Daniel and Kelly’s Extraordinary Universe - What is cold welding?

Episode Date: February 22, 2024

Daniel and Kelly talk about how its possible to merge metals without melting!See omnystudio.com/listener for privacy information.

This is an I-Heart podcast. I'm Dr. Joy Hardin-Bradford, host of the Therapy for Black Girls podcast. I know how overwhelming it can feel if flying makes you anxious. In session 418 of the Therapy for Black Girls podcast, Dr. Angela Neal-Barnett and I discuss flight anxiety. What is not a norm is to allow it to prevent you from doing the things that you want to do, the things that you were meant to do. Listen to Therapy for Black Girls on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Every case that is a cold case that has DNA. Right now, in a backlog, will be identified in our lifetime.

On the new podcast, America's Crime Lab, every case has a story to tell, and the DNA holds the truth. He never thought he was going to get caught, and I just looked at my computer screen. I was just like, ah, gotcha. This technology's already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Our IHeart Radio Music Festival, presented by Capital One, is coming back to Las Vegas. Vegas. September 19th and 20th. On your feet.

Streaming live only on Hulu. Ladies and gentlemen. Brian Adams. Ed Sheeran. Fade. Glorilla. Jelly Roll. John Fogarty.

Lil Wayne. L.L. Cool J. Mariah Carey. Maroon 5. Sammy Hagar. Tate McCray. The offspring. Tim McGraw.

Tickets are on sale now at AXS.com. Get your tickets today. AXS.com. Do we really need another podcast with a condescending finance brof trying to tell us how to spend our own money? No thank you. Instead, check out Brown Ambition. Each week, I, your host, Mandy Money, gives you real talk, real advice with a heavy dose

of I feel uses, like on Fridays when I take your questions for the BAQA. Whether you're trying to invest for your future, navigate a time. toxic workplace. I got you. Listen to Brown Ambition on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. Hey, Kelly, how are things going on the science farm? You know, they're going pretty well, but we have some old pipes and they've been failing. And so, you know, renovating the bathroom and the kitchen, we're pretty low on my to-do list. But suddenly they went to the top. And so there's been

lots of renovating projects happening. Ooh, does that mean lots of opportunities to show your kids how to use power tools, circular saws and arc welders and all that good stuff? There's lots of opportunities for me to play with power tools. Many different kinds

of saws. No arc welders yet. But generally the kids are not playing with the power tools. Not until they hear this episode and then they start asking for their turn. This is why my kids don't get to listen to your podcast. Oh, man.

How can you consider yourself a good parent if you don't share this podcast with them? I'm pretty sure that the number one rule of parenting is keep the kids alive. And I'm pretty good at that. And that does seem to be tied to them not listening to your podcast. Fair point. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I want everybody's kids to stay happy and healthy.

I'm Kelly Weiner-Smith. I'm a parasitologist. I'm adjunct at Rice University. And I also want kids to stay happy and healthy, which probably means no power tools before the age of 10. Ooh, you hear that? Kelly's kids? 10th birthday, you're getting power tools.

Oh, no, that's only a couple months away for one of them. I meant 20. Wow, that was a pretty quick backpedaling right there. Well, you know, eventually they got to learn some useful skills, so arc welding could be in their future. You know, she's really good with the screwdriver, and I feel like I've done my part. She can also make a little circuit. She did that for the talent show. And it had little light up eyes and the mascot of her school.

And it was pretty cool. I'm doing a great job, Daniel. You're doing a bang. up job for sure. And so welcome to the podcast, Daniel and Jorge explain the universe in which we try to do a bang up job of welding your brain to the universe, making those connections between everything that's happening inside your skull and all the physics of the universe. The black holes, the tiny particles, the galaxies, the arc welding, everything that's going on out there. We want you to understand it. No topic is too big. No topic is too small. No question is too weird. No

No idea is too bonkers for us to consider because our goal is to make sense of the whole universe. My usual co-host, Jorge, can't be here today, but I'm very happy to be joined by Kelly to talk about today's amazing and fun topic. I'm excited to be here. You know, how, I think you and I just had a podcasting anniversary. Didn't we? It's been like two and a half years or two, I don't know. It's been a while.

I'm excited. Oh, no. I'm embarrassed. I haven't been keeping tracks. totally unaware of our anniversary. I apologize. I should have gotten you something. Well, you got me a really interesting topic to talk about. So thank you. Yes, that must have been my subconscious plan of what's what it was the whole time. Yes. The two year anniversary is the cold welding anniversary. Well, congratulations on two years of being on the podcast. We love all

your contributions. Oh, I love being here. Thanks. Awesome. And sometimes in the podcast, we talk about quantum mechanics. Sometimes we talk about black hole. Sometimes we talk about planetary orbits and the future of our star. And sometimes we talk about the everyday physics and science that is around us, the stuff that makes up our lives, how it works and how hard it is to understand even the everyday normal stuff in our universe. It never gets easier. It's sort of amazing. The complexity of things that we see around us, rocks and blueberries and ice cream. And it's incredible that we can understand how that stuff all comes together from the tiny little particles that are inside it. The buzzing and towing and froing of all those little bits somehow weave themselves together

into this incredible experience we have where things seem solid or liquid or gaseous, that we know that that actually all just bubbles up from the tiny little particles inside them. I'm glad you're confident that we understand the world because as a biologist, I'm way less confident, but we'll go with it. You know, I was recently doing college interviews, and one young lady told me she was really interested in biology because she thought it was cool how you could explain everything using the smallest bits around us, the cell. And I was like, well, it is very cool how the cell comes together to make complex biology, but you know you can go further than that, right? You can dig

