the radium girls LICKED the stuff ... continuous incorporation is a lot worse than a little bit shielded by metal and glass ... although you are right, that it's not advisable to wear that stuff ... Do you recall the unshielded X-ray devices in shoe shops in the 50s, so you could see your skeletal foot in the shoes to determine if they are of the right size ? Now that's dangerous ...
Yup, I do. Also, radioactive dish plates were kinda bad, I don't know if it was radium paint though. Man, people need to do more research before putting stuff for personal use.
people probably didnt tell anyone about these because kids might be more attempted to break something for a glow in the dark cast, i mean fully grown people like us would never do that though... right?...
To continue on this luminescence theme, could you also cover electroluminescence that's often used in back-lighting of LCD displays and fancy Tron-like "lighting" that's used on cars, bikes and by some modern dance troupes?
I used to have a little doll, some kind of dog/bunny thing, called Pj Sparkles. Which I proceeded to name, in my lack of imaginative 6 year old ways, Sparkles. That thing still glows in the dark and its been a good 20+ years. Not particularly relevant to the video but it reminded me of it. Great video!
The glow in the dark stars that I put in my playroom at my grandmother's house as a child are still there and they still sort of glow at night. plus my gma uses that room as her bedroom now, which I think is kinda sweet because we've always been close
We also use these super cool fluorescent dye molecules for other stuff, like for example to measure the amplification of DNA with Real-Time PCR. My personal favorite is still bio luminescence, which essentially is chemoluminescence inside living cells, we also use some of those compounds at the lab when sequencing DNA, more specifically the ones fireflies use to glow in the dark.
My mom used to buy me some of the stars. One day she got me a glowy castle set. We were talking one night and she thought she saw one if the stickers blink. The said they were demon possessed and then threw them away. :(
+Nathan Trone Actually, some idiot has already tried exactly that 20 years ago with the goal to build a home reactor. There is even a book about it. Just google "The radioactive boy scout". There is no idea too stupid, that people wouldn't try it. That's why the Darwin award is so important.
I wish there was a version of this on SciShow kids, my oldest is wanting to know but the language in this is a bit advanced for a six year old lol. We'll still watch together and talk about it but I'll also keep looking for kid friendly resources
Water gets in your ear by going inside your ear and then it stays because of how small the tubes are, and especially because of the hair in there. the small openings mean the surface tension of the water is strong enough to hold it inside for a while. Don't ask how to get it out. That's a question as old as time that even science doesn't have an answer to.
It's 4:33am I am obsessed with glow in the dark stuff being older I probably shouldn't be so fascinated by it as I am since I was little I've always loved glow in the dark things fun memory I have that could be the first time I learned about it we were moving and found stars through out the rooms I love glow in the dark so much I have blankets stats toy figures paint ect.it goes hand and hand with my love of space and clouds
Hi Hank, which one was used in your No Edge T-shirt? Went to a movie last week and forgot I was wearing it, when the lights went down that sucker really lit up.
Is a phosphor limited to one column of activation? Or can a phosphor that glows by absorbing energy from light (photoluminescent) also glow from exposure to tiny amounts of one of the radioactive sources (radioluminescent)?
As light (or other energy) enters it excites the electrons, making them move to a higher orbital tier. Over time the electrons settle down, releasing their energy as visible light.
+TheCodeAlive No, because the compounds used are photoluminescent, not thermoluminescent. When a photoluminescent atom absorbs a photon of (approximately) the correct frequency, it "excites" one electron, increasing its energy and raising it to a higher energy orbital. Some time later, the electron will "relax," falling back to the lower energy orbital and releasing a photon of the same frequency. Though most photoluminescence is relatively fast and called "fluorescence," it can rarely proceed very slowly in a process known as "phosphorescence" (named after white phosphorous, even though technically that is not phosphorescent but chemoluminescent). The mechanism behind this is very complicated. In a phosphorescent atom, the excited electron has a high probability of "intersystem crossing," in which its spin changes to be parallel to the spin of its partner. Normally, electrons in an orbital are paired up, with the two members of a pair having opposite spins. This is due to the Pauli exclusion principle, which states that two particles cannot occupy the same quantum state; so if two electrons are otherwise identical (in the minimum available energy state), they must have opposite spin. When one electron is excited, this pairing is generally still preferred, so the spins typically remain parallel, a so-called "singlet state." However, because the excited electron is now alone in the higher energy state, it is possible for it or its partner's spin to flip, forming a "triplet state," but this is usually not energetically favored. In a very few compounds or solutions, this type of flipping may actually be favorable, usually due to relativistic effects in non-circular orbits (the new electron may favorably align its spin with the angular momentum in the non-circular orbit), especially if there are magnetic species in solution. When this happens, the electron is "stuck" in a metastable state, because it cannot relax back to the lower-energy orbital without first flipping its spin again due to a thermal or quantum fluctuation. Even this extremely "slow" relaxation typically occurs on the millisecond timescale for most phosphors, but in the case of zinc sulfide, strontium aluminate, and probably a few other compounds, it can take minutes to hours on average. Because this is a probabilistic process, some atoms may relax very soon by pure chance, while others will take quite a while, which allows a large sample to luminesce continuously (albeit at an exponentially decreasing rate) for quite a while.
