Glass is Solid… So Why Is It Clear?

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Glass is made of sand, which is a kind of rock. But glass is transparent, and rocks aren’t transparent. What’s up with that? Why is glass clear? And why can I sit on a chair? And why can we touch anything? Today we zoom down to the weird world of electron clouds and quantum touching to find the answers.
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[@besmart]

Is this one of those questions you've always wondered about but never knew the answer to? Me too. This is a re-upload, there was an error in a graphic in old version and YOU DESERVE 100% ACCURACY, FRIENDS

[@nihilsinedeo9472]

yes

[@garretthallmark6648]

This is a question that I never knew I wanted to know the answer to haha

[@Dudukina]

Thank you! YES

[@LiraNuna]

I'm watching it again and commenting so the algorithm sees the engagement, Re-uploading hurts creator metrics so I hope I can do my part.

[@jordanlaquey5325]

you're welcome

[@yeetghostrat]

My initial thought "well that's obvious, it's becau... Wait why is transparency a thing?"

[@kritika6734]

Same here I was like "that's simple, because light just passes through it and no reflection means no visibility" and then I watched the video and I was like :O

[@NeonGreenT]

Imagine a Ship on the sea, If small waves hit it, it just absorbs them, If a wave with The same size as the ship hits it, it might break. But If the waves are way bigger than the ship, the wave passes under the ship without really getting weaker. Thats an analogy for transparency, where as the wavelengths of the visible light spectrum are Just too big to tingle the glass molecules and therefore pass through it.

[@NeonGreenT]

@Mr. Virtual be precise in your terrible terrible criticism

[@blossomalabi5428]

@Mr. Virtual had us in the first half

[@gualo21]

He doesn't really explain why, or rather why other things aren't. What's different between the crystal structure of salt and the structure of glass.

[@nerobernardino88]

And I was today years old when I learned that glass is opaque to UV Light.

[@gordzhao]

Normal glass blocks UVB but not UVA.

[@smapa1185]

Ever seen a slight shadow through prescription glasses?

[@Enourmousletters]

@@smapa1185 That's definitely not from UV.

[@DANGJOS]

@@smapa1185 Glass normally makes slight shadows because of reflection.

[@hulagu3068]

Not true you can get sunburned through glass

[@aparks1437]

"have i made myself clear?" "clear as glass. in fact, i can see right through you"

[@radha1172]

*If Joe was my science teacher, I'm 100 % sure I wouldn't have dropped science.* This is sooo cool!

[@theDCification]

I feel like this video explains really well why matter in general can be transparent, and not at all why glass meets those conditions.

[@alex.mojaki]

Yes, they said it's about the atoms (not the molecular structure) but also sand and glass have the same atoms.

[@andrewburnett8743]

Comment of the year

[@srenjensen7208]

its mostly to do with its amorphous state. no crystal structures inside the glass to refract the light. i think.. here ya go kzbin.info/www/bejne/jKi1fXyqa8-amq8

[@minisn3066]

What do you mean exactly? He explained that the energy levels (of the electrons within the atoms that composes glass) are too far apart for visible light to provide sufficient energy to “bump” electrons to the next level. Therefore, glass is transparent in visible light, and because our eyes detect visible light, glass looks transparent to us.

[@theDCification]

@@minisn3066 which is a great explanation for how “matter in general” can be transparent. But there’s not an explanation for why the energy levels in amorphous glass are further apart than crystalline sand. They’re made of the same atoms, the jumps seem like they should be the same.

[@indominus6091]

This video is intresting just like all the others

[@yetinother]

And that's more than ok!

[@Aphrodite10]

Yeah, your comment is as good as others

[@indominus6091]

@@Aphrodite10 wow thats a good burn if you meant it that way im taking that

[@Aphrodite10]

@@indominus6091 what you meant

[@indominus6091]

@@Aphrodite10 i meant the video is intresting and we can learn from it

[@Darkanight]

I love how you genuinely love understanding the reasons behind physical phenomena! It's so cool.

[@s_h_u_a_n]

The way it is illustrated and how you tried to explain it was incredible! Thank you!!

