Can Light Bump Into Other Light?

I show you how second harmonic generation and frequency doubling works
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[@jerotoro2021]

If you held that crystal over a camera, would you be able to see what the world would like if our visible spectrum was 50% lower frequency? That would be interesting to see.

[@user-zb9ie4do7r]

You would likely need to design a lense based on this principle to properly capture it, otherwise you are not emulating the structure of the crystal that causes this light refraction

[@tiffanyvalencia8415]

We'd mostly be seeing in green, blue, purple.

[@darktherapy]

Don’t mess around with crystals, you’ll fu*k up your chakras!

[@RealNovgorod]

No, the second-harmonic crystals in laser pointers are extremely narrow-band in order to be efficient. Only that one specific infrared wavelength (around 1064nm) is partially converted into green light (532nm) with some ten percent of efficiency, everything else is unchanged. So only if you have a strong light source at that 1064nm wavelength in the room, you might expect to see a tiny increase in green hue - without the crystal that wavelength would be simply invisible. Also, it's a 2nd-order nonlinear effect and you only get that efficiency if you pump 50-100mW of infrared light through a tiny spot on the crystal. If you use the crystal as a lens for your glasses with only eye-safe ambient light, the power density on the crystal will be millions of times less and the conversion efficiency scales with the power density squared, so you will see absolutely nothing, even if the whole room is lit up in 1064nm light. Frequency-doubling of the entire visible spectrum is extremely challenging because these crystals typically work only for a "single" (i.e. narrow-band) wavelength and even then getting more than 10% efficiency is considered good. If you want to convert a broad range of wavelengths simultaneously, you have to make the crystal very thin (look up "phase matching"), which makes it very inefficient, so this is only useful for high-power or short-pulsed lasers. Maybe you could make a giant stack of many different crystals tuned for different wavelengths covering the whole visible spectrum, but the resulting contraption would probably be meters thick and re-absorb all the converted light...

[@hex00ffff]

@@darktherapy That was hilarious!

[@laarmyguy]

I love how even I can understand most everything. He is very good at information presentation.

[@JJT1705]

Yeah and I also don't have enough knowledge of physics and I understand almost everything

[@darealpoopster]

@@JJT1705 You probably don’t actually understand it though.

[@DGRIFF]

I think you're probably above average intelligence... this channel is lost on people with average intelligence.

[@RealGedagedi]

@@darealpoopster oh fr?

[@BariumCobaltNitrog3n]

@@RealGedagedi Understanding is being able to explain it to someone else. The information here might make sense to people but I also doubt most understand it. Think about it: the average IQ is 100.

[@danielleohallisey4218]

I recently retired from an engineering career that included extensive work in nonimaging optics (the optics of illumination devices, for the most part. I designed some photography lighting, high-efficiency concentrators for solar energy, and a couple of very badass flashlights, over the decades I spent in that arena). While I've studied and have understood the concepts you put forth in your videos, I give you great credit for bringing those very abstract ideas to life. Thank you for all you do to bring science to us, your audience!

[@ali-g]

I am an engineering major myself and would love to listen your experience

[@BariumCobaltNitrog3n]

Flashlights like the SyniosBeam or Maxablaster? The 12" mirror is pretty effective. The short arc speaks for itself though. I'd like to make a gigathrower with a nice spill. Drivers are getting more efficient too.

[@danielleohallisey4218]

@@BariumCobaltNitrog3n it was pretty long ago, when LED flashlights were brand-new and I had some good ideas for reflector/lens design. Now you can just buy aspheric lenses off the shelf that do a better job, but 20 years ago I was, like, cutting edge...

[@danielleohallisey4218]

@@ali-g one of the best things I ever did was learn to use a specialized piece of software, called OptisWorks. It's now sold by National Instruments but still works the same way; it's a modeling add-in for SolidWorks CAD software. I eventually bought a (very expensive) license for it and was the only person in northern New England who had it, and knew how to use it. Most of the jobs were pretty straightforward. A client would bring me a design done by someone who had no idea how to build an optical system, and pay me to double, triple or quadruple the output (brightness, focus or both) of the system. Really fun stuff!

