Sixty Symbols - 2013-07-11
Professor Merrifield largely "uncut" discussing refraction... Professor Moriarty on the same subject: http://youtu.be/YW8KuMtVpug Visit our website at http://www.sixtysymbols.com/ We're on Facebook at http://www.facebook.com/sixtysymbols And Twitter at http://twitter.com/#!/periodicvideos This project features scientists from The University of Nottingham http://www.nottingham.ac.uk/physics/index.aspx Sixty Symbols videos by Brady Haran A run-down of Brady's channels: http://bit.ly/bradychannels Mike Merrifield tweets at https://twitter.com/ProfMike_M
"Barry the beam of light"?? Surely his name should be Ray!
right? barry should be reserved for beams of particles made of 3 quarks.
Jim Beam
Maybe because it’s a baryon ;)
Ma Ray Sue
Oh no you can't call a polariton ray that just wouldn't do.
All I wanted to know is why light traveled a bit slower through a medium such as glass, but now I find myself with all these questions about quantum physics and the nature of fundamental reality, and it's a bloody mess.
And he's not even right 😂
@Jess Stuart - What happens to the light particles? Cuz it's a particle AND a wave, right?
@Jess Stuart Hi Stuart, sorry to comment to a post of yours two years ago, but I think you are mixing two models here: Your first electron oscillation explanation can not be right. remember glass can pass multiple rays of light at once, so if the electrons are busy, re-radiating EM from one stream of light out of phase, but at the same time doing it with light from another direction or color, they would both interfere, mixing the two beams direction and color!.
This is purely to be understood in Quantum Mechanical sense, it is the wave functions of the whole electron that gets mixed with with the wave function of the photon, so it is this new hybrid wave function that propagates at a lower speed, but preserves all information, regardless of what other light it is mixed with on its way. It is conservation of information, in action.
The more you know... the more you're puzzled.
that' what happened to physicists back in ~1900! xD
Weirdly enough, that last explanation makes the most sense
It's Feynman's Path integral formulation ("sum over histories") and forms the basis of QED.
@Billy Willy I think he was referring to the 'Polariton' explanation.
@DANG JOS I don't know, to me both quantum mechanical explanations make more sense than the Newtonian one. It didn't seem like he ever said why having all the other fields around slows light, just that it does.
@Nathaniel Graham Pretty sure the reemitted EM waves are phase shifted, and this combines to form a slower wave. Also, the path integral explanation doesn't really have an intuitive feel for why it travels slower.
1:42 - No that's not a reduction by 40 percent but 28.57 percent lol !
Wrong! The way for the Lightphase becomes 30% longer, because the direct way is blocked tough the electronconfiguration from Silicium. So the Light will not becomes slower, the Way for the Lightphase becomes longer. Nothing else. This guy here is the greates "Wanna be Professor in Physics" which I've ever seen.
@G4mm4G0bl1n You're joking right??
@DANG JOS He's just trolling
@Jan Sten Adámek Yeah I had a feeling
Yep, the speed slows down by 29%, and it takes 40% longer to exit the glass as a result. :-) It's simply a question of what is the reference quantity: %change = (new thing) / (reference thing) - 1
i love how he got quiet at "traveling faster than the speed of light" xD
thats kind of a taboo
I wear glasses from my birth, are you telling me i've been sort of living in the past all that time ? i am 28 y.o now
@carultch It's not insignificant for humans! Never jump into a swimming pool just because it LOOKS shallow enough. That's due to the light being bent, and for anyone who hurt themselves because of this effect, they won't be saying it's insignificant!
@Rob Blakemore damn right, next time i am losing a bet with a rock-paper-scissors game, i will blame it on a headstart of 14 picoseconds that my opponent had!
😊
@δτ I was wondering about that. Percentages are relative to where they're applied. A 20% discount needs 25% added to the actual price charged to undo. Not knowing exactly how that 1.4 refractive index applies, I couldn't really comment about it.
Valentin Degenne if light didn't slow down when it went thru your glasses you couldn't see.
we hope you can make a video about Polaritons.
ALice Akkush
هاي
I hope so, too
... and Magneto, and Cryptonite! :D
What, whaaaat aareeee thooseeee??
best part of this video in my opinion is at 16:04 as you try to imagine Brady's face before vocalizing his question.