[@deadmemer4991]

I’m taking chemistry right now, and it’s really cool seeing how what I learn in school and what I learn from these videos is connected!

[@harishchad.]

I was just thinking the same Doing numericals of such topics seems boring but this topics are really interesting

[@neurofiedyamato8763]

@@harishchad. The math isn't all that fun to me either. The theories are really cool though.

[@andrewburnett8743]

Math is fun guys just ask my calc teacher

[@micahbirdlover8152]

@@neurofiedyamato8763 I like your pfp

[@poppymcpeake9961]

i was literally asked why we can see through windows for my admissions interview for university lol

[@jesusalvarez8864]

And how did that go?

[@jamess1787]

Did you get in?

[@teejation1064]

Damn thats a great question to ask

[@poppymcpeake9961]

@@jamess1787 yeah, they gave me an offer but i rejected it (and then got rejected from the universities i actually applied to, which was stressful 😅)

[@AlafndyAlosh]

@@poppymcpeake9961 it's okay bro we feel your pain

[@angieahite2597]

I can’t stop thinking about his kid(s) who will watch these videos at school for science class and being like: “THATS MY DAD!”

[@rohanjose_486]

Omg this was so helpful I din't know this was why we aren't transparent and how soil an opaque material became transparent when melted. Thank you so much

[@filip.pwr0]

"you can't touch anything" - Michael Stevens

[@debkalpapal2682]

Also Michael:Or is it ??

[@jimmym3352]

I tried that defense at my trial for touching a woman's rear end, didn't work. In the court of law, you can touch things.

[@Demigodess42]

"You can't touch this" - MC Hammer

[@not_a_chess_grandmaster]

in future , we can have special lenses that produces different wavelength of light and then we can see through anything as we wish.....😁😁😁😁😁

[@jessjomarcaraca7394]

It's actually true u just don't touch each other in a microscopic level

[@Alexander-is9jo]

This video is misleading, in reality we love Joe's puns.

[@themanpigface2165]

Clearly we (n) do

[@joostspohler2964]

I agree, it just misses some more explanations and some better conclusions. For example thou he did scratch molecular orbitals and he didn't go into band theory which is a big part in explaining optical properties.

[@rolfviehmann6240]

Fun fact: It's nowadays possible to fine tune which frequencies should be let through and which should be blocked. I can't really explain how it works in detail, but I know the following: For example, I wear glasses (not really made of glass, it's some kind of plastic) that have these two (intentionally created) features: * UV filter (always present): It blocks all UV rays as much as possible (since they can harm your eyes, and are useless for human vision anyway). * Blue filter (optional, costs extra): It blocks the highest frequencies of blue/violet light (basically right next to UV on a spectrum), since these are only minimally useful for human vision (since they are at the very edge of the visible frequency range), but they make your eyes go tired faster, since the photons have a lot of energy. And no, it does not filter out all blue light, just the highest frequencies, so everything only has a very slight yellow tint that you get used to very quickly. So both features are made for the same purpose: Let as much useful light through as possible, while blocking as much unnecessary photons as possible, which is good for the eyes and it really works: Since I have glasses with these two features, my eyes get tired much less quickly (which is important for my work, but also for driving in the night). So if you ever get glasses, and are asked if you want to have an UV filter and a blue filter, I can recommend it.

[@parthkhanayat420]

yes I also have the above mentioned blue block and UV filter in my glasses and I love it

[@maskedmarvyl4774]

Great video. It actually made me want to explore more of the topics you mentioned.

[@funkykong9001]

Could an alien species create their bodies out of molecules that were transparent to human-visible light? :-D

[@CG64Mushro0m]

big brain time

[@shaddjimenez4524]

No one knows but hey let your imagination go wild

[@TheRenegade...]

Doubtful

[@andrewfleenor7459]

There are fish that are pretty close to transparent. You could probably get aliens with similarly transparent bodies, but I think organs, bones or other structural components, etc, would still be pretty distinct as blobs with different degrees of transparency, rather than the alien looking like a glass sculpture. Probably not a route to invisibility, unfortunately.

[@spacepopeXIV]

@@andrewfleenor7459 No, fortunately, I don't know about you, but I don't want an alien species to be able to be completely invisible.

