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

0:08
Speaker 1: Hey, Kelly, how are things going on the science farm?
0:11
Speaker 2: You know, they're going pretty well, but we have some
0:13
Speaker 2: old pipes and they've been sailing and so, you know,
0:17
Speaker 2: renovating the bathroom in the kitchen. We're pretty low on
0:19
Speaker 2: why to do list, but suddenly they went to the
0:21
Speaker 2: top and so there's been lots of renovating projects happening.
0:26
Speaker 1: Ooh, does that mean lots of opportunities to show your
0:29
Speaker 1: kids how to use power tools? Circular saws and arc
0:32
Speaker 1: welders and all that good stuff.
0:34
Speaker 2: Uh, there's lots of opportunities for me to play with
0:37
Speaker 2: power tools, many different kinds of saws. No arc welders yet,
0:41
Speaker 2: but generally the kids are not playing with the power.
0:45
Speaker 1: Tools, not until they hear this episode and then they
0:48
Speaker 1: start asking for their turn.
0:50
Speaker 2: This is why my kids don't get to listen to
0:51
Speaker 2: your podcast.
0:52
Speaker 1: Man, how can you consider yourself a good parent if
0:56
Speaker 1: you don't share this podcast with them.
0:58
Speaker 2: I'm pretty sure that the number one rule of parenting
1:01
Speaker 2: is keep the kids alive, and I'm pretty good at that,
1:05
Speaker 2: and that just seem to be tied to them not
1:07
Speaker 2: listening to your podcast.
1:10
Speaker 1: Fair point. Hi, I'm Daniel, I'm a particle physicist and
1:28
Speaker 1: a professor at UC Irvine, and I want everybody's kids
1:31
Speaker 1: to stay happy and healthy.
1:33
Speaker 2: I'm Kelly Wieder Smith. I'm a parasitologist. I'm adjunct at
1:37
Speaker 2: Rice University, and I also want kids to stay happy
1:40
Speaker 2: and healthy, which probably means no power tools before the
1:42
Speaker 2: age of ten.
1:45
Speaker 1: Ooh, you hear that Kelly's kids tenth birthday, you're getting
1:48
Speaker 1: power tools.
1:49
Speaker 2: Oh no, that's only a couple months away from one
1:51
Speaker 2: of them. I meant twenty twenty.
1:56
Speaker 1: Wow, that was pretty quick backpedaling right there. You know,
2:00
Speaker 1: eventually they got to learn some useful skills, so arc
2:03
Speaker 1: welding could be in their future.
2:04
Speaker 2: You know, she's really good with the screwdriver, and I
2:07
Speaker 2: feel like I've done my part. She could also make
2:09
Speaker 2: a little circuit. She did that for the Talent Show
2:12
Speaker 2: and it had little light up eyes and the mascot
2:15
Speaker 2: of her school and it was pretty cool. I'm doing
2:17
Speaker 2: a great job, Daniel.
2:20
Speaker 1: You're doing a bang up job for sure, and so
2:23
Speaker 1: welcome to the podcast. Daniel and Joor explain the universe,
2:27
Speaker 1: in which we try to do a bang up job
2:29
Speaker 1: of welding your brain to the universe, making those connections
2:34
Speaker 1: between everything that's happening inside your skull and all the
2:37
Speaker 1: physics of the universe, the black holes, the tiny particles,
2:41
Speaker 1: the galaxies, the arc welding, everything that's going on out there.
2:45
Speaker 1: We want you to understand it. No topic is too big,
2:48
Speaker 1: no topic is too small, no question is too weird,
2:51
Speaker 1: no idea is too bunkers for us to consider, because
2:55
Speaker 1: our goal is to make sense of the whole universe.
2:58
Speaker 1: My usual co host he can't be here today, but
3:01
Speaker 1: I'm very happy to be joined by Kelly to talk
3:02
Speaker 1: about today's amazing and fun topic.
3:05
Speaker 2: I'm excited to be here. You know how, I think
3:08
Speaker 2: you and I just had a podcasting aniversary, didn't we.
3:12
Speaker 2: It's been like two and a half years or two,
3:15
Speaker 2: I don't know, it's been a while. I'm excited.
3:18
Speaker 1: Oh no, I'm embarrassed. I haven't been keeping tracks. I'm
3:21
Speaker 1: totally unaware of our anniversary. I apologize. I should have
3:25
Speaker 1: gotten you something.
3:26
Speaker 2: Well, that's you got me a really interesting topic to
3:28
Speaker 2: talk about. Oh, thank you.
3:30
Speaker 1: Yes, that must have been my subconscious plan of what's
3:33
Speaker 1: what it was the whole time.
3:35
Speaker 2: Yes, the two year anniversary is the cold welding anniversary.
3:38
Speaker 1: M Well, congratulations on two years of being on the podcast.
3:42
Speaker 1: We love all your contributions.
3:44
Speaker 2: Oh, I love being here.
3:45
Speaker 1: Thanks awesome. And sometimes on the podcast we talk about
3:48
Speaker 1: quantum mechanics. Sometimes we talk about black hole, sometimes we
3:51
Speaker 1: talk about planetary orbits in the future of our star.
3:55
Speaker 1: And sometimes we talk about the everyday physics and science
3:58
Speaker 1: that is around us, stuff that makes up our lives,
4:01
Speaker 1: how it works, and how hard it is to understand
4:04
Speaker 1: even the everyday normal stuff in our universe.
4:07
Speaker 2: It never gets easier.
4:09
Speaker 1: It's sort of amazing the complexity of things that we
4:11
Speaker 1: see around us, rocks and blueberries and ice cream, and
4:14
Speaker 1: it's incredible that we can understand how that stuff all
4:17
Speaker 1: comes together from the tiny little particles that are inside it.
4:20
Speaker 1: The buzzing and tuing and frowing of all those little
4:23
Speaker 1: bits somehow weave themselves together into this incredible experience we
4:26
Speaker 1: have where things seem solid or liquid or gaseous, that
4:30
Speaker 1: we know that that actually all just bubbles up from
4:32
Speaker 1: the tiny little particles inside them.
4:35
Speaker 2: I'm glad you're confident that we understand the world, because
4:37
Speaker 2: as a biologist, I'm way less confident. But we'll go
4:40
Speaker 2: with it.
4:41
Speaker 1: You know, I was recently doing college interviews, and one
4:44
Speaker 1: young lady told me she was really interested in biology
4:47
Speaker 1: because she thought it was cool how you could explain
4:49
Speaker 1: everything using the smallest bits around us, the cell. And
4:54
Speaker 1: I was like, well, it is very cool how the
4:56
Speaker 1: cell comes together to make complex biology. But you know
4:59
Speaker 1: you can go further than that, right, you can dig deeper.
5:04
Speaker 2: You leave her alone. She's on the right track.
5:06
Speaker 1: I almost convinced her to do particle physics, but she
5:09
Speaker 1: was like, nah, she wanted to study stuff that was
5:11
Speaker 1: more relevant to our lives. Good for her, but there
5:15
Speaker 1: are still lots of deep mysteries remaining about this fairly
5:18
Speaker 1: pedestrian idea. Everything is made of particles. Those particles follow
5:22
Speaker 1: simple rules, and how those bits bang up against each
5:24
Speaker 1: other and stick or don't stick and repel makes up
5:27
Speaker 1: our whole world. Why some things are shiny, why some
5:30
Speaker 1: things are sticky. We think that those are all emergent
5:33
Speaker 1: properties from those little particles and the rules that they follow.
