How to find Stress Patterns with Polarizing Filters

[@ScienceAsylum]

The first 1,000 people to use the link will get a 1 month free trial of Skillshare: skl.sh/thescienceasylum09221 *Correction:* The segment about safety hammers has been removed from this video. Some safety hammers do actually work very well. Thanks to diligent commenters, I've since done an experiment and released a correction video: kzbin.info/www/bejne/ZqXQfZuVmrijh7c *Clarification:* The side windows and _rear_ windshield are tempered. The _front_ windshield is annealed. Sorry for any confusion.

[@sadderwhiskeymann]

are you familiar with a strange experiment i saw a loooong time ago on a youtube video where - IF i remember correctly- the setup was two perpendicular polarized filters which of course resulted in black (no light passing) but then when adding a third filter in series, light magically appeared again!! I really hoped you would touch onto it cause i cannot remember the explanation! Thank you for the video anyway

[@pathwaytousername]

@@sadderwhiskeymann I don't think there is an explanation... just another mystery like quantum entanglement that everyone thinks should be impossible. Would still love to see a video if he hasn't already.

[@ScienceAsylum]

@@Server0750 The glass is cooled with a bunch of air nozzles. Each spot is where one of the nozzles was.

[@Luiz_Alberto.P.K]

Can I use this technique to see the stress pattern in a Prince Rupert's drop?

[@ScienceAsylum]

@@Luiz_Alberto.P.K Yes, you should see the rainbow pattern in a Prince Rupert's drop.

[@jursamaj]

4:25 That "chip" in the edge of the protractor is where the plastic was injected into the mold. That's why the stress is oriented to it. 4:35 That "crack" likely indicates that the plastic was injected near the hidden upper corner of the triangle, flowing around both sides. The "crack" is where the 2 flow fronts came together. Yes, I spent a few years in the injection molding industry.

[@ScienceAsylum]

🤔 Interesting! I'm not an engineer, so these kinds of things just don't occur to me. Thanks for sharing.

[@zeno2712]

@@ScienceAsylum Yes, as jursamaj points out, it's not a crack but a knit line. They are usually not a problem if the moulding tool and the moulding process are done well, but they can still be a line of weakness that may need to be considered in critical applications.

[@JohnDoeHZ]

Thanks for the injection molding tidbit. I would guess that quality control inspectors though (not engineers) use the polarization in production runs, if at all. Engineers would use it it for design. Although I've seen it used in research papers (scientists) on stress concentrations which might then be referenced by engineers for design.

[@miinyoo]

Injection molding of plastic is now so ubiquitous yet it still seems like materials sorcery when closely examined. Same feeling you get when you make your own nylon. Mind blown.

[@jursamaj]

@@JohnDoeHZ In my (admittedly limited) experience, polarimetry isn't very useful in production facilities, because most plastic parts aren't transparent. There is a lot of information we used based on such research, but I don't recall my plant even having any polarimetry equipment.

[@parallaxe5394]

Hello. Nick, I did not expect this topic here on the channel but as an engineer for material science I aprove! I would like to ad a short explanation how tempered glass is made and how it works, for people who would like to know/understand. Very hot glass (the car window!) is quickly cooled from the outside. When this happens the outer parts of the glass starts to quickly cool and when things cool they generally shrink a bit. No problem yet because most of the body of glass is still hot and can easily adapt to the shrinking outer layer. But soon the inner volume starts to cool down too and at that point the outer layer is stiff and can not easily change. But the inner parts need to shrink! (The atomic forces who hold the material together are very powerful and demanding) What happens is that the inner volume contracts but the outer layer can not move and this causes the outer layer to be compressed (more than it wants) and the inner volume to be pulled apart (because the outer layer does not move much). So why does this help against damage? Home experiment! Take a bunch of pillows and put them together on the table. Punch them and watch them fly through your room. NOw have another person take the pillows and press them together with both hands. Punch the pillows again and.. the pillows stay where they are. The compression forces in the outer layer function like the hands of the person holding the pillows. To "push the glass apart" you need to overcome these forces first which makes tempered glass much more resistant against damage. I hope this helps.

[@ScienceAsylum]

Thanks for the extra detail! (Also, I want other people to love polarizers as much as I do, so the glass thing helps make polarizers relevant to people's lives.)

[@DANGJOS]

Fascinating, and makes so much sense, thanks! I always wondered why the stress makes it stronger and resistant to breaking.

[@localverse]

Nice explanation! 👍 Would it have been better to call it 'pressured glass'?

[@olmostgudinaf8100]

@@localverse Or "pre-stressed glass".

[@jasonremy1627]

Well explained!

