I did the double slit experiment at home

[@LookingGlassUniverse]

If there are variations you’d like to see, let me know, I’ll film them as a short :)

[@Redjuicey]

If you rotate the splits 90 degrees, does the pattern appear vertical? I've always thought it odd that these experiments always produce patterns on the horizontal :) And can you create a 4 sided "slit" to try create a circular or square pattern of interference? Or is that too much interference or not possible?

[@stephens1393]

Nice approachable video. I always felt like the typical demonstrations and explanations don't connect to real-world experience well enough. I'd like to see your version of the other side of this coin-- what's your approachable experiment to show the particle-like nature? Can you demonstrate the photoelectric effect at home?

[@BroImVlogging]

Yeah, block all the extra beams except your target center and have another wall behind your current setup to see if more beams appear.

[@L2p2]

can you do one with a donut shape hole. ofcourse it needs someting to hold it up. so basically a circular shaped obstruction.

[@HMan2828]

Try it with polarized light! (filter the beam to allow only one polarity before the slits)

[@eduardpertinez4767]

You forgot to mention the most important point. And that is that the experiment works the same even when you send the photons one by one. The interference could be explained both by light being only a wave and by light being particles that somehow follow a pattern when they bounce against each other. But the magical point of the double slit experiment is that sending photons one by one, the interference pattern arises in the detector screen even when there is no possibility for the photon to interact with any other photon.

[@myke13021]

If i remember correctly, the Heisenberg's uncertainty principle can bring it back to particle behaviour. If the photons are observed, they behave like particles again.

[@luizfernandonoschang8298]

OK, wait a minute! Is that just even possible? To shoot only one photon?

[@JohnKerbaugh]

The reality of multi-dimensionality being visible in photons behavior is an interesting thing to think through. The wave isn't all within our 4 dimensions at any given point in time and that wave only interests our dimensions at one point at a time.

[@tman197]

@Luiz Fernando Only if you're not observing it/them... :)

[@registrationaccount1034]

​@@luizfernandonoschang8298 yes

[@siya.abc123]

I turned 103 y/o this summer and this is the best version of the double slit experiment I've ever seen. Well done young lady

[@ericchristian6710]

@@siya.abc123 I don't believe u at all

[@ericchristian6710]

@@siya.abc123 what was your favorite thing to do when you were 14?

[@ericchristian6710]

@@siya.abc123 I don't mean any disrespect I love old people and if you're really 103 I think that's freaking awesome and I'd like to ask you a few questions cuz I'd like to learn stuff from you but I am very doubtful

[@ericchristian6710]

@@siya.abc123 doubt is the same as curiosity I think it's the other end of it the the critical thinking goes along with curiosity I want to know it all and then I want to sift through it for what's good

[@aarontooth]

MOTOR TORPEDO BOAT

[@ranjansingh9972]

Absolutely marvellous! You can be taught by a teacher, a lecturer, through a book - but nothing brings it to life like doing the experiment yourself! Thank you for taking us on the journey.

[@stevewithnell911]

Tell me, I'll forget. Show me, I'll remember. Let me do, I'll understand.

[@cmvamerica9011]

Einstein said: “ It’s a miracle that curiosity can survive formal education.” . It takes curiosity to be able to do science. Keep up the good work.

[@Bretaxy]

And?

[@tenminutetokyo2643]

He also said creativity is more important than knowledge.

[@edgymaster7376]

no he didnt

[@scottturner1504]

Well I know Einstein said "the difference between intelligence and stupidity is that intelligence has its limits "

[@CeRz]

And formal education kills creativity with recipe-like lectures, assignments and laborations.​@@tenminutetokyo2643

[@sherylbegby]

This was fantastic. I love your skepticism. It's amazing to see a physics PhD admit they're not entirely, viscerally, convinced by the wave theory of light, and then work out whether they can find a way to convince themselves either way. It is seeing the scientific process in action, and it's a beautiful thing. Thank you.

[@viola0livido]

It's called "scientific method"

[@viola0livido]

@@BobbyT-yj1cw naaaaa

[@viola0livido]

@@BobbyT-yj1cw it is how it's called...

[@FictionCautious]

She's not a gatekeeper, yet.

[@kujojotarostandoceanman2641]

​@@viola0lividobased

[@DougKendig]

Outstanding! By far the most definitive example I have ever seen.. and I am 60 yrs old.. Wow.. well done young lady.

[@alien.intergalactic]

You're the first person that has shown this without graphics. I love it.

[@taylorbyrum1851]

Yeah, I googled double slit experiment but like nobody was doing the actual experiment lol

[@sebastianclej-dv8ju]

If you send only one photon, it’s almost impossible not to use graphics

[@Paraselene_Tao]

I came looking for a video like this, just to see it done in real life. I have seen it in several textbooks, many animations, and several physics simulations. I've never taken a physics class for light, and I don't know if many light physics courses would have a lab experiment to go with the double slit experiment or other optical phenomenon. It was definitely nice of her to show us her setup and show us how the waves interfere. I only wish it went one more step or a few steps further and showed us how to slow down the emmitance of the laser down to single photons, and then measure each with an observer. That would be even wilder to see happen in front of us: watch the interference patterns disappear as the observing instrument measures where the photon is going, and watch the interference pattern reemerge as we stop using the observing instrument. That would be very interesting to see in person or even watch it happen with a homemade setup.

[@maconcamp472]

The Big Bang Theory!! 🐘 🐾 🥁 Each thought represents a bang❗️Higher vibrational thoughts 🐝🐝🐝 will create bigger bangs‼️ Pebbles And Bam Bam!! 🧊 🦕 🧊 🦖 🧊 🦣 🧊 Each grain of sand or pebble, a building block for planets or dark matter!! 🪨 Dark energy aka consciousness, creates the bang!! Supernovae!! 💥 Super Moons!! Flowery moons!! 🌹 Saturn a flowery moon!! Representing the 6th dimension!! More energy!!🪐 🛸 We control it!! 🧞 We’re stars!!✨ Hi, Hey, Hello!!🦜 The more G’s, the better!! They’ll reflect our minds, technology, and more!! G strings!! 👙 👙👙👙 Our brains look like gum!! 🧠 Juicier the better!!!🍏🍋‍🟩🫐🍍🍎🍌🍈🥥🍐🍉🍒🥝🍊🍇🍑🍋🍓🥭 Love everything until it loves you back!! Mosquitos too!!🦟 ❤ Each of us and each galaxy would represent a cell!! 🦠 We’re stars putting ourselves back together again!! Like Humpty Dumpty!! 🥚 🐓 The sky is blue because we’re meant to imagine it as a diamond!! The auroras then create the rest of the spectrum!! 🌈 💎 A purple sky would reflect the heart of the ocean!! An opened mind!! 🤯 The earth purring more!! Purrrrrple rain!!☔️ 🐈‍⬛ 🧶 Each thought to me is a solar flare, which shifts us into parallel worlds!! It’s hard here!!! I’m a peaceful dude, yet my life here has been super difficult!!🥹 Alpha Centauri represents a shift in consciousness!! Dog planet!! We’re riding the alpha waves!! Woof woof!!🐶 🐾 This is our world peace and enlightenment for the world and universe!! All is one!!😇🥳🥰🤩 We’re each a mini universe!!🌌 The 3 Body Problem represents our gut brain, 🍱 heart,❤️ and mind!! 🧠 The moon is a black hole!! 🕳️ A neutrino!! The planet is a colonized moon!!😇🌍👽 The sun is a shapeshifter!! 🌞 Are you and I sculpting together as a team or as individuals??? 🧑‍🎨 Using the moon as a tool!!! 🪨 The Sun is the eye!!👁️ I love the tool/word grinder!!!😮 We’d be Bumping and Grinding!!😂 The Earth is like a refrigerator and the atmospheric pressure is melting or defrosting the stars above, as if they’ve been in the freezer!! 🥶 It would also reflect us krystalyzing and becoming diamonds in the sky!! 💎 💎💎 Lucy becomes Maisie!! 🐒 👽 We could be stars from above aka heaven, melting everything from above, as well! Like a River Running Through It!!! 🌊🌊🌊🌊🌊 Gravitational waves or our thoughts raining down on us!! 🌧️ Unlocking a Secret Garden within and outside of us!!🤫 An Oasis!!!🏝️ 🏝️🏝️🏝️🏝️ Flowing!!! It helps a lot to flow!!!🌊🌊🌊🌊🌊🌊 Letting go, so we can concentrate more and work on our project!! Heaven On Earth!!🌍 👼 Flowers!! 🌺 🌸 💐 and Flow-Ers!!🌊🌊🌊🌊🌊 I know energy is still impurrtant!! 😻 And of course imagination!!! Love!!!💗 🐶 🎾 🧶 🐈‍⬛ To create heaven On Earth, the galaxies collide!! 🌌 Twin flames connect!! 🔥 🔥 We’re creating quantum entanglement!! Ghost particles merging, becoming more like the Stay Puft Marshmallow Man!!👻👻👻👻👻👻👻👻 The universe is still the Earth!!⭐️🌍⭐️ We’re seeing it from the insides!! 🕵️ Like we’re inside a volcano 🌋 or wishing well!! The stars and galaxies are like coins!!🪙 The Goonies vibes!! 💀 We’re treasure!! Antarctica is treasure island!! 🐧🇦🇶 Unlocking antimatter!! 🐜 Booby and booty traps exposed!! Planet X!! Hubba Hubba!!🥰 Everything and everyone has been our teacher!!👩‍🏫 3D is like the murky bottom of a bong or volcano!!🌋 The fourth dimension, representing Mars is like the stem of the bong or the volcanos vent!! 👽 Experiencing higher dimensions is like the smoke or magma reaching our mouths 😋 and then circulating through our bodies!! We are the Earth!!🌍 👼 The road less traveled!!!🧳 🌹 Straight up!! 🎈 🎈🎈🎈🎈We’d be super condensed or extremely packed neutron stars!! Like Rigel!! Blueberries!! Antioxidants!! Betelgeuse has evolved into a neutron star!! 🍊🫐 Our long winding road, exploring different dimensions, finally straightening out!! I’m getting Pee Wee vibes!! Large Marge sent me!!🚴😂 We’re vaporized, as if we’ve been smoked or roasted!! 💨 The smoke representing again those compressed neutron stars climbing the higher dimensions of the universe like a chimney!! I’m Mary Poppins, y’all !! ☂️ 🧞‍♀️ It would also represent us as a comet traveling through a wormhole!! 💫 Who me, I’m just a worm!!🐛 🫖 Solving a labyrinth!! 🦉 Solving amaze!!! 🦋 Different energies tell a different story!! 📚 We’re storytellers!! Artists!!🧑‍🎨 We’re energy first!! 🐝 A 12 inch boner is like receiving a foot of snow!!⛄️ 😂 When powered by neutrons and a magnetar energy field, one is like the energizer bunny!!🐰 They’ll keep going and going and going!! 🐇 🐇🐇🐇🐇 If you’re destined to have more than one twin flame, you’re like Frogger, playing leap frog!! Lucy is a sucker for Lillies!! 🐸 🍀 🐸 🍀 🐸🍀🐸🍀🐸 G Force!!!🥳👙🥳👙🥳👙🥳👙🥳 Dorothy’s Ruby red slippers!! ❤❤ Something here in 3D land has to change, yes, mmmmm! Dark Crystal Series!!😍 🧚🏼 We need to get this show rolling!! 🎥 We need our second moon!! Two moons!!! Two Mercurys!! Two black holes!!🕳️ 🕳️ They’ll need some color!! 🌈 Two blood moons!! 🩸 🩸 Two Ruby red slippers!!🥿 🥿 We have to die and become reborn!! Dye!! Dye those slippers red!!😮❤❤😂 Makes complete sense!! 🤯 There’s no place like home!! Home is where the heart is!! Jupiter and the 5th dimension!! 🐸 🍀 Clover Field!!👽 🛸 Time speeds up real fast once we’re there because seeing is definitely believing!! We get excited, hearts start pumping!! 💕 Minds start to open up!! 💜 Oxytocin pumping through our blood!! A love signature!! ✍️ Removing our writers block!! We’re storytellers!! 📚 The two blood moons also like draculas fangs!! Or the fangs of a snake and spider!! A kundalini experience!!!🐍💜 An anti venom!! 🐜 A love bite!! I’m nibbling your ear!! Ringing your ears like church bells!! A liberty bell! 🔔 Heightening your spidey senses!!!🕷️😳🩸🩸 My story just gets juicier!! When is it juicy enough for you, I guess, is the question!! Strawberry Hill!! Cherry Blossoms!!🍒🍓We even got hills named after chocolate!!🍫 Purrthquakes!! 😻