deeper. You leave her alone. She's on the right track. I almost convinced her to do particle physics, but she was like, nah, she wanted to study stuff that was more relevant to our lives. Good for her. But there are still lots of deep mysteries remaining about this fairly pedestrian idea. Everything is made of particles. Those particles follow simple rules. And how those bits bang up against each other and stick or don't stick and repel makes up our whole world. Why some things are shiny, why some things are sticky. We think that those are all emergent properties from those little particles and the rules that they follow. But it's complicated. It's not like if you give me the location and velocity of 10 to 29

particles, I can tell you exactly how they're going to behave. Oh, this thing's going to flow or this thing's going to conduct electricity because it's a lot of particles. It's too many for us to understand, which is why chemistry is still a thing, right? Which is the reason we don't just have particle physics as the only science in the universe. I mean, that would not be as interesting, really. But I remember I took stochastic differential equations in college and I was just like, how do we know anything about the universe ever? This is also complicated. And, It is incredible because the universe seems chaotic. All those tiny little particles are so dependent on other tiny little particles.

It's incredible that anything emerges. But one of the great philosophical mysteries of science is that simple stuff does emerge. Balls seem to follow simple trajectories, even if we can't understand the tiny particles inside them. You can make chicken soup without understanding quantum gravity. The universe is understandable at all these different layers, which means there are fascinating questions and interesting mysteries at every level of. of science, you know, studying galaxies, studying people, studying cells, studying funguses, and studying the tiny little particles. Questions to be asked at every level. Not sure we'll ever understand people, but we'll do our best and keep moving forward.

Exactly. And so one of the topics we love thinking about is how materials work. Why protons and electrons come together to make one thing conduct electricity and something else be transparent and something else be opaque. How does that all emerge from the the tiny little particles that are inside them. And there's so many different aspects of these materials we can explore, like how you stick them together to build stuff. How does the Eiffel Tower come together

from all those individual bits of steel? Gorilla glue. No? Wow, you just infended an entire country over there. I mean, it's a really good glue. You can get it in a can and spray it. Are you saying if they were going to build the Eiffel Tower today,

They would use guerrilla glue instead of welding. Probably, I don't know. You'll have to tell us about welding. Then I'll make my decision at the end. Well, today in the podcast, we are going to talk about welding, how it works, how you can stick stuff together, and how you can possibly do it without even heating things up in a way that could be helpful for space industry and could be safe for even Kelly's children. Oh, all right. You've got my attention. Maybe my oldest can listen to the, you know, second part of this discussion.

So today in the podcast, we'll be asking the question. What is cold welding? So this is a topic a bunch of listeners wrote in to ask me about what is the physics or the chemistry or just the science of cold welding? How could it be possible to stick stuff together without melting it down first? And could this potentially be a way to build things in space? So, you know, when you proposed the topic of cold welding to me, I could not remember a time when I had heard this phrase. And so my first thought was, I was it like sticking like pieces of gum together? And then I'm like, no, welding specifically refers to metal, right?

It's like putting two pieces of metal together. Is that right? Yeah. Yeah. And so then I was like, I don't know. But I hear it has to do with space. So I'm going to have to go with that. So let's see if your listeners are more clued into.

to the world of welding than I am. I bet they are. So thanks very much to everybody who answers these questions for the podcast. If you would like to contribute your uninformed speculation for the episode, please don't be shy. Write to me to questions at danielanhorpe.com. Everybody's welcome. So think about it for a moment before you hear these answers. What do you think cold welding is and how does it work? Here's what listeners had to say. Well, cold welding can't work by heating up to metal sources and melting them together, but it could create a chemical reaction that causes them to melt together. So my guess is it's not actually fire, but it's some sort of chemical. Maybe it is using a chemical reaction to fuse two things together to rearrange the molecules. It reminds me of

the old farmers in Vermont would attach wrought iron gate latches to granite posts by boring a hole in the granite and sticking the gate latch in there and then pouring some sort of a powder that would create a reaction and fuse the two together. I've tried to cut them out many, many, many years later and it's impossible. It's sort of just one thing. Well, those were two great answers. And to be honest, I hadn't heard about farmers attaching iron latches using a powder to connect it to granite. Like, that's awesome. I've got to find an excuse for how to do that on the farm. even though right now I don't think I need to. I think that sounds like farm magic.

You know, I think he's run into some magic and they have some like spells and powders and they're able to fuse things together. I think we need to dig into this. This could be like a whole revolution in science. So you hadn't heard of that before either? Vermont Farmer Magic. No, I had not heard of that before.

I can imagine it being pretty obscure, Vermont Farmer Magic, but that's not that far away from the Salem witches. Those farmers, you've got to be careful. You've got to be careful using your powers out there where everybody can see you. Yeah, but this doesn't seem to be something a lot of people have understood. And frankly, I was a little surprised, Kelly, that you didn't come across it in all of your deep, deep research about space settlements. You know, I have literally thousands of pages of notes and my mind retains 1% of what I write down because I figure, why memorize it?

If I could just, you know, control what it? Control F for my search term and then see what I wrote down in the past. So I bet I read about cold welding at some point, but it did not stay in my internal hard drive. Well, maybe it turns out it won't be crucial for a space settlement after all. We'll find out. So I asked a silly, I won't say stupid, a silly question at the beginning, you know, could it be like sticking two pieces of gum together? And you told us, no, it requires metal. What else are the very, very basic facts of welding?