[@KyleJMitchell]

"Light is literally all we can see" is so simple a statement that it sounds silly. But since I've been going through your videos on cosmology I've gotten a handle on dark matter and understand that light doesn't interact with everything. It's... uncomfortable knowing that some ideas that we take for granted (like light being the mechanism through which we observe ALL things) hide ridiculous facts about how the universe really works.

[@bryandraughn9830]

Technically, the only thing we can ever see is the electrochemical patterns moving around in the visual cortex. It's so strange to Conceive that we don't see "out", but everything we see, all of our surroundings, even the sky, is built within the mind based on sensory input. When you see something "over there", the distance between you and that object is probably real, but it's perceived within the confines of your skull. Even the position of yourself, your body, and it's location relative to the environment, is a projection of what may or may not exist "out there". It really messes with the mind! Lol!

[@MNbenMN]

@@bryandraughn9830 Kinda like we are just bundles of neurons driving bone mechs powered by meat motors with a skin casing.

[@Silverxlx]

I mean is touch not also observation

[@thirdeye4654]

@@bryandraughn9830 Very true and to make that more obvious, make sure to understand that there is no brown or magenta in the color spectrum (let's call it a rainbow). Colors (by that I mean the sensation we call colors) are made up by our mind. Not to mention that you perceive different colors depending on the words you have in your language.

[@valpsrn9235]

We can easily extend this to "almost everything we can see is electromagnetic fenomena". We only know about gravity (apart from touch, of course) because the fotons expose the objects positions in the space due reflexion or absorption (hence the acceleration too). Moreover, Touch is also an electromagnetic phenomenon, LoL

[@MaverickBlue42]

The sharp point tools actually work quite well, your problem is your glass isn't secured, and just flexes and bounces away. In a car, the glass is secured by the doorframe, with extra pressure from the water pushing in. There's lots of youtube videos of people testing tools, most of them work just fine, with the best having a spring-loaded punch similar to one you'd use to mark metal prior to drilling.

[@stephenviggiano1610]

^agree to this with a ton of experience behind it. As a firefighter, taking tempered glass is done often on vehicles. A lot of tools that folks expect to readily break glass doesn’t often work but the easiest victor against tempered glass is always a small, focused point.

[@ItsEverythingElse]

Was going to say the same thing.

[@HeriEystberg]

I'm surprised that he didn't figure that out himself.

[@thepenguin9]

Pointy end of hammer, not the blunt end 👌

[@AnagramGinger]

It reminded me of an episode of Shark Tank where someone first wanted to show how easy it was to break through a door, but humorously failed to to so because the door was secured to a movable metal frame instead of an actual wall.

[@adupthetotal782]

I recently finished a first year module in Material Science and we literally did this exact experiment! Your videos were a huge inspiration for me to study an undergraduate course in Physics. Thank you so much!

[@RobbieHatley]

Amazing! I happened to have a pair of sunglasses hanging off my shirt, and a clear plastic rule under my monitor, so I put the sunglasses on my face and held the ruler up to the screen, and voila, rainbow colors and stress patterns! I especially like how the colors are the most intense when the sunglasses are rotated 90° so that the light from the screen goes black except where it's shining through the ruler, which reorients the light so that it can be seen. I've been alive 63 years and I'm reasonably science savvy, and yet this is the first time I've heard-of or seen this effect! Thanks for bringing this to my attention! Subscribed, liked, and playlisted x5.

[@angeldelvax7219]

Took me quite a few years to find out not everyone can see stress-patterns without any tools. Turns out only a very small percentage of people can actually see them. Needless to say, I got even more interested in them! Opticians use polarizes all the time to check if the lenses in your glasses are mounted properly!

[@mlok4216]

Wait, you mean, your eyes act like a polarizer? You can see them naturally?

[@localverse]

Are there any artists that paint with that in mind, so people would need polarizers to properly see all of the painting, while a very small percentage of people would see that naturally?

[@anullhandle]

@@mlok4216 some people can to a limited degree, not like an octopus though.

[@davidward5968]

@@localverse I don't know if there are, but what a great niche for someone.

[@MattMcIrvin]

I trained myself to see Haidinger's brush, which is a visible manifestation of linearly polarized light that you can see without a polarizer. It looks like a very faint yellow and blue bow-tie pattern near the center of your field of vision--you can see it by looking at a white LCD screen and gradually tilting your head, so the pattern changes enough that your brain won't edit it out. The blue parts lie along the axis of the electric field, and the yellow parts along the axis of the magnetic field. Once you know what to look for, you can see it in the sky, because that light is somewhat linearly polarized.

[@damienhunt4264]

"Light is all we can see." This is quite beautiful.

[@saumitrachakravarty]

Sandwiching something in between two polarizers is an useful tool to pathologists since it allows them to differentiate between different types of microscopic materials based on their molecular isotropy (or anisotropy). Like, it is used all the time in microscopic tissue sections to detect amyloid, a class of misfolded protein that causes amyloidosis. Also there are uses of polarizing microscopy in geology to tell apart different rocks. You could do an episode on such practical uses of polarized light microscopy. It could be interesting, at least to me.