[@bobm4378]

@@Paraselene_Tao textbooks and simulations are just that, NOT REAL.. they are too busy doing the math to get thru their college course... if you ask them what the 'observing instrument ' is, they will give some math answer..

[@kunk6818]

You literally woke up my curiosity over quantum mechanics which I buried long ago for my software career. The demo of double slit experiment is like never before. You're the main reason I bought QM by J.Griffiths textbook a year back. You inspired me a lot. Keep up the amazing work. Love you.

[@LookingGlassUniverse]

I’m so happy to hear that! Thank you for your lovely comment :)!

[@kunk6818]

Is there a Patreon Page or any other way so that I can support you?

[@LookingGlassUniverse]

@@kunk6818 aww! I don’t have one at the moment but I am planning to set one up :)

[@mastershooter64]

Do Shankar principles of QM after griffths

[@kunk6818]

@@mastershooter64 Thanks for the recommendation.

[@CyberMongoose]

My intuition for why diffraction occurs comes from Huygens' principle - it's the natural tendency for light to radiate in all directions. Light traveling as a beam is actually a very uncommon state that is caused by the interference of different points in the wavefront. As you block parts of the wavefront you remove this interference and the light radiates spherically again.

[@LookingGlassUniverse]

Yes, huygen's principle seems to be the the right way to think about it! But what I don't understand is, given huygen's principle, how do laser beams stay so well collimated in the first place? What do you think? I'm planning on just sitting down and working it out for my next video

[@CyberMongoose]

@@LookingGlassUniverse At a large enough distance even a laser beam will become spherical, but the distance required depends on the wavelength. How well collimated the beam is to start though depends a lot on how the laser cavity is designed. Having now watched the full video, I find it interesting that you initially preferred the photon picture of light. For me it was the complete opposite: I found the photon picture of light so confusing that I chose to do my PhD in quantum optics just so I could understand it better. So far though it hasn't worked and I dislike photons even more now. The main thing that bothers me is that the way we commonly talk about photons is very different to how Fock states are actually defined. For instance: in the double slit experiment, its not that photons are coming out of the laser and randomly choosing a path to take. A photon in this case is an excitation of the entire diffraction pattern.

[@coolcat23]

​@@LookingGlassUniverse I think the laser's light is so focused because only the photons in the direction the laser is pointing receive constructive interference. The mirrors in the laser are shaped so that all photons hit it with the same phase and they are only constructively interfering in the longitudinal direction implied by the two mirrors. There is nothing more "natural" per se about light to radiate in all directions. Natural light sources just don't have a preferred direction of emittance. The reason why a straight light beam diffracts at a sharp edge is due to the uncertainty principle. If the location of a photon is precisely determined (as in "it is just about not blocked by the edge" then its momentum (direction) becomes very undetermined. Hence the spread into all directions.

[@LookingGlassUniverse]

@@CyberMongoose I know, it’s been driving me crazy! What the hell is a photon?? I used to think it as point like, but exactly as you said, modes are not at all point like. I’d love to hear more about how you think of light. If you’re down for it, send me an email to looking.glass.universe at gmail

[@jonasdaverio9369]

@@LookingGlassUniverse Also keep in mind that visible light is made of wavelength extremely small compared to the diameter of the beam. At microscopic scale, the beam looks like a massively large plane wave. If you try to generate kilometer wide waves in the ocean, you will find that they don't spread very much, very much alike lasers. If you try to make a very small (microscopic) laser beam, you will have no choice but to see it spread out.

[@thirdeyyye]

I’ve watched many videos on this subject before, but this is honestly the very first one I’ve seen that has helped me gain the most understanding about the double slit experiment…so, thank you for that! What an excellent video.

[@A-moose1234]

As someone who has spent way too much time thinking about the double slit, this was an amazing video. Thank you.

[@stevenhoog1]

It was wrong. Consciousness or the observer actually does not collapse the wave function. It happened bc of the measurement device used. See Neil degrass Tyson double slit. It was all bullshit. When they measured it the measurement was light which changed it not consciousness.

[@demonsheadshot8086]

The ability to see something physically and practically that you've only seen or heard theoratically is such a surreal moment like THIS is infact a real thing, it exists, I am seeing it with my own eyes and not just some mathematical equations/models, as someone who is curious about literally anything I get my chance at, this was pretty amazing

[@andsalomoni]

If you want to see diffraction effects with your own eyes with no experimental equipment, just put two finger near your eyes, look at the space between them, then bring the fingers together, when they're close enough the diffraction effect starts.

[@BobSacamano666]

You like plants?

[@atlantic_love]

That's a pretty lame attempt, dude.

[@ericscott6447]

Heh. Same thing when I looked through a telescope at Saturn. My knowledge had always been indirect, from some sort of a storage repository. Books, TV, Movies. But then my wife got me a decent telescope. It was a revelation. No camera. No screen. Just me and this celestial body in the same moment. A real mind opener.

[@smyrnianlink]

@@ericscott6447 What size objective lens/mirror do we need for that feeling sir?

[@mfatihakal6635]

I don't write comments very often but to this one I really had to. 14:05 and 14:20 are simply jaw-dropping. You are really a very good experimentalist, I never really imagined that I could see light as a wave with plain eyes as it propagates. Thank you very much, it was simply a perfect visualization.

[@LookingGlassUniverse]

Thank you, this comment means so much to me. I started thinking about this video a year ago and at the time I only knew about theory but I had no idea how to do real experiments. It’s been such a journey even to get to the point where I can do this ‘simple’ experiment. Thank you for your kind words

[@mfatihakal6635]

@@LookingGlassUniverse I'm very glad that you felt so 😊 Keep up the good work 🖖

[@dahawk8574]

@@mfatihakal6635 * Plain eyes. Or maybe you have cat pupils. Heh.

[@mfatihakal6635]

@@dahawk8574 Haha, you're very much right. Some words don't let you go when you spend some time with them. Corrected :)

[@dahawk8574]

@@mfatihakal6635 Speaking of cats, I am wondering if Mithuna's next in this series will be... 'I killed my cat at home'. Yikes. I'm sub'd. But concerned. Hah.

[@satosato4169]

Not sure if you'll notice, but I have to say this. I have looked for something like this for years. I'm in love with quantum physics and can't pull out of my mind all of this. I was simply vaping in my room, turned on my laser pointer and noticed this, clearly, but never really saw anyone noticing this as well. Moreover, all of the videos about double-slit experiment were strictly about "life isn't real!!!!!", so it's actually a big relief to see this. Thank you a lot.

[@boldkojak2734]

I knew the experiment for decades since i studied physics in the 70s but never thought of doing the experiment myself until now 2024 . I am so proud of you, brilliant young lady and resourceful . Brilliant people make complex easy and guid others … bravo And thank you for bringing some scientific excitement to an old man, 🙏🙏

[@tibees]

Love this video! Your choice of books for holding up the ripple tank perfectly summarise the journey you are taking us on to understand the weirdness of reality. Well done! 💗

[@dip8870]

hello :)

[@daviddavis-vanatta1017]

Agreed! And my copy of Griffiths just happened to be right on my desk, next to the keyboard, as I began this video!

[@Dave-xc7cj]

Which dimension are you talking from? lol

[@guyincognito.]

Summarises*

[@tharii314]

Wow! I was wondering whether it's you (tibees) doing this video, but younger. 😋

[@UnlistedAccount]

Your enthusiasm and curiosity is infectious. I love seeing people build their experiments at home, getting incredibly educational footage and sharing it with the world. Wanting to follow that light back was clever, and I finally got to see the waves.

[@twitzmixx8374]

right?? I keep holding myself from clicking the × button because she made everything so interesting in every second if the video.

[@dongshengdi773]

​@@twitzmixx8374 ​@ ​ Light is both a particle and a wave . That's why human beings are both a body and a spirit.

[@aarontabi398]

put me through the double slit and what happens is...

[@JuanPablodelaTorre]

Love the idea of using a single hair! It is so much simpler and clearer than the double slit. I tried to show this effect for a science fair when I was 9 or 10 (almost 30 years ago👴) after reading some book on QM. But, it was impossible to replicate with what I knew back then (books would show an incandescent bulb as the light source 🙄). Well, now I'll come up with an easy to carry setup and I'll tour around my family and friends homes showing them how cool this is. I've been waiting for this for too long.

[@kevincasson9848]

You must be joking. She was all over the place, and incoherent. Can't beat the original double slit experiment! Light is a wave and a particle when observed. Which she didn't touch on. Are they giving away PHD's to anyone these days?

[@nickb3164]

this is genuinely one of the best science explainer channels around

[@OriginalPuro]

Brian Cox.

[@terrytin7352]

So clever and simple. As a teacher for some 40 years I can honestly say your talent for communication an devising simple demonstrations is considerable. Good luck for the future - you'll make a difference to so many students ! 🌞

[@morpheus6749]

Except that she's dead wrong about what she thinks are light waves. See my post above. She is astonishingly clueless and sadly misleading the unsuspecting public.

[@Yogesh-kr7bo]

​wdym there's no post above

[@atlantic_love]

Stop slobbering.

