February 22, 2024 • 46 mins
Daniel and Kelly talk about how its possible to merge metals without melting!
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Speaker 1 (00:08):
Hey, Kelly, how are things going on the science farm?
Speaker 2 (00:11):
You know, they're going pretty well, but we have some
old pipes and they've been sailing and so, you know,
renovating the bathroom in the kitchen. We're pretty low on
why to do list, but suddenly they went to the
top and so there's been lots of renovating projects happening.
Speaker 1 (00:26):
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.
Speaker 2 (00:34):
Uh, 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.
Speaker 1 (00:45):
Tools, not until they hear this episode and then they
start asking for their turn.
Speaker 2 (00:50):
This is why my kids don't get to listen to
your podcast.
Speaker 1 (00:52):
Man, how can you consider yourself a good parent if
you don't share this podcast with them.
Speaker 2 (00:58):
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 just seem to be tied to them not
listening to your podcast.
Speaker 1 (01:10):
Fair point. Hi, I'm Daniel, I'm a particle physicist and
a professor at UC Irvine, and I want everybody's kids
(01:31):
to stay happy and healthy.
Speaker 2 (01:33):
I'm Kelly Wieder 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 ten.
Speaker 1 (01:45):
Ooh, you hear that Kelly's kids tenth birthday, you're getting
power tools.
Speaker 2 (01:49):
Oh no, that's only a couple months away from one
of them. I meant twenty twenty.
Speaker 1 (01:56):
Wow, that was pretty quick backpedaling right there. You know,
eventually they got to learn some useful skills, so arc
welding could be in their future.
Speaker 2 (02:04):
You know, she's really good with the screwdriver, and I
feel like I've done my part. She could 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.
Speaker 1 (02:20):
You're doing a bang up job for sure, and so
welcome to the podcast. Daniel and Joor 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,
(02:41):
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 idea is too bunkers for us to consider, because
our goal is to make sense of the whole universe.
My usual co host he can't be here today, but
I'm very happy to be joined by Kelly to talk
(03:02):
about today's amazing and fun topic.
Speaker 2 (03:05):
I'm excited to be here. You know how, I think
you and I just had a podcasting aniversary, 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.
Speaker 1 (03:18):
Oh no, I'm embarrassed. I haven't been keeping tracks. I'm
totally unaware of our anniversary. I apologize. I should have
gotten you something.
Speaker 2 (03:26):
Well, that's you got me a really interesting topic to
talk about. Oh, thank you.
Speaker 1 (03:30):
Yes, that must have been my subconscious plan of what's
what it was the whole time.
Speaker 2 (03:35):
Yes, the two year anniversary is the cold welding anniversary.
Speaker 1 (03:38):
M Well, congratulations on two years of being on the podcast.
We love all your contributions.
Speaker 2 (03:44):
Oh, I love being here.
Speaker 1 (03:45):
Thanks awesome. And sometimes on the podcast we talk about
quantum mechanics. Sometimes we talk about black hole, sometimes we
talk about planetary orbits in the future of our star.
And sometimes we talk about the everyday physics and science
that is around us, stuff that makes up our lives,
how it works, and how hard it is to understand
even the everyday normal stuff in our universe.
Speaker 2 (04:07):
It never gets easier.
Speaker 1 (04:09):
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 tuing and frowing of all those little
bits somehow weave themselves together into this incredible experience we
have where things seem solid or liquid or gaseous, that
(04:30):
we know that that actually all just bubbles up from
the tiny little particles inside them.
Speaker 2 (04:35):
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.
Speaker 1 (04:41):
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.
Speaker 2 (05:04):
You leave her alone. She's on the right track.
Speaker 1 (05:06):
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
(05:27):
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 ten to twenty nine 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
(05:49):
many for us to understand, which is why chemistry is
still a thing, right, which is a reason, the reason,
the reason we don't just have particle physics as the
only science in the universe.
Speaker 2 (06:00):
I mean, that would not be as interesting. But yeah,
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.
Speaker 1 (06:15):
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
(06:39):
all these different layers, which means there are fascinating questions
and interesting mysteries at every level 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.
Speaker 2 (06:56):
Not sure we'll ever understand people, but well we'll do
our best and keep.
Speaker 1 (07:00):
And 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 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
(07:22):
together to build stuff? How does the Eiffel Tower come
together from all those individual bits of steel?
Speaker 2 (07:28):
Gorilla glue?
Speaker 1 (07:32):
No, wow, you just invented an entire country over there.
Speaker 2 (07:38):
I mean, it's a really good glue. You can get
it in a can and spray it.
Speaker 1 (07:41):
Are you saying if they were going to build the
Eiffel Tower today, they would use guerrilla glue instead of welding.
Speaker 2 (07:47):
Probably, I don't know. You'll have to tell us about welding.
Then I'll make my decision at the end.
Speaker 1 (07:51):
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.
Speaker 2 (08:06):
Oh all right, you've got my attention. Maybe my oldest
can listen to the you know, second part of this discussion.
Speaker 1 (08:14):
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
(08:35):
stuff together without melting it down first, and could this
potentially be a way to build things in space?
Speaker 2 (08:43):
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 was it like sticking like pieces of gum together?
And then I'm like, no, welding, welding specifically refers to metal, right,
It's like putting two pieces of met together, is that right?
Speaker 1 (09:01):
Yeah?
Speaker 2 (09:02):
Yeah, yeah, And so then I was like, I don't know,
but but I hear it has to do with space,
So I'm gonna have to I'm gonna have to go
with that. So let's see if your listeners are more
clued into the world of welding than I am. I
bet they are, so.
