There's a classic sci-fi story about glass-like material that is so dense it takes ten years for light to pass through. The idea is that you store a nice view, say from an alien planet, and sell the "glass" after ten years to someone who wants a "living window" to another world.

@elio7610

2 ай бұрын

so the view lasts for ten years but also takes ten years to store. would it just be black when the glass is brand new?

@notsam2270

Ай бұрын

​@@elio7610 should be, but i'm wondering about the corners which light could possibly go through in a shorter time frame, causing weird distortions not to mention light bouncing off of materials and all of that, making the sight a blur

@PC_Simo

Ай бұрын

@@elio7610 Probably 🤔.

@effestop

Ай бұрын

mindblowing!

@PC_Simo

Ай бұрын

A literal window to the past 🪟.

Even without the need for a vacuum, he finds a way to use the vacuum chamber for experiements. What a legend.

@mgancarzjr

2 ай бұрын

Should have measured the time of flight though a chamber full of air then vacuum.

@bakedatbeen

2 ай бұрын

Exactly, this man tries to make the most of his vacuum chamber in all his videos. That's one of his prized possessions or smth and why wouldn't it be

@kricketflyd111

Ай бұрын

If I lived next door, I would want to be his helper free of charge.

@FractalShoggoth

Ай бұрын

When you buy a shiny new hammer, everything starts looking like a nail...

@kricketflyd111

Ай бұрын

@@FractalShoggoth only in a vacuum

Appreciate all the free education you provide.

@ColtonBrummell

2 ай бұрын

I second that motion! The Action Lab is excellent and awesome!

@cutiepiepanini

2 ай бұрын

I second that motion! The Action Lab is excellent and awesome!

@westonding8953

2 ай бұрын

Absolutely!!

@alien3200

Ай бұрын

But his channel is dead 😢

@ColtonBrummell

Ай бұрын

@@alien3200 no u

This is a hell of a rabbit hole, the mathematics behind it is crystal clear, models can show aspects of whats going on, but a complete intuitive explanation of whats actually physically happening is incredibly difficult to grasp. Like a lot of things in physics the more you learn the more you realise the naive explanations just dont cover the full range of weirdness of it all.

@b.s.7693

2 ай бұрын

Exactly my feeling. The problem is, you can visualize the behaviour only for a very tiny section of the whol thing (1 wave cross section + 1 electron). The real process in 3 dimensions and for multiple elctrons and waves is overwhelmingly more complex. I can't imagine anything of this tbh.

@Dipj01

2 ай бұрын

I picture this as like the light gets pushed backwards a bit when it comes across a medium, and then it continues to move at c. But because it got pushed back when it touched the medium, it'll reach the other side a bit late even though it's still moving at c. So from our perspective, light seems to be slowing when in fact it just got offset backwards a bit.

@duran9664

Ай бұрын

🚩This is why many people have started hating scientists 🤢🤢🤮They lie & manipulate with ZERO shame🤢🤢🤮 Light NEVER slows😡It just scatters in denser material, which makes it takes longer time to pass through🤏

@AncientMysteriesAndInnovations

Ай бұрын

​@@Dipj01 interesting thanks

@RoySATX

Ай бұрын

" the mathematics behind it is crystal clear" You've earned a gold star for that line!

0:29 "the most famous constant in the universe, the speed of light, named after the speed of light" made me giggle ( cannot say cracked me so hard coz some guys do not catch the vibes)

@PC_Simo

Ай бұрын

Yes 😅. Also; the constant, called: ”the speed of light”, is actually just the speed of light, in a vacuum.

@thingsiplay

Ай бұрын

@@PC_Simo It's actually not the speed of light that is the constant. The actual constant is the speed of causality=C. This is the speed of how fast a change can occur. Light itself could be infinite in speed, but is limited by the speed of causality.