5:36
Speaker 1: But it's complicated. It's not like if you give me
5:38
Speaker 1: the location and velocity of ten to twenty nine particles,
5:41
Speaker 1: I can tell you exactly how they're going to behave, Oh,
5:44
Speaker 1: this thing's going to flow or this thing's going to
5:46
Speaker 1: conduct electricity because it's a lot of particles. It's too
5:49
Speaker 1: many for us to understand, which is why chemistry is
5:53
Speaker 1: still a thing, right, which is a reason, the reason,
5:56
Speaker 1: the reason we don't just have particle physics as the
5:59
Speaker 1: only science in the universe.
6:00
Speaker 2: I mean, that would not be as interesting. But yeah,
6:05
Speaker 2: I remember I took stochastic differential equations in college, and
6:10
Speaker 2: I was just like, how do we know anything about
6:12
Speaker 2: the universe? Ever, this is also complicated, and.
6:15
Speaker 1: It is incredible because the universe seems chaotic. All those
6:19
Speaker 1: tiny little particles are so dependent on other tiny little particles.
6:21
Speaker 1: It's incredible that anything emerges. But one of the great
6:24
Speaker 1: philosophical mysteries of science is that simple stuff does emerge.
6:29
Speaker 1: Balls seem to follow simple trajectories, even if we can't
6:32
Speaker 1: understand the tiny particles inside them. You can make chicken
6:35
Speaker 1: soup without understanding quantum gravity. The universe is understandable at
6:39
Speaker 1: all these different layers, which means there are fascinating questions
6:43
Speaker 1: and interesting mysteries at every level of science. You know,
6:47
Speaker 1: studying galaxies, studying people, studying cells, studying funguses, and studying
6:52
Speaker 1: the tiny little particles questions to be asked at every level.
6:56
Speaker 2: Not sure we'll ever understand people, but well we'll do
6:59
Speaker 2: our best and keep.
7:00
Speaker 1: And forward exactly. And so one of the topics we
7:03
Speaker 1: love thinking about is how materials work. Why protons and
7:06
Speaker 1: electrons come together to make one thing conduct electricity and
7:10
Speaker 1: something else be transparent and something else be opaque. How
7:13
Speaker 1: does that all emerge from the tiny little particles that
7:15
Speaker 1: are inside them? And there's so many different aspects of
7:18
Speaker 1: these materials we can explore, like how you stick them
7:22
Speaker 1: together to build stuff? How does the Eiffel Tower come
7:24
Speaker 1: together from all those individual bits of steel?
7:28
Speaker 2: Gorilla glue?
7:32
Speaker 1: No, wow, you just invented an entire country over there.
7:38
Speaker 2: I mean, it's a really good glue. You can get
7:40
Speaker 2: it in a can and spray it.
7:41
Speaker 1: Are you saying if they were going to build the
7:43
Speaker 1: Eiffel Tower today, they would use guerrilla glue instead of welding.
7:47
Speaker 2: Probably, I don't know. You'll have to tell us about welding.
7:49
Speaker 2: Then I'll make my decision at the end.
7:51
Speaker 1: Well, today in the podcast, we are going to talk
7:53
Speaker 1: about welding, how it works, how you can stick stuff together,
7:57
Speaker 1: and how you can possibly do it without even heating
7:59
Speaker 1: things up in a way that could be helpful for
8:02
Speaker 1: space industry and could be safe for even Kelly's children.
8:06
Speaker 2: Oh all right, you've got my attention. Maybe my oldest
8:10
Speaker 2: can listen to the you know, second part of this discussion.
8:14
Speaker 1: So today in the podcast, we'll be asking the question
8:21
Speaker 1: what is cold welding? So this is a topic a
8:26
Speaker 1: bunch of listeners wrote in to ask me about what
8:28
Speaker 1: is the physics or the chemistry or just the science
8:31
Speaker 1: of cold welding. How could it be possible to stick
8:35
Speaker 1: stuff together without melting it down first, and could this
8:39
Speaker 1: potentially be a way to build things in space?
8:43
Speaker 2: So, you know, when you proposed the topic of cold
8:46
Speaker 2: welding to me, I could not remember a time when
8:50
Speaker 2: I had heard this phrase, And so my first thought
8:52
Speaker 2: was was it like sticking like pieces of gum together?
8:55
Speaker 2: And then I'm like, no, welding, welding specifically refers to metal, right,
8:58
Speaker 2: It's like putting two pieces of met together, is that right?
9:01
Speaker 1: Yeah?
9:02
Speaker 2: Yeah, yeah, And so then I was like, I don't know,
9:05
Speaker 2: but but I hear it has to do with space,
9:07
Speaker 2: So I'm gonna have to I'm gonna have to go
9:08
Speaker 2: with that. So let's see if your listeners are more
9:12
Speaker 2: clued into the world of welding than I am. I
9:14
Speaker 2: bet they are, so.
9:16
Speaker 1: Thanks very much to everybody who answers these questions for
9:19
Speaker 1: the podcast. If you would like to contribute your uninformed
9:23
Speaker 1: speculation for the episode, please don't be shy. Write me
9:26
Speaker 1: to questions at Danielandjorge dot com. Everybody's welcome, So think
9:31
Speaker 1: about it for a moment before you hear these answers.
9:34
Speaker 1: What do you think cold welding is and how does
9:36
Speaker 1: it work? Here's what listeners had to say.
9:39
Speaker 3: Well, cold welding can't work by heating up two metal
9:43
Speaker 3: sources and melting them together, but it could create a
9:46
Speaker 3: chemical reaction that causes them to melt together. So my
9:50
Speaker 3: guess is it's not actually fire, but it's some sort
9:52
Speaker 3: of chemical.
9:53
Speaker 4: Maybe it is using a chemical reaction to fuse two
9:58
Speaker 4: things together to rearrange them molecules. It reminds me of
10:02
Speaker 4: the old farmers in Vermont would attach wrought iron gate
10:06
Speaker 4: latches to granite posts by boring a hole in the
10:10
Speaker 4: granite and sticking the gate latch in there, and then
10:12
Speaker 4: pouring some sort of a powder that would create a
10:15
Speaker 4: reaction and fuse the two together. I've tried to cut
10:19
Speaker 4: them out many many, many years later, and it's impossible.
10:23
Speaker 4: It's sort of just one thing.
10:25
Speaker 2: Well, those were two great answers, And to be honest,
10:28
Speaker 2: I hadn't heard about farmers attaching iron latches using a
10:33
Speaker 2: powder to connect it to granite. Like that's awesome. I've
10:37
Speaker 2: got to find an excuse for how to do that
10:39
Speaker 2: on the farm, even though right now I don't think
10:41
Speaker 2: I need to.
10:42
Speaker 1: I think that sounds like farm magic, you know. I
10:44
Speaker 1: think he'd run into some magicians and they have some
10:46
Speaker 1: like spells and powders, and they're able to like fuse
10:49
Speaker 1: things together. I think we need to dig into this.
10:51
Speaker 1: This could be like a whole revolution in science.
10:54
Speaker 2: So you hadn't heard of that before either.
10:56
Speaker 1: Vermont farmer magic. Noila had not heard of that before.
11:01
Speaker 2: I can imagine it being pretty obscure Vermont farmer magic.
11:05
Speaker 2: But that's not that far away from the Salem witches.
11:10
Speaker 1: Those farmers. You gotta be careful. You gotta be careful
11:12
Speaker 1: using your powers out there where everybody can see you. Yeah,
11:16
Speaker 1: but this doesn't seem to be something a lot of
11:18
Speaker 1: people have understood. And frankly, I was a little surprised,
11:20
Speaker 1: Kelly that you didn't come across it in all of
11:23
Speaker 1: your deep, deep research about space settlements.
11:27
Speaker 2: You know, I have literally thousands of pages of notes,
11:30
Speaker 2: and my mind retains one percent of what I write down,
11:35
Speaker 2: because I figure, why memorize it if I could just
11:38
Speaker 2: you know, control what it control f for my search
11:42
Speaker 2: term and then see what I wrote down in the past.
