33 years old french scientist here. Just enjoying my last years of this earth with those great videos.

"I'm so afraid of magnets." That's smart. Magnets move on their own and feel no remorse. I'm terrified of the big ole magnets I work with.

Galios, one of the biggest deal Mathematicians of all time: 1) was french 2) died at 19

Angela flexing on us with a $700-$800 Faraday Rotator she just casually keeps in her house while also saying "I'm not an experimentalist." Love it.

If John Green has taught me anything, it's that everything is tuberculosis

Angela: "Don't judge my books." Me: "Of course Angela owns Maus and Persepolis, because they're awesome and she's awesome."

Obviously, it was Skynet that send back terminators in time to make sure French physicists would die neither too early nor too late in order to bring about its existence. One bad sequel after another. And some getting in each other's way. On a more serious note, doing the quantum computations to get the same constant we have already measured is actually good work. It's something that should be doable and it just proves the validity of quantum mechanics a bit more.

10/10 no notes on your character analysis of Napoleon in Egypt.

The faraday effect in the atmosphere is actually extremely critical to long-range (non-line-of-sight) radio propagation. Not only does it randomly polarize shortwave-and-lower radio waves so that horizontal antennas can communicate with vertical antennas, the rotation plays a key role in those radio waves bouncing off the ionosphere instead of going straight through into space. Without it, over-the-horizon radio communication would be nearly impossible. There's some minor effects you can use to get some frequencies of RF to 'hug' the earth a bit to reach a short distance around the Earth, but when the sunspot cycle is at a peak, a lot of frequencies will propagate around the earth multiple times.

"I'm so scared of magnets." - A.C. Me looking at my healing bruise from two neodymium magnets being put too close together, with my hand in between: "I can relate."

Faraday invented a precursor of the Bunsen Burner, so I think he used something very similar to a proper Bunsen Burner, of Faraday's own invention. Because he's just that cool.

When they were doing the old-timey experiment, all I could think was my optometrist's voice asking, "Is it polarized through one....or two?"

If it moves, it's biology. If it smells, it's chemistry. If it doesn't work, it's physics.

Michael Faraday spent five years making optical glass, and if he hadn't quit that to experiment with electricity he would have probably died of heavy metal poisoning like everyone else who was experimenting with glass ingredients at the time. Although, he did have a nervous breakdown a few years after he quit experimenting with the heavy metals. He was almost killed making explosives for Humphrey Davy too.

I find it astounding that people back then even considered the idea that light and electromagnetism were connected, given that in our everyday experience, light couldn't seem to care less about magnets.

Can't wait until someone comes up with the faranight effect

I'm a ecologist, so all the quantum quantum quantum goes over my head, but I appreciated the visual demonstration of all the ways a faraday experiment can go wrong

Having taken a minor in physics (while studying math) lo these many years ago, and having had to re-create the Cavendish Experiment, I have the utmost respect for experimental physicists. The attention to detail required to get accurate measurements is terrifying.

Hi Angela, I'm Steve from Adelaide, South Australia. I've been on leave from work and only discovered your channel a week or so ago. Thank you, thank you. I'm not a scientist of any persuasion but wish I was. I've watched as many of your videos as I could and while your knowledge is lightyears beyond mine I've always loved science and it's method. Your humour, knowledge and humble approach is wonderful to watch. Sincerely, Steve.

“and now we have the internet” It amazes me just how many different fields of study end up here.

Its not only physicist its also mathematicians doing algebra which dies in France. Galois and Abel both died in France around that time.

There's a famous unsolved mystery in history where the French population growth mysteriously slowed in the 1800s and historians don't know why. Not saying that's related to your mystery about French physicists coincidentally dying young, but I think it's interesting.

We use Fresnel constantly in game dev - it’s incredibly useful for faking things like rim lighting, ghost effects, or masking the fresnel angle of an object to create some effect that avoids the boundary angle from the camera. Love that guy. Games would not look the same without him.

