SciShow Tangents - Eyeballs

Episode Date: September 15, 2020

Jeepers creepers, today we’re talking about peepers!  I can't come up with anything that would really add to the above description of the episode, but I also feel like I owe you guys more than that... so hey, what's up? Excited for Halloween? Watching any good shows? I'm sort of out of shows...  Follow us on Twitter @SciShowTangents, where we’ll tweet out topics for upcoming episodes and you can ask the science couch questions!  While you're at it, check out the Tangents crew on Twitter: Stefan: @itsmestefanchin Ceri: @ceriley Sam: @slamschultz Hank: @hankgreen If you want to learn more about any of our main topics, check out these links: [Truth or Fail] Bat Eyeshttps://www.vice.com/en_us/article/78kwdz/bats-crash-into-each-other-all-the-time-high-speed-cameras-reveal Guitarfish Eyeshttps://www.smithsonianmag.com/smart-news/instead-eyelids-fish-has-special-muscles-retract-its-eyeball-180957005/ https://ocean.si.edu/ocean-life/sharks-rays/sharks#:~:text=Sharks%20have%20eyelids%2C%20but%20they,damage%20when%20fighting%20or%20feeding.&text=In%20addition%2C%20some%20species%20have,the%20eye%20in%20dicey%20situations. Goat Eyeshttps://www.npr.org/sections/health-shots/2015/08/07/430149677/eye-shapes-of-the-animal-world-hint-at-differences-in-our-lifestyles [Fact Off] Glowing Contactshttps://www.caltech.edu/about/news/glowing-contact-lens-could-prevent-leading-cause-blindness-82050https://orionvisiongroup.com/blog/glow-in-the-dark-contact-treatment-diabetic-retinopathy/#:~:text=Diabetic%20Retinopathy%20%E2%80%93%20The%20Facts,the%20precursor%20to%20nerve%20death. Cockeyed squidshttps://today.duke.edu/2017/02/mismatched-eyes-help-squid-survive-ocean%E2%80%99s-twilight-zonehttps://royalsocietypublishing.org/doi/10.1098/rstb.2016.0069https://www.discovermagazine.com/planet-earth/this-squid-gives-better-side-eye-than-youhttps://www.scientificamerican.com/article/how-does-someone-get-two/ [Ask the Science Couch] Eye shapeshttps://www.mentalfloss.com/article/90509/13-furry-facts-about-pallass-cathttps://advances.sciencemag.org/content/1/7/e1500391https://www.npr.org/sections/health-shots/2015/08/07/430149677/eye-shapes-of-the-animal-world-hint-at-differences-in-our-lifestyles [Butt One More Thing] Cow butt eyehttps://www.smithsonianmag.com/smart-news/painting-eyes-cow-butts-could-save-cow-and-lion-lives-180975601/https://www.mentalfloss.com/article/627983/save-cow-from-predators-paint-eyes-on-its-butt

Hello and welcome to SciShow Tangents, the lightly competitive knowledge showcase starring some of the geniuses that make the YouTube series SciShow happen. We're joined, as always, this week by Stefan Chen. Have you ever been to a monster truck rally? No. Oh, come on. It's so good. I've never been to any of the, like, demolition derby, monster truck. Oh, my gosh.

The moment this lockdown ends, we're finding a demolition derby, and we'll take all of you to it. Demolition derbies are so fun. They are stupid fun. I went and I was ready to enjoy it ironically. And then I was like, oh no, this is art. Yeah. What's your tagline, Stefan?

68 and freezing. Sam Schultz has also joined us today. Sam, what is the number one top cartoon? Oh, Batman the Animated Series. That's the best cartoon show ever made, I think. And Avatar the Last Airbender are tied for the best cartoon shows ever made. Avatar the Last Airbender might be the best television show ever made. And what's your tagline?

It's five o'clock somewhere. I'd like this song better if it were posed as a question. Sari Reilly has also joined us. And Sari, what's your tagline? It just got very dark in here. That's great. It's a really good tagline, but also it seems like it actually did. And I'm Hank Green, and my tagline is, you can't really count on the sun.