@isbestlizard

Ай бұрын

Cannot tell if joke, or AI generated script... >.>

@PC_Simo

Ай бұрын

@@thingsiplay That’s fascinating 😮! Might that be connected to Planck time? 🤔

@jasonharrison25

Ай бұрын

​@@thingsiplayfrom our prospective. From lights prospective it traveled to its destination instantaneously

Totally off-topic comment, but please consider to have your cheek checked for skin cancer. I have seen such a slight discolorisation before in someone, and it turned out to be cancerous and was indeed surgically removed.

There are lots of "authoritative" misstatements on KZread on this topic. I'm glad you reference 3Blue1Brown and his illustration of Feynman's explanation ... the best I've seen. Nice demo, as usual!

@whuzzzup

Ай бұрын

3Blue1Brown indeed has some good animations on it (KTzGBJPuJwM & aXRTczANuIs). I also like FloatHeadPhysics (JZOn1B8K8mA) although the "pull back" animation isn't that good - it has some really interesting comments though. I don't like the FermiLab version as it does not really explain it properly (well at least as you can say "properly" as of course it's far more complex in real life than any of those videos imply).

@SahilP2648

Ай бұрын

Someone explain to me how this works as a photon of light. Whenever I see videos or explanations done about this, everyone starts showing waves. While I know light behaves both as a wave and as a particle, if we don't know how an individual photon 'knows' it transitioned into a different medium, there's a possibility this wave theory is also incorrect. Also, the way it's explained here and everywhere else is that a single atom's electrons changes the wave and then it gets passed on to the next atom's electrons.... but isn't this additive? If that were the case, enough length of the material would make it completely opaque, and well before that the refractive index would be observed as being dynamic. It makes 0 sense that this is considered the proper explanation.

I just had a long discussion with my wife about how come light slows down through different mediums when it's massless and so can never slow down - then I open my laptop and this pops up. Now, that really is strange...

@tomr6955

2 ай бұрын

That stuff happens a lot to me too.

@esecallum

2 ай бұрын

you being spied on by your phone and any mic on laptop

@Randomstuff77654

2 ай бұрын

Google heard you then forced action lab to make the video

@solanumtuberosa

2 ай бұрын

I mean, as long as it has speed it can slow down.

@NamVu-im2xm

2 ай бұрын

That is just a normal thing, no need to freak out. Tons of information fly through our head everyday but we never give them a damn. When you focus on one topic, you'll pay attention to information of it, if it fly through your day again. And then you just think "Wait, does universe listen to me?"

We need more optics experiments 🔥

I think addressing "What makes a material transparent?" would have been a good addition to this video. Great work.

@bosslca9630

Ай бұрын

Wait- holy hell this just gave me actual virtigo. This explanation means that in the truest sense of the word, no mateiral is transparant, it's simply a material that has an electromagnetic-wave-propagation effect. 'Air' would be a good case study becuase I'm uncertain if it has enough density to compare to something like Water or Acrylic... but except in a true vacuum, you will never receive the electron that the originating atom created... And in low density fluids... how deeply could an EM wave penetrate before it MUST hit another atom to propagate and potentially delay? Your eyes are constantly re-propagating EM waves so for that matter... *head asplode*

@georgkrahl56

Ай бұрын

Methinks this question has the wrong direction. It e.g. does not explain why vacuum is perfectly transparent. And it gets difficult to explain why water is transparent and snow is not. The question is why some material is not transparent.

@peglor

Ай бұрын

@@bosslca9630 A vacuum, and gases in general, will be transparent because the photons can actually pass through without interacting with anything. Gases are mostly empty space, part of the reason their densities at normal pressure are so low compared t liquids and solids where the atoms do contact each other. There is some atomic interaction between light and gases - that interaction is why the sky is blue for example.

