SciShow Tangents - Navigation

Episode Date: September 3, 2019

Wether it's a human trying to figure out the quickest way to the airport, a salmon returning to the waters where they were born, or a dog trying to figure out the perfect place to poop, almost everyliving thing uses some sort of innate or technological navigation system every day.  Follow us on Twitter @SciShowTangents, where we’ll tweet out topics for upcoming episodes and you can ask the science couch questions! If you want to learn more about any of our main topics, check out these links:[Truth or Fail]Orientation of mental maps:https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0135803Humans sensing magnetic fields:https://www.the-scientist.com/news-opinion/can-humans-sense-the-magnetic-field--65611[Fact Off]Marine chronometerhttp://www.jgiesen.de/LunarDistance/index.htmlhttps://www.jstor.org/stable/3087198?seq=1#page_scan_tab_contentshttps://timeandnavigation.si.edu/navigating-at-sea/longitude-problemhttps://archive.org/details/principlesmrhar00unkngoog/page/n22https://www.timeandwatches.com/p/the-detent-escapement-from-marine.htmlEtak navigator[Ask the Science Couch]Sunstone/calcite:https://www.sciencemag.org/news/2011/11/viking-sunstone-revealedhttps://arstechnica.com/science/2018/04/mysterious-sunstones-in-medieval-viking-texts-could-really-have-worked/https://royalsocietypublishing.org/doi/10.1098/rsos.172187https://www.nature.com/news/2011/110131/full/news.2011.58.htmlImage of calcite: https://www.sciencesource.com/Doc/TR1_WATERMARKED/6/9/f/3/SS2509789.jpg?d63642476241

Hello, and welcome to SciShow Tangents, that lightly competitive knowledge showcase starring some of the geniuses that make the YouTube series SciShow happen. I am joined, as always, by Stephan Chin. I'm here, as always. Hello. Hello. Great energy so far. Hey, guys. Stephan, what's your tagline? Homeward bound.

I wish I was. Hi, Sam. Sam Schultz is also here. How are you? Good. What's your tagline? Poetry crime. Poetry crime. Sam Schultz is also here. How are you? Good. What's your tagline? Poetry crime. Poetry crime? I did one of those this week. Sari Riley is also with us. Yep. How you doing? Still with us. Still with us. What's your tagline? Need a hug,

need a nap. That'd be nice. And I'm Hank Green. I've had a lovely week. Summertime is good and it's sort of like tailing off where it's nice and cool in the mornings and I love it. Summer here lasts three weeks. I know, it's quick. I hate it. But there hasn't been any bad fires

so we're all counting our blessings. Yeah, we're in bonus summertime now. And my tagline is pants but with pockets. What a concept. 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.

We do everything we can to stay on topic, but judging by previous conversations, we won't be great at that. So if the rest of us deems the tangent unworthy, we can force someone to give up a hank buck. So tangent with care. Now, as always, we introduce this week's topic with the traditional science poem this week from Sam Schultz. Whose woods these are, I think I know. I will check my Google Maps, though, just to see if I'm getting near the pizza place called Domino's. A satellite far up from here does through its little camera pier between the woods and frozen lake to show a path from which not to veer. My foot now removed from the brake, my car lurches forward with a shake. The only other sound's the beep of my phone telling me which left to take.

The woods are lovely, dark and deep, but I got two pizza pies real cheap. And miles to go before I eat. And miles to go before I eat. Yeah, that is definitely a poetry crime. Is Robert Frost going to burst out of the ground and get me oh goodness gracious our topic for the day is navigation which is how you get from a place to a different place and we've been doing that for a long time to try and not get lost and i think that like originally you were just like follow the river until the this landmark and then do this and go over two mountains and you'll be there.

But now we have all kinds of very complicated and excellent systems to do it with. So we get to talk. I don't know what we're going to talk about. Maybe we'll talk about old ways of doing it, new ways of doing it. But do we have a definition of what navigation is or do we all just sort of know what it is? I think you covered it. Just humans finding their way different places and gradually using more technology to do it.