Old timey light source-- starting in late 18th century there were oil lamps with tubular wicks with springs to keep them at the right height and pressurised oil wells, they burned brighter and more consistently than candles. Scotland was home of Europe's best medical universities in the 19th century... whereas France was rocked by ongoing revolutions/civil wars through the century. 19th century life expectancy in general was probably lower in France vs Britain. fwiw. I don't have stats off the top of my head.

One cool property of the Faraday effect, which leads to the Faraday Isolator, is that the direction of polarization rotation is independent of the direction the light is travelling through it, unlike a quartz crystal rotator, which rotates the polarization CW from one direction and CCW from the other. So, you arrange your polarizing filters, quartz rotators and Faraday rotator such that, in one direction, the polarization is rotated 45 degrees by the Faraday rotator, and then undo that rotation with the quartz crystal rotator (0 +45 -45 = 0). In the opposite direction, the polarization will be rotated by 45 degrees twice, and will get rejected by the filter, or polarizing beam cube at the input (0 + 45 +45 = 90). The design I'm most familiar with consists of a Polarizing Beam Cube | Faraday Rotator | Quartz Crystal Rotator | Polarizing Beam Cube. P-polarized light passes through the first cube polarizer, is rotated +45 degrees by the Faraday Rotator, -45 degrees by the Quartz Crystal Rotator, and passes through through the second cube. In the opposite direction, P-polarized light passes through the Cube Polarizer, is rotated +45 degrees by the Quartz Rotator, +45 degrees by the Faraday Rotator (making it S-polarized) and it is rejected by the Cube Polarizer on the input side, into a beam dump.

28:08 For what it's worth, Faraday Rotators can used on high power laser systems to prevent damage from back reflections. The big laser facilities are built such that in order to keep the beam power low enough to not destroy the opics, the laser beam is made wider, then it's amplified, then it's made wider, then it's amplified again.... however, if the laser light reflects off whatever you're shooting and goes back down the laser chain, it gets amplified, then made narrower (focussed down), then amplified again... and so on until you've blown up the amplifiers on your multi million pound laser system 🙃

If you remember "floptical" disks (like the LS-120 Superdisk) from the 1990's, those used the Fariday effect to read the bits off the disk. The laser head would measure the polarization angle of the reflected light to determine the orientation of the magnetic field on that spot of the (plastic) disk surface.

My 8-year old son's really into puns right now, and he wants you to know that "a FAR A DAY keeps the crushing experimental failure away."

Mantis shrimp are able to use circularly polarized light for communication, which is pretty neat.

the best aspect of these videos are the history and historical context. they are important and essentially everything else can be self-taught, but the history of a science is almost oral tradition passed down through professors and teachers. Few outsiders know much about this aloof tribe because they do not appreciate etic study of their culture.

I'm happy to announce that my girlfriend has been converted to "that sassy science woman" as she puts it and now watches your videos with me

TIL that Egypt threw a shoe at Napoleon.

I’m currently waiting to hear back about my PhD applications for experimental cosmology programs and watching you do you best with the optical table and then admit “I’m not an experimental physicist” cracked me up so much. Another great video as always!

5 min in and I already have answers to polarization questions I've had for years! Amazing content

Great video, Angela! Another important reason we use Faraday Rotators to prevent back reflections is that we don't want back propagation within the laser's cavity, because it can cause all sorts of undesired effects on the laser's gain medium.

At the time I think the Rosetta Stone had just been discovered and their was a race between England and France to see who could decode Egyptian Hyrogliphics. That meanappropriating and pillaging as much Egyptian cultural artifacts as possible. There were a lot of French soldiers in Egypt at that time, and disease ran rampant.

I really like the idea of Faraday shining a laser through electromagnet (at 11:40). It shows how old I am. When I studied physics lasers were already used a lot but they still had the glamor of a new invention about them.