11:44
Speaker 2: So I bet I read about cold welding at some point,
11:47
Speaker 2: but it did not stay in my internal hard drive.
11:50
Speaker 1: Well maybe it turns out it won't be crucial for
11:52
Speaker 1: a space settlement, after all, we'll find out.
11:56
Speaker 2: So I asked a silly I won't say stupid, a
11:59
Speaker 2: silly question at the beginning. You know, could it be
12:02
Speaker 2: like sticking two pieces of gum together? And you told
12:04
Speaker 2: us no, it requires metal. What else are the very
12:10
Speaker 2: very basic facts of welding.
12:12
Speaker 1: Yeah, so before we talk about specialized cold welding, let's
12:16
Speaker 1: just talk about normal vanilla hot welding. I guess, and
12:19
Speaker 1: this is basically sticking two pieces of metal together. You
12:22
Speaker 1: want to build the Eiffel Tower, you want to build
12:24
Speaker 1: a bicycle, you want to build a tank, you want
12:28
Speaker 1: to build an airplane, all this kind of stuff. You
12:30
Speaker 1: got to use welding. Welding is basically the way that
12:33
Speaker 1: we corillatly stuff together in the modern world.
12:38
Speaker 2: So I'm doing a bathroom renovation and luckily when I
12:43
Speaker 2: opened up the wall, there were no copper pipes, because
12:46
Speaker 2: then I was gonna have to solder, and I don't
12:49
Speaker 2: know how to solder, but I would have learned. Is
12:51
Speaker 2: soldering welding because it's like that little silvery thing that
12:57
Speaker 2: you unroll and you heat up and you put on
12:59
Speaker 2: the copper. That's metal too, right, So does that count?
13:03
Speaker 1: Yes, so that does not count as welding. Soldering and
13:07
Speaker 1: welding are two different things. So welding is when you
13:10
Speaker 1: melt two pieces of metal, so the metals themselves join
13:14
Speaker 1: become like one piece. So you got two objects you
13:17
Speaker 1: want to stick them together. You actually melt the edges
13:20
Speaker 1: of both of them. Soldering is different soldering. You have
13:23
Speaker 1: a lower temperature filler, something which melts at a much
13:26
Speaker 1: lower temperature that basically acts as glue and bonds to
13:30
Speaker 1: the two surfaces. But you don't actually melt the two
13:33
Speaker 1: things you're sticking together. So you got two pipes you
13:35
Speaker 1: want to stick together, you can solder them together. By
13:38
Speaker 1: melting some filler material which sticks them together, or you
13:42
Speaker 1: can actually weld them by melting the two pipes and
13:45
Speaker 1: sticking them together when they're liquid, so when they cool,
13:47
Speaker 1: you get those chemical bonds between them.
13:50
Speaker 2: But soldering is still cool because you get you used
13:51
Speaker 2: a bload. I was kind of torn when I opened
13:55
Speaker 2: up the walls and there was pets. Part of me
13:57
Speaker 2: wanted to solder, part of me did, But anyway, okay,
14:00
Speaker 2: I'm getting a soft track.
14:01
Speaker 1: And soldering somebody. You can do an electrical laborate. You
14:04
Speaker 1: have that special solder material which you touch to the
14:06
Speaker 1: tip of the soldering iron. It just like instantly liquifies, right,
14:10
Speaker 1: super cool stuff, and that stuff you use because it
14:13
Speaker 1: liquifies very very easily, and then it cools very quickly
14:16
Speaker 1: and becomes solid again. So that's soldering. But welding is different, right.
14:20
Speaker 1: Welding is when you really want to join these two
14:22
Speaker 1: materials and you do it by some combination usually of
14:25
Speaker 1: heat and pressure.
14:27
Speaker 2: Okay, and I'm guessing that we've been welding. It's got
14:31
Speaker 2: to be after we get access to fire. How much
14:36
Speaker 2: after we get access to fire before we're welding.
14:39
Speaker 1: Yeah, welding technically is something we've been doing for thousands
14:42
Speaker 1: of years. Essentially, blacksmiths invented welding. They notice you got
14:47
Speaker 1: two pieces of metal, you heat them up and pound
14:50
Speaker 1: them hard enough. They will join a lot of the
14:52
Speaker 1: stuff that's been connected together to make basic swords and
14:56
Speaker 1: tools for farms and all this stuff that blacksmiths have
14:59
Speaker 1: been making for thousands of years. They called that forge welding. Basically,
15:03
Speaker 1: heat it up and hammer it hard and you will
15:05
Speaker 1: get that fusion, that connection between the two materials that
15:09
Speaker 1: tells you that they are now one.
15:11
Speaker 2: Okay, So they're using like a furnace, Is that the
15:16
Speaker 2: most typical way or a blowtorch? Is that the most
15:19
Speaker 2: typical way to get the heat that you need to
15:21
Speaker 2: combine two metals.
15:22
Speaker 1: Yeah, exactly. And when my dad retired from Los Almo's
15:26
Speaker 1: National Labs, he actually took up blacksmithing as a hobby.
15:29
Speaker 1: I was pretty sure he was like preparing for the
15:31
Speaker 1: end times. He thought, like, what would be a useful
15:34
Speaker 1: skill to have if civilization collapsed, and he decided blacksmithing
15:38
Speaker 1: would be useful, And so he got a little furnace
15:42
Speaker 1: and he would go to the dump and like pick
15:44
Speaker 1: up scrap metal, you know, like truck suspensions and all
15:47
Speaker 1: sorts of stuff, and he would melt it down and
15:49
Speaker 1: hammer it into shapes. And he made all sorts of
15:51
Speaker 1: stuff from like towel hooks to his own spears and
15:55
Speaker 1: stuff like that.
15:57
Speaker 2: Whoa, that's awesome.
15:59
Speaker 1: It was pretty cool until half the town burnt down
16:02
Speaker 1: in a forest fire, which is a real tragedy. And
16:05
Speaker 1: then the neighbors were a lot less keen on him
16:07
Speaker 1: having like a thousands of degrees furnace in his garage
16:11
Speaker 1: spewing up sparks into the dry woods. So he got
16:14
Speaker 1: shut down. Yeah, reasonable, reasonable, yep.
16:18
Speaker 2: But said, hey, do you know what turneski?
16:21
Speaker 1: I don't. Who's that?
16:22
Speaker 2: I think he's the current blacksmith that loaves Alabos and
16:24
Speaker 2: he's a friend of mine. Oh, right, back and off, okay, okay,
16:29
Speaker 2: So I was trying to get you to talk about electricity.
16:31
Speaker 1: Yeah, but blacksmithing is an ancient form of welding, right,
16:35
Speaker 1: You heat it up, you squish it together, and what's
16:37
Speaker 1: happening there is that the metals on one side and
16:39
Speaker 1: the metals on the other side are bonding together, and
16:42
Speaker 1: so there's really no distinction there. And that makes a
16:44
Speaker 1: very very strong connection. Right. But in the late nineteenth
16:48
Speaker 1: century we invented arc welding. We had electricity now, and
16:52
Speaker 1: see we could more efficiently deliver energy than just like
16:55
Speaker 1: sticking the whole thing in an oven, which also isn't
16:58
Speaker 1: possible if you don't have a big enough oven. You
17:01
Speaker 1: want to weld together two I beams, you don't want
17:03
Speaker 1: to have to stick the whole thing in the oven
17:04
Speaker 1: and then hammer them together. You want to only heat
17:07
Speaker 1: at the spot that between them that's touching.
17:09
Speaker 2: So what is more dangerous a giant furnace operating at
17:13
Speaker 2: intense heat or electrifying metals and working with fads. Kid
17:18
Speaker 2: one is not allowed to listen to the episode up
17:20
Speaker 2: to this point yet, let's see where we get to.