***** In the case of visible light emission, I think that is the dominant cause, but there are lots of ways black bodies radiate. Actually, a black body radiates in _every_ possible mode, including molecular rotation and vibration, electronic ejection and recombination, internal and external electron transitions, nuclear rotation and transitions, dipole-dipole and dipole-monopole radiation, etc. Basically any way charged particles can move can emit radiation. How often each of these happens at a given temperature and the energy released by each are determined by the black body spectrum.
What is happening to the phosphor when the light hits it that causes it to re-release the energy as visible light? What happens to the photon when it gets absorbed?
The reason HOW these compounds store light for so long would have been far more welcome than telling us what we already know and could find with 2 minutes of google searching!
I still don't get it . How exactly can a material get energised by light and how does that energy becomes light again?? Is the light it emits the same light as it absorbed? I guess not but if so, does that mean the lights kind bounces around with-in the material and only a small amount of it escapes over time?
+L Galicki, in principle yes, but there is not that much radium in it and the upper layer of dead cells of your skin provide some protection so you won't die of radiation within hours ;->, but you shouldn't lick at it. Incorporation is pretty nasty.
I've read that this strontium aluminate that I suppose my watch uses is doped with europium and dysprosium, is that right? If so I probably have something like a nanogram of each :-) They glow all through the night if they've been exposed to strong enough lamp or sun light
blacklight results in fluorescence and and doesn't evolve a meta-stable excitation state, while phosphorescence does. So in short: fluorescence immediately transforms light of higher frequency (UV) into light of lower frequency (visible), while at phosphorescence you populate a meta-stable state over time with light of a given frequency, which is emitted at the same frequency over time as the electrons drop from their excited meta-stable state back to their ground state. As a result phosphorescence shows this typical "after glow" in the dark, if you shut down the light, while fluorescent material does not, when you switch of the light source. if you switch of the UV light, it stops emitting.
Frank Schneider That isn't my question. Take two identical glow in the dark stars, and charge one with regular light and the other with a black light, for the same amount of time. The one charged by the blacklight instantly lights up, and the one charged by normal light takes a while. Then when you remove the light sources, the blacklight charged one dims very quickly while the one that absorbed normal light lasts much longer.
Nicholas Braden Yes it is. Phosphorescence involves a meta-stable state and therefore has this after glow, fluorescence does not, and therefore immediately stops when the light source is switched off.
*SciShow I want to know how water goes in to your ear and how do you get it out*,because in my experiences on beaches is you take a *long dive theres water inside your ears*,*while when you dive for a short time it doesn't*
bis(2,4,6 trichlorophenyl) oxilate; 9,10 diphenylanthracene; diethal phthalate; sodium acetate and hydrogen peroxide. One of my favorite chemical reactions.
My stars are actually still on the ceiling of my childhood room at my parents' house. I used the blue tack and it won't come off their ceiling, so they just left them. :D
I had two theories to this right before I watched this: radioactive compounds and energised electrons emitting photons as they fall back to lower energy levels. Looks like I was on the right track.
But where do the photons come from? Does the material collect them and emit them later? Because photons are actual things, and if actual things are being thrown off of the material constantly, eventually it should run out... where does it come from?