Speaker 1 (09:16):
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 me
to questions at Danielandjorge dot 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.
Speaker 3 (09:39):
Well, cold welding can't work by heating up two 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.
Speaker 4 (09:53):
Maybe it is using a chemical reaction to fuse two
things together to rearrange them 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
(10:15):
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.
Speaker 2 (10:25):
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.
Speaker 1 (10:42):
I think that sounds like farm magic, you know. I
think he'd run into some magicians and they have some
like spells and powders, and they're able to like fuse
things together. I think we need to dig into this.
This could be like a whole revolution in science.
Speaker 2 (10:54):
So you hadn't heard of that before either.
Speaker 1 (10:56):
Vermont farmer magic. Noila had not heard of that before.
Speaker 2 (11:01):
I can imagine it being pretty obscure Vermont farmer magic.
But that's not that far away from the Salem witches.
Speaker 1 (11:10):
Those farmers. You gotta be careful. You gotta 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.
Speaker 2 (11:27):
You know, I have literally thousands of pages of notes,
and my mind retains one percent 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,
(11:47):
but it did not stay in my internal hard drive.
Speaker 1 (11:50):
Well maybe it turns out it won't be crucial for
a space settlement, after all, we'll find out.
Speaker 2 (11:56):
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.
Speaker 1 (12:12):
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
(12:33):
we corillatly stuff together in the modern world.
Speaker 2 (12:38):
So I'm doing a bathroom renovation and luckily when I
opened up the wall, there were no copper pipes, because
then I was gonna 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
(12:59):
the copper. That's metal too, right, So does that count?
Speaker 1 (13:03):
Yes, so that does not count as welding. Soldering 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. Soldering is different soldering. You have
a lower temperature filler, something which melts at a much
(13:26):
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 got two pipes you
want to stick together, you can solder them together. By
melting some filler material which sticks them together, or you
can actually weld them by melting the two pipes and
sticking them together when they're liquid, so when they cool,
(13:47):
you get those chemical bonds between them.
Speaker 2 (13:50):
But soldering is still cool because you get you used
a bload. I was kind of torn when I opened
up the walls and there was pets. Part of me
wanted to solder, part of me did, But anyway, okay,
I'm getting a soft track.
Speaker 1 (14:01):
And soldering somebody. You can do an electrical laborate. You
have that special solder material which you touch to the
tip of the soldering iron. It just like instantly liquifies, right,
super cool stuff, and that stuff you use because it
liquifies 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
(14:22):
materials and you do it by some combination usually of
heat and pressure.
Speaker 2 (14:27):
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.
Speaker 1 (14:39):
Yeah, welding technically is something we've been doing for thousands
of years. Essentially, blacksmiths 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 called that forge welding. Basically,
(15:03):
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.
Speaker 2 (15:11):
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.
Speaker 1 (15:22):
Yeah, exactly. And when my dad retired from Los Almo's
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
(15:44):
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.
Speaker 2 (15:57):
Whoa, that's awesome.
Speaker 1 (15:59):
It was pretty cool until half the town burnt 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, reasonable, yep.
Speaker 2 (16:18):
But said, hey, do you know what turneski?
Speaker 1 (16:21):
I don't. Who's that?
Speaker 2 (16:22):
I think he's the current blacksmith that loaves Alabos and
he's a friend of mine. Oh, right, back and off, okay, okay,
So I was trying to get you to talk about electricity.
Speaker 1 (16:31):
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 nineteenth
century we invented arc welding. We had electricity now, and
(16:52):
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 I 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
at the spot that between them that's touching.
Speaker 2 (17:09):
So what is more dangerous a giant furnace operating at
intense heat or electrifying metals and working with fads. Kid
one is not allowed to listen to the episode up
to this point yet, let's see where we get to.
Speaker 1 (17:24):
But our 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
(17:46):
a resistorance. It's gonna 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.
Speaker 2 (17:54):
Ah, And so we just don't let it get out
of control because you don't want your light bulbs burning
or melting.
Speaker 1 (18:01):
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. You can be DC, you can be acy,
all sorts of varieties of it. It was meant that
(18:23):
in the eighteen hundreds when people were learning about the
power of electricity.
Speaker 2 (18:27):
You know, you've got me wondering now, fun tangent. So
the first the first space walk ever conducted by a
woman was a sptlanasub Atskaya, and she welded in the
vacuum of space for the first time. So do you
think that she welded with heat or electricity?
Speaker 1 (18:47):
I suspect that was an arc welding, right, because the
heat generation from like a blowtorch might require combustion with
the atmosphere respect that was probably arc welding.
Speaker 2 (18:57):
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.
Speaker 1 (19:04):
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.
Speaker 2 (19:15):
Well, you know what's infuriating she is this like hypercompetent,
incredible cosmonaut. And there's this movie called Solute seven that
came out in Russia and it's sort of like Solute
seven is almost their equivalent to our Apollo thirteen. So
Solute seven like they had a problem I think it
was with the solar panels and the power ran down,
(19:36):
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
Setlanasovitskaya 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.
(19:57):
It's 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
(20:18):
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 Salute seven 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
(20:42):
a huge and at the very end you've got the
Space Shuttle driving past Salute 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, Like all.
Speaker 1 (21:00):
The research you did for your space settlement book may
have ruined you for science fiction Kelly.
Speaker 2 (21:05):
Ah, yeah, yeah, that's probably true.
Speaker 1 (21:09):
That's the downside of knowing a bunch of stuff.
Speaker 2 (21:11):
Better not to know.
Speaker 1 (21:14):
So in the eighteen hundreds we developed this new technique
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 nineteen
hundreds 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,
(21:37):
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.
