Ologies with Alie Ward - Invisible Photology (INVISIBILITY CLOAKS) with Greg Gbur

Episode Date: May 10, 2023

Invisibility cloaks. Transparent frogs. Stealth bombers. Gorilla mischief. Theoretical optical physicist and Invisible Photologist Dr. Greg Gbur joins Alie to chat about light, illusions, secret technology, science fiction inspiration, terrible camouflage, great movies, historical mishaps, and even a few great household life hacks – and why you should go read a book on your porch. Perhaps his book, Invisibility: The History and Science of How Not To Be Seen. Visit Dr. Greg Gbur’s blogs, Skulls in the Stars and Science Chamber of Horrors, and follow him on Twitter, Mastodon, Instagram and TikTokBuy Dr. Gbur’s book, Invisibility: The History and Science of How Not To Be Seen, on Bookshop.org or AmazonHis 2019 book, Falling Felines and Fundamental Physics, is also available on Bookshop.org and AmazonA donation went to Doctors Without BordersMore episode sources and linksOther episodes you may enjoy: Molecular Neurobiology (BRAIN CHEMICALS), Ophthalmology (EYES), Malacology (SNAILS & SLUGS), Teuthology (SQUIDS), Cosmetology (GLAM/GROOMING), Quantum Ontology (WHAT IS REAL?), Cosmology (THE UNIVERSE) Parts 1 & 2, Plumology (FEATHERS), Medusology (JELLYFISH)Sponsors of OlogiesTranscripts and bleeped episodesSmologies (short, classroom-safe) episodesBecome a patron of Ologies for as little as a buck a monthOlogiesMerch.com has hats, shirts, masks, totes!Follow @Ologies on Twitter and InstagramFollow @AlieWard on Twitter and InstagramEditing by Mercedes Maitland of Maitland Audio Productions and Jarrett Sleeper of MindJam Media and Mark David ChristensonTranscripts by Emily White of The WordaryWebsite by Kelly R. DwyerTheme song by Nick Thorburn

Oh, hey, it's your friend who puts all this sticky change in a water cooler jug to buy a jet ski one day. Allie Ward, welcome back to oligies. If you're there, I can't see you. But even if I could, could I? Let's make sounds about sight, shall we? Okay, invisibility, it's here. This oligist wrote the book on it.

It's called Invisibility, the history and science of how not to be seen. How does one become such an expert they can write a book about invisibility? Well, first you get an undergrad and a master's degree in physics and then a PhD from the University of Rochester in theoretical physics and get stoked about the optics of all that we can and cannot see. So this guest is a professor in the Department of Physics and Optical Science at the University of North Carolina at Charlotte and has well over a hundred published scientific papers with titles such as super oscillatory behavior in partially coherent fields.

How do we even go about covering this? How do I do this episode? Will I even ask questions that make any sense? Let's see. I was so nervous to jump on this chat with him. So let's see how I do. Okay, but first, thank you to all the new listeners who came from Radiolab. Hey, I loved being on the show last week.

Thank you, Lulu and Lottif for having me. And if you wish that we had a kid-friendly version without swears, we do. Don't worry, we do. They're called spologies and they are linked in the show notes. You can go to oligies.com. There's a link right there for you. Thank you patrons who chip in a buck or more at patreon.com and submit questions for the oligies ahead of time.

And thanks to everyone who rates and subscribes and reviews, which really does put us up on the charts. This week, we were the number three podcast across all categories, a lifetime record, just surreal. And I read all of your reviews and to prove it, thank you, Reed Nez, who left the review this week. I somehow just discovered this not at all hidden gem via Radiolab. It's already my new favorite.

I can't wait to nag all my friends and family incessantly about it. Thank you for doing that. Also, Chiba Pet, who left two stars because of language. I do have one word for you and it's not for letters, it's small g's. Those are the, again, G-rated, shorter versions of episodes linked in the show notes. Your welks. Okay. So, the oligy here, invisible photography, and photography is the study of the physics

of light. So is spectrology, but spectrology can also be the study of ghosts. So, let's just stuff that term in our bra for later because Spooktober is only five months away. But yes, this wonderful physicist has a book about light and invisibility as well as a previous one titled Falling Fee Lions and Fundamental Physics. So we hopped on a call alongside a few kitties, the furry subjects of his first book. They kind of cruised around the camera a few times, much to my delight.

And we covered camouflage patterns, stealth bombers, maybe solved the riddle of why the universe is expanding. We talk guerrilla mischief, see-through skin, household life hacks, the blackest black, the best sci-fi books and movies on the topic, practical applications, as well as obstacles to invisibility, why you should go read a book on your porch, and so much more with professor, author, optical, theoretical physicist, and expert in invisible photography, Dr. Greg Gabor. You know, I use he, him.

My name is Greg Gabor. And, you know, I cannot believe that your job exists. But I imagine that you probably get a lot of disbelief when you try to explain what you do and what you study. How do you introduce yourself at dinner parties? How do you say what you do? Well, usually I start by just saying I'm a theoretical, optical physicist, so I study the science of light.

And if I had to get more descriptive, I often describe my more paying part of my job that I actually get funding for these days, which is sort of light propagating in the atmosphere. But then if I want to shock people, then I'll just be like, yeah, and I also study theoretical possibilities of invisibility. I mean, first off, I guess my first question is why do we call it an invisibility cloak and not an invisibility calf can or an invisibility coat? Or there are so many other nouns that you could possibly make invisible, right? Yeah.

I like to tell this story about writing my book that I nearly had a heart attack when I was doing the research on it because I was searching old journals looking for other papers that might talk about invisibility, and I found a paper from 1944 that was talking about cloaks of invisibility. And I was like, what? But they were talking about camouflage. This was World War II, and they were literally just using invisibility in the literal sense of you can't be seen.

Oh, wow. And now we've taken it in such a far direction. Okay, so I tracked this paper down, and it was written by one Dr. Frank Thone, who explained the military use of things like pseudo haystacks and dug out holes with grassy trapdoors like spider burrows. And now the word cloak, just historically, comes from a root cloche, which means bell-shaped. And this paper is titled Cloaks of Invisibility, but then the word cloak is not used again in the whole body of the article, but Dr. Thone does maintain some journalistic cloaking for

the military, writing, many of their works are of necessity not open for public inspection at present. What Hitler doesn't know won't hurt him until it jumps out and bites him. Good one, Dr. Thone. Getting back to the propagating light in the atmosphere, can you explain a little bit about what that is? Sure. It's all about just sending laser beams through the atmosphere.

And our atmosphere gets this turbulence in it. It churns and royals, and on a hot sunny day, if you look over a road, you see a shimmer of the image across the street. And the problem is, is that people would like to design free space optical communication systems. Translation, sending data without cables or wires. So getting rid of the fiber in fiber optics, Greg explains. You send a laser beam from point A to point B, and you send data that way, just like we

send data through optical fibers. But the light goes through the atmosphere and it gets distorted, and that can basically garble your message. So people are trying really hard to figure out what are the best ways to try and mitigate the distortions that that atmosphere does. And are there any types of light beams that work better in the atmosphere than others? How's that working out? And nobody still has an answer.

Is that something that you think that in this lifetime we might figure out, or does that rely on technology that doesn't exist yet? I think we're at the point where we're starting to see a lot of interesting applications and developments in this sort of free space optical communications technology. So the science is out there to improve the technology, so I would not be surprised to see more of it in use in the near future. And you've been studying optical physics for decades now, correct? That is correct.