Every week here on SciShow Tangents, we get together to try to one-up a maze and delight each other with science facts. We're playing for glory, but we're also keeping score and we award sandbox from week to week. We do everything we can to stay on topic, but judging by the intro of this podcast, we won't always be great at that. So if the team deems you tangent unworthy, we'll force you to give up one of your sandbox. So tangent with care, especially about motorsports. Now, as always, we introduced this week's topic with the traditional science poem this week for the first time in a while, it feels like, from me. This poem is entitled Daydream.

It has a title. Who's that actor getting out of that Mercedes Benz? I don't know, but you saw it using an anatomical lens. Oh, he's that Australian. I think his name is Russell. I can't see him, but you're doing it with your ciliary muscle. I wonder how old he is. He looks like he could be a boomer.

I don't know, but I know that his image travels through your aqueous humor. And who's that with him from Wonder Woman? Ah, what a gal. You'd have a much harder time seeing her without your Schlem's canal. She's on ice skates.

She just did a sow cow. I think it was quadruple. I didn't see it, but you only saw it with the help of a pupil. And Russell, now he's walking an animal. It looks like some kind of chimera. I don't know what it is, but neither would you if you didn't have a sclera. Oh, and now

Gal, she looks so cold. She could have hypothermia. Maybe so, and maybe not, but you're seeing it with a cornea. That one was a stretch. I'm starting to think that you can't see anything at all. That's true,

my friend. I don't exist. You're staring at a wall. Oh. Twisted it around at the end there. Uh-huh.

Who on earth is the Australian guy named Russell? Russell Crowe from Gladiator. Oh. Yeah. I assume there's

a specific movie, and does it have to do with the topic or? No, it's just a daydream. Or just that we're watching a movie. No, they're just like thinking. It's not even a movie, Stefan. No. We've left Stefan behind. I haven't seen a lot of movies.

I thought maybe there was like a movie that was called Eyeballs. Starring Russell Crowe and Gal Gadot. Yeah. It's especially great because their names rhyme, which was not intentional. Which didn't even rhyme them in the poem, right? Did not, did not. Half of those parts of the eye I've never heard of.

Yeah, Schlem's canal, that was new for me. Yeah, what the hell is that? It moves aqueous humor around your eye, which apparently is important for some reason. Sounds important. Yeah. So our topic for the day is eyeballs. I think it's specifically eyeballs.

So if anybody comes to me with eye spot facts, then you're in trouble. But we'll see. We'll see when we get there. Sari, what is an eyeball? So an eyeball, I guess to distinguish it from an eye spot, is a specialized organ of the visual system. So instead of just like a specialized patch of cells, it has specialized beyond that to be like such a cluster of cells that they're like, that's a different tissue. That's a ball. In fact,

they don't have to be balls though. They can be like discs or football. Owls have like tubes or something right yeah i think they're like long in some way do compound eyes count i think a compound lens is an eye like an eye that's a ball but it's not an eyeball well colloquially speak colloquially colloquially speak don't you dare edit that out either I think eye spots are eyeballs I think compound eyes are eyeballs what slugs have on top of their little things those are eyeballs

Sam thinks it's all eyeballs to me I disagree but eyes they see there are things that see that are ball shaped do you have

an etymology of eyeball I don't know where the ball part comes from and the eye part. I know where the word eyeball comes from. I didn't look up eyeball specifically. There wasn't an etymology dictionary, but I is from the Proto-Indo-European root OKW. Not sure how you pronounce it. In my it's like the cardi v okur thing that i can't do with my mouth it's like one of those things where humans have had eyes and so we've had to describe them in some way so it's always one and so yeah okw means to see and then the germanic forms evolved from there to from like algo or oog or auga.

Any combination of like G's, A's, O's, and then eventually made its way to I. I think people used to think that Shakespeare invented the word eyeball, but I don't think, I think they found an older thing that predated him just barely. But it's from about that time. Whenever that time was, I have no idea. And now I think it's time for... One of our panelists has brought three science facts for our education and enjoyment, but only one of those facts is real.