17:24
Speaker 1: But our welding is actually really cool because it basically
17:27
Speaker 1: makes a circuit. You're running electricity through the metals, and
17:31
Speaker 1: because the metals are not perfect conductors, there's some resistance
17:35
Speaker 1: to them, and resistance means heat resistance. You're turning electrical
17:39
Speaker 1: energy into thermal energy. Like the way a light bulb
17:42
Speaker 1: works is you're running electrical current through something which is
17:46
Speaker 1: a resistorance. It's gonna heat up and then it's going
17:48
Speaker 1: to glow. So the reason the metals get hot is
17:51
Speaker 1: the same reason that a light bulb glows.
17:54
Speaker 2: Ah, And so we just don't let it get out
17:57
Speaker 2: of control because you don't want your light bulbs burning
18:00
Speaker 2: or melting.
18:01
Speaker 1: That's right. And so in arc welding, what you're doing
18:04
Speaker 1: is creating a circuit, and then you're passing that electricity
18:07
Speaker 1: from a stick which arcs onto the spot that you're
18:10
Speaker 1: trying to weld, passes energy through that and then completes
18:14
Speaker 1: the circuit. And so you just power that electricity back
18:17
Speaker 1: and forth. You can be DC, you can be acy,
18:20
Speaker 1: all sorts of varieties of it. It was meant that
18:23
Speaker 1: in the eighteen hundreds when people were learning about the
18:25
Speaker 1: power of electricity.
18:27
Speaker 2: You know, you've got me wondering now, fun tangent. So
18:30
Speaker 2: the first the first space walk ever conducted by a
18:34
Speaker 2: woman was a sptlanasub Atskaya, and she welded in the
18:39
Speaker 2: vacuum of space for the first time. So do you
18:42
Speaker 2: think that she welded with heat or electricity?
18:47
Speaker 1: I suspect that was an arc welding, right, because the
18:50
Speaker 1: heat generation from like a blowtorch might require combustion with
18:53
Speaker 1: the atmosphere respect that was probably arc welding.
18:57
Speaker 2: Yeah, oh I should have known that. As soon as
18:59
Speaker 2: you started saying it, I was like, oh, of course.
19:02
Speaker 2: But anyway, all right, so fun, Yeah, there you go.
19:04
Speaker 1: But hold on, that sounds super dangerous. You have this
19:07
Speaker 1: like arc welding in space. I mean that could easily
19:11
Speaker 1: rupture a suit or cause some damage. So that seems
19:14
Speaker 1: crazy to me.
19:15
Speaker 2: Well, you know what's infuriating she is this like hypercompetent,
19:19
Speaker 2: incredible cosmonaut. And there's this movie called Solute seven that
19:23
Speaker 2: came out in Russia and it's sort of like Solute
19:25
Speaker 2: seven is almost their equivalent to our Apollo thirteen. So
19:29
Speaker 2: Solute seven like they had a problem I think it
19:32
Speaker 2: was with the solar panels and the power ran down,
19:36
Speaker 2: so they had to send somebody up there to try
19:37
Speaker 2: to fix it and get it back online. But at
19:40
Speaker 2: the beginning of the movie they create this scene where
19:43
Speaker 2: Setlanasovitskaya is welding in space, which happens, but she gets
19:48
Speaker 2: a welding burr in her glove and she's starting to
19:50
Speaker 2: lose pressure and her male colleague needs to pull her
19:54
Speaker 2: back into the station because she just like I don't know.
19:57
Speaker 2: It's like losing her composure. And that didn't happen. She
20:01
Speaker 2: did a great job of welding. She didn't get a
20:03
Speaker 2: burr in her glove. She didn't need to be saved
20:05
Speaker 2: by a man. But that's how the movie starts, and
20:09
Speaker 2: that made me very frustrated. Tangent done. Oh and the
20:14
Speaker 2: rest No, no, almost done, Tangent almost done. The other
20:18
Speaker 2: big lie in the movie is that they need to
20:19
Speaker 2: get up there to get the station started again because
20:23
Speaker 2: the shuttle, the Americans are going to set off the
20:25
Speaker 2: Shuttle and they want our technology, so they're going to
20:28
Speaker 2: put the Salute seven space station in the shuttle's cargo
20:33
Speaker 2: bay and take it back to Earth to steal our technology,
20:37
Speaker 2: which it wouldn't fit. That didn't happen, but that's like
20:42
Speaker 2: a huge and at the very end you've got the
20:44
Speaker 2: Space Shuttle driving past Salute and the Space Shuttle people
20:47
Speaker 2: who are driving Salute the Solute cosmonauts for doing such
20:50
Speaker 2: a good job of getting it fixed before they could
20:52
Speaker 2: go there to steal it. And it was like what anyway,
20:56
Speaker 2: a classic film, Like all.
21:00
Speaker 1: The research you did for your space settlement book may
21:02
Speaker 1: have ruined you for science fiction Kelly.
21:05
Speaker 2: Ah, yeah, yeah, that's probably true.
21:09
Speaker 1: That's the downside of knowing a bunch of stuff.
21:11
Speaker 2: Better not to know.
21:14
Speaker 1: So in the eighteen hundreds we developed this new technique
21:17
Speaker 1: like basically the first advance since blacksmithing for thousands of
21:21
Speaker 1: years in how to join metals. And this got really
21:24
Speaker 1: fast forwarded in the World Wars in the early nineteen
21:27
Speaker 1: hundreds because people wanted to make lots and lots of
21:30
Speaker 1: tanks and airplanes and all sorts of stuff, and arc
21:34
Speaker 1: welding can be a little bit painful, it's kind of slow,
21:37
Speaker 1: and it can be inefficient, and so they developed lots
21:40
Speaker 1: more techniques to do this much more quickly, to do
21:42
Speaker 1: it much more efficiently. So fast welding really was born
21:46
Speaker 1: in the first part of last century because of the
21:49
Speaker 1: World Wars, humans wanted to kill each other more efficiently,
21:52
Speaker 1: so they had to be quick at building those killing machines.
21:56
Speaker 2: So depressing. Same goes for rockets, right, that's the rockets
22:00
Speaker 2: took us to the Moon. We're used to drop bombs
22:02
Speaker 2: on London without great aim, I'd say, But anyway, Yeah, it's.
22:06
Speaker 1: A conflict I feel deeply internally. I mean a lot
22:09
Speaker 1: of advances in physics come from wanting to build weapons
22:12
Speaker 1: of mass destruction, and so that's you know, also where
22:16
Speaker 1: a lot of fund incomes from. But it does, in
22:18
Speaker 1: the end reveal a lot about the nature of the universe.
22:20
Speaker 1: So it's a tough situation, yep. But it turns out
22:23
Speaker 1: that you could apply a lot of these welding techniques
22:26
Speaker 1: not just to metals. You can also weld things like glass. Right,
22:30
Speaker 1: you can take two pieces of glass and you can
22:32
Speaker 1: have a glass rod, and you can use a blowtorch
22:35
Speaker 1: to melt the glass and stick them together. And so
22:37
Speaker 1: you can weld pieces of glass together. You can even
22:40
Speaker 1: weld glass to ceramic or to steal all sorts of stuff.
22:44
Speaker 1: So welding is not just something you have to do
22:46
Speaker 1: with metals.
22:47
Speaker 2: I didn't realize that. I guess I did think welding
22:50
Speaker 2: was metal specific.
22:51
Speaker 1: Yeah, it's basically just joining stuff together by melting them.
22:55
Speaker 1: And it makes a lot of sense because you melt
22:57
Speaker 1: it together and that the atoms are all jiggling and
22:59
Speaker 1: they can and jiggle together and when they cool, it's
23:02
Speaker 1: like they're one again. What sort of mysterious is doing
23:05
Speaker 1: this without heat? And so cold welding is a much stranger,
23:10
Speaker 1: much more interesting and maybe potentially useful in space kind
23:14
Speaker 1: of process.