I need to admit. Where did that spark, that light kind of start for you? Well, physics in general, it's sort of interesting that originally when I first became interested in physics and decided to pursue it, it was my high school physics teacher who really got me excited about it. He was a very quirky guy and he just made physics fun and made it seem fun to be a physicist. So I went to college for physics and originally I was doing experimental particle physics. As one does.

And I had this feeling like I really wanted to study the most fundamental aspects of nature. But after I was in grad school and I did that for a couple of years, I decided that I loved the results of the research, but I didn't really like the day-to-day work. Because you have these big high-energy particle physics groups and you end up doing a lot of busy work just to keep the systems running and to make everything work, which I don't criticize it, but it just wasn't for me. And then I met Emil Wolf who ended up being my PhD advisor and he was one of the recognized masters of theoretical optics.

And he just sort of one day I went to see him and he said, well, I'm kind of old and I could die at any moment. But my doctors say I'm healthy and if you want to work with me, here's a stack of papers that I recently published, go look through them. What an intro. Yeah, that was always his personality. It was always very quirky and had a great sense of humor that I try and carry on. Just a side note about Emil Wolf.

So as a youngster, he fled German-occupied Prague in what's now the Czech Republic. And according to an article by the University of Rochester, he remains one of the most recognized optical scientists of his generation. And his principles of optics textbook is the most cited textbook in physics ever, it notes. And one of his former students said that Dr. Wolf was deeply committed to equality and justice. And the most upset he ever saw him was when he thought a student had been treated unfairly because of race or gender.

But in spite of all of his achievements, they said that he did not take himself too seriously. And Greg is also quoted in this piece saying that he felt less like Dr. Wolf's employee and more like a member of his extended family. And Dr. Wolf died at the age of 95. But when they first met... He gave me this huge stack of publications that were all very recent, which did convince me that, yeah, he was still doing very well. And I just fell in love with the study of light as a wave, the mathematics and the theoretical

aspects of it is all just really elegant mathematics. That's just so much fun to work with. And here is where Greg kind of flipped a switch for me about light. I've never heard light be described as elegant mathematics. That's so fascinating to hear that that's how your brain kind of receives that and finds that order in it. Yeah, you know, I often explain it to people that on a daily basis, light seems very mundane, like just light sources in our house that we use to drive at night and so forth.

Everything seems very routine. It's only when you start to set up very careful experiments to study the wave properties of light and then eventually the quantum physics of light, you realize that it does a lot of very strange things and that there are a lot of unexpected effects that come from just the behavior of light. We don't see most of them on a day-to-day basis because our light sources are relatively ordinary, but you probe a little deeper and you find all sorts of really neat stuff happening. And for someone who is not an expert in theoretical optical physics, can you explain to a layperson,

what is light? I'm sorry. I'm sorry to ask this, this is supposed to be so exhausting for you, but for someone who takes it for granted constantly, how would you explain what light is? So if you're new around here, we ask the smart people the not smart questions because nothing is simple. Well, yeah. Sorry.

No, no, that's fine because it's a great chance to open with an old Einstein quote from a letter where he says that, to paraphrase it, he spent his entire life asking the question, what is light? And nowadays, every rascal thinks that they have the answer, but they're all deluding themselves. Shade. Wow. Yeah.

I want to come back. And he really hits it because at the basic level and historically, before anybody really seriously started doing research on light, we viewed light as this sort of stream of particles that a light source emits particles that we now call photons. And on a day to day basis, if you just look around sort of at lights, light sources casting shadows and stuff, that's kind of what it looks like that light seems to just stream out from a source. And if it hits something along the way, it bounces off of it and gets reflected or it

gets absorbed. The history is way back when everybody was convinced it was a stream of particles, then in the 1800s, people said, no, light is a wave. And then Einstein came along and said, no, light is a wave and a particle. Like a Reese's Peanut Butter Cup, it's the both and even better for it. I'm going to steal that. The one contribution I made to theoretical optical physics. I will be sure to credit you any papers that come out.

I'll take it. And so if it is a wave and a particle, I've always wondered, where does it go? If it's a particle, once it zooms past us, is there a repository of all the light in the universe that reached some final destination? OK, we're here. Well, that gets into that to some extent gets into cosmology and in a little outside of my pay grade. But as far as we know, the light that's out there, that as long as it's not hitting anything,

it just keeps on going. We can turn this around and say we know from astronomy that there's light that's still reaching us that's been traveling for billions of years from near the beginning of the creation of the universe or the emergence of the universe. And we're only seeing a lot of that now. So it's just sort of traveling along and nobody really knows if it's going to reach a boundary or not, I don't think. Is there any possibility that the reason the universe is expanding is because light's pushing

it out? I'm not sure. I've never really thought about that, you know, could be. I don't want to speak too much about it or all the cosmologists I know are going to jump all over me. Right. Now, when we're talking a wave, too, that wavelength that determines what color we perceive it as.

That is correct. Yeah. If we're talking about ultraviolet or things outside of the visible light spectrum to humans, is there any work in invisibility to try to make things that are outside of our spectrum? To like make a physical structure that is, say, not seeable in the visible range but visible to ultraviolet? Yeah. I suppose you could just get ultraviolet glasses, though, and then your whole scheme

is interrupted, right? Yep. Yep. Okay. So check that out. Yes, that was some of the earliest science fiction explanations of invisibility where people tried to imagine how invisibility could happen. They thought, well, we know that, you know, certain glasses are very transparent to visible

light. And so it's natural to imagine that there might be some sort of material that is perfectly just doesn't interact with visible light and only interacts with ultraviolet or something. And that's where a lot of invisible monsters in fiction come from. They're creatures that are of a color that just is outside of our spectrum to see. Are you inspired by science fiction? I know so many inventors and so many scientists are, and I interviewed Marty Cooper who invented the cell phone.

He was inspired by Star Trek. So were you ever someone who loved science fiction? Did that ever inspire your work? Oh, yeah. I mean, I still arguably am. I've been tearing through all these old classic invisibility stories looking for other interesting ways that people have imagined invisibility that we haven't even thought of yet and finding a lot of surprises in there.

Really? Anything that you would ever kind of go down a research path on? Possibly, but I'm not sure yet. So far, they're just really neat ideas. Okay. So he fell in love with the elegant mathematics of light, which is composed of photons that act as both a wave and a particle. And light is a part of the spectrum of electromagnetic radiation that's visible to the human eye.

And it's measured in billions of a meter or nanometers. And wavelengths around 400 nanometers appear to us as violet light. And then it goes through the rainbow down to longer and longer wavelengths about 700 nanometers, which appear as red light. And ultraviolet light therefore has shorter wavelengths, but higher energy than the violet light and thus UV rays. But infrared is longer wavelengths and has scientific applications like thermal vision and night vision and telescopes, which are real and exist.

But has science fiction cracked any codes? And actually, what is the code, practically and theoretically speaking? Greg, get us into it. So a modern day invisibility cloak that people talk about the sort of rough description of how it works is it sort of guides light around a hidden region and sends it on its way. And there have been a half a dozen or more science fiction authors that sort of had that vision of how it would work. And they anticipated the science that is being done these days.