@duckofdeath3266

Ай бұрын

@@peglor Compared to vacuum, air is incredibly dense. It is as dense as it can be without increasing the temperature in its space. It is so dense it will knock you over if it travels as 20m/s. "Speed of light" in materials is indeed a conundrum that very likely proves we don't understand what light is. It is neither hardness, element or state deciding if a material is transparent. Coal is the perfect light stopper, unless you compress is insanely hard. Crude oil is also blocking almost all light, until you increase the mass of the molecules and turn it into plastic. No metal is ever transparent, unless you "fix" it in a ceramic grid. The reason light "slows" down in different materials is probably because it never travels through it. It's only the waves going through. Sort of like sound through a wall.

@kopiller

Ай бұрын

Thenproblem is that youbare thinking in particles, everything is transparent and opaque, it depende on the wavelenght, the window of your microwave oven is opaque to microwaves but transparent to visible waves.

I'm a new sub...delighted to find you answering many questions I've had for years!

Great video! Props for doing the shoutouts at the end, I thought of those videos instantly when I saw this!

I'm glad so many science KZreadrs are tackling this. Most quantum things require many different analogies and explanations to illustrate an idea without using math. This was probably the most concise yet complete explanation I've seen yet.

@duran9664

Ай бұрын

🚩This is why many people have started hating scientists 🤢🤢🤮They lie & manipulate with ZERO shame🤢🤢🤮 Light NEVER slows😡It just scatters in denser material, which makes it takes longer time to pass through🤏

@Canetoady

Ай бұрын

@@duran9664did you even watch the full video 21/4/2024 Sunday 4:21PM

You made a very deep question very accessible. The true speed of light divided by the speed of light in the material in question. Great job James. The speed of light through the material in question IS the true speed of light... through that material

Very interesting! Upvoted for mentioning 3B1B video on this topic, which is outstanding!

You made a very deep question very accessible. Kudos!

@duran9664

Ай бұрын

🚩This is why many people have started hating scientists 🤢🤢🤮They lie & manipulate with ZERO shame🤢🤢🤮 Light NEVER slows😡It just scatters in denser material, which makes it takes longer time to pass through🤏

@Canetoady

Ай бұрын

@@duran9664did you even watch the full video 21/4/2024 Sunday 4:21PM

@hewaahmedmustafa8027

Ай бұрын

these preprint papers claimed reversing entropy. What do you think about this? Experimental Demonstration of Energy Harvesting by Maxwell's Demon Device And An Autonomous Mechanical Maxwell's Demon

Great job James you have done a great job on the action lab. You are so good.

I was always puzzled by this question. Thanks for your great explanation

You should attempt at a zero point energy experiment in a vacuum. Using the Casimir Effect.

I watched the 3Blue1Brown video recently and sort of understood it, but your explanation is much more understandable. Thanks.

I love it when good science channels shout out videos from other good science channels. Your content might be targeting kids but that's honestly a good thing with how good your quality is :D Its hands on broken into simple small components explained using simple terms and showcases that are using real life models. Keep it up! you def deserve the 5mio subs

*Light slows down in Diamonds by 25% which is why they have so much "fire".*

Fantastic video! I really love these strange observations of light. Especially in relation to the very cold, the very dense, and now the very electric. Sometimes I wonder if the apparent expansion of the universe is a function of the lensing of light through varying degrees of cold pockets, transparent matter, and gravity wells. If a galaxy we observed 100 years ago seems farther away, it might not be, but the light red-shifting towards us from it might be running up more hills to get here than it used to, because of the vast movements of new anomalies in its path to get here. Edit: But that would mean we should observe some cosmic neighbours seemingly getting 'closer' to us, if their light was once struggling through more to get here than it is now...

Always great stuff! And really appreciate your recommending other channels! KZread is always throwing new ones at me and they are not always worth much. Nice to know in advance!

Really goes to show how much depth there is to the things we think we already know. I had no idea about this

As a long time engineer and physics enthusiast it is often so easy to forget things like these are not common sense to everyone. Great video on the topic 🙂

Thank you. What is the specific app you used for measuring distance to sticker on table?