[@BariumCobaltNitrog3n]

@@danielleohallisey4218 I've been experimenting with lenses and reflectors and combinations of them for a few years. Did you check out those two flashlights? Handheld, battery operated, not tethered and must run for minutes (no strobes) and the record is around 52M candela and 7.5 kilometers. From a single led and the beam is 12" wide. I'm a flashaholic. Budget light forum.

[@ogranesson]

i still wonder how he comes up with these questions no one else does but finds interesting soon after.

[@louf7178]

Must have been tinkering with a green laser.

[@ryandoesstuffapparently1540]

That’s just what happens when you have a curious mind. He probably thinks he has too many questions to make videos about haha

[@wernerviehhauser94]

Just read a bunch of physics papers on arxiv :-) physicists ask the questions all the time. A few years ago, there was an experiment involving ATLAS and CMS where they showed that high energy photons can interact in vacuum.

[@HUMAN-gg7zl]

i had this question! and i tried to hit a laser bean path with another laser, but nothing happened, and Now i know why (sry if my english is not that good)

[@yourleftisttesticle]

Other people obviously have asked these questions. That's why he knows the physics surrounding the experiments and demonstrations. His videos are cool, but he isnt actually teaching us some brand new aspect of physics he discovered.

[@nikolausluhrs]

We actually have a really cool way of measuring single photons of infared light. Look up superconducting nanowire single photon detectors. The ones ive worked on operate at 1550 nm

[@D-train69]

What was the title of your job or whatever you volunteered for????

[@nikolausluhrs]

@@D-train69 i was a "undergraduate research fellow" the devices in this paper were fun to play with in the lab: A near-infrared 64-pixel superconducting nanowire single photon detector array with integrated multiplexed readout

[@nobelphoenix]

A "cool" way of measuring with superconductors, eh? I see what you did there..

[@SquirrelTheorist]

That's fascinating! Thank you!

[@D-train69]

@@nikolausluhrs it would detect single photons but for what??? A beam of light used to set alarms off, a laser of some sort, something emitting gfrom a computer or a navigation system for rockets, I just don't interstand???

[@Warhawk76]

I had a pretty good understanding of how this worked from my time working with lasers in the lab, but its still cool to see it demonstrated.

[@firefoxuser2557]

I’m studying QM in second year now, and yeah it’s cool to hear it in a different way and actually demonstrated too

[@Zeinzu2]

I don't normally learn a whole lot from videos like this (unless it's about the universe and existence haha), but coming from an audio background, I got so much wrong about frequencies of light and the energy of those colors. Super cool. I watched this like 3 times back to back. Awesome stuff!!!!!!!

[@DFPercush]

Be careful with green laser pointers in the cold. They can turn into infrared lasers and you won't know you're damaging your eyes if you try to peek into it. I always wondered how they can have instruments that can dial in a particular frequency of laser light. Neat.

[@alexnather7614]

Wow that's some important knowledge

[@Iwvclvz]

What does pointing in the cold even mean? “Cold” specifically. As the freezing cold ambient temperature?

[@ephjaymusic]

@@Iwvclvz cold/freezing weather - enough to lower the circuitry and diode ability EDIT *crystal ability* to output green light with a high enough level of efficiency to be visible. It can differ between laser pointers due to their construction and components/batteries etc.

[@rebelwind6474]

Isn't that infrared light has much less energy compared to visible light? Meaning that even if you did shine it in the eyes, it wouldn't really do much damage, so no. Also in terms of energy, visible light is much more dangerous Like in the video, you can go down the energy frequency path, not upward. If it's UV, X-ray and higher energy rays than yes it's much dangerous

[@ephjaymusic]

@@rebelwind6474 no. IR light is actually even more damaging when emitted from a high power in diode since you cannot see it and there is no blink reflex. You will be receiving a focused beam of IR which will burn the retina. Lower energy level in the context of light colour does not represent the power.