It's not something I've thought about a lot, but why are some objects just transparent? Why is saran wrap and glass and Wonder Woman's jet? Why are some things we can see through and others we can't? Well, this actually goes back to your kind of comment about can we make something that's only visible in the ultraviolet and perfectly invisible in the visible range. And the reality is that in general, and probably part of the reason that we see in the visible range is that that's where most of the light absorption of materials happens. Just atoms and molecules and stuff tend to absorb visible light very strongly.

And so it's kind of natural that we would have evolved to see in the visible because that's where everything's going to be the most visible. But then when you talk about things like glass, it usually comes down to the fact that certain materials just don't absorb light very strongly at certain wavelengths. And if they happen to not absorb very strongly in the visible regime, then we get what we would consider transparency. And transparency and invisibility, I imagine, are probably hotly debated at a lot of conferences. But has there ever been a change in definition for transparency versus invisibility?

I find it kind of interesting that I don't think people have really thought about it too much from a technical standpoint. The terms are kind of flexible and maybe often suggest more than they should at times. Like I said, people use the term invisibility even in science journals to talk about literally hiding behind a bush or something. That's the best thing I've ever heard, I'm sorry. But it has come up more often these days because the idea of perfect invisibility would be that you create an object or a cloak, that there's no possible way you could detect it

with visible light. But people have realized that that's really, really hard to design something that could do that and maybe even not really possible. So over the past kind of decade and a half, you've found more and more people saying, well, I can't make something perfectly invisible, but if I make it less than perfectly invisible, then it becomes something that I could possibly make. So you find that the definition of the term invisibility, people are kind of pushing the definition more towards something closer to transparency where it's really that it's

very see-through and it's very hard to see, but it could still in principle be detected. So there is kind of a fuzzy boundary there. Yeah. And Greg explained via a blog post over 10 years ago that something called an attenuation coefficient measures how strongly light is attenuated, which means it dissipates in a material and an object can absorb photons and their energy can be converted to heat, which is why being goth in August is kind of a sticky proposition. But light can also scatter.

So the lower the attenuation coefficient is, the more transparent an object is. Then there's the issue of reflection when light bounces back at you, making glass visible at certain angles, especially if you're in the light. So if you were standing in the dark looking inside at a window, there'd be less reflection because you're in less light, but then there is refraction, which changes the trajectory of light and bends it, making a transparent object visible. So Greg writes in this blog post, so what would it take for an ordinary material to be invisible?

Not only would it need to be transparent, having an attenuation coefficient close to zero, but it would also have to produce no refraction and have the same refractive index as air. So what does this have to do with wigs, semantics? So if you're looking to buy a lace front wig and you're wondering why the transparent option is cheaper than the HD lace option, well, I just learned that the transparent one is less invisible. It's more noticeable.

The HD wigs are higher quality and thinner lace in front, which means less attenuation, which means you will have to pause, drag race, and stare into their hairlines to detect them, or you could just tape the show and watch it frame by frame. Tape, who tapes? Scotch does. Apparently Scotch tape makes transparent tape, which is glossy and see-through. But they also make magic or invisible tape, which is cloudier and matte and absolutely not transparent or invisible, but it does blend into paper better and you can write

on it. Oof, you could debate this all day, but let's talk about transparency in academia. I imagine in some parts of science, people are very keen to share their research, and I imagine that this is not one of those areas. Is it hard to collaborate with people? Because by nature, you're trying to do something secret. Yeah, I think it's actually okay, though, where I can't speak very well of it is I'm guessing that there are a lot of military research labs that are maybe looking at it

very seriously, and they're probably not talking to anybody about it. I kind of think of stealth technology for stealth aircraft, which is a very different sort of invisibility, but they kind of coat their planes with radar-absorbing materials that they don't really want to talk about what those materials are. On the other hand, in the 1990s, a lot of this research on invisibility got started because private companies discovered their own radar-absorbing materials that they couldn't quite figure out how they worked, and those companies, for all we know, were probably rediscovering the same sort of thing that militaries have been already using for a while.

So it was an intentional outcome, but still a technological mystery. This company, it was a British company, was trying to make a material that would be really good at absorbing radar, and they succeeded. And then they said, wait, we don't know how this works. It works really well, and we don't know why. I might as well spend a sunny spring afternoon indoors reading about stealth bombers. Well, I did, so you won't have to wonder. Okay, so this British company was known as GEC Marconi.

It was founded by a guy way back in the day named Guglielmo Giovanni Maria Marconi, and you're never going to believe this, but he was Italian. He was also awarded the Nobel Prize in 1909 for his contributions to inventing radio, and his mom was the heir to the Jameson Whiskey fortune. What? He installed Vatican radio in 1931 for the Pope, which is like getting Mother Teresa on TikTok. But what does this have to do with the Titanic?

Okay, so Marconi International Marine Communication Company was a telegraph company, and that was the one aboard the ill-fated ship on her maiden voyage. And operators sent out an SOS, and 17 minutes later, the ship Carpathia got it and was able to haul last 58 miles to the site of the Titanic sinking and pick up 705 souls, who thereby survived. I'm sorry. You thought we were talking about stealth bombers? We were.

Okay, so Marconi, credited with inventing radio, big telegraph guy. And in Greg's new book, once again, Invisibility, the History and Science of How Not to Be Seen, Greg explains that the stealth bomber itself has a flat bottom, which means that radar waves primarily reflect in a single direction instead of all over the place, like they would on a round tube plane, and thus they're less likely to hit a radar station on the ground and be detected. But the material of the stealth bomber is a carbon graphite composite that absorbs a significant amount of the radar energy beaming toward it.

So Greg says that in the mid-1990s, researchers at the UK-based defense company, GEC Marconi, were fiddling around with anti-radar materials, and they developed this substance that was very effective at absorbing radar. However, they had no idea why their material was so effective. So they had to go to this theoretical physicist, Dr. John Pendry, at the Imperial College London and say, hey, why does this work so good, Doc? Because of teeny tiny fibers that overlap and help absorb radar. What is the big deal?

Well, everyone silently freaked out because they realized that the structure and not just the chemical makeup or the materials can influence the invisibility of objects. Also, side note, I'm guessing that Marconi scientists were also silently freaking out because in researching this, I just learned that in the late 1980s, early 1990s, several defense and computer engineers working on these top secret projects died in bizarre and really grisly circumstances, one after the other, enough to raise a lot of coroner's eyebrows and some international suspicion of Russian assassinations. Anyway, invisibility optics, thrilling, sometimes scary.

Do you get approached by the DoD? Do you have to keep anything under wraps? Do any of your neighbors think you're a spy? No, not for my work. Fortunately, everything that I do has been very non-restricted research. And as someone who works on the theoretical side, Greg has to look at all those elegant mathematics to figure out the theoretical solutions before anyone can go sketching invisibility chambers on the backs of napkins.

Are there a few basic tenants when it comes to creating something with invisibility, like optically? Are there a few different principles that are the major ones people are kind of looking to target? Oh, yeah. That's a very good question, and I don't think anybody's ever asked me that before. Oh, my heart leapt because I was so nervous to interview him. The very first sort of in 2006 was when the first two theoretical papers about invisibility

came out, and they both used a technique that's nowadays called transformation optics. And the idea of transformation optics is that if you could imagine mathematically, and I stress mathematically, you could imagine mathematically warping space, like you poke a hole in space and you stretch open a gap, and then everything kind of flows around that gap in space that you've made. So people realized in the late 1990s that you could do this mathematically, and not only could you mathematically design a warping of space that could make an invisibility cloak, so that gap that you've made in space becomes your hidden region that you're hiding, and

then all the light just sort of flows around it. Mind the gap. But then they realized that after they'd derived that mathematical formula for the warping of space, that they could directly figure out what sort of material structure would produce the equivalent of that warping. And so I stress again, there's no actual warping of space. It's a mathematical warping, but it turns out that you can, for any sort of warping of space, you can imagine, you can find a material that effectively does the same thing.