The rest of us have to figure out either by deduction or wild guess, which is the true fact. And if we do, we get a Sam Buck. If we don't, then the presenter, who is Sam this week, gets a Sam buck. You can play along at home at twitter.com slash SciShow Tangents, but don't click until you've heard all the facts. Sam, what are

your facts for us today? So if you have eyes, you're pretty familiar with the way that eyes move. They go up and down and left and right, you know, pretty much like on the same axis. But there are some animals out there that can move their eyes in weirder and more fun ways than people can. So which of these is true? Number one, many sharks and rays have eyelids that they can close to protect their eyes when they're attacking prey.

But the guitarfish, which is a ray that basically looks just like a flat shark, does things a little differently. It has a muscle in its head that can yank its eyeballs into its skull. Number two, bats spend pretty much all their time that they aren't flying around hanging upside down, which means that they're always seeing the world upside down. But the bulldog bat family has developed a special trick, eyes that can rotate around so that everything is right side up. Scientists have found that this adaptation helps them get oriented faster when taking flight, reducing midair collisions. No fucking way, but yeah, go ahead,

keep going. Number three, the Spinosaurus had many adaptations that lead researchers to believe that's the only dinosaur able to swim, but some other researchers believe it has another unique distinction. It's the only dinosaur with independent eye movement. It might have had eye structure similar to a chameleon that both protected much of the eye when it was underwater and allowed it to track multiple swimming targets at once. Ooh, okay, I like them. So we've got our three facts.

The guitarfish can use muscles that pull its eyes inside its skull. The bulldog bat can rotate their eyes to maintain orientation when hanging upside down, or the Spinosaurus has skull structures that suggest they had independent eye movement. I've already said my piece about the bat. Well, maybe there's like, they put little lead weights in there,

so it's always right side up. Oh, yeah, yeah, yeah. I like that. It's like a gyroscope in nature. I can absolutely believe that there's something weird out there where it's like, oh, it just rotates around. It's in fluid, and the only connection is something that we've never seen before. We're using it for space stations now. we're using it for space stations now.

And I really want them when they're flying to like do a barrel roll, but their eyes stay in the same orientation while they spin around. Their eyes don't necessarily stay in the same orientation. They can move the orientation. Right, right. It doesn't just float there like one of those globey things that you like spin,

but the globe stays in the same place. We've got guitar fish. This seems perfectly reasonable that a fish would be able to yank its eyes into its skull. Where's the room for it, though? We don't have any room in our skull for eyes to be sucked in. Well, we're not guitar fish.

Okay. Fish got empty heads, man. There's nothing in there. There's nothing in there. Siri, have you ever tried to yank your eyes into your head? No. Okay, try. Look at, I need to see you. Look at me.

I'm trying to yank your eyes into your head. I just want to see what it looks like. No. Don't do it. Because what if you do it? No, I'm not going to. I think if you plugged your nose up real good and snorted really hard at the same time.

That's going to blow my eyes out. Maybe something will happen. All right, Sam, you seem to have all the, like you've got it figured out. Why don't you do it? Because I know I could and I couldn't get him back out if I did. That's too powerful.

Too powerful. Okay, I'm going to do it. Oh, he did it. Horrible. What? All right. And then our last fact also seemed really cool. The Spinosaurus skull having structures.

So it had chameleon eyes. And that seems like that would be interesting. Because the surprising thing about dinosaurs we were like figure out these stupid little amazing things by looking at

like muscle connection points and we're like oh the only reason that would be there is if they had chameleon eyes and I could see it being a weird adaptation when eyes were first

I don't know early on earlier on in eye development where it was like of course it would come up more than once that it's cool to watch prey in more than one place

because you're hungry and you want to protect yourself and find more things to eat. I'm going for the alligator fish. The guitar fish? The guitar fish, yeah, that one. You know, alligators and guitars, they look a lot alike. I will also go for the guitar fish

whoa yes oh no i was leaning towards guitar fish but do we want to go all in all right let's do it let's make a gamble everyone on guitar fish we're all in baby that's so scary so now it is time for you to go vote at twitter.com slash SciShow Tangents and to see what you pick. Do you vote with us, with Guitar Fish, or do you vote your own independent way? Free yourself from our tyranny. Sam, what is the true fact?