[@Scribe13013]

It's because of the heck...all answers lie in the heck

[@IveGotBeef]

Exactly 100 likes Perfection

[@Brindlebrother]

aw hecc, here we go again

[@mukfay]

THAT is the absolute best explanation I've ever heard! Thank you very much!

[@clove3665]

i just love how the setup is, it make videos more interesting. Also all the topics are just so fun to watch and ya how can i forget our beloved pbs digital , they are just doing such great work. :) :)

[@Real28]

I come here for the sciency dad puns. I need to make sure my science dad joke game is always sharp for my kids.

[@manjotbali8985]

Good I have one for you Never trust atoms they make up everything

[@herrschmidt5477]

@@manjotbali8985 guess he is able to also read two posts above...

[@NiTeLightYears]

@@manjotbali8985I laughed

[@ninjanerdstudent6937]

2:20 That would make a cool electron shooter game.

[@nagaprabhashetty8011]

JOE electron

[@Sohlstyce]

honey, that's called real life.

[@WilliamBoudle]

So glad you're back to making videos frequently. For awhile there I was starting to think you we're going to stop. You are one of my favorite science shows.

[@dimamatat5548]

"Transparent Joe doesn't exist, he can't hurt you" Transparent Joe: 0:36

[@not_a_chess_grandmaster]

in future , we can have special lenses that produces different wavelength of light and then we can see through anything as we wish.....😁😁😁😁😁

[@zacharysherry2910]

Terrifying. 😂

[@PankajKumar-bg4ke]

"The stuff that makes up stuff doesn't contain much actual stuff" 2020

[@electronresonator8882]

2:45 now you know, next time you have to stay under the sun for a long time, you should carry a glass with the size of your body, and put it between you and the sunlight

[@wizardsuth]

Or you could carry an opaque cover mounted on a stick (a parasol), or coat your skin with a substance opaque to UV light (sunblock).

[@anidubme_studios]

I found this channel at 3 am and Instantly I subbed. Great work pal.

[@ZZ-sb8os]

Merry Christmas Joe! Thanks for all the great content!

[@gcc2313]

I was just thinking about this like yesterday. What a coincidence.

[@cheesywiz9443]

this concept of electrons being in different energy levels was just introduced in my class yesterday.. it was a pleasant coincidance for me too

[@Mr1987atul]

Same here.. when i was cleaning my window glass yesterday.

[@weirddemocracy3432]

Mandela Effect

[@hickyxnicky411]

Love this video, already knew this, but I am so happy that glass is transparent in visible light because we wouldn't have astronomy or microbiology or any field that requires lenses!

[@thoughtfulcolors]

THANK YOU SOOOOO MUCH FOR EVERYTHING YOU AND YOUR SUPPORT SYSTEM DO ON KZbin. YOU'RE ONE OF MY 100'S OF INSPIRATIONS THAT HELPED ME TO FINALLY CREATE A KZbin CHANNEL.

[@drdotey2443]

This video was a nice little warmup for school. When you see all sorts of complex stuff it can be really nice to go back to the root of things.

[@Pikminiman]

Explanation was excellent, as always. Video effects and animation were above and beyond.

[@teodelfuego]

Really loved the 7 days in a week video and the hilarious plot twist halfway through. Keep up the good work

[@2dayesterday]

Maaaan! I was enjoying this! Continue more on this topic pleeease :D

[@victorvalverdes7801]

This video made me remember the classic "you can´t touch anything" from VSAUCE.

[@Shuizid]

Title: Why is glass transparent? Video: Why aren't all things transparent?

[@misterfister15]

all things are transparent, just to a certain degree. And it also depends on the material.

[@Shuizid]

@@misterfister15 more like "to a certain wavelength" - although there are some exceptions. Black holes certainly aren't transparent at all. Plasma might also be troublesome given the flowing electrons might be free enough to interact with all wavelengths (but no idea if this is true).

[@LivenrightHalo2]

Easy decision to subscribe to this guy. Great explanations. He understands what he's explaining well, and relays the information so I can too.