What type of materials could possibly simulate a warping in space? Is it things that are really magnetic or things that are really heavy or dense or nuclear or irradiated? Well the magnetic gets to it. One thing you need is most natural materials that exist for visible light respond to the electric field of a light wave. The light wave consists of an electric and magnetic components oscillating together. And those two waves are at right angles to each other.

Kind of think of a shark's dorsal fin and pectoral fin, except one is magnetic and one is electric. And Greg says that most natural materials respond only to the electric part of a light wave, but there are in principle materials that could respond to the magnetic part as well. And if you can make a material that responds to both the electric and magnetic part, that's the sort of material you need that can help you make something invisible. Oh my gosh. This is mostly done theoretically with mathematics and crunching a lot of data and numbers to

see what might be possible. Yep, but the trick that's come out of this is people did these theoretical calculations to say, well, in order to do this, we'd need this sort of material that doesn't exist in nature. Boomer. But some of the same people were actually already studying this idea of what people call metamaterials now, which are, hey, we can actually in principle make materials that have optical properties that nothing in nature actually has.

How does that happen? Do they reflect structurally differently, like, you know how some bird feathers or some pigments on insects aren't actually blue, but it's a structural color? Is there anything like that being developed that's a structural not color? You've hit it almost exactly correct because those bird feathers or beetle shells and stuff, they derive their sort of shininess not due to the actual materials that they're made out of, but due to the fact that those materials are put together in a strange way, like strange layers, and that's sort of the idea of metamaterials is saying, hey, most of the time when you think

of the optical properties of material, those optical properties come from the chemistry of the atoms or the molecules that are present. So Greg offers up an invisibility visualization. We picture kind of like a bunch of Lego blocks that the atoms are a bunch of different Lego blocks, and there's sort of a natural way of just stacking them all together in the simplest configuration. But then you say, well, what if I in fact put them together, but make a little more complicated structure with like little holes in the structure instead of one big solid block, I leave little

holes throughout the structure. Now when you shine light on that structure, even though it's made of exactly the same material, the optical properties are going to be different. And that's exactly what those colorful bird feathers or beetle shells do is that they're made out of the same material as every other feather or beetle shell, but the materials are layered or combined in such a way that they produce different effects. So this is called structural coloration, and it's responsible for the blues and greens on a lot of birds and some brilliant blue butterflies and flowers and even that entrancing

rainbow inside some seashells. And iridescence happens when there are layers of structure and light bounces back through the layers out of phase. So you have a rainbow effect. And this was discovered by a lad named Thomas Young way back in 1803, and not to cause you any existential crisis. But by 14, this kid knew Greek and Latin and French and Italian, Syriac, Samaritan, Hebrew, Arabic, biblical, Aramaic, Persian, Turkish, and Gieze, an ancient Ethiopian language.

Thomas Young has been described as the last man who knew everything. Also important, his friends liked him and said he wasn't even a dick about it. But for more on structural colors in nature, especially feathers, you can see the plumology episode all about feathers. Now what about invisible animals? Oh, we'll get to that in a bit. Any other major kind of categories of invisibility that you would want people to know about that we should touch on to?

Oh, yes. I got on a diversion. Oh, no. I loved it. I loved it. So the one category that people do is transformation optics. And another category, which is kind of what a lot of my early PhD work was more related to is what people would call an interference effect or scattering cancellation.

The idea here is this goes back to light being a wave. And waves can combine to create constructive interference and destructive interference. So you add together the up part of one wave and the down part of another wave, and they partially or totally cancel out, at least at a location. If you're familiar with Young's double slit experiment. I am not yet. That's sort of the classic demonstration of interference. You shine light through two small holes.

You get light waves coming out of the two holes. And if you set it up correctly, if you shine the light from those two holes on a screen, you see these bright and dark bands. Because in some locations on the screen, the light from the two holes is adding together and becoming brighter. In other locations, it's canceling out. Okay, so Young himself was like, this double slit experiment, aka double slit interferometer, is the coolest shit I've done in my life, because it helped push the wave theory of

light into acceptance instead of just Newton's corpuscular theory that said light is made of particles called corpuscles, but they are elastic, rigid and weightless. So yes, Young devised this experiment letting sunlight shine through two slits. And because the light is coming through in oscillating waves, at some points, they're canceling each other out and creating stripes. And that is a classic interference pattern that things that come in waves tend to do. And some people were right pissed that he dared to contradict Sir Isaac. And he had haters in the press, which caused Thomas Young, who has also happened to be

an ophthalmologist, to say screw you, physics, I've got plenty of medical stuff to achieve, such as discovering astigmatism, which I have. And I thank him for that, because I also have it. And we talk more about that in the ophthalmology episode. But back to the double slit creating interference in waves causing those stripes. But imagine you have like a small sphere, you shine a light beam on it, the light's going to bounce off of that sphere and go every which way. So you can see it because it scatters light.

But if... And now you put a layer around that sphere, and you design that layer to produce exactly the opposite scattered wave that the sphere itself produces. And so now the sphere is scattering one wave, but the layer you put on top is basically producing a wave that completely cancels out that first scattered wave. And so in principle, if you do it correctly and it works, you've now got an object that does not scatter light off of it again, and it is invisible. And what about the type of invisibility using cameras and projection to make you think that

you're seeing through something, but you're not? I've seen some really awesome Halloween costumes. I don't know if you've ever seen anyone that looks like someone has a hole through them, but it's an iPad. Oh, yes, I love those. You heard those great? Yeah. Like what?

Yeah. And that's what... That's sort of a third class. The two that I kind of described are what you might call passive invisibility. You design an object so that it's invisible on its own. You don't have to do anything else. It just sits there and it's invisible all by its lonesome. Active invisibility is when you have to do some sort of effort to make the invisibility

happen. And that idea of those sort of camera illusions is the perfect example. So if you want to make an object look like it's got a hole in it, you've got to have a camera on one side that records the scene, and then you've got to have a projector on the other side that projects the scene so that the object looks see-through. So again, passive invisibility is when you can throw off how light bends and wiggles toward your eye while active is more like actual smoke and mirrors or replacing a thing that exists with an image of something that doesn't.

And Greg says that most active invisibility like that isn't true invisibility, but rather an illusion that only works at specific angles or in specific directions. Like the hole in a person's chest. It works well if you're looking at them dead on, but if you look at that hole from an angle, you realize you're still seeing the same image of what's directly behind them. But it is, in principle, possible to also do that active invisibility where you design it so that the object looks completely see-through or invisible from all directions. There was the 2020 film, The Invisible Man, that came out, and Minor Spoiler, it uses

a very much that form of active invisibility. Uh-huh. He said that wherever I went, he would find me, walk right up to me, and I wouldn't be able to see him. Adrian is dead. He's not dead. He has figured out a way to be invisible. Of course it's fiction, but still.