[@jt12blk]

Back in the early 1980’s a physics nerd buddy and I tried to grow our own ammonium di hydrogen phosphate crystal so we could create a blue led, since at the time the shortest wavelength of led was a mucky green color. We did not succeed; you need to pump quite a few photons into the crystal to get anything useful out.

[@belyndasonger7574]

I love this! My physical science kids will too!

[@sandipanganguly2219]

Taught more than my physics teacher, thanks!

[@BariumCobaltNitrog3n]

That meme sailed a long time ago. Your physics teacher is there to introduce you and pique your interest to physics and the world around you. It looks like they succeeded at all those things. You learned something new today? Don't blame your teacher.

[@fuckingdumbo]

i literally was searching on Google about this when vid showed up

[@Fire27hun]

What about the Kugelblitz black holes formed by high concentrations of light? It was a really interesting video, I love the passion you pour into your job making these videos, cheers!

[@tiffanyvalencia8415]

Yeah those are what demons suck your soul through once you've passed Einstein's level.

[@feynstein1004]

That still isn't light interacting with itself, but rather with spacetime, which then bends enough to trap the light. So kind of like an indirect interaction, not a direct one.

[@smokeduv]

What's also interesting is that it seems that the crystal acts differently depending on the temperature so, if the laser is used in low temperatures, the crystal seems to stop working and may lead you to think that the laser is not working anymore, but it is working properly... as an infrared laser, so if you heat it a little bit it will start glowing green again

[@vaakdemandante8772]

makes sense, as low temperature changes the crystalline structure in a way that prevents its resonant properties from working. Once the temperature raises and the crystalline lattice rearranges the photons are once again merged into one photon of summed frequency.

[@smokeduv]

@@vaakdemandante8772 well, one could say that your explanation was… coherent 😏

[@Zenodilodon]

Temperature changes the length of the resonator ( distance between HR and OC mirrors ) This changes the way photon match in their phasing while in the nonlinear medium. You can see on some lasers the beam will become bright and dim in repeating cycles as you warm up the resonator. Some crystals themselves do work best at a certain temp, but I have found that to be secondary to resonator length in most cases.

[@jasonkocher3513]

More of this please... awesome job.

[@catabc-rd8dy]

I love this channel because it always answers my questions.

[@JamesMulvale]

Absolutely fascinating!

[@chunfung8934]

Q: Does the 2 photons goes into the crystal have to be in sync (phase)? And does polarity matters? By the way, thanks for the video, it’s really interesting and keep me thinking. Thx 👍🏻😃

[@smo1165]

Phase and polarisation do matter for this process. To understand why and how you might want to look up the term „phase matching“.

[@silvenshadow]

This was really great. Thanks for the video!

[@charlestaylor3195]

To the point, easy to understand, and easy to remember. The best.

[@custos3249]

Ah, so this is how they've recently found a way to make solar panels more efficient. The channels that've mentioned it have never gone into deal about the process other than saying a vague "special layer able to change one wavelength of light into another the cell can absorb."

[@DFPercush]

Huh, I haven't heard of that. That's a... really good idea.

[@balazsszalai41]

I think they use quantum dot technology.

[@tiffanyvalencia8415]

@Custos About that layer...this video demonstrated that the non-linear crystal absorbed the infrared wavelength (which our 🌞sun🌞 is 👑king👑 of emission) and changing it into another, yet stronger wavelength...there ya go!

[@muhammedali8025]

6:22 To convert a single IR photon to visible light, what is it adding to? Is like half a photon adding to itself or something? Can you clarify?

[@Gameboygenius]

Rewind a bit. He talked about frequency summation, ie combining two wavelengths of light using a nonlinear crystal to create a third wavelength. So you combine photons of one wavelength (that you send an abundant amount of) with another (that you want to detect).