So looking at landmarks, then looking at stars, looking at animals. Looking at animals? Yeah. Expand on that one. What does that mean? Well, animals can navigate.

Oh, like looking at how animals navigate. Not like, take a left at the rhino. It moves. As soon as you see a bird like five more steps

that's where the treasure is thank you by the way to June Fruit for suggesting this topic yeah thank you we have a whole list

of viewer topics that are going to be gone through in the next couple months and now it's time for Treasure Fame

one of our panelists has prepared three science facts but only one of them is real. The other panelists have to figure out either by deduction or wild guess which is the true fact. If we do, we get a Hank Buck. If we don't, Stefan will get our Hank Buck because you are the one giving us the fact. Hit me, brother. So in a city where the streets are aligned to cardinal directions, people seem to be fairly good at knowing which way is north. But which of these three things

is a real fact about a pedestrian's ability to orient themselves in a city where the streets are not aligned with cardinal directions? Number one, pedestrians asked to simply point towards north, had a hard time doing so because their guesses were based on the orientation of the roads, which again

were not aligned with the cardinal directions. And this happened even when they were indoors. Number two. That makes sense. Pedestrians who had been tested to have higher than normal sensitivity to magnetic fields were able to relatively accurately orient themselves northwards even when blindfolded and indoors. No.

Okay, keep going. That sounds like bullshit to me. Number three. The pedestrians were much better able to pick out cardinal directions when they were indoors and not being influenced by the roads nearby. And so they could just focus on their mental maps, which had a north up orientation. So the three facts we have, pedestrians have a hard time pointing north when they're in not north, south, east, west roads, even when they're inside. Two, people who have higher than normal sensitivity to magnetic fields. I'm not even going to finish that one. Three, pedestrians were better at picking out cardinal directions when they were inside without being distracted by the roads.

One and two seem completely possible to me. They seem like inverses of each other almost, right? Yeah, kind of. directions when they were inside without being distracted by the roads. One and two seem completely possible to me. They seem like inverses of each other almost, right? Yeah, kind of. Direction to me means nothing when I walk inside. That's north? That's north. He seems to be pointing north. I'm pointing north. I agree that that's north.

I mean, this building is in a north-south orientation, so it's pretty easy. I don't know. It's not my building. You don't picture... I picture a little me, kind of like a Google Maps person, dragged around by the color of their shirt being plopped down outside. So, like, if I were to walk upstairs, plopped down outside. Missoula doesn't have a north-south grid in this part of town, does it? Oh, yeah, I guess it does.

I think we're good right here. I'm pretty sure. The slant streets are no. Yeah, yeah. And then things get a little weird. There's a couple weird places. I'm not good at this because, like, I don't have a lot of experience with that.

In Florida, there were no grids at all. Oh, that doesn't surprise me. It was just wigglies. The roads were made by alligators just walking around. That's exactly right. Children on alligators. Back when they let the children run free. Yeah, the good old days.

They didn can keep them safe all the time it's put them on an alligator and had them right around slapped alligator's ass and it just runs off that's how they have fun do humans sense the magnetic field no i can't imagine humans being able to sense magnets but if stefan found the one study on the whole planet that's like we held a magnet near their brain and they jittered. Some animals can sense that, right? Yes. Definitely some animals can.

Can. Can any mammals? From my understanding, and there's probably a scientist out there that specifically studies magnetosensations. I don't even know what the word is in animals. I don't even know what the word is in animals. We have an understanding that some animals like birds use the magnetic field to navigate because if you remove that in some way, I don't know what experiments they do. They put like little tinfoil hats on them or something. Then they stop being able to navigate as well.

But we're not sure what mechanism enables them to like what in their cells is a magnetic particle or a magnetic reactive particle yeah they seem to like different organisms have like clusters of magnetite inside of them that they can find we don't know exactly how their cells are able to sense what those clusters of magnetite are doing but some bats do have that so okay it's a thing okay which is wild well i'm gonna go with the last. That's harder to tell inside which direction, right? Is that what it is? No, that's easier.