Speaker 2 (21:56):
So depressing. Same goes for rockets, right, that's the rockets
took us to the Moon. We're used to drop bombs
on London without great aim, I'd say, But anyway, Yeah, it's.
Speaker 1 (22:06):
A conflict I feel deeply internally. I mean a lot
of advances in physics come from wanting to build weapons
of mass destruction, and so that's you know, also where
a lot of fund incomes 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 could apply a lot of these welding techniques
not just to metals. You can also weld things like glass. Right,
(22:30):
you can take two pieces of glass and you can
have a glass rod, and you can use a blowtorch
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 steal all sorts of stuff.
So welding is not just something you have to do
with metals.
Speaker 2 (22:47):
I didn't realize that. I guess I did think welding
was metal specific.
Speaker 1 (22:51):
Yeah, it's basically just joining stuff together by melting them.
And it makes a lot of sense because you melt
it together and that the atoms are all jiggling and
they can and jiggle together and when they cool, it's
like they're one again. What sort of mysterious is doing
this without heat? And so cold welding is a much stranger,
much more interesting and maybe potentially useful in space kind
(23:14):
of process.
Speaker 2 (23:15):
And we're going to learn more about it after the break.
All right, So, hot welding uses heat to combine metal, glass, plastic,
(23:35):
and steal. 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.
Speaker 1 (23:52):
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 very clean. Think about what's
happening inside of 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.
(24:13):
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.
Speaker 3 (24:34):
Right.
Speaker 1 (24:34):
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 the sort of
idea behind cold welding. Like, if you have a material
that's very regular and you have two pieces of it,
if you just get them together close enough and apply
(24:55):
a little bit of pressure, they will all of a
sudden act like they were always one thing. They will
just sort of like stick together.
Speaker 2 (25:02):
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 or yeah, why so why does that?
Why does that happen?
Speaker 1 (25:21):
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 Feinman. 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
(25:43):
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 are and stuck together.
(26:04):
It's thee 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.
Speaker 2 (26:14):
So why do metals do this? And like the I've
got a book sitting next to me with lots of pages,
but the pages are staying distinct. Why why doesn't everything
start just sort of blending together.
Speaker 1 (26:30):
Exactly? Why isn't the whole world just fuse the one
lump right exactly? Yes, this is something metals can do
because the electrons in a metal are very mobile. 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
(26:52):
can really flow freely through the metal. 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 one p orbital and the four f orbital,
and there's all these energy levels for an electron.
Speaker 2 (27:12):
We shouldn't assume I remember anything from high school chemistry,
but keep going.
Speaker 1 (27:16):
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 zigging back and forth between those two atoms. Well,
the energy levels get more complicated because you're now responding
(27:37):
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 jump up to the
higher energy levels and then move around the whole atom.
(27:58):
In insulators is like a big gap, then 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 are 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
(28:20):
share electrons, and boom, they're bonded.
Speaker 2 (28:23):
So all right, So I've got these copper pipes m
in a different part of my house, and and if
you get this electron c and these metals can all
like come together. Why do my copper pipes retain their shape?
Why doesn't the like copper you know that's above or
that's at the top of the pipe sort of like
(28:44):
start moving into the copper that's at the bottom of
the pipe, and it all just sort of like becomes
a glob.
Speaker 1 (28:51):
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 where the nibs and the holes all match up,
they will click in the place. The real question is,
(29:12):
like you've touched copper together before, you didn't notice it,
like cold welding together. Right. 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. And so why doesn't this
happen all the time. The answer is that these materials
(29:33):
have to be really really clean. Essentially, you need like
really bare copper to touch really bare copper, or bar
iron to touch bear 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.
(29:53):
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 sides and greases and all
sorts of other stuff on the surface, So you're not
really getting that clean contact.
Speaker 4 (30:06):
Is it?
Speaker 2 (30:07):
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.
Speaker 1 (30:16):
Yeah, a lot of the stuff we interact with are alloys, right,
steel for example, there's 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
(30:37):
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.
Speaker 2 (30:47):
So like if I rub my copper pipes, I know
I'm stuck on the copper pipes. I rubbed the copper
pipes together to clean them off and press them together.
Is that going to be enough or know where we
back to. Your copper pipes are probably not pure copper.
Speaker 1 (31:01):
It depends on the purity of your copper. But this
is something you can actually accomplish like down here on
Earth without special materials. It was first demonstrated in the
mid seventeen hundreds by a guy in England who just
took two lead balls and he pressed them together and
twisted them and rubbed them together and the two pieces
would join. This seemed like magic at the time. It's
(31:22):
like without any heat, he's somehow turning two lead balls
into one single thing of lead.
Speaker 2 (31:28):
Did they burn him at the state.
Speaker 1 (31:31):
Him and all the Vermont farmers, Yeah, exactly. This was
in the or mid seventeen hundred, so seventeen twenty four
by a guy named Reverend Dsagular I'm not sure if
he's actually French, and it's like Disagulae, but he demonstrated
this phenomenon to the Royal Society and published the details
in a scientific journal at the time. So this is
(31:54):
something you can accomplish with pretty normal materials, and then
archaeologists discover the humans have 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 seven
(32:17):
hundred BC.
Speaker 2 (32:18):
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
(32:39):
did it purposefully?
Speaker 4 (32:41):
Oh? Yeah?
Speaker 2 (32:41):
Or how do we know they didn't use hot welding.
Speaker 1 (32:44):
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
(33:06):
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.
Speaker 2 (33:24):
Oh, happy accident.