Yeah, so before we talk about specialized cold welding, let's just talk about normal vanilla hot welding, I guess. And this is basically sticking two pieces of metal together. You want to build the Eiffel Tower, you want to build a bicycle, you want to build a tank, you want to build an airplane, all this kind of stuff. You got to use welding. Welding is basically the way that we grill stuff together in the modern world.

world. So I'm doing a bathroom renovation. And luckily, when I opened up the wall, there were no copper pipes because then I was going to have to solder. And I don't know how to solder. But I would have learned is soldering welding? Because it's like that little silvery thing that you unroll and you heat up and you put on the copper. That's metal too, right? So does that count? Yeah. So that does not count as welding. Soughtering and welding are two different things. So welding is when you melt two pieces of metal so the metals themselves join become like one piece. So you got two objects. You want to stick them together. You actually melt the edges of both of them. Sodering is different. Sodering, you have a lower temperature filler, something which melts at a much lower

temperature that basically acts as glue and bonds to the two surfaces, but you don't actually melt the two things you're sticking together. So you've got two pipes you want to stick together. You can solder them together by melting some filler material which sticks them together. Or you could actually weld them by melting the two pipes and sticking them together when they're liquid. So when they cool, you get those chemical bonds between them. Ah, but soldering is still cool because you get you use a blow for. I was kind of torn when I opened up the walls and there was pecks. Part of me wanted to solder. Part of me did. But anyway, okay, I'm getting, I'm getting a soft track.

And soldering is something you can do an electrical lab, right? You have that special solder material, which you touch to the tip of the soldering iron. It's just like instantly liquefies, right? It's super cool stuff. And that stuff you use because it liquefies very, very easily, and then it cools very quickly and becomes solid again. So that's soldering. But welding is different, right?

Welding is when you really want to join these two materials and you do it by some combination, usually of heat and pressure. Okay. And I'm guessing that we've been welding. It's got to be after we get access to fire. How much after we get access to fire before we're welding? Yeah, welding technically is something we've been doing for thousands of years. Essentially, blacksmith's invented welding.

They notice you got two pieces of metal, you heat them up and pound them hard enough. They will join. A lot of the stuff that's been connected together to make basic swords and tools for farms and all this stuff that blacksmiths have been making for thousands of years, They call that forge welding, basically heat it up and hammer it hard. And you will get that fusion, that connection between the two materials that tells you that they are now one. Okay.

So they're using like a furnace. Is that the most typical way or a blowtorch? Is that the most typical way to get the heat that you need to combine two metals? Yeah, exactly. And when my dad retired from a Los Alamos National Labs, he actually took up blacksmithing as a hobby. I was pretty sure he was, like, preparing for the end times. He thought, like, what would be a useful skill to have if civilization collapsed? And he decided blacksmithing would be useful.

And so he got a little furnace and he would go to the dump and, like, pick up scrap metal, you know, like truck suspensions and all sorts of stuff. And he would melt it down and hammer it into shapes. And he made all sorts of stuff from, like, towel hooks to his own spears and stuff like that. Wow. That's awesome. It was pretty cool until half the town burned down in a forest fire, which is a real tragedy. And then the neighbors were a lot less keen on him having like a thousands of degrees furnace in his garage, spewing up sparks into the dry woods. So he got shut down.

Yeah. Reasonable. Yeah. But sad. Hey, do you know Rick Farneski? I don't. Who's that? I think he's the current blacksmith that loves alibos and he's a friend of mine.

Oh, that's cool. Right. Back and off. Okay. Okay, so I was trying to get you to talk about electricity. Yeah, but blacksmithing is an ancient form of welding, right? You heat it up, you squish it together, and what's happening there is that the metals on one side and the metals on the other side are bonding together.

And so there's really no distinction there. And that makes a very, very strong connection, right? But in the late 19th century, we invented arc welding. We had electricity now and see we could more efficiently deliver energy than just like sticking the whole thing in an oven, which also isn't possible if you don't have a big enough oven. You want to weld together two eye beams. You don't want to have to stick the whole thing in the oven and then hammer them together. You want to only heat up the spot between them that's touching. So what is more dangerous? A giant furnace operating at intense heat or electrifying

metals in working with that. Kid 1 is not allowed to listen to the episode up to this point yet. Let's let's see where we get to. But arc welding is actually really cool because it basically makes a circuit. You're running electricity through the metals, and because the metals are not perfect conductors, there's some resistance to them, and resistance means heat. Resistance, you're turning electrical energy into thermal energy. Like the way a light bulb works is you're running electrical current through something which is a resistor, it's going to heat up, and then it's going to glow. So the reason the metals get hot is the same reason that a light bulb glows.

Ah. And so we just don't let it get out of control because you don't want your light bulbs burning or melting. That's right. And so in arc welding, what you're doing is creating a circuit and then you're passing that electricity from a stick which arcs onto the spot that you're trying to weld, passes energy through that and then completes the circuit. And so you just power that electricity back and forth.

It can be DC, it can be AC, all sorts of varieties of it. It was meant that in the 1800s when people were learning about the power of electricity. You know, you've got me wondering now. Fun tangent. So the first spacewalk ever conducted by a woman was Spetlana Subitskaya, and she welded in the vacuum of space for the first time. So do you think that she welded with heat or electricity? I suspect that was an arc welding, right? because the heat generation from like a blow torch

might require combustion with the atmosphere. Oh, of course. I suspect that was probably arc welding, yeah. Oh, I should have known that. As soon as you started saying it, I was like, oh, of course. But anyway, all right, so fun. Yeah, there you go. But hold on, that sounds super dangerous.

You have this like arc welding in space. I mean, that could easily rupture a suit or cause some damage. So that seems crazy to me. Well, you know what's infuriating? She is this, like, hyper-competent, incredible cosmonaut. And there's this movie called Salute 7 that came out in Russia. And it's sort of like, Solute 7 is almost their equivalent to our Apollo 13. So Solute 7, like they had a problem.

