Speaker 1: When you save that picture of your cute dog or
Speaker 1: cat on your computer, you expect it to be there
Speaker 1: later when you want to show it off or send
Speaker 1: it to your favorite podcaster. Side note, Thanks for all
Speaker 1: the pet pictures. We love them and keep them coming.
Speaker 1: But how can you be sure that the information you
Speaker 1: store in your computer will be there uncorrupted when you
Speaker 1: come back for it? Is our digital information infrastructure robust
Speaker 1: or fragile. Since this is a physics podcast, you might
Speaker 1: be wondering if there are physics reasons that your data
Speaker 1: might not be safe. There are in this case. Unfortunately,
Speaker 1: it's not aliens. I'd love if it were aliens. But
Speaker 1: the concern is radiation from space. We know that it
Speaker 1: can hurt our bodies and rewrite our DNA, which are
Speaker 1: essentially biological hard drives. Can it also erupt our computers
Speaker 1: cosmic ray bitflips? What does that mean for data centers
Speaker 1: in space or puppies in space or pictures of cats
Speaker 1: on Mars? Oh my? Welcome to Daniel and Kelly's Extraordinary
Speaker 1: Digital Universe.
Speaker 2: Hello. I'm Kelly water Smith. I study parasites and space,
Speaker 2: and if something goes wrong with my computer, I have
Speaker 2: no clue how to deal with it.
Speaker 1: Hi, I'm Daniel. I'm a particle physicist and I'm technically
Speaker 1: an experimental list but really all of my sciences on
Speaker 1: the computer.
Speaker 2: Now, you told me that you were thinking about going
Speaker 2: into computer science before you decided to go into particle physics.
Speaker 2: So are you the person that everyone goes to when
Speaker 2: they have computer problems or now in the era of
Speaker 2: like MacBooks, is it just like two hard for you
Speaker 2: to troubleshoot? Or yeah? Are you? Are you the go
Speaker 2: to person?
Speaker 1: I'm definitely the tech support person in my family. You know,
Speaker 1: why won't this thing load? Or I want to print
Speaker 1: from here? Why can't I? For some reason, everybody comes
Speaker 1: to me, even though like computer science undergraduate degrees is
Speaker 1: mostly about like red black trees and sorting and whatever,
Speaker 1: and you don't really get expertise in that kind of stuff.
Speaker 1: Nothing useful, nothing useful exactly. But you have very recently
Speaker 1: become aware of how fragile computers are.
Speaker 2: Sure, Yes, I'm coming to you from Zex's chromebook because
Speaker 2: I have with in one year, broken my computer screen
Speaker 2: for the second time and it is in the shop again.
Speaker 1: And have you managed to blame this on like weird
Speaker 1: particles from space.
Speaker 2: No, no, what, just a lot of clumsy members in
Speaker 2: the Wienersmith household. Fifty percent of the time it was
Speaker 2: my fault. The other fifty percent was my adorable children.
Speaker 1: Well, maybe today's episode is going to give somebody over
Speaker 1: there excuse I didn't break that computer screen, even if
Speaker 1: my footprint is on it. It was cosmic rays.
Speaker 2: In this case, it was their teeth marks. But yes,
Speaker 2: maybe maybe they can blame a really amazing combination of
Speaker 2: particle rays that came in just the right pattern.
Speaker 1: Well, today's topic really connects with a few of my
Speaker 1: interests because, of course I like thinking about cosmic rays.
Speaker 1: They are particles from space, and everything I do is
Speaker 1: on the computer. Plus, this is a concept that appears
Speaker 1: a lot in popular science, cosmic rays flipping bits on computers,
Speaker 1: And I thought, let's make sure everybody out there really
Speaker 1: understands how that works and how serious a problem it is,
Speaker 1: especially with all this talk of sending data centers into space.
Speaker 2: Does it occur a lot in pop science? I can't
Speaker 2: think of a single example.
Speaker 1: Wow, maybe I read the wrong pop science.
Speaker 2: Or maybe I read the wrong pop science. Can you
Speaker 2: name five examples? No? I'm just kidding. Name one. I'm
Speaker 2: winny h.
Speaker 1: You put me on the spot, and I cannot name
Speaker 1: a single one right now off the top of my head.
Speaker 1: But I have the feeling like this is something that
Speaker 1: I hear a lot in popular science, or that people
Speaker 1: in general know a little bit about, but my benefit
Speaker 1: from understanding, like the real physics that underlies all of
Speaker 1: this stuff, so that in the future, when there is
Speaker 1: an onslaught of popular science articles after we launched the
Speaker 1: first data centers into space, everyone will be well equipped.
