Light Can Go Backwards Through Time, And This Experiment Proves It

[@astrumspace]

Listen to the Astrum Sleep Space Podcast on your preferred platform by clicking here: www.buzzsprout.com/2250635/share

[@ausnorman8050]

💤

[@thorvo9287]

I can’t find you on apple podcasts. Clicking the link on buzzsprout also just refreshes the page.

[@DigitalBirdie]

Same here. If I click on the Buzzsprout link, the page refreshes but podcast doesn’t appear in Apple Podcasts. I’m running iOS 17.0.2

[@labonazzarena]

Google podcast is a major platform. SoundCloud as well

[@TK-by9pj]

The Apple podcast link is broken I think.

[@bloemundude]

That must be why my mother hated it when I used to turn the lights off and on in quick succession. I risked sending the house back in time. That would explain our dated home decor.

[@marilynjean9689]

🤣

[@nehemiahflorence7133]

Nice😅

[@Byronic19134]

Mother’s intuition is a real thing.

[@honestfxpredator7903]

This could be one of the best KZbin comments ever hahah… congratulations

[@Deeper489]

Thats why she had to slap you to next week to make you catch back up to the present.

[@John-bq9jh]

Einstein liked boating and in his personal papers often refers to him just lying in the boat and dipping his finger in the water and watching the waves spread out. He also would look at others doing the same and noticed that no matter if he was looking at his wave or someone else’s wave he noticed that the waves produced by him or the other travelled at the same speed no matter how fast either boat travelled. He also noticed that no matter how fast he made the boat travel or how fast he dipped his finger in the water or how big of a drop he made the speed of the wave never changed it remained constant. Shortly after he wrote 2 papers. Photoelectric effect and special relativity. Cool eh!!!

[@ChasedoeseverythingATX]

That's awesome, I hadn't heard that before, thanks for sharing!

[@user-wb7nv9ht1g]

What about if you hit the water the water will sort of be a wave and travel faster than the others. I've worked it out, I know how to travel faster than light

[@John-bq9jh]

@@user-wb7nv9ht1g when a photon is created it disturbs space itself and travels an “ether” those pesky particles that come into existence and disappear within the h. I refer to this as quantum foam. Your thinking is like a tidal wave where it goes much faster than the speed of the water wave. But the water speed doesn’t change since both observers are on the tidal wave. Maybe you description is akin to “sub space “ if you watch Star Trek. Lol

[@andrewkaiser7203]

How accurately did he measure the speed of the waves? He didn't. He eyeballed it, because that's all he could do. So he PERCEIVED it to be that way. And that doesn't mean that it was accurate. It's what it LOOKED LIKE to him.

[@John-bq9jh]

@@andrewkaiser7203 seriously?

[@Leonarco333]

It’s a very popular misconception that light acts different when we are watching it. It doesn’t and it doesn’t care. It acts differently when we MEASURE it because in order to measure light we have to interact with it in some way. It’s this interaction that changes the quantum properties of light not the observation.

[@TheKateDash]

Yeah it’s like even when they know it, they still call it “observer/observation”. Why they want to confuse people by saying “observe” instead of “measure”.

[@rafaelgonzalez4175]

@@TheKateDash The vacuum chamber designed for the experiment was to act as if, it was the environment of space. Therefore, observable measure. The confusion is keeping the people thinking time is relative.

[@DJRussellBrian]

the real confusion came when Einstein figured out quantum entanglement... That's when it got weird

[@Leonarco333]

@@DJRussellBrian to be fair most of quantum physics is weird. Entanglement is the part where you’ve twisted your brain in knots and kind of understand the basic rules and then something breaks and you stare unblinking and unmoving at the wall for a couple of hours til someone comes along and hits the reset button.

[@rafaelgonzalez4175]

@@DJRussellBrian Quoted for context. @brianrussell5789 1 day ago the real confusion came when Einstein figured out quantum entanglement... That's when it got weird " It would be true the rare and the few understand entanglement on any microscopic level. It is in my understanding as simple as knowing on the other side of the universe there is another Earth with another me doing the exact same thing, typing to you. My understanding is that the electron in all particles make that connection and communication. Quantum mechanics may reach the point when it can dive into the photon, the electron and even the protons. We are pretty close with protein reconstruction but not there yet.

[@gregorysagegreene]

There's definitely something deeper going on with light, space, and time that is even more fantastic than we can imagine. Maybe we're on the verge of a new century of physics.

[@OmegaVideoGameGod]

It’s beyond our comprehension and that is proof everything in space and beyond is bigger than we could ever imagine

[@420247paul]

light travels at the speed of causality past present and future is the same to light thats what the movie title everything everywhere all at once means.

[@crow2989]

@@420247paulis that movie worth the watch? I was gonna see it but something came up around that time and my family weren’t the type to watch a movie like that. I like Tenet, The Creator, Dune, Valerian, Arrival, Annihilation, etc. for some an idea of what i enjoy

[@helisoma]

there's nothing beyond our comprehension

[@crow2989]

@@helisoma Comprehend a new color

[@alexhatfield2987]

I have to be honest. The quanta phenomena that you are describing is sometimes hard for me to conceptualise. Like light travelling through supercooled sodium atoms, I’ll get there eventually….. What I really love is that our assumptions and understanding is constantly evolving, that there is always something new to discover. As a 62year old who’s lived a life, I can’t tell you how reinvigorated and inspired you make me feel!

[@cabanford]

Sometimes? 😮

[@cueball6969]

Don't put yourself down over it. The quantum world is nigh impossible to conceptualise, given how utterly alien it is to us who evolved in the relativistic world

[@kaboom-zf2bl]

what hard ... put a tennis ball on a string toss it away and dont let go of the string it begins to spin ... the amount it curves is equal to the force of the string on the ball at some angle to the balls thrown direction ... now bend light around a star ... the amount it bends is equal to the gravitational force on the light from the star it is passing meaning the light must slow down by that much to curve its trajectory ... making light NOT a constant ... never was it ... just like sound one just needs a better engine to pass that speed ..

[@tempestive1]

Our brains didn't evolve dealing with such abstract concepts :)

[@philipchantry01]

I have watched and read a lot on the subject of light travelling in a transparent medium, including the Richard Feynman lectures. He stated that light is transmitted by being absorbed by an electron, then retransmitted, at a slight angle. This continues as it passes through the medium, and so the explanation shown in the video is not correct. The absorption and transmission takes time and thus slows the 'photon'. If you cool down the substance to close to absolute zero, then the effect is to slow down the 'photon' to extremes. But what is of note, is that the original photon doesn't exist after being absorbed by the first electron it comes in contact with. A new photon is created with equal properties slightly refracted. I believe Richard Feynman on this as he states in exceptional detail, and for every circumstance. Including refractive and reflective indexes.

[@ryankile5323]

its so annoying when people say it behaves different when you look at it, it doesn't. in order to "look at it" you need to interact with it in some way, ofcourse you get a different result by interacting with it.