I think it was with the solar panels and the power ran down. So they had to send somebody up there to try to fix it and get it back online. But at the beginning of the movie, they create this scene where Svetlana Savitskaya is welding in space, which happens, but she gets a welding burr in her glove and she's starting to lose pressure and her male colleague needs to pull her back into the station because she just like, I don't know, it was like losing her composure.

And that didn't happen. She did a great job of welding. She didn't get a burr in her glove. She didn't need to be saved by a man. But that's how the movie starts. And that made me very frustrated. Tangent done. Oh, and the rest, no, no, almost done.

Tangent almost done. The other big lie in the movie is that they need to get up there to get the station started again because the shuttle, the Americans are going to set off the shuttle and they want our technology. So they're going to put the Solute 7 space station in the shuttle's cargo bay and take it back to Earth to steal our technology, which it wouldn't fit. That didn't happen. But that's like a huge. And at the very end, you've got the space shuttle driving past Saul, and the space shuttle people who are driving

salute the solute cosmonauts for doing such a good job of getting it fixed before they could go there to steal it. And it was like, what? Anyway, a classic film. It sounds like all the research you did for your space settlement book may have ruined you for a science fiction, Kelly. Yeah. Yeah, that's probably true.

That's the downside of knowing a bunch of stuff. Better not to know. So in the 1800s, we developed. this new technique. We'd like basically the first advance since blacksmithing for thousands of years in how to join metals. And this got really fast forwarded in the world wars in the early 1900s because people wanted to make lots and lots of tanks and airplanes and all sorts of stuff. And arc welding can be a little bit painful. It's kind of slow and it can be inefficient. And so they developed lots more techniques to do this much more quickly, to do it much more

efficiently so fast welding really was born in the first part of last century because of the world wars humans wanted to kill each other more efficiently so they had to be quick at building those killing machines so depressing same goes for rockets right that's the rockets that took us to the moon were used to drop bombs on london without great aim i'd say but uh anyway yeah the conflict i feel deeply internally i mean a lot of advances in physics come from wanting to build weapons of destruction. And so that's also where a lot of funding comes from. But it does in the end reveal a lot about the nature of the universe. So it's a tough situation. Yep. But it turns out that you can apply a lot of these welding techniques, not just metals. You can also weld things like

glass. You can take two pieces of glass and you can have a glass rod and you can use a blow torch to melt the glass and stick them together. And so you can weld pieces of glass together. You can even weld glass to ceramic or to steel, all sorts of stuff. So welding is not just something you have to do with metals. I didn't realize that. I guess I did think welding was metal specific. Yeah. It's basically just joining stuff together by melting them.

And it makes a lot of sense because you melted together and now the atoms are all jiggly and they can jiggle together and when they cool, it's like they're one again. What's sort of mysterious is doing this without heat. It's so cold welding is a much. stranger, much more interesting and maybe potentially useful in space kind of process. And we're going to learn more about it after the break. I'm Dr. Scott Barry Kaufman, host of the psychology podcast. Here's a clip from an upcoming conversation about exploring human potential.

I was going to schools to try to teach kids these skills and I get eye rolling from teachers or I get students who would be like, it's easier to punch something. someone in the face. When you think about emotion regulation, like you're not going to choose an adaptive strategy, which is more effortful to use unless you think there's a good outcome as a result of it, if it's going to be beneficial to you. Because it's easy to say like, like go you, go blank yourself, right? It's easy. It's easy to just drink the extra beer. It's easy to ignore, to suppress, seeing a colleague who's bothering you and just like walk the other way. Avoidance is easier. Ignoring is easier. Denials is easier. Drinking is

easier. Yelling, screaming is easy. Complex problem solving, meditating, you know, takes effort. Listen to the psychology podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Have you ever wished for a change but weren't sure how to make it? Maybe you felt stuck in a job, a place, or even a relationship. I'm Emily Tish Sussman, and on she pivots, I dive into the inspiring pivots of women who have taken big leaps in their lives and careers. I'm Gretchen Whitmer, Jody Sweeten, Monica Penn, Elaine Welteroth. I'm Jessica Voss. And that's when I was like, I got to go.

I don't know how, but that kicked off the pivot of how to make the transition. Learn how to get comfortable pivoting because your life is going to be full of them. Every episode gets real about the why behind these changes and gives you the inspiration and maybe the push to make your next pivot. Listen to these women and more on She Pivots, now on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Hello, Puzzlers. Let's start with a quick puzzle. The answer is Ken Jennings' appearance on The Puzzler with A.J. Jacobs. The question is, what is the most entertaining listening experience in podcast land?

Jeopardy-truthers who say that you were given all the answers believe in... I guess they would be Kenspiracy theorists. That's right. Are there Jeopardy-truthers? Are there people who say... that it was rigged? Yeah, ever since I was first on, people are like, they gave you the answers, right? And then there's the other ones which are like.

They gave you the answers, and you still blew it. Don't miss Jeopardy legend Ken Jennings on our special game show week of the Puzzler podcast. The Puzzler is the best place to get your daily word puzzle fix. Listen on the IHeart radio app, Apple Podcasts, or wherever you get your podcasts. The U.S. Open is here, and on my podcast, Good Game with Sarah Spain, I'm breaking down the players from rising stars to legends chasing history. The predictions will we see a first-time

winner and the pressure. Billy Jean King says pressure is a privilege, you know. Plus, the stories and events off the court and, of course, the honey deuses, the signature cocktail of the U.S. Open. The U.S. Open has gotten to be a very fancy, wonderfully experiential sporting event. I mean, listen, the whole aim is to be accessible and inclusive for all tennis fans, whether you play tennis or not. Tennis is full of compelling stories of late. Have you heard about Icon Venus Williams' recent wildcard bids or the young Canadian Victoria Mboko making a name for herself?