A beautiful explanation. I had heard the claim that the photons were constantly being absorbed and re-emitted, and that that's what caused the delay, and I'd heard the statement that no, that wasn't accurate. But I hadn't heard what the real explanation was. Thank you for providing it.

@DrDeuteron

2 ай бұрын

you can do this w one photon, but the absorbed an remitted is very misleading. The photon remains coherent , which wouldn't work if it were absorbed and remitted classically..but then it gets into more semantics of coherent vs incoherent scattering. The juice is not worth the squeeze,

@duran9664

Ай бұрын

🚩This is why many people have started hating scientists 🤢🤢🤮They lie & manipulate with ZERO shame🤢🤢🤮 Light NEVER slows😡It just scatters in denser material, which makes it takes longer time to pass through🤏

@oasntet

Ай бұрын

A very small portion of the photons actually are being absorbed and re-emitted, it's just that the majority are making it through and just being interfered with over and over again. In other mediums, the ratio is different, and so transparent-ish things can take on colors.

@whuzzzup

Ай бұрын

No please forget about this idea. It's completely wrong and bogus. Just think about one thing: Why would the re-emitted photon fly in the direction it needs to fly and not in any other random direction?

Nice demonstrations with the ToF Lidar

Great demonstration and explanation. Worth noting that the "true" speed of light is measured in a vacuum, so the phone's software already compensates for the air molecules affecting the beam. If you used it to measure distance in a vacuum it would underestimate.

@badbasic

Ай бұрын

Oh no, he might need to use his vacuum chamber, and he never uses it😊

That is a fantastic video. Thank you!

fantastic. so simple yet so deep.

THIS WAS SO AWESOME! I ALMOST UNDERSTOOD IT!!! 😃

Nice explanation. I like that you show it experimentally with cell phone lidar

Fantastic video as always! I still don’t quite understand, but I’ll take your word for it 😊

This excellent vid reminded me of one of my favorite science fiction short stories, "Light of Other Days", by Bob Shaw. (1966) About "...a window made of Bose-Einstein Condensate that slows light to a snail's pace.", ....thereby allowing it to be set up in, say, a beautiful wilderness scene, uncovered for 10 years to 'record' that, then sold to people who wanted that scene to be 'played' for another 10 years in their home, as that original light finally makes it through. (Not to be confused with Arthur C. Clarke and Stephen Baxter's "_The_ Light of Other Days".)

@robertgreen7593

Ай бұрын

That could make a good murder mystery element. Where the owner of the window is sitting their watching the view and he sees someone being murdered ten years ago.

@scollyer.tuition

Ай бұрын

​@@robertgreen7593Bob Shaw wrote another "slow glass" story called Burden of Proof that is vaguely similar to your suggestion.

Fascinating video.

Good job - my compliments. I have an issue with the idea that the incident photon pumps an electron in the acrylic material then continue on its merry way unchanged to later couple with the photon emitted by the pumped electron as it drops back a level and create a third wave front that is slower. I understand the concept of the standing wave - well. think I do at least) The only way for the photon to pump the electron is to dump energy into the electron. The energy level of a photon/electron is in discrete steps. The photon either has to dump all its energy and disappear or dump a significant part of its energy, then drop to a longer wave length (lower energy level) to continue on. This raises the question of the recombining of photons of different wavelengths recreating the same color of light as the primary product (ignoring scattering) . As a ham radio guy it suggests to me that recombination should result in an I/Q modulation with three different wave lengths appearing at the output (as a mix of colors). This all proven by Major Armstrong at much longer wavelengths..I will let the standing wave slide for now. 73

Your content never ceases to amaze me and serve as great education tools!