[@Stars4Hearts]

Science fact of the day

[@dandurkin9735]

Wonderful video! When I was a TA, the demos I did with polarized light were the most popular (and most beautiful). Thank you!

[@jonathanb6371]

I love how Nick keeps the bloopers! 😄😄 Pure genius!

[@markotrieste]

Next, do a video with three polarizers. Whenever I see more light coming out when adding a filter, I really "feel" quantum mechanics.

[@mirador698]

Wanted to make the same comment. Hope he sees this.

[@joehubler4965]

@@mirador698 me too

[@gert-janbonnema]

I wanted to place this comment.

[@greamespens1460]

The 3D animation used ramps up your production, great work .

[@ScienceAsylum]

Thanks! 🙂

[@snowthemegaabsol6819]

Unknown to most of us, humans actually do have some capacity to tell polarized light apart from unpolarized. A blank sheet of paper will simply be white, uniformly and equally, no surprise there. But on a standard LCD or OLED monitor showing a blank white canvas, by really focusing and also tilting your head every so often, you can see a blob of yellow and blue in the shape of a bowtie. It's slightly different from person to person, some people see patches where the screen is slightly darker but don't see the colors, some people do see the colors with no change in brightness, and sometimes the effect can randomly disappear.

[@whatitmeans]

nick has already a video on it... you could find it here on YT

[@rya1701]

It's called haidinger's brush

[@JohnDoeHZ]

I'm pretty sure you struggled to crack the tempered glass because you allowed it to move, preventing the kinetic energy from turning into pressure (stress). When you hit the corner, the glass was pinned to the floor at the contact point, it couldn't move, so all the kinetic energy was turned into pressure energy, exceeding the internal allowable at that point.

[@logiticalresponse9574]

you are partially correct . due to how tempered glass is made the edges of the glass cool down faster than the rest of the piece making it ........ less tempered . hitting tempered glass edge on can break it just as easy as annealed glass .

[@57thorns]

@@logiticalresponse9574 I believe prince Rrupert's drop is en extreme example of this.

[@logiticalresponse9574]

@@57thorns indubitably

[@SytRReD]

Giant ball of stress 😂 Thanks for all your hard work, I've been an avid viewer of your videos for already quite many years, and I love everything you do!

[@ScienceAsylum]

Thanks for watching 🤓

[@DavionStar]

Always love your vids. You always tend to explain things in a way I can always understand which is sometimes difficult to find. And sitting down for a little science lesson kinda reminds me of the old days with Mr. Wizard when I was little. Keep up the great work!

[@wernerviehhauser94]

One of the first things I bought when I started as a ohysics teacher - linear and circular polarizers as well as cmy and rgb filters. Theater supply usually has those as foils for reasonable prices.

[@owlredshift]

Okay honey, well I don't know about any of that but this the Mac Donnels. We got a line formin ??

[@Nikhillbt]

I just love it when you say "It's okay to be a little crazy".

[@antonl21]

Thanks for letting me know how to experiment with this phenomenon using just my sunglasses and a pc monitor! On the other hand, my wife does not appreciate it greatly because I am searching through the kitchen for every transparent bowl and gathering them on my desk for inspection.

[@ScienceAsylum]

😂

[@rudolfquetting2070]

Sometimes, Your video are difficult to understand (due to the complexity of the subjekt). Sometimes, Your videos are relatively simple (but even teach me some new aspects like this one). Sometimes, I allready know the physics You are talking about (It had been part pf my business) Sometimes, it’s all completely new for me. (Due to my limited knowledge.) But, it ALLWAYS is a very incredible fun to watch Your videos.

[@laci272]

I already tried it before the video's end. Amazing experiment. My daughter loved it and so did I.

[@DANGJOS]

@Science Asylum I've noticed that the pattern or order of colors in the polarizing materials is the same as in thin film interference. That makes sense because the change in phase of the different wavelengths of light differs the same over distance for the rotating field vector as in the transverse sinusoidal oscillation does over distance inside of a thin substance (like a soap bubble). I've graphed those colors using simple wave theory in kaleidagraph and with a little color theory knowledge, my predicted colors seemed to match well with the observed colors. You can take that as a hint at a suggestion for a future video, if you want 😉

[@beardlyinteresting]

You know it's funny, I knew about all the individual bits of information that made up this video; LCD screens have polarised light, Clear materials can show their stress patterns when placed between two polarisers. But I never though to use my screen as a polarised light source and to look at stuff through my sunglasses to get this effect. I'm very annoyed that I never even made the connection because I've always wanted to check out the stress patterns of stuff. So thanks for the awesome video, I'm now running around my house getting every clear glass/plastic thing I can find and holding them up to my monitor.