[@Leszek.Rzepecki]

@@Yogesh-kr7bo Well, the problem is the photon also acts like a particle when it's absorbed or emitted by an electron. She completely avoided that issue. Lots of atoms absorb and emit light at specific wavelengths, and that light is absorbed or emitted by electrons as their energy level goes up or down. A photon can be treated as a particle or a wave, it acts as one or the other, depending on what you are observing. Electrons have a wavelength too: From google: Louis de Broglie showed that every particle or matter propagates like a wave. The wavelength of a particle or a matter can be calculated as follows. Thus, the wavelength of electrons is calculated to be 3.88 pm when the microscope is operated at 100 keV, 2.74 pm at 200 keV, and 2.24 pm at 300 keV.

[@Zazu1337]

@@morpheus6749 I searched all 1146 top level comments for your post and couldn't find it would you mind to repost?

[@bobpilz1021]

Well, that was the most informative explanation of the double slit experiment I’ve ever seen. I’ve always been confused about this for the same reasons you mentioned. Well done. I hope you do more along these lines with light.

[@Pastisas]

As a PhD student in experimental physics it was fun for me to watch a theoritical physicist discovering that experiments are fun! :)

[@LookingGlassUniverse]

Yes!! I can’t believe that I hadn’t tried doing this myself before and I only worked on pen and paper. That stuff seems so dry now compared to playing with lasers

[@Pastisas]

@@LookingGlassUniverse Indeed, seeing physics happen with your own eyes opens up entirely new perspective! It is funny when you realize that all experimental physicists have to do theoritical analysis but theoretical physicists never do experimental work. You just broke that barrier! Hope it benefits you in your academic life.

[@mastershooter64]

yea but lab reports 💀💀💀

[@jimmyboy131]

@@mastershooter64 They're a part of real life work. As an engineer that's one of the end results of all work I do: design and run the experiments, analyze the data, then write it up in a final peer-reviewed report.

[@jimmyboy131]

@@LookingGlassUniverse This reminds me of how there were two camps in school. One camp were the math or physics majors, the other camp were the engineering majors. We all had to take many of the same classes and we clashed (that's an overly dramatic word) over wanting more theoretical examples vs more practical examples. So...another thing we've proved here is that engineers really do have more fun.

[@DrEhrfurchtgebietend]

I am a former physics prof and used to to this in a lab I taught. I wanted to do this at home for my kids. Was not sure if I needed proper equipment. This helped. Thanks

[@MrMelvinSchlock]

Light has always kind of freaked me out. For instance, you can have an infinite amount of viewers looking at the same spot on a mirror and there will be an infinite amount of different reflections. Or, sitting in your room, every point of light bouncing off all surfaces in all directions somehow resolve in our eyes to fine detail.

[@cronaman3196]

Well it wouldnt ever be enfinit becauze the mirror ends and that second thing you described is just your feild of view. Try and focus on your feild of view, its blurry and not that detailed. You cant focus on it maybe because the light isnt all being reflected. Im in my room right now, my green pillow with white spots is in my perifrial but if i really try and focus on it withought looking at it it literally just looks green to me. And the white wall that its agains is in full detail, cus there. Try and take a thin thing like a book and take it as far out of your parifial as you can withought actually loosing sight of it. And just observe it. Think about your eyes too, theyre spherical, what youre seeing isnt actually flat as your brain WANTS to precieve it. Youre brains flipping the image upside down, focusing on the center and if you go agains the own rules of your prain yourll feel a little bit of strain and discomfort, at least i do. Because were actually limited and our brain forms the illution and our contiousness preieves that illution. And everything beyond that is unknown

[@JohnCena-le1jj]

Of course infinite viewers will be shown in a mirror, because the mirror reflects the light that the electrons in the viewers' bodies emit. Is that so surprising?

[@charlesbarr3437]

Hmm. Sorry terrible comment. Blessed be. 🎉❤🎉

[@martincrown8616]

@@charlesbarr3437 no it's not

[@martincrown8616]

something i found interesting was taking my first long exposure picture. i kind of took light for granted before this but once i took a long exposure photo in almost pitch black darkness, and it appeared as a sunday morning, i was able to grasp how mindblowing light really is.

[@bobcarn]

This was one of the coolest physics video I've ever seen! You took what is common to any enthusiast and presented it both in a new and interesting way, but also in a way that can be replicated easily at home! Freaking brilliant!

[@syllogismo]

Didn't people learn about it in school? It took me back to school. I guess my science teachers in school were really good 😊

[@Watchyn_Yarwood]

👍

[@kevincasson9848]

OMG. She hadn't a clue. Didn't even mention that the interfering, pattern collapses when observed. Oh dear! Oh dear!!....Don't try to fix something that aint broke, should be her motto. Terrible presentation. Full of holes lol

[@hhf39p]

Everyone knows light acts like a wave. What is surprising is to see particles act like waves, or for light to act like particles. I didn't find this video impressive at all.

[@Watchyn_Yarwood]

@@hhf39p I'm sure this video was not produced with the intent to impress you.

[@BetterThanEmber]

So cool that you got the other beams to become visible! I've worked on this at home myself and it is absolutely worth doing, but I've never actually seen the other beams and figured they were just too dim compared to the main split beam to register optically. Unrelated: I always thought of waves as the "real" concept and particles as the "abstract, for math purposes only" idea. I wonder why our brains do that.

[@ian-flanagan]

Do you mean beams on the paper, or in the air in transit to the paper? I want to do this at home so should I buy the most powerful laser online?

[@thestralspirit]

@@CoruscationsOfIneptitude are you on the electrons don't exist team too? What about atoms in a Bose-Einstein condensate? Does simply changing the state of matter make it so that the atoms themselves cease to exist?

[@thestralspirit]

@@CoruscationsOfIneptitude I was actually kinda hoping, for some reason, that you might have something interesting to say that defends your stance that the particle half of quanta is only a mathematical construct. Unfortunately, you decided to stop asserting things about physics and start asserting things about people. If you ever grow out of ad hominem, I'll gladly have a conversation with you about physics.

[@toddcamnitz6164]

This video helped me realize something that’s long perplexed me about popular summaries of the double slit experiment, specifically the part where the summary says something like “but observing the electron changes it back from a wave to a particle, collapsing the wave function and fixing the electron in space.” From here, many non-experts lark off in all sorts of wild directions about consciousness, time travel, etc. Your video, plus another showing that a real double slit experiment with only a small amount of space between the slits results in a random cloud under observation (measurement), instead of two distinct clouds, made me realize that probably what’s happening is this whole particle and wave notion maybe isn’t correct. Or rather, *in no case does the electron behave like a particle, really.* it’s not that measurement turns the electron (or photon) “back” into a particle, it’s that measurement screws with the initial wave, such that the resulting waves hitting the final measurement board are sort of all over the place, and no longer interfering perfectly enough to develop the interference pattern. It’s not the notion of observation that’s doing this, it’s the mechanical requirement of observation in the first place - to make the measurement something has to interact with the electron, and that interaction isn’t changing the electron from a wave-like thing to a particle-like thing, it’s just changing the “shape” of its waviness. Put another way, it’s not the wave-like nature that’s disappearing upon observation, but literally just the perfect arrangement of wave like natures that result in interference. I think this confusion would probably go away entirely if we could somehow figure out what exactly a photon really is.

[@DheeBheee]

What really breaks my brain is that Young's double-slit experiment has also been conducted using all sorts of things that we generally agree are particles: electrons, protons, atoms, all the way up to large organic molecules (buckminsterfullerene about twenty years ago up to a 2000-atom molecule as of 2019). Great video and very good explanation!

[@vlake8614]

and they also reacted as a wave or as a particle?

[@teddansonLA]

@@vlake8614 they all show the characteristic interference of waves, but are detected as particles.

[@ArtistJoshuaWeigand]

This is the best variation or presentation of the double slit experiment I've seen. Really amazing to see all those beams

[@WilliamLeeSims]

I love all the way you "blocked" the laser (none, full blocking, right/left half, hair, double split, etc.). I'm looking forward to future experiments! Finally, thank you for mentioning laser safety. Laser power has gotten crazy out there!

[@LookingGlassUniverse]

I completely agree about the lasers- it was genuinely difficult to find lasers that I could trust were safe. All the labels on lasers mean nothing because they’re terribly regulated.

[@cykkm]

@@LookingGlassUniverse Even worse, the same applies to safety goggles! Most are as good a PPE item as no goggles at all. On the very first search page, there are googles with non-existing rating "OD 4+" without any mention of wavelength range. For 14.99, the price of cheap sunglasses. Yeah, right. And add the lack of training to that, people think that donning even real goggles gives them the Superman's eyes. Gosh, you can buy a 1.5W blue laser on Amazon or eBay for under US $200! And this wavelength is quite energetic, not yet ionising, but certainly able to wreak royal havoc on fragile organic molecules even before cooking tissues thermally, so the usually considered class 2 limit of 0.25s eye exposure likely may not apply. They should be handled as class 3B-in a controlled lab... Not the thing I'd dare to even turn on without proper setup. It has enough power to bounce off only slightly glossy black surface and still blind anyone around or even outside the window.

[@Competitive_Antagonist]

@@cykkm Damn that's nuts. I remember messing around with only 3B lasers. I did by some supposed match burning laser on Wish a few years ago, but it's only a 3B blue laser. Maybe the UK has better laws in place, as I remember someone telling me that you need a license to buy some of these powerful lasers and they have a very legitimate use in astronomy.

[@cykkm]

​@@Competitive_Antagonist Yes they are used in astronomy, yellow wavelength range (Nd compounds). These are much more powerful. Google "adaptive optics." You've likely seen the stock footage of observatories shooting a bright yellow ray up the sky. But they are mounted on the telescope, already a dangerous machine (and expensive, too) with only trained personnel having access. There are many legit uses in research, not only astronomy. 3B is "not only"; it's a very dangerous thing. If you want to operate it confidently, take a safety course, and you're totally fine as soon as you're following the procedures and get PPE from a reputable vendor (wideband goggles are in a $100-200 range). The 3B safety class is defined as, IIRC, causing "permanent vision damage regardless of exposition time, and possible skin burn" unless properly handled. This label is not about power, medium, wavelenght or anything, it's only about standardized safety procedures. Different countries and states have different rules, but generally the idea is a windowless facility with a warning light at the door when laser is in operation, and only trained people allowed in, OR shooting them up the sky with safety in place preventing anyone getting close to the beam closer that X (a meter or two), for light shows. FAA permit may be required for the latter (Fed. Aviation Admin.); I never did this, I don't know, only guess. Here in California 3B and 4 handling requirements were the same 20 years or so ago. I don't work with them anymore, now daughter does. :) Class 2 and above are illegal for sale to general public here as separate units, but it's not enforced for internet orders. It's not a big issue, in general, and law enforcement resources are limited. ADDED: I think licensing discourages responsible experimentation at home. Come think of it, regular tools like a wood-chopping axe are even more dangerous if used improperly, but we don't license them. And handguns are legally sold at every corner. Safety education and raising awareness is a more productive approach.