2020's The Invisible Man, side note, is not to be confused with the 1933 film, The Invisible Man, which is based on H. G. Wells' 1897 novel, The Invisible Man, which is about a guy who's the victim of a scientific experiment to make him invisible. Now all of this is not to be confused with Ralph Ellison's acclaimed 1952 debut novel, Invisible Man, Noda, about an unnamed black narrator who has to compete in a battle royale to obtain a college scholarship. And among Ellison's famous lines from that book is the narrators, I am invisible, understand, simply because people refuse to see me.

Ah, books. Are there any that Greg has enjoyed, I mean, about optical invisibility? In written fiction, there is a story by Aljus Boudras, who is one of these classic science fiction authors of the 1960s. And he wrote a story which featured an invisible weapons carrier. And the idea of this invisible weapons carrier is it was a bunch of fiber optic cables. Light from one side would enter this mass of fiber optic cables, be guided around the inside of the structure, and maybe amplified with some circuitry, and then be sent on the

other way to make the object look basically very transparent, almost invisible. And Greg further explains it as structures that are designed to just take light and guide it around a central hidden region and then send light on its way. And in this story for love, a bunch of extraterrestrials are marooned hanging out on Earth's surface. They got a broken spaceship, and all the humans are like, well, fuck, what are we going to do? They're trying to kill us. And they move underground.

And they figure out we'd hide a weapons carrier with this fiber optic light detour. Not only is that some ACEs vintage atomic age sci-fi, but Greg says that the optical physics logic pretty on point, which is groovy. And so Aljus Boudras really nailed it. He not only had that concept of guiding light, but he said, here's how I might imagine it happens. And can I ask you questions from listeners? They know you're coming on specifically.

And we do a lightning round. Of course. OK, but before we strike with those questions, first we'll take a quick break to rest your brain. And while we're at it, we'll give out some cash to a cause of the Aljus choosing. And hey, did you know that while a lot of state and country lines exist, you can't see them? So I guess it's only fitting that Greg chose Doctors Without Borders, which is a nonprofit

that delivers emergency medical aid to people in crisis with humanitarian projects in more than 70 countries, because they say wars, diseases, and disasters, no no borders. So a donation will go to them in Greg's name. And thank you sponsors, apologies, who make our donations possible. OK, let's see what you asked a lightning round. OK, Katie Holtman, great question. What kind of laws would have to be in place if invisibility was actually achievable? Do you think that there needs to be some sort of governing body that's like, hey, don't

do that, don't do anything mean? That is a good question. And it fits into that whole that whole aspect of modern society that we tend to rush forward and figure things out without actually thinking about the consequences. And yeah, probably you would imagine that if we could if we can achieve it to that sort of science fiction level of being able to walk into a room and nobody else knowing you're there, we would almost certainly need to have some sort of rules or regulations to keep things from getting out of control.

I can see you, but you can't see me. I do like to say, though, I don't think we're anywhere near that stage yet. So to be a little reassuring, I think we're a ways away from anybody achieving such a thing. OK, that's good. That's good to know. So we're figuring it out as we go along, kind of. And Eric Burnett, Milan Ilnicki, both wanted to know about in an age of AI and facial recognition and cameras everywhere, how could a person remain anonymous, Eric asks?

For example, is there tech that could scramble facial recognition in facial recognition? Is invisibility becoming something that is more protective of the average person? That's an interesting thought. I imagine it could be. I am very aware of the fact that people have been working on all sorts of schemes and patternings that can totally throw off facial recognition, because that is another technology that really seems like it just sort of got thrown out there without anybody really thinking about the downside.

Right. OK, so Patron Milan Ilnicki left a comment on the questions thread on Patreon saying that the head of their Halloween costume a few years ago incorporated a block-headed helmet printed with a special anti-facial recognition pattern, and that's called Hyperface. It was developed by this artist named Adam Harvey, and it looks like kind of a digitalized mishmash, like blurry, pixelated faces. So facial recognition software gets overloaded trying to find the possible eyes and mouths. It's kind of creepy.

It's kind of like when you see a face in something, but do you, do you not? But pixelated looking. And Milan smacked a QR code right in the middle of it, which then led people to a URL about facial recognition. But what about the pandemic? Don't masks kind of obscure you? Think again. So I checked into this and read this 2022 article titled, Facial Recognition During Coronavirus.

Do masks block facial recognition? Which essentially found that, yeah, computers know it's you by your eyes and your head shape. And to illustrate, they included a bunch of photos of Ben Affleck in a surgical mask, and you're like, yeah, that's fucking Ben Affleck. But there's also this scene in a 2008 movie, I can't stop thinking about The Dark Knight, where the Joker shocks Two-Face in the hospital by pulling down his medical mask so you can see his mouth, and the revelation causes convulsions of sudden fear in Two-Face. Despite the fact that Heath Ledger's character's face is scarred and white and his eyes look

like a haunted clown, but that's neither here nor there. In real life, facial recognition algorithms and invisibility jumpsuits, they could be tried in a Supreme Court near you. Yeah, we need some theoretical, optical lawyers. Some great questions were asked about nature, Bronwyn Cole asked, are there any living organisms that have the power of invisibility? And Edna Ordnezino's first time question asked her, I wanted to know, does an animal's ability to camouflage count as invisibility, such as an octopus or a chameleon?

Any animals doing it really well, and what counts as invisibility? The term invisibility is simultaneously very suggestive and also very vague. I would say that for most generally, you would say camouflage definitely counts as invisibility. The term invisibility just literally means that you're unseeable. A lot of camouflage out there probably does a better job than anything that anybody has tried to make in terms of a proper invisibility device so far. So I definitely count animal camouflage as a form of invisibility, though I don't talk about it in my book because there's so much to be said about camouflage that I would

have had to have written twice as long of a book just to talk about nature. Oh, I'm sure, speaking of invisibility jumpsuits, those shaggy, moss-colored onesies that hunters wear are called ghillie suits, and the name comes from boy servants of yore, who would accompany Scottish hunters into the field. And why were they called ghillies? Possibly from the term ghillie-doo, which in folklore was a lone male fairy, so a little nocturnal woodland sprite covered in lichen, in twigs doing good deeds, which sounds like someone I would want to kick it with.

But nowadays, ghillie suits are used in war and for hunting, they're used in police stings, and I was perusing the Workerpedia page for ghillie suits, and noticed kind of like a forlorn postscript that said, civilians have, on rare occasions, purchased ghillie suits to commit crimes. But your friendly nature photographer might also post up and want hoping to get shots of critters. Yes, technically, you can purchase an invisibility cloak at Big Five Sporting Goods for $36.99. Do you ever go back and look at historical camouflage patterns to see how they've changed

it all? Like, is camouflage getting better as the years go on? Well, there was an article I read a while ago that said that some camouflage has actually gotten worse. A few years ago, the US military, I think, adopted some patterns that they thought worked really well, but they had sort of tested it under very specific circumstances and thought it worked really well as an urban camouflage, but actually out in the field, it works much worse than the stuff they were already using.

No. And so that was sort of a boondoggle, if I remember the story correctly. Oh, what a boondoggle it was. Let me tell you about this. Can we gossip? Great. The universal camouflage pattern was introduced in 2005, and it's made up of these washed out tones of green and gray and beige, and it was designed to work against both greenery

and desert terrain. Also, the universal camo pattern had a pixelated look, which was modern and cool. One issue, it did not work well. So I found an article that said the primary issue was an optical effect known as isoluminance, and this is when the human eye interprets a number of colors and patterns as a single mass, so that means that they can see you. So the army had to pull universal camo out of commission and replace it with a pattern called operational camouflage, and the whole thing cost them about $5 billion of yours.