Well, look, okay, it's the Guitar Fish. Oh, God. That was scary. So the Guitar Fish can suck both its eyes into its head. It has one long muscle that runs along the bottom of its skull and hooks up to the muscles around its two eyes. And when it's about to get a crab or whatever they eat, crabs are one of the things they eat,

it's going to dive into the dirt. It sucks its eyes up into its head and gets a crab. And other rays and sharks do not do this. They just have like a protective eyelid that goes over their eyeballs. But they're looking at other ones right now actually to see if maybe they do do it. And they also have a protective lid, but the guitarfish don't have a lid. They don't have a lid. They just suck their eye in.

As far as I could tell, they just suck their eye in. It can go two inches. It goes two inches into their head. Wow, that's far. It seems quite far, yeah. Does their skin just kind of pucker over it? Is that what protects it? Yeah, it looks weird.

Yeah. There will be a picture of it in the sources. I'm looking at it right now, and I'm getting a physiological vibe from it. It's got a butthole vibe. There's a clenchiness to it. The bat thing I made up. It would be cool if bats could do it. It seems like it would be really useful for them.

But goats and sheep sort of can move their eyeballs on that different axis than we can. They have eyes with horizontal pupils, obviously, so they're good at panoramic vision. But when they bend their heads down to grays, they can move their eyes up to 50 degrees

to match the horizon to keep the panorama going so they're not just looking at the sky and the dirt. And bats do smack into each other a lot when they're flying out in their big groups at night, but they're generally fine. They recover from it and do not die from smacking into each other or anything. And Spinosaurus was really the only dinosaur

that they think could properly swim. It had big flat feet and super dense bones that let it be able to submerge itself. And I guess other dinosaurs maybe had two porous of bones and would float or something like that. And its nostrils are set really far back on its head, so it could keep them above water, but it did not have special eyes

as far as they know. Maybe they did. That's true. There's no way to actually prove I'm wrong. Oh, boy. We went all in. Sam, I'm so sorry. No, that's okay. I mean, you needed the point. Stefan and Sari are still locked in a tie, I'm so sorry. No, that's okay. I mean, you needed the point.

I don't know. Stefan and Sari are still locked in a tie, I think. Alright. Everybody, we're going to go for a short break, and then it'll be time for the Fact Off! Welcome back, everybody. We've got Stefan and Sari tied with one, Sam with none, and me in the lead for once with two points. But I will not end in the lead because, well, because I don't have any more opportunities to get points.

Because now it is time for Stefan versus Sari in the fact off. Two panelists have brought science facts present to the others in an attempt to blow our minds. And we get a sandbuck to award to the fact that we like the most. And to discover who's going to go first, we're going to answer a trivia question. Of the six million cones in the human retina, approximately how many of them are red cones? You can say a number or you can say a percentage.

But the percentage would probably be easier. I'm going to say one-fifth. One-fifth of the cones. That's interesting. This question only makes sense if it's not split evenly. But I sort of, I don't know, red seems more important to me. It's also my favorite color, I think. So

I'll say two-fifths. Hey, we didn't say fractions that were... Forty percent! Forty percent! Yeah, twenty percent. We can do quick math. Point two. You're making this so hard for us. No, I can do fractions.

Now, the actual answer is two-thirds-ish, 64%. Whoa! What? Yeah. Yeah, red Z is the color of Z. Red is better. Yeah. I thought it was green.

I thought we were all in on green. No, green's the hardest to see, I think. The terrible news is that I don't know why. I don't know why there are more red drones. I just know that there are. And that means that Stefan gets to go first or choose who goes first. Yeah, sure.