[@watamatafoyu]

@@LookingGlassUniverse Perfect demonstration of why we need proper regulation; companies will do whatever they want at anyone's expense to maximize profit.

[@tyjones9963]

This video made physics 1000 times easier to understand for me. Please don't stop making these videos.

[@jrod1235]

Yes, please continue the experiment with single photon. The whole point is to show the wave AND PARTICLE duality because when observed, they behave like particles, but when not observed, they can exhibit interference patterns.

[@gyro5d]

When not observed, the rarefaction of light is a shell/wave. When observed, the compression of light is a photon.

[@gyro5d]

Aether's field is wave. Aether's mediated to center zero point/Counterspace/Nothing is the particle. Light is aligned Aether. "Scalable Aether Universe".

[@robertsouth6971]

Or particles in other universes affect the particles in our universe.

[@renedekker9806]

_"when not observed, they can exhibit interference patterns"_ - in the interference pattern, they are observed as well. When not observed, you don't see anything. What you probably meant to say, is that when the possible paths of the photon can interfere with each other, they show an interference pattern.

[@HunterHM1489]

“Observed” in the double slit experiment is actually a misnomer… The researchers didn’t observe the photons that caused it to collapse into a particle function, they “measured”… meaning they literally interacted with the wave before it even encountered the slits. Considering that a photon is the smallest unit of anything that we can measure with, it’s difficult to measure another photon without affecting its state/position.

[@dictatorjames]

Thank you for making something *real*, something educational, and without any click-bateyness. This is so fascinating.

[@CuidightheachODuinn]

clickbaitiness* Sorry, I'm anal.

[@TheFaarf]

A thought: Does different colours of light have a different interference pattern? Red should have the largest gaps, and violet the smallest because of the difference in wavelengths. Is the difference big enough for the human eye to see using a double slit experiement? Great video! This made the wave-particle duality of light a lot more intuitive for me!

[@MrMeltdown]

Yes the dots are more of less spread out depending on the frequency

[@henrycgs]

Yes, the colors change the dot pattern, and yes, it's visible to the naked eye! White light has a really interesting dot pattern as it's made out of pretty much all frequencies between red and violet, so doing the double slit experiment with sunlight makes a really colorful pattern, kinda similiar to a prism. you can try yourself, with a long dark box with a double slit opening. but it's a bit difficult to get it right because you somehow need to, you know, be inside the box to look at the pattern. you can look it up online if you want. veritasium made one in a video some years ago

[@foogod4237]

This is actually a really good thought: It would not be hard to modify this experiment to have two different colors of lasers mounted vertically one above the other, both going through the same double-slits, so you could both see the difference in patterns on the screen, as well as see the different spread of the individual "beams" through the fog...

[@derbemobile]

Great video. Thanks. Love your enthusiasm.

[@luizfernandonoschang8298]

Why the light creates a pattern horizontally but not vertically? I mean, many sound waves are omnidirectional, so I would expect that the light waves were too.

[@Sunflower-rg1nt]

you have no idea about how much this video changed my perception of light. thank you so much. your curiocity is appreciated

[@samerbazerbashi]

I’m not a scientist but learned about this experiment from Brian Green years ago on PBS. It was such an enigma! I kept following up on the newest reasoning and nothing made sense! This video was almost cathartic. Your explanation was clear and the tests were simple and easy to grasp! Great job!

[@ScottFreemire]

@manuelfrn I don't know how to detect individual photons at home but it's been done in the lab. From what I've read, any attempt to measure the photons before they hit the back screen eliminates the dotted line effect and instead you just see two spots of light (or one spot with a line through it).

[@kwimms]

PBS is the BEST source of woke scientism... Great job!

[@doggonemess1]

Very cool! I'd recommend doing some experiments with polarization filters. When you take two together, turn them so they become black and then put three together and turn one and it makes them transparent, that really blew my mind.

[@LookingGlassUniverse]

Will do! Thanks :)

[@Will-kt5jk]

Visualising that with the smoke machine would be really interesting.

[@surendarvijay2520]

Ah! The good old quantum eraser

[@hdthor]

When you use three, it only works if you turn the middle filter. Each filter can only twist light so much before it’s completely blocked. If you use two filters to block out all the light, merely adding a third filter over them will never get you back light, no matter what orientation you rotate that third filter. Imagine if schools accept you if your accent is similar or reject you if your accent is too dissimilar. You can therefore only attend schools that are nearby otherwise your accent will be too different and you’ll be rejected. But attending that new school changes your accent so now you can attend an even further away school. So you can eventually attend a really far away school with a completely different accent by hopping through intermediary schools that slightly twist your accent little by little.

[@830927mjki]

@@hdthor ah, so the light cant twist 90 degrees between filters, but it can manage ~45

[@uziah1113]

What’s really cool is I’m now realizing that this was right in front of me the whole time. I have an astigmatism so I see lights like this all of the time. Kind of coming at me in beams, the moment you showed the final experiment it hit me. That’s insane

[@austinsinger7565]

Same here

[@Aiden-ham]

You don't even need astigmatism to observe this effect! If you squint your eyes so they're just barely open (a slit!) you will see the light spread out like in the experiment

[@mofirminhosadiosalahrobert4904]

@@Aiden-ham i actually just did this , and yes squint and you'll see the lines , ngl for a quick second there i thought i was doing something a little bit amazing , you brought my straight back down again , lol

[@manlyadvice1789]

Me too. Since my glasses lenses are made of a material with a high refractive index, they exaggerate the effect, which is most noticeable with near-monochromatic light. Since so many people have been moving to LED lighting in recent years, I've been seeing a lot more of it than I used to.

[@abelnyamori]

@@Aiden-ham you just blew my mind. I’ve always wondered why lights look like that. This is insane

[@CosmoPuke]

I conducted the double slit experiment at home. The wife threatened to divorce me.

[@Lee-sf7nw]

First video that actually showed real proof of it. Maybe I'm bad at finding things, but you totally nailed it and blew my mind away. Thanks for making and sharing this.

[@juandissimomagnifico7819]

i just saw this and i am so excited for this series, light is right next to gravity for me in terms of being something so frequent and interesting and yet so little is intuitive and even understood about them. PLEASE DONT STOP

[@paronga42]

Great video! In my third year physics at Monash Uni I did the single photon double slit experiment. It’s mind bending and I highly recommend you check it out. Especially if you are loving the wave nature of light. In the experiment you get to see for yourself how even a single photon of light can become a full wave and produce the same result as the double slit experiment. I’m no longer in the field of maths of physics, but I still remember that experiment. It changed my view of the universe. Great to see some great Australian physicists on KZbin! Keep up the great work.

[@IFY0USEEKAY]

That must have been awesome! Whenever I hear about the single photon double slit experiment I remember that when the photon is measured for position, the waveform collapses. Yet I have never been able to find actual video of this happening, only "simulations" or "replications". Is there any video out there that you have come across?

[@MagiMas]

@@IFY0USEEKAY This is the single photon experiment: kzbin.info/www/bejne/m2STc6iKo819pMk here it is with an explanation of what you're seeing: kzbin.info/www/bejne/lX7Tp3d3htd-mNU

[@Dinofaustivoro]

I was looking for a comment about this. The real quantum magic happens when you do it with just one photon.

[@Argrouk]

Did you really do a single photon, or did they lie to you with maths?

[@tonydwoodhouse1]

kzbin.info/www/bejne/f2qkk2t4gbxmoaM the single photon experiment starts around 5:46 - showing the wave nature of light and the quantum “collapse” on measurement

[@David-yt3tv]

one of the better explanations of the double slit experiment I have seen... bloody well done, especially with the type of advanced lab we all have at home :)

[@jessespad]

Everyday before high school i would smoke pot in the shed on the side my house. The shed was small and had 2 sliding doors that came together in the middle. There was always a small gap about 1/4 inch between the door panels and the sun was just rising over the horizon straight across from the shed. I'd sit on one side of the shed and blow smoke into the light. The light passing through the smoke was one of the coolest things I've ever seen. It was like taking a 2D plane out of a 3D or even 4D cloud. It's hard to imagine unless you've seen similar yourself, but I still remember it 25 years later. This reminds me of it. Go out and try it today!

[@lugosky02]

Oh my god! Girl I remember watching your channel something like 10 years ago, and somehow it disappeared until just now. A huge fan has been reactivated! I'm really happy to see you and to hear you've done a doctorate. It honestly feels like reconnecting with an old friend. Also, what a nice experiment there. I think I'm going to copy what you've done here! Thanks!

[@LookingGlassUniverse]

Oh my god, thank you for this adorable comment!! That’s so sweet! What are you up to these days yourself?

[@sibbyeskie]

I love this whole thing! I’ve heard so many times about the double slit experiment but never seen it such a practical everyday sort of way. You’re right it really hits the ideas home. This quantum home experiments idea of yours is great. I like that it’s slightly wonky and underproduced. Truly. Wonderful stuff!

[@David_Hogue]

I've seen that pattern and didn't realize what I was seeing with my own eyes. I knew about the double slit experiment. I even knew a lot about RF waves and interference patterns. Somehow this tied it all together in a way that made me tear up. Thank you!

[@joe-nautilus-nauticus]

Yes, we take what's been studied and surmised from others works for granted, assuming there isn't more to the story as it were. I learned so much more from your clinical experiments, creative thinking, and results. Thank you for posting.

[@Blivot]

It reminds me of Side-Bands on a Spectrum Analyzer. "Third, fifth, seventh & more hamonics. We used to see these same type of hamonics on, "14 thru 128 track Recording Heads 15 inch on reel to reel systems.

[@talon6268]

​@@Blivot wtf are you ranting on about lil bro

[@Blivot]

​@@talon6268 At the RTS GUAM Tracking Station we had to verify that the Playuback Heads on the Memorex Recorder's were not producing harmonic sigjnals stronger than the real data signal being recordered. Light acts like a sound or electronic wave too so who knows, it could be related.

[@timtigerjazz]

I really like how you personalized this experiment and revealed how you now can start to see the wave character of light as real from getting your self directly involved and finding the facts for yourself through direct observation of real experiments in real time etc

[@ironjide7975]

I’d love to know why the light only scatters in one plane, or what would happen if you added another horizontal slit. There’re so many variations, it’s amazing

[@lUnderdogl]

What if blockers are something sphere and in flight

[@Darkduke1000]

if you add a horizontal slit you get a cross with the interferance pattern on it i tryed before =)

[@nir199820]

en.wikipedia.org/wiki/Arago_spot@@lUnderdogl

[@squared8290]

OK, first off, unbelievable! So incredibly well done! Absolutely love this. My favorite part of the video is when the laser output starts looking like strings on a guitar fretboard. Goose bumps... I don't know if it helps but I think of light just as a signal and hence as a wave. I think of it being nothing more than a signal demonstrating that there has been a change made to a field. Changes in field strengths lead to ripple-like distortions in your field lines and hence you get a wave that traverses space over time. As for the particle nature of light, this is probably a great oversimplification, but perhaps to maintain some kind of intuitive sense of what light is, we just accept the quantized nature of things. It's not that light is a particle, it's just that it's quantized and hence in a very peripheral sense has something in common with real physical particles. Thank you so much for the video!!!