And if you're thinking, did she camies? Isn't that the pixel pattern of the Marines? Never, ever call a Marines fit universal camo pattern, not unless you have like an hour to spare and really good health insurance. So Marine camo is called MARPAT, Marine pattern. And it was developed before universal camo, and it is pixelated looking. It was issued in 2002. It's still in commission, and it was based on a bunch of pixelated photos of terrains.

And the Marines say it works hella good, and no other branch of the military is allowed to wear it. But anyway, a $5 billion mistake that also cost lives. So camo, serious business. But it also highlights the point that the military is constantly looking for improvements on camouflage of how to do things better, though I don't think we beat a lot of nature at that. They've had millions and millions of years in iterations to perfect it.

So yes, biomimicry looks to nature, and then it just cheats off its paper. And a lot of patrons, namely Bronwyn Cole, Sarah McCarron, Naderian Knight, Shannon O'Grady, Marie, Chelsea Willick, Valerie Bertha, and specifically Alayna Crusen and Zed Shiragane, wanted to know how some living animals can be transparent if there's blood and cells and tissue, like glass frogs. How can you see through something that has matter? You know, I haven't looked into the details of like the glass frog in particular and how it maintains so much transparency, though I did read an article recently, I've been

compiling a bunch of stories of animal invisibility recently. And if I remember correctly, it may very well have been the glass frog that when they're sleeping, they hide by storing most of their blood in one of their organs. I'm just going to put this right here. So there is a problem that, yeah, blood is not very transparent. So even if the animal's mostly transparent, it's got all this blood going through it. So when they're sleeping, they dump most of their blood into one of their organs and keep most of it in their liver.

Yep, that was the story. That just came out not too long ago. Oh, wow. Oh my gosh, just like taking everything, put it in the closet for now. We'll use it. We'll bring it out when we need it again. And for more on this, you can see the 2022 paper titled, Very Clearly, Glass Frogs Conceal Blood in Their Liver to Maintain Transparency.

And for more invisible critters, you can check out animals like the aptly named glass squid, just a whole mess of jellyfish. There's this white-blooded, Antarctic-dwelling crocodile fish, Peruvian glasswing butterflies. There's a clear, shrimp-like creature called a cystosoma, which sounds like something that you have to pop. You can also marvel at the camouflage capabilities of any of the chromatophore-bearing cephalopods that we talked about in this squid, aka, toothology episode with Dr. Sarah McNulty. And of course, don't forget hair cloaks of foxes and hairs that adapt to their snowy

environment, which by the year is less snowy for less amount of time in putting these animals in greater danger. And there are constantly squirrels close to me that I can't see. They're just blending into tree bark, jokes on us. Squirrels know what's up. Oh, so many great questions. Now, what about dark matter? Anne-Marie Everhart, Connie Connie Bobani, Brenna Quirk, and Erin wanted to know, in

Anne-Marie's words, first-time question asker, is invisibility related to dark matter or dark energy because it seems like they should be related? Any crossover? That's actually a very good question because there have been some people that have thought about this. So I talked about this scattering cancellation idea that if you have a combination of two different objects, you could have them so that the light that scatters off of the combination of two pieces doesn't produce any scattering at all.

That was that scattering cancellation passive invisibility idea. And there's a fundamental type of electromagnetic object called an anapole. And an optical anapole is basically, you could imagine it as a fundamental particle that consists of two different modes on an electric oscillation mode and a magnetic oscillation mode that cancel out and produce no radiation. And there have been people that have speculated that maybe dark matter might be some sort of anapole mode. Now again, so the cosmologists don't yell at me, I've read the paper where somebody

proposed this. I have no idea if it's gotten any credence at all in the cosmology and dark matter community, but people have thought about it. So this paper that he mentions is the 2012 study titled Anapole Dark Matter, which discusses the electromagnetic anapole, which is the only allowed electromagnetic form factor for Majorana fermions. But you can also follow up with the 2022 paper aligning a Majorana fermions anapole moment with an external current through photon emission mediated by the fermions generalize polarizabilities.

But the main takeaways you need to know are that anapoles are shaped like donuts and fermions are teeny, teeny, tiny things like quarks and leptons and atoms made out of an odd number of them and that a Majorana fermion is one that has its own antiparticle. So some dark matter theorists think that the universe is made of things that have a donut shaped electromagnetic field around it. But hey, we have a whole episode on dark matter, aka scoto-hyalology, it's just waiting for you. In the meantime, you can feel free to use Majorana fermions as a pen name for some smutty

novels that you're secretly writing. Let's publish some sensual fiction because we're all just going to disintegrate into tiny or cosmic donuts. And I thought this was a great question. Two people had this same question. Marin Profit and Taylor, both want to know, in Taylor's words, can you explain how, why my wallet and keys turn invisible when I'm late for work? Marin has this problem as well.

They can pass over it two or three times before seeing it. So what's the deal and do mind tricks play any part in invisibility technology? Well, that's actually a nice question in that sense because that kind of goes back to the camouflage aspect too, that our brains are spectacularly weird at how they select what to notice and not notice. And have you ever seen the invisible gorilla illusion? No. This is from the 1999 paper, Gorillas in our midst, sustained inattentional blindness for

dynamic events. So the way I encountered this was a person was giving a talk at an optics conference on optical illusions. And without any explanation, they said, let's do this. So they have like five people, and those five people are bouncing basketballs and dribbling the basketballs back and forth between each other. And so the task that you're given as the video starts is, OK, I want you to focus on one basketball.

I want you to keep track of where that basketball is and try and keep track of it through the whole video and where it ends up. So everybody does this. And at the end of the video, the speaker said, OK, now who among you saw the gorilla? And most people did not because at the middle of the video, a fellow in a gorilla suit just walks right into the center of the group of people bouncing basketballs, looks at the camera, beats his chest and walks off. But it's sort of the trick of our brain is that when we focus really intently on one

thing and we're looking for one thing in particular, we can miss really obvious things in front of us, probably analogous to losing our keys or our wallet. And I have my own example of this, which I'm very bad at recognizing people if I see them out of context. When I was in grad school, there was one time I was walking on campus and I suddenly heard a shout from behind me. And it was my roommate who I had literally just walked right past, even as he nodded at me.

And I wasn't used to seeing him actually at that location on campus, and I just walked right by him. Mm-hmm. There is that condition of kind of facial blindness. Have you ever considered that maybe that you might have that? I have a friend who has that. Yeah. I don't seem to have facial blindness because I'm really, really good at identifying people,

like actors in movies. I can pick out an actor instantly. But if I do see somebody in a situation where I am really not expecting to see them, my eyes can just track right over them. Yeah. I thought it was funny when we got on this call, I said, hi, nice to see you. And you said, nice to see you. And I was like, I don't think we've met before, but I wonder if you think I think we've met

before. We have met before. When did we meet? A comm sci camp, probably six or seven or eight years ago. Oh my gosh, okay, well then, duh, I was thinking, I was thinking, I wonder if I've confused you. Okay, that is so funny. Thank you for reminding me, because as you can tell, I sometimes have that context thing

as well. Yeah. In your defense, I think I said hello and we talked for like two minutes. It's still though. This is so exciting. I'm so glad that we're like full circle, because that was might, might have been before allergies even existed. Yeah.

