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-278996
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1.2k

u/HawksRule20 May 02 '26

I think I’m more confused

387

u/Forgotten_Planet May 02 '26

"there's just soup"

147

u/AggressiveSpatula May 02 '26

Well go to the next aisle

88

u/JakeTheHuman83 May 02 '26

It’s more soup!

67

u/Nhobdy May 02 '26

Where are you right now!?

101

u/Whitejj01 May 02 '26

I’m AT SOUP

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u/Flowerpowers May 02 '26

What do you mean you're at soup?!

62

u/Jay-bi-Red May 02 '26

I mean I’m AT the SOUP STORE

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u/Justaway12 May 02 '26

Why are you measuring time at the SOUP store!

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u/Keyboard_Lion May 02 '26

You know what they say.. it’s better to measure time at the soup store than measure soup at the time store!

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u/MarilynMonroeVWade May 02 '26

I nean I'm at soup, but also... I AM soup!

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u/jedi2155 May 04 '26

But you just left to go get soup? How did you get at SOUP before everyone else?

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u/donfrezano May 02 '26

All the way down.

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u/jadedargyle333 May 02 '26

Positive or negative 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

5

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/azrckcrwler May 02 '26

Or maybe it's just a good reminder to go take your meds :P

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u/RespecMyAuthority May 02 '26

There is no soup

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u/Escovaro May 02 '26

It's all in your head

Points at forehead

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u/MogarRage May 02 '26

Normal soup takes 3 min to eat special soup took 1 min to eat

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u/AntalRyder May 02 '26

But there is no spoon tho

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u/Screambloodygore1184 May 02 '26

We’re swimming in primordial soup, we just call it air, Neo.

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u/EnSebastif May 02 '26

Some of it is backwards soup, or something.

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u/injeckshun May 02 '26

That’s a block of cream cheese

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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/ChildishStromboli May 02 '26

Are you sure about that 5 minutes?!?!?!?

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u/Any_Introduction259 May 03 '26

Yesssss ! Love hearing this movie quoted

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u/big_carp May 03 '26

These two youts.

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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/SlightPhilosophy9664 May 04 '26

It's like that guy that could cook Minute Rice in 58 seconds.

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u/Dismal_Buy3580 May 07 '26

This one was the most helpful to me, humorously enough. 

Thank you for the analogy. In this case, is the soup basically quantum foam?

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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/bobpage2 May 03 '26

So the soup aged faster that one time?

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u/3412points May 02 '26

How much time does the person measuring experience over the journey?

I'm guessing 1 minute on the assumption that's how they are measuring how long it took me to walk through, but I'm not 100 that's correct%.

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u/viziroth May 02 '26

I'm just interpreting the metaphor, but that would be my understanding.

the negative time exists to balance out of the length of the journey. it's not actually traveling back in time, but the way to conceptualize it would be if you traveled back in time 2 minutes before doing the 3 minute walk so that you still arrived in 1 minute to the external reference frame, but the walker still experiences 3 minutes.

but what I'm guessing is happening, without digging into the paper (speculating from my surface level understanding of relativity, I'm probably wrong here,) is more of a dialation, where you're actually experiencing 3 minutes in your reference frame while others are experiencing only the 1 minute, but the expression of negative time is how it makes the math work. and this is just a team proving it's happening.

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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/CockItUp May 02 '26

No soup for you.

1

u/BobbalishBobbus May 02 '26

Confused? You won't be after this weeks episode of Soup.

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u/Tacotuesday8 May 02 '26

Some soup too not old. Some soup be.

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u/peoplearecool May 02 '26

No soup for you. One year!

1

u/feverlast May 02 '26

This is how I feel whenever anyone tries to explain relativity to me.

1

u/Juul0712 May 02 '26

No soup for you!

1

u/mrzoops May 02 '26

Yeah why am I traveling through soup and not just stopping to eat?

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u/skillywilly56 May 02 '26

No soup for you!

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u/Druggedhippo May 03 '26 edited May 03 '26

Light isn't a single point, it's a wave function, like a bell curve.

If you fire a light beam at time = 0, ON AVERAGE the "peak" of the bell curve will hit the cloud (soup/wall) at time T, and the peak will exit at time T + T1

But sometimes, it exits at T + T1 - 2.

Why? doesn't that mean it went at the speed of light? It arrived earlier than it entered!

No, because light is a wave, like a bell curve, and T is an average. But it's not just random spread — the atoms (jelly/soup) preferentially absorb the trailing half of the pulse, physically reshaping it so the peak shifts forward. The bell curve gets its tail eaten.

So it's kind of like like your body was "squished/stretched" forward.. but the analogy doesn't perfectly hit because your body isn't a light wave.. or is it?

And it turns out that the size of that shift equals the "group delay" — and near atomic resonance, that group delay can be negative. The experiment has now confirmed this isn't just theoretical: the time the photon spends stored inside an atom before being re-emitted is that same signed value, even when it's negative.

We show that, for transmitted photons, this time is equal to the (spectrally averaged) group delay, even in regimes where the group delay is negative. For scattered photons, the time is given by the sum of an ensemble-averaged group delay and an always-positive Wigner time delay, well known in elastic scattering theory.

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u/Whobob3000 May 03 '26

All of that makes sense, but in English, to a curious idiot who would love to know more, what does that mean? Because I followed you up until you stopped talking about shifting the bell curve away from its trailing tail.

What is “group delay” and why do we care? Is it simply that we can measure the amount the wave gets manipulated and it’s not random or does it mean something else entirely? What is the psychics significance of group delay?

1

u/Wilikersthegreat May 02 '26

No soup for you!

1

u/silian_rail_gun May 02 '26

Go watch the movie “Primer”, then you’ll understand.

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u/Gymrat777 May 02 '26

Me too, and hungry