I'm going with the harder one. Okay. The first one? Yeah, because I can't do it. I'm going to go with pedestrians were better at picking out the cardinal directions inside when they weren't distracted by the roads, number three. I'm going to go with Sam and say it's harder because I'm also very directionally challenged. And so, like, anything will throw me off. It was the first one. It and say it's harder because I'm also very directionally challenged. And so like anything

will throw me off. It was the first one. It was. Is that the one I guessed? Yeah, yeah. Sam's like, which one is it? Sam is not only having a little trouble with where north is, but what is it? There have been previous studies that

sort of suggested that our mental maps are oriented north facing up. And it sort of made sense to me because like that's how we look at Google Maps and like video is so prevalent these days. Yeah. So that seemed intuitive. But the researchers in this study thought that that might be because the testing in previous studies was done in cities where the grids of the roads are aligned with the cardinal directions and so they specifically tested in a city where they were off axis and so they took participants to different like locations on the sidewalk around town and

like had them point north and most people were able to point within like a 180 degree semicircle this is like sort of more north than south. But it was kind of all over the place. And like the aggregate answers were like all around the circle. Like people were all over the place. But it looked like people were using the roads to orient themselves.

So it would be like, I know that Main Street kind of faces like northeast, southeast. So I'm going to orient myself that way and would be like, I know that Main Street kind of faces like Northeast, Southeast. So I'm going to orient myself that way and then turn left a little bit. And that's probably North. So that was the outside thing. And then inside,

they were told to imagine that they were facing in a particular direction and then indicate what direction a different landmark was from there. So like you're at the coffee shop facing the statue of Aristotle or whatever there's a statue of, and then in what direction is city hall or something like that, like known landmarks. And they found that people's guesses happened more quickly and were more

accurate when the initial orientation that you were asked to imagine was aligned with the roads, that you were asked to imagine was aligned with the roads, not aligned with cardinal directions. And so they think that people's maps are more aligned based on the roads, which sort of makes sense. But I thought that over time, living in an area and looking at Google Maps, you'd sort of get a sense of how your city's oriented. But it seemed like the length of time that people were living there didn't really matter. They gave people a questionnaire to see like how good their sense of direction was in general.

And like people who had a good sense of direction did slightly better, but it wasn't that big of an effect. That's what I want to know. Because people are always like, I'm so bad at direct. Or like, I have an amazing sense of, and I i'm like i bet the effect is small i bet the difference between somebody who's just a total loser and trying to get places and somebody like who or who thinks that about themselves it's like people who are like i'm tone deaf i'm like maybe but probably you just like aren't as you know you're like slightly worse slightly worse

than average yeah and the full picture of like how we navigate and orient is probably much more complicated and like we use different mental models in different situations for different tasks well i think for example with missoula i know north better because people refer to parts of missoula by the cardinal directions it's like this is the north side that's the south side but i don't think i could do like i lived in boston for four years but i don't think i could do that city the same way because no one calls things north southeast yeah yeah but it's also bonkers in boston it's also crazy what a what a disaster i was once navigating like my my gps was taking me through boston and it was like okay drive on this road and it just stopped like it

was never there it It had never connected. I was like looking at the place where I was like, I can see where you want me to go. It had invented a road that I thought should be there. Yeah, it was like a neighborhood slow road and it was like,

now turn right onto this extremely fast thing. Literally, there's a fence between you and it. I was very late for that meeting. The third one, which was like the opposite of the right answer, I just made late for that meeting. The third one, which was like the opposite of the right answer, I just made that up. But the magnetic field one,

there's a recent study where they, and they noted in the thing, and he was like, we know the results of this study are controversial. We controlled really, really well. It seems like there's an alpha wave response

in the brain to changing magnetic fields that were made to simulate the strength and movement of earth's magnetic field changes but super like no conclusions can be really drawn from this they maybe are seeing some alpha wave like they say they can reproduce it but like no sense that we could sense that or do anything with that. But I was like, that sounds like a good way to make a lie. Is there a dose-dependent response?