[@apostolakisl]

Tip. If you break a spark plug and collect the broken ceramic pieces that result, simply toss them at a tempered window, the window shatters with hardly any impact at all. Something about the harmonics I suppose. But just a little shard of that broken ceramic casually tossed at the window and it shatters. Might be worth looking into and doing a video to confirm exactly how that works.

[@ScienceAsylum]

Interesting 🤔. I'll have to look into that.

[@stuehleruecker]

Hmm, i think Adam and Jamie had it. But its difficult find on so many videos.

[@gadget6623]

The Slow Mo Guys did a video on crack propagation in tempered glass. They went to 800,000 frame per second to get it. That's nearly 2 days playback at normal speed for 5 seconds of filming. It's insanely fast how the cracks move through the glass as the pressures relieve.

[@ScienceAsylum]

It's so fast! My camera is only doing about 1000 fps, so nowhere near what Gav and Dan can do.

[@prathmeshsutar5829]

Nick this video fascinated me so much, u are doing a great job, I kept searching for things to check them out under these polarized glasses hope to see such surprises in upcoming videos too

[@unclao]

Your videos put more "light" in our world! 🤩

[@FirstLast-vr7es]

We've used this technique to find defects in door glass for residential ovens where I work. That tempered glass has to be perfect, or it can shatter during cooking cycles. Don't want that to happen in somebody's kitchen.. There are some REALLY cool stress patterns in that glass, too. You'd never know without using a polarized filter like this.

[@kerryhaycock9446]

I think the graphic at 2:13 depicts a Laser , not just common polarisation , as the waves are also all in phase …. Also I can vouch that the hard tipped glass breakers do work . I noticed your example of glass was not rigidly constrained around its perimeter and was able to bend under the blows . In a car or window frame the glass is unable to bend as freely especially closer to the frame , and the tool is able to work as intended.

[@robg7892]

i really like your videos! I was going to do a linkedin post about this over the pandemic, but never got around to it. Couple of notes: "stress rings" are usually called fringes, like when looking at the moire effect and probably more technically correct to call strain rings since it's really the spacing of the molecules that alters the polarization of the light. You can actually buy off the shelf polarizers and materials that are basically calibrated to measure stress (you put the clear stuff over a thing and let it stretch) and a color coded chart is provided to quantify the stress of each color. Something not touched on your video, which I'm probably just telling you something you already know, but if you rotate your polarizer you can determine the directions of the stress in the material also. Birefringence is cool!!!!!!!!!!!! lol, nice job, you're doing awesome stuff.

[@mariotabali2603]

Good stuff

[@dcsignal5241]

I recognise those patterns in the Plastic equipment (protractor, rulers etc.) we had in High School. I wonder if there was a enough Polarisation going on in my glasses to account for this. Nice to finally have an explanation for what it was.

[@h7opolo]

this vid shall be a wonderful addition to my "birefringe" playlist.

[@itsawonderfullife4802]

Thank you for the video. Also great book by the way. Compact, to the point and comprehensive. A great refresher and review of all fundamental physicist. For those interested, polarization is the manifestation of spin for photons (quanta of a mass-less vector quantum field). It is the same quantum phenomena but with different names and histories of discovery for electrons and photons.

[@VagifZeynalov]

Thanks! I still didn’t understand how more filters could produce more light? Because the first one is obviously already filtered out most light with other polarizations….

[@luckybarrel7829]

Very interesting. I wish everyday stuff like this was more common knowledge. You're definitely making that happen!

[@ZiggityZeke]

I was actually wondering about these since Ive seen these in my car with my polarized sunglasses. Thanks!

[@yunthi]

tempering glass is based on heat dilation (as opposed to metal where its about the crystalline structure grain size, glass doesnt have a crystalline structure), its heated up to a point where its sortof soft, and then cooled quickly. when its heated the glass dilates. when its cooled from surface first, the surface shrinks and hardens. after that the insides start to shrink too, but as they do, it drags the surface with it creating pressure and resulting in a denser surface. the cooling is done via pressurized air, and each of those dots is where an air nozzle is blowing on the glass.

[@ZiggityZeke]

@@yunthi wow, very interesting, thank you for the comment

[@gabewrsewell]

to those curious, you can see polarized light yourself! physics girl has a video on haidinger’s brush, and its orientation in your vision is dependant on the polarization of light coming in. i’ve trained my ability to see the pattern enough that i can easily spot it in the clear blue sky 90° away from the sun, with the yellow lobes in the pattern pointing to where the sun is. you can also see it while looking through polarized sunglasses or an LCD screen as mentioned in the video here.