[@vd_sv]

Ikr. The worst is when they start to time travel because they cannot comprehend that they’re measuring light with light

[@SupraSav]

You do not effect the operation or completion of a cycle of the experiment, just an observer

[@At_Amsterdam]

EXACTLY! I was about to write this rn thank you. This immediately gives me the impression that these KZbinrs don’t know what they’re talking about. It’s all Brain Greene-speak

If you're measuring only light, then you will see the same result every time. Unless your method of measurement and/or your interpretation are faulty, you will get the same result. I can't believe how even physicists are quite literally projecting.

It's like sticking your hand in a cup of water to feel the temperature: your hand is gonna change the temperature of the water. This method affects the result of your measurement. It's a chronological error: The measurement you get is not a measure of what was there. It's a measurement of the combination of what was there and what you did to measure it. So, observation intrinsically does not change what is there. It's that we measure by affection. We don't have a method of measuring light without making it interact with something. Thus, the resulting measurement will be affected by variables of that interaction.

[@Syntaxxed]

the mexican wave explanation is so good! Thank you for your video. Sometimes it's hard to remember core concepts when you're so overwhelmed with all of the formulas and exercices. This has made it intuitive for me again!

[@SlowMonoxide]

I am so confused right now.... since when has "Mexican" been appended to 'the wave'? It's just "doing the wave," right? I have never heard anyone say that any other way. Weirded me out hearing that in the video

[@NotSoMuchFrankly]

@@SlowMonoxide I've never heard "Mexican" wave, either. I think b/c of his British accent, the word "the" just sounds like "a Mexican". It's possible I just made that up.

[@20xx-mm-dd]

​@@SlowMonoxideit originated in Seattle. It's from the old King Dome days

[@thebulletshow]

​@@SlowMonoxide it refers to minute 6:32 a Mexican wave is basically what the video says, we do it at football matches, it's a human wave lol

[@zacharyjamieson8114]

@@thebulletshoww

[@amantedar123]

I have often wondered about this when I am in a queue of cars waiting for the traffic light to change. I often see the light changes to green long before the first driver moves.😃

[@lowmax4431]

Lol

[@waltersistrunk4200]

That’s because the first driver is texting and doesn’t see the light change. Photons are like that.

[@simonlinser8286]

You're not supposed to go instantly that's how you get t boned

[@FeyIndigoWolf]

One of my biggest pet peeves.

[@FeyIndigoWolf]

@@simonlinser8286 you should be watching the intersection anyway. Even if a car is driving really fast, it's easy to tell if it's going to stop or not.

[@MathIndy]

The Heisenberg uncertainty equation is usually written as (delta-x)(delta-p)>h/2*pi but you can also easily rearrange the Heisenberg equation so that, rather than position and momentum, it instead refers to energy and time. That is (delta-E)(delta-t) on the left side but remember that a photon's frequency is directly proportional to its energy (E=hf). So, in the traditional double slit experiment the delta-x is confined to one of two slits so the uncertainty in the lateral momentum must increase (two probability waves spread out and form a spacial interference pattern). From the (delta-E)(delta-t) point of view if you confine the (delta-t) to two time slits, then a similar thing must happen except now the two uncertainty "waves" are in the E=hf frequency. This creates two interfering frequencies and the associated beat pattern that is observed.

[@manutosis598]

Breaking bad reference!?!?!?!?

[@SprakanaKerum]

​@@manutosis598Don't be corny.

[@jtrujillo866]

Say whaaaat ????

[@SprakanaKerum]

@calencrawford2195 Homer Simpson

[@ВељкоМаксимовић]

Exactly, I thought about the Heisenberg principle too. This would be a correct explanation of the time slit experiment I think. Thanks for your comment!

[@nilsnorden2092]

I've seen so many explanations about the speed of light here on YT. But You explain to me the questions I was so often left with. Thank you from the bottom of my heart - sooooo good!

[@snailnslug3]

It’s a computer simulation my bro.

[@scootergem]

This was one of your all-time best videos. More like this please; less flash and more fact. Bravo!

[@Michaelgrx]

Flash makes cash, bro

[@Twodoor1]

13:50 ok so i might be wrong, but from the photon's perspective it isnt moving through time at all, only space(as it is going at light speed) so wouldnt this mean that perhaps it is able to interact with the other photon as from its perspective they are coexisting at the exact same moment in time?

[@ssm-sf8by]

Photons technically move at infinite speed and do not experience time. If you force a photon to stay still it will decay shortly after. From it's point of view it's birth and destination happen simultaneously. We can only see from the outside therefore we see the speed of light as the one it is traveling at

[@samiteeny9743]

I read the paper and a couple explanatory articles, none of them have photons going back in time. There is “diffraction” through the temporal slit, which alters the frequency (and wavelength) of the light reflected off the pulsing mirror. There is also a very tiny time gap between the first and second pulse. To my understanding, the light is “schmeared” through time. The overlap in this “schmear” over the tiny gap in time between the first and second pulse results in interference. Because the diffraction occurs over the frequency, the end result is that some frequencies are constructively and deconstructively interfering. None of this requires backwards in time effects, which would break causality (which quantum physics obeys). As a point about your time-space diagrams, If you position your receivers and mirrors at higher points in the graph, you will see that light doesn’t need to speed up; it can just slow down instead. This prevents the impression of light going into the past, but preserves the ability for inference. Drawing analogy to the original double slit, photons going through the time slit should have a certain amount of uncertainty as to which “slit” they will go through, but the photon must still obey causality.

[@pparadparadoxy4134]

Spread of a photon through time is rather surprising, although it doesn't violate causality. It means that a tiny part of photon lives in the future (or past), resulting this interference. It does sound what Heisenberg uncertainty principle for energy and time might also suggest, but I am getting a head of myself. Nevertheless he couldn't put receiver and mirror at higher points in the graph, because that would imply that the group velocity of photons in the second beam are less than c.

[@NotSoMuchFrankly]

I'm late to the game but thank you, sir! So often, pop science publications end up confusing and wowing people with click-baity mind benders. I kept thinking of how the materials and fluctuating fields involved could be fouling the results. For one, do we think firing photons through an oscillating (electro-magnetic?) field won't be affected?

[@nickfleming3719]

Thank you, I was just thinking his logic fell apart completely with the space time chart, but looking at all the comments you'd have no idea

[@zakts911]

i was looking for this answer, i don't know what type of crack the author is on, tired of these clickbait trash

[@mohammedabdulhadi4591]

Finally someone understanding thank u

[@ignazachenbach5406]

I'm no scientist myself, but I reckon-given the brevity of a femtosecond-that this interference might be attributable to things like internal refraction within the sensor, or the density of air within the testing chamber. The more refraction is possible, the less it can be ignored…

[@hahahasan]

I would think all that can be controlled for. Perhaps by running the experiments in the reflective and transparent states separately and then doing the femto-second switch and seeing if there is more of an interference in the fast switch case compared to either of the other two cases.