[@RexxSchneider]

@@Gameboygenius How is a single IR photon an "abundant amount"?

[@Gameboygenius]

@@RexxSchneider it's not. What's abundant is photons of another wavelength you add to "sensitize" the crystal.

[@ShenZhouGaiacoin]

this vid is amazing, I was thinking about a problem related with light, and out of nowhere youtube recommend your vid to me, as if youtube knew what I was thinking.

[@hosseynshanbehzaadeh9342]

You're amazing (the best I've seen by far) at visualizing things that haven't been yet observed, and are VERY hard to wrap your head around. Like your video about neutron star or condescended dark matter or 4d sphere et cetera. Could you do a video about visualizing a monopole? A theoretical magnet with just south or north pole. Thank you and lots of love from Iran ♥️

[@aakashanantharaman4037]

Great video. Could you do a video combining this with the photoelectric effect, where light can push objects but not other light?

[@zoldrin]

How does the harmonic doubling affect a single photon of infrared light? It seemed like at least two photons are required.

[@jpe1]

I came to the comments to ask the exact same question, so I’m commenting to get notification of any reply.

[@IC-lz3of]

I expect they use a light "base" (in addition to the single photons of infrared) then have a band pass filter to look for the base + infrared (not base + base).

[@zoldrin]

@@IC-lz3of thanks, that makes absolute sense

[@jamesn0va]

I'm not gonna say this is what's happening here but photons can interact with themselves ( double slit experiment ).

[@yourstoneruncle]

I find you through Snapchat shorts and I had to come find you on KZbin, you're so entertaining I wish my science teacher had been able to keep my focus like you can

[@daviddredge1178]

Another fantastic episode. Thank you.

[@RealNovgorod]

You can't convert a single photon of infrared into visible, that's simple conservation of energy! If you have a classical (Poissonian) light source and you wait long enough, you'll get 2 photons to coherently overlap once in a while to do the nonlinear frequency conversion. With an actual (non-Poissonian/anti-bunching) single-photon source that's impossible.

[@Elie-J-Saoud]

Conservation of energy?!!!! How about You double the frequency and decrease the ampiltude by 4?!!!!

[@RealNovgorod]

@@Elie-J-Saoud Can't reduce the amplitude of a photon, buddy. That's kind of the point of that whole quantum stuff.

[@alexandermarsteller7848]

I imagine you would use a high intensity probe laser and do the frequency summation mentioned. You should get out a single photon of source+probe frequency which you can then separate from the probe & doubled probe photons.

[@RealNovgorod]

@@alexandermarsteller7848 Yeah, that's called OPA (the high-intensity laser is called pump, not probe) and that's not at all what he was talking about. He talked about spontaneous sum-frequency generation (i.e. second-harmonic generation) without any additional pump source where infrared turns into visible light all by itself in a nonlinear crystal. That doesn't work with a single photon.

[@adrianyong4640]

Science would be fun if you were my teacher

[@Bela12351]

This was amazing! Thank you for the video.

[@jcjcortz8526]

Just thought about this thing and found out that this channel actually has something to say. I never regret I subscribed "The Action Lab". Thank you so much❤.

[@prich0382]

Wait if you can double the frequency, does that mean putting loads of them in a row you can keep going higher and higher with the frequency? Or is there a limit?

[@aura4977]

gamma rays may be the last know checkpoint to increasing it? idk what comes after that

[@prich0382]

@@aura4977 Well I did a little s arch and apparently frequency has no lower and upper limit, they go on forever either way getting closer to zero Hz and going higher and higher forever

[@ngotranhoanhson5987]

@@prich0382 i think about it too, hope this dude will make a video of it, gamma rays is something fun to play with

[@wally7856]

@@prich0382 You can't go higher and higher in frequency forever. The energy of a photon is proportional to its frequency, so as you go higher you would eventually have enough energy in a single photon to create a black hole so that would be a limit. Also, as you go higher in frequency, the wavelength would get shorter and shorter and eventually the wavelength would approach the Planck length so you couldn't go any higher. That's 2 upper limits you would reach.