Oh my gosh. Look at us. So this was at sci-com camp run by my friends, Cara Santa Maria and Jason Goldman and Sarah Curtis of the Nerd Brigade. And since then, Dr. Kapoor has written two books and I make a podcast about allergies. So what a reunion. That's so great. Oh, okay.

That makes me so happy. Okay. I have a curveball, a curved lightball for you. All right. I don't know what this question is about, but I'm going to ask it. So Zombot wrote in and asked, could you talk about the real world lenticular sheet aka invisibility shield that renders a subject behind it invisible as long as there is an uninterrupted horizontal pattern behind the subject?

Lenticular invisibility sheet. What is it? Yes. I know exactly what they're talking about because this baffled me for a little while myself. So a company a number of years ago came out with what they brand name called quantum cloaking, I think. And it was a very strange demonstration because they had a, yeah, this sort of sheet of material

and then a person would be standing behind it, but you would see the wall behind them and you would not see the person themselves and it was called a form of cloaking. And at first I was like, I really don't know what's going on there and I'm not even sure this is real because from all I know it should not be possible to hide somebody like that. I looked this up and a company called Hyper Stealth Biotechnology Corporation demonstrated stepping behind what looked like privacy glass in a bathroom, a little blurry, but then the person completely disappears, not a whisper of them. And they're called lenticular because of a dome shape.

They kind of are like corrugated sheets of a bunch of clear cylinders fused together, making something that's ribbed and can throw off light. It can blur everything in the horizontal direction, but in the vertical direction, everything will look exactly the same. All the light along the horizontal axis is going to get blurred together. Oh, okay. But if you now put a person or a finite size object behind that screen, that person is going to get blurred out too.

Aha. You know those old toys that if you, they like came in crackerjacks where if you move them one way, they look like one thing, then you move them another, they look like another. Is that any kind of invisibility, like those kind of ridges? That's pretty much exactly what we're talking about here, is that sort of ability of those ridges creating interesting illusions. Just a side note, the owner of Hyper Stealth Biotechnology Corporation is a Canadian paintball champion named Guy, who has also, according to his website, designed thousands of camo

model patterns for six million military issued uniforms in over 40 countries, including one pattern called Guy-Pat, and despite years and millions of dollars that military branches have spent designing their camo, he says he made Guy-Pat in two hours with a computer graphics program that cost about a hundred bucks, and he says, quote, I have hidden six rabbits in black in this design. There are four bunnies present on the uniform, one on the left shoulder, one over the abdomen, one near the zipper, and one near the right cuff of the pants. There are others, he writes, but I've landed the camouflage so well I can't pick them

out. Camo, the aspect of invisibility cloaking you never knew you needed to know. Welcome to my rabbit hole. Now Catherine Wood wants to know, is anyone using Vantablack to achieve a kind of invisibility, and if not, why not? Do you have thoughts on Vantablack, the darkest pigment, like the least reflective paint in the world? Yeah, I talk about it a bit in my book because that's also science fiction authors have also

considered that as a possible form of invisibility, and in a sense, it kind of works because there is an incident that happened at an art installation that was using one of these ultra heavy blacks to make like a perfectly black hole in the center of a room, and somebody walked right into that hole because they did not realize it was actually a six-foot deep hole. Oh, no. I think they were more or less okay, but it made the very good point that yes, these ultra black blacks that really reflect almost no light at all, it's very hard to tell what you're looking at.

Mm-hmm. Portugal, summer 2018, a museum featuring artist Anish Kapoor's installation Descent into Limbo, which looks like an inky black painted circle representing a cartoon hole, but is really an actual void that drops eight feet into the ground. And a 60-year-old Italian tourist figured it was just one dimension short of 3D, and he was rushed to the hospital but is okay. But would anyone really be okay after that? Ever?

I mean, again, we need futuristic space lawyers to figure out at what point is something a good-natured prank and when is it used for nefarious purposes. Yes. I thought Adam Silk had a great question. They asked, is there a material that's entirely opaque to all electromagnetic radiation or something that's entirely clear to all electromagnetic radiation? Oh, well, light is a form of electromagnetic wave, and then you've got infrared on the longer wavelength side, ultraviolet on the shorter wavelength side.

And you go past ultraviolet, you get into X-rays, you go past infrared, and you get eventually into radio waves with longer wavelengths. And really, the answer, I think, as far as I know, is no, that pretty much everything is going to be somewhat transparent at some wavelengths and somewhat opaque at other wavelengths. Oh. Well, we know in particular if you go to X-ray, the X-ray regime, almost nothing stops X-rays. You need a lot of material like lead to block X-rays effectively, and that really relies on just having this ultra-dense material that an X-ray is guaranteed to interact with when

it's going through it. So we now rely on what we know from the periodic table of elements, and lead is this dense material that we use. But in the future, there may be an even better metamaterial that relies on some unique structure to deflect certain rays, and just in case someone actually makes X-ray glasses and tries to take a gander at your heiny. So not cool, future creeps. Don't.

A couple more listener questions, if it's OK, we had such good ones, I love those. Oh, yeah. I got nothing else going on right now. Good. I love it. Kayla C. wants to bust a little flimflam, as we say, wants to know, what do people most misunderstand about light? Well, I can give you a recent example that's very helpful.

There was a recent viral TikTok video that all sorts of people duplicated where they put a sheet of paper against a mirror. Yes! Oh, the egg! The egg! Yeah. OK, thank you. I'm so sorry I'm freaking out, but OK, explain, Professor.

OK. Well, yeah, so the idea is that you put a sheet of paper on the mirror, and then you have like an egg or some other object behind it. And the thinking of the people that made these videos is, if you go to the side of the mirror now, you can see the egg in the mirror. People said, well, how can you see the egg if the piece of paper is blocking it? And I actually wrote a little blog post about this, too. And first of all, I like to say, OK, how do people think that it works?

How do people think that a mirror works? And I'm guessing people think that somehow the light is kind of directly projecting into the mirror and that somehow inside the mirror, and that gives us the image. But what's really happening is the mirror is just reflecting light rays that come off of an object. So what you're seeing is the light rays that were reflected off of the egg hit the mirror and then bounce to your eye. If you're standing right in front of the sheet of paper and the egg, of course, you can't

see anything because the sheet's blocking it. It's only when you go to the side. And if you go far enough to the side, there are light rays that are coming off of the egg that are still hitting the mirror and able to go to your eye. So to answer the original question, I guess one of the things that I would love for people to think about in optics is that you really should, at a basic level, the way light and optics works is that kind of you follow these straight line trajectories. The light is emitted from a light source in all directions.

It bounces off of objects. It reflects off of mirrors. And that's the way images are formed is from those straight line. And then if it goes through a lens bending path of light rays. Oh, thank you for elucidating that. No light pun intended. Yeah. So thank you.

One thing I like to say about that, a lot of people were saying, well, this is really silly that people don't know this. And I countered and said, this is actually really nice. Here are some people that saw something. They said, I do not understand how this works. And they shared it with everybody else. And all these other people said, how does this work? And that's exactly what science is supposed to be about.

That's wonderful. And sometimes the items and the things that you take for granted the most can have the most complex answers you never know. And if you don't ask and you don't investigate, you'll just, you'll never look in the mirror the same. Yeah, that reminds me of a little anecdote about my own life because we all have things like that that have been staring us in the face forever and we've just never thought about them.