Speaker 2: Well, but I mean, this is a thing that could
Speaker 2: be important for our lives personally, So like, not only
Speaker 2: could this be important if we put data centers in space,
Speaker 2: but for example, one of our listeners, Simon, sent us
Speaker 2: this article where there was a plane that was flying
Speaker 2: and all of a sudden it dropped really fast, and
Speaker 2: nobody died. Some people did get hurt. But the thought
Speaker 2: was that some part of the computer on the plane
Speaker 2: got hit by a cosmic ray. It flipped a bit,
Speaker 2: which Daniel's going to explain, and that sort of messed
Speaker 2: up the control of the plane and the plane dropped
Speaker 2: really quick and some people got hurt. And so this
Speaker 2: is like a thing that could impact our lives, and
Speaker 2: at some point I have another space related story that
Speaker 2: I'll tell. So you know, this isn't just a thing
Speaker 2: that might be important in the future. It's a thing
Speaker 2: that matters. Now.
Speaker 1: Hey, that sounds a lot to me like a popular
Speaker 1: science article about a cosmic ray.
Speaker 2: Bitflip, I thought you said a sci fi thing.
Speaker 1: Oh are you too popular? No play the tape, we said,
Speaker 1: POPSI this is a concept that appears a lot in
Speaker 1: popular science.
Speaker 2: Does it occur a lot in pop science?
Speaker 1: Pop science? Popular science? Pop science, popular science, popular science articles? Oh?
Speaker 2: I thought you said sci fi? All right? All right, anyway,
Speaker 2: Daniel and I aren't communicating well today, But that's all right.
Speaker 2: We're gonna move forward. I'll give you the win on
Speaker 2: that one, all right. So let's let's lay some groundwork here.
Speaker 1: But before we explain how everything works. I was wondering
Speaker 1: what people knew about how cosmic rays could mess up
Speaker 1: those pictures of your puppies. So I went out there
Speaker 1: to ask our volunteers their thoughts, without any googling, of course,
Speaker 1: whether cosmic rays can corrupt computers. Here's what people had
Speaker 1: to say.
Speaker 3: Perhaps theris magnetosphere is protecting us from that issue.
Speaker 1: Cosmic rays are nasty.
Speaker 3: Of course, Cosmic rays can corrupt computer data. Cosmic rays
Speaker 3: definitely can flip bits in computer systems.
Speaker 1: I'm sure cosmic rays can cause problems or another. I
Speaker 1: can with some dish drawers. I'm not sure.
Speaker 3: Cosmic rays can absolutely corrupt computer data by flipping essential bits,
Speaker 3: even when we build in redundancy. I think there have
Speaker 3: even been stories of car accidents attributed to cosmic ray disruptions.
Speaker 1: I would think so because the higher frequency spectrum could
Speaker 1: penetrate I wouldn't imagine across the computer barriers.
Speaker 3: Cosmic rays and computers do not get along. I think
Speaker 3: cosmic rays messing with our computers all the time, and
Speaker 3: that's why we have checksums and stuff. Yes, I know
Speaker 3: for certain in space, electronics that are exposed to cosmic
Speaker 3: rays do have a risk of that bits getting flipped.
Speaker 1: Absolutely, cosmic rays can corrupt data. Satellites can be corrupted
Speaker 1: by cosmic rays, so they have to be hardened and redundant.
Speaker 1: I'm not sure about on the surface of the Earth, though,
Speaker 1: a cosmic ray flipped a bit inside the game as
Speaker 1: the player was playing and basically cheated for them. They
Speaker 1: would be able to alter the bit in a data stream.
Speaker 2: So yes, great answers. As always, I think when someone
Speaker 2: says can X mess up y, my answer is usually yeah,
Speaker 2: probably as like I'm negative. But I don't think I
Speaker 2: really knew that this was something to worry about until
Speaker 2: I was researching a city on Mars and we came
Speaker 2: across some stories about like space radiation messing up computers.
Speaker 1: Yeah. People think of their computers as robust, like you
Speaker 1: put a one in memory somewhere, it's going to be there.
Speaker 1: It's not like somethuzz if you a paper that can
Speaker 1: get overwritten or destroyed or whatever. But in reality, these
Speaker 1: are physical systems and they live in the universe, and
Speaker 1: the universe is not always a friendly place to store
Speaker 1: to your data.
Speaker 2: Yeah, and you're not supposed to bite the screen either.
Speaker 2: So let's start with understanding how computers store data because
Speaker 2: I still find this like slightly magical, which which is
Speaker 2: kind of great. So how are computers storing information?
Speaker 1: Yeah, it's a great question, and fundamentally computer store information
Speaker 1: using quantum mechanics. Right, you could store information on just
Speaker 1: like a long tape, like the way a Turing machine does.
Speaker 1: You're like writing ones and zeros and principle, it can
Speaker 1: be anything, but you want it to be compact, so
Speaker 1: you could have like lots and lots of ones and
Speaker 1: zeros and not have it take up a whole room.
Speaker 1: And you want it to be fast so you can
Speaker 1: read it out really quickly and you're not waiting an
Speaker 1: hour for that picture of your puppies to load. And
Speaker 1: so we make it small and fast by using atomic systems.
Speaker 1: And at its core, all these atomic systems are built
Speaker 1: on semiconductors, which is why you hear about silicon so much.