Speaker 1 (33:26):
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 they 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
(33:47):
and you make copper crystal over there. They're gonna 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 gonna 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.
Speaker 2 (34:07):
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, Yes, all the time.
Are there examples of it happening when it's not when
it wasn't intended to happen.
Speaker 1 (34:22):
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's 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
(34:45):
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
(35:05):
of space.
Speaker 2 (35:06):
All right, Well, before we get to welding in space
space space, let's take a commercial break. Okay, we're back,
(35:27):
all right, So you promised me stories about cold welding
happening when we didn't want it to happen. But you
told me that I had to wait till 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.
Speaker 1 (35:48):
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 cop or whatever, it's gonna
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
(36:10):
in the middle there to interfear, no impurities, Your bare
stuff stays bear stuff.
Speaker 2 (36:15):
Have we used that to our advantage yet? Like, do
we are there things that we decide we're just gonna
put together in space because we're gonna send clean stuff
up there and then assemble it with cold welding while
it gets up there.
Speaker 1 (36:26):
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 sort 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
(36:48):
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.
Speaker 2 (37:02):
Yeah, space sucks.
Speaker 1 (37:03):
Space sucks exactly. I did find a couple of examples
of accidental space welding go on. In nineteen sixty five,
Gemini four was the first American spacewalk. So they sent
the guy out there, They open the hatch. He goes
out there, he space walks 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
(37:24):
having so much fun. And when he came back in
and 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.
Speaker 2 (37:40):
No, no, you know. Apparently apparently the same thing happened
during the first Soviet space walk. Are you familiar with
this story?
Speaker 1 (37:46):
No, what happened.
Speaker 2 (37:47):
It doesn't have to do with cold welding. But Alexei
Leonov went out to do the first space walk 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. 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
(38:09):
like puffed up a little bit because you know, you
pressurize your suit, and after it got a little like puffy.
Or 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.
Speaker 1 (38:26):
Who 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 one of the initial
suggestions was cold welding. That maybe, 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
(38:49):
to your car and stuff, because everything's covered, right, this
pint 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 gonna worry about them like spot welding themselves together?
Oh my god, 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
(39:10):
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.
Speaker 2 (39:24):
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 gonna keep messing with us?
Speaker 1 (39:36):
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.
Speaker 2 (39:48):
Wait, NASA, there were delays in a NASA project.
Speaker 1 (39:50):
I know, shocking, right, And the spacecraft was like moved
across the country multiple times, and during those transports, 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
(40:13):
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.
Speaker 4 (40:23):
No.
Speaker 2 (40:24):
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. They did they find a way around it,
or were they just stuck.
Speaker 1 (40:34):
They never got the high gain intended 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
(40:54):
of those slow modems rather than your high speed internet.
Speaker 2 (40:58):
Yeah, but still, oh my goodness, those 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 gonna get my images eventually.
Speaker 3 (41:09):
I know.
Speaker 1 (41:10):
It's like the old days when you're down the neck
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? I download the right picture or not
a worry?
Speaker 2 (41:19):
And you go do my computer freeze or should I
shut it down? Or should do I wait? Yeah?
Speaker 1 (41:24):
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 gonna 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.
Speaker 2 (41:41):
Space, all right, So are there any other applications that
we should chat about.
Speaker 1 (41:46):
People have discovered that cold welling can also be really
helpful for nano circuits, Like you want to build really
really small electronics in 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, you know exactly, you know, they can count
(42:09):
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 nanofabrication. I read this paper that came out of
(42:31):
nature like ten years ago where they had ultra thin
gold nano wires 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
(42:51):
of like the electrical conductivity and a crystal orientation, and
it's as if it was always just one wire. So
this means, Kelly, do need your children, with like their
delicate little fingers to do tiny little arc welding on
our nano circuits?
Speaker 2 (43:06):
Oh? Good, good, because that was gonna be a thing.
Speaker 1 (43:10):
But it might be that we can send your kids
down the space to do space construction jobs without arc welding. Right,
how do you.
Speaker 2 (43:16):
Feel about that any of the episode? Nope, none of
the episode. None.
Speaker 1 (43:21):
If your kids grow up and they want to work
construction in space, you're gonna say no, yes, no. You
didn't think about that deeply at all. It was just
like a straight up no.
Speaker 2 (43:32):
I hope they don't go that route, but if they do,
I will support them grudgingly.
Speaker 1 (43:38):
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
the 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
(43:59):
one metal. Every time there's an advancement in material science,
it feels almost like we're creating real magic.
Speaker 2 (44:06):
I agree, but I still feel like the main takeaway
for me is one more thing to worry about in
space because cold welding going wrong. We should have gotten
that in the book.
Speaker 1 (44:17):
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 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
(44:38):
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 this incredible variety of behaviors and phenomena.
Speaker 2 (44:56):
Yeah, I gotta give it to you chemistries pretty much.
Speaker 1 (44:58):
It is kind of magic, dang it. Yeah.
Speaker 2 (45:02):
Yeah, my chemistry professors kept telling me that, but but
now I believe it.
Speaker 1 (45:09):
Finally, thirty years later, I've learned it too.
Speaker 2 (45:13):
Thirty Oh, why you might be on it?
Speaker 1 (45:17):
All right? Well, thanks Kelly for joining us on this
tour of chemistry and magic and this dive into how
cold welding works.
Speaker 2 (45:24):
Thanks for having me.
Speaker 1 (45:25):
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 two questions at
Danielandhorge dot com. Tune in next time. Thanks very much.
(45:49):
For more science and curiosity, come find us on social media,
where we answer questions and post videos. We're on Twitter, Discord, Instant,
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,
(46:09):
or wherever you listen to your favorite shows.
