Light sucking flames look like magic

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7:40 Hey! There's a legit use case for that! People who live near sodium public lighting might want their windows tinted like that, so their room is dark during the night but then in the morning (most) sunlight will filter through and help them gradually wake up!

Now someone can make the REAL Darksaber!

I see this flame and the first thing that comes to mind is the Godskin Cult.

15:22 is something that I didn't expect to see, but I was glad it was there.

I don't know whether it's the quality of your pedagogy or if we just happen to think alike but whenever I have questions while watching one of your videos you inevitably say, "You might be wondering..." and then answer those questions. It makes your content extremely satisfying to watch. The downside is that since I'm left with no outstanding questions I rarely comment, hurting that elusive "engagement" metric. So here's me making up for that.

When I was learning electronics in the Navy, we used to joke that DS label used for lights in a circuit diagram stood for Dark Sucker. When a bulb blows, all the dark leaks out.

So, this is the secret behind Itachi's Amaterasu.

Here in Sweden, I miss the highway sodium lights upon startup (I remember them shifting from purple/blue/yellow/deep red/orange to the final yellow light). A late summer evening with a clear, rather dark sky, seeing the sodiums start up into the distance... awesome.

2:30 I like how your camera can't even remotely pick up on the actual rainbow in that diffraction grating, and just gives you three bands of RGB.

i have struggled with "Spin" of subatomic particles for years. The "it tells us which way the moving electric charge points its magnetic field" line felt like an epiphany i have waited decades for

Wow, came here for a black flame (which I knew would be about sodium absorption lines) and learned about glass blowing, colour blindness and - finally - a good explanation of an electron spin.

I saw a misconception in this video which keeps getting spread, mainly because the actual explanation is a lot trickier and weirder to understand than the actual reasoning. In the video, Steve says that the reason there are two lines is because the electron spins are either in the same direction or different direction from the orbital angular momentum. But, this is not true. Rather, it is because of statistics and the Pauli exclusion principle. The Pauli exclusion principle says that an electron cannot be in the same quantum state as other particles. As it turns out, there are 4 different options for spin orientation: both spinning in the same direction upwards, both spinning in the same direction downwards, one spin up and the other spin down, and then vice versa. We then write these as a math statement. The first one is written as ↑↑, the second is ↓↓, the third is ↑↓, and the last is ↓↑. HOWEVER, as it turns out, ↑↓ and ↓↑ are not actual "good" states. For those who this word means something to, they aren't eigenvectors of a 2x2 matrix -- which is necessary for a state to be physically possible. So the solution is to change the set of states we work with to: {↑↑, ↓↓, ↑↓+↓↑, ↑↓-↓↑}. This is the set of all possible spin states. Now onto the Pauli exclusion principle. Because an electron is a "fermion," when you swap two electrons, all that should change is the overall quantum function -- the thing which describes the electron -- should have a negative sign. Let s be the spin state, and p be the rest of the function -- describing which orbital the electron is in. We write that the whole function P is a function of particle 1 and 2, written as P(1,2) and equaling s(1,2)*p(1,2). In other words, P(1,2)=s(1,2)*p(1,2), with * just meaning multiplication. The "fermion" statement I made means P(2,1) = -P(1,2). So, s(2,1)*p(2,1) = -s(1,2)*p(1,2). Now, we will look at each of the spin states. Note that when you swap the order of the first three spin states, we get ↑↑, ↓↓, ↓↑+↑↓. The last is identical to ↑↓+↓↑ because you can swap the order of addition. HOWEVER, the last state becomes ↓↑-↑↓ = -(↑↓-↓↑). This means if the particle is in the first three states, then we have to say p(2,1) = -p(1,2), and if the particle is in the last state, p(2,1) = p(1,2). This property is what causes the electron to have different energy levels. If the particle has the first property p(2,1) = -p(1,2), the particles tend to be repelled away from each other, and we say that the position function has a "fermionic" behavior. In fact, THIS is why solids are solid. It's not that there are electromagnetic forces repelling electrons from electrons. Rather, it's because of this fermionic behavior of matter. Neutrons do the SAME exact thing, which is why neutron stars are a thing. They are held together and kept from collapsing by this pressure called "degeneracy pressure," despite having a neutral charge. If a particle has the second property, p(2,1) = p(1,2), the particles tend to be attracted towards each other, and we say that the position function has a "bosonic" behavior. Light is a boson. A bosonic particle tends to be attracted to other of the same type. I will make an important distinction: the repulsion of fermions and the attraction of bosons ONLY happens because the particles are EXACTLY the same. All electrons are 100% completely indistinguishable, there is no way to know for 100% certain one electron is not another electron or one photon is not another photon. Fermions are ONLY repelled from other fermions for which they are 100% absolutely identical to, and bosons are ONLY repelled from other bosons they are 100% absolutely identical to. Protons, neutrons, and electrons, for example, are not repelled from each other by this degeneracy pressure. FINALLY we can get into why the energy levels are different. If they are in the fermionic position state, we call this state the "triplet" state, and the position function needs to be of a higher energy because of the degeneracy pressure pushing the electron further away. And, if they are in the bosonic position function, we call this state the "singlet" state, and the position function needs to be of a lower energy level. Now, I will admit, I feel like there is something slightly wrong here. I believe an important statement is I need to say magnetic fields show up someplace in here because iirc, splitting of the singlet and triplet state don't occur unless if there is a magnetic field. Iirc, this magnetic field is due to the nucleus's spin (?). I am willing to correct myself if I made any mistakes. At the very least, the misconception which keeps getting spread is that objects are solid because of electromagnetism, which isn't true; it's because of spin statistics.

Someone else may have already commented about this, but the fact that the light emitted by sodium atoms produces roughly one wavelength of visible light was used in movies for compositing in lieu of greenscreen. This technique known as "Sodium Vapor Process" or informally "Yellow screen" utilized custom-made beam-splitter prisms with embedded notch filters (similar to how EnMouldia glasses work) and Bandpass filters split the image into two parts to create a perfect matte. This process was famously used by Disney in the filming of Bed knobs and Broomsticks as well as Mary Poppins.

16:12 From one uncle to another, this is top notch uncling giving your nephew's YouTube a shoutout. Bravo.

This video is amazing. Your casual explanation of spin to get to the why of the double lines emmiting form sodium was marvelous, I love when I get answers to questions I didn't know I have. And I'm totally using that orbit analogy to explain this. Thx for your content, cheers Steve

Thanks for all the neat videos over the years Steve!

A fun fact about the sodium light spectrum is Disney created a special process back in the day that worked better than any blue/green screen using a prism. They could get much more detail around a subject without any spill from the screens as well as being able to film sheer & transparent materials. Marry Poppins is the best example of this. The Corridor channel did an interesting deep dive and recreated the effect on one of their channels.

"because id be dead" got me spitting out water lmao

Very nicely done, good explanation of subatomic photon production (and absorption). As a theoretical concept, I had thought about "dark light", but had never seen an example of such as being demonstrated via a black flame. Of course, there are well known examples of "invisible" flames (partially a function of the flame temp, and the relative energy levels of the electron orbits), a terrifying example of which is the methanol fuel used in race cars. It has happened when a driver is being burned with a flame no one can see, but the process of being burned becomes extremely apparent.