@hewaahmedmustafa8027

Ай бұрын

these preprint papers claimed reversing entropy. What do you think about this? Experimental Demonstration of Energy Harvesting by Maxwell's Demon Device And An Autonomous Mechanical Maxwell's Demon

@mdkamruzzaman8605

Ай бұрын

That star you have in your name is kinda rare

@westonding8953

Ай бұрын

@@mdkamruzzaman8605I am a paying member of his channel.

wow you always can show something in such creative manner

3B1B's and LGU's were more intuitive for me, but this video was good. And I loved seeing the acrylic blocks; your experiments always make the concepts a lot more concrete.

You're my favorite science teacher

This is one of the best takes on the topic. Much is semantics. Yes, light slows down in acrylic, and when we say "the speed of light", we mean c/n, and don't appreciated "achtually's". (we: ppl who've built Cherenkov detectors)--it doesn't mean we think gamma rays slow down too. It's perfectly fine to use Maxwell's eqs. in media (the ones with D and H in addition to E and B), where the permittivity is > that of free space. Ofc that is a bulk model and ignores atoms...which you can do since the wavelength is much bigger than an atom. Nevertheless, the most unambiguous approach is to use Jefimenko's eqs (equivalent to Maxwell's, but manifestly casual). This is gives you the *correct* physics view that changing E fields do not cause B field (and likewise for dB/dt -> E, an a-causal idea). Rather, the fields at a point/time are *only* due to charges and currents on the past light cone, so effect from cause propagates at "c", but because the medium, the presence of max E-field appears to move at c/n. Note that nothing is moving, waves don't propagate...only effect propagates from cause on the past light cone. In media and in vacuum, the wave description is just a model of an emergent phenomenon--I hate to use this cliché, but it's correct here: like a Mexican wave at soccer game. There is no wave, just people standing up and sitting down in what looks like a wave, so with that: the wave does move slower than c.

@EffectualPoet

2 ай бұрын

Holy sh-t bro, you writing books on YT.

@DrDeuteron

2 ай бұрын

@@EffectualPoet well, I worry about this one, and I got some work churning on the other computer that needs attending every 20m. If I put on movie or sports I'll forget about the work...this is actually max efficiency.

This channel (and others mentioned in description) are the real gems of KZread ❤

@duran9664

Ай бұрын

🚩This is why many people have started hating scientists 🤢🤢🤮They lie & manipulate with ZERO shame🤢🤢🤮 Light NEVER slows😡It just scatters in denser material, which makes it takes longer time to pass through🤏

@Canetoady

Ай бұрын

@@duran9664did you even watch the full video 21/4/2024 Sunday 4:21PM

Quadrature shifting. Used to modulate and demodulate radio waves. Very interesting stuff. I work with RF for hobby and experiment purposes and have come across this concept.

Wow that’s amazing! 👍

Great explanation and animation, I wish you would have really hammered down the point that its a result of continuous phase change "backwards" with some sort animation of the continuous phenomena

A question I had for a long time and u made a video on it. 😃

This channel is everything Veritasium ever aspired to. Without all the fake videos for money.

@user-kc1dn6ik7x

2 ай бұрын

💀💀☠☠

I was researching this for a while long ago but only read that atoms absorb and re-emit light. Thanks.

Awesome explanation.

U never fail to entertain me with science

The explanation was known to me as it's the standard one, but I always wondered about three things that so far nobody answered: 1) The secondary waves created by the "wiggled" electrons move along with the incoming initial wave. But what happens to those waves once they all exit the glass on the other side? They all still move with c, but why does the "kickback" now reverse and the wavefront no longer (apparently) slows down? 2) You talk about "second order propagation" - ok but why are there no third, fourth,... until light slows down to 0? 3) Wiggling an electron needs energy. Thus a photon should lose energy and thus change its frequency (hf). Why does it not do that?

@marianl8718

Ай бұрын

A wave decrease in amplitude when it loses energy, not frequency. On a microscopic scale, the release of energy takes place in the form of quanta, which are released in their entirety. At least that's what quantum physic says. Yes, there might be a wave going through glass without slowing down, but only at the beginning, until the transient regime passes.