And for me, it was probably a decade ago. So I was in my 40s and I was putting away the cord for my vacuum and I was wrapping it around the two hooks that you wrap the cord on. And I was thinking to myself, why does the top hook of this vacuum cord thing turn? Because when it turns, the vacuum cord just falls right off. I never thought about that. I'm sure everybody and probably already listening to has a moment like that where there's something like really, really obvious that's been staring you in the face forever.

And it was only when, you know, you just thought about it the right way or somebody pointed it out that you suddenly went, oh, the other good example of that is, you know, in your car, there's a little image of the gas pump and there's a little arrow to the left or the right. And probably most people make it to their 30s or older before somebody finally explains to them that little arrow tells you which side the gas cap is on. No, why doesn't anyone tell us that? If you are buying a car, this should be like, and here's the arrow that shows you where

the gas cap. Thank you so much. Got it. It's like these things you just have to learn so incrementally. Now, one question so many people wanted to know, Lexi back, David, Demi Uichu and Connie Connie Bobani in Sage Scarberry, who has great names worth. If Dr. Gerber could be invisible, what would you do with your superpower? Would you play tricks on your cats?

Oh, yeah, that would probably be the most common thing, though, not too much because I don't like to be too mean to my cats and they have their limits of what they're willing to put up with. You know, I don't know that I would have any sinister outlook. One thing that would be interesting to try, and this is purely from a scientific point of view, would be how easy would it be to get around in a city if you were invisible? So many science fiction stories like H.G. Wells is the invisible man and others make that very clear point that the characters make themselves invisible and then they go

out in public and find it really hard to get around because nobody's looking out for them. And it would be really interesting to be able to test that in practice. Would it be super hard to go into a city and move around without constantly getting bumped into? It's hard to, hard to predict one way or the other how easy it would be without testing it. Gosh, can you imagine just Manhattan at rush hour, how many people would hip check you and then not know?

Because even if you're invisible, you're still going to make a solid impact of matter. So you'd be hitting people left and right. People could step on you. Excuse me. Excuse me. Interesting. I'm trying to think what I would do if I were invisible. I think, I mean, my aspirations are so weak.

I'm like, I'd sneak into the movies. You know what? I could probably sneak into the movies as it is right now. I'd probably feel bad and like leave a 20 on the cash register. A lot of the science fiction imaginings of invisibility are all for very sinister type purposes. And I would feel guilty about doing most of those. Right.

Right. Maybe like, um, sneaking on the side stage of a concert I really wanted to see as long as I didn't do anything creepy, you know, just like get better tickets for something. Or even heck, even just being able to go on stage during the concert and get the experience of what is it like to be facing that crowd? That's true. You could dance up there as much as you wanted. No one would know unless you accidentally hip-check the bassist.

In which case you have a problem. But last questions I always ask, worst thing about your job. Is it a frustration? Is there something about emails, lab, anything petty to giant? Really it tends to be just all the paperwork, paperwork for funding to actually do the work to make sure that my students get supported. The unending amount of paperwork, when all I really want to just do is sit around and play with mathematical equations and figure out cool stuff.

But you become a professor and suddenly you've got to worry about how everything gets done. Right. And do you have any good advice? How to approach academia for your student or how to find what you're really kind of excited about? Yeah. The one thing I tell most students, including my own graduate students, and I'm not sure they ever listen to me, is read everything.

Read stuff in your field. Read stuff out of your field. Read stuff in a completely different field. And that's a really great way to find what sort of problems interest you. It's a great way to just get used to the way that scientists write and to learn the jargon. And also, you often can learn really exciting new approaches to things by studying outside of your immediate field. We get so focused in our little fields of study that often the answer that we're looking

for is just right next door. Somebody's doing something in a subfield different from yours. And they've already got the answer, and neither of you know it. And you know, I learned this from Adam Becker, who we met at Saicamp Camp II. He said when he was writing his book, he would do Pomodoro and he would go read fiction in between and just to give his brain a break and to not withhold other sources of information or inspiration from your work that it ends up really helping you. But sometimes we're so focused on getting the job done that we don't give ourselves

that. And I say 100% agree because I say the same thing. I have a lot of additional hobbies that I'm involved in. And I say it's not only just fun and good for me, it's also very practical because it also helps me think about how other people are thinking about problems and solving problems. That's so good to hear from someone who's so smart and accomplished. Oh, thank you. What about your favorite thing about light, about invisibility, about what you do?

I do just enjoy the thrill of exploring something new, trying a crazy new idea that shouldn't work at all and then finding that it works. And also now that I think about it, since I have a whole book, I really love studying the history of science. I love seeing how people figured out the things that they figured out, which is often very different from the way we learn it in our introductory classes. For sure. I feel like we're so used to science.

They know things and they know things and don't question it. And then we find out that there's so much trial and error and people looking for one thing and finding something else and feuds and fights at conferences. It's so exciting. And your book is so, I'm so thrilled for you. The chapters are so fun. Science meets fiction, invisible rays, invisible monsters. What a book.

It's so great to talk to someone who is not only an authority on this, but someone who also can explain this to a lay audience in a way that's really fun. Well, thank you. And I guess I would say I can't wait to see you again, but who knows if I'm even going to see you? You might be there right next to me. You'll be the first to know if I figure it all out. Yes, please.

Send me a text. So ask wonderful people, wonder filled questions, because honestly, they love explaining what they love. It never fails. And you can find Dr. Greg Gabor online at the Handel Skulls and the Stars. That's also the name of his blog. And all of those are linked in the show notes and on my website. And if you appreciated this episode, I encourage you to find Dr. Gabor online and let him know.

He is really great and deserves all the praise for making us see the light differently. So big hugs to him. Thanks for being on. And find us at oligies on Twitter or Instagram. I'm Allie Ward on both. Allie has just one L. Also, I'm on TikTok at alley underscore oligies and I'm on the blue sky thing. Small oligies are shorter, kid friendly episodes that are free of filth and they're safe for

all ages. Those are linked in the show notes or just go to oligies.com. Thank you, Zeke Rodriguez-Thomas and Mercedes-Maitland for editing those. Merch is available at oligiesmerch.com. Thank you, Susan Hale for managing that. And tag at oligiesmerch and we'll repost your photos of you and your merch. Noelle Dilworth Handel Scheduling. Erin Talbert admits the oligies podcast Facebook group.

Transcripts are by Emily White, the wordery producer and editor. Jared Sleeper makes these episodes. And this week on his social media, he posted a really lovely behind the scenes video of reading reviews. So enjoy that. Go to sleeper, find him. And our lead editor is the lovely Mercedes-Maitland of Maitland Audio who makes our audio worries vanish each week.

Nick Thorburn made the theme music and if you stick around until the end of the episode, I tell you a secret. And this week, it's that I was thinking that not only do we never realize how cute we are in the moment, we always look back on pictures or like, I was so cute. I was so cute. So right now you're so cute. No matter what picture you look back, you're going to be like, so cute. Not only that, but you're living in yesteryear.

You just don't know it yet. So not only are you so cute, but you're also wearing entirely impeccable vintage. In the future, it'll be vintage. Look at you right now, completely perfect vintage outfit wherever you're sitting is period to the time, which is now. So just think in the future, a picture of exactly what you're doing right now would be so cherished. So just like, I guess, live in that and just be like, Oh, what a time.

How charming. Okay. Bye bye. That's what we do Troy, incredible, invisible, unbelievable things.