[@NishiAAAddiction]

Mindblown. While I knew about this on a..."surface" level, I love knowing how things actually work, and knowing exactly how light, molecules, pressure and all that actually work and interact is amazing! Thank you for the science, Joe. Keep up the great work ^_^

[@benediktgoerdt9827]

I have waited so long for an explanation like this, thanks so much!

[@Rika5589]

If we don't actually "touch" things, and only get as close as atoms allow, does that mean soft things have atoms that are more spread out, and rough things have atoms that are closer together? If so, is that why soft things are typically more flammable? If so, what about things like flour? Flour is super soft, but I don't think it's very flammable compared to hair. I need a video about soft things! Lol

[@jinxcraft1170]

Flour is actually super flammable, there have been a LOT of fires/explosions where flour is milled. Max Miller of Tasting History has done a video on it recently.

[@Rika5589]

@@jinxcraft1170 didn't know that!! Thank you for clarifying that!

[@jinxcraft1170]

@@Rika5589 To be fair, I didn't know that either till the video on Tasting History posted (that channel is really good & entertaining as well)

[@HexerPsy]

No, something is hard or soft based on many properties. Flour comes from grains, which are packed with carbohydrates. Those in turn are essentially long chains of sugar molecules. What makes flour so soft is that the grains are ground up to form a very fine powder. As a thin powder, the molecules have a lot of surface area - which means a chemical reaction can occur very quickly, because you can burn up a whole lot of molecules at the same time, if you can mix the flower with enough oxygen. Flour feels soft, because flour contains so much air, you push the mass of flower apart easily. Its just not connected to each other. In this case it has more to do with the structure of the compound, than molecular connections. As for what makes other objects soft, its the flex in the structure. Glass is 'spacious' in its molecular structure, but still very hard. A Buckminsterfullerene (basically a sockerball of carbon atoms) is also spacious and its very rigid. However, there are plastics that feel much softer, because the chains of plastic molecules can slide and move within the structure. That gives some plastics their flex.

[@MGSLurmey]

@@HexerPsy Tldr: Flour is very flammable when aerosolised. Things are soft because they are either very flexible/squishy or airy like a sponge.

[@mateoa.2366]

Really interesting! Wanna hear more about the nature of electrons and how does all that actually work, it's so crazy!

[@aroundtheworld5901]

super information, because I have never thinking about that. Thank You and stay Healthy

[@Mu51kM4n]

the game of trying to figure out what was wrong in the first upload that warranted a fix and reupload

[@Jeffsd17]

Many commenters noted that the little diagram of the electro-magnetic spectrum had the longer and shorter wavelengths reversed.

[@SotraEngine4]

Well Plenty wrong here too

[@x-cessive5977]

Man that last topic about electrons was really touching

[@danielmontana3610]

I love this video it answered two questions I've had for a long time (Why is transparent and if you could get a sunburn from behind a window)

[@kikolektrique1737]

From what I remember, the silica molecules in glass are spread far apart enough that light can easily move in between and pass through. This is why you can see right through glass. Also the molecules are stuck in place really well so that its always transparent. pretty neat eh

[@roserobson6707]

Pretty much, it is classed as a reflective material meaning light can bounce back than clear, hence the name, *- R E F L E C T I V E-*

[@ashketchup247]

My only problem with this content is that it wasn't around when I was a kid.

[@mikeyoung9810]

I had Star Trek back in the '60's. That's almost as good.

[@tiffanymarie9750]

Sounds like someone who didn't watch pbs growing up...

[@ashketchup247]

@@tiffanymarie9750 This is way better than the magic school bus or reruns of cosmos.

[@TheMarauderOfficial]

gotta love this level of science where “spin” and “rotation” are two entirely different things, and are both complicated to explain simply

[@nicknolte5700]

awesome vid, lots of nice practical stuff bout electrons

[@YounesLayachi]

I feel guilty for clicking. I know why but it's just so fascinating !

[@saturn724]

When you comb your hair, you're not really combing it, you're just repelling it with the comb's atoms

[@yanchee2023]

This is by far the best and most down-to-earth explanation I have ever seen, you put it in a way that even a young child could clearly understand the scientific facts behind how this really works, bravo.

[@janetgray2184]

This was the best explaination of glass i ever saw!