Got me curious, considering that atmosphere can affect the speed of light, does the lidar system on the phone notice a distance difference from sea level or higher up? Perhaps a vacuum chamber could help.

7:53 Looking Glass Universe videos on this topic are great, I can recommend them.

This brings a great perspective to understand what’s going on. Essentially light isn’t slowing down, it’s just taking extra steps as it moves through the medium, thus taking more time to exit through it, creating the observation of it moving “slower” Thank you very much for sharing with us and making something like this comprehensible

The simplicity of demonstrating the speed of light with your phone app is stunning! We can NEVER directly measure the speed of light, only indirectly by reflection.

Great video! I have a question: What gives photons their energy to move through space-time? Is this energy intrinsic to photons, or is there a process during its moment of emission that gives the photons their energy to travel? Thanks!

I've actually watched all of those videos talked about here from both channels trying to understand this, and i think i actually do now. For the most part, still some ways until it's intuitive. But it's right there on the tip of my intuition. haha.

if you would use 2 walls of that vacuum chamber, that would be enough to see the relativistic effect of light. We could see a little delay on the moving image below the walls. You should try something more that could make the relativistic effect visible by just eyes.

cool! didn't even know this was a thing!

Us:Hey does light ever slow down? His answer: Yesn't

Now i'm curious to see how the difference between constructive and destructive phase change in a dual slit experiment under various dense materials(air, water, salty water etcetera).

you have to try an experiment where the IR laser goes though transparent materials of different densities, for example a transparent cylinder filled with air at different pressures (take precautions), and the same optical path. If you can use solid lidar IR-transparent materials with different densities, even better.

learned about what lidar is and how it works, thats a cool technology

What was the measuring app you used with your phone?

This is cool. Thanks! So the photons appear to be moving slower between point A and point B because they are bouncing around at the speed of light as they travel between A and B when encumbered by some medium that has mass? But I'm still perplexed by the question of whether photons 'experience' time in the first place?

I could listen to a 10 minute evil villain monologue about the speed of light

This explanation is very interesting. Good Job. This knocked a couple of cells together and sparked a thought: Passing it through materials would be a wave resistor... I wonder could there would be a way to make light transistors using prisms or ....

@mkammyd

2 ай бұрын

Or lenses?

@JumboStiltskin

2 ай бұрын

Optical Computing is a field of ongoing research, and there is a lot of fascinating work being done in building logic mechanisms using light’s properties. Typically these techniques leverage quantum effects such as wave interference and polarization - check out Huygens Optics channel

@azy6868

2 ай бұрын

If only it were that easy. Photonic logic is the use of photons (light) in logic gates (NOT, AND, OR, NAND, NOR, XOR, XNOR). Switching is obtained using nonlinear optical effects when two or more signals are combined. Resonators are especially useful in photonic logic, since they allow a build-up of energy from constructive interference, thus enhancing optical nonlinear effects. Other approaches that have been investigated include photonic logic at a molecular level, using photoluminescent chemicals. In a demonstration, Witlicki et al. performed logical operations using molecules and SERS. The basic idea is to delay light (or any other signal) in order to perform useful computations. Of interest would be to solve NP-complete problems as those are difficult problems for the conventional computers. There are two basic properties of light that are actually used in this approach: The light can be delayed by passing it through an optical fiber of a certain length. The light can be split into multiple (sub)rays. This property is also essential because we can evaluate multiple solutions in the same time. When solving a problem with time-delays the following steps must be followed: The first step is to create a graph-like structure made from optical cables and splitters. Each graph has a start node and a destination node. The light enters through the start node and traverses the graph until it reaches the destination. It is delayed when passing through arcs and divided inside nodes. The light is marked when passing through an arc or through a node so that we can easily identify that fact at the destination node. At the destination node we will wait for a signal (fluctuation in the intensity of the signal) which arrives at a particular moment(s) in time. If there is no signal arriving at that moment, it means that we have no solution for our problem. Otherwise the problem has a solution. Fluctuations can be read with a photodetector and an oscilloscope. The first problem attacked in this way was the Hamiltonian path problem. The simplest one is the subset sum problem. An optical device solving an instance with four numbers {a1, a2, a3, a4}. The light will enter in Start node. It will be divided into two (sub)rays of smaller intensity. These two rays will arrive into the second node at moments a1 and 0. Each of them will be divided into two subrays which will arrive in the third node at moments 0, a1, a2 and a1 + a2. These represents the all subsets of the set {a1, a2}. We expect fluctuations in the intensity of the signal at no more than four different moments. In the destination node we expect fluctuations at no more than 16 different moments (which are all the subsets of the given). If we have a fluctuation in the target moment B, it means that we have a solution of the problem, otherwise there is no subset whose sum of elements equals B. For the practical implementation we cannot have zero-length cables, thus all cables are increased with a small (fixed for all) value k'. In this case the solution is expected at moment B+n×k.