That's the first thing you got to look for as you increase the magnetic field and people's alpha waves get bigger. And then you're like, we've done it. We've determined that humans have another sense to stack on top of all the other ones. And then you're like, we've done it. We've determined that humans have another sense to stack on top of all the other ones.

And then you go from there and you're like, we can move things with our minds. Whoa. Just metal though, like magneto. Yeah.

I'm just thinking about how magneto works. Let's move on. Next up, we're going to take a short break and then it's time for the fact off.

Welcome back. Hank Buck total. Sarah, you've got one point. Sam has got two. Stefan's also got one. And I continue my streak of no points. Back on top, baby. Well, let's see if I can bring it back, everybody.

Now, during the fact off, where Sari and I will be competing to present the better facts to our other panelists here. So you each have a Hank Buck to award to us if you like our fact. And if you hate our fact, you can throw it into the fire that we have here at SciShow Tangent Studio. We always keep a fire going. You guys don't know about it. That's why you say that thing at the end, the fire to be lighted or whatever.

Yeah, that's the fire. You're talking about the literal fire. The literal fire. It's very dangerous. It's really difficult to keep control of inside. We have to have a very large fume hood. Anyway, so the person who's going to go first is the person who most recently got lost. Like a week and a half ago was the last time I felt lost.

Like actually. Like existentially. Oh, no, that's every day. But I felt lost navigation-wise. Yeah. But I felt lost navigation-wise because it was late at night, driving home from a national park in New York with three drunk people in the car. One of them was not you. Yeah, you were okay.

I was not, yes. And I had to navigate by myself in the dark. Oh, no. You were just hanging out drunk in a national park? There was a wedding. Oh, okay. Yeah, but I felt very stressed out the entire time and drove like 10 to 15 miles below the speed limit i was just in minneapolis and we were trying to go get breakfast and as occurs every time i walk out of the hotel you look at your phone and it's like

it's this way and you're like but i have no idea where i am on the map like which way is is left right which way is north south so i guess I would count that as lost. But you found your way. I did. Like, the last moment was lost, lost. Like, I was, like, worried. That's a totally different world. And, like, that so rarely happens.

Yeah. Yeah. I do feel like driving 15 miles below the speed limit is the hallmark of being stressed out and lost. Yeah. So maybe Sari wins in this situation. Okay. So that means, like, whatever like Who knows what it means? I'll just go.

So one of my favorite stories about navigational history is the longitude problem. Classy. Do you guys all know it? No. I have some vague idea that we could figure out one of latitude or longitude and we were like, yeah, we know this one, but we had no idea that we could figure out one of latitude or longitude.

And we were like, yeah, we know this one. But we had no idea where we were on Earth the other way. Well, you just said the whole fact. That's it. Okay, I'm going to dig it out now. So there's more details. Latitude is the one that's easy to figure out because you can look up at the sun at noon and use a tool called a sextant, which is like the triangly one, to reference like its angle to the horizon and like cross-reference that with a table to see where you are relative to the equator.

The table has the angle and the date. Yeah. All of these things include a lot of math, which I'm going to gloss over a little bit. Sounds great. So latitude, distance relative to the equator, like north and south, relatively easy to figure out because the sun has an angle to the horizon. That's predictable. Longitude, distance relative to the equator, like north and south, relatively easy to figure out because the sun has an angle to the horizon. That's predictable. Longitude, which is east to west, much harder to figure out because usually, like even on land, they would have to take multiple observations to figure out where they were relative to other things. I think the problem with the east to west navigation is that there are more changing elements in the sky relative to your position. And so like our time zones are changing now and

we have satellites that help us position ourselves. But if you were like a sailor on the ocean or walking across a continent, there aren't that many things that you could easily reference without doing a bunch of math to figure out where you were. And this was a big problem because then sailors would know where they were north or south but not know how close to land they were or things like that. And so they'd crash into rocks. There were a bunch of shipwrecks because of this, basically. Because people came up on land way too fast because they didn't realize where they were. They weren't using their damn eyes.