[@diegocabrales]

This video clearly says light polarization can be seen given some conditions and gives examples where these conditions holds.

[@localverse]

First off, great topic, and as usual you revealed a tidbit that helped upgrade my knowledge to a new level. Particularly about how a material can rotate the light. Also got questions related to that: 3:25 Where the plastic rotates the light: 1) what in atoms is rotating the light? 2) if plastic can rotate the light, and the effect between two polarizers will depend on wavelength, then why do so many video demos of polarizers act like it's such a mysterious quantum effect for a 3rd polarizer to change the amount of light coming through two polarizers?

[@eroraf8637]

The rotation of polarized light is caused by birefringence, where a material’s refractive index depends on the polarization and propagation direction of light. In other words, it’s “harder” for the electric field to propagate along one axis than another. There’s nothing mysterious about the three-polarizer experiment if you think about it in terms of vector components and vector projection.

[@Niko-rf9or]

The main reason car windows are tempered are for crash safety, but basically for the same reason you mentioned; no big sharp pieces being thrown at you. Car crashes are a lot more common than cars being fully submerged.

[@ScienceAsylum]

Fair point.

[@dearcath]

Always a fan of your videos, Nick!

[@N0Xa880iUL]

One person in your 2017 video about polarized glasses had commented about this.

[@ScienceAsylum]

Yep. Finally got around to making the video.

[@ishakawade9100]

your videos always amaze me, though i don't completely understand them as i am a student still learning those big terms but they are..umm.. precisely great

[@Ckamerad]

Firefighter/rescue worker here. The glass would have broken if it had been secured in place. This glass is amazing at distributing impact force. The strikes you made deformed the glass as it is made to do. It’s an excellent example of how well we have learned to manufacture safe materials. That said the tools you used were made to strike this glass when it has a very limited area that the material can use to deform and flex. I can’t speak to the usability or performance of anything of the tools you had tested. Something with a small enough impact point works great on vehicle windows so long as you give it plenty of force. I’ve used a spring loaded windshield breaker for years. It takes much less force than swinging any kind of hammer tool. It shatters the window without endangering the occupants and causes almost no material to be ejected into the vehicle. The impact point is extremely small and it takes little force in comparison to a hammer. I absolutely love your channel. I hope my explanation doesn’t seem rude. I am definitely not an expert in physics. Would love if you could make another video giving reference to how the size of an impactor can make a huge difference in effect. I’d use that for training. Thank you for the wonderful work you do sir.

[@ScienceAsylum]

It's not rude at all. Thanks for the correction.

[@ankokuraven]

playing with polarizers for the first time in physics class was cool. if i recall, a really cool object to look at under this effect is a prince ruperts drop.

[@Manabender]

This *really* makes me want to see the Slo Mo Guys revisit the Breaking Glass video with polarizing filters. I wanna see those colors change *as* the glass breaks.

[@ScienceAsylum]

My camera isn't high-speed enough for that, but the Slow Mo guys could definitely pull it off. I'd love to see it.

[@mandelabrein8116]

@@ScienceAsylum I bet Destin with smarter every day would be willing to collaborate with you, yall both a couple weirdos

[@kindlin]

@@mandelabrein8116 Their energies would vibe perfectly.

[@blackholedividedbyzero]

From wanna be immortal to a giant ball of stress.

[@ScienceAsylum]

I'm a diverse individual.

[@blackholedividedbyzero]

@@ScienceAsylum thanks for the reply😊😊

[@troger147]

Someone on s/askphysics asked how KZbinrs like Veratasium and kurzgesagt were as far as videos go. Turns out Fermi labs, pbs spacetime, and you were in many of the responders top 3. I totally agree!!!

[@ScienceAsylum]

Thanks for letting me know!

[@troger147]

Not that any of them were bad rather being more convoluted for the sake of being convoluted. I'm sure most of us appreciate the clarity you and couple others bring. Easier to follow and understand which means easier to learn. Make like a fraction and simplify it lol.

[@troger147]

And you're welcome =)

[@Bassotronics]

I remember when I found on the street a broken game toy and I was able to take the screen apart. It had two transparent plastic pieces and I was astonished when I turned the two plastic pieces and it became completely black! 😯

[@trollme.trollmehard.9524]

Back when these filters weren't glued in, I'd take my watch/calculator apart and flip the polarizers, which created white-on-black displays.

[@anthonygiaconia7880]

I've always wondered what those circles in automotive glass represented. Thanks for answering it.

[@ScienceAsylum]

You're very welcome 🤓

[@kindlin]

@@ScienceAsylum I actually just noticed these in my car the other day, and was curious, but not enough to go and look it up. Now, I know!

[@benjaminsmith4058]

Because of Brewster's angle acting as a second polarizer, you can see photoelasticity by simply looking at the reflection of LCD light off of plastics like polystyrene - no second polarizer needed.