So, wait. Do the Phosphors take in the light from the sun (or wherever), which excites the molecules to vibrate (due to their unique chemical makeup), which so happens to emit a wave of energy within our visual spectrum as a sort of energy byproduct? Is that how it physically works? Or is there something happening that's not so intuitive?
the electrons within the molecule do that not the molecule itsself though the shape of the molecule determines what frequency of energy is required to lift the electrons
we just put the glow in the dark stars on my son's ceiling....I bought them and my husband took it upon himself to make an accurate representation of the sky...utilizing a compass app, star projection, ruler, etc. haha.
My watch has Tritium dots for the numbers. Before the half lives caught up to it, it glowed so bright, all night, that I had to put it face down on the bedside table.
I love when Lego pieces come in glow in the dark colors. It is awesome to see that it's a pretty simple thing that captures and reemits the light.
Anyone else still have those glow-in-the-dark stars on their ceiling? I do!
at my mother's home in my old bedroom i do.
yep
Not stars, but planets for me. xD
My girlfriend does haha
+BusiedGem Official cool
"without being dangerous to humans using the watch" *cough* radium girls *cough*
they were not using the watches
the radium girls LICKED the stuff ... continuous incorporation is a lot worse than a little bit shielded by metal and glass ... although you are right, that it's not advisable to wear that stuff ... Do you recall the unshielded X-ray devices in shoe shops in the 50s, so you could see your skeletal foot in the shoes to determine if they are of the right size ? Now that's dangerous ...
Yup, I do. Also, radioactive dish plates were kinda bad, I don't know if it was radium paint though. Man, people need to do more research before putting stuff for personal use.
I had a glow in the dark cast on my broken leg as a teenager. Sketched out so many people with it huehehehe
I never knew you could have a glow in the dark cast!!! It would have made my experience with a broken arm more enjoyable.
people probably didnt tell anyone about these because kids might be more attempted to break something for a glow in the dark cast, i mean fully grown people like us would never do that though... right?...
I'm not fully grown... Eh I still would never do that since it is a lot of work for something that is just a distraction and an inconvenience.
To me, it'll always be magic.
Well, it's a quantum effect, so it might as well be.
what is magic
Thee Original Trainer Gamer The thing that's in every child's heart.
I think that stuff is called blood
THE FUTURE IS NOW THANKS TO SCIENCE!!!!
To continue on this luminescence theme, could you also cover electroluminescence that's often used in back-lighting of LCD displays and fancy Tron-like "lighting" that's used on cars, bikes and by some modern dance troupes?
I had those glowy ceiling stars on my ceiling as a kid. They're awesome!
I used to have a little doll, some kind of dog/bunny thing, called Pj Sparkles. Which I proceeded to name, in my lack of imaginative 6 year old ways, Sparkles. That thing still glows in the dark and its been a good 20+ years.
Not particularly relevant to the video but it reminded me of it.
Great video!
I love you guys. I'm a visual learner and I love science, you guys have taught me so much since I found your channel :)
The glow in the dark stars that I put in my playroom at my grandmother's house as a child are still there and they still sort of glow at night. plus my gma uses that room as her bedroom now, which I think is kinda sweet because we've always been close
Man, I still got those stars on my celling.
Today we give glow in the dark toys to kids... but in Soviet Russia, kids give glow to toys.
no that was/is in Chernobyl Ukrainian. there everything glowes.
sirBrouwer You are right, Ukraine was in the Soviet Union when Chernobyl happened but that's not the same as Russia. My mistake ^_^
Master Therion finally I did it now I can sleep for 5 years under this rock. See you in 5.
sirBrouwer What did you finally do? Why are you sleeping under a rock? Sorry, I am confused.
Master Therion i was trying to take the piss out of my self. As if I only knew this only fact and nothing else.
We also use these super cool fluorescent dye molecules for other stuff, like for example to measure the amplification of DNA with Real-Time PCR.
My personal favorite is still bio luminescence, which essentially is chemoluminescence inside living cells, we also use some of those compounds at the lab when sequencing DNA, more specifically the ones fireflies use to glow in the dark.
My mom used to buy me some of the stars. One day she got me a glowy castle set. We were talking one night and she thought she saw one if the stickers blink. The said they were demon possessed and then threw them away. :(
I have a ton of glow in the dark stars on my bedroom walls and ceiling!
Me too....
I used to have a ton in my old bedroom...I had no idea that they had already been around for so long
OH COOL! I can melt down my collection of 5000 glowing military watches and make a nuclear reactor!!! :P
it comes with inbuild timer
+Nathan Trone
Actually, some idiot has already tried exactly that 20 years ago with the goal to build a home reactor. There is even a book about it. Just google "The radioactive boy scout". There is no idea too stupid, that people wouldn't try it. That's why the Darwin award is so important.