23:15
Speaker 2: And we're going to learn more about it after the break.
23:30
Speaker 2: All right, So, hot welding uses heat to combine metal, glass, plastic,
23:35
Speaker 2: and steal. But you have told me that we can
23:39
Speaker 2: do it without heat, and so maybe my daughter can
23:42
Speaker 2: listen to this part of the episode. So how do
23:46
Speaker 2: we do that? Do we just bang them together really
23:48
Speaker 2: hard and hope they stick.
23:52
Speaker 1: That's the long and short of it. Yes, essentially you
23:54
Speaker 1: can do cold welding if you have pressure and if
23:58
Speaker 1: the materials are very, very very clean. Think about what's
24:01
Speaker 1: happening inside of metal. Metal is essentially a crystal. You
24:05
Speaker 1: have all of these atoms of iron or whatever, and
24:08
Speaker 1: they're lining up in a crystal, and the reason they're
24:11
Speaker 1: so strong is all those bonds are holding them together.
24:13
Speaker 1: How do you make a bigger crystal? Well, you could
24:15
Speaker 1: like rejigger all the atoms and make them liquid again
24:19
Speaker 1: and then stick them together so they cool back down
24:21
Speaker 1: to make a crystal. But what if you just have
24:23
Speaker 1: like half of a crystal here and half of a
24:25
Speaker 1: crystal there, and you just like stick them together so
24:29
Speaker 1: that the two bits of crystal like link together, sort
24:32
Speaker 1: of like sticking two puzzle pieces together.
24:34
Speaker 3: Right.
24:34
Speaker 1: You don't have to melt them down to liquid cardboard
24:37
Speaker 1: to make to stick them together. You just sort of
24:40
Speaker 1: fit the nibs into the holes and they click together
24:43
Speaker 1: into one big picture. Okay, So that's the sort of
24:47
Speaker 1: idea behind cold welding. Like, if you have a material
24:50
Speaker 1: that's very regular and you have two pieces of it,
24:52
Speaker 1: if you just get them together close enough and apply
24:55
Speaker 1: a little bit of pressure, they will all of a
24:57
Speaker 1: sudden act like they were always one thing. They will
25:00
Speaker 1: just sort of like stick together.
25:02
Speaker 2: All right. So I'm having a little trouble wrapping my
25:05
Speaker 2: head around it. So I'm imagining like, all right, so
25:07
Speaker 2: you put two pieces of metal together, and very very
25:10
Speaker 2: very slowly they start what like acting like liquid and
25:15
Speaker 2: sort of mixing together or yeah, why so why does that?
25:20
Speaker 2: Why does that happen?
25:21
Speaker 1: It's not very very slow. The whole thing can happen
25:24
Speaker 1: in seconds or less, and there's no liquid involved. This
25:28
Speaker 1: is just two pieces of metal clicking together. I read
25:33
Speaker 1: this fun quote by Richard Feinman. He says, quote, the
25:36
Speaker 1: reason for this unexpected behavior is that when the atoms
25:39
Speaker 1: in contact are all of the same kind. There's no
25:43
Speaker 1: way for the atoms to know they are in different
25:45
Speaker 1: pieces of copper. Essentially, you just have like a bunch
25:48
Speaker 1: of copper here and a bunch of copper there. You
25:50
Speaker 1: bring them close together, they will stick together. They do
25:53
Speaker 1: like to bond to each other. Think about what happens
25:56
Speaker 1: between two atoms of copper. There are electrons that are
25:58
Speaker 1: like flowing between them, bonding them together. That's what the
26:01
Speaker 1: bond is, right, The actual nuclei are and stuck together.
26:04
Speaker 1: It's thee electrons between them. And so if you have
26:07
Speaker 1: two atoms you bring them near each other, they will bond.
26:10
Speaker 1: They don't have to become a liquid in order to
26:13
Speaker 1: bond together.
26:14
Speaker 2: So why do metals do this? And like the I've
26:18
Speaker 2: got a book sitting next to me with lots of pages,
26:20
Speaker 2: but the pages are staying distinct. Why why doesn't everything
26:25
Speaker 2: start just sort of blending together.
26:30
Speaker 1: Exactly? Why isn't the whole world just fuse the one
26:33
Speaker 1: lump right exactly? Yes, this is something metals can do
26:38
Speaker 1: because the electrons in a metal are very mobile. Like
26:42
Speaker 1: some materials, the electrons mostly stick around their own atom
26:45
Speaker 1: or the neighboring atom. But when metals come together the
26:49
Speaker 1: energy levels of those electrons are such that the electrons
26:52
Speaker 1: can really flow freely through the metal. It's more like
26:55
Speaker 1: an ocean of electrons. And this all depends on how
26:58
Speaker 1: the energy levels translate. Like you have an individual atom,
27:02
Speaker 1: we know that the electrons around that atom have energy levels.
27:05
Speaker 1: Like you remember from your high school chemistry that there's
27:07
Speaker 1: like the one p orbital and the four f orbital,
27:10
Speaker 1: and there's all these energy levels for an electron.
27:12
Speaker 2: We shouldn't assume I remember anything from high school chemistry,
27:15
Speaker 2: but keep going.
27:16
Speaker 1: I don't remember it either. I probably just remember it
27:17
Speaker 1: because my son is taking high school chemistry, so I
27:20
Speaker 1: have to hear about all this stuff. Anyway, Electrons around
27:24
Speaker 1: atoms have energy levels, right, Well, what happens when you
27:28
Speaker 1: have two atoms and now your electrons are sort of
27:30
Speaker 1: like zigging back and forth between those two atoms. Well,
27:33
Speaker 1: the energy levels get more complicated because you're now responding
27:37
Speaker 1: to the positive charge of two atoms. Now add another atom,
27:40
Speaker 1: and another atom and another atom. You get a whole
27:42
Speaker 1: crystal lattice. And so now you get a bunch of
27:44
Speaker 1: different energy levels for the electrons. And metals and insulators
27:49
Speaker 1: have different kinds of energy levels there. In metals, it's
27:53
Speaker 1: very easy for the electrons to jump up to the
27:55
Speaker 1: higher energy levels and then move around the whole atom.
27:58
Speaker 1: In insulators is like a big gap, then the electrons
28:01
Speaker 1: can't easily get up there, so they're sort of like
28:04
Speaker 1: trapped around individual atoms more So, the short answer is,
28:08
Speaker 1: metals have a lot of electrons that are easy to
28:10
Speaker 1: flow around, and so if you bring two pieces of
28:12
Speaker 1: metal together, their electrons would just sort of like start
28:15
Speaker 1: flowing back and forth, and then the copper atoms will
28:17
Speaker 1: be like, hey, you're my neighbor. I'm your neighbor. Let's
28:20
Speaker 1: share electrons, and boom, they're bonded.
28:23
Speaker 2: So all right, So I've got these copper pipes m
28:27
Speaker 2: in a different part of my house, and and if
28:30
Speaker 2: you get this electron c and these metals can all
28:32
Speaker 2: like come together. Why do my copper pipes retain their shape?
28:38
Speaker 2: Why doesn't the like copper you know that's above or
28:42
Speaker 2: that's at the top of the pipe sort of like
28:44
Speaker 2: start moving into the copper that's at the bottom of
28:46
Speaker 2: the pipe, and it all just sort of like becomes
28:48
Speaker 2: a glob.