For years I had the same question, thanks

If you measure the time it takes for the light from a torch to hit a sensor through a prism, does it change because of the prism or do the split color spectrums each reach the sensor at the speed of light constant?

What app can you use to measure distance with your camera?

Think of all the error involved in calculating the distance of deep space objects. Is the space all vacuum or the light rays pass through various mediums that alter its speed along billions of kilometers of distance that it travels. In the end, if it affects our measurements, how are we supposed to know if there was a delay or not? Also, is it observable with space telescopes and earth telescope because of the atmosphere? Very interesting topic.

Talk about over my head lol. But if you had a super fast strobing light shining through a very long piece of acrylic and recorded it with a high powered camera, would the light passing through the acrylic appear to reach the camera slower?

Yeah, 3Brown1Bkue did a great job 😎

I love this video. Thanks for rhess

Okay, but does visible light spectrum and for example radio waves part of spectrum travel though materials the same speed? If one were to slow down x-ray or radio in the acrylic would the delay be the same or would the higher energy make it pass through faster? 🤔

😮Wow! Awesome!

3b1b is one of my most favourite channels

Basically the interaction of the incident light and the matter wave takes some time to produce the resulting wave and the denser the material or the more fine-tuned the "shift" the slower the resulting wave propagates through the material. That is why it's possible to almost stop the light - it's like when a photon is traveling from withing the Sun's core to Earth. The core is so dense that there's so much interaction that the photon seems like it's slowed down until it reached the corona where it zips right through reaching Earth in 8m20sec. What makes the material clear or opaque is if the resulting wave still has the same direction as the incident light but clear materials can occupy the photon for as much time as the opaque materials do.

@CothranMike

Ай бұрын

The radiative pressure of the sun's photons forcing through the dense core (1.622 x 10 to the 5 kg/m3) and the surrounding currently created elements as well as those present in the initial molecular cloud does slow the straight pathway of a lot of the photons. This is what holds the rest of the gases in place as the density decreases. Eventually these photons WILL leave the sun and reach us, about 200,000 years after their creation.

Buen video. Instructivo.

The constant "C" is defined as "The speed of light in a vacuum". This speed is the constant. The context matters. Light, like every other wave, travels at different speeds in different mediums. This doesn't change the constant, just the context.

If the wavelength is shorter inside the cube, what color would a CCD detect if it was molded into the cube, or fixed in a way that removes any air between the CCD sensor and the cube, and then shine red light through the cube and into the CCD sensor?

Hi, do you have the link to the paper of Dr Hau and al? The link is not on their video

In some of the diagrams when showing that the speed of light slows down, it looks like the wavelength of the propagated field (original+electrons wiggle) changes, which would be a change in energy. Does the sum field, which moves slower, have a different wavelength and therefore is light of a different energy? If so, a follow up question. Light interacts with different materials differently based on its energy. Does this mean the product wavelength have different interaction probabilities? The three wavelengths exist in the block, the original, the electrons wiggle, and the sum of the two.