How about Naomi Osaka getting back to form? To hear this and more, listen to Good Game with Sarah Spain, an IHeart women's sports production in partnership with Deep Blue Sports and Entertainment on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Presented by Capital One, founding partner of IHeart Women's Sports. All right, so hot welding uses heat to combine metal, glass, plastic, and steel. But you have told me that we can do it without heat. And so maybe my daughter can listen to this part of the episode. So how do we do that?

Do we just bang them together really hard and hope they stick? That's the long and short of it, yes. Essentially, you can do cold welding if you have pressure and if the materials are very, very clean. Think about what's happening inside a metal. Metal is essentially a crystal. You have all of these atoms of iron or whatever, and they're lining up in a crystal. And the reason they're so strong is all those bonds are holding them together. How do you make a bigger crystal?

Well, you could like rejigger all the atoms. and make them liquid again and then stick them together so they cool back down to make a crystal. But what if you just have like half of a crystal here and half of a crystal there and you just like stick them together so that the two bits of crystal like link together. Sort of like sticking two puzzle pieces together, right?

You don't have to melt them down to liquid cardboard to make to stick them together. You just sort of fit the nibs into the holes and they click together into one big picture. Okay. So that's a sort of idea. behind cold welding, like if you have a material that's very regular and you have in two pieces of it, you just get them together close enough and apply a little bit of pressure,

they will all of a sudden act like they were always one thing. They would just sort of like stick together. All right. So I'm having a little trouble wrapping my head around it. So I'm imagining like, all right, so you put two pieces of metal together and very, very, very slowly they start what, like acting like liquid and sort of mixing together. And sort of mixing together. or yeah why so why does that why does that happen it's not very very slow the whole thing can happen in seconds or less and there's no liquid involved this is just two pieces of metal clicking together I read this fun quote by Richard Feynman he says quote the reason for this unexpected behavior is that when the atoms in contact are all of the same kind

there's no way for the atoms to know they are in different pieces of copper essentially you just have like a bunch of copper here and a bunch of copper there you bring them close together they will stick together they do like to bond to each other think about what happens between two atoms of copper there are electrons that are like flowing between them bonding them together that's what the bond is right the actual nuclei aren't stuck together it's the electrons between them and so if you have two atoms you bring them near each other they will bond they don't have to become a liquid in order to bond together. So why do metals do this? And like I've got a book sitting next to me with lots of pages, but the pages are staying distinct. Why doesn't everything

start just sort of blending together? Exactly. Why isn't the whole world just fuse into one lump? Right. Exactly. Yes. Why? This is something metals can do because the electrons in a metal are very Like some materials, the electrons mostly stick around their own atom or the neighboring atom. But when metals come together, the energy levels of those electrons are such that the electrons can really

flow freely through the metals. It's more like an ocean of electrons. And this all depends on how the energy levels translate. Like, you have an individual atom. We know that the electrons around that atom have energy levels. Like you remember from your high school chemistry that there's like the 1P orbital and the 4F orbital, and there's all these energy

energy levels for an electron. We shouldn't assume I remember anything from high school chemistry, but keep going. I don't remember it either. I probably just remember it because my son is taking high school chemistry, so I have to hear about all this stuff. Anyway, electrons around atoms have energy levels, right? Well, what happens when you have two atoms and now your electrons are sort of like zicking back and forth between those two atoms?

Well, the energy levels get more complicated because you're now responding to the positive charge of two atoms. Now add another atom and another atom and another atom, you get a whole crystal lattice. And so now you get a bunch of different energy levels for the electrons. And metals and insulators have different kinds of energy levels there. In metals, it's very easy for the electrons to like jump up to the higher energy levels and then move around the whole atom. In insulators, there's like a big gap there and the electrons can't easily get up there.

So they're sort of like trapped around individual atoms more. So the short answer is metals have a lot of electrons that easy to flow around. And so if you bring two pieces of metal together, their electrons would just sort of like start flowing back and forth. And then the copper atoms will be like, hey, you're my neighbor. I'm your neighbor. Let's share electrons. And boom, they're bonded. So, all right. So I've got these copper pipes in a different part of my house. And if you get this electron C and these metals can all like come together, why do my copper pipes retain their shape? Why don't, why doesn't, why doesn't the like copper, you know, that's above or that's at the top of the pipe sort of like

start moving into the copper that's at the bottom of the pipe and it all just sort of like becomes a glob. Well, copper is pretty strong, right? It's crystal structure preserve itself. But when it comes next to another piece of that crystal structure, then they will link together. It's just like the puzzle pieces, right? Puzzle pieces hold themselves together into a shape. But if you bring them nearby into something else where the, where the nibs and the holes all match up, they will click into place. The real question is like, you've touched copper together before. You didn't notice it like cold welding together.