28:51
Speaker 1: Well, copper is pretty strong, right, it's crystal structure preserve itself,
28:55
Speaker 1: but when it comes next to another piece of that
28:57
Speaker 1: crystal structure, then they will link together. It's just like
29:00
Speaker 1: the puzzle pieces, right. Puzzle pieces hold themselves together into
29:04
Speaker 1: a shape, but if you bring them nearby into something
29:06
Speaker 1: else where where the nibs and the holes all match up,
29:09
Speaker 1: they will click in the place. The real question is,
29:12
Speaker 1: like you've touched copper together before, you didn't notice it,
29:15
Speaker 1: like cold welding together. Right. It's not like every time
29:18
Speaker 1: two copper pennies touch that they cold weld. It's not
29:22
Speaker 1: like every time you have change in your pocket you
29:24
Speaker 1: pull it out and it's like one single blob. Right,
29:27
Speaker 1: That would be pretty weird. And so why doesn't this
29:29
Speaker 1: happen all the time. The answer is that these materials
29:33
Speaker 1: have to be really really clean. Essentially, you need like
29:36
Speaker 1: really bare copper to touch really bare copper, or bar
29:39
Speaker 1: iron to touch bear iron, and that doesn't happen very
29:42
Speaker 1: often because we're in an atmosphere, and so the copper
29:46
Speaker 1: in your pipes interacts with the atmosphere and the oxygen
29:49
Speaker 1: in the atmosphere and forms like thin layers of oxides.
29:53
Speaker 1: So if you take two copper pipes and you bang
29:55
Speaker 1: them together, the copper is not actually touching. What's touching
29:58
Speaker 1: are these thin layers of sides and greases and all
30:01
Speaker 1: sorts of other stuff on the surface, So you're not
30:04
Speaker 1: really getting that clean contact.
30:06
Speaker 4: Is it?
30:07
Speaker 2: Also like a lot of the metals that you encounter
30:09
Speaker 2: that we encounter in our day to day lives, are
30:11
Speaker 2: they pure metals or are they also metals that have
30:14
Speaker 2: like other stuff mixed in.
30:16
Speaker 1: Yeah, a lot of the stuff we interact with are alloys, right,
30:19
Speaker 1: steel for example, there's all sorts of stuff mixed into it,
30:22
Speaker 1: and a lot of stuff we interact with are not
30:24
Speaker 1: pure metals. So this requires sort of a special situation.
30:27
Speaker 1: You need pure metals and you need them to be
30:30
Speaker 1: super duper clean, And so if you wanted to accomplish
30:34
Speaker 1: cold welding, what you got to do is like really
30:37
Speaker 1: carefully clean the surface. Sometimes you can actually just rub
30:40
Speaker 1: the two surfaces together in order to scrape them clear
30:43
Speaker 1: of these oxides, press them together, and they will make
30:46
Speaker 1: a metallic bond.
30:47
Speaker 2: So like if I rub my copper pipes, I know
30:51
Speaker 2: I'm stuck on the copper pipes. I rubbed the copper
30:53
Speaker 2: pipes together to clean them off and press them together.
30:56
Speaker 2: Is that going to be enough or know where we
30:57
Speaker 2: back to. Your copper pipes are probably not pure copper.
31:01
Speaker 1: It depends on the purity of your copper. But this
31:04
Speaker 1: is something you can actually accomplish like down here on
31:06
Speaker 1: Earth without special materials. It was first demonstrated in the
31:10
Speaker 1: mid seventeen hundreds by a guy in England who just
31:14
Speaker 1: took two lead balls and he pressed them together and
31:17
Speaker 1: twisted them and rubbed them together and the two pieces
31:19
Speaker 1: would join. This seemed like magic at the time. It's
31:22
Speaker 1: like without any heat, he's somehow turning two lead balls
31:25
Speaker 1: into one single thing of lead.
31:28
Speaker 2: Did they burn him at the state.
31:31
Speaker 1: Him and all the Vermont farmers, Yeah, exactly. This was
31:36
Speaker 1: in the or mid seventeen hundred, so seventeen twenty four
31:40
Speaker 1: by a guy named Reverend Dsagular I'm not sure if
31:44
Speaker 1: he's actually French, and it's like Disagulae, but he demonstrated
31:48
Speaker 1: this phenomenon to the Royal Society and published the details
31:51
Speaker 1: in a scientific journal at the time. So this is
31:54
Speaker 1: something you can accomplish with pretty normal materials, and then
31:58
Speaker 1: archaeologists discover the humans have actually been doing this for
32:01
Speaker 1: thousands of years. You don't need heat in order to
32:05
Speaker 1: accomplish welding as long as you have pressure and you
32:09
Speaker 1: have two clean materials. So people have found like gold
32:12
Speaker 1: boxes made by cold welding that date to like seven
32:17
Speaker 1: hundred BC.
32:18
Speaker 2: Okay, so this is going to be potentially another silly question.
32:22
Speaker 2: So these boxes were gold, and so if having them
32:27
Speaker 2: together is enough for them to weld, how do we
32:30
Speaker 2: know that they hadn't like that this gold wasn't like
32:33
Speaker 2: lining a wooden box and over time it cold welded
32:37
Speaker 2: on its own, Like, how do we know that they
32:39
Speaker 2: did it purposefully?
32:41
Speaker 4: Oh? Yeah?
32:41
Speaker 2: Or how do we know they didn't use hot welding.
32:44
Speaker 1: If you do hot welding, you can see the effects
32:46
Speaker 1: at the intersection, like you can see that it's been melted.
32:49
Speaker 1: It changes the chemical composition a little bit, and then
32:52
Speaker 1: there's a transition there between the heated part and the
32:54
Speaker 1: not heated part. So cold welding does look different from
32:57
Speaker 1: hot welding, so we can tell that this was not
33:00
Speaker 1: hot welded gold. Obviously, people have been doing goldsmithing also
33:03
Speaker 1: for thousands of years using heat and hammering, but these
33:06
Speaker 1: are cold welded materials. But you're right, it could have
33:10
Speaker 1: been accidental and probably the discovery of it was accidental.
33:13
Speaker 1: Somebody for some reason accidentally squeezed two pieces of gold
33:16
Speaker 1: together and discovered they had welded. And you know, I
33:19
Speaker 1: hope that was a happy accident for whoever was doing that.
33:24
Speaker 2: Oh, happy accident.
33:26
Speaker 1: But it's sort of amazing that you can do this,
33:29
Speaker 1: you know. On one hand, it seems sort of crazy,
33:31
Speaker 1: like you stick two things together and they like talk
33:33
Speaker 1: to each other, and they like intermingle themselves and click together.
33:37
Speaker 1: It seems kind of impossible to get everything lined up right.
33:41
Speaker 1: On the other hand, it seems kind of obvious because
33:44
Speaker 1: copper is copper. Like you make copper crystal over here
33:47
Speaker 1: and you make copper crystal over there. They're gonna have
33:50
Speaker 1: the same atomic spacing. It's basically the same stuff. It's
33:53
Speaker 1: ready to get clicked together. You push on it a
33:56
Speaker 1: little bit, and those atoms are just gonna happily line
33:59
Speaker 1: up and interact with their new neighbors. It doesn't really
34:02
Speaker 1: matter that they used to be separate. When to push
34:04
Speaker 1: them together, they're ready to grab onto each other.
34:07
Speaker 2: I feel like once you explain the concept to me,
34:09
Speaker 2: it's less surprising to me that it happens and more
34:12
Speaker 2: surprising to me that it doesn't happen, Yes, all the time.
34:17
Speaker 2: Are there examples of it happening when it's not when
34:20
Speaker 2: it wasn't intended to happen.
34:22
Speaker 1: Oh, there's lots of examples of it happening when it
34:24
Speaker 1: wasn't intended, especially in the space program, which we'll get
34:28
Speaker 1: into in a little bit. It's a little bit complex
34:30
Speaker 1: to make it happen for more complex materials, like if
34:33
Speaker 1: you imagine something that's an alloy or an ionic solid.