[@bulakhv]

My thoughts are that maybe the first light pulse causes the electrons in the material it reflects off to resonate, and if the next light pulse comes soon enough, it might interact with the residual resonance left by the previous pulse.

[@tcwal]

I was thinking this as well. Ideally they could vary the frequency of the source at such a rate that there is a detectable change between the measurements, then they could tell exactly where/when the interference is coming from by looking at the interference pattern. I would guess it is something to do with the material or some kind of systematic error.

[@CosmicEpiphany]

If you’re no scientist then do you think the scientists had that same thought and accounted for it? I would have to assume as much unless they are dishonest.

[@ignazachenbach5406]

@@CosmicEpiphany You'd be surprised how often researchers fail to take a step back and account for external variables.

[@dakloos316]

Wow you really explained this soo well! I admit, I had to watch it two times to really get an understanding, but that's nothing considering the complexity of this stuff! Well done.

[@yogipete2336]

I'm a first time listener. Fantastic video, great speed of presentation for me as an oldie on a complicated subject matter. I've subscribed to listen to more like this one. Thank you

[@danpowell3953]

This is probably already somewhere else, but wondering if the photon(s) are spread out enough in time to interfere with photons just before are afterward. In other words, the photon is not an instantaneous blip but a wave packet that essentially extends before and after the detectable blip.

[@patrickgisler4061]

Good question! Insert smart insightful comment here.

[@johnmurray3834]

Appears that way displayed on the graph. Makes sense looking at it in 2 dimensions. Hard for me to picture past that

[@LordToxygene]

I was going to ask a similarly related question. How far in time would it need to be before the interference pattern disappears? A second, an hour, a year?

[@Tha_AntiChrist]

In double slit experiment they shot singular photons through and got the same result as shooting multiple through so good idea but I think they have tried it already

[@TheGIGuy-oh5fp]

In the double slit experiment it shows that shooting one photon at a time will still cause an interface pattern , when being observed, meaning it goes through the slits a wave of probability

[@eamonia]

Thanks Alex. I can't _wait_ to check out your new sleepy stuff. I've tried to fall asleep to your content dozens of times but it's too interesting and paced for the curious listener so it didn't work very well but thank you, sincerely, for being such an involved and gracious artist. You're truly one of the greatest insignificant specks in the whole universe.

[@Christopher-N]

It's like the prop on an airplane. The light is reflecting off the prop (the slit) and being received by our eyes (the detector), traveling at the same speed regardless of how fast the prop turns. Yet, as the prop changes speed, it appears to our eyes to be rotating at different rates and even backwards. The change in the slit's state (open or closed), happens much slower than the speed of light.

[@justindressler5992]

Yep exactly or light the timing light used to tune a car. Matter is changing slowly but light is always travelling the same speed. Matter just causes light to change direction and frequency but not speed up or slow down.

[@bobbygetsbanned6049]

That's completely different than photons going back in time to interreact with a photon in the past. The prop never actually goes backwards, it's just an illusion.

[@QUIRK1019]

I would be very interested in learning the physical processes involved in conducting the single photon double slit experiment. I've always wondered how we actually create the single photons, and how we detect them on the target screen or as they pass thru the slits.

[@raam1666]

Reaaaallllyy tiny LEDs No, seriously!

[@reinhardruescher2134]

Also I think we don't detect them going through the slits. If it is measured at that time, the quantum wave collapses and the interference pattern disappears.

[@QUIRK1019]

@@reinhardruescher2134 I get that, but we must have at least tried to detect them going thru the slits in order to know that that collapses the wave.

[@meateaw]

Detection requires interaction, by definition. The double slit only works when the wave form of the photon passes both slits. If the wave is required to interact with a detector, then it collapses onto the detector, imparting a physical change to the detector, and then continues on, no longer exhibiting a wave-like interaction with the slit.

[@BillyViBritannia]

Probably with beam splitter shenanigans after the slits.

[@GRudeger]

I love that in this 4D, as he calls it, graph, we're astonished that light is getting to it's destination "slower" having to travel a greater distance while also getting to it's destination "faster" having to travel a greater distance. What a remarkable demonstration of 4 dimensions! Time = distance traveled divided by speed. Who knew?!

[@pavemedia1828]

in laymen terms what that mean please

[@GRudeger]

@pavemedia1828 He's showing a graph with 2 dimensions while explaining 4. Imagine talking about a cube with only using height and width. Now imagine we're not only missing length but another "thing" we can't even perceive to explain something that would exist on a 4 dimensional plain. It's just made up. Here, I can do it too: Magic is a combined force of will and intelligence and I can control matter with my mind by thinking about it. It's made up. We don't know what the 4th dimension is (yet🤞) and here we are explaining it as if we know anything about it. Another example for you: Do you know anything about nuclear fission? No? Great! Now explain to me how to make an atomic bomb when you know absolutely nothing about it. Doesn't make sense, does it?

[@benjaminshropshire2900]

Regarding the time slit stuff, I think this can be easier to understand if you remember that there is a time/frequency uncertainty (much like the position/momentum uncertainty). As a result, the more accurately you know *when* a photon arrives, the less accurately you know it's frequency. Thus if a photon could have arrived via two different narrow time windows, there are two different frequency distributions that it must exhibit and it's those frequencies that (I think) are interfering. (And yes, that's grossly over simplified.)

[@miikavihersaari3104]

Would the frequency interference pattern disappear in the following experiment? Fire a burst of laser light and measure the frequency distribution. If there is no interference pattern, fire a second burst in quick succession, but if there *is* an interference pattern, don't fire a second burst.

[@benjaminshropshire2900]

@@miikavihersaari3104 IIRC the time scales are such that by the time the interference pattern is detectable (you know if it's their or not) it's >1000x later in time than you would need to do the second burst. The spacing on the bursts might actually be close enough that (regardless of what path you assume) the light won't have reached the detector before the second time-slit closes.

[@benjaminshropshire2900]

@@armandaneshjoo I'm no expert, but I think what's happening is that there is an fundamental uncertainty in the speed being observed. It's not that the photon is going faster than light or that its velocity is chosen from some probability distribution, but rather its velocity *is* a probability distribution. At a guess, what this all boils down to is that you fundamentally can't know what path through space-time the photon took so you can never "see" it going faster than light. Only the combination of effects of all the possibilities can actually be "seen" (i.e. cause something) and that only propagates at the speed of light thus causality isn't violated. Again, just a guess.

[@benjaminshropshire2900]

@@armandaneshjoo I understand that time/frequency uncertainty is a thing and I kinda get how the math works but I have no clue as to *why* that math is. The edge of my expertise passes somewhere short of the question of why the uncertainty of properties is more fundamental that it simply being the physical limits of actually measuring them.