Speaker 1: Silicon is a semiconductor. Well, what does that mean semiconductors, Well,
Speaker 1: semiconductors sit between insulators which don't conduct electricity and conductors
Speaker 1: like metals, which conduct a lot of electricity. And understand
Speaker 1: why that is. You have to understand something about the
Speaker 1: atomic structure here, and we're used to thinking about atoms
Speaker 1: by themselves. You have like energy levels, and a silicon
Speaker 1: atom has like where electrons can be. There's like a
Speaker 1: ladder of them, right, and they can absorb and emit photons.
Speaker 1: This kind of stuff is like a very discrete set
Speaker 1: of energy levels, and that's true for atoms. And if
Speaker 1: you have, like a gas of silicon, it's going to
Speaker 1: emit photons at certain energy levels and absorb at those
Speaker 1: energy levels, and that's all cool. So that's atomic physics.
Speaker 2: Is atomic physics another word for chemistry, because it kind
Speaker 2: of sounds like it's another word for chemistry.
Speaker 1: It's the foundation of all chemistry. Yet everything in chemistry
Speaker 1: comes out of those energy levels. And then it gets
Speaker 1: more complicated because you have atoms binding with each other
Speaker 1: and sharing electrons. And if you take that too, you
Speaker 1: get things like solids where you have a whole lattice
Speaker 1: of atoms, and now you don't have to solve these
Speaker 1: problems just for one electron. You have to think about
Speaker 1: what happens to an electron that's shared among many, many atoms.
Speaker 1: And so instead of thinking about a lattice of silicon,
Speaker 1: atoms is like each a bunch of individual atoms with
Speaker 1: their own energy levels. These things overlap because they're so close,
Speaker 1: and so they spread these sharp atomic energy levels into bands.
Speaker 1: So we talked about bands of electron energy levels. So
Speaker 1: you shouldn't think about electron in a piece of silicon
Speaker 1: is like this one belongs to that atom, or belongs
Speaker 1: to this atom, or belongs to this other atom. It
Speaker 1: moves smoothly right the ions the nuclei are bound together,
Speaker 1: they're sort of like fixed in a lattice, and the
Speaker 1: electrons are all moving around, and there's different energy levels there,
Speaker 1: which roughly get grouped into two different kinds of bands.
Speaker 1: There's the valence bands. Those are the low energy ones
Speaker 1: where the electrons are mostly local and bound to a
Speaker 1: specific ion. But then there's above that, there's the conduction band,
Speaker 1: are usually empty and the electrons can flow around. So
Speaker 1: if you have, for example, a metal, then there's a
Speaker 1: very small gap between the valiance band and the conduction band,
Speaker 1: and the electrons that fill up the valance band can
Speaker 1: jump up to the conduction band like getting on the
Speaker 1: highway really easily, and flowing all around the metal. So
Speaker 1: if you put an electric field near a conductor, the
Speaker 1: electrons will jump up to the conduction band and flow
Speaker 1: all around. If you have a big gap there, like
Speaker 1: no entrances to your freeway, then the electrons are all
Speaker 1: stuck in their local area, and even if you put
Speaker 1: an electric field over it, they're really not going to move.
Speaker 1: So that's how to understand an insulator and a conductor
Speaker 1: or something we call a metal. Usually a semiconductor like silicon,
Speaker 1: is something where that gap is sort of like in between.
Speaker 1: It's not really big, it's not really small. All that
Speaker 1: silicon lithography helps you do some fancy local chemistry to
Speaker 1: make a silicon dioxide or silicon nitride that changes its conductivity,
Speaker 1: which means you can now separate components and dielectrics and
Speaker 1: whatever you need to build circuits. And so you can
Speaker 1: design really really small electrical circuits just by doping the
Speaker 1: silicon in various ways.
Speaker 2: Okay, so the reason you want to use silicon is
Speaker 2: because it's helpful to have something that's in between, because
Speaker 2: you well, so, like, why wouldn't you just want to
Speaker 2: have a full insulator or a full conductor on your
Speaker 2: chip as opposed to just using silicon everywhere and then
Speaker 2: tinkering with it. Tinkering sounds possibly more complicated than just
Speaker 2: putting conductors in some places.
Speaker 1: Yeah, you could construct it out of just conductors wrapped
Speaker 1: in insulators, and that's basically how you build circuits on
Speaker 1: your bench, Right, you have like copper wires wrapped in rubber, right,
Speaker 1: and that works, But it's really hard to do that
Speaker 1: at a micro scale. To manufacture that stuff, and to
Speaker 1: do it cheaply and at high volume. It's easier to
Speaker 1: take silicon, which can be tweaked in either direction. It
Speaker 1: turns out to be a lot easier to tweak it
Speaker 1: than to just like build it from scratch, okay.
Speaker 2: And so to tweak it, you just like flick some
Speaker 2: germanium on it, and now you're good.
Speaker 1: Yeah. Essentially we have a whole episode about how silicon
Speaker 1: lithography works, and people should dig into the details there.
Speaker 1: There's a lot of nuance that's missed in this summary here,
Speaker 1: but roughly, that's why you want to start with silicon,
Speaker 1: because you can easily change it to be a conductor
Speaker 1: or an insulator.