[@Aphrodite10]

6:08 , maths on the other side of atlantic. The best line lol

[@nex5261]

"Giving examples of glass" Me: you literally have glasses in front of your eyes

[@fromexoplanet21]

You explain things really well👏👏👏

[@whatyolookingat8992]

Love the vid, very informative, thank you

[@igorl7910]

Awesome video like always! A question, if we can never really touch anything since the electrons repels each other, how do things such paint, powders or even corona virus can stick to our hands?

[@narsisunkariya]

The repulsion between electron can be overpowered by adhesive forces of paints and powders, and maybe coronavirus uses some sticky substance which also have adhedive or some other forms of attractive force, which are large enough to overpower Electrostatics repulsion. This can be demonstrated by using same fingers coated with some adhesive.

[@himanshusingh-er7dd]

'The stuff which makes of stuff, doesn't contains much actually stuff'

[@Benji-Lindz]

A lot of this went over my head, but I feel smarter for watching it. :)

[@nickfroze]

New to this channel, love it already. Awesome work!

[@daviddavids2884]

you should not be so quick to praise this channel, based on this Flawed episode.

[@chaosinsurgency884]

Let us all take a minute to thank Adam for keeping us all together.

[@MJWITHER]

"The elctrons around a nucleus can't be just anywhere" hehe actually...

[@tomisinabel418]

Enunciate!

[@MJWITHER]

There is a non zero probability of finding the electron anywhere in the universe although it's astronomically low

[@MJWITHER]

Basically we can't say where the electron isn't but we can say where it mostly likely is

[@tomisinabel418]

That makes sense. Thank you

[@AjayThakur-fw2lv]

This is such a nice explanation

[@KevinVerstegen]

Good video, lots of information!

[@SupremeLeaderKimJong-un]

Chocolate ice cream is good but mint chocolate chip is where it's at

[@vitorhugo2331]

Wassup Kim from Korea

[@Scribe13013]

You don't deserve ice cream...you're horrible

[@cloudkitt]

When he's right, he's right.

[@jakemc4177]

I’m following you, I was following you on chippys couch

[@Real28]

Mint is the GOAT.

[@hiago3902]

This video it's very interesting as always

[@frilystolyviper]

Nice videos Mr. Hanson!

[@rianmacdonald9454]

Another science video very much enjoyed. THANK YOU

[@kevinluna8411]

Your flesh is transparent to x rays but your bones are not. They must be transparent to gamma rays, I imagine.

[@AverytheCubanAmerican]

Me when a joke goes over someone's head: 0:31

[@LiMCRiMZ]

Seeing titles like that is a personal hell for my sleep deprived self, thanks!

[@not_a_chess_grandmaster]

in future , we can have special lenses that produces different wavelength of light and then we can see through anything as we wish.....😁😁😁😁😁

[@thiagomartins1643]

Love all the videos!! Tank you

[@ForeverLumoz]

And then there’s me... I can get a sunburn inside a house, in the shade and even in winter in rainy Denmark 😅

[@miguelmontenegro3520]

Rough xD. My familly is dutch or italian or something, and it came to live in northeast Brazil. Once I sat my arm in the midday sun for literally 5 minutes at the bus. When I looked back it was almost burning like a barbecue.

[@SotraEngine4]

Because glass only blocks UVB, but not UVA

[@jjc5475]

instructions unclear. i am now a liquid.

[@ryanhiggins1902]

Thank you Very true

[@nenben8759]

I already conceptually and kinda mathematically understood how electrons and their interactions with light and such lead to larger phenomenon but its nice to hear a short n sweet conceptual overview to jog my memory lucky me you're not going hard and fast in to the math of qft as a conceptual basis for electron interactions thank God.

[@obbinexx3991]

Yknow I was thinking about this just yesterday and now I get an answer to it recommended...

[@michaelrose93]

5:25 *"Even in the glass of the screen that's between us right now"* < Glass? You mean the plastic???

[@MastaSquidge]

Phone screens have used glass for a number of years. Even prior to this video way back in the stone ages of 3 years ago when you posted this.