[@mbrusyda9437]

They can only double a specific frequency, most probably

[@Jared7873]

What happens if you aim 2 identical laser beams into a non-linear crystal 🔮? Will they annihilate each other & dissappear?

[@RyanBoggs]

I think the implication in this video was that this is how frequency doubling occurs. Im guessing that the green laser is taking two infrared photons to make one green photon. So if you aim two lasers into the same crystal, maybe you get the sum of the frequencies of the two.

[@Ashwanth]

That depends upon various factors.

[@EduardRitok]

that experiment with crystal in the laser was cool!! 😳 to see the actual transformation from infrared to bright visible green

[@briancannard7335]

This is the coolest shit I saw in my entire life in physics demonstrations. This thing explains everything. You just showed a working perpetuum mobile of the 2nd kind.

[@drivera0502]

I work in an imaging lab and second harmonic generation is pretty common in collagen. We also see 3rd harmonic generation (3 photons coming together) in brain white matter

[@rayoflight62]

The photosynthesis in every plant produce red light as product of the photochemical reaction. This red light coming off any plant leaf can't be seen with the naked eye, because photosynthesis occurs only when the sun is shining. As the sunlight is much more intense than the red light emitted by the leafs, you can only see the latter if you use a spectrometer or some filters...

[@DANGJOS]

@@rayoflight62 Are you referring to the red light fluorescence? I have seen that

[@tiffanyvalencia8415]

@Daniel Rivera what you commented is courtesy of our fascia and nervous tissue, which permeate every part of our bodies and create, emit, communicate, and store light 👍

[@tiffanyvalencia8415]

@@rayoflight62 I use red lights at night if vision is necessary, which makes my plant leaves under it appear a dark greyish-brown, relative to your comment.

[@maxfofax5471]

In general, you get THG microscopy signal anytime you have a refractive index boundary or large X3 boundary which is less than the wavelength of light, or are focusing in birefringent crystals at the right polarization. You also get great SHG from natural cellulose.

[@yeet1337]

Optical light does not, in fact, split up into electrons and positrons spontaneously. The effect is called pair production and can only occur if the photon has an energy bigger than 1022 keV (rest mass energy 511 keV * 2 for both particles), which is nowhere close to the optical spectrum. This is, however, very common with high-energy gamma rays.

[@Impatient_Ape]

Yes, and even when it happens, it requires the presence of a third particle --usually a nucleus.

[@TheActionLab]

Yes, below 1MeV though they can decay into neutrino/antineutrinos as well. But you are right, for visible light, it needs to occur in the non-linear crystals. The non linear crystal provides a setting in which the driver, signal, and idler modes can interact.

[@yeet1337]

@@TheActionLab Photons can decay into neutrino pairs? Never heard of that, can you tell me the name of the effect or some source?

[@RealNovgorod]

That is not entirely true. Even visible-light photons can spontaneously decay into _virtual_ e+/e- pairs as long as they annihilate back into photons within the uncertainty time corresponding to the "borrowed" energy (another way to see it is that within that short time the photons have a huge energy uncertainty such that it's enough for pair creation with finite probability). That happens all the time even with vacuum energy fluctuations and it's the mechanism behind (e.g.) the Casimir effect or Hawking radiation. That said, "vacuum polarization" becomes an actual thing in ultra-hyper-super-strong-field physics, think of EW/cm² (or maybe even ZW) monster lasers like for inertial ignition. If you have mind-boggling densities of low-energy (visible/IR) photons, the probability of virtual pair creation becomes high enough to provide the necessary nonlinear susceptibility for _actual_ pair creation where a million photons simultaneously decide to become an e+/e- pair from now on. It's left as an exercise to the reader to calculate the corresponding chi(1000000) susceptibility tensor...