Speaker 2: I'll go check that out. My memory is just the
Speaker 2: pits lately, Okay. So now we've got our semiconductors.
Speaker 1: Yeah, and so you can use that to build all
Speaker 1: sorts of microscopic bits of your circuits out of silicon.
Speaker 1: But keep that in mind for later when we're talking
Speaker 1: about what happens when a cosmic ray tears through a
Speaker 1: piece of silicon. So, now you have the silicon, and
Speaker 1: then you want to build a computer, how do you
Speaker 1: actually use it to store memory? So your computer has
Speaker 1: several different kinds of memory depending on your need. So
Speaker 1: the memory you might think about are things like RAM. Right,
Speaker 1: These are like things your computer remembers when it's turned on,
Speaker 1: but if your turn off, the computer is empty. So
Speaker 1: like loading a program into memory so that your computer
Speaker 1: can run it. Right. So this is you know, random
Speaker 1: access memory, and these days it's called d RAM dynamic
Speaker 1: random access memory. And random access just means that you
Speaker 1: can like get a piece of informmation from anywhere. You
Speaker 1: don't have to like read it in order, like a book.
Speaker 1: You can just have an index. You can say, tell
Speaker 1: me what's stored here, tell me what's stored there. Song.
Speaker 1: As you know the index, you can look it up.
Speaker 2: Okay, So I've got a semiconductor which allows me to
Speaker 2: move electrons around.
Speaker 1: And to build circuits. And so now the question is
Speaker 1: how do you use little electrical circuits to store information?
Speaker 1: And so DRAM does this by using a capacitor connected
Speaker 1: to a transistor. So a capacitor physically, if you build
Speaker 1: a large one, is just like two surfaces insulated from
Speaker 1: each other that are separated, and so you can have
Speaker 1: like a charge stored across them. You can put a
Speaker 1: bunch of electrons on one side and then you have
Speaker 1: like a voltage across the capacitor. And so capacitor is
Speaker 1: very useful for all sorts of things circuits. But in
Speaker 1: this case you can just ask like, well, is there
Speaker 1: voltage on it? If so, I'm going to call that
Speaker 1: a one. If there's no voltage across it, I'm going
Speaker 1: to call that a zero. You just need some sort
Speaker 1: of microscopic state which you can control and you can
Speaker 1: read out, and then you assign the meaning of one
Speaker 1: to one of the states and zero to the other state.
Speaker 2: Okay, but so what could actually be happening in the
Speaker 2: capacitor is there's a lot of different ways that you
Speaker 2: could have more charge on one side and less charge
Speaker 2: on the other, but it all gets sort of summarized
Speaker 2: down to one in zero.
Speaker 1: Yeah, exactly, because this is digital logic. In the end,
Speaker 1: everything is analog, like the universe is mostly analog, but
Speaker 1: we assign digital meaning to it. And as these things
Speaker 1: get smaller and faster than the amount of charge to
Speaker 1: capacitor holds gets really really small, so that it's quick
Speaker 1: to read out, it's quick to assign, and it's easy
Speaker 1: to make small. So in this case, it's like a
Speaker 1: few tens of thousands of electrons hold the charge. And
Speaker 1: you can imagine more complicated systems. If you don't want
Speaker 1: to use binary logic, you want to use trinary, you
Speaker 1: could have like two different threashs. You could say zero
Speaker 1: is anywhere from zero to ten thousand electrons, and a
Speaker 1: one is ten thousand to twenty thousand electrons, and anything
Speaker 1: above twenty thousand I'm gonna call it two if you
Speaker 1: have trinary logic, but we use binary. So it's like
Speaker 1: zero or somewhere above ten thousand electrons or ten to
Speaker 1: thirty fempto coulums. And so there's a capacitor that holds
Speaker 1: it and then a transistor which allows you access to it.
Speaker 1: And so that's the basis of DRAM. And this requires
Speaker 1: constant power. When you turn off the computer, that charge
Speaker 1: dissipates and it's gone, which is why when you turn
Speaker 1: off your computer, it doesn't remember anymore what was in
Speaker 1: its memory.
Speaker 2: Okay, so you've got the semiconductor, and those electrons are
Speaker 2: jumping up into the highway and they're getting moved around
Speaker 2: in the capacitor so that they can store up these
Speaker 2: ones in these zeros.
Speaker 1: And it's critical there that you have conductors, Like the
Speaker 1: plates on the capacity are made of conductors and insulators
Speaker 1: between the plates so that the chargers don't just flow across.
Speaker 2: Okay, all right, so you want them to move and
Speaker 2: then you want them to stay once you've.
Speaker 1: Moved there, exactly, Okay, exactly, But these things don't work great.
Speaker 1: Like there's a leakage there because these things are super
Speaker 1: duper small and the insulator isn't perfect, and so every
Speaker 1: sixty four milliseconds or so, it just like leaks away.
Speaker 1: So your computer has to constantly refresh your RAM every
Speaker 1: sixty milliseconds or so, it rewrites the number onto it.
Speaker 1: It's not very stable.