I'll go first. Let's do it. Okay. So diabetes is a disease and the main long-term complication with diabetes is that your blood vessels get damaged. This includes the blood vessels in your eyeballs. And so over time, this can lead to diabetic retinopathy, which is also

known as creeping blindness, because as the blood vessels are damaged, there's less blood flow. And so you get less oxygen to the nerve cells in your retina. So they eventually die. Apparently, the body tries to regrow the blood vessels, but it does a bad job and that makes everything worse. So the two things that it seems like you can try to do is inject medicine into the eyeball that inhibits that blood vessel growth, or you can use a laser to burn away cells on the peripheral parts of the retina, and that reduces the overall oxygen needs of the eyeball so that the limited resources that do make it up there can get focused on the more important cells that are at the center of the retina.

And we suspect that a lot of the damage that's happening in the eye happens at night when we're sleeping and everything is dark because we have the rod cells and the cone cells. Rod cells work better in dimmer light, and that's how we have our low light vision. And so when it's dark, the rod cell's oxygen needs double. And so it needs more oxygen. It's not getting it more damage. So there's this idea that if we could keep the rods from experiencing darkness while people are sleeping, we could keep the rods from experiencing darkness

while people are sleeping, we could prevent them from needing more oxygen and prevent that damage. And so previously we had tried using sleep masks that shine lights into people's eyes. This is great. We're going to save their vision, but also we're just like actual torture. to save their vision, but also we're just like actual torture. Yes. Yes. Unsurprisingly, people found it distracting to have lights showing a shine to their eyes while they're trying to sleep. And also, I guess our eyes roll back once we're asleep. And so like the retina is not even receiving that light anyways at that point. So Colin Cook, Caltech graduate, came up with this idea to use glowing contact lenses to achieve that same effect, but without needing to do anything invasive or painful or distracting. It's a standard contact lens, but then it has a circle of tiny tritium-filled vials. And so that's like a radioactive version of hydrogen gas.

And then there's a phosphorescent coating on these vials. So they glow. They're very tiny. Each vial is like the thickness of a few human hairs. And they're arranged in this circle. But the circle is large enough. And because it's right up against your eye, it's big enough that while you're awake, the circle is outside your field of view. So you don't see it glowing because it's glowing all the time. But then when it gets dark and your pupils dilate, then they let in the light from this glowing circle. Oh my God. And that stimulates the rods. And so their energy needs don't jump up. And they also noted that because this light source is moving with your eye, it's a very like constant thing. And our brain

is good at like tuning those kinds of things out. So after a while, you don't even really consciously register the light. And so it doesn't distract you from falling asleep. And in the testing they've done so far, they found that the rod activity was reduced by 90% with people who are wearing the contacts. We don't know yet if this will actually translate to reducing the blindness, but that's like the next steps. But it's just seemed like such a cool thing. Tritium does release ionizing radiation, which is why it is able to make this stuff phosphorous.

I don't know if I want to put, it's not very much, I understand. They're tiny vials. I don't know if I want to put ionizing radiation on my literal eyeball. Yeah, it feels like that wouldn't help with the damage in the long term yeah some some extra uh dna damage in some cells might just does pop off and does seem worrying i don't want to get eyeball cancer but and it also occurs to me that this would be a good way to prove out this theory at the very least, that the problem is the overactivity in these cells while there's no light, because they work harder when there's no light and need more oxygen. Yeah, it seems like we just haven't had a good way to actually like get people to comply with whatever like protocol they're, you know.

like get people to comply with whatever like protocol they're, you know, it, it also seems to me like wild that our bodies expend more energy during darkness. Like it's, it's harder to not receive information than to receive information for those cells. They're just like,

Oh, Oh shit. It's dark. I'm going to try really hard to see, but it's the darkness of your own eyes being closed. Even though like, I know that your eyes are going to be closed for like eight hours a day. I'm still going to try

really hard the whole time. That's where they get their exercise. I guess so. Yeah, it's the only part of your body that exercises while you sleep. If I can capture that from my freaking pecs. Okay. I love that fact. And I love that this is a real thing that exists and that they've used.