[@benjaminshropshire2900]

@@armandaneshjoo that doesn't explain anything. Why are "quantum fluctuations" fundamentally real rather than a convenient math hack to explain observations? I accept the expert consensus that they are fundamental, but I've never understood how that conclusion was reached in the first place. (FWIW, my curiosity is enough to get me to the point I'm at, but from here I'd rather broaden my knowledge and understanding than deepen it.)

[@greghodges2116]

As a former college physics professor I have a moral quandary over sleeping during a lecture

[@WakenerOne]

Has a morality particle ever been observed by physicists?

[@beamshooter]

@@WakenerOneyeah have you seen oppenheimer

[@theunluckycharm9637]

​@beamshooter I haven't can you explain what happened detail by detail what happened in Oppenheimer

[@OGdadpool]

​@theunluckycharm9637 What did Oppenheimer say to Uranium-235 when he heard how explosive it could be? "You should split." The joke has never really been funny, but it killed back in the day.

[@ScionStorm1]

Probably not as much as a Sleep Studies professor.

[@gabrielgonzales5907]

Thank you very much for the illustrations and animations in this video. I imagine that it involves a lot of work, but we as an audience need them.

[@HanakoSeishin]

I'm not a physicist, but I've heard on PBS Spacetime in relation to Feynman diagrams that a result of an interaction is a sum of all the infinite number of ways it could go, including both possible and impossible ways (impossible exactly as in faster than light / backwards in time). This seems to be very related.

[@deltainfinium869]

I think this is just the proof/application of what pbs spacetime said.

[@robertwilsoniii2048]

​I think it's different. Feynman independently discovered this sams idea with his path integral formulation of QM. A Japanese guy named Satoshi Takoshi (or something like that) also indeoendently came up with a double vector inference method (wave function going both forward and backward in time, considering all possible options, meeting in the middle to determine the only possible actual path and option). ​@@deltainfinium869 ICL did the first experiment to confirm these theories of retrocausality.

[@sergeboisse]

Is it possible to replicate this time slit experiment, but with electrons instead of photons ? If yes, this would be fantastic. If not, this would break down matter-wave duality and that's even more a game-changer.

[@spinnenente]

Double slit also works with electrons. Look it up

[@mygirldarby]

They've done double slit with electrons since the 1920's.

[@dumbledazzjones]

​@@spinnenentethey specifically said the time slit version

[@dumbledazzjones]

​@@mygirldarbythey specifically said the time slit version

[@FuSiionCraft]

@@dumbledazzjones It doesn't change anything since electrons are elemental particles.

[@heathcwalker]

If a photon is a packet of energy that travels along a medium that's always there, then light (or the medium light travels thru, the fabric of space) is always interfering with itself even when there is no packet of energy to observe.

[@chenilleoneil1289]

Why does light travel so much better through water than our atmosphere?

[@gojifan05]

yes

[@here_4_beer]

You are completely wrong. Photons are fully symmetric bosons and do not couple with each other (at least in first order interactions, but higher orders are so rare that it's insignificant). This would violate QED. Also there is no fabric of space, light has no medium. This medium is called ether and was falsified by the Michelson Moley experiment, the same experiment which established Einsteins postulate that light has constant speed for all observers.

[@Stroyer123]

@@chenilleoneil1289 It doesn't. Light travels much faster through our atmosphere than through water. It travels at 299,702,547 meters per second in air and 225,000,000 meters per second through water. It travels roughly 33% faster through air than through water.

[@rafaelgonzalez4175]

@@Stroyer123 How much momentum was used to get light to go that fast? And what was that momentum? Is it the star itself. Just burning away and with each day it just sends particles into our eyes. I also have to ask is ultraviolet light faster? And how does that react to incandescent light?

[@FloraJoannaK]

I'm fascinated by the study and measurement of time. A complete amateur can get glimpses on how physicists see the universe through the ostensibly elementary thing.

[@DougMayhew-ds3ug]

This is a good experiment but the first question I have is could the detector still be ringing from the first light pulse, as the second arrives? Need to see the settling time of the photodetector and related circuit to know if the beat mixing is happening in the detector or related electronics or if it had ample time to settle.

[@RoboticusMusic]

It has something to do with the harmonics and frequency spectrum kind of like FFT. If you switch a sound or light on and off fast enough you get extra harmonics that add to the effect iirc.

[@4DRC_]

What incredible is that the amount that light slows down in vacuum vs air is almost 3 times the outbound velocity of the Voyager spacecraft, and yet in RF engineering we basically treat the difference as so negligable as to calculate in air as vacuum.

[@condealexandervonhasslerra5527]

Nice episode, and really thank you for the audio version. Keep at it!!

[@joji_okami]

love these. i actually use them to sleep since i have a hard time to, and they help so much. thank you for doing these.

[@macysondheim]

Disrespectful. Either wake your lazy *ss up or click off video

[@Dudleymiddleton]

Another fantastic video with beautiful imagery thank you Alex!

[@parentfake306]

4:41 I was just wondering how slow you could get it to get. WOW 0 THAT'S GODLY!!

[@georgechristoforou991]

I always that that freezing down to absolute zero is equivalent to traveling at the speed of light because time would stand still in both cases.

[@biankacosma]

Wait till you see how slow I can get MYSELF 😂

[@t.c.bramblett617]

That just blew my mind and I was wondering how far it could ever be blown. Turns out, it was blown larger over a very small interval in time, blowing it even more than it should ha ve!

[@nathanmoore101]

Trying taking acid. U haven't even begun to to blow.

[@Noconstitutionfordemocrats1]

Instructions unclear: took hydrochloric acid, everything but my mind was blown.

[@doughboywhine]

A fan of drama I see

[@a-walpatches6460]

@@nathanmoore101 Try taking DMT!

[@OfficialMarlo]

You explain things so well. Very well done.

[@keneola]

Thank you! thank you! I heard of this experiment but it was never explained to the point I felt understanding but your explanation was remarkable!

[@musicalBurr]

This is very exciting to learn about. Thanks for posting about this mind-bending experiment. Absolutely amazing!

[@JPowerMMA]

Nicely visualized. Well spoken as well. Not many physics channels on this level

[@TheEveryDayC]

This makes me think that it isn't a problem of light legitimately travelling backward through time, but with our understanding of what light is being flawed in such a way that with our understanding, it appears to arrive faster than light. I don't understand enough of physics or this particular subject to know, but if I were to throw my undereducated idea at it, I would start to think that light is a probabilistically appearing function of something that we just don't know about yet, and that interference patterns are just the natural way that something's made apparent to us with the way these experiments are set up. We just don't know quite what we're looking at.

[@GraveUypo]

No joke i feel like i got a fundamental understanding that i have always missed about the size of things in the time axis. i always assumed we were all points in the time axis, but the way light behaves here suggests it is not a point, but rather a small blob. which means it simultaneously exists in the past, present and future, however small slice of those it may be. that's amazing.

[@xxportalxx.]

Yeah well you know how in the quantum regime an object's position is actually blurred? It's a probability distribution of where you're likely to find it, and you can only make that so narrow before you run into heisenberg uncertainty. This same thing applies to time, an object's position in time is similarly a probability distribution, i.e. when you're likely to see it (but you can't say exactly when).