Yeah. Open your eyes. Sometimes the land is below the ground. Sometimes the clouds are in front of you. All right. So in 1714,

this became a big enough problem that the British government offered a cash prize. Oh, I love that. The Longitude Act, they passed on July 8th, 1714, and they offered awards up to 20,000 pounds, which is like millions of pounds in modern day. Depending on the accuracy of this method, they just like did an open call.

Can someone figure out how to do longitude? Yes. If it's good, we'll give you money. And so historically, astronomers were like the big people as far as navigation. Like this was a lot of the time where we would look at the stars, use those to navigate. And so Galileo and Halley, Halley? Yeah, sure. The comet guy?

The comet guy. Okay. Yes. Proposed different like celestial navigation strategies. I think Galileo was really into Jupiter's moons. Halley was into something else. And then other people suggested this too. But the most famous person who worked on this tool was a clockmaker named John Harrison, who is just like this.

They paint him as like this podunk country boy who is a carpenter who came up with a different idea that other people had experimented with called a marine chronometer, which is a clock that you would bring with you at sea. And so then you could look up and be like, oh, it's noon local time. What time does my clock say? And basically like calculate your time difference and that will let you know your longitude. So it's like reverse engineering time zone. As long as you can keep your clock going. Yeah. As long as you can keep your clock going.

Then you can be like, the sun is currently directly above my head, but my clock says it's one o'clock. So basically the same way that like time zones work you can be like i am a time zone away from that spot and so the problem with clocks before this time was they were pendulum clocks and like the way that clocks counted up seconds was a pendulum swinging back and forth on a boat yeah but if you bring that on a ship everything's gonna get messed up really quickly and so hook the dude who made Hook's Law, started experimenting with this.

Captain Hook? Not Captain Hook. It's Hook with an E. But Captain Hook liked clocks. Robert Hook was his name. Bob Hook. Bob. Not Captain Hook. That was Captain Hook's name.

Yeah. Bob. Canonically. They came up at some point with the idea of spring-loaded clocks, like the timekeeping element being a spring bouncing back and forth rather than a pendulum. Among other innovations, John Harrison came up with two very, very chunky clocks that would sit on a big table

that had a spring system to keep track of time. And they worked a little bit better than a pendulum clock at sea, but springs can still get shifted around with the flow of the waves and then he made one i think he included like some ball bearing systems and made it better like made the springs more enclosed and that was h3 and it was still a pretty big box and it did better but then he was like it's still not good enough this isn't gonna win me my money and he made a like a big pocket like imagine the size of your face sort of and i think that is like the size of the pocket watch he invented with a very small spring system and that

was h4 and that was the model that won him the longitude prize because it was accurate i think it lost less than a second per day which is really really accurate for the time so when you say marine chronometer it's just a clock right yeah it's you say marine chronometer, it's just a clock, right? Yeah, it's just a water clock. But like, it's a clock that works when it's on water. Yep. Yeah. So we had clocks before, but like clocks got better then. Like because we did this, everyone was like,

oh, actually that's better in a lot of ways. You can make it the size of your face. That's basically pocket size if you've got a really big pocket. When we had clocks back then, but they were all pendulum until they started to mess with how to tell time on the water, how to do this on the water. I think people were experimenting with non-pendulum

clocks before that. So, like, in my mind, Bob Hook is just super into springs. He probably was interested in them for a good physical reason. Yeah. But springs are dope. Yeah, he likes springs, and so I think he was looking into a spring clock without thinking about the the ocean problem right but john harrison and a couple other people who go