If I had a nickel for every time a French physicist who made great strides in the field of optics died tragically young in their 30s from disease, I'd have 2 nickels. Which isn't a lot but it's weird that it happened twice.

Came over after hearing about your channel from Professor Dave. And now I've got a link to old-timer experiments. The rabbit hole deepens. And it's awesome. I also love that you're ready to put yourself out there and show the failed experiment, because learning from failure is something we should expect and learn to appreciate.

I worked in a thin film PV manufacturing facility as an engineer for about 3 years. We actually measured the thickness of our films using thin film interference. From the light that was emitted on the PV, some would reflect off of the film, and some would refract through the film and reflect off of the glass underneath the film. By measuring the difference in the two reflected beams, we were able to measure within a precision of 0.1 microns (the film was only ~3 microns in thickness)

Your comments about solving for Verdun's constant from a quantum basis reminded me of how empirical electromagnetism was done before we understood the structure of matter. There are theorems that show that as long as the "macroscopic" fields are small compared to the internal binding energies of the parts (atoms and molecules, natch), assuming a linear response to the fields will do just about everything you need. You can then "renormalize" the vacuum wave equations with tweaked, empirical constants with effectively no knowledge of the fiddly details. This got science an absurdly long way before we began understanding the fiddly details. And note that it is an approximation. Crank up the electric (or even more difficult, the magnetic) fields enough and the technique fails. Still awful cool though. And it meant that experimentalists were able generalize from light in air to light in a vacuum with little effort - so useful.

only 1 min old and already 6 downvotes. Peeps must have have STONG opinions about Faraday.

New microphone?

I remember this! In Cosmos the show with Neil Degrasse Tyson he mentioned that people who worked in optics and therefore glass often worked in puddling furnaces that gave off toxic fumes that would shorten lifespans. This may be the case with opticians.

omg babe wake up new dr. collier just dropped

I got a good chuckle out your total hopelessness during the "Experiment" at the end of the video.

The Rumford medal is named after Benjamin Thompson, an American born scientist who became Count Rumford in Europe. Thompson/Rumford's story deserves its own video.

I just read that the glass Faraday used to discover this was *_one third lead oxide_* (one third silica, and one third boricic acid). I don't know if these propotions are molar ratios, or volume ratios. Previously, I said magneti-optical disks (like the Minidisc) used the Faraday effect, but I was wrong, they use the closely related Kerr effect. Transmission through a transparent media is the Faraday effect, and reflection off a magnetic surface is the Kerr effect.

I actually used this effect on a research project in undergrad to try to measure the magnetic fields of galaxies [we didn't have the resolution in the end, but w/e]. Basic premise was to look at a polarized source behind the galaxy, and use the wavelength-dependence to determine the (integrated) strength of the magnetic field (along line of sight) despite not knowing the original polarization. That way we could determine at least the overall direction of the magnetic field relative to the rotation of the galaxy (which, perhaps surprisingly, isn't known). [This was radio data, so the wavelengths were long enough that effects were measurable.] The wavelength dependence is that angle is proportional to wavelength squared, so the traditional way to do this is to fit a plot of angle vs. wavelength squared, assuming a single source. But we were trying a new technique, "rotation measure synthesis," which basically extracts the light emitted at each "Faraday depth" (magnetic field times length) using the fact that (1) rotations in 2D can be complex phases, (2) using that phase as part of an integrand Faraday depth and wavelength squared are dual under a Fourier transform, and (3) Fourier transforms are invertible [with some technical caveats, both the usual ones about finite data and the fact that wavelength squared is always positive]. Very neat idea; I don't know if they've tried to do it since (I left the project back in 2015 or so, and completely lost track since 2017 when I graduated).

the reduced power of 3 filters is not always reduced by a power of 8: the transmitted intensity through all three polarizers is equal to the initial intensity (I0) multiplied by the cosines of the angles between each successive polarizer, Angela Rocks!!!! and I have to thank her for making me ponder this aspect of physics. Gr8! Peace ☮💜

You described Faraday as a “top-tier physicist”; I think everyone will agree we would love a physicist tier list video.