It feels so good when you know the answer before the video and confirm your right.
I wish the explanation was more in-depth, because trapping the light and emiting it, isn't.
thx!!!! I asked this 2-3 months ago :)
I usually just go to wikipedia and ask the man in the counter there.
+imfrommanndame AT the counter?
+mondos2001 IN.
I wish there was a version of this on SciShow kids, my oldest is wanting to know but the language in this is a bit advanced for a six year old lol. We'll still watch together and talk about it but I'll also keep looking for kid friendly resources
Hank, you're a STAR ... of UA-cam!
Thanks for making this video, I have often wondered what made toys glow in the dark.
yeah, thanks for telling me stuff i have known since being a kid. which was well over 20 years ago.
Can you do one on cerebral aneurysms? I had one rupture at 19 and would love to learn more!
Am a neutralscientist. You should go as your doctor or you shouldn't ask your doctor.
Do an episode on how water gets in your ear and how it gets out
yes pls
Your ear produces a bubble that blocks the water, and if you pop it, instant ear infection.
+Crazy Conspiratard Scary
Water gets in your ear by going inside your ear and then it stays because of how small the tubes are, and especially because of the hair in there. the small openings mean the surface tension of the water is strong enough to hold it inside for a while. Don't ask how to get it out. That's a question as old as time that even science doesn't have an answer to.
It gets in by going through the hole it gets out by going through the hooe
thank you!! i got some of those famous stars a little bit back as a pass me down from a friend's mom and this was really helpful!!!!!
It's 4:33am I am obsessed with glow in the dark stuff being older I probably shouldn't be so fascinated by it as I am since I was little I've always loved glow in the dark things fun memory I have that could be the first time I learned about it we were moving and found stars through out the rooms I love glow in the dark so much I have blankets stats toy figures paint ect.it goes hand and hand with my love of space and clouds
How come everytime I walk through a spider web, I instantly become a karate expert?
Hi Sci-Show
Can I ask what is healthier, Normal full fat milk or milk that has the fat removed and sugar added.
Thanks
Hi Hank, which one was used in your No Edge T-shirt? Went to a movie last week and forgot I was wearing it, when the lights went down that sucker really lit up.
I did not expect hank green to be the one to answer this for me
You just run 'em over, that's what you do
This video makes me want to go to a rave really bad.
Aw cool I just found a old glow in the dark bouncy ball and was wondering how they work but this has answered my question
I can just picture little Hank recreating the constellations on his ceiling, or else making up his own like one for John called 'Dorkus Major'
That was an epic episode!
Is a phosphor limited to one column of activation? Or can a phosphor that glows by absorbing energy from light (photoluminescent) also glow from exposure to tiny amounts of one of the radioactive sources (radioluminescent)?
But how they work? How light (photons) enters the toy and why toy glowing for long time? I need physics answer, not just chemical name of stuff.
As light (or other energy) enters it excites the electrons, making them move to a higher orbital tier. Over time the electrons settle down, releasing their energy as visible light.
would heating up the material would also make it glow?
TheCodeAlive
Depends on the material, in theory yes, however heat tends to mess with chemical properties.
+TheCodeAlive No, because the compounds used are photoluminescent, not thermoluminescent. When a photoluminescent atom absorbs a photon of (approximately) the correct frequency, it "excites" one electron, increasing its energy and raising it to a higher energy orbital. Some time later, the electron will "relax," falling back to the lower energy orbital and releasing a photon of the same frequency. Though most photoluminescence is relatively fast and called "fluorescence," it can rarely proceed very slowly in a process known as "phosphorescence" (named after white phosphorous, even though technically that is not phosphorescent but chemoluminescent). The mechanism behind this is very complicated.