8:40 it prefers to be called a differently abled light wave :(
"How'd you expect me to edit this?" :D
Thank you for this very informational video.
The shown material is completly wrong and missunderstood from the original postulation from Albert Einstein. The Light becomes not slower. The radiant from the longitude movement will be longer. So the Light becomes not slower, the way for the Light becomes longer!
Lightspeed is constance and fix! Thats the first rule of E=mc². Baddest fail I ever seen and what is he, a Professor? Where is the Vending Machine for 25¢ to get the title?
@Joel White
The Explanations of him are useless complicated. I can show you a picture which explains all what he said over the complete video and more.
lol...i bet u are more confused now and didnt understand a sh!t!!!
can u pls explain what actually happens cause i am really confused
Cheeki Breeki I think it's * informative...
08:30: The explanation at this point in the discussion is hard to imagine... Does anyone know of a link that shows an animation of this wave "addition" process.
Did he make a mistake? I think he meant 40% faster in vacuum, not 40% slower in glass (ya, they aren't the same).
150 is 50% more than 100 but 100 is only 33.3% lesser than 150.
Tell me if I am wrong.
When you say something is 40% smaller, you are saying that you divide by 1.4 to achieve your result. For example, 10 is 40% lower than 14 -> 14 / 1.4 is 10. 14 is 40% larger than 10 -> 10 * 1.4 = 14.
so 71,43 is 40% less than 100??? how did you come to this conclusion. by what logic?something is 40% less, it means it's -40% of the original value. If 100 is original value, then 40% less is 60. How did you come to "divide by 1,4"? makes no sense? The only way I can see how would you come to this, is that you thought that if to add 40% you need to multiply by 1,4, then to take 40% you need to divide by 1,4 (???) No.
@AMGwtfBBQsauce If you do what you say, then to find something 100% smaller you would only divide it by 2? That would only cut it in half. If something is 100% smaller, it's value is 0. So to use your example, to get something 40% BIGGER you are right that you just multiply by 1.4. However to get something 40% smaller you multiply by 0.6, and so the op is right that there is a difference between the two.
Another way to think about it is that if something is 40% smaller, that also means it's only 60% of the original size.
Yes, he made a mistake. It is 29% smaller, not 40% smaller, if the ratio is 1.4.
You're wrong - 100 is 33 and 1/3 percent less than 150. You are off by 1/30 percent.
Time to start using 'Polariton' in sci-fi stories :3
I found the last model to be the easiest to understand. Photons becoming Polaritons, no longer behaving like photons, is not as mind-bending as a photon being everywhere at once :)
I read it over the internet that "For every complex problem, there is an answer that is clear, simple, and wrong."
Sure, but remember that this Polariton thing is just a model, a mathematical symbol... which is also true of a photon. Quantum theory shows that in any measurable sense, particles that are small enough to be subatomic move according to probability waves. So in fact the term "particle" is misleading, but it's very difficult for us to wrap our minds around the idea of the universe and all its contents including our own bodies and brains as consisting of probabilistic fields of "energy", whatever that is...
You think that is mind-bending? Cause you are also everywhere at once.. but just a little bit :D
@Cretaceous Steve here's a simple solution (to having to wrap our minds around quantum physics): don't. How physicists model reality has no bearing on how reality actually is, as explained by both the prof and you just earlier in your comment.
I do hope we get a simpler way to interpret these models though.
I'm so glad we get to see Brady more often. It really improves the videos.
This is one of the best explanations I've ever heard on the subject.. And definitely the clearest of them.
8:39 When you can’t think fast enough to get around it
soon I hope - been a bit busy here!
There is a little math error at 1:38.
Light travels 40% faster in vacuum than it does in glass
The reverse with same percentage is not true though.
In glass, the speed is 1 - 1/1.4 = 29% slower than in vacuum
Percentages man :P
14:26 just to mess things up a little further 😂😂
This is one of my favourite videos on YT, of all time.
A huge thank you to all involved in its making.
so many experts in the comments, makes you wonder why they even watch this if you already know everything XD
This is the most amazing thing I've ever heard! were you serious when you said all of that?
8:40 funny hearing words used how they're supposed to be used.