uncredited but didn't actually build the thing right um were some of the first people to apply a non-pendulum clock idea to a big problem that the world was facing with navigation but couldn't could you take a pendulum clock and put it on like a like a i don't know if gyroscopic is the right word but like a table that is like weighted at the bottom and like free floating so that it like is always does that make sense so as the waves bounce the ship around, the clock stays oriented right up and down? I think that even just moving the ship from side to side, like if you're tacking, like if you're going in a different direction,

it's going to pull on the pendulum to some extent. So you'd have to keep the clock exactly still. And if the clock is staying still, it's not on a ship. I guess it's my turn now. So, GPS, great and everything, but... I wrote a poem about it. In 1985, 15 years before GPS was available for civilian use,

you could buy and install a car navigation system called the eTAC Navigator that worked so well that the underlying techniques are still used in modern navigation software because the e-tac navigator didn't need gps it had something much cooler it had cassette tapes oh my god i love this so the e-tac navigator was a product of stan honey and nolan bushnell who set out to create a car navigation system that would require only a digital map, a compass, and some sensors. And with this system, the compass and sensors would keep track of the path that your car had gone, and then it would locate you based on that path inside of a map somewhere inside of this tape. So it would figure out where you are. It's a technique called map matching.

The navigator wouldn't give the turn-by-turn directions that we're used to this days, but it would see your location and the streets around you, and it would give you an arrow pointing in the general direction of where you want to go, like Crazy Taxi. That was, of course, very advanced at the time. This was the 1980s, so storing a whole bunch of digital map of a city in a way that would tolerate all the vibrations

and heat of a car was not a trivial problem, so they used special cassette tapes with polycarbonate shell that could handle temperatures up to 105 degrees Celsius. And each cassette would hold 3.5 megabytes of data. So if you wanted to have all of the Bay Area covered,

for example, you would have to get six tapes that would cover the entire Bay Area. And then you'd have to get out of your car and put a new one into wherever the thing was? No, it's inside the car with you. Okay, okay. Yeah.

So you're like, oh, I drove out of the area that I'm in. Switch the tape out. Like, you've got a new song. So, you're tired of hearing Salt-N-Pepa. You've got to switch out the tape to play, like, you know, your Tiffany album. Okay. So, you could, like, buy different sets, like, different map sets and, like, switch them out.

They were not cheap. So, the individual cassette tapes cost about $35. Jeez. But the system itself cost over $1,000 then, which would be like $3,000 now. And they did not sell very many. They sold like thousands of them. Okay. I have a lot of questions.

Okay. I only have one, actually. When you put a new tape in, how did you orient where you were? It oriented for you. How? How? So it knows where you are based on the turns that you make. So if you're driving on a road and so you go, say, 30 feet and then you turn right and then you go another 30 feet and then you turn right and then you go another 100 feet and you turn left.

Based on where those points are, you can figure out there's only after the third or fourth turn, there's only one place where you could are. Right. You can figure out, like, there's only, like, you know, after the first, after, like, the third or fourth turn, there's only one place where you could be. Okay. All right.

That's the next fad that's gonna come back. Yeah, cassette tape, that seems extremely inefficient. the wild thing, I love that it has, like,

a crazy taxi, like, you're going to this place, and this arrow points just in a direction. So, just go that way, roughly. If anybody wants to see a picture

of the ETAC navigation system, we'll put it up on scishowtangents.org. It's beautiful, green on green, just as you would expect. The screen is? Yeah. Nice. It's time for you to pick

which one your favorite fact was. Oh, boy. I forgot to hit it. Was it the latitude, the longitude problem? Longitude problem. Longitude problem. Longitude problem or was it the ETAC navigation system?

I have to say I am tired of learning about new technology that cassette tapes were used for that I didn't know about. I'm annoyed that I didn't know.