[@MsGnor]

This is the first time the double-slit experiment felt tangible to me, thank you for a wonderful set of demos 🌈💖✨

[@48ford8n]

Great explanation! I hope you will touch on the real odd behavior that the pattern on the wall will change by simply observing which side of the slits the light comes through. At home this is typically done with polarizers but to me that’s not really the same as the classic double slit experiment.

[@asdfafafdasfasdfs]

I've never understood these experiments, would be interesting indeed... I always think about that as somehow theoretical

[@p3t3mit]

Wow, I absolutely loved this. I've seen so much content about this experiment, but you managed to teach me a lot and think about things in a way that I hadn't ever before. I think it's because you're genuinely curious instead of just teaching an "established fact". Someone with your background you could totally expect this to be all drab and rote and just a textbook answer but you're actually digging in and trying to perceive and conceptualize things. Thank you.

[@dennishancock]

You are: curious, courageous, enthusiastic, intellectually honest, intelligent, sharing, humble, and inspiring! Keep on illuminating the world

[@kylefillingim7275]

Just thought it would be important to note that the results are quite different when using a wide spectrum such as white light. I tried it with white light at first and thought the whole physics community was crazy until I saw it with a narrow spectrum Lazer. Of course that was about 2 decades ago.

[@tombrazier6172]

When doing this at home I find it fun to turn the ISO (i.e. gain) up to max on the camera and turn exposure time and aperture down. When exposure gets low enough, the image begins to resolve onto individual bright spots. If light were simply a wave then the experiment I have described would always give an interference pattern, just with less and less intensity. Instead you get a random spread of individual dots at a fixed intensity. So light looks like a particle in this version of the experiment. But take a lot of these photos and sum them together and suddenly the interference pattern is back. So in the *same* experiment you can demonstrate that light is interfering like a wave but arriving at the target like a particle.

[@manlyadvice1789]

I must argue that quantization has nothing to do with light being a particle (which it's not). Light is a product of two fluxes. Thinking of fluxes as objects is an attempt to shoehorn the language of classical mechanics into electromagnetism where it doesn't belong.

[@manlyadvice1789]

@anolakesThanks for the 3rd grade simplification of mistakes made by professional physicists. The people on whom you would rely for your explanation think of light as a "point particle," which is demonstrably incorrect and doesn't even make sense as a physical entity. I would get more into the physics, but that's not really the point of contention. There are some people who are simply incapable of imagining a universe that isn't made of stuff, so they think everything is a particle and all field and flux behaviors must arise from particle interactions, similar to what you've said. I assert the opposite, that light is entirely made of flux-driven fields and hydrogen (THE atom) is made of light. Ultimately, there is no such thing as a particle of any kind. Physical substance is fundamentally insubstantial.

[@manlyadvice1789]

​@anolakes Okay, Captain Physics. What is the smallest, most basic particle made of?

[@manlyadvice1789]

@anolakesCongratulations. You've won the KZbin comment section. You may now feel good about yourself.

[@gopinathvaradarajan6743]

Light always Wave nature, till you either observe or falls in to screen/object, then it becomes particle. Narrowing aperture amounts to detecting so it becomes particle.

[@rowanjones3476]

Love your work. I like how you’ve demonstrated both how simple this experiment is to perform, and how profound its implications are. On a safety note: perhaps acquire, and recommend the purchase of a pair of laser safety glasses suitable for the wavelength of laser being used, if it is capable of burning you. They’re way cheaper than new eyes.

[@yourii2c]

Would you care to expound on these implications so I can see what level of reality you have ascended to?

[@mhouslay7281]

Big thanks - Brilliant Loved your enthusiasm and doing science stuff at home. Chemistry sets when I was young got me excited about science and that enthusiasm has never left. I’m in my 70’s and ready to do a double slit experiment for myself now. Keep up the good work.

[@effectingcause5484]

You absolutely MUST do a follow up video! You MUST fire the laser through a sheet of darkened paper, add another sheet, then another sheet, allowing the light to become dimmer and dimmer, until only one photon at a time is making through the darkened sheets of paper. You will need a very, very sensitive photographic plate to detect single photons. But if you do this, you will find a single photon can land on the photographic plate at some random location in the form of a dot on the screen. Then, if you fire one at a time millions of time over, you will be shocked to find the interference pattern builds up one at a time. Your experiments are good ones, but I want to point out that the smoke is not necessarily illuminating a wave of light interfering with itself. The smoke can be viewed as if it is illuminating many trillions of single photons, all traveling within multiple beams of light, and these beams are all compromised of single particles. The particles follow a path which is seemingly non-deterministic but still at least follows the Schrödinger equation quite well. The Schrodinger equation mathematically treats the path of each photon like a kind of “wave of probability” which determines where the photons are able to land and the likelihood for all of the possible landing destinations and paths that can be taken. That mathematical wave describes the likelihood of all possible paths, and is called a “wave function." The wave function is said to interfere with itself after fanning out from the double slits, causing a pattern of light and dark fringes which can be interpreted as wave interference, even for a single particle or photon, because the wave function is describing many 'possible' paths simultaneously, yet all paths are describing the same particle. So in this way, the wave function is like a mathematical tool which describes places where a single particle is very likely to land and places where the particle is very unlikely to land. Photons can be viewed as particles even after fanning out from the double slits nonetheless. They can be viewed as traveling in beams, not necessarily waves, while still accounting for the light and dark fringes. The individual particles within a beam can only follow paths allowed by it's wave function however. In this view, the middle bar of the double slit serves as a point of origin for a "repeating shadow" which displays as dark fringes from regular repeating angles, where all light fringes are beams of photons (particles) which are pivoting from the openings of the slits, and all dark fringes (which are merely shadows) are pivoted from the middle bar in between the slits. The dark fringes or "shadows" are regularly repeating because the two slits are spaced at equal distances from the middle bar. Someone will ask, why should the photons ever pivot from the slit openings and fan out towards the left and right sides of the photographic plate in the first place? Someone will say, if photons can be viewed as particles in the double slit experiment, then we should always find a double-line pattern directly behind the slits. Why don't we?... It is because of Heisenbergs Uncertainty Principle. Here, most people misunderstand that it's just the speed and location of a photon which cannot be known simultaneously. But the more accurate truth is that - speed, location and thirdly, the 'direction' also, cannot be known simultaneously. We do already know the exact speed of a photon, which is always equal to C. We can also know the exact location of the photon if we create a single slit that is narrow enough to quantify it's location at the moment the photon passes through. But by knowing the exact speed and by narrowing down the exact location of a photon when it passes the slit, we will have sacrificed the exact "direction" of the photon after it emerges from the other side the slit. So when the photon exits a single slit, or of course any double slits, the direction of that photon will be completely undefined by the universe and so the photon shall change trajectory after the slits and be aimed at any 'possible' location on the photographic plate. None of the photons land on the dark fringed bands because in this view, the dark bands are caused by the middle bar which simply casts a repeating shadow behind all angles that are not possible. In this way, we can account for the light and dark bands as beams of particles, rather than waves. I’d also recommend/request that you do a follow up study/video which explores the nature of the photoelectric effect! Here we learn how Einstein models light as a beam of particles, rather than waves, to explain the observations of the photoelectric effect. He eventually won a Nobel prize for this insight because it essentially proved that it was impossible to explain the photoelectric effect when modeling light as any kind of waveform, but instead could be readily explained by viewing light as a beam of particles. You think you’re amazed so far about the properties of light? Hahaha! You’ve only just begun to dive down the “what is light” rabbit hole.

[@sweepingdenver]

Fun reply with a lot of great insight, but everything you describe is just a theory. There is no definitive proof of the "pilot wave" theory. Yes the individual photons will accumulate into an interference pattern. But, as of 2024, no one truly knows why! Lots of competing theories, but it will probably be a long time before the next big breakthrough that unequivocally proves what is happening.

[@pingpong9656]

This is correct - her experiment is incomplete at this point. Needs to go much deeper.

[@kobayashimaru8114]

She knows this. She's just showing us an easy way to do the experiment at home so that we can visualize the phenomenon with our own eyes. @pingpong9656 I wouldn't call this experiment incomplete. It is pretty much complete although simplified. The original double-slit experiment was essentially done the same way. In later versions of the experiment it was performed with individual photons. It was even done using other particles and even molecules which surprised me.

[@pinkeHelga]

Pairs of single photons / quantums of light are produced by a special crystal. But what should it say us? Think of a photon as some soap bubble. The membrane is the wave front. You can seek it und when you have found it at some place, the bubble disappears. You get some local effect. Without further interaction it will continue to spread out from that point.

[@effectingcause5484]

@@pinkeHelga I love the bubble analogy, but it implies that if we keep making more photon bubbles, then all the bubbles will just pop at the same location every time, at whichever object is located closest to the bubble... Here's another analogy Neil DeGrasse Tyson once offered - Photons are like shouting words at a crowd of people. But the first word gets heard by only one person strangely, while the second word gets heard by another person in another location, the third word by another person in a different location, and so on. All of the words are shouted in the same direction, but the sound waves fall on randomly located ears, the location seemingly non-deterministic, or at least not determined by any known physics.

[@Confuzer]

I am obsessed with this experiment as it's the most simple clue to something we cannot grasp yet. I think a particle is an expression when interacting, but underneath it all a wave of smaller elements/vibrations which might be on a plain that is only visible on that interaction. Some call it a probability wave but I think that's just an abstract way of looking at it. I really like the smoke! But in a way, each laser hit on a smoke particle was in a way the wall being closer to the split. But the effect is super cool as you can also detect possible anomalies at a certain distance instead of just the wall distance.

[@abhinav-4556]

Hey that sounds like string theory are you a fellow believer

[@Confuzer]

@@abhinav-4556 it sounds like it and it might be the same. I just think that everything there is might be the same thing in a different state, and that relativity is all, even time.

[@namopatel-ij6cc]

​@@Confuzer so what this experimnet concludes??? photons or atoms are fully concious..???

[@Confuzer]

Euh no, that is a bit of a leap into fantasy there ;)@@namopatel-ij6cc

[@Confuzer]

No, that is fantasy. Conciousness also has no meaning I believe on the scale of physics. It's just an emergence, a causality.@@namopatel-ij6cc

[@cmdrblahdee]

I would be curious to see the pattern as more and more slits are added. The delayed choice variant is always mind bending as well, but im not sure if that's possible with an at home setup. I know this wasnt what you were testing, but in the video you were so excited about the wave nature, very little was said about the particle nature. As I understand it, the photoelectric effect doesn't make sense without considering light as photons.