Hey, Kelly, how are things going on the science farm?
Speaker 2 (00:11):
You know, they're going pretty well, but we have some
old pipes and they've been sailing and so, you know,
renovating the bathroom in the kitchen. We're pretty low on
why to do list, but suddenly they went to the
top and so there's been lots of renovating projects happening.
Speaker 1 (00:26):
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.
Speaker 2 (00:34):
Uh, 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.
Speaker 1 (00:45):
Tools, not until they hear this episode and then they
start asking for their turn.
Speaker 2 (00:50):
This is why my kids don't get to listen to
your podcast.
Speaker 1 (00:52):
Man, how can you consider yourself a good parent if
you don't share this podcast with them.
Speaker 2 (00:58):
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 just seem to be tied to them not
listening to your podcast.
Speaker 1 (01:10):
Fair point. Hi, I'm Daniel, I'm a particle physicist and
a professor at UC Irvine, and I want everybody's kids
(01:31):
to stay happy and healthy.
Speaker 2 (01:33):
I'm Kelly Wieder 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 ten.
Speaker 1 (01:45):
Ooh, you hear that Kelly's kids tenth birthday, you're getting
power tools.
Speaker 2 (01:49):
Oh no, that's only a couple months away from one
of them. I meant twenty twenty.
Speaker 1 (01:56):
Wow, that was pretty quick backpedaling right there. You know,
eventually they got to learn some useful skills, so arc
welding could be in their future.
Speaker 2 (02:04):
You know, she's really good with the screwdriver, and I
feel like I've done my part. She could 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.
Speaker 1 (02:20):
You're doing a bang up job for sure, and so
welcome to the podcast. Daniel and Joor 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,
(02:41):
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 idea is too bunkers for us to consider, because
our goal is to make sense of the whole universe.
My usual co host he can't be here today, but
I'm very happy to be joined by Kelly to talk
(03:02):
about today's amazing and fun topic.
Speaker 2 (03:05):
I'm excited to be here. You know how, I think
you and I just had a podcasting aniversary, 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.
Speaker 1 (03:18):
Oh no, I'm embarrassed. I haven't been keeping tracks. I'm
totally unaware of our anniversary. I apologize. I should have
gotten you something.
Speaker 2 (03:26):
Well, that's you got me a really interesting topic to
talk about. Oh, thank you.
Speaker 1 (03:30):
Yes, that must have been my subconscious plan of what's
what it was the whole time.
Speaker 2 (03:35):
Yes, the two year anniversary is the cold welding anniversary.
Speaker 1 (03:38):
M Well, congratulations on two years of being on the podcast.
We love all your contributions.
Speaker 2 (03:44):
Oh, I love being here.
Speaker 1 (03:45):
Thanks awesome. And sometimes on the podcast we talk about
quantum mechanics. Sometimes we talk about black hole, sometimes we
talk about planetary orbits in the future of our star.
And sometimes we talk about the everyday physics and science
that is around us, stuff that makes up our lives,
how it works, and how hard it is to understand
even the everyday normal stuff in our universe.
Speaker 2 (04:07):
It never gets easier.
Speaker 1 (04:09):
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 tuing and frowing of all those little
bits somehow weave themselves together into this incredible experience we
have where things seem solid or liquid or gaseous, that
(04:30):
we know that that actually all just bubbles up from
the tiny little particles inside them.
Speaker 2 (04:35):
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.
Speaker 1 (04:41):
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.
Speaker 2 (05:04):
You leave her alone. She's on the right track.
Speaker 1 (05:06):
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
(05:27):
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 ten to twenty nine 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
(05:49):
many for us to understand, which is why chemistry is
still a thing, right, which is a reason, the reason,
the reason we don't just have particle physics as the
only science in the universe.
Speaker 2 (06:00):
I mean, that would not be as interesting. But yeah,
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.
Speaker 1 (06:15):
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
(06:39):
all these different layers, which means there are fascinating questions
and interesting mysteries at every level 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.
Speaker 2 (06:56):
Not sure we'll ever understand people, but well we'll do
our best and keep.
Speaker 1 (07:00):
And 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 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
(07:22):
together to build stuff? How does the Eiffel Tower come
together from all those individual bits of steel?
Speaker 2 (07:28):
Gorilla glue?
Speaker 1 (07:32):
No, wow, you just invented an entire country over there.
Speaker 2 (07:38):
I mean, it's a really good glue. You can get
it in a can and spray it.
Speaker 1 (07:41):
Are you saying if they were going to build the
Eiffel Tower today, they would use guerrilla glue instead of welding.
Speaker 2 (07:47):
Probably, I don't know. You'll have to tell us about welding.
Then I'll make my decision at the end.
Speaker 1 (07:51):
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.
Speaker 2 (08:06):
Oh all right, you've got my attention. Maybe my oldest
can listen to the you know, second part of this discussion.
Speaker 1 (08:14):
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
(08:35):
stuff together without melting it down first, and could this
potentially be a way to build things in space?
Speaker 2 (08:43):
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 was it like sticking like pieces of gum together?
And then I'm like, no, welding, welding specifically refers to metal, right,
It's like putting two pieces of met together, is that right?
Speaker 1 (09:01):
Yeah?
Speaker 2 (09:02):
Yeah, yeah, And so then I was like, I don't know,
but but I hear it has to do with space,
So I'm gonna have to I'm gonna have to go
with that. So let's see if your listeners are more
clued into the world of welding than I am. I
bet they are, so.
Speaker 1 (09:16):
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 me
to questions at Danielandjorge dot 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.