[@TheActionLab]

@@RealNovgorod great point

[@aharris206]

I was actually shining my green laser pointer around when I saw you take it out at the beginning of the video :3

[@omsingharjit]

It's something that i already new about.. And i like this field of optic and non linner effect because it can do Quantum Entanglement and same technology also used in Frequency mixing in radio and Wireless.

[@briancannard7335]

Let's build a working time machine prototype then? I'm serious.

[@MlorenDraymeer]

If you kept stacking more of these crystals in front of the laser, would it go up even higher through the frequencies?

[@alunjones3860]

The crystal only works over a narrow bandwidth, so each crystal will need to be designed to work at the higher frequency and there will be a limit to the maximum energy any material can handle. High energy x-rays can damage crystals.

[@Onyx-0.01]

I wonder if it's possible for this same scenario to happen with sound

[@fellipec]

Today I learned something very cool, thank you!

[@HelloKittyFanMan.]

Oh wow, this was amazing! Thanks, James!

[@underseer]

What would happen if you shined green light on the glowing paper thing?

[@Pseudify]

I assume it would depend on the exact incoming frequency and the exact frequency that the paper is designed to emit. As long as the incoming frequency is higher then it would probably glow. Just a guess though. I’m not a physicist.

[@underseer]

@@Pseudify Yeah, I thought so too..

[@BogdanZB]

What if I combine two ultriviolet light sources into one with crystal? What type of light will I obtain?

[@cienciabit]

Or a second crystal after the green laser?

[@55Ramius]

Cool. Never knew about this. Hope you never run out of great ideas like this in future videos. : )

[@TomJones-tx7pb]

wow this video is exactly what I have been wondering about for ages but never bothered to find the answer. I enjoyed this video immensely.

[@jpietersen519]

At 6:25, if the crystal needs 'two' photons/light sources to double their frequency, how could it be used to detect a single photon? I understand there's probably some particle/wave distinction here, but I am struggling to translate the diagram of two lightwaves entering to a single photon, unless the two waves were never required

[@shedactivist]

The 'single' source of light your thinking of is actually a stream of photons, so two photons in the stream get diverted in the crystal and collide with each other.

[@bluesillybeard]

I think they have a constant source of photons, and when the second one comes it adds with one from the continuous source to make the visible light

[@jpietersen519]

@@shedactivist but then how could you detect a single photon?

[@shedactivist]

@@jpietersen519 You don't need to detect a single photon pair to see what is going on. That's where the theoretical scientists corroborate their work with the experimental scientists.

[@iPsychlops]

What you're talking about with harmonic frequencies and frequency summation is super cool. Just got my amateur radio (ham) license and learned during the process about radio waves doing that, and how it can lead to RF interference. All waves behave the same!

[@aghanasir78]

I will forever be grateful of you to answer questions that everyone wonders but no one answers. I have wondered this thrice when I was reading the light chapter in my 8th grade book

[@tthtlc]

Finally I had a beginner's intuitive introduction to Feynman Diagram, thank you very much.

[@Alvin-eq5rc]

Great video mate! Easy to understand and learned something. Never knew laser pointer uses inferred

[@wilbur9416]

Something that I found very interesting is WDM. Wave division multiplexing. cool video

[@4corander]

Very informative!

[@souls2music567]

Thanks for this wonderful video..

[@MrMcp76]

Whoa, I had to watch this twice to understand it! My coffee hadn't kicked in yet through the first viewing lol!!! Great video!

[@grantyentis5507]

My favorite lab is The Action Lab!

[@h-leath6339]

Dude. So cool. Thanks for what you do!

[@Treksh]

Such a cool topic

[@supremeleader69]

That was actually very informative.

[@flyfin108]

very much thought provoking, thank you

[@swiddle1]

Fascinating!