[@eyewaves...]

I have never given up on this experiment for more than forty years !! This is the most fascinating experiment one could ever do at home... for getting involved with Quantum Mechanic !

[@moladiver6817]

This experiment never ceases to amaze. What really blew my mind though was that actual particles such as electrons also produce interference patterns. Perhaps you could figure out a way to show that too? That would be so cool! But please keep it safe. 🙏 Amazing videos. I'm already a fan.

[@Scrogan]

Problem with matter is you need the mean-free-path before collision to be significantly longer than the distance it’s travelling. With air molecules around the particles need to be travelling very fast, like “ionising radiation” kind of fast. It’s basically only viable to do the experiment in a vacuum chamber, with a particle beam. Electron beams just need a heated cathode and a plate with a hole in it at, held at a high voltage, but it’s a bit of set-up.

[@andsalomoni]

There is a 70-80's italian TV documentary that shows that: kzbin.info/www/bejne/qn7PaoCbZ82igqc

[@andsalomoni]

There is an italian TV documentary, uploaded on KZbin, that shows that. Search for: "L'esperimento più bello della fisica l'interferenza di elettroni".

[@0ooTheMAXXoo0]

Electrons are also wave phenomena... Are only like a chunk with position or speed or direction when measured, interacted with. The right amount of energy in a harmonic configuration for there to seem to be one or two or however many electrons when interacted with...

[@arifsaifee4146]

This is one of the best (if not the best) video I've come across that explains the wave/particle duality in a way that even a layman can understand. Well done!

[@MrFreeGman]

How do you figure? She didn't even do the other half of the experiment with single photons that makes it so mind bending. Maybe I missed it, but did she mention anything about how observing the light changes its behavior? Did she mention how photons can behave like waves even when you fire them one at a time, and how the photons take random but probabilistic paths when not observed? I honestly don't think she even understands the experiment herself.

[@miki_9034]

​@@MrFreeGman Take it easy, man; this is just a home experiment. Making equipment that can fire a single photon is costly (at least from what I googled.) If you disagree or think there is a better way of demonstrating this, please do a video. Don't be bitter.

[@MrFreeGman]

​@@miki_9034 That's besides the point. The experiment is incomplete and boring without showing how photons can behave like waves when they're fired individually. It's got nothing to do with being bitter. This video is just getting a lot of undue praise from people who have no idea what they're talking about.

[@miki_9034]

@@MrFreeGman You sound like you're a physicist. That might be why you're disappointed with the lack of depth in explaining the particle side of light, and I understand that. The reason I loved the video is because she dumbed down the experiment for a guy like me who is not a physicist and within my budget ($20 - $50)

[@jolanewmen5447]

@@MrFreeGman That's just a different experiment with the same set-up. And I think the observer effect of it might be simpler to do with electrons anyway since they're probably easier to fire one at a time than photons. The experiment wasn't meant to show the wave collapse, but was a demonstration of light's wave-like properties. The experiment is in no way "incomplete", you just misunderstood the purpose of it.

[@ObviouslyASMR]

That's probably the coolest DIY experiment I've seen on KZbin, and those visuals.. wow

[@yourii2c]

Really have to wonder why the simple addition of smoke to aid in visualizing this phenomena has not already been presented to us by our brilliant scinetists doesn't it?

[@scottmiller7000]

That was awesome. Thanks for putting this together. I love the fact that you did this from home using materials that are easily purchased. Nothing like being able to simulate Quantium mechanics principles at home easily.

[@truejim]

This is an outstanding video. You told the two-slit story as a personal journey, with terrific animations and a fascinating climax.

[@adastra123]

Brilliant ! You are one of those real scientists that actually uses whatever is around you and you tinker with things. Kudos big time. When I was a young fella in my teens ( I am fifty something now ) I used to program a commodore computer and take electronics things apart. You are like super version of that with massive brain horsepower . Thanks for uploading and the brilliant explanation. It calls consciousness into question.

[@stephenbenner4353]

I love that you took all this time to find out for yourself. I’ve seen lots of detailed animations and heard really good explanations, but you’re the first person I’ve ever seen actually do the experiment. Anyway, this is the first video of yours I’ve seen, but I subscribed to your channel hoping for more of this kind of in depth experimentation.

[@-danR]

Post-doc confused by her own hair. Makes youtube video to confuse the rest of us.

[@t.me_s_petizioni_2220]

Sì siamo stufi di disegni animati. A scuola non sperimentiamo un'acca, almeno qualcuno insegna a farsi esperimenti in casa!

[@t.me_s_petizioni_2220]

@@-danR Meglio confusi che omologati a dogmi (divulgazioni spacciate per scienza: semmai c'era scienza, sta in chi ha sperimentato, non in chi ha sentito dire o letto!)

[@draudes657]

During the night I encountered a roadwork traffic light consisting of a (square) matrix of LEDs (2 cm pitch?). Waiting for it to turn green, at 15 meters, I noticed a fading out extension of the same pattern in all 4 directions very similar to Double Slit Experiment. To eliminate windshield influence I went out of the car. To eliminate my eyes influence (astigmatism), I repeatedly tilted slowly my head, but no change: the reverb was perfectly aligned to the LEDs row/column direction. Do these punctiform LEDs produce the same effect as the punctiform light passing through the slits? The power source is a car battery (DC current, no flickering). I appreciate much your passion to perform the experiment and extend it with variations.

[@jonathanrabe3727]

This is an awesome explanation! For your question at 5:54, in RF engineering the same happens to waves propagating, when they encounter an obstacle. Note that the obstacle size determines if the wave will bend around, or if it will cause a "shadow". There is a video by Physics Videos by Eugene on yt that explains all this quite well. Anyhow, waves being bendy around corners comes from the fact that they are carried in some medium (free space for example, is a great medium for EM waves). As the wave disturbes the field it is carried by, it will cause an effect on the nearby field as well, and so for a corner, the nearby medium will also be excited...

[@vnkkhare078]

Eugene is the LOVE ❤️❤️❤️

[@donaldkasper8346]

The blocking object has an electric field. Notice no one grounds the objects or runs current through them, they just throw things to block light. No carbon fibers for an attempt at grounding, nothing, just stuff thrown out there. Now metals are pure s-polarized reflectors, but are wires tried? Nah, why, use stuff. Now, with a laser spectrometer, I have several of those s- and p-polarizers. They are actually circular so you can count off by degree what you want, but s- and p- are at 0 and 90 degrees in the device. Of course, I would run the light through the polarizer to see what it does.

[@hhf39p]

ssshhh! Don't tell my old roommates Albert Michelson and Edward Morely about that medium of free space thing.

[@thenargles]

This is absolutely magical to see. Even though it’s physics, not magic! I never imagined this could be done at home.I simply have to try it! Thanks so much for the brilliant video. 😊

[@alexoftheway8169]

What a really cool video! I guess that's the great side of available technology is that people like you can do really interesting experiments and videos like this for the rest of us to see! Keep up the good work.

[@zyxi8143]

5:47 To asnwer oyur question "Why does it happen?" This is Huygens Principle. Every point on a wavefron can be considered a source of secondary wavelets. these wavelets spread out in all directions. When part of the wavefron is blocked, the wavelets near the edge of the obstruction continu to propogate and overlap, creating a new wave pattern that bends around the obstacle. The extent of diffraction depends on the relationship between the wavelength of the waves and the size of the obstruction. If the wavelength is much smaller than the obstacle, the waves pass mostly unaffected and diffraction is minimal. If the wavelength is comparable to or larger than the obstruction, significant diffraction occurs and the waves spreads out widely. The only reason I'm aware of this is because I work as a sound engineer, and sound shares the same principle as to why it can "bend" around corners. To learn more I would recommend reading up on wavelength theory.

[@kirahokuten357]

Been trying to understand this double slit experiment/light being particle or wave and I've watched tons of videos about it, your video helped me understand it on a different level. Thumbs up!

[@Steve-bu3qr]

Unfortunately, no, this still isn't it. It's a misinterpretation. No waves have ever been observed.

[@thesentientneuron6550]

I did this experiment back in HS following a video by The Thought Emporium. I got the pattern, but I couldn't understand this whole 'observation makes the pattern disappear' thing. I think he mentioned in his video about using a polarizing filter to 'observe' it. I used polarized sunglasses for this but to no effect. Thank you so much for covering this riddle I couldn't figure out for years! I thought I would have to wait until I took a course on Quantum Mechanics for my higher studies to get a clue on what was going on. Thank you so much for experimenting with this and sharing! I'll be following this series quite closely from now.

[@RWMAirgunsmithing]

Replacing "observing" with "taking a measurement" (ie. Interacting with the system) I find makes much more sense. When the photons hit a detector you collapse the wave function and gain information (take a measurement) about the particle, in layman's/NdGT terms you made an "observation". Edit : the "making the patern disappear" part happens when you have a controlled particle source and measure what slit each particle passes throuh, versus using that same source, not measuring the particles and ending up with the wave pattern. Every time you interact with the system you collapse the wave function.

[@MrWhateva10]

Agreed with R WM. The polarization filters can be used in "single-photon" setups where the light is massively constrained at the entrance to the experiment such that on average only one photon should be traveling through the system at a time. The polarization filters demonstrate that interactions with the system, but only in a way that provides which-path information, collapses the wave behaviors to particle-like behaviors. If you put a horizontal polarizer after each slit, you are interacting with the system and thus changing it, but you are changing both paths equally and thus you still have the interference pattern. If you put a vertical polarizer after each slit, you still have the interference pattern. But if you put a horizontal on one slit, and a vertical on the other, you *could* now determine which path a photon has taken through the slits by measuring its polarization at the end. Even if you don't actually take that measurement, the interference pattern disappears. If you introduce a third polarization filter at 45 degrees and further down so that both paths would travel through it, the interference pattern returns! This third filter is called a "quantum eraser" because it is erasing the which-path information that could be gathered from the different polarization filters on the two paths. This is truly astounding because the single photon of light is reaching the slits, being polarized one way or another, entering a second polarization filter and now is suddenly traveling both paths again to create the interference pattern in the end.

[@DavidByrden1]

@@RWMAirgunsmithing Sorry, but that's not a helpful interpretation. Not in the long run. Because, you see, the wave function doesn't "collapse". Nothing in the theory of QM corresponds to "collapse". If you imagine the wave "collapsing", you'll grasp the double-slit but you'll get very confused by the Afshar Experiment, or by Entanglement. It's just not a mental model that works everywhere.

[@DavidByrden1]

I didn't see any place in the video where an "observation" was made. An observation of which path was taken.