[@michaelrose93]

@@MastaSquidge The screen in between me and him is plastic, still is, because I'm watching on a flat screen.

[@mediumfast]

When he said "booper" I thought he was about to follow it up with "snooter" XD So close

[@punditgi]

What an eye opener!

[@ADHDerailed]

"Beneath the clothes, we find a man...and beneath the man, we find his...nucleus." -Nacho Libre

[@Niksinnocent]

Why you uploaded it twice😍???

[@rogersledz6793]

Thank you so much for uploading this video. It is helping me get through the pandemic!

[@KaleOrton]

Brilliant educator.

[@shaddjimenez4524]

This was an incredible video! D That why.

[@ReynaSingh]

I’ve seen this before

[@furrie1183]

Hey I know your channel!

[@ViraL_FootprinT.ex.e]

Transparency used to fascinate the hell out of me as a small kid. Always wondered about windows. And those clear Bic pens... I used to collect them because I thought they were treasure, lol. Pretty sure I grew out of that by the time I was 5 or 6 though.

[@CesareVesdani]

Glass washed with washing liquid, then washed with hot water squeaks when it is rubbed on a woolly jumper after the glass has dried.

[@theendereyes4395]

Ahh yes, the founder of Oscorp telling us about his master plan of turning invisible

[@MsAndaction]

I want more smart friends...I be having these types of conversations with myself...

[@ajay2552]

I relate with you.. all my friends are just dumb asses.. all they care about are some shitty video games.

[@manamritsingh969]

I do have smart friends but they don't like talking about subjects because they only correlate studying to good grades, nothing else besides that xD. It's a real shame.

[@aingel3846]

@@ajay2552 yupp they just gotta talk about Netflix in the science club

[@addicted2caffeine]

Commenting for the youtube algorithm. Because knowledge should never die and always be shared.

[@victorcastrellon4880]

Today I learned something new. Thank you so much

[@irenerosenberg3609]

PBS is supported my tax dollars!

[@ShakalDraconis]

One part of the photon absorption I've never been clear on : How close to "just the right amount" of energy in a photon does the difference between the energy potentials have to be for the photon to be absorbed. The way it's described here as well as other places, it's made to sound like it is EXACT (in the same way that every photon of a particular wavelength has exactly the same energy). However, the likelyhood that a photon has EXACTLY the right amount of energy, to within a billionth of a billionth of a billionth of a percent, is practically 0, as to my knowledge the possible wavelengths of light are not quantized, so there's nothing that would keep photons from occupying the full range of possible wavelengths generated. So clearly there's a little 'fudge room' when it comes to the exact energy that is able to be absorbed, but if that's the case where does the extra energy GO, as the energy cannot be lost? If it were able to be immediately re-emitted as a photon, then it would seem there'd be no reason that the same couldn't happen for all photons that contain at least the minimum amount of energy. This can also be seen in absorption lines, they are thin, but not infinitely so. So where does the 'width' in absorption lines come from? WHere does the extra energy come from/go?

[@gabor6259]

And how far apart can the electron and the photon be?

[@thomorl285]

These are some really good questions actually and I can try my best to clear things up from what ive learned from being a chemistry major. Youre definitely right about the fact that there is not one exact amount of energy a photon has to have to move an electron to a higher energy level. But from what ive learned an extremely specific wavelength of light has to hit the atom for an electron to jump to a higher energy level. Im not sure how specific the wavelength has to be but the margin of error is definitely less than a nm. Where does this extra energy go though? I would suggest if the wavelength was on the shorter side of the threshold, slightly more energy, then when the electron returns to a lower energy level it would just release slightly more energy. Very good questions though and now I am curious to look deeper into this also.

[@thomorl285]

I actually just researched this and absorption lines theoretically should be infinitely narrow but the atom can absorb a small range of wavelengths due to the Doppler effect which happens when the atom is in motion, you should definitely read into this its pretty cool.