Speaker 3 (09:39):
Well, cold welding can't work by heating up two 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.
Speaker 4 (09:53):
Maybe it is using a chemical reaction to fuse two
things together to rearrange them 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
(10:15):
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.
Speaker 2 (10:25):
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.
Speaker 1 (10:42):
I think that sounds like farm magic, you know. I
think he'd run into some magicians and they have some
like spells and powders, and they're able to like fuse
things together. I think we need to dig into this.
This could be like a whole revolution in science.
Speaker 2 (10:54):
So you hadn't heard of that before either.
Speaker 1 (10:56):
Vermont farmer magic. Noila had not heard of that before.
Speaker 2 (11:01):
I can imagine it being pretty obscure Vermont farmer magic.
But that's not that far away from the Salem witches.
Speaker 1 (11:10):
Those farmers. You gotta be careful. You gotta 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.
Speaker 2 (11:27):
You know, I have literally thousands of pages of notes,
and my mind retains one percent 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,
(11:47):
but it did not stay in my internal hard drive.
Speaker 1 (11:50):
Well maybe it turns out it won't be crucial for
a space settlement, after all, we'll find out.
Speaker 2 (11:56):
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.
Speaker 1 (12:12):
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
(12:33):
we corillatly stuff together in the modern world.
Speaker 2 (12:38):
So I'm doing a bathroom renovation and luckily when I
opened up the wall, there were no copper pipes, because
then I was gonna 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
(12:59):
the copper. That's metal too, right, So does that count?
Speaker 1 (13:03):
Yes, so that does not count as welding. Soldering 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. Soldering is different soldering. You have
a lower temperature filler, something which melts at a much
(13:26):
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 got two pipes you
want to stick together, you can solder them together. By
melting some filler material which sticks them together, or you
can actually weld them by melting the two pipes and
sticking them together when they're liquid, so when they cool,
(13:47):
you get those chemical bonds between them.
Speaker 2 (13:50):
But soldering is still cool because you get you used
a bload. I was kind of torn when I opened
up the walls and there was pets. Part of me
wanted to solder, part of me did, But anyway, okay,
I'm getting a soft track.
Speaker 1 (14:01):
And soldering somebody. You can do an electrical laborate. You
have that special solder material which you touch to the
tip of the soldering iron. It just like instantly liquifies, right,
super cool stuff, and that stuff you use because it
liquifies 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
(14:22):
materials and you do it by some combination usually of
heat and pressure.
Speaker 2 (14:27):
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.
Speaker 1 (14:39):
Yeah, welding technically is something we've been doing for thousands
of years. Essentially, blacksmiths 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 called that forge welding. Basically,
(15:03):
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.
Speaker 2 (15:11):
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.
Speaker 1 (15:22):
Yeah, exactly. And when my dad retired from Los Almo's
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
(15:44):
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.
Speaker 2 (15:57):
Whoa, that's awesome.
Speaker 1 (15:59):
It was pretty cool until half the town burnt 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, reasonable, yep.
Speaker 2 (16:18):
But said, hey, do you know what turneski?
Speaker 1 (16:21):
I don't. Who's that?
Speaker 2 (16:22):
I think he's the current blacksmith that loaves Alabos and
he's a friend of mine. Oh, right, back and off, okay, okay,
So I was trying to get you to talk about electricity.
Speaker 1 (16:31):
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 nineteenth
century we invented arc welding. We had electricity now, and
(16:52):
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 I 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
at the spot that between them that's touching.
Speaker 2 (17:09):
So what is more dangerous a giant furnace operating at
intense heat or electrifying metals and working with fads. Kid
one is not allowed to listen to the episode up
to this point yet, let's see where we get to.
Speaker 1 (17:24):
But our 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
(17:46):
a resistorance. It's gonna 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.
Speaker 2 (17:54):
Ah, And so we just don't let it get out
of control because you don't want your light bulbs burning
or melting.
Speaker 1 (18:01):
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. You can be DC, you can be acy,
all sorts of varieties of it. It was meant that
(18:23):
in the eighteen hundreds when people were learning about the
power of electricity.
Speaker 2 (18:27):
You know, you've got me wondering now, fun tangent. So
the first the first space walk ever conducted by a
woman was a sptlanasub Atskaya, and she welded in the
vacuum of space for the first time. So do you
think that she welded with heat or electricity?
Speaker 1 (18:47):
I suspect that was an arc welding, right, because the
heat generation from like a blowtorch might require combustion with
the atmosphere respect that was probably arc welding.
Speaker 2 (18:57):
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.
Speaker 1 (19:04):
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.
Speaker 2 (19:15):
Well, you know what's infuriating she is this like hypercompetent,
incredible cosmonaut. And there's this movie called Solute seven that
came out in Russia and it's sort of like Solute
seven is almost their equivalent to our Apollo thirteen. So
Solute seven like they had a problem I think it
was with the solar panels and the power ran down,
(19:36):
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
Setlanasovitskaya 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.
(19:57):
It's 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
(20:18):
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 Salute seven 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
(20:42):
a huge and at the very end you've got the
Space Shuttle driving past Salute 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, Like all.
Speaker 1 (21:00):
The research you did for your space settlement book may
have ruined you for science fiction Kelly.
Speaker 2 (21:05):
Ah, yeah, yeah, that's probably true.
Speaker 1 (21:09):
That's the downside of knowing a bunch of stuff.
Speaker 2 (21:11):
Better not to know.
Speaker 1 (21:14):
So in the eighteen hundreds we developed this new technique
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 nineteen
hundreds 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,
(21:37):
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.