[@DavidByrden1]

@@MrWhateva10 ."..you could now determine which path a photon has taken...by measuring its polarization...Even if you don't actually take that measurement, the interference pattern disappears" I would expect it to reappear if the target screen were made of material that erases polarisation data...does such a thing exist?

[@tiagopariol]

This video is worth sharing with all our chem. Engineering / civil / mechanical / electrical undergrad friends !

[@peterburgess5974]

I really enjoyed this video, so thanks. At the age of 13, we set up a practical in physics class, and the double slit experiment really confused me. I respected this particular teacher so much because we were encouraged to ask questions rather than provide answers based solely on what we saw. At that age, I didn't realise that we were being introduced to the first glimpses of quantum physics. I enjoyed physics; building a motor from scratch was an amazing experience, although I wasn't a great student compared to my peers. I thank my physics teacher, whom we called 'Planck' (Brian Boardman, his name a 'play' on his surname), and all those who tried to educate me. My excellent physics education enabled me to understand more about the physical world as I gradually moved into the field of geography. Life is an amazing experience. It's worth living. Ad altiora!

[@davidcox9983]

Very cool. I love to see your wave patterns. I worked in the radio electronics field, and with antennas for many years. I've always felt that light and radio wave were really the same thing, only at different frequencies. In fact, if you lower the frequency enough, you get into the audio wave frequency, which creates the effect of sound. Audio also travels as a wave, physically vibrating objects that it meets with its energy. So audio waves, light waves, electrical energy waves, and radio waves are all related and provide similar properties. Food for thought!

[@JohnB-l4d]

I used to experiment with antennas a lot, I was infatuated for decades and it's almost all I thought about in spare time. Your statement caused me to remember how I always pictured standing waves on an antenna. The pattern I pictured was amazingly similar to this!. I have to think on this a while, Thanks!

[@nadarajahsriskanthan5639]

Note that radio, light, microwave, x-ray etc. are electromagnetic in nature conceived (currently) get propagated without a medium!! While sound (audio) waves need the air to propagate; reducing the frequency won't do.

[@davidcox9983]

@@nadarajahsriskanthan5639 Agreed.

[@mildpass]

Great idea for a series. For me the mindblowing part was when I first ran the experiment of a laser incident on a resonant Fabry-Perot cavity. Even though it's just two mirrors facing each other any laser you send through it takes the shape of Hermite-Gaussian functions from quantum mechanics. Still blows my mind to this day. Aligning the cavity and laser is a pain though even with proper equipment.

[@TomRock81]

The video was cool, and she did do a really great job actually showing what happens. There is something that I don't understand, the most significant part of the double-slit experiment is that light reacts differently when there is an observer, human, video camera, etc.. I'm just confused why it wasn't mentioned. Other than that, awesome job!

[@RhezaElfuegoTheWizard]

still waiting respond to this comment

[@captainfaulpelz6308]

i had to scroll down about 50 comments to find you, someone that was confused about the same part as i was. what you mentioned is where the double-slit experiment starts to get interesting. therefore i clicked the video, because i thought there is a way we can try that interesting part at home. i am shocked about the fact that pretty much nobody in the comments even mentioned that, and how impressed all those people seem to be while the reality shattering part of the double-slit experiment is not even mentioned in the whole video. seems like almost nobody here has even a clue of what makes the double-slit experiment really special.

[@otaku-chan4888]

​@@captainfaulpelz6308 there's nothing really reality-shattering about the 'measurement' of the double-slit experiment- the most interesting thing still is the fact that light interferes with itself and isn't a particle. You only 'think' it's reality-shattering because _you needed a detector to observe your reality._ The more practical interpretation of why results are 'influenced' by observation is because *acts of observation disrupt the system too much.* By wanting to observe a result, you have to put down a detector screen. By putting down a detector, you're interfering with the quantum uncertainty, that wants the opposite of measurements to remain a probability. If you interfere with quantum states, of course it'll collapse into a non-quantum state. By deciding when and how to detect results, you can predict what result you're going to get. If you don't allow for a probability function, there won't be any. It's like saying looking at a dice is reality-shattering because the moment you look, you get a number. Of course you will??? In fact, if you look waay too hard at a dice right after rolling it, and start calculating things like how hard you threw the dice, how many times it bounced and at what speed, etc, you'll be able to math out what side it's most likely to land on, and hence what number you'll get (from that dice side). Does that mean you collapsed a wave-function? In a sense, yes- you measured too much information, too early, and influenced i.e changed the probability such that the dice is no longer a wave function of many probable number outcomes but one very likely number result. That's common sense and not very reality-shattering.

[@Brayan_Arias]

I don't know if you noticed but the pattern is not limited to the horizontal line....if you pay close attention to the vertical axis you can see also a pattern like a circle, not just in the horizontal line. I repeated this experiment and I have a pattern too. When I zoom in I can see a texture in the light, a little more complex figure than just dots and dashes. Thank you for this great video.

[@Brian36685]

Awesome! I read about double slit and was obsessed for awhile. I think the scientists originally thought the particles were just causing interference with each other, and that's why it made the interference pattern. But doesn't the original double slit experiment shoot one particle at a time and it still creates a wave? Scientists were baffled, so they put a measuring device there to see what the particle was doing, and it acted as a particle and not a wave, creating just two slits of light. It was the act of observing it that made it do what you would expect from a particle. When the observation device was taken away, it went back to the interference pattern. Its as if the particle knew it was being observed. Not only that, but that one particle was everywhere all at once. Its been awhile since I have read that piece, so hopefully I got that right. I am not a scientist or student. I am just obsessed with science in general and the nature of creation. Quantum physics is incredible. I believe we are all just one mind, separated into conscious beings, and its our subconscious mind (single collective mind) that creates reality, and our conscious mind observes visually and physically through light. Thereby collapsing the wave function and creating what we see and feel as reality. Anyway, this was a great video. Thanks!

[@Woodledude]

Thank you for bringing this up - I loved the video reminding us that there's more to this experiment, and there's very good reasons why it was controversial then and important now. The rabbit hole always goes deeper. Your pondering on the nature of consciousness is interesting, too. I tend to think of it more from a bottom-up perspective - Consciousness as an emergent property of simpler systems, finely tuned through natural selection to achieve certain goals. But with that approach in mind, it's not hard to keep extrapolating up, and see the actions of something like a corporation or a government as very similar to those of a single person, just on a different scale. So why not all of us, at once? Everything and anything? We might be pretty incoherent, all together, but that's not to say there isn't some thread that could be recognized as some kind of thought pattern there, even if it isn't terribly meaningful. Reminds me of Andy Weir's short story "The Egg". If you haven't read it yet, I highly recommend it. Sort of a fictional expansion on your thoughts.

[@sebbo36]

thats exactly on point. With psychedelics you can see and experience all that. This is so interesting to research

[@debrachambers1304]

The ORIGINAL experiment didn't use single particles because that wouldn't be possible with the technology of the time, but single particles were later used

[@DavidByrden1]

You will understand it better when you discard this concept called "collapse of the wave function". That doesn't happen. There is nothing in the theory of QM that corresponds to "collapse". Why would anybody even talk about "collapse"? It's as if we had a theory of earthquakes, and then somebody said "How do earthquakes begin" and we replied "A dragon moves his tail". Completely ignoring our own theory.

[@Brian36685]

@@DavidByrden1 thanks for the correction, but it would be helpful to include a way to describe it. I'm still left only half corrected. 😄

[@qdadahu]

I think it's even more interesting when the intensity of the light is reduced (a lot). Because with many photons in the system, we can present a model where the particles of photons are oscillating positive/negative and when they collide, you check their 'charge' and that leads to the same experimental result you predict with waves. What's crazy is when you reduce the light intensity down so much that you essentially have single photons being fired from your laser, the photons will still destructive interfere with themself.

[@Argrouk]

That's massively incorrect.

[@MrWhateva10]

@@Argrouk Interested to hear your perspective on why @qdadahu is "massively incorrect"? "Single photon interference" is somewhat famous as an example of how "weird" quantum mechanics is. The interference pattern is clear even when only a single quanta of light enters the experiment at a time. And like the double slit experiment, when a measurement is taken as to which path the photon has taken, the interference pattern disappears. dash.harvard.edu/bitstream/handle/1/27413728/single_photon_paper.pdf

[@Argrouk]

@@MrWhateva10 because it's not a single photon, it's an extrapolation of data.

[@MrWhateva10]

@@Argrouk I mean, everything is an extrapolation of data. lol. That doesn't mean it "isn't a single photon". I think we have ample data that light is quantized, we call the "unit" here "one photon", though it is obviously not a point-like particle. There is no "half photon" or "two and three quarters photon"... it is a unitary quanta. In so called "single-photon" experiments the aperture is sized so that "on average" there is "1 unit" of light in the device at any given time, sometimes zero, sometimes two or more, but given the speed of light and flux, it's an average of one photon at a time. Critically, the detector at the end registers a single impact point. That single point is actually a triggered cascade of photon-electron interactions that produce a signal large enough to be sensed, but in a single sensor cell, not over many cells as you would expect from a wave washing ashore. These cells are triggered sequentially over the duration of the experiment, exactly as you would expect particles of light to behave, and yet when the information is gathered over time an interference pattern emerges. It's incredible, counterintuitive, and there are no explanations yet offered that use only classical mechanics like "spherical billiard ball particles" or "waves in the aether" that fully explain the data from that experiment. Always interested to hear one though if you've got some ideas.

[@DavidByrden1]

@@Argrouk I don't know why you deny the "single photon" experiment. It HAS been carried out. We know how much energy a single photon carries and we have emitters that emit so little energy that there is, statistically, no more than one photon in the experiment at one time. That's not an extrapolation of data, it's the actual situation. There are related experiments where the photon is split into two photons. They register simultaneously at two separate detectors. Why would that happen if there was not literally a single photon emitted?

[@Snarlydowrong]

These demonstrations are really cool! I wanted to point out though that the diffraction patterns seen in the video are often confused as a quantum mechanical effect, but they can all be explained with classical mechanics though using Maxwell's equations, which are the wave equations of classical light (still really interesting!). The quantum mechanical double slit experiment is quite difficult to do because it requires determining which slit a particle passes through. Let's say you instead send electrons at a double slit in a wall, you would again find a diffraction pattern on the wall behind the slits like you do with the laser, making it seem as though the electrons are waves. Really you would be seeing electrons arrive as particles in the wall behind the slit, but the distribution of where the particles landed would give an interference pattern that you would expect from a wave passing through the slit. This is the particle-wave duality of quantum mechanics! Next you point a light source at one of the slits so that light would scatter off of an electron and into a detector when the electron passed through. This would allow you to determine what slit the electron went through and suddenly you would loose the diffraction pattern on the wall. Instead the electrons would act as if they were particles. It might seem as though this is simply the result of light interacting with the electrons and not because you determined which slit the electrons went through. You can test this though by increasing the width of the light source so that it covers both slits, so it would still scatter light when an electron passes through, but you would no longer be able to tell what slit the electron went through. Doing so would actually cause the diffraction pattern to return on the wall, meaning the electrons are acting like waves again even though you are scattering light off of them. The diffraction pattern arises because the electron is in a superposition of going through both slits and interferes with itself in a wavelike way. When you put a light source on one slit, you force the electron to pick which slit it goes through destroying the superposition so that the electron no longer interferes with itself. To be clear, it doesn't matter whether or not you or any person actually looks at the detector to see which slit the electron went through, nature doesn't care about that, just that the light source is there forcing the electron to choose which slit (the reason it destroys the superposition is due to something called decoherence, but that's a bit more complicated). Thanks for coming to my TED talk lol.