It's not like every time two copper pennies touch that they cold weld. It's not like every time you have change in your pocket, you pull it out and it's like one single blob, right? That would be pretty weird. Right. And so why doesn't this happen all the time? The answer is that these materials have to be really, really clean. Essentially, you need like really bare copper to touch really bare copper or bare.

iron to touch bare iron. And that doesn't happen very often because we're in an atmosphere. And so the copper in your pipes interacts with the atmosphere and the oxygen in the atmosphere and forms like thin layers of oxides. So if you take two copper pipes and you bang them together, the copper is not actually touching. What's touching are these thin layers of oxides and greases and all sorts of other stuff on the surface. So you're not really getting that clean contact. Is it also like a lot of the metals that you encounter that we encounter in our day to day lives. Are they pure metals or are they also metals that have like other stuff mixed in? Yeah, a lot of the stuff we interact with are all sorts of stuff mixed into it. And a lot of stuff we interact with are not pure metals. So this

requires sort of a special situation. You need pure metals and you need them to be super duper clean. And so if you wanted to accomplish cold welding, what you got to do is like really carefully clean the surface. Sometimes you can actually just rub the two surfaces together in order to scrape them clear of these oxides, press them together, and they will make a metallic bond. So like if I rub my copper pipes, I know I'm stuck on the copper pipes. I rub the copper pipes together to clean them off and press them together. Is that going to be enough or no, are we back to your copper pipes are probably not pure copper? It depends on the purity of your copper, but this is something you can actually accomplished like down here on earth without special materials. It was first demonstrated in

the mid-1700s by a guy in England who just took two lead balls and he pressed them together and twisted them and rub them together and the two pieces would join. This seemed like magic at the time. It's like without any heat, he's somehow turning two lead balls into one single thing of lead. Did they burn him at the stake? him and all the Vermont farmers, yeah, exactly. This was in mid-17, 700, so 1724 by a guy named Reverend De Sagular. I'm not sure if he's actually French and it's like De Sagulet, but he demonstrated this phenomenon to the Royal Society and published the details in a scientific journal at the time.

So this is something you can accomplish with pretty normal materials. And then archaeologists discovered the humans had actually been doing this for thousands of years. You don't need heat in order to accomplish welding as long as you have pressure and you have two clean materials. So people have found like gold boxes made by cold welding that date to like 700 BC. Okay. So this is going to be potentially another silly question. So these boxes were gold. And so if having them together is enough for them to weld, how do we know that they hadn't like,

that this gold wasn't like lining a wooden box and over time it cold welded on its own? Like how do we know that they did it purposefully? Oh, yeah. Or how do we know they didn't use hot welding? If you do hot welding, you can see the effects at the intersection. Like you can see that it's been melted. It changes the chemical composition a little bit.

And then there's a transition there between the heated part and the not heated. part. So cold welding does look different from hot welding. So we can tell that this was not hot welded gold. Obviously, people have been doing goldsmithing also for thousands of years using heat and hammering, but these are cold welded materials. But you're right, it could have been accidental and probably the discovery of it was accidental. Somebody for some reason accidentally squeezed two pieces of gold together and discovered they had welded. And, you know, I hope that was a happy accident for whoever was doing that. Oh, happy accident.

But it's sort of amazing that you can do this. You know, on one hand, it seems sort of crazy. Like you stick two things together and they like talk to each other and then like intermingle themselves and click together. It seems kind of impossible to get everything lined up, right? On the other hand, it seems kind of obvious because copper is copper. Like you make copper crystal over here and you make copper crystal over there. They're going to have the same atomic spacing.

It's basically the same stuff. It's ready to get clicked together. you push on it a little bit and those atoms are just going to happily line up and interact with their new neighbors. It doesn't really matter that they used to be separate when to push them together. They're ready to grab onto each other. I feel like once you explain the concept to me, it's less surprising to me that it happens and more surprising to me that it doesn't happen all the time. Are there examples of it happening when it's not, when it wasn't intended to happen? Oh, there's lots of examples of it happening when it wasn't intended.

especially in the space program, which we'll get into in a little bit. It is a little bit complex to make it happen for more complex materials. Like if you imagine something that's an alloy or an ionic solid, these things really are more complex because they have lots of different components to them.

And so getting everything lined up is more tricky. I think it is possible in principle to cold well things that are not like pure copper or pure gold. It's just harder. You basically need more pressure and more time and a little bit more luck to make sure everything actually does line up against itself. But we have used cold welding,

and there's been examples of on-purpose and accidental cold welding in the environment of space. All right. Well, before we get to welding in space, space, space, let's take a commercial break. I'm Dr. Scott Barry Kaufman, host of the psychology podcast.

Here's a clip from an upcoming conversation about exploring here. human potential. I was going to schools to try to teach kids these skills and I get eye rolling from teachers or I get students who would be like, it's easier to punch someone in the face. When you think about emotion regulation, like you're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome as a result of it if it's going to be beneficial to you. Because it's easy to say like go you go blank yourself, right? It's easy. It's easy to just drink the extra beer. It's easy to ignore to suppress seeing a comment.

who's bothering you and just like walk the other way avoidance is easier ignoring is easier denial is easier drinking is easier yelling screaming is easy complex problem solving meditating you know takes effort listen to the psychology podcast on the iheart radio app apple podcasts or wherever you get your podcasts hello puzzlers let's start with a quick puzzle The answer is Ken Jennings' appearance on The Puzzler with A.J. Jacobs. The question is,

what is the most entertaining listening experience in podcast land? Jeopardy truthers who say that you were given all the answers believe in... I guess they would be conspiracy theorists. That's right. Are there jeopardy truthers? Are there people who say that it was rigged?

Yeah, ever since I was first on, people are like. They gave you the answers, right? And then there's the other ones which are like, they gave you the answers and you still blew it. Don't miss Jeopardy legend Ken Jennings on our special game show week of the Puzzler podcast. The Puzzler is the best place to get your daily word puzzle fix. Listen on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. Have you ever wished for a change but weren't sure how to make it?

Maybe you felt stuck in a job, a place, or even a relationship. I'm Emily Tish Sussman, and on she pivots, I dive into the inspiring pivots of women who have taken big leaps in their lives and careers. I'm Gretchen Whitmer, Jody Sweeten. Monica Patton. Elaine Welter-A. I'm Jessica Voss. And that's when I was like, I got to go. I don't know how, but that kicked off the pivot of how to make the transition.