Speaker 2 (21:56):
So depressing. Same goes for rockets, right, that's the rockets
took us to the Moon. We're used to drop bombs
on London without great aim, I'd say, But anyway, Yeah, it's.
Speaker 1 (22:06):
A conflict I feel deeply internally. I mean a lot
of advances in physics come from wanting to build weapons
of mass destruction, and so that's you know, also where
a lot of fund incomes 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 could apply a lot of these welding techniques
not just to metals. You can also weld things like glass. Right,
(22:30):
you can take two pieces of glass and you can
have a glass rod, and you can use a blowtorch
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 steal all sorts of stuff.
So welding is not just something you have to do
with metals.
Speaker 2 (22:47):
I didn't realize that. I guess I did think welding
was metal specific.
Speaker 1 (22:51):
Yeah, it's basically just joining stuff together by melting them.
And it makes a lot of sense because you melt
it together and that the atoms are all jiggling and
they can and jiggle together and when they cool, it's
like they're one again. What sort of mysterious is doing
this without heat? And so cold welding is a much stranger,
much more interesting and maybe potentially useful in space kind
(23:14):
of process.
Speaker 2 (23:15):
And we're going to learn more about it after the break.
All right, So, hot welding uses heat to combine metal, glass, plastic,
(23:35):
and steal. 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.
Speaker 1 (23:52):
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 very clean. Think about what's
happening inside of 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.
(24:13):
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.
Speaker 3 (24:34):
Right.
Speaker 1 (24:34):
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 the sort of
idea behind cold welding. Like, if you have a material
that's very regular and you have two pieces of it,
if you just get them together close enough and apply
(24:55):
a little bit of pressure, they will all of a
sudden act like they were always one thing. They will
just sort of like stick together.
Speaker 2 (25:02):
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 or yeah, why so why does that?
Why does that happen?
Speaker 1 (25:21):
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 Feinman. 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
(25:43):
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 are and stuck together.
(26:04):
It's thee 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.
Speaker 2 (26:14):
So why do metals do this? And like the I've
got a book sitting next to me with lots of pages,
but the pages are staying distinct. Why why doesn't everything
start just sort of blending together.
Speaker 1 (26:30):
Exactly? Why isn't the whole world just fuse the one
lump right exactly? Yes, this is something metals can do
because the electrons in a metal are very mobile. 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
(26:52):
can really flow freely through the metal. 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 one p orbital and the four f orbital,
and there's all these energy levels for an electron.
Speaker 2 (27:12):
We shouldn't assume I remember anything from high school chemistry,
but keep going.
Speaker 1 (27:16):
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 zigging back and forth between those two atoms. Well,
the energy levels get more complicated because you're now responding
(27:37):
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 jump up to the
higher energy levels and then move around the whole atom.
(27:58):
In insulators is like a big gap, then 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 are 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
(28:20):
share electrons, and boom, they're bonded.
Speaker 2 (28:23):
So all right, So I've got these copper pipes m
in a different part of my house, and and if
you get this electron c and these metals can all
like come together. Why do my copper pipes retain their shape?
Why doesn't the like copper you know that's above or
that's at the top of the pipe sort of like
(28:44):
start moving into the copper that's at the bottom of
the pipe, and it all just sort of like becomes
a glob.
Speaker 1 (28:51):
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 where the nibs and the holes all match up,
they will click in the place. The real question is,
(29:12):
like you've touched copper together before, you didn't notice it,
like cold welding together. Right. 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. And so why doesn't this
happen all the time. The answer is that these materials
(29:33):
have to be really really clean. Essentially, you need like
really bare copper to touch really bare copper, or bar
iron to touch bear 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.
(29:53):
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 sides and greases and all
sorts of other stuff on the surface, So you're not
really getting that clean contact.
Speaker 4 (30:06):
Is it?
Speaker 2 (30:07):
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.
Speaker 1 (30:16):
Yeah, a lot of the stuff we interact with are alloys, right,
steel for example, there's 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
(30:37):
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.
Speaker 2 (30:47):
So like if I rub my copper pipes, I know
I'm stuck on the copper pipes. I rubbed the copper
pipes together to clean them off and press them together.
Is that going to be enough or know where we
back to. Your copper pipes are probably not pure copper.
Speaker 1 (31:01):
It depends on the purity of your copper. But this
is something you can actually accomplish like down here on
Earth without special materials. It was first demonstrated in the
mid seventeen hundreds by a guy in England who just
took two lead balls and he pressed them together and
twisted them and rubbed them together and the two pieces
would join. This seemed like magic at the time. It's
(31:22):
like without any heat, he's somehow turning two lead balls
into one single thing of lead.
Speaker 2 (31:28):
Did they burn him at the state.
Speaker 1 (31:31):
Him and all the Vermont farmers, Yeah, exactly. This was
in the or mid seventeen hundred, so seventeen twenty four
by a guy named Reverend Dsagular I'm not sure if
he's actually French, and it's like Disagulae, but he demonstrated
this phenomenon to the Royal Society and published the details
in a scientific journal at the time. So this is
(31:54):
something you can accomplish with pretty normal materials, and then
archaeologists discover the humans have 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 seven
(32:17):
hundred BC.
Speaker 2 (32:18):
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
(32:39):
did it purposefully?
Speaker 4 (32:41):
Oh? Yeah?
Speaker 2 (32:41):
Or how do we know they didn't use hot welding.
Speaker 1 (32:44):
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
(33:06):
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.
Speaker 2 (33:24):
Oh, happy accident.
Speaker 1 (33:26):
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 they 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
(33:47):
and you make copper crystal over there. They're gonna 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 gonna 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.