[@aclearlight]

These are interesting speculations, but as an experimentalust who has done a bit of work like this, let me explain how devilisly difficult it would be to design an experiment approximately corresponding to your suggestions (to the extent that I followed them, please correct me where I'm missing your message). Electron beams are much harder to work with than light beams since they require vacuum conditions to avoid spurious attenuation and scatter. Their wavelengths are typically much shorter at easily-controlled velocities, so a double slit approriate to photons would likely be far too large to use with electrons. Electron beams require serious gear to render them monochromatic and collimated enough to illucit stable interference behavior. Gating the device to know when photons and electrons were hitting the target, whether simultaneously or not, would be very tricky. Lastly, finding and tuning a detector to respond to both photons and electrons would likely be a challenge as well, though I can imagine it being possible with sufficient effort and budget. You would need a very good dynamic range with respect to both particles since, eventually, you'd be wanting to dial beam intensities down to single quantum fluxes and then integrate over extended periods. All so much easier said than done.

[@Snarlydowrong]

@@aclearlight I totally agree that this would be a very hard experiment! You would need a much smaller slit spacing for electrons like you said. For an electron moving at non-relativistic speeds its wavelength is around 40x10^-12 meters, making the experiment very difficult, although it has been done in some form and the wave like nature of electrons has been experimentally verified. One correction, in the experiment I was talking about you would have separate detectors for the electrons and the photons. The photons just need to determine which slit the electrons went through. The light source wouldn't need to anything special since you would just be scattering light off the electrons. Although the diffraction limit of light would be much larger than the spacing of the slits so that would pretty much make the experiment I described impossible. Really, I think the quantum mechanical double slit experiment is almost more of a thought experiment to explain the core concepts of quantum mechanics. However, experiments analogous to it have been done. For example, using a beam splitter and a coherent light source such as a laser you can prepare photons in a superposition of traveling along two different beam paths. If you bring those paths back together you will get an interference pattern similar to the double slit experiment (this is the basis of interferometry). You could then separate the light, once the two beams have been recombined, by its wavelength components by sending it through a spectrometer (essentially acts just like a prism; see the dark side of the moon album cover) and detect the intensity of the light based on it's wavelength. You would see that the photons would arrive at different spatial location on the detector (that corresponding to different wavelengths) as if they were particles. However, over time, the distribution of particles would show an interference pattern you would get from a wave that could not be explained if light was made of particles. If you don't have a spectrometer lying around ;) you could also vary the path length of one of the beams and look at how many photons arrive as a function of the difference in length of the two beams. Then all you need is piezoelectric motor lol. Ultimately, to really seeing quantum behavior light is not trivial and typically requires more complicated experimental devices (unless there's some cool simple method that I've never seen). Btw you're probably very aware of all of these experimental methods but in case others who aren't happen to read this I wanted to describe them in more detail.

[@snowy10r]

I thought the collapse of the interference pattern was more complicated than light setting the particles to one path.. Didn’t the classic double slit experiments also cite that trying to detect the particles at the slits with a sensor also resulted in the wave collapsing? Which makes it seem like any kind of measurement would be impossible?

[@olswirly]

try a light bix and cut 7 slits i asked what happens beyond the doubel slit maybe you can got more than seven . but at 7 slits your shadow behaves steange and thats all ill say . do it its a simple science rideel challenge im piseing to you tube physics folks yup . ol swirlys 7 slit expirement yup . wtf

[@karlkarlsson9126]

Maybe someone can clarify this, I'm a bit dumb, but light is waves in the electromagnetic spectrum, and the electromagnetic spectrum is oscillated electric and magnetic fields, does this mean light is electrons bouncing up and down (oscillating) to create various frequencies for us to see? Or is it the field "per se" that is created by the oscillated electron that creates the light? If so, what is this field, is light an magnetic field depended on what frequency? Does this mean light is an magnetic field? Wouldn't we then be able to bend light with magnets?

[@ratvomit874]

This concept of interference actually made it into a Chinese drama some years back, where someone was shot dead in a room and the police thought the witnesses were lying because the witness furthest from the scene reported the loudest gunshot while the nearest one never heard it. Eventually the police brought in a science professor to help and it turned out that the room had two windows open causing the gunshot sound to interfere with itself, creating that counterintuitive result whereby the nearest witness was in a spot of destructive interference and the furthest one was in a spot of constructive interference

[@TimoBlacks]

lol that's bs. but i like it.

[@DrDnd4nyer]

Amazing video! As someone who did a science fair project on holography in high school (in my senior year 1982-83), I spent lots of time working with a ruby laser in dark rooms! I'm happy to say I did make a few viewable holograms and won first place. Just subbed to see how the future experiments go!

[@lelouchvibrittania5172]

This video is brilliant. The way you went about setting things up and the smoke screen idea at the end was wonderful; I wish more lab classes actually do the smoke thing to teach polarization. This is why I love physics. Congrats and I look forward to more of your content!

[@jennifer7685]

Right?! When you see how easy it is up, it’s stunning that it isn’t done in every high school. I also want every school to go over additive light where they use three different flashlights to show how red and green make yellow.

[@interloperdrones1172]

You might find Theoria Apophasis most enlightning. Go learn about real science there

[@debarshidas8072]

0:25 Man, that strand of hair must have a really good sense of humour.

[@ctvxl]

This all gets very sticky, however, if you repeat the experiment using not light, but instead particle streams such as protons or electrons. You get the same exact interference pattern with the dual slit. Unless you believe protons and electrons are waves, you can not account for this using wave theory...

[@matthewmurdock4875]

Thank you. I was shaking my head in disbelief she didn't bring that up.

[@lightstrands2855]

We did a similar study and published our work on it about about 2 years ago. We have a KZbin presentation on it which you can find if you lookup “light strands not waves”. We came to a different conclusion that this supports particle behavior not wave properties. These light strands are distinct linear tubes of light. Wave interference would create fuzzy patterns. These light strands exist within and pass through hollow tubes. Waves shouldn’t. Light strands can be focally blocked without distorting adjacent or downstream strands unlike what would happen with waves. Would like to get your thoughts on this. There is a link to our papers on the channel. Also have paper and KZbin video on how Poisson spot can be explained by particles, not waves. If interested and have equipment would like to collaborate on doing this experiment with individual photons and hollow tube channels on the exiting side. If particles should see fringe pattern. If wave should see nothing. Hope to hear from you.

[@rudraksh111]

So sir from the perspective of waves poisons spot can be explained I guess😅

[@rudraksh111]

To better explain my thoughts what I see is that there is no difference in wave and particle I repeat NO difference And I AM NO MAD PERSON if you want I can explain it the difference is External that is environment. Etc

[@schitlipz]

Yay. I also tried guitar strings a while back and they work good, the thin ones anyway and they come precision made width, so you can calculate stuff with that. And I guess it's been noticed that oblique angle create easier-to-measure bands. TBH I thought moving the screen closer and further would create a merge and spread type of effect, instead of rays. I guess pop culture imagery would be the big alien ship in Close Encounters the way the lights went about it with neat effect.. or like a checkerboard style pattern across the plane. Glad that's cleared up. (Shine your red laser through plastic money where there looks like a circle, pinky width).

[@theeclectic2919]

Actually, she should try it using fishing line. It's not opaque, therefore, the light would partially go through the line.

[@ColinWatters]

I've never had a problem seeing light as wave but it seems to me its particle like behavior is equally interesting. For example ive read that if you turn down the brightness so you are sending one photon at a time through the double slit experiment you still get interference. It's as if each photon goes through both slits or both sides of the hair and interferes with itself.

[@stargazer7644]

That’s where the pattern comes from. It isn’t from photons interfering with other photons, it’s from photons interfering with themselves.

[@tykemorris]

Yes, each photon interferes with itself.

[@nonplayercharacter6478]

So they say, but it's not possible to build a device that emits one photon at a time.

[@stargazer7644]

@@nonplayercharacter6478 It is trivially easy to build a device that emits one photon at a time.

[@nonplayercharacter6478]

@@stargazer7644 Oh? what is that device? And why haven't they done the double slit experiment with it?

[@citizenY]

Exceedingly human malfunction to mistake Light with Illumination.

[@Jonemode]

Nice presentation! It was cool to see the beams of light using the smoke machine. The double slit experiment is pretty mysterious in that if you fire electrons one at a time through the slits, they somehow still interfere with each other. And if you measure which slit the electrons go through, they don’t interfere. By measuring the result, you change it and no longer get the interference pattern. That’s the part that makes me most curious. Would be great to hear your thoughts on it !

[@michaelbrininstool2627]

Electrons?

[@chrisbriswrites]

Because, once a quantum wave is touched by an outside source, it loses its quantumness.

[@theo3000]

This video demonstrates simple wave interference. It never demonstrated the wave-like behavior of individual photons, it only described it. NOT an at-home double-slit experiment..

[@rodschmidt8952]

@@chrisbriswrites It gets "thrown into an eigenstate" of the measurement, in the words of McKeown. So it still has its quantumness, it just has a different shape. It now has definite position (if that's what you measured) and indefinite momentum. OR it has definite momentum, if THAT'S what you measured, and indefinite position.

[@steveswhirld]

hows about using a double double 4 slit experiment and instead of using a smoke machine ;blow marijuana smoke on it

[@harant8036]

Thank you for the inspiration! I am surprised that this famous experiment was so easy to recreate with only one hair from my head and 10 euro laser line level which I forgot I had in my drawer. You don't even need to buy a special equipment for the proper double slit version. Instead, you can attach a hair directly on the laser and carefully put a piece of insulation tape from each side of the hair. It is really amazing to see the wave pattern with your own eyes even after all of these quantum related youtube videos :)

[@adamphilip1623]

Fantastic video! I've never seen this kind of demo before, looks amazing! I've been really impressed with the increase in quality of your last few videos, thanks for the great content, keep up the good work!

[@LookingGlassUniverse]

Thank you so so much!

[@huaqero5458]

If these were waves I would expect the bright and dark spots on a screen to fluctuate/change place as the screen moved away from or near the source. But this is not the case here. We see continuous beams stemming from the slits. These are particles.

[@SciD1]

Yep, simple reflection.