34:36
Speaker 1: These things really are more complex because they have lots
34:39
Speaker 1: of different components to them, and so getting everything lined
34:42
Speaker 1: up is more tricky. I think it is possible in
34:45
Speaker 1: principle to cold well things that are not like pure
34:48
Speaker 1: copper or pure gold. It's just harder. You basically need
34:51
Speaker 1: more pressure and more time and a little bit more
34:54
Speaker 1: luck to make sure everything actually does line up against itself.
34:58
Speaker 1: But we have used cold welding, and there's been examples
35:01
Speaker 1: of on purpose and accidental cold welding in the environment
35:05
Speaker 1: of space.
35:06
Speaker 2: All right, Well, before we get to welding in space
35:09
Speaker 2: space space, let's take a commercial break. Okay, we're back,
35:27
Speaker 2: all right, So you promised me stories about cold welding
35:31
Speaker 2: happening when we didn't want it to happen. But you
35:34
Speaker 2: told me that I had to wait till we got
35:35
Speaker 2: to the space part of the episode, which is almost certainly,
35:39
Speaker 2: you know, always my favorite part of any episode. So
35:42
Speaker 2: tell me about how space poses unique challenges and benefits
35:46
Speaker 2: for welding.
35:48
Speaker 1: Yeah, so space is sort of an obvious place you
35:50
Speaker 1: might want to do cold welding because there's no atmosphere,
35:54
Speaker 1: which means there's nothing to oxidize your materials. You have
35:58
Speaker 1: a piece of bare pure cop or whatever, it's gonna
36:01
Speaker 1: stay bare pure copper. You don't need to like scrub
36:04
Speaker 1: the surface to get the oxides off because there's no
36:06
Speaker 1: oxygen to make any oxides, So there's no like gas
36:10
Speaker 1: in the middle there to interfear, no impurities, Your bare
36:13
Speaker 1: stuff stays bear stuff.
36:15
Speaker 2: Have we used that to our advantage yet? Like, do
36:19
Speaker 2: we are there things that we decide we're just gonna
36:21
Speaker 2: put together in space because we're gonna send clean stuff
36:23
Speaker 2: up there and then assemble it with cold welding while
36:25
Speaker 2: it gets up there.
36:26
Speaker 1: You know, it seems like an obvious application, but I
36:28
Speaker 1: couldn't actually find an example of times this had been
36:31
Speaker 1: done intentionally and It seems to me like a great
36:35
Speaker 1: idea because having any sort of like intense heat in
36:39
Speaker 1: space seems pretty dangerous. Like the story you told us
36:42
Speaker 1: was terrifying to me, because you know, on Earth, you
36:45
Speaker 1: accidentally bring your heat too close to something, it melts
36:48
Speaker 1: or maybe you get a burn or something. But in
36:49
Speaker 1: space you destroy your spacesuit. Right, everything is so much
36:53
Speaker 1: more dangerous out there in space. It seems like it
36:56
Speaker 1: would be awesome to do welding without the danger of
36:59
Speaker 1: heat or like super high electrical arcing.
37:02
Speaker 2: Yeah, space sucks.
37:03
Speaker 1: Space sucks exactly. I did find a couple of examples
37:07
Speaker 1: of accidental space welding go on. In nineteen sixty five,
37:12
Speaker 1: Gemini four was the first American spacewalk. So they sent
37:16
Speaker 1: the guy out there, They open the hatch. He goes
37:18
Speaker 1: out there, he space walks all around, He's having a
37:21
Speaker 1: great time. They asked him to come back in. He
37:22
Speaker 1: actually didn't want to come back in because he was
37:24
Speaker 1: having so much fun. And when he came back in
37:28
Speaker 1: and they couldn't close the hatch again, the hatch was
37:30
Speaker 1: like stuck in the open position. They had to like
37:33
Speaker 1: really yank on it, which is not a situation you
37:36
Speaker 1: want to be in when you're out in space and
37:37
Speaker 1: you like can't close the door.
37:40
Speaker 2: No, no, you know. Apparently apparently the same thing happened
37:43
Speaker 2: during the first Soviet space walk. Are you familiar with
37:45
Speaker 2: this story?
37:46
Speaker 1: No, what happened.
37:47
Speaker 2: It doesn't have to do with cold welding. But Alexei
37:50
Speaker 2: Leonov went out to do the first space walk ever
37:52
Speaker 2: because I think they beat us to that too, and
37:55
Speaker 2: he couldn't get back in, and he's known to exaggerate
37:59
Speaker 2: his stories a bit like astronauts. That's right, Well, I
38:02
Speaker 2: would too if I was an astronaut. But I think,
38:05
Speaker 2: you know, like his suit. You know, he got out
38:06
Speaker 2: into the vacuum of space and his suit sort of
38:09
Speaker 2: like puffed up a little bit because you know, you
38:10
Speaker 2: pressurize your suit, and after it got a little like puffy.
38:14
Speaker 2: Or My understanding is either he couldn't get through the
38:16
Speaker 2: hatch or he couldn't like bend the way he needed to,
38:19
Speaker 2: so for a second there he couldn't get back in.
38:21
Speaker 2: But I guess in both cases they managed to get
38:23
Speaker 2: the astronaut back in and bring them back home safely,
38:25
Speaker 2: thank goodness.
38:26
Speaker 1: Who Well, in this case, NASA was trying to figure
38:29
Speaker 1: out like why did the hatch get stuck? Kind of
38:31
Speaker 1: an important thing to understand, And one of the initial
38:34
Speaker 1: suggestions was cold welding. That maybe, like the outside of
38:38
Speaker 1: the hatch cold welded itself to the surface of the spaceship.
38:42
Speaker 1: And you know, this is the kind of thing we're
38:44
Speaker 1: not used to worrying about. On the surface of the Earth.
38:46
Speaker 1: You don't worry about like your keys cold welding themselves
38:49
Speaker 1: to your car and stuff, because everything's covered, right, this
38:51
Speaker 1: pint or this oxidation or just plain dirt is keeping
38:54
Speaker 1: stuff from cold welding. But in space this is maybe
38:57
Speaker 1: something we had to worry about, Like anytime two metals touch,
39:00
Speaker 1: are we gonna worry about them like spot welding themselves together?
39:03
Speaker 1: Oh my god, I know. And actually, if you look online,
39:06
Speaker 1: there's a lot of lore about how this is an
39:08
Speaker 1: example of cold welding. But you dig a little bit
39:10
Speaker 1: deeper and it turns out it's actually not cold welding
39:13
Speaker 1: at all. When it came back down to Earth, the
39:15
Speaker 1: engineers dug into it and they found out it was
39:18
Speaker 1: just a stuck spring that didn't compress right. So like
39:21
Speaker 1: very normal door not working.
39:24
Speaker 2: Okay, so you gave us like a psych moment could
39:27
Speaker 2: be cold welding, but it's not. Is there are there
39:30
Speaker 2: any actual cold welding examples in space or are you
39:34
Speaker 2: just gonna keep messing with us?
39:36
Speaker 1: No, there is one real example, and this is the
39:39
Speaker 1: Galileo probe. And so this is a probe which went
39:42
Speaker 1: out to explore the Solar System and take pictures of Jupiter,
39:45
Speaker 1: for example, but it got delayed.
39:48
Speaker 2: Wait, NASA, there were delays in a NASA project.
39:50
Speaker 1: I know, shocking, right, And the spacecraft was like moved
39:54
Speaker 1: across the country multiple times, and during those transports, like
40:00
Speaker 1: shaking a bunch, and the lubrication that was supposed to
40:03
Speaker 1: protect the metals from cold welding together eroded away. And
40:07
Speaker 1: so when they launched this thing, and then they were
40:09
Speaker 1: supposed to unfurl the high gain antenna, the thing that
40:13
Speaker 1: was going to send us data back with images of
40:15
Speaker 1: Jupiter on it, it turns out that several of the
40:18
Speaker 1: metal struts had become cold welded together, and so it
40:22
Speaker 1: couldn't unfurl.