[@Dark_Jaguar]

I appreciate that this video was designed with cell phone orientation in mind. I happen to hold my phone on it's side.

[@sorushflummi411]

To get a pretty fascinating Effect One needs a Pair Polarisation Glasses with round Glasses. Plop One Out, turn it a few Degrees - I have One at Horizontal and One 45° turned to the Left and plop it Back and One gets a 3D Effect in Reality or even more!! I know not really, but pretty fascinating and revealing! Works best during the Day :)

[@logiticalresponse9574]

due to how tempered glass is made the edges cool down faster than the rest of the piece . hitting the glass edge on will break it just as easy as annealed glass . there is also an in between temp and plate (annealed) called heat strengthed that breaks similar to temp but in bigger pieces in a less chaotic fasion

[@paulvansteenberghe4644]

I worked for about 6 years with Alvin and Mortimer Marks, the inventors of polarizing films. Amazing the things that can be done with polarizing light, including making old time 2D movies into 3D movies, polarizing photovoltaics ( LUMELOID), stealth materials ( absorbing UV visible and IR light).

[@basti4655]

I always wondered what these points are on the rear window when i look in the rear view mirror with my polarised glasses on, thanks nick.

[@ScienceAsylum]

Glad I could help 🤓

[@marcelosantana9311]

Not sure if someone mentioned but windshields are made of laminated glass (1 piece of plastic sandwiched between 2 thin pieces of glass). This is important because of several factors, for example, if a rock or large object hit your windshield it won’t got through. Second the crack are lines so you can still see and drive. The temperate glass are used on side windows, that is why on smash and grab you will find a thousand piece of glass. On a car accident it allows the windows to be broken so you can be removed and also prevent sharp glass from hitting you.

[@DigitalArchmage]

Better tool for breaking glass is a "spring loaded center punch". The PSI is much higher in the tiny point, and the window shatters easily. They're cheap, small, and you don't have to swing anything (you just press it into the window until it clicks). I keep one in my car - less for finding myself in a lake and more for if I need to get someone out of their car in an emergency. Another interesting method (but not practical for emergencies) is throwing a piece of broken spark plug at the glass. The ceramic does some interesting science - there are youtubes showing throwing rocks vs throwing spark plug chunks, and the difference is amazing.

[@ScienceAsylum]

Good to know 👍

[@cyrilio]

Did you know you can see UV light if your cornea is removed? See for example the painter Monet and how his paintings turned more blue after the removal of his lens in one eye. Monet's surgery meant the entire lens of his left eye had to be removed, leaving him with what's called aphakia, or the absence of an eye lens.

[@jesperpersson465]

The sky can become kinda funky with polarized sunglasses too. I have noticed that if I look away from the sun ( north at noon in the northern hemisphere ) I can make the blue of the sky darken by rotating my glasses. The effect doesn't affect the look of the clouds so they pop out. Sometimes the effect doesn't happen and I have no clue why. Not even sure why the side of the sky away from the sun seems to have some polarizing effect.

[@zefellowbud5970]

Thats apparently how birds tell directions from what i read in an article a while back The polarized sky tells them where is north.

[@microwave221]

Tempered glass also keeps you from getting blended by broken windows in a car wreck, or even just after hitting bigger bumps in the road. As far as those crash hammers go, the cheap ones are too soft to work because they deform slightly on impact, and shouldn't be allowed on the market considering the implications. Better ones will have hardened steel or carbide tips to focus the impulse into a smaller spot, and spring loaded center punches are very popular in emergency services for their ability to break auto glass in a controlled way

[@ScienceAsylum]

I don't understand this cheap "window breakers" are even legal. I'm going to look for a standard hammer design but with a pointy tip. Best of both worlds.

[@BartdeBoisblanc]

Great video on glass and polarized light. I notice one thing you didn't mention but touch on tangentially. The amount of rotation is dependent on the frequency of light. Circular polarizers take into account the frequency of light. Most Sun glasses are linear polarizers.

[@henriquecorreia9670]

Amazing nick ❤️

[@h7opolo]

7:35 the glass shards won't just be smaller, they'll be less sharp, too.

[@Unprotected1232]

On a side note car windshields are also laminated. When the tempered glass shatters it will stick to a stretchy substance and act like a net. Kinda like how softer steel is used to reinforce hard and brittle concrete.

[@DaellusKnights]

Prince Rupert drops are probably the best tool for looking at stress patterns in glass. The tension curve on the inside is so extreme that it makes the most vivid examples in polarized light. 😁

[@ScienceAsylum]

I'll have to try that out.