Thumbs up for the interference pattern!
Beautifully explained. 💫✨💫
"Your videos are Humanity's treasure".
8:30 but light behave as photons when interacting with matter
I learned a semi-classical polariton explanation when I took Relativistic Electrodynamics in college 8)
Very interesting. First time I've grasped quantum vs classical models
Atlas Of Creation? WTF????
Gryffster i hope that book is there just for those moments of fun...
It seems that fear of death reaches not only average people, but also physics?
Late response, but he talked about it in another video. He got sent the book by some creationist group. It's a thing they do, apparently.
Yeah, I had to look this up...
I had read the pinball theory a long time ago, so thanks for clearing up that misconception for me.
13:00 does every possible path also include going back to the interface from the photon started?
7:00 also the thing with direction still applies in case of light being absorbed by atoms and emitted back. it can come out at any angle. right?
i'm a bit thick but... if they go slower through glass, then they lose momentum, but when they exit, how do they speed back up......
@hOREP < Not necessarily, there's an average even with all the bouncing, and the more material it has to pass through the greater the "slowdown", which is so minute that it's virtually imperceptible by human eye, only instruments can measure it. Also this explains how light doesn't actually "slows" down then speeds up once it exists the medium, it merely takes a slightly longer path due to the bouncing/interference waves. Oh, I didn't make this up, smart physicists have come up with this explanation.
When light enters the glass, it excites electrons and makes it move having its own waves. When the waves of light combine with the electron one it gets slower and when it exit the light is back to itself.
@Great job Its mass time velocity.
@Calculated Risk - If it is a particle and a wave, doesn't it have to have mass?
Classical explanation: light is not a particle, it is a wave, and has no momentum in the sense that it has no mass, its speed doesn't change as much a new wave which is the sum of the light and the wave that is produced by the movement of electrons (because of the light's entry) is slower than the light on it's own
Quantum explanation 1: light is both a wave and a particle, but still has no momentum either way, and we are still using at a "new wave" that is slower, except now this wave comes from the multiple paths light can take rather than the movement of electrons combined with an absolute path
Quantum explanation 2: when light enters a medium, the maths gets so crazy that it's a completely different system, if you solve this system you will get a particle that has mass so is slower
All of these explanations rely on the maths that happens in the medium, so when light exits the medium, it just returns to normal.
It’s simple, photons are devious!
Just when I thought i had some idea how this works, along comes the polariton. Never heard of it. Maybe I should quit trying to understand.
My question is; is the speed of light the same after in travels through a matter like glass? Suppose we have a piece of glass and the light travels through it. Now, we also have the light that did NOT GO THROUGH THE GLASS. This light did not go through the glass, and is being joined by the light that DID go through the glass. Will we be able to measure the differences between these two now DIFFERENT lights?Curious
Thank you Professor! i really love u
8:10 So we can say Electro-Megnatic Inertia? (from @AstroGate بوابة الفضاء)
Once light exits the medium (e.g. glass), does it have the same energy and speed as it did before entering?
How does a single photon behave through a Glan-Foucault prism ?
"How do you expect me to edit this?" ... asked the Grand Editor of Reality (as well). :-)
In other words, that question really points to biggest problem of physics today: "Let's find a universal model, p-p-p-pleaaase." :-)
This video is really awesome, I really appreciate these being posted. Thanks Brady. I learnt something, today and every day!
Can't we test the effects of gravity on polariton the same way we've tested it on light to prove their existence?
12:26 if this is true, how come a narrow beam of light seems to go in a straight line over all? like Professor merrifield said in 4:35?
+Sean Thrasher Just watch the video
the last time i heard the word "treacle" was when gordon ramsay showed me how to make cocaine out of coca-leafs
Brilliant interview!
He's fighting Sherlock Holmes!
That it is my friend, that it is!
Thomas Drowry - 2016-11-22
Professor Moriaty , what a great name.
Paul McDonagh - 2019-08-02
MORIARTY he's australian they dont pronounce the R. Its an irish name originally
Redcoat‘s Return - 2019-09-03
Elementary my dear Watson!
iguju progress - 2020-02-20
like some evil genius.. :D
R Sinclair - 2020-02-21
lol
R Sinclair - 2020-02-21
Elementary