In a phosphorescent atom, the excited electron has a high probability of "intersystem crossing," in which its spin changes to be parallel to the spin of its partner. Normally, electrons in an orbital are paired up, with the two members of a pair having opposite spins. This is due to the Pauli exclusion principle, which states that two particles cannot occupy the same quantum state; so if two electrons are otherwise identical (in the minimum available energy state), they must have opposite spin. When one electron is excited, this pairing is generally still preferred, so the spins typically remain parallel, a so-called "singlet state." However, because the excited electron is now alone in the higher energy state, it is possible for it or its partner's spin to flip, forming a "triplet state," but this is usually not energetically favored. In a very few compounds or solutions, this type of flipping may actually be favorable, usually due to relativistic effects in non-circular orbits (the new electron may favorably align its spin with the angular momentum in the non-circular orbit), especially if there are magnetic species in solution. When this happens, the electron is "stuck" in a metastable state, because it cannot relax back to the lower-energy orbital without first flipping its spin again due to a thermal or quantum fluctuation. Even this extremely "slow" relaxation typically occurs on the millisecond timescale for most phosphors, but in the case of zinc sulfide, strontium aluminate, and probably a few other compounds, it can take minutes to hours on average. Because this is a probabilistic process, some atoms may relax very soon by pure chance, while others will take quite a while, which allows a large sample to luminesce continuously (albeit at an exponentially decreasing rate) for quite a while.
***** In the case of visible light emission, I think that is the dominant cause, but there are lots of ways black bodies radiate. Actually, a black body radiates in _every_ possible mode, including molecular rotation and vibration, electronic ejection and recombination, internal and external electron transitions, nuclear rotation and transitions, dipole-dipole and dipole-monopole radiation, etc. Basically any way charged particles can move can emit radiation. How often each of these happens at a given temperature and the energy released by each are determined by the black body spectrum.
What is happening to the phosphor when the light hits it that causes it to re-release the energy as visible light? What happens to the photon when it gets absorbed?
The reason HOW these compounds store light for so long would have been far more welcome than telling us what we already know and could find with 2 minutes of google searching!
I have 20 years old u have tons of glowing stars :D thanks guys i really like this episode
Tritium is still very popular, and probably the only current solution, in night sights.
I still don't get it . How exactly can a material get energised by light and how does that energy becomes light again?? Is the light it emits the same light as it absorbed? I guess not but if so, does that mean the lights kind bounces around with-in the material and only a small amount of it escapes over time?
Wow i've always wanted to learn about this. Cool !
amazing video 👏🏻👏🏻
Why does it hurt so bad when I stub my toe?
Because you're not paying attention.
Stop being a cheapskate.
Your toe sends a chemical message to your brain via your nervous system. Its hurts so bad to teach you a lesson not to do it again.
The tips of toes and fingers have a higher density of nerves.
What I would like to know is why it hurts worse when your tired.
You just rammed your toe into something.
I was starring at my ceiling that has the glow-in-the-dark stars when I got the notification for this video
If you break that watch, could direct contact with the radio luminescent pointers be harmful?
+
+L Galicki,
in principle yes, but there is not that much radium in it and the upper layer of dead cells of your skin provide some protection so you won't die of radiation within hours ;->, but you shouldn't lick at it. Incorporation is pretty nasty.
3:10 what are those?
My green stars are still on the ceiling at my parents' house.
When I was younger, my parents didn't want to glue stars to the ceiling, so they decorated my room with glow-in-the-dark starry wallpaper. ;)
Excelente vídeo, muchas gracias por el magnífico trabajo.
I've read that this strontium aluminate that I suppose my watch uses is doped with europium and dysprosium, is that right? If so I probably have something like a nanogram of each :-) They glow all through the night if they've been exposed to strong enough lamp or sun light
I've always been interested about glow in the dark stuff.
can GITD things absorb any kind of energy to store light energy in them??
Those stars were the shit
Drew Caylor exactly
Why is there a Charmander in my toilet?
Stop using the pokemon incubators as a toilet......
Put your phone down and stop playing Pokemon Go for a few minutes.
Why does shining a blacklight on them charge them up so much faster but then they also glow for a shorter amount of time?
A good question that highlights an over generalization Hank makes. The teeth thing is fluorescence not phosphorescence.
blacklight results in fluorescence and and doesn't evolve a meta-stable excitation state, while phosphorescence does. So in short: fluorescence immediately transforms light of higher frequency (UV) into light of lower frequency (visible), while at phosphorescence you populate a meta-stable state over time with light of a given frequency, which is emitted at the same frequency over time as the electrons drop from their excited meta-stable state back to their ground state.
As a result phosphorescence shows this typical "after glow" in the dark, if you shut down the light, while fluorescent material does not, when you switch of the light source. if you switch of the UV light, it stops emitting.