Speaker 2: That doesn't sound like a great system. I mean, I
Speaker 2: mean it seems to work great. I love my computer
Speaker 2: when it's not in the shop.
Speaker 1: It's kind of amazing that it works as well as
Speaker 1: it does. You don't just like call up a picture
Speaker 1: and it's like totally corrupted.
Speaker 2: Yeah.
Speaker 1: Then there's another kind of memory, which is in your CPU.
Speaker 1: So your computer basically has like a hard drive to
Speaker 1: store information. And then there's the CPU, the central processing
Speaker 1: unit that does all the actual calculations. Then it has
Speaker 1: access to the main memory that we just talked about,
Speaker 1: the RAM, But when it's doing the calculations, it slurps
Speaker 1: stuff from the RAM into a special super fast memory
Speaker 1: called the CASH, which is close to the CPU so
Speaker 1: that it doesn't have to go all the way to
Speaker 1: memory which turns out to be a little bit slow.
Speaker 1: So you have these hierarchies of memory in your computer
Speaker 1: which are smaller and faster or bigger and slower. So
Speaker 1: SRAM is the fastest, smallest memory. It's like right there
Speaker 1: next to the CPU. It's like if you're trying to
Speaker 1: do your household budget, you don't keep all of the
Speaker 1: information right in front of you. You have like a
Speaker 1: sheet of paper or a spreadsheet with like the critical
Speaker 1: details right in front of you that you're calculating right now.
Speaker 1: The CPU's CASH is essentially like its.
Speaker 2: Little worksheet and sm SRAM stands for is that slow
Speaker 2: random access memory? Is that what it stands for.
Speaker 1: It stands for a static random access memory, okay, as
Speaker 1: opposed to dynamic, which is the kind you have for
Speaker 1: your most of your memory. And this is cool because
Speaker 1: it's built by a pair of logic gates usually, so
Speaker 1: it's built using not gates. Sont gits are something where
Speaker 1: if you take in a one, you output a zero,
Speaker 1: if you take in a zero, you output a one.
Speaker 1: So it's like a basic logic gate in the same
Speaker 1: categories like and gates you know that require two ones
Speaker 1: to output a one, or an ore gate that requires
Speaker 1: either of the inputs to be one to output a one.
Speaker 2: Oh yes, of course.
Speaker 1: And these again are built on top of transistors which
Speaker 1: are made of silicon, So you can tie a few
Speaker 1: transistors together to make a nand gate or an and
Speaker 1: gate or a knot gate. All these basic digital logics
Speaker 1: are built on top of the same fundamental technology, which
Speaker 1: are silicon transistors which have these various levels of doping
Speaker 1: so they can do what they need to do. And
Speaker 1: so the way SRAM works is you have two knock
Speaker 1: gates looped on each other. It's kind of silly, but
Speaker 1: it works really amazingly well. Like, say I have two
Speaker 1: knock gates. If the first one has an output value
Speaker 1: of one, and then you feed that into the second one,
Speaker 1: the second one is going to have an output value
Speaker 1: of zero, right, feed the output of the second one
Speaker 1: back into the first one, and it's going to keep
Speaker 1: the first one having an output value of one because
Speaker 1: it's input with zero. And so it's just sort of
Speaker 1: like if you have two of these things in series
Speaker 1: and then looped on each other, they support each other,
Speaker 1: and there's two stable states here. Either the first one
Speaker 1: is one and the second one is zero, or the
Speaker 1: first one is zero and the second one is one,
Speaker 1: and either way they just constantly support each other, confirming
Speaker 1: each other.
Speaker 2: Okay, I'm following, but I feel like the big picture
Speaker 2: here for anyone who is maybe having a little trouble following,
Speaker 2: is that in all of these cases, what's happening is
Speaker 2: we are very carefully keeping track of where electrons are going,
Speaker 2: and they need to be going in particular places and
Speaker 2: staying there.
Speaker 1: And so you have your DRAM, which is a capacity
Speaker 1: and a transistor. You have your s RAM, which has
Speaker 1: this pair of knock gates which you're keeping your information.
Speaker 1: And these are more robust than your DRAM because they
Speaker 1: don't leak the same way. But these transistors are super
Speaker 1: duper small and so like a little bit of tweaking
Speaker 1: can corrupt them. And then the last kind of memory
Speaker 1: in your computer is the hard drive. This is the
Speaker 1: most robust, the thing where if you turn it off,
Speaker 1: it will stay there. You can put your picture of
Speaker 1: your puppy on your hard drive and turn your computer
Speaker 1: off and on it's still there. And this is also
Speaker 1: the slowest kind of memory and the biggest and these
Speaker 1: days this uses flash technology, which essentially like an insulated
Speaker 1: box and you try to trap some electrons in there,
Speaker 1: or you let the electrons out, and it's insulated so
Speaker 1: the electrons can't leave. And essentially you say, if the
Speaker 1: electrons are trapped in there, then it's going to be
Speaker 1: a one. If the electrons are not trapped, it's going
Speaker 1: to be a zero. And so this is like a
Speaker 1: really big energy barrier that's very robust and it's very
Speaker 1: hard to pertur, but it's kind of slow, which is
Speaker 1: why you use it for your biggest, slowest memory, like
Speaker 1: your hard drives.