My colloquium for my second year undergraduate lab experiment which is on polarization is in two days. Thanks for the introduction to polarization!!!

Love the video, some of the most informative science I've seen in years, and the history lessons are fun to boot. Even the parts where you slip up or are unsure are charming in their own right. It's honestly very refreshing to see that experimental side of things, and to see a real and relatable reminder that this stuff is complicated, confusing, and that demonstrating it can be hard. Too much of what we have available to us today feels alienating in how refined and perfect the end results present themselves. It seems easy to feel inadequate in the face of all our collective discoveries, and the painstaking efforts of those with the resources and facilities to consistently reproduce their effects, especially when we only ever see the finished products for demonstration.

Riemann died of tbc at 39 too in Germany

It's always a pleasure to see a video of yours Dr. C!

Ive been a lurker on your channel for awhile. I really enjoy your vids, and sense of humor, thank you!

I kinda dozed off cuz I was tired but if it wasn’t mentioned, polarized light is how modern 3d movies work. Each eye lens filters a different direction of polarized light and the movie is played quickly alternating between two different types of polarized light.

Your videos are the best! Polarized goggles & sunglasses for snowboarding, polarized filters for my cameras (which are so cool because they have 2 pieces, the outer one rotates & one rotates it to be able to eliminate reflected light from glass or water so as to to see what's on the other side of the glass or water & it also makes the sky incredibly beautifully blue) & I've always wondered about the physics of how that works. I never ever looked it up because I had a feeling that eventually the answer would reveal itself to me. And through you, Angela, it has. And I thank you so very much for that. Again, I think your videos are absolutely wonderful and I cannot thank you enough!

I don't know if this will soften your dislike of "corpuscle", but it's pronounced like "muscle".

"Whatever, it's fine" is definetely catching on as a catchphrase.

Holy cow, the chapters and notes! That’s gotta be a lot of work. Thank you for including that.

Yes! More demos please! They are fun to watch, and give a more visceral understanding.

The part at the end trying to manually hold a laser and also a laser in water has big "Slotin's screwdriver" vibes. Being scared was a very reasonable feeling!

I'm glad you swung to the right in your shot, it was bugging me the whole time whether or not that black book with the red band was Just My Type or not. Also, I'd read Maus before, but I finally picked up both at a sale recently and it's a delight to revisit. Maybe "delight" sounds strange for the content, but you know what I mean.

Finally! Been waiting so long for some acollier astro! 🌠🔥

Your physics knowledge is impressive but it’s your honesty and passion that brings me back for more.

Ok maybe it wasn’t the most polished physics demo, but I thought it was really cool and would love to see more in future vids!

Great video! Love the experimental demo, always enjoy revisiting physics with your insight and humor. Someday i will understand these electro-magic waves 😊

I love that you incorporate the history of science and don't just explain how things work.

It turns out that although mantis shrimp actually can't see many more colours than we can they _can_ see UV and circularly polarized light which is pretty cool.

"What is going on" in early 19th century France is best answered with a sad look and a puff of smoke.

13:23 - "minuscule but indistinguishable" Did you mean "distinguishable" ? cause otherwise that just does not make sense to me.

What a perfect time for this video to drop, the semester just started and I’m taking a lasers class as one of my major electives

I would honestly love a series of videos that are just failed attempts to recreate old timey physics experiments, ultimately concluding that physics is just kinda hard, and people shouldn't underestimate the brilliance of the people who get laws, constants, and formulas named after them.