Frank Schneider That isn't my question. Take two identical glow in the dark stars, and charge one with regular light and the other with a black light, for the same amount of time. The one charged by the blacklight instantly lights up, and the one charged by normal light takes a while. Then when you remove the light sources, the blacklight charged one dims very quickly while the one that absorbed normal light lasts much longer.
Nicholas Braden
Yes it is. Phosphorescence involves a meta-stable state and therefore has this after glow, fluorescence does not, and therefore immediately stops when the light source is switched off.
Frank Schneider I am not observing an immediate stop in either case.
How is Hank present in every single useful scientific video?!?!?
sci show! how do grow toys work such as orbeez or those kind sold at dollar tree?
I wish you'd do little animations showing out the photons were absorbed and re-emitted, and how the chemicals react to make light.
I like this guy better than the other
Thanks 👍🏻
What is the psychology behind "comfort" or what we define as "comfortable"?
how can you check how much is left of a battery by squeesing it?
How exactly is that energy stored in the phosphorus material
*SciShow I want to know how water goes in to your ear and how do you get it out*,because in my experiences on beaches is you take a *long dive theres water inside your ears*,*while when you dive for a short time it doesn't*
top 10 youtubers and science behind their success
Thanks, Hank! You're like a modern day Beakman. :-) Perhaps you can answer a question he never answered for me: How do hair spray and hair gel work?
0:11 We need to bring this back lol
hey i got a question for you guys what is a micro climate exactly ?
I noticed an extremely quick on-off cycle among the fireflies a few nights ago.
bis(2,4,6 trichlorophenyl) oxilate; 9,10 diphenylanthracene; diethal phthalate; sodium acetate and hydrogen peroxide.
One of my favorite chemical reactions.
man just the other day I was wondering if you guys did a video about this
My stars are actually still on the ceiling of my childhood room at my parents' house. I used the blue tack and it won't come off their ceiling, so they just left them. :D
I had two theories to this right before I watched this: radioactive compounds and energised electrons emitting photons as they fall back to lower energy levels. Looks like I was on the right track.
Hey! Y didn't u talk about the sights on guns? They glow pretty powerful.
Looks so cute :)
I have a question: when do glow in the dark stuff (made with liquid) stop glowing?
Where are phosphorescent colors on the spectrum? Is it diff than just green like UV is different than purple
What about color changing nail polish from temperature change
As a kid I always enjoy having things that glow in the dark.
I don't have that much,but i got glow in dark toy cars. *Childhood flashbacks*
What is a plumbus for?
But where do the photons come from? Does the material collect them and emit them later? Because photons are actual things, and if actual things are being thrown off of the material constantly, eventually it should run out... where does it come from?
Episode idea: Why do we like solving puzzles?
THANK YOU
I still have phosphorescent stars on my ceiling. I refuse to grow up!
Radioluminescence is great because it is basically permanent. Used in tritium gun sights for example.
also, Scorpions glow under UV light.
King of Randon xD
+Sulaiman Faisal random*
+Sulaiman Faisal lol
+Peter the Porcupine xD
Sulaiman Faisal King of Random ftw
So, wait. Do the Phosphors take in the light from the sun (or wherever), which excites the molecules to vibrate (due to their unique chemical makeup), which so happens to emit a wave of energy within our visual spectrum as a sort of energy byproduct? Is that how it physically works? Or is there something happening that's not so intuitive?
the electrons within the molecule do that not the molecule itsself though the shape of the molecule determines what frequency of energy is required to lift the electrons
Alistair Shaw
Thank you! I figured it was something like that. Really neat.
we just put the glow in the dark stars on my son's ceiling....I bought them and my husband took it upon himself to make an accurate representation of the sky...utilizing a compass app, star projection, ruler, etc. haha.
When he mentioned the stars, I couldn't help but look at my stars on the ceiling.
Anyone else notice the color changes to Hank thoughout the video? ? Looks like he's glowing ;)
Hey so do fireflys use chemilumescence?
I still have the glowing stars on my ceiling they've been there fo 10+ years! Like an old friend.
Wonder how long the radioluminescent coatings last (they have a rather short half-life).
I'm 19 and I still have those glowing stars on my ceiling
what is the black chemical in a carbon battery and what can it be used for @SciShow +SciShow
My watch has Tritium dots for the numbers. Before the half lives caught up to it, it glowed so bright, all night, that I had to put it face down on the bedside table.