Learn how to get comfortable pivoting because your life is going to be full of them. Every episode gets real about the why behind these changes. and gives you the inspiration and maybe the push to make your next pivot. Listen to these women and more on She Pivots, now on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. The U.S. Open is here, and on my podcast, Good Game with Sarah Spain, I'm breaking down the players from rising stars to legends chasing history. The predictions will we see a first time winner and the pressure. Billy Jean King says pressure is a privilege, you know. Plus, the stories and events off the court and, of course, the Honey Deuses, the signature cocktail of the U.S. Open.

The U.S. Open has gotten to be a very fancy, wonderfully experiential sporting event. I mean, listen, the whole aim is to be accessible and inclusive for all tennis fans, whether you play tennis or not. Tennis is full of compelling stories of late. Have you heard about Icon Venus Williams' recent wildcard bids or the young Canadian, Victoria Mboko, making a name for herself? How about Naomi Osaka getting back to form? To hear this and more, listen to Good Game with Sarah Spain, an Iheart women's sports production in partnership with deep blue sports and entertainment on the Iheart radio app, Apple Podcasts, or wherever you get your podcasts.

Presented by Capital One, founding partner of IHart Women's Sports. Okay, we're back. All right. So you promise. me stories about cold welding happening when we didn't want it to happen. But you told me that I had to wait until we got to the space part of the episode, which is almost certainly, you know, always my favorite part of any episode. So tell me about how space poses unique challenges and benefits for welding. Yeah. So space is sort of an obvious place you might want to do cold

welding because there's no atmosphere, which means there's nothing to oxidize your materials. You have a piece of bare, pure copper or whatever, it's going to stay bare pure copper. You don't need to, like, scrub the surface to get the oxides off because there's no oxygen to make any oxides. So there's no, like, gas in the middle there to interfere, no impurities. Your bare stuff stays bare stuff. Have we used that to our advantage yet? Like, do we, are there things that we decide we're just going to put together in space because we're going to send clean stuff up there and then assemble it with cold welding while it gets up there? You know, it seems like an obvious application, but I couldn't actually find an example of times this had been done intentionally.

And it seems to me like a great idea because having any sorts of like intense heat in space seems pretty dangerous. Like the story you told us was terrifying to me because, you know, on Earth you accidentally bring your heat too close to something, it melts. Or maybe you get a burn or something. But in space, you destroy your spacesuit, right? Everything is so much more dangerous out there in space. It seems like it would be awesome to do welding without the danger of heat or, like, super high electrical arcing. Yeah, space sucks. Space sucks, exactly.

I did find a couple of examples of accidental space welding. Go on. In 1965, Gemini 4 was the first American spacewalk. So they sent the guy out there. They opened the hatch. He goes out there. He spacewalks all around. He's having a great time.

They asked him to come back in. He actually didn't want to come back in because he was having so much. much fun. And when he came back in, they couldn't close the hatch again. The hatch was like stuck in the open position. They had to like really yank on it, which is not a situation you want to be in when you're out in space and you like can't close the door. No. No, you know, apparently, uh, apparently the same thing happened during the first Soviet spacewalk. Are you familiar with this story? No, what happened? It doesn't have to do with cold welding. But, uh, Alexei Leonov went out to do the first spacewalk ever because I think they beat us to that too. And

he couldn't get back in. And he's known to exaggerate his stories a bit. Like astronauts do. That's right. Well, I would too if I was an astronaut. But I think, you know, like his suit, you know, he got out into the vacuum of space and his suit sort of like puffed up a little bit because, you know, you pressurize your suit. And after it got a little like puffier, my understanding is either he couldn't get through the hatch or he couldn't like bend the way he needed to. So for a second there, he couldn't get back in.

But I guess in both cases, they managed to get the astronaut back in and bring them back home. safely. Thank goodness. Well, in this case, NASA was trying to figure out, like, why did the hatch get stuck? Kind of an important thing to understand. And what are the initial suggestions was cold welding that may be like the outside of the hatch cold welded itself to the surface of the spaceship. And, you know, this is the kind of thing we're not used to worrying about on the surface of the earth. You don't worry about like your keys cold welding themselves to your car and stuff because everything's covered, right? This paint or this oxidation or just plain dirt is keeping stuff from cold welding but in space this is maybe something we had to worry about

like anytime two metals touch are we going to worry about them like spot welding themselves together oh my gosh i know and actually if you look online there's a lot of lore about how this is an example of cold welding but you dig a little bit deeper and it turns out it's actually not cold welding at all when it came back down to earth the engineers dug into it and they found out it was just a stuck spring that didn't compress right so like very normal door not working. Okay. So you gave us like a psych moment. Could be cold welding, but it's not. Is there, are there any actual cold welding examples in space? Or are you just going to keep messing with us? No, there is one real example. And this is the Galileo probe. And so this is a probe which went out to explore

the solar system and take pictures of Jupiter, for example. But it got delayed. Wait, NASA? There were delays in a NASA project? I know. Shocking, right? And the spacecraft was like moved across the country multiple times. And during those transports, it got like shaking a bunch and the lubrication that was supposed to protect the metals from cold welding together eroded away. And so when they launched this thing and then they were supposed to unfurl the high gain antenna, the thing that was going to send us data back with images of Jupiter on it, it turns out that several of the metal struts had become cold welded together. And so it couldn't unfurl. No. Oh, and they even planned for it.