[@DANGJOS]

@@thomorl285 The doppler effect contributes, but it's not nearly enough to explain how broad real absorption lines are. Look up *spectral broadening.* There are many types. Even a sodium vapor lamp has spectral broadening, which is why the two thin emission lines at 589.0 and 589.6 nanometers are not perfectly thin, as they should be. But in solids, you have many atoms and molecules arranged and coupled to many other atoms/molecules. In fact, these would probably be better described by a band structure, rather than the oversimplified Bohr model shown in this video. Absorption lines in real solids are *extremely* broad. They have to be, otherwise pigments wouldn't exist. You could emit colored light through vapor lamps, but if a solid only absorbed a specific amount of energy, then so little light would be absorbed that we wouldn't notice any color change at all! All pigments would be white! What a boring world that would be.

[@HexerPsy]

+ @Thomo RL Actually that has to do with 3 things. 1. Photons come in quanta (quantummechanic) which is defined as its frequency * the Planck's constant. So light comes in set stanges of energy. 2. How much wiggle room within absorption lines there is, is based on the amount of surrounding atoms. No electron can have the exact same state as the other electrons in the molecule (dunno why, thats just how it works). The exact state also changes on the surrounding bonds inside a molecule. Imagine a complex protein molecule - electrons at the center have slightly different states than those on the outsides. You can imagine that the absorbtion bands for a complex protein are actually very complex and wide - sometimes overlapping, that it aborbs most light and isnt transparent for a lot of frequencies of light. This is also why a cold gass has narrower bands - but a hotter gass has wider bands, because collisions between molecules (which increases with heat) slightly change the state of colliding electrons. This widens the spectrum bands - and then I'm ignoring the dolper effect in this story - this widens the band a little more. 3. A photon doesnt need to be exactly the right energy level. It can also be higher - but never be lower. If the energy is higher than the energy that binds the electron to the nucleus, the electron escapes and the atom becomes an ion (charged particle). This is the photoelectric effect, a piece of research that Einstein got his Nobel prize for. The electron absorbs enough energy to escape, and the remaining energy gets transfered into speed. If there is more than enough energy to jump to the next energy state, but not enough to let the electron to escape - the event does not occur - the photon passes through and the material is mostly transparent for this frequency of light. As photons get higher in energy another effect occurs: This is called the Compton effect. The photon encounters a electron. The electron absorbs enough energy to escape the atom. However there is so much energy left in the photon, it changes direction and continues as a lower energy photon. The angle + the loss of frequency = the amount of energy absorbed by the electron. This effect only occurs well above the binding energy of electrons to the nucleus. You are dealing with x rays at this level. The change of angle is called the scattering of photons - resulting angles of 0-60 degrees (so it fans out behind the scattering object) are common - but there is also a common reflection (angles between 160-180 degrees) for x rays to reflect back towards their source. So you would be safest, standing next to the person getting x rayed - not next to the x ray source. This ionization is a real problem. It's minimum level occurs at UV light from the sun. It can ionize atoms in your cells and lead to all kinds of damage. If that damage occurs on your DNA, you may develop cancer later on. You body's immediate response to the damage is called a sunburn. Okay, class is done - go celebrate xmas!

[@gregmonks]

When I worked in a foundry many years ago, I was amazed to see the shadows of people through yellow-hot sheets of steel. I think pretty much anything can be transparent under the right conditions.

[@HuFlungDung2]

Interesting. Do you suppose that people make better reflectors? I'm imagining that the heat coming off the sheet reflects off the person, coming back through the sheet, thus reinforcing the light output on Your side of the sheet.

[@gregmonks]

@@HuFlungDung2 I don't think it matters what the surface is, unless it's one that absorbs light.

[@Taz6688]

Foundry work attracts all sorts, one I worked with used to throw scraps of paper with peoples names on into the oven, he swore he could see people inside.

[@rickkwitkoski1976]

Excellent! Thank you, Joe.

[@jacksagrafsky4936]

Saw this video and thought for a minute why the hell is glass transparent. I wear glasses and they help me to see, my house has windows that keep the heated air out and the cold air out too. So why is, glass invisible. I had a hard time following your discussion but will NEVER take glass for granted again.

[@FharishAhmed]

RE-Upload?

[@rohithkumarsp]

ikr? i had opened the video on chrome, went to sleep, wake up and continued and halfway through the video said "unavailable" lol here's the original link kzbin.info/www/bejne/qYbQpISKor16fMk