Speaker 2 (34:07):
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, Yes, all the time.
Are there examples of it happening when it's not when
it wasn't intended to happen.
Speaker 1 (34:22):
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's 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
(34:45):
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
(35:05):
of space.
Speaker 2 (35:06):
All right, Well, before we get to welding in space
space space, let's take a commercial break. Okay, we're back,
(35:27):
all right, So you promised me stories about cold welding
happening when we didn't want it to happen. But you
told me that I had to wait till 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.
Speaker 1 (35:48):
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 cop or whatever, it's gonna
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
(36:10):
in the middle there to interfear, no impurities, Your bare
stuff stays bear stuff.
Speaker 2 (36:15):
Have we used that to our advantage yet? Like, do
we are there things that we decide we're just gonna
put together in space because we're gonna send clean stuff
up there and then assemble it with cold welding while
it gets up there.
Speaker 1 (36:26):
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 sort 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
(36:48):
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.
Speaker 2 (37:02):
Yeah, space sucks.
Speaker 1 (37:03):
Space sucks exactly. I did find a couple of examples
of accidental space welding go on. In nineteen sixty five,
Gemini four was the first American spacewalk. So they sent
the guy out there, They open the hatch. He goes
out there, he space walks 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
(37:24):
having so much fun. And when he came back in
and 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.
Speaker 2 (37:40):
No, no, you know. Apparently apparently the same thing happened
during the first Soviet space walk. Are you familiar with
this story?
Speaker 1 (37:46):
No, what happened.
Speaker 2 (37:47):
It doesn't have to do with cold welding. But Alexei
Leonov went out to do the first space walk 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. 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
(38:09):
like puffed up a little bit because you know, you
pressurize your suit, and after it got a little like puffy.
Or 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.
Speaker 1 (38:26):
Who 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 one of the initial
suggestions was cold welding. That maybe, 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
(38:49):
to your car and stuff, because everything's covered, right, this
pint 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 gonna worry about them like spot welding themselves together?
Oh my god, 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
(39:10):
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.
Speaker 2 (39:24):
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 gonna keep messing with us?
Speaker 1 (39:36):
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.
Speaker 2 (39:48):
Wait, NASA, there were delays in a NASA project.
Speaker 1 (39:50):
I know, shocking, right, And the spacecraft was like moved
across the country multiple times, and during those transports, 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
(40:13):
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.
Speaker 4 (40:23):
No.
Speaker 2 (40:24):
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. They did they find a way around it,
or were they just stuck.
Speaker 1 (40:34):
They never got the high gain intended 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
(40:54):
of those slow modems rather than your high speed internet.
Speaker 2 (40:58):
Yeah, but still, oh my goodness, those 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 gonna get my images eventually.
Speaker 3 (41:09):
I know.
Speaker 1 (41:10):
It's like the old days when you're down the neck
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? I download the right picture or not
a worry?
Speaker 2 (41:19):
And you go do my computer freeze or should I
shut it down? Or should do I wait? Yeah?
Speaker 1 (41:24):
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 gonna 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.
Speaker 2 (41:41):
Space, all right, So are there any other applications that
we should chat about.
Speaker 1 (41:46):
People have discovered that cold welling can also be really
helpful for nano circuits, Like you want to build really
really small electronics in 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, you know exactly, you know, they can count
(42:09):
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 nanofabrication. I read this paper that came out of
(42:31):
nature like ten years ago where they had ultra thin
gold nano wires 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
(42:51):
of like the electrical conductivity and a crystal orientation, and
it's as if it was always just one wire. So
this means, Kelly, do need your children, with like their
delicate little fingers to do tiny little arc welding on
our nano circuits?
Speaker 2 (43:06):
Oh? Good, good, because that was gonna be a thing.
Speaker 1 (43:10):
But it might be that we can send your kids
down the space to do space construction jobs without arc welding. Right,
how do you.
Speaker 2 (43:16):
Feel about that any of the episode? Nope, none of
the episode. None.
Speaker 1 (43:21):
If your kids grow up and they want to work
construction in space, you're gonna say no, yes, no. You
didn't think about that deeply at all. It was just
like a straight up no.
Speaker 2 (43:32):
I hope they don't go that route, but if they do,
I will support them grudgingly.
Speaker 1 (43:38):
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
the 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
(43:59):
one metal. Every time there's an advancement in material science,
it feels almost like we're creating real magic.
Speaker 2 (44:06):
I agree, but I still feel like the main takeaway
for me is one more thing to worry about in
space because cold welding going wrong. We should have gotten
that in the book.
Speaker 1 (44:17):
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 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
(44:38):
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 this incredible variety of behaviors and phenomena.
Speaker 2 (44:56):
Yeah, I gotta give it to you chemistries pretty much.
Speaker 1 (44:58):
It is kind of magic, dang it. Yeah.
Speaker 2 (45:02):
Yeah, my chemistry professors kept telling me that, but but
now I believe it.
Speaker 1 (45:09):
Finally, thirty years later, I've learned it too.
Speaker 2 (45:13):
Thirty Oh, why you might be on it?
Speaker 1 (45:17):
All right? Well, thanks Kelly for joining us on this
tour of chemistry and magic and this dive into how
cold welding works.
Speaker 2 (45:24):
Thanks for having me.
Speaker 1 (45:25):
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 two questions at
Danielandhorge dot com. Tune in next time. Thanks very much.
(45:49):
For more science and curiosity, come find us on social media,
where we answer questions and post videos. We're on Twitter, Discord, Instant,
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,
(46:09):
or wherever you listen to your favorite shows.
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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