And that did planning didn't work. Oh, my gosh, I'm getting stressed just thinking about it. I know. Did they find a way around it or were they just stuck? They never got the high gain antenna to work. Fortunately, there's always like redundancies on these craft and they had the low gain antenna, which was not designed to be used to like send data. It was more like for control systems.

But they had to reprogram it and use it to send the actual pictures, which like delayed people seeing these images of Jupiter. But of course, you know, we got them. It's just more like downloading on one of those slow modems rather than your high speed internet. Yeah, but still, oh my goodness, those clever engineers, they figured it out. Thank goodness. I'm sure there were a lot of PhD students who were like, I can stay in grad school for another year or two. That's fine. But at least I'm going to get my images eventually. I know. It's like the old days when you download a picture and you're seeing one row of pixels at a time come across the screen. And you're like, what am I looking at? Did I download the right picture or not? Anyway, did my computer freezer?

Should I shut it down or do I wait? Yeah. Oh, not fun. So in practice, it's not really that big a problem. It's not like when we build big space stations or space settlement. We're going to have to worry about cold welding all the time. You really need like perfectly clean materials and they have to be pressed together for long enough for this to happen. So not really a huge concern in space.

All right. So are there any other applications that we should chat about? People have discovered that cold welding can also be really helpful for nanny. circuits. Like you want to build really, really small electronics. And these days the trend is to build like tinier and tinier microchips, which use less power and can be squeezed into all sorts of scenarios. So you can have like microchips in your cereal or whatever you need. Who doesn't want that? Exactly. You know, they can count your calories for you, right? Exactly. Anyway, nanoscale fabrication is tricky because spot welding is very hard when it's really, really

tiny. You know, basically need like tiny sources of heat or you need this electricity to arc perfectly. Well, what they've discovered is that you can do cold welding for nano fabrication. I read this paper that came out in nature like 10 years ago where they had ultra thin gold nanowires and you just bring them together and if the edges touch, boom, they cold well together within seconds. You don't even need a lot of pressure. Whoa. Yeah. And these wires, once they've cold welded together, essentially as like a near perfect bond. They did all these tests of like the electrical conductivity

and the crystal orientation and it's as if it was always just one wire. So this means Kelly we don't need your children with like their delicate little fingers to do tiny little arc welding on our nanocircets. Oh good, good because that was going to be a thing.

But it might be that we can send your kids out to space to do space construction jobs without arc welding, right? How do you feel about that? any of the episode. Nope. None of the episode. None of the episode. If your kids grow up and they want to work construction in space, you're going to say no. Yes. No. You didn't think about that deeply at all. That was just like a straight up no. I hope they don't go that route. But if they do, I will support them begrudgingly. Well, I think cold welding is super fascinating. And what it tells me

is that there's a lot more to understand about how these particles weave themselves together to make this sort of macroscopic materials that we're familiar with and that there's still sort of magic left. I mean, I'm not talking about Vermont farmer magic. I'm talking about accomplishing things that seem impossible to us. You know, just like sticking two pieces of metal together

and make them into one metal. Every time there's an advancement in material science, it feels almost like we're creating real magic. I agree, but I still feel like the main takeaway for me is one more thing to worry about in space. Is the whole welding going wrong? We should have gotten that in the book. I think you already had like a thousand reasons not to build in space in your book.

You don't need another reason. Yeah, I guess you're right. Beat that dead horse. And as much as I'm jokingly negative about chemistry, it does really give us access to the microscopic nature of materials. It's the easiest way to see these emergent properties to see how something can be sticky or shiny or brittle because of the way the particles inside it interact. And cold welding is just another manifestation of that, that our world really is dominated by the microscopic rules that somehow bubble up to make these incredible variety of behaviors and phenomena. Yeah, I got to give it to you. Chemistry is pretty amazing. It is kind of magic. Dang it.

Yeah. Yeah. My chemistry professors kept telling me that. But now I believe it. Finally, 30 years later, I've learned it too. 30. Oh. Oh, you're using. You might be older than me. All right. Well, thanks, Kelly, for joining us on this tour of chemistry, magic, and this dive into how cold welding works.

Thanks for having me. All right, everyone, keep wondering about how the universe works and send us your questions. This episode was inspired by listeners who wanted to understand how cold welding works. If you have ideas for things you'd like to hear us explore, please don't be shy. Write to me to Questions at Danielanhorhe.com. Tune in next time. Thanks very much. For more science and curiosity, come find us on social media where we answer questions and post videos.

We're on Twitter, Discord, Insta, and now TikTok. Thanks for listening, and remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. I'm Dr. Joy Hardin-Bradford, host of the Therapy for Black Girls podcast. I know how overwhelming it can feel if flying makes you anxious. In session 418 of the Therapy for Black Girls podcast, Dr. Angela Neal-Barnett and I discuss flight anxiety. What is not a norm is to allow it to prevent you from doing the things that you want to do, the things that you were meant to do. Listen to Therapy for Black Girls on the IHeart Radio app, Apple Podcast,

or wherever you get your podcast. Let's start with a quick puzzle. The answer is Ken Jennings' appearance on The Puzzler with A.J. Jacobs. The question is, what is the most entertaining listening experience in podcast land? Jeopardy-truthers believe in... I guess they would be Kenspiracy theorists. That's right. They give you the answers and you still blew it.

The Puzzler. Listen on the I-Heart radio app, Apple Podcast. or wherever you get your podcasts. Your entire identity has been fabricated. Your beloved brother goes missing without a trace. You discover the depths of your mother's illness. I'm Danny Shapiro, and these are just a few of the powerful stories I'll be mining on our upcoming 12th season of Family Secrets. We continue to be moved and inspired by our guests and their courageously told stories.

Listen to Family Secrets Season 12. on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.