Alright, Sari, what do you have for us? So nature is full of symmetry and we also really like recognizing symmetry when we see it, whether it's the bilateral symmetry of our bodies or radial symmetry in a snowflake. I guess I have a tangent in here already. I think this is why we have such a fascination

with asymmetrical things like heterochromia iridium when a human or a dog or some other animal has two different colored irises, like a brown or a dog or some other animal has two different colored irises, like a brown eye and a blue eye. And we're like, ooh, asymmetrical. That's cool. So that eye phenomenon is just caused by a genetic or a traumatic variation in pigment for some reason. But there is a much more extreme asymmetrical eye situation in the animal kingdom. And let me introduce you to the cockeyed squid. They live in the animal kingdom. And let me introduce you to the cockeyed squid. They live in the mesopelagic part of the sea,

so 200 to 1,000 meters deep. Not the pitch black darkest, but not exactly bright from sunlight. And to survive here, they have two radically different eyes. One is a small eye with a clear lens, so it looks black when we look into it. It's like fairly standard for a squid eye.

But the other one is comparatively giant and bulbous with a big yellow lens. And in a 2017 paper, Kate Thomas of Duke University did studies on 30 years of 152 or so sightings of Histiotuthis heteropsis, which is one of the species of the cockeyed squid. And they did some simulations of these two different eyes to figure out why they are so radically different. So the squid swims along in what looks like an upside-down orientation to us with, like, tentacles faced towards the surface

so that its eyes are oriented in different directions. And the small eye almost always points downwards and scans the deeper ocean for any flashes of bioluminescence in the otherwise dark water. And the size of the eye doesn't really matter here, just as long as you have some sort of vision thing, a light-sensing organ to catch a flash coming from below. And the big yellow eye almost always points up towards sunlight to look for the silhouettes of anything swimming above it. And in that case, the increased size greatly helps the amount of light the eye can detect, and especially the size combined with the yellow pigmentation helps it tell the difference between

just ambient light up there and reflective camouflage from organisms like lanternfish and shrimp and other things that it wants to eat. And so the researchers are looking at the squid and are like, why did you evolve two eyes? Everything else is symmetrical. And their only guess is that it's biologically taxing to devote energy to two giant yellow eyes,

which presumably could also look down and see small flashes of light. And so instead of having both eye adaptations, something weird genetically flipped and it has two distinct eye adaptations so that it only has to put energy into specializing one and the other one can can be boring and relatively low energy for a vision organ. And that's just weird, because there aren't many asymmetrical animals in nature, but the squid is like, I got you. Apparently, there is a lot of eye diversity in this layer of the ocean, though,

because the light situation is so varied. So this is one of the most eye diverse places in the ocean. You're going to have a lot of weird eyes here. It looks diseased. Yeah, a couple pictures do a really good job of showing how big and weird the big eye is. Did squids develop eyeballs? They must have. Yeah, separately from us.

It would have had to be so long ago where we developed eyes. We are not closely related to squids. Invertebrates, invertebrates. Yeah. Squids evolved from like clams. We did not evolve from clams. We all got there in eyes except for plants. What the heck's wrong with plants?

Plants can detect light in some ways. Yeah, they don't got balls though. They don't got balls. It's true. Steph, thank you for making that clear. All right. Sam, do you want to vote with me on what your favorite fact is? Three, two, one.

Stefan. Oh. Interesting. Oh my gosh, how are the turntables? Now it's time to ask the science couch where we've got listener questions for our couch of finely honed scientific minds. It's from at FoxNarutoMax.

Why do we only have the regular circle pupils? finely honed scientific minds. It's from at Fox, Naruto Max. Why do we only have the regular circle pupils? I want pupils like cats or like frogs. Is that so hard? There are different hypotheses as far as people shapes, but it seems like a lot of people refer back to this one 2015 paper in which researchers studied 214 terrestrial animals. So did not count the fishes and the sucking into your eye guitar fish or the cockeyed squids of the world and sorted different eye shapes and how they got their food. So there's like vertical eyes, circular eyes,