[@dddgx05]

DeltaE * Deltat >= hbar/2

[@xxportalxx.]

@@dddgx05 indubitably

[@wilderbeast9368]

You seem to be describing the Heisenberg Uncertainty Principle, I implore you research further because it is truly gripping!

[@GraveUypo]

@@wilderbeast9368 i already know about that, but its not quite what im seeing here. that would imply that the light would be one small point in that blob of possibilities, but im saying its behaving like it is the entire temporal blob at once, otherwise it would not interact with its past self, and would just collapse into a single one of its possible temporal points instead when observed. nyway, its just mine own thoughts and interpretations of this phenomenon, i could just as well be interpreting it wrong.

[@milodemoray]

Thanks for this Alex. The idea you present here makes perfect sense while expanding on the original double slit experiment.

[@Congruesome]

“It is impossible to travel faster than light, and undesirable, as one’s hat keeps blowing off.” -Woody Allen

[@ListenToMe180]

so the light delivers a good blow job 🤔

[@Heart0rHead]

14:09 this resembles a video of a lightning in a super slow motion - it does the same, various branches search for shortest way to grounded point to make a discharge.

[@offgridphilosophy7959]

I love your channel bro! No click bait and ai generated narration! Your voice and accent is easy on the ears and great for heloing people digest the information! ❤

[@filonin2]

The title of this video is itself click bait. Obviously an ai bot comment.

[@thisisafox1961]

I don't know what you mean about no clickbait. The thumbnails and titles of this channel have gotten much more clickbaity over the past half year or so.

[@Richie-Stefon-King]

@@thisisafox1961 adding a little extra time to the graphics/imaging for the thumbnail doesn't necessarily make it clickbait or "more clickbaity" - that's subjective. that said, even if it were clickbait, the obvious goal is for potential & repeat viewers to view your content. i wouldn't have watched his videos if he used a boring or less catchy thumbnail. this is a great channel, we're not hassled for money or endless donations. great information is provided and he clearly in invests in his content for his viewers.

[@subsume7904]

​@@thisisafox1961how?? He literally explains how light goes backwards through time to find the the most optimal path in this video, it isn't click bait if he actually does the thing

[@ChaohsiangChen]

As a person who has the credential to talk and critique on this topic, I am astonished that this paper is peer reviewed and published on Nature Physics. The conflating of time and frequency domain is astonishing for anyone who studied signal and systems in college.

[@Aturnadagar]

The indium-tin oxide does not stop been reflective at the speed of light. So is not like 1 or 0. What you see when at the end of the experiment is not going faster than speed or traveling back in time, is just that the First pulse is still been partially reflecting at a lower intensity at the moment the second is activated to be reflected.

[@lihtan]

That's really interesting! The thing I get from the time slit experiment, is that because the laser beam is coherent light, it's automatically quantum entangled with itself. This would be why it would leave interference artifacts that can be detected across time.

[@Adventist1997]

That would break the concept on "when" the universe started. 😂

[@ishaalimtiaz6715]

explain that to a fool (me)

[@TheMrJizzus]

I am amazed by this discovery and how it was explained in such a beautiful way. Thank you so much

[@juliopaveif]

Jesus christ. This gave me Goosebumps. It somehow makes sense and feels impossible

[@Daytruin]

light and other subatomic particles seem to have a kind of retcon/ hash check/edit ability to make up for the breaking of continuity within the world we live in. The ability to shortcut time by being both a wave at the same time as a particle is astounding. every day i'm amazed by our leaps in understanding, and to think mankind not too long ago was living in caves and small huts only being able to make up gods to explain the stars in the sky. If nothing else is worth it in life, this world and beyond it is so fascinating and i'm glad i get to witness it along with each of all you others of the human race. We all are lucky to see such marvels, so make sure you take time out to look back on your life and despite any ugliness just appreciate the marvel that is the universe and even our earth.

[@jacobostapowicz8188]

'Make up gods to explain the stars in the sky' Now they just make up magical naturalistic origin stories where time is the hero and can build all things, design universes and understand the complexity of biological life and invent flight and locomotion. The universe and biological life is obviously designed, stop pretending that physics and chemistry knows how to design and build.

[@logansmall3340]

Love this style, hope there are many more to come!

[@AnonNopleb]

If the experiment is analogous to the spatial double-slit experiment, that means when actually trying to measure any of these "feelers" by whatever method we might come up with in the future, the interference pattern vanishes as well.

[@kylaxial]

@@sIXXIsDesigns reality is sometimes weirder than fiction

[@JohnnyWednesday]

@@sIXXIsDesigns - if reality is a simulation then that's exactly what would happen as an optimization - no point in simulating things that the subject matter can't see at full quality.

[@nicodesmidt4034]

It's the luminiferous aether 🙂

[@weylinstoeppelmann9858]

@@sIXXIsDesigns Observation is interactive, it's destructive. When trying to view the most fundamental forces, there is no other way to measure it than to change it. It's not like watching a ball fly by and having no effect on it because your eyes absorb the light that bounced off of it, you're trying to look at the very essence of looking lol

[@thesenamesaretaken]

​@@sIXXIsDesignsyou're well within your rights to doubt quantum physics, but the problem is finding a theory which matches its explanatory power. Bohm's approach is an option but afaik that only gets you as far as the 1950s because nobody has figured out a Bohmian analogue of QFT.

[@Maisonier]

What if, in Lene Hau's experiment, we were to put a person inside a transparent capsule (obviously with oxygen and ideal conditions for the observer) and around that capsule, another container filled with those sodium atoms that stop light? What would the person inside see? Theoretically and hypothetically, could someone travel to the future inside that capsule?

[@tcwal]

They would see nothing until the cloud was warmed enough to be permeable again, then they would see the light shining through. Time would be exactly the same.

[@SuputraBharathi]

​@@tcwalPerfect 10/10 for that comment

[@Bhatt_Hole]

They'd end up in hell, cause this here be the DEVILS WORK!

[@Mindbulletz]

They would see nothing, then perhaps get enough retinal damage to continue to see nothing.

[@alfadog67]

I think the nearly frozen gas simply holds the electromagnetic energy in its higher-energy electron states, and when it cools, the waves are again released, not dissimilar to a tape recorder. If we were inside that cloud in a capsule, we would see atoms freezing in their higher-energy states as they absorb the EM energy of light. I doubt we'd notice from inside the capsule; we'd see whatever frozen ionized gas looks like.