This one was oddly soothing and I almost fell asleep. Maybe I will rewatch it tomorrow.

this experiment was the first experiments that really excited me and blew me away during my grad school photonics course. since then I've been obsessed with photons and things like fiber optic gyroscopes. physics is cool :)

during your digression about Faraday's light source, I recalled that he lived during the heyday of limelight. now, im saying he used limelight to stare directly into - it is intensely bright - BUT, wikipedia does give this tidbit: "The limelight effect was discovered in the 1820s by Goldsworthy Gurney,[4][5] based on his work with the "oxy-hydrogen blowpipe", credit for which is normally given to Robert Hare. In 1825, a Scottish engineer, Thomas Drummond (1797-1840), saw a demonstration of the effect by Michael Faraday[6] and realized that the light would be useful for surveying [...]"

Hey Angela! I love your videos so much. You're very good at explaining advanced topics and that has been very helpful for my self studies! I would love to see you make a video talking about degenerate stars and degeneracy pressure! Thanks again for the awesome video

Yoooo I noticed and appreciated the increased audio quality this episode

Was not expecting a collab video with Sir Lawrence Bragg

I barely understand any (read: none) of that, but your excitement/tendency to jump between unrelated thoughts made my ADHD brain very happy XD. Prob gonna go rewatch the video tho to make sure I actually understood at least some of it.

OMG, the audio is glorious! New mic day? Congrats!

Not a historian, but a small glimpse at France: Firstly, the 19th century is sometimes called the long 19th century in European history. That's because some mayor things happened right before and after and it makes less sense to put down a border in the 00s when the social consequences were still ongoing. We have the French Revolution in 1787 which lasted until 1799. First this went after gentry and royals, especially 1789, but then the whole thing turned into the Reign of Terror over time and it wasn't fun for anyone. At the end of this everyone was fighting, specifically the French Revolutionary Wars, which are 2 wars 1792-1797 and 1798-1802. After that was done, all of Europe had the Napoleonic wars 1803-1815. They are called this because Napoleon was beating up absolutely everyone up instead of French infighting. This included Britain and conquering significant pieces of the whole continent like Germany, Austria, parts of Italy, Spain and Portugal. Then he made the mistake of trying to invade Russia during winter and got beat up on the way back by a multinational coalition. They exiled him twice, once after he escaped the first one. Now idk if scientist got drafted during that time, but they had an absolute outbreak of typhus on the way home and brought that back home. Now, after the beheading of the French royals, every other monarch in Europe was shook, because if peasants can behead one, they can behead the others too. They agreed that things should be put back as before, more or less. That whole debate was called the Congress of Vienna since they met there for a year. France lost some territory from that. As you can guess, the nobles weren't really making things easier on the poor. (The British have had mainly the plus of no longer blockading France by sea and fighting in wars, so everyone young with enough money started traveling Europe again. "The Grand Tour" is the reason why you have Mary Shelley hanging out with Byron in Switzerland when she wrote Frankenstein. That and the volcano. Also absolutely a regency thing, especially since you had steam trains getting started, making everything faster and safer.) Anyway, so the poor weren't really happy to have the pre-revolution bs back when a new king took the crown in 1824, so you had the July Revolution in 1830. (This is the setting for most of Les miserable.) They only crowned a different king this time, so it wasn't as radical, but people sure died. The July Monarchy heavily favoured people with wealth with the proverbial laissez-faire politics, so there was a failed revolution attempt in 1848. The Revolution of 1848 sparked revolutions all around Europe, since royalty wasn't being great there either. The second republic got overturned in 1851 in a coup de etat by some nephew of Napoleon proclaiming himself Emperor. This leads to the Second Empire (of France) where they were fighting some "light" wars like the Crimean War 1853-1856. That was mainly against Russia, for who gets access to the Black sea (still relevant today :/). It's probably today best known as the war where Florence Nightingale did groundbreaking nursing work. This came to an end in 1870-71, with the Franco-German war or War of 1870. Most German states were still pissed France beat them under Napoleon, France was trying to reassert dominance on the continent and also eyeing the slow organisation of German states together with trepidation. That said, Prussia started the war under chancellor Otto Von Bismarck to explicitly kick in the front door Paris and unify Germany. They had been working for that with several other wars against Austria, Denmark and each other for a while. Somehow absolutely pulled it off and crowned the King emperor in Versailles in 1871 and France was mad about that for sure. As always, people at home died which is why there is the dip around that time. After that you have the Third Republic. Being the losers of the Franco-German war, they had to pay Germany reparations for losing. There was also a financial crash in 1873, so that didn't help. It also engaged in the "Scramble for Africa" mostly between 1884-1913. More or less colonialism Olympics between France and Britain, the British tried to get a length of colonised land from north through south of Africa, while France was trying the same only from east coast to west coast. So no way these interest didn't collide in there. And one French dude was trying to make the Suez canal happen, which succeeded. Absolute horrible era, but they were terrorising people in the colonies and plundering riches (because they needed the money), so until the start of the first world war it was also the "Belle Epoque". The industrial revolution has also been going on. You get early cinema and photographs, telegraphs, automobiles like peugeut, the Eiffel tower being build, electric lights with paris being one of the first cities being electrified, germ theory and radio activity being discovered. In art you have Picasso, art nouveau, expression, impressionism, japonism, fin de siecle around the turn of the century. Thus ends the long 19th century when the hunger of colonialism finally collides in the first world war. I hope this made you a bit more interested in the long 19th century, which sure was long. It's no accident you had Victor Hugo and others writing a lot about the plights of the poor. The literary movement realism started in France in the 1840s as a response to the absolute vile conditions for some and pulled no punches. For the first time, paintings actually focused more on ordinary people as well, showing everyday people and workers instead of just royality and people with money. Alternatively there is also naturalism, though they overlap to a degree. Well known works are Middle march, Mark Twain, John Steinbeck, Upton Sinclair's The Jungle, Jack London, Balzac, Alexandre Dumas (three musketeers), Madame Bovary by Gustave Flaubert, Tolstoy, Dostoevsk, Anton Chekhov, Henry Ibsen and you could argue Charles Dickens.