Speaker 2: Does your computer start with all the electrons that it
Speaker 2: needs and just move them around or does it pull
Speaker 2: electrons out of the environment when it needs them?
Speaker 1: Why are you Oh, great question? No, I love this
Speaker 1: question because it touches on like, you know, electrons versus electricity, right,
Speaker 1: and mostly electricity is the motion of electrons, So you're
Speaker 1: not like running out of electrons in a sense. But
Speaker 1: people confuse these two things and they like to talk
Speaker 1: about electrons when they mean electricity. And remember that these
Speaker 1: numbers of electrons are super due per tiny, right, Like
Speaker 1: the number of electrons in silicon is like, you know,
Speaker 1: ten to the twenty nine per gram or some crazy number.
Speaker 1: So if you're talking about circuits that need like ten
Speaker 1: thousand electrons, it's really just you're never going to run
Speaker 1: out of electrons. So electrons are everywhere. We're all just
Speaker 1: living in a vast ocean of electrons. It's about controlling
Speaker 1: where they are and where they aren't and where they go. Okay,
Speaker 1: you don't need to recharge your electrons, but it sounds
Speaker 1: to me like a really fun scam we can sell people,
Speaker 1: like let's top up your electrons.
Speaker 2: All right, Well, Daniel and I are going to think
Speaker 2: of how we can monetize electrons. See if you can
Speaker 2: hear are commercial for it during the break, and we'll
Speaker 2: be back in a moment. We're back. Daniel just gave
Speaker 2: us a great explanation for how computers store information, and
Speaker 2: now we're going to hear about how cosmic rays can
Speaker 2: mess that all up. So, Daniel, what is a cosmic ray.
Speaker 2: I'm sure physicists have this absolutely nailed down.
Speaker 1: Cosmic rays are basically just particles from space. Right. Rays
Speaker 1: is just like a generic name for a particle, or
Speaker 1: sort of an old fashioned name, and cosmic just means
Speaker 1: it comes from space somewhere, and the Earth is constantly
Speaker 1: being hit by particles from space. Because space is not empty.
Speaker 1: You might think of it as like a grand vacuum,
Speaker 1: but really it's filled with particles, just much lower density
Speaker 1: than here on Earth. So in our Solar system, for example,
Speaker 1: there's a massive producer of cosmic rays in the Sun.
Speaker 1: It pumps out protons and electrons and photons and all
Speaker 1: sorts of stuff, and when the protons and electrons hit
Speaker 1: the Earth, we consider those cosmic rays. And Jupiter also
Speaker 1: puts out a lot of radio contributes to cosmic rays.
Speaker 1: The center of our galaxy is a massive source of
Speaker 1: radiation because there's a lot of crazy stuff going on
Speaker 1: in there. It's hot, it's dense, it's nasty. Things around
Speaker 1: a black hole also emit cosmic rays because there's a
Speaker 1: lot of energy there. And so basically a lot of
Speaker 1: things in the universe are emitting cosmic rays and they
Speaker 1: go from fairly low energy all the way up to
Speaker 1: like the craziest highest energy things ever seen in the universe,
Speaker 1: which are what which are created by things we don't know. So,
Speaker 1: for example, the large hadron collide, which is like the
Speaker 1: pinnacle of energy the humanity's ever created. We accelerate things
Speaker 1: to have like thirteen terra electron bolts. That's thirteen trillion
Speaker 1: electron bolts of energy. But out in space we see
Speaker 1: things that have a million times as much energy. Whoa
Speaker 1: yeah wow, And we don't know what causes that. Like
Speaker 1: we know that the center of the galaxy emits some
Speaker 1: but not that high energy. We know supernovas creates some
Speaker 1: but not that high energy. We know if you take
Speaker 1: particles from supernovas whiz them around um black hole, that
Speaker 1: gives them a little bit more energy, but still not
Speaker 1: that high energy. So we see these particles from space
Speaker 1: that have crazy high energy, and nothing we know in
Speaker 1: the universe can make particles that high energy. It's like
Speaker 1: a huge mystery. Maybe it's a glitch in the simulation.
Speaker 1: Maybe it's alien particle physicists shooting their beams at us.
Speaker 1: Maybe there's information there we don't know.
Speaker 2: Okay, go ahead and mark that spot on your dKu
Speaker 2: Bingo cards. Friends, I knew that was coming.
Speaker 1: Aliens, Yeah, yep. And so they impact life on Earth
Speaker 1: here because they hit us, but they hit the atmosphere,
Speaker 1: and the atmosphere is a great shield from cosmic rays.