[@paulfrindle7144]

I can think of some important concepts we should mention when looking at this experiment? Firstly light (as for any other wave signal) must be a perfect sinewave function to present as a perfect single frequency, or colour in the case of light. This means that for a perfect sinewave to exist (i.e. with no harmonics), it must have started at the beginning of time and gone on to infinity to be totally perfect - and be measured in it's entirety. Anything we do to measure it in our constrained time means that we have no choice but to start and finish the measurement in finite time. This means that our measurement in itself causes an error which will create harmonics. This is why we use 'windowing' in signal processing to reduce the fall out when analysing signal (i.e. fading in and fading out again, by various means etc.). So the introduction of harmonic lines in the light wave after being passed through the switchable reflector can be adequately explained by the light having been subjected to a foreshortening due to the reflector being turned on and off very quickly. BTW this also means that we cannot think of a photon as a discrete 'packet of energy' by dint of wavelengths being 'faded and and out' like his diagram suggests - since this would also cause a frequency spread where no light could ever truly occupy only a single frequency. This simple depiction of bursts of waves must be wrong! The second thing worth considering is that if light is moving at the speed of light (in a vacuum) it does not experience time at all - because of complete time dilation! This means that it apparently ONLY experiences time IF we must think of it as a discrete particle of energy. The only way we can counter this wave / particle duality notion is to state that a photon has no mass, because anything with mass would require infinite energy to reach the speed of light. This means that the photon is apparently the only thing which can transport energy from one place to another that has NO mass! Hmm... Anyway give all of the above - it's not a great stretch of the imagination to understand that gating light 'signals' will cause frequency spread (just like any other signal). And since light as a wave itself does not experience the passage of time at all, the periods in 'our time' the light mirrors happen to be opened and closed is totally irrelevant... Food for thought?

[@ddezzko]

Nevertheless, hypothetically if it was a light signal with single frequency then as @MathIndy in the comment section mentioned, the increase in uncertainty in energy due to reduced uncertainty in time would certainly explain the results

[@paulfrindle7144]

@@ddezzko In many ways that amounts to the same concept I was talking about - but sort of looked at the other way around? Uncertainty in actual frequency spread is increased by the briefer period we try to measure it in time at our level? In other words, gating the measurement of any wave form creates sidebands in the frequency domain. Since light is massless when considered as a particle, it's energy is transferred only due to its momentum. So the total energy is preserved even if it is chopped up into periods over a wider spectrum in our resting time frame.

[@vintagelady1]

Your ability to use analogies is simply genius, particularly the line of Light People doing the wave & lightning seeking the shortest path to earth.. Perhaps photons are something we cannot perceive or conceive of & we should call their structure "wavicles?" Or "partiwaves?" The latter sounds like more fun, at least for the photons.

[@Noconstitutionfordemocrats1]

Punch an ooblick. Is it solid or liquid? It's a lolid or sliquid.

[@cyberfunk3793]

Except the claim with the mexican wave was wrong. Of course information can be passed faster then the group are walking when they are doing the mexican wave.

[@garyfilmer382]

Great animations, light may travel faster, or slower, and is a wave, and a particle, in a quanta, a packet, being both the wave and the photon particle, travelling by the path of least resistance, and in space, light is actually bent too…compelling, mind blowing, and enigmatic, the story of light is forever fascinating!

[@infernalsorcery7923]

Light is not bent, the tangential velocity of light passing near massive objects is altered by the distortion those objects cause in spacetime, bending the path the light is taking, not the light itself

[@lokikuro4236]

The way I am seeing this is like this. Light travels through the electromagnetic field as a wave. Meaning this photon is influencing the EM field as it is propagating. The moment the screen closes and lets light pass through is “blocking “ this propagation for a brief moment. This time (of blocking/passing light through the filter) is orders of magnitude higher than the propagation of the EM ( which is the same as the speed of light in that medium). Because the EM field of T1 and T2 ( before and after the filter was turned on and off) these EM fields are overlapping therefore interference is being observed. A way to increase/decrease the interference pattern would be to increase/decrease the time the filter flickers. Another way would be to increase the area surface of the filter.

[@bloodyfluffybunny7411]

can we combine the super cooled slow light experiment with the time/reflective double slit ? maybe the testing of routes goes way to fast for us to detect under normal light speed conditions cus it might be a single photon that tests the way or maybe even only a carrier wave without any visible light well many more things to tests and double check in the coming future

[@MeinCouch123]

This is a genius idea

[@bloodyfluffybunny7411]

@@MeinCouch123 probably amounts to nothing but it's worth a try just to know for sure

[@francomckellar]

Please Mr Astrum, would you consider doing additional videos on the planets? I have watched them all over and over again. I need more!

[@cbsaulren]

I've always wondered if the presumed expansion rate of the universe could be explained not through dark matter, but rather the varying of what we consider constants, either the speed of light or time or both

[@thetwodimensions7588]

Great video as always, keep up the educational, and the bizarre theories of physics!

[@StephanBuchin]

Wow, this is so clearly explained. So much better than all the videos about this topic I have watched so far.

[@RobertHershkowitz]

Best one I've ever seen.thanks once more to cell phone company's towers men and women who maintain these. In fact all the workers.

[@ZemikianUchiha]

This sounds incredible, but how can we be sure there were no other material effects of the reflector/system that might have responded differently under different input circumstances?

[@zaku28]

Definitely a cool experiment but I agree. hopefully more tests are conducted using slight variations that end up narrowing down any alternate possibilities (or revealing the true cause/more information on why it happens)

[@clearercarton]

More of these sleep episodes please

[@javadrezaee]

😂😂😂

[@alexhatfield2987]

That’s an interesting and good question, Jay. The answer would probably change, every day I look back over my life. You have a lovely looking family in your profile photo. I hope you all have as happy a life, as any of us can.

[@pepe6666]

i think it needs clarification that 'when light hits at a different angle, its frequency changes' only applies to this diagram. meaning the same light wave but with a faster wave velocity will have its crests/valleys hit the receiver plate more frequently. how light actually behaves when hitting a surface at an angle in geometry is actually complicated. the distance in time between light pulses should be mentioned i think. light has a certain speed through time and speed through space. but the photon experiences no time. like you show its taking the diagonal in this experiment. light either interfering or not interfering with itself would be a function of the delay time between pulses and the distance of the whole apparatus. i think some aspects of light's result on something can be thought of if the whole setup occurred in an instantaneous speed of light. of if the distance it travelled shrunk to zero.

[@Mikerumball]

Dude this channel is brilliant.

[@dhavalpanchal4856]

Since light is only the visible spectrum, it would be interesting to know how this works across all EM spectrum such as xrays, microwaves, radio ways, UV, Infrared, gamma, alpha, etc

[@clintanderson4591]

This was the video that made me subscribe. Looking Glass Universe was also toying around with the speed of light recently too--combining with Grant from 3BlueOneBrown to make this understandable. Great job here from you, Alex. You three need to collaborate to finish this visualization off more, then form a group to talk about stuff. Veritasium, Minute Physics, PBS SpaceTime, sabine hossenfelder, Nick Lucid, and others are all solid, but you three need to combine like Voltron to form a group to catch all of us up from what we missed in high school. Add Eugene Khutoryansky to the mix too--he didn't talk about light speed (that I know of), but bring him in and present the ultimate presentation.