I heard from somewhere that due to relativity, any object moving at lightspeed from its own perspective will arrive at its destination instantanelously. Does that still apply once its put through a material to slow it down to outside observers?

Dispersion can be seen using a prisma. Does that mean, that red light and blue light (as the extremes) also have different velocities going through glas?

This melts my brain a little bit. The actual incident light wave is travelling at c and being affected by the electron's EM field which retards it so we only see it travelling slower, but it is also travelling at c? Not sure I get it. It is like shrodingers cat, alive and dead at the same time.

Cherenkov Radiation is a beautiful example of light moving slower through a material than other particles. Folk should check it out. Imagine an impossible haunting blue colour, that's Cherenkov Radiation.

does that mean we can stop, or slow down light infinitestimally but impinging infinite amount of light sheets/ fields over the first one and hence impeding the propagation? What if we propagate another light through the transparent block and let that sort of "drag" light 1 back, or even cancel out the light?

that edge of your acrylic vacuum chamber is very nicely polished *or broken, not cut ;)

Sound refracts the same way. My ultrasound machine needs to have the correct material velocity to measure the time of flight properly. My machine can find a defect the size of a grain of sand through 50 inches of steel. Did ultrasonic non destructive testing at a steel casting foundry in Berkeley California. We use lucite shoes coupled to the transducer to do shear wave inspection that looks for flaws at an angle where straight longitudinal waves can’t reach. Sound does not propagate through air as well as it does through water or other viscous coupling agent.

Sixty Symbols, Brady Haran's physics channel, also attempts to explain refractive index with two physics professors with their own but similar explanations (Phil Moriarty and Mike Merrifield). Another 60S video with Phil explains why some materials are transparent while others are not.

Sweet - the acrylic acts like a delay line or tardis for light waves!

I wonder if you can recreate the process using water with floats on the surface. You could see if the ripples on the surface causing the floats to oscillate cause the same kind of wave interference and delay the ripples reaching the other side of the pool. I'd also like to see how this relates to Lagrangians.

@TheActionLab I see it Kind of like a fast car creating wind behind itself, and the cars behind it will, end up catching that wind ultimately giving resistance to those car Except in this case as soon as the light hits the dense material, because it's so fast it creates waves which like air will proved resistance, and slow it down somewhat. Being dense, the material will react as one piece once the light hits the material, and that denseness will create a more dense wave. That dense wave is what slows down the light as it travels through the material With air, there is no resistance so it can go as fast as it needs to. Am I right or off?

So if I understand this video correctly, the denser the material the slower the speed of light in that material? It just still needs to be transparent for that type of light?

If this were any other youtube channel I would refuse to believe phones have sensors accurate enough to measure the speed of light. that is just wild

I've always thought of light moving "slower" through some medium is just the light "bouncing" around in said medium. While the full explanation may be more accurate, it's simply easier to wrap your head around it. If you jump into a pool of water, you now fall slower than you would in pure air. And you can still see all the way to the bottom as if it was air. But the denser medium simply makes you move slower because you are bumping into more stuff on the way. And that's what i think of when light "slows down" when hitting something.

@101Mant

Ай бұрын

You can think that. It isn't right though. The problem with analogy is we are the quantum scale and our intuition is all wrong. None of these things are objects as we understand them and the concept of a medium is meaningless.

@RealCadde

Ай бұрын

@@101Mant Yep and i did say that. But to wrap your head around the phenomenon in a practically usable way, it does help to look at it in simpler terms.

You might want to do an experiment with moving medium, to see what the effect would be... like light beam passing through flowing water with flow direction the same as/opposite to the beam

@DrDeuteron

2 ай бұрын

idk, a relativistic water fall sounds dangerous.

@GeoffryGifari

2 ай бұрын

@@DrDeuteron bbbut it would be COOL though