[@mrt1917]

This man is genius 👍

[@dennislindqvist5461]

The glass will only break if there’s a difference in preasure. But as shown in Myth Busters, a car that goes under water is actually flooded and you can’t open the doors or lower the windows because of the outside pressure jamming them shut. However the pressure won’t be enough to shatter the glass. The security feature is more about car collisions where you won’t suffer the death of a thousand cuts.

[@SeanBZA]

Finally a way to use that quack high power polarised light source I got a while ago. Bioptron I bought that was faulty, but which was a very easy ( actually free, using scrap parts) fix for me to do. Had no real use for a 50W polarised light source till now, just have to find some polarised film to use it.

[@VicMikesvideodiary]

I love this guy.

[@mericet39]

I love your t-shirt! Relevant AND Enterprise D - the best Enterprise!

[@ScienceAsylum]

Next Gen shirts are so hard to find!

[@borg972]

@@ScienceAsylum True 😿Can you tell us where this one is from? 🖖😺

[@ScienceAsylum]

@@borg972 I think I bought it at Target, but I'm not sure. 🖖

[@85set05]

Oh Wow, I cant wait to figure out what those are I've been seeing them since getting my new sunglasses.

[@prich0382]

Try having a monitor screen all white while in a dark room, have a pair of polarising lenses so you can see either the screen lit up or go dark, turn the lenses so it's dark, then grab a full clear water bottle and look at it through the lense. It looks amazing, looks like it's completely self luminescent, it'll look lot up and maybe you'll see other colours too

[@Hansengineering]

I got some Oakley "fishing" glasses a few years ago. I don't fish, but the mirrored reflection was a and that's what I wanted :V Anyway, they have STRONG polarization and when pairing them with a motorcycle helmet it makes a cool but sometimes disorienting effect and ofc it's related to polarization! First off, cars change color with their angle to you. They're dark when coming at you, but shift to a lighter color as they approach 90° to your vision centerline. WATER is super trippy, and can appear doubled at some angles. I got prescription lenses so I hardly wear those glasses any more but I was walking my dog by a pond and noticed "holy crap! I can see all the fish!". Product functions as intended.

[@Martinko_Pcik]

Cool! I just tried the glasses from the 3D movie theater and a cell phone as the source of polarized light and I can see stress in the plastics as well.

[@whatitmeans]

Hi Nick!... I would like you to extend this video with this: if you pick your 2 squared polarized filter and place them perpendicular, as you shown, light is blocked.... but if you place in between another polarizer at 45°, suddenly light will start to pass, which is a complete nonsense from the classical Maxwell's description of light!!... but it happen in reallity!... minutephysics has a video on it, but I would be nice to see your point of view and apply to it other experiments: it will still happen if the polarizers are wet and stitch together through surface tension of water? (water in between polarizers will reduce any effect of evanescent waves, allowing "tunneling" of photons)... Hope you give it a try. PS: tempered glass is used in case you crash without the safety belt on, and you get thrown through the glass due inerce... if it is a tempered windshield you will fly through without been torn apart due the remaining glass spikes it would being there, after a crash if the windshield were not tempered glass.

[@zefnoly9147]

You can use this polarization to see how dusty your monitor is as well... As the dust will slightly rotate the polarized light as it bounces off the dust and let you see the dust clearly... Along with other stuff that may be on your monitor...

[@rayoflight62]

Thank you for the video, great job...

[@diegofernandez4789]

A different kind of video this time. Love it anyway.

[@ScienceAsylum]

I don't want my channel to exist in too small of a (metaphorical) box.

[@argon1611]

I was able to see these colours since I was a kid - without polarising glasses .. I assumed everybody could. I've also been able to see colour tones vividly where others were saying it's the same colour .. found out I'm a male with tetra-chromatic vision .. .. like a unicorn - discarded by society for being different .. .. I've learned to keep such things to myself and pretend I'm just ordinary Joe and use my not-so-super-powers to excel in life .. only to find that it pisses off people .. words like "who do you think you are?!" - echo in my not-so-identical memory .. .. oh well .. this is my life and it's beautiful.

[@tinglin6121]

Hello Nick, I am new to your channel and find your detailed explanations extremely helpful! Would you mind doing an episode explaining why solids have color? I think there are a few different absorption mechanisms out there, like F-centre or van der Waals. A video about them would be amazing. Thanks in advance!

[@melchiortod29]

The magic of dielectric tensors

[@GwonkReefkeeping]

Loved this video.👍🏾👍🏾👍🏾

[@rafaelshumaker1883]

I've heard that striking tempered glass with the ceramic of a broken spark plug can cause the glass to shatter easily. But I have not tried to verify that.

[@douglasboyle6544]

The critical thing about breaking the tempered glass with the special pointed hammer is keeping the pane rigid, as if it were in a car door, yours flexed and dissipated a lot of the energy required at the point of the hammer. But otherwise, you're right, even a moderate bang on the edge will shatter tempered glass.