"What is going on in France (in the 19th Century)" is like the History equivalent of "What is Gravity?"

Revolutionary French viewed warfare as an academic pursuit. They would bring scientists and artists with them to solve engineering problems and examine (pilfer) art. Being in campaign is bad for your long term health!

You are a gem! Thanks for these mind-blooming videos

History degree and I’m trying to understand the faraday effect but you’ve honestly just poleaxed my entire consciousness trying to understand how Egypt was like OIF or how Bush likens to Napoleon.

The existence of top tier physicists implies the existence of a physicist tier list and I feel the viewing public is owed a glimpse of Dr. Collier’s work in this area

thank you for updating your channel title to something my dyslexia can parse :)

Thank you for all of your efforts! You are amazing!

I find these videos, both informative and very soothing.

Very neat experiment. It was funny that when you got things attached I went "oh there it went!" and then you pointed it out a few seconds later haha.

I think of my self as at least some what scientifically literate but I've never heard of this experiment. 15:40 Gas Light 1792 , Lime light 1826 Thank You!😃

That was the first time I've ever seen the Faraday effect actually demonstrated! Neat bit of work. Polarizing films or 1.25 inch eyepiece filters are probably still available from Edmund, and magnets you can get anywhere. That would be a fun thing to have around, then donate somewhere. I know a couple of teachers.

Yes, another acollierastro! So hyped for this! :)

In hope of making it sound a little less repellant to you, corpuscle is pronounced to rhyme with muscle :)

The frenchmen were likely dying younger due to some combination of more densely packed cities, worse sanitation in those cities, particular local pollution types based on industry, diet (don't forget how much butter French cooking uses), military service, casualty in regional conflict, and a scoche of confirmation bias (e.g. you just haven't found the scottish physicists who died young yet).

This is actually kind of a good companion video to LowSpecGamer's video about the development of liquid crystal displays. He didn't really drill down into the physics so much since he's more interested in the manufacturing and application in consumer electronics.

yay, a new video! Thank you

Btw…Glucose is also called dextrose because it rotates polarized light to the right.