That shouldn't you shouldn't have to take that out on me. Actually, though, the boat thing reminds me of the pool tables on cruise ships because they move with the boat thing reminds me of the pool tables on cruise ships

because they move with the boat so that they stay level so you can actually play pool so I'm gonna give it to Sari fine

yeah take out your aggression on Hank's fact what are you mad about Sam? oh I'm not really mad about anything this is like

one of those things where it's like you could have something about how science saved humanity or about these dumb tapes. But the dumb tapes are so funny. And I love thinking about the dumb things that we used to do to

make up for the fact that we didn't know how computers were yet. So Hank, it's mine. All right. Now it's time to ask the science couch where we ask listener questions to our couch of finely honed scientific minds. At L Joel Rods asks, how did people navigate without stars as in on cloudy or stormy nights? I think they just crossed their fingers that it would stop being cloudy and stormy. I mean, if you're in the middle of the ocean, like you could just keep going and then figure out if you're how far off course you are once that the clouds are gone right but then you might starve to death yeah you could

you could definitely it could turn out real bad during night time that's not gonna like there's nothing you can do but during the daytime wasn't there like a a rock tell me about the rocks let me tell you about this rock calcite has a very cool property called birefringence. So that light passing through calcite is split because of the way the crystal is oriented. So it forms a double image on it. So if you put, for example, calcite on top of a newspaper, all the words you'll see double, like slightly offset from each other. It's very cool. And the brightness of both images relative to each other depends on a property of light called polarization. Light is made up of waves that oscillate.

When all of the oscillations are pointing in the same direction, light is polarized. Around the sun, there are concentric rings of polarized light with the sun at its center. with the sun at its center. And so with calcite, which is a crystal that depolarizes light, you can hold it up to the sky and determine the location of the rings around the sun. And this is when it's cloudy. Even when it's cloudy, yes.

Because the light from the sun is still traveling through. There's still sufficient light. The light pattern on the calcite and through the calcite varies depending on the orientation of the stone relative to the light polarization from the sun. And I think when the images got more aligned or they got more equal in brightness, then you know that you're pointing more directly at the sun because the polarized lights are rings around it and they're hitting the stone in a more equal way.

So this is what we think was mentioned in Norse mythology or Viking times called a sunstone that they used for navigation. So in these texts, there's a bunch of passages, as far as I can tell, that was like, we used the sunstone and found our way home. You can also use a sunstone to turn your gloom into a blossom. Is that a Pokemon joke? Yes. The way this area is with music, I'm like with Pokemon. That is a better thing

to be that way about it. If you want to ask the Science Couch, you can follow us on Twitter at SciShow Tangents where we'll tweet out the topics for upcoming episodes every week. Thank you at Becca Sitlali

at Minimarker3 and everybody else who tweeted us your questions this week. Final scores! Stefan and I are tied for last with one. Sari and Sam are tied for first with two. Hooray!

If you like this show and you want to help us out, it's easy to do that. First, you can leave us a review wherever you listen. That helps us know what you like about the show. And we're going to be looking at iTunes reviews for topic ideas for future episodes. Second, tweet out your favorite moment from the show. And finally, if you want to show your love for SciShow Tangents, just tell people about us.

Thank you for listening. I'm Hank Green. I'm Sari Reilly. I'm Stefan Chin. And I'm Sam Schultz. SciShow Tangents is a co-production of Complexly and the awesome team at WNYC Studios. It's created by all of us and produced by Caitlin Hoffmeister and Sam Schultz, who also edits a lot of these episodes, along with Hiroko Matsushima.

Our sound designer is Joseph Tunamedish. Our social media organizer is Victoria Bongiorno, 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. A two-year study published in 2014 in the journal Frontiers in Zoology

concluded that dogs can sense the Earth's magnetic field and seem to prefer to line themselves up with its north-south axis while pooping. I've heard that before, but I think it's going to be fake. You know, I took it with a little bit of a grain of salt, too. So this isn't always observed every time a dog poops, and they think that's because dogs get thrown off when there's disturbances in the electromagnetic field, so they don't know which way to poop anymore.

That's why they go around in circles a bunch. They're like, wow, what the hell? Maybe it is. Maybe you cracked it open.