[@xavaloy]

So so so good... absolutely loved the video ❤ Seems things don't just happen, they are manifested and calculated into reality... 😮

[@a.m.9357]

Of all the stuff with quantum physics, I find 'light' to be the most beautiful, difficult, elegant, enigmatic and mysterious. Forget gravity, space-time or subatomic particles. Light is what holds the secrets of the universe.

[@PRINCESSMUYUNDA]

Yeah it's literally influenced a lot in the universe... It's like now everything we see is seemingly in the past or behind light you know in other words seemingly beyond time we experience

[@Alex-vm9ug]

seems to be a major oversight in this study, and that is a pretty simple one, indium tin oxide cannot change state faster than the speed of light... the entire phenomenon of the experiment can be explained by light traveling through the indium during is phase change

[@jgunther3398]

i think the reflector is a lot more complicated than illustrated here, multiple elements so on. what i want to know is how to make a femtosecond timer to control it with!

[@janet4900]

Maybe it's really a continuous wave (not a particle), but it's interacting with something else (the ether) that makes it's activity zero, until it picks back up again, appearing to be a particle. What I'm trying to say is that maybe it's interreacting with something that makes up the fabric of space, so it has to move cyclical. I also find it interesting that theoretically, things can get infinitely small, just as they can get infinitely large.

[@jeffarsenault4606]

If light slows thru a certain medium, when exiting, it must accelerate at mind boggling speed, like 0 to 60 mph of a car in pico seconds !!

[@funnycatvideos5490]

It's not traveling its uses the medium for propagation. Water is not traveling in The wave energy is moving through it. We are describing energy not waves. Of course the ether has to exist.

[@janet4900]

@@funnycatvideos5490 Do you think a particle is just a disturbance in the field (of energy)?

[@tinabealtine7152]

Wow that analogy with lightning is really helpful! Thank you for an amazing video.

[@devilmaker28]

What if you steadily increased the gap in time? Would there come a point where the frequency no longer seemed to have an interference pattern? Based on my current understanding of the experiment, I can't imagine that if you were to increase the time gap by several seconds (or a minute, or any other longer length of time) that you would keep seeing an interference pattern. Therefore, you might be able to calculate an upper bound to this apparent faster-than-light speed limit?

[@lih3391]

Theres probably no upper bound, just a point where you can't measure it anymore, it would be a fuzzy boundary, like everything else in QM

[@TlalocTemporal]

​@@lih3391-- "Quantum" literally means "Discreet Packet". Quantum mechanics is all about the parts that aren't fuzzy, as opposed to classical mechanics where everything is mathematically perfect gradients or edges.

[@lih3391]

@@TlalocTemporal thats a good point, I think I was thinking about it like moving the two slits in a double slit experiment apart. Theres a point when they don't interfere, but it might be because your detector is not sensitive enough. If theres interference in the time direction, and "interference" has the same meaning as before, it should be similar. I'm not sure, but I think the uncertainty principle has something to do with the wave nature of particles right? That's the fuzziness I was talking about.

[@TlalocTemporal]

@@lih3391 -- Ah, ok, so less "chaos of random" and more "normal distribution", I see. So for the normal DSE, increasing the gap width between slits means decreasing fringe spacing (the distance between peaks of the interference pattern), with a larger distance from the slits to the detector and a larger wavelength increasing the fringe spacing. In the Time-based DSE, the width between slits is the time between reflections, so I think we'd expect less wavelength diversion as the delay gets larger, but a larger total difference in wavelength? What would the larger wavelength from the normal experiment be equivalent to though, amplitude? What component of the probability wave is having an effect through time? I wonder if you could do some kind of quantum eraser with this, changing the delay based on how the first reflection behaves? If some of this light appears to move faster than c, and there's no universal simultaneity, can we get light appearing to go back in time?

[@ashishsavadia]

My feeling is small imperfections/density variation of the instrument environment material (not purely vacuum) through which the light is travelling can cause the light to reach at different point on time and interfere with the previous one specifically when we are talking about accuracy of femto seconds..

[@unowenwasholo]

Certainly one of those things where as a layman, you can't help but to wonder, "But wait, surely there's room for error at these extremely sensitive measurements." At the same time, one has to assume that these scientists are experts and aware of such simple things.

[@greegorygrimlee5487]

I'd imagine they try to rule that out as much as possible. Like mathematically predicting the interference pattern and how it changes when the source frequency or the 'distance' between pulses is varied. And replication would tend to ruke out material imperfections too. Like the double slit experiment has been done millions of times with millions of different slits/light sources/etc and yet the same interference is observed.

[@barthennin6088]

This reminds me of another fascinating video I saw where it was explained that we only know the "round trip average" speed of light is 'c' but that it's speed may vary during the trip. The average is always 'c' but the speed to vs the speed from in the round trip journey may differ. There is nothing proving otherwise.

[@rtrThanos]

Black holes are so powerful that nothing escapes, yet jets of energy are constantly escaping. Nobody has been able to explain this.

[@Crikey420]

Taco Bell

[@galaxies2go]

Try research the electric universe theory…

[@astronomyphilly]

Well, I'm going to assume you've it actually looked because if you had, you'd find it's been well explained, tested and proven for quite some time now. I teach it every week. Do some actual research pal, don't listen to the spaz below and no, KZbin doesn't count.

[@dannydetonator]

Nearly as ignorant and dumb take of anything, as the 'electric universe' conspiracy reply above. (If anyone wonders, it's not an 'energy' jet per se: and matter escaping doesn't come from inside the event horizon, so its neither claims).

[@wassupnomesayin]

Black holes are still theory, not anywhere near fact.

[@tokesalotta1521]

Apparently, the first time people outside of America ever saw the "wave" was during Mexican soccer games. It started in America though, and worked its way down to Mexico

[@jgunther3398]

i kind of remember the first game it happened at and the announcers remarking about it. couldn't tell you when or where it was though

[@jakegrist8487]

Energy, confined in space, is mass. Mass, unconfined, is energy. I would propose that any talk about light moving slower than C is simply an observation of energy interacting with the Higgs field, and so partaking in a degree of mass. I would assert that C, the speed of causality, is the critical rate to be concerned with - not the apparent velocity of light, or gravitational waves, or any other form of energy. Causality itself should be absolutely constant, as it is a fundamental property of spacetime.

[@waveparticleman]

Regarding the time slit experiment, how can it be ruled out that a residual vibration in the reflective surface caused by the first light pulse is not causing the interference in the subsequent light wave?

[@steevehoyoufat9155]

"Light travels at the speed of light..." One of the great thinkers of our time.

[@OmniOmega]

"Light travels the path of least time" literally a multidimensional circuit. As an EE, this made me think of a lot of ways this can be used, a little scary though.

[@RB-fp8hn]

How do you produce such amazing videos on mind-boggling physics so often? Teach us, sensei!

[@astrumspace]

Some very bright and talented people helped me make them :)

[@misterlyle.]