horizontal eyes, like we've been talking about. And then there's herbivorous animals, ambush predators, or active is the other category, which I'm guessing is just like actively scavenging. Maybe they're like omnivorous. And they found that there's a relationship between the ecological niche and the pupil shape. So herbivorous animals, so like the goats of the world, are more likely to have horizontal pupils. Diurnal predators, so you need more variation between day and night, have circular pupils. And then nocturnal or polyphasic sleeping during the day predators have vertical pupils. So it depends on what kinds of eye muscles you need to control light during the times of the day that you find food and so it's like your eyes specialize to when you're awake and so probably like the behavioral

cycles of of your circadian rhythms and and those patterns of like when when other members of your species are awake and when you can forage for food and when you can like be social and when you need rest then had an influence on eye shape because the muscles of your eye adapted to when you were awake well what is interesting to me is that it seems like if you're going to make a thing that can contract and expand circle is by far the easiest shape to make but it seems like that doesn't matter that much because vision is such an important sense that it's like, whatever works best, we will invest the evolutionary,

like the advantage will matter so that the different pupil shapes will happen. To the point where like goat pupils, I'm like, that doesn't seem possible. I don't understand physiologically how the muscles create a rectangle. Yeah. And like the advantage that these researchers think it gives, and I guess we can only simulate other eyes. We can't necessarily like see through them yet until we have a neural link technology so we can see inside their brains.

But the rectangular eyes help them get a more panoramic view, kind of like you were describing, Sam, where they can adjust for the horizon so they can watch out for predators that are around because they don't really need to see the grass so they can have a wider range of vision than us. Or in the case of cats, they can really laser focus in on what their prey is as they ambush or get a lot of light if they need to. Like if you've ever seen a cat in the dark, they're just like big eyes. Big eyes. They got those big eyes. It's really cute.

I like it when they get real dilated. But why do we only have the regular kind? It's because we're all related to each other And it was advantageous to have the regular kind. But I'm not saying to give up on your dreams, Naruto. I am saying to give up on your dreams. Unless you want like a colored contact lens or something like that. Especially for a ninja like Naruto. A cat eye would be much more useful, I think.

If you want to ask the Science Couch your question, you can follow us on Twitter at SciShowTangents, where we'll tweet out topics for upcoming episodes every week. Thank you to at Hemoglobed, at ActuallyGimli, and everybody else who tweeted us your questions this episode. Our followers and listeners have the best Twitter handle aesthetic. All right, that brings us to our Sandbox final scores. Sari has one. I've got

two. Stefan has three and Sam has nothing, which means that Sari and Stefan are still tied. Is that right? And also somehow Sam is now like almost all the way back there with me. Doing a really bad job. If you like this show and you want to help us out, it's easy to do that. You can leave us a review wherever you listen. That helps us know what you like about the show. And also, maybe

there's an algorithm somewhere that's like, mmm, delicious. Second, tweet out your favorite moment from the episode. And finally, if you want to show your love

for SciShow Tangents, just tell people about us. Thank you for joining us. I've been Hank Green. I've been Sari Reilly. I've been Stephen Chin. And I've been Sam Schultz. SciShow Tangents is a co-production of Complexly and the wonderful team at WNYC Studios.

It's created by all of us and produced by Caelan Hoffmeister and Sam Schultz, who edits a lot of these episodes along with Hiroko Matsushima. Our social media organizer is Paola Garcia Prieto. Our editorial assistant is Debuki Chakravarti. Our sound design is by Joseph Tunamedish. And we couldn't make any of this without our patrons on Patreon. Thank you. And remember, the mind is not a vessel to be filled, but a fire to be lighted.

But one more thing. Between 2015 and 2018, scientists in Botswana took 683 cows and painted eyes on their butts to see if they could deter predators. They compared the fates of these cows to a group that had cross marks painted on their butts and a group that remained completely unpainted and found that none of the butt eye group were killed by predators. Meanwhile, four of the cows with cross marks and 15 of the unmarked cows were eaten. The theory is that lions and other ambush predators see the eyes and think they've been spotted and so don't even try for it. I want booty shorts with eyes on the back of them. Yeah. And it's like, I know what you're doing. I know what you're doing.

I think that'd be great. That'd be my new favorite. Like, I'm going for a run outfit.