Speaker 1: But it doesn't just like delete them. What happens when
Speaker 1: a particle hits the top of the atmosphere is it
Speaker 1: collides into the particles in the atmosphere. And so you
Speaker 1: go from having one very energetic particle to two that
Speaker 1: have half as much energy, to four with a quarter
Speaker 1: as much energy, to a trillions of particles, each with
Speaker 1: a small slice of the energy, but still enough to
Speaker 1: make it all the way down to the star of
Speaker 1: the Earth. And so we have a constant flux of
Speaker 1: cosmic rays on the surface of the Earth. It's like
Speaker 1: one hundred and fifty muons per meter squared wow per
Speaker 1: second at sea level. So like every fingernail you have
Speaker 1: has hundreds of muons passing through it every second. They're everywhere.
Speaker 2: So you know what I'm wondering, do I need to
Speaker 2: worry about that?
Speaker 1: Well, it contributes to you know, changes in your DNA
Speaker 1: because cosmic grays carry energy and if they hit your DNA,
Speaker 1: they can change essentially the information stored there in great
Speaker 1: analogy to what happens when a cosmic gray hits a computer. Right,
Speaker 1: this is how biology stores information, but it's not totally robust.
Speaker 1: You know, I'm not an expert in biology, but my
Speaker 1: understanding is that cosmic ray can like either hit the
Speaker 1: DNA directly or it can ionize water, which makes free
Speaker 1: radicals that react with the DNA. And in the end
Speaker 1: you can have something which was originally like a cytosine
Speaker 1: and now behaves like thiamine, and that gets read out
Speaker 1: differently by your molecular machine. Now you're building a different
Speaker 1: protein and like, oops, now you have cancer, or oops,
Speaker 1: now you have like laser rays out of your eyeballs. Right,
Speaker 1: all sorts of mutations, And so I think this is
Speaker 1: a big part of our evolutionary history that cosmic creates
Speaker 1: contribute to changes in our DNA. At least, it's my
Speaker 1: favorite explanation for how me and Katrina have an athletic.
Speaker 2: Sun Wait, wait, when I got skin cancer, you mean
Speaker 2: I could have gotten lasers out of my eyes because
Speaker 2: that would have been way cooler. Anyway, sunscreen and broad
Speaker 2: rimmed hats are your friends friends.
Speaker 1: Yes, exactly. And in that case, I think mostly skin
Speaker 1: cancer is caused by ultraviolet radiation and not by like
Speaker 1: more deeply penetrating muons or neutrinos. But it's the same principle,
Speaker 1: you know, particles in that case, photons from space corrupting
Speaker 1: the information. And so think of these things as just
Speaker 1: high energy particles from space to come down through the atmosphere. Okay,
Speaker 1: so you have these particles from space that carry a
Speaker 1: lot of energy. Mostly it's muons. They're also electrons in there.
Speaker 1: They don't penetrate as deeply. Most the electrons are blocked
Speaker 1: by stuff like skin or you like a small sheet
Speaker 1: of metal. Muons have more mass and so they don't
Speaker 1: interact as much and so they can go deeper into
Speaker 1: an object. They are also neutrons. Neutrons are created in
Speaker 1: these showers, and because they're neutral, they pass through a
Speaker 1: lot of material. They're penetrating as well. Neutrons are less common.
Speaker 1: They're like one hundred times less dense than muons, but
Speaker 1: they have a lot more mass to them, so they
Speaker 1: can really do a lot more damage. So you have
Speaker 1: these particles from space, and we told you that we
Speaker 1: build all of our digital infrastructure out of semiconductors, which
Speaker 1: rely on like the delicate balance between a conductor and
Speaker 1: an insulator based on how exactly the electron bands are arranged,
Speaker 1: and essentially build everything out of these building blocks. Well,
Speaker 1: what happens when a cosmic ray passes through a lattice
Speaker 1: of silicon. It can smash right into one of those atoms,
Speaker 1: breaking up the nucleus, or it can push that atom,
Speaker 1: or it can just ionize a bunch of silicon. The
Speaker 1: silicon atoms that it kicked off can like flow through
Speaker 1: the lattice, ionizing it. And so essentially, if you build
Speaker 1: your whole digital infrastructure out of this stuff, it's like
Speaker 1: taking a sharpie and just like scrawling a ride across
Speaker 1: the page.
Speaker 2: Okay, so it's not like it's so I'm thinking about
Speaker 2: it as a highway now with cars moving along it,
Speaker 2: the cars being the electrons and the silicon being the highway.
Speaker 2: It's not that the cars are getting moved around. It's
Speaker 2: that you're essentially like blowing up the highway and now
Speaker 2: the cars like they don't know where to go anymore.
Speaker 1: Yeah, essentially you're blowing up the highway. And think about
Speaker 1: for example, your capacitor, right, your basic unit of memory
Speaker 1: in your computer. What's going to happen if you suddenly
Speaker 1: deposit a whole bunch of charge, or you like tear
Speaker 1: through that and destroy the insulator so the charge leaks out.
Speaker 1: You're going to go from a zero to a one,
Speaker 1: or you're going to go from a one to a zero. Right,
Speaker 1: You've built this careful thing out of these bricks and
Speaker 1: then you have to suddenly just tear right through it,
Speaker 1: and you still have the machinery around it that's going
Speaker 1: to try to interpret what's going on the one or
Speaker 1: a zero. Right, Your transistor that's next to the conductor
Speaker 1: is gonna be like, oh, excuse me, by the way,
Speaker 1: this doesn't seem to be like it's behaving itself. It's
Speaker 1: just gonna be like, is there charge zero? Is there
Speaker 1: no charge one?