[@MattMcIrvin]

When I was a graduate student I lived in a literal hole in the ground--a studio apartment in my landlord's basement, with a sliding glass door in a small well below ground level. The door was double-glazed with tempered glass. One wintry evening, I was away from home when the temperature suddenly dropped from around freezing to down near zero Fahrenheit. When I came home, I found that the outer pane of the glass door had completely shattered into those tiny gravel-sized pieces. Thermal contraction had apparently caused those internal stresses to let loose and break the glass. Fortunately, the inner pane was still intact--but most of the shattered outer pane was still holding together loosely like a sagging vertical jigsaw puzzle that was obstructing the door from opening, so I had to knock it all away to open the door. Since the remaining pane was a less effective insulator, I had a chilly couple of nights until the landlord could get the door fixed.

[@ScienceAsylum]

Dang! I just Googled it and, apparently, it's not uncommon for doorwall glass to do that. Seems like maybe they shouldn't be using tempered glass in doorwalls.

[@ultimasdragon7840]

Awesome video, I kinda always wondered about the spots, although I'm wondering if they might be from the molds themselves, seeing how auto glass is made, the molds are not what you'd think. They basically are a "Table" for lack of a better word, made of a grid of rollers that can be adjusted up or down to set the curve of the glass. And I'm thinking since the spots basically line up with the grid of the rollers if the glass cools faster at the contact points creating those stresses the polarization allows us to see. If that makes sense. Also As someone currently working in the auto glass industry as a tech, and for some time now, a few corrections: (to the best of my knowledge and understanding) A: On a lot of newer vehicles the front door glass is now laminated annealed glass, like the windshield. Meaning it's not going to break into a thousand tiny pieces, it will hold very strong even if broken and take a lot of effort to make fully fail. However the rear door glass, or backglass should be tempered. The way to tell is to look at the glass, there should (by law) be markings on EVERY piece of glass that states laminated or tempered along with other info like brand etc. B: Tempered glass is very unlikely to shatter from the force of impact going into a body of water, unless it hits head on, you should 100% have a glass breaking hammer similar to what he showed in your vehicle..period. You should also have a seatbelt cutter as well. C: As to the point above, the reason the hammer failed in your test is because it was not secured on the sides allowing it to dissipate the energy. These hammers are intended to break tempered auto glass in an emergency to gain access in, or out of the vehicle, that glass will be secured on all sides and will break. He is 100% correct that the edge of any glass is the weakest point. D: Not so much a correction but if you find yourself a body of water and sinking, the very 1st thing to do is roll down the window, power windows are not likely to immediately fail as there is water proofing, the inside of your door takes on moister normally. E: Purely a nit pick, there is only ONE windshield in a vehicle (unless it's a split windshield) everything else is a front door glass, rear door glass, Back glass, vent glass (opens as part of the door but does not roll up or down) quarter glass ( stationary glass that does not roll up or down, and does not open with a door.)

[@randomisedrandomness]

I tested it with polarising glasses from a 3d cinema and wow it's so cool.

[@TheFLOMAN76]

Love it! Thanks! 😊

[@DaedalusYoung]

When I first got a polariser filter for my camera I did this. Just pointed it at my computer screen and took pictures of various transparent plastic objects, such as bubble wrap. Just because it looked cool, nothing scientific about it. Also, there's a glass museum in my town, they have some polarisation experiments in their collection. Always fun to play around with.

[@ScienceAsylum]

Sounds like a fun museum!

[@harold2718]

Haidinger's brush is crazy, it's something you can pretty much always see when you're staring at a computer screen, but unless someone tells you it exists, you probably never notice.

[@glimm3r]

Me gettting between my monitor and the sunglasses to check my stress points: As I predicted, I resemble a polka dot!

[@Tore_Lund]

A few cars do have tempered windshields, with spots and rainbow coloring all over, that is vey noticeable from the outside at least on certain days.

[@gregg4]

I don't know which hammers you are talking about at around 07:00 but the small red hammers designed for emergencies definitely do work to break tempered glass quickly. If I had a car, I would have one of those near at hand.

[@ScienceAsylum]

I'm hearing this a lot in the comments. I must have a cheap useless hammers. Will be trying alternatives soon 👍

[@cjg8763]

I remember my dad having polarized glasses when I was a kid and we'd use them to watch fish swimming around below the surface of the water in front of the fish ladder we lived near.

[@h7opolo]

awesome selfie hack 4:07

[@veldrintheshadow]

I also self-identify as a "giant ball of stress". That cracked me up.

[@RichardJohnson_dydx]

The clear ruler and triangle was a great example of internal stresses. I am taking a strength of materials course at my university right now. It was difficult to understand internal stresses and the concept did not make sense to me.