[@Hossak]

Thank you very much, I have wondered if photons can interact with each other. That crystal transformation to green light was awesome!

[@flaviospedalieri8707]

An important point to keep in mind with Non-linear interactions such as frequency-doubling of laser light, is the energy loss in the conversion is very high. The laser you have used in the demonstration, more accurately, a Diode-Pumped Solid-State laser uses a Diode pump laser of 808nm and typically its output energy is anywhere between 0.5W upto even several Watts of optical energy. In-turn, this pumps a solid-state laser, a Neodymium-doped yttrium orthovanadate (Nd:YVO4) crystal to produce the 1064nm 'fundamental' frequency. Nd:YVO4 is more efficient that Nd:YAG for smaller pump powers. The Non-Linear crystal is typically a Potassium Titanyl Phosphate (KTP) crystal, however there are a number of crystals that exhibit non-linear properties as well. With a pump laser of say 1W, your final output will be several mW of green 532nm light. Most of the optical energy is used in to Pump the Laser Crystal and then the second harmonic generation of the 532nm light.

[@dexterman6361]

Holy shit underrated video! Thanks!

[@ciphermatrix]

Still the best channel on youtube for science explanations and practical experiments.

[@the_crusader_8883]

Finally, a video covering what I was thinking about in 2021

[@RomanoPRODUCTION]

thank you James, it is beautiful

[@cranegantry868]

Amazing. I understood lots in a short time.

[@thelovertunisia]

Amazing. Well made video

[@Heartless44-_-]

Ok, how the? You just gave the info I needed for a special project I’m working on. Ty!

[@IScreamAtCats33]

love how at the end he just drops that this works for a single photon, which is pretty crazy in and of itself

[@SinisterBlackShadow]

Dang, that was interesting 🤔. Thanks for the video upload!

[@sithlordbilly4206]

Awesome dude! ✌

[@dmitryfalkovich833]

finally i found a simple explanation of the type of harmonic conversion i do at work, the physicists just couldn't explain it

[@SorLord]

You literally make KZbin a better place.

[@electronash]

Great vid, as always. I learn something new every time. But, I want to point out one small thing (using my best nerd voice)... They do now have so-called "Direct Injection" Green laser diodes that don't require the crystal(s). They are becoming far more widespread now, and available with higher output powers. That's quite a recent development, though. It was also only about 10 years ago that we started seeing high-power BLUE laser diodes without the crystals, too.

[@sfb-wi9pn]

I had this question for a long time. Finally an answer

[@gnorts_mr_alien]

amazing content as always.

[@artdonovandesign]

Great video, Did we just see purple laser light @ 6:09 ? And BTW: You wrecked the futuristic dreams of all Star Wars fans (a heartfelt thank you for that)

[@jer103]

I would have loved to have him as my high school science teacher.

[@craftysun]

love your vids

[@jamesT008]

Ur gem...nice detailing...good info

[@marcfruchtman9473]

Very interesting!

[@LeSpulch]

Just as you think you're starting to understand how light works, someone comes along a tells you why you don't, I love this!

[@monstruonegro05]

Nice one!

[@elliotmapp-best9990]

Brilliant...I loved it

[@Toobula]

Gee, you're a spectacular explainer, James. Perhaps one day you might do a video about the forest fire modelling that you did at BYU?

[@RickSjoerds]

Did not know this! Cool!

[@drsamuelk]

This was mind boggling superb

[@rajibalam9748]

Wonderful!!

[@garyha2650]

That has some up and down top to bottom strange quarky charm Mr Higgs

[@depressedknight369]

love you... keep it up.. ✌️

[@solapowsj25]

Thanks🌹 God bless you.

[@juanluisclaure6485]

Gracias por tanto. saludos from Bolivia

[@josefaction6982]

thats amazing!!!

[@RUTired]

Napoleon: "hold on, I forgot to put in the crystals."

[@smile768]

Amazing!

[@crysikosden]

MIND BLOWN