Your vocal delivery for each program is highly effective. So if it is you we are hearing, that part is your natural talent.@@astrumspace

[@maestroaxeman]

​@@astrumspace This is one of the reasons I totally respect you & your channel, Alex🤓🙏 Humility & those like attributes shine through because you make sure to note credit to your team & your colleagues.

[@MiguelSilva-vq6qe]

He is jhon titor, a time traveler

[@Li.Siyuan]

This was really interesting and very well explained, Alex. Could the interference not be a simple result of a non-point like fluctuation in the photo's quantum field? This would mean that there would be a non-zero chance of a second photon being able to interfere with one sent ahead several femto-seconds ahead of the second which would, indeed mean that the interference was happening before the light hit the In2O5Sn film. Having said that, it also leaves several other questions regarding interference with multiple photos all travelling together, I suppose. Just a thought.

[@Rubensgardens.Skogsmuseum]

To begin with the light never went superluminal speed. Hence, I think this is either a quantum effect or detector saturation.

[@o__o.6212]

Does this singularly disprove all of our understanding of the time-reliance of causality? And the whole philosophy of presentism? Because I’m having a bit of an existential crisis over here, yet I don’t see physicists all talking about this or philosophers taking up arms. Is there something I’m missing? Because to me this seems like the first experiment in history proving time travel, which opens up a gigantic can of worms on *everything*.

[@BrownCuttingwood]

What can you do. If time travel is widely available to the future, what would it change our life for us, their past. They are going to set laws and rules like the peace after he who invented the Atomic Bombs.

[@deathchilde]

Like how in order for our sight, "sight" doesn't come out from our eyes to the object but the other way around. Light lands on object and bounces off to our eyes. So to measure something, it's like taking a different light and colliding them with normal light which changes the trajectory

[@taijaroennaparat9874]

i had a brief look at the paper you cited. there is no mention of light going backwards in time or any thing of the sort in other articles about this experiment. i just don't see how the argument that its travel back in time make sense, since speed of light is invariant in all reference frame. i don't know if this logic is sounds, but if you consider the same space time diagram and the fact that light has a constant speed in any frame, to get interference it simply that the distance between the detector and laser is shorten - hence length contraction from special relativity .

[@xizilionyizzexeliqer3897]

It's humans being humans again it doesn't make sense whether you are white english or not.

[@WILLIAMMALO-kv5gz]

So much I do not as yet understand. Thanks for this humbling video.

[@chekote]

This sounds exactly like a video I watched (I think it was science asylum) where they talked about how light bounced off a mirror. IIRC, they said how it took all paths, and the wave constructively interferes with itself to give the typical reflective path we perceive. I wonder if all waves propagate in all directions of space time (not just space) and the destructive interference is what creates the arrow of time? 🤔

[@kaboom-zf2bl]

first Space ... Time is a man made measuring device to compare dissimilar things over a similar interval ... TIME doesnt exist even our brains dont use time ... we see at 24 images per moment ... motion is just more images per moment of the same thing with slight changes .... a flip book ... this is how video works by sending many pictures per moment in front of your vision to make things appear to move ... Time is nothing more than a measuring tape

[@kaboom-zf2bl]

the laser split experiment also needs the reflective surface slits to be looked at as they will also bend the light to some degree and will be a primary reason for the light to become diffuse ... ignoring it you preload your error by at least 5 % ....

[@renoallstate4573]

Please make a video of what it would look like for two observers traveling away from each other at 60% the speed of light, then toward each other, and then add a central third observer

[@haakoflo]

Light has to comply with Heisenberg's Uncertainty Principle, like all other matter, meaning dE*dt >= hbar/(4pi). That even applies to a single "Monochromatic" light pulse, down to individual photons. The more precise the frequency (= E/h for photons), the less precise is its time, meaning it exists over some period of time. If the screen has a shutter speed shorter than the time size of the photon, the photon is "chopped in two" in a way that is pretty similar to a double slit experiment. Fundamentally, this is just one of the consequences of the wave aspect of any elementary particle. Photons do not (when travelling) even HAVE a specific time where they exist. As they travel, they form a wave packet not unlike a single note played on a piano. A photon that has a relatively precise position in Energy-Space will look similar to a drawn out sine wave in Time-Space, since these are Fourier transforms of each other. A single photon will, if it has a precise energy, have a large numbers of periods (peaks) in this sine wave. Removing part of the Time-Space contribution to the photon will, when Fourier transforming it back to Energy Space, cause some kind of clipping effect. In fact, the detector is in effect doing precisely this Fourier transform, as it's built to be sensitive to the energy rather than the time of the arriving photons. For anyone into audio, you can get the same effect by playing a sine wave through an amplifier or speaker beyond it's ability, where it will also "clip" the peaks of each period, which then takes the output from a clean sine wave to multi-frequency noise. Furthermore, the reason we notice this, is because the cochlea of our ears basically does a fourier transform of the sound, taking it from a time-amplitude-space to a frequency-amplitude-space. (We can easily tell a 1000Hz note from a 2000Hz note, but it's near impossible to detect temporal jitter in the order of 0.0005s).

[@corina753]

I tried to understand your comment, but I can't say I understood it 100%. In the end I have a stupid question, did the experiment in the video prove in some way that light can travel back in time or the conclusion at which they arrived was not the only possible solution and there are other more plausible. And in your opinion, is there something that can travel back in time?

[@haakoflo]

@@corina753 As far as we know INFORMATION cannot travel back in time, which is also said in the video. That would include everything we care about, including anything with DNA inside it. MAYBE there is some way to warp space time enough (such as through a wormhole) to create an exception, but as far as we know Quantum Mechanics cannot do it.

[@Primordialtruth666]

Info can not travel back in time lol no but it can be exposed to do so, so your proved wrong very simply. Bud. ​@haakoflo

[@haakoflo]

@@Primordialtruth666 If you think I'm wrong about something above, please provide details about why/how/where. Are there any experiments (real or hypothetical) that can send information back in time? As far as I can tell, the experiment in the video is simply a confirmation of Quantum Mechanics, which treats each Photon as a wave. It only becomes strange when you think of photons as point-like particles. EDIT: Btw, there seems to be an error in the video. The video describes a direct interaction between two photons. But in the original article, the first photon (or pulse of photons) primes a medium in a way that causes the medium to become a time slit. Then probe photons are fired on that medium that have their wave packets chopped up in time, these photons then interact with themselves across time before hitting the detector. In other words, this is no different from other experiments where single photons can have phase velocities faster than the speed of light (c), but where the wave packet still travel at or below c.

[@kittensmitten8793]

The photon propagates, with some probability, through all the paths. Why would it not also travel, with some probability, all the times?

[@AlexGallegos]

It’s not just light. All energy can travel through time. It’s the reason the electron slit experiment works. It’s the way electrons can change from solid to energy based on the observation by consciousness.

[@feba33]

Light be like fuck it