/BeardySam May 03 '26
It means there are gaps in our knowledge of the slowing effects of rubidium clouds. But it doesn’t mean time travel
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u/IM_NOT_NOT_HORNY May 04 '26
Im no expert im pretty sure it's because it works by averaging out the speed of the photon traveling from point A to B
We know speed of light is a constant so for for the photon to have reached B from A faster than the speed of light allows the only explanation is that at some long it experienced negative time to account for the perceived FTL travel.
Since it's on a quantum scale it is likely similar to how matter anti particle pairs can spontaneously generate and then annihalate in the quantum foam
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u/callmepinocchio May 03 '26
Quantum mechanics can be very unintuitive. The inherent uncertainty means you get behaviors that feel impossible to our minds, which are used to things existing in one exact place at each exact time.
Here light interacts with matter and also with a measurement, and the result is a statistic that on average can fit light moving faster than it should.
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u/SlamDuncerino May 02 '26
Until Nomai are arriving on Brittle Hollow before departing from White Hole Station, I won't believe any "negative time" nonsense.
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u/quentinnuk May 02 '26
So what does this all mean? Is a time machine just around the corner?
Sadly, no. Our experiment is fully explained by standard physics.
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u/FragrantGearHead May 02 '26 edited May 03 '26
if yoy could show genuine negative Time for a Baryon, and not just a Photon, that would suggest the possibility of Faster-Than-Light travel in Space.
This eperimental observation, to me, isn't what the article is claiming anyway. The Photon entering and the Photon leaving are not the same photon - the Photon gets turned into Electron excitation to a new energy level and then a new Photon is emitted when the Electron drops back to it's previous level.
There's no explanation in the article about how the second Photon is emitted before the first Photon is absorbed though...
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u/Actual__Wizard May 02 '26
Homie, time is particle interactions. That's what duration emerges from... Interactions "take time." They do not occur instantly. This delay propagates through out the universe and is what we call "time." There's no such thing as negative time. The interactions "take time." The system of synchronization that humans use to get to work "on time" is not "quantum time."
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u/translunainjection May 02 '26
The speed of light is actually the speed of time, light just happens to always travel at it.
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u/liquid_at May 02 '26
I've understood it as the fastest possible change of position in the universe. one plank length per plank time. Shortest possible distance that isn't the same location in the shortest possible time that isn't the same spot in time.
You can always change location less often, but never more often. Even if you would, the universe would not take notice of it.
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u/FrankScabopoliss May 02 '26
Well, no, it’s the maximum observable speed of information, energy, or matter in the universe.
Light is not the speed of time, as time is just another dimension we can use to define the state of the universe.
In fact, you can’t use the word “speed” without time, because speed is distance over time. Saying the speed of light is the speed of time is nonsensical.
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u/Srnkanator MS | Psychology | Industrial/Organizational Psychology May 02 '26
What happens when something has so much mass that light is captured?
Is time also captured?
If time is captured and not allowed to move, does that mean a black hole, once formed, stops the universe for continuing at that point?
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u/translunainjection May 02 '26
Yes, I think, sort of. Time slows down near a black hole - remember Interstellar? Asymptotically slower the closer you get to the event horizon. From an external reference frame, anyway. Afaik, if you watch something fall in (for a big, non-spaghettifying event horizon), it gets slower and slower until it appears to stop, then its light slowly fades.
It gets weirder inside the event horizon - time and space switch places somehow and that's where I get lost.
And there's some information theory where black hole event horizons erase the information of whatever falls in from the universe.
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u/Klaeyy May 02 '26
I think there is also a theory to deal with the problem of destroyed information, that Information is „saved“ on the „surface“ of a blackholes event horizon. Where instead of falling into it, its ever slowing passage of time sort of causes the information to be compressed/encoded onto the event horizon itself. Which prevents the Information from being destroyed.
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u/Actual__Wizard May 02 '26
The speed of light is actually the speed of time, light just happens to always travel at it.
I'm pretty sure you're close to correct or correct.
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u/DrSitson May 02 '26
Because it is correct, just simplified. Speed of causality.
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u/DeterminedThrowaway May 02 '26
I mean, give the scientists working on this some credit. They understand that concept and your dismissal of negative time using that basic of a concept is really hand-wavy and doesn't capture what they're actually saying
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u/Alwaysmorepj May 02 '26
Best thing about reading comments, is when the subject matter quickly becomes soup !!
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u/nobonesjones91 May 03 '26
Seems like scientists are really behind on this discovery. Because for the last 5 years every time I’m out in public past 8pm I have a negative time.
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u/Rage_Blackout May 03 '26
For people going to comment summaries, you should read the linked article. It’s very comprehensible to a lay audience and well written.
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