40:23
Speaker 4: No.
40:24
Speaker 2: Oh, and they even planned for it, and that did
40:27
Speaker 2: planning didn't work. Oh my gosh, I'm getting stressed just
40:29
Speaker 2: thinking about it. They did they find a way around it,
40:32
Speaker 2: or were they just stuck.
40:34
Speaker 1: They never got the high gain intended to work. Fortunately,
40:36
Speaker 1: there's always like redundancies on these craft, and they had
40:39
Speaker 1: the low gain antenna which was not designed to be
40:41
Speaker 1: used to like send data. It was more like for
40:43
Speaker 1: control systems. But they had to reprogram it and use
40:46
Speaker 1: it to send the actual pictures, which like delayed people
40:49
Speaker 1: seeing these images of Jupiter. But of course you know,
40:52
Speaker 1: we got them. It's just more like downloading on one
40:54
Speaker 1: of those slow modems rather than your high speed internet.
40:58
Speaker 2: Yeah, but still, oh my goodness, those engineers they figured
41:00
Speaker 2: it out, Thank goodness. I'm sure there were a lot
41:02
Speaker 2: of PhD students who were like, I can stay in
41:04
Speaker 2: grad school for another year or two, that's fine, but
41:07
Speaker 2: at least I'm gonna get my images eventually.
41:09
Speaker 3: I know.
41:10
Speaker 1: It's like the old days when you're down the neck
41:11
Speaker 1: picture and you're seeing one row of pixels at a
41:13
Speaker 1: time come across the screen and you're like, what am
41:15
Speaker 1: I looking at? I download the right picture or not
41:18
Speaker 1: a worry?
41:19
Speaker 2: And you go do my computer freeze or should I
41:21
Speaker 2: shut it down? Or should do I wait? Yeah?
41:24
Speaker 1: Fun, So in practice, it's not really that big a problem.
41:26
Speaker 1: It's not like when we build big space stations or
41:29
Speaker 1: space settlement, we're gonna have to worry about cold welding
41:31
Speaker 1: all the time. You really need like perfectly clean materials
41:35
Speaker 1: and they have to be pressed together for long enough
41:37
Speaker 1: for this to happen. So not really a huge concern in.
41:41
Speaker 2: Space, all right, So are there any other applications that
41:45
Speaker 2: we should chat about.
41:46
Speaker 1: People have discovered that cold welling can also be really
41:49
Speaker 1: helpful for nano circuits, Like you want to build really
41:53
Speaker 1: really small electronics in these days, the trend is to
41:55
Speaker 1: build like tinier and tinier microchips, which use less power
41:58
Speaker 1: and can be squeezed into all sorts of scenarios, so
42:01
Speaker 1: you can have like microchips in your cereal or whatever
42:04
Speaker 1: you need, you know exactly, you know, they can count
42:09
Speaker 1: your calories for you, right exactly. Anyway, nanoscale fabrication is
42:15
Speaker 1: tricky because spot welding is very hard. When it's really
42:18
Speaker 1: really tiny, you know, basically need like tiny sources of
42:21
Speaker 1: heat or you need this electricity to arc perfectly. Well,
42:25
Speaker 1: what they've discovered is that you can do cold welding
42:27
Speaker 1: for nanofabrication. I read this paper that came out of
42:31
Speaker 1: nature like ten years ago where they had ultra thin
42:34
Speaker 1: gold nano wires and you just bring them together and
42:37
Speaker 1: if the edges touch, boom, they cold well together within seconds.
42:41
Speaker 1: You don't even need a lot of pressure. Whoa yeah.
42:45
Speaker 1: And these wires once they've cold welded together essentially as
42:48
Speaker 1: like a near perfect bond. They did all these tests
42:51
Speaker 1: of like the electrical conductivity and a crystal orientation, and
42:55
Speaker 1: it's as if it was always just one wire. So
42:59
Speaker 1: this means, Kelly, do need your children, with like their
43:01
Speaker 1: delicate little fingers to do tiny little arc welding on
43:05
Speaker 1: our nano circuits?
43:06
Speaker 2: Oh? Good, good, because that was gonna be a thing.
43:10
Speaker 1: But it might be that we can send your kids
43:12
Speaker 1: down the space to do space construction jobs without arc welding. Right,
43:16
Speaker 1: how do you.
43:16
Speaker 2: Feel about that any of the episode? Nope, none of
43:19
Speaker 2: the episode. None.
43:21
Speaker 1: If your kids grow up and they want to work
43:23
Speaker 1: construction in space, you're gonna say no, yes, no. You
43:28
Speaker 1: didn't think about that deeply at all. It was just
43:30
Speaker 1: like a straight up no.
43:32
Speaker 2: I hope they don't go that route, but if they do,
43:34
Speaker 2: I will support them grudgingly.
43:38
Speaker 1: Well, I think cold welding is super fascinating, and what
43:40
Speaker 1: it tells me is that there's a lot more to
43:41
Speaker 1: understand about how these particles weave themselves together to make
43:45
Speaker 1: the sort of macroscopic materials that we're familiar with, and
43:48
Speaker 1: that there's still sort of magic left. I mean, I'm
43:50
Speaker 1: not talking about Vermont Farmer magic. I'm talking about accomplishing
43:54
Speaker 1: things that seem impossible to us, you know, just like
43:57
Speaker 1: sticking two pieces of metal together and make them into
43:59
Speaker 1: one metal. Every time there's an advancement in material science,
44:03
Speaker 1: it feels almost like we're creating real magic.
44:06
Speaker 2: I agree, but I still feel like the main takeaway
44:09
Speaker 2: for me is one more thing to worry about in
44:11
Speaker 2: space because cold welding going wrong. We should have gotten
44:16
Speaker 2: that in the book.
44:17
Speaker 1: I think you already had like a thousand reasons not
44:20
Speaker 1: to build in space in your book. You don't need
44:21
Speaker 1: another reason. Yeah, I guess beat that dead horse. And
44:27
Speaker 1: as much as I'm jokingly negative about chemistry, it does
44:31
Speaker 1: really give us access to the microscopic nature of materials.
44:35
Speaker 1: It's the easiest way to see these emergent properties, to
44:38
Speaker 1: see how something can be sticky or shiny or brittle
44:41
Speaker 1: because of the way the particles inside it interact and
44:45
Speaker 1: cold welding is just another manifestation of that that our
44:48
Speaker 1: world really is dominated by the microscopic rules that somehow
44:51
Speaker 1: bubble up to make this incredible variety of behaviors and phenomena.
44:56
Speaker 2: Yeah, I gotta give it to you chemistries pretty much.
44:58
Speaker 1: It is kind of magic, dang it. Yeah.
45:02
Speaker 2: Yeah, my chemistry professors kept telling me that, but but
45:07
Speaker 2: now I believe it.
45:09
Speaker 1: Finally, thirty years later, I've learned it too.
45:13
Speaker 2: Thirty Oh, why you might be on it?
45:17
Speaker 1: All right? Well, thanks Kelly for joining us on this
45:19
Speaker 1: tour of chemistry and magic and this dive into how
45:23
Speaker 1: cold welding works.
45:24
Speaker 2: Thanks for having me.
45:25
Speaker 1: All right, Everyone, keep wondering about how the universe works
45:28
Speaker 1: and send us your questions. This episode was inspired by
45:31
Speaker 1: listeners who wanted to understand how cold welding works. If
45:34
Speaker 1: you have ideas for things you'd like to hear us explore,
45:37
Speaker 1: please don't be shy. Write to me two questions at
45:40
Speaker 1: Danielandhorge dot com. Tune in next time. Thanks very much.
45:49
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45:52
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46:00
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