Speaker 2: That sounds bad?
Speaker 1: Yeah, And the same is true for your s RAM
Speaker 1: for example. This was built out of knot gates, and
Speaker 1: these again are built out of transistors, and transistors have
Speaker 1: various components of silicon that are dope in various ways
Speaker 1: so they can do their logic. If you have a
Speaker 1: cosmic ray plow through that, it's going to deposit a
Speaker 1: bunch of charge. It's going to change the way those
Speaker 1: gates operate in the same way. Now, hard drives, which
Speaker 1: are the most robust and the most difficult to change,
Speaker 1: have that like insulated box. So this requires like stronger radiation.
Speaker 1: But essentially you want to have like charge in there
Speaker 1: or not charge in there. If you have a cosmic
Speaker 1: ray that comes in and tears through it and essentially
Speaker 1: deposits a bunch of charge, you're gonna go from a
Speaker 1: zero to a one. Or if it breaks the containment
Speaker 1: and lets the charge out, then you're gonna go from
Speaker 1: a one to a zero. So it's possible for every
Speaker 1: one of these components in your computer to be susceptible
Speaker 1: to cause and graze, very similar to how it happens
Speaker 1: with DNA.
Speaker 2: Okay, so that all sounds bad, but can we get
Speaker 2: a little bit more concrete about, Like does that mean
Speaker 2: your computer is just gonna like one hundred percent crash
Speaker 2: every time this happens, or like what's the range of
Speaker 2: outcomes here?
Speaker 1: So it depends on where it hits, right, it might
Speaker 1: hit your computer and it just hits a place where
Speaker 1: like nothing is being used anyway, Like you have an
Speaker 1: empty part of your hard drive and it goes from
Speaker 1: zero to one. Whatever it was noise, it doesn't really matter.
Speaker 1: Or maybe you were about to store a picture of
Speaker 1: your puppy there and so it goes from zero to
Speaker 1: one and then you overwrite your puppy on top of it,
Speaker 1: so it doesn't matter. Right, So those are the best
Speaker 1: case scenarios. You've overwritten your garbage with a puppy.
Speaker 2: Oh good, I thought you were gonna say, overrode my puppy,
Speaker 2: and I was gonna get really upset.
Speaker 1: No, that's a disaster.
Speaker 2: Yeah, meal is very cute.
Speaker 1: Yeah. So in the sort of next stage of like
Speaker 1: problematic thing, it's like something goes wrong and it's crucial
Speaker 1: and your computer crashes. You know, like your computer follows
Speaker 1: some instruction in its memory and the instruction isn't what
Speaker 1: it was supposed to be because it got changed by
Speaker 1: a cosmic ray and it does this instead of doing that,
Speaker 1: and it doesn't work and it gets stuck and boom,
Speaker 1: your computer has crashed. That's actually a good outcome because
Speaker 1: you notice it and it stops you from using it,
Speaker 1: and then you like restart your computer and you're.
Speaker 2: Fine, so your computer can recover.
Speaker 1: Yeah, if your computer crashes, you just reboot it, right,
Speaker 1: Like it happens all the time, especially if you use Windows.
Speaker 2: Oh ouch, but isn't your silicon chip still like toast
Speaker 2: because it got hit.
Speaker 1: No, No, you could just refresh. It's like it will
Speaker 1: change it from zero to one. But it's not like
Speaker 1: it's destroyed it, right, Okay. Usually these things, you know,
Speaker 1: are robust. It's about the charge that's stored in that circuit,
Speaker 1: and so they can like release it or right into
Speaker 1: it accidentally. But you restart all this stuff, You're gonna
Speaker 1: be fine. It's not permanent damage. If it happens occasionally.
Speaker 1: We'll talk later about what happens to electronics inside the
Speaker 1: large hadron lighter and why that needs to be much
Speaker 1: more radiation hard. But you know, if it happens once
Speaker 1: or twice, you're fine. You have like enough silicon there
Speaker 1: for these things to still work.
Speaker 2: Okay, So then what is a bad result.
Speaker 1: The bad result is when it happens silently, like you
Speaker 1: have stored some data on your computer and the bit
Speaker 1: gets flipped and you don't notice, and later you read
Speaker 1: that in you do some analysis and you're like maybe
Speaker 1: you're doing some science or you know, your puppy's eye
Speaker 1: color has changed or something. And this is when it's dangerous,
Speaker 1: when it's a silent mistake. Right. Or for example, you're
Speaker 1: storing voting results from some precinct in Virginia and like, oops,
Speaker 1: a bit flips and somebody now has more or fewer votes. Right,
Speaker 1: This is when we really rely on this stuff. So
Speaker 1: not knowing that it's happened and having it happen silently
Speaker 1: in a way that doesn't cause any errors, that's the
Speaker 1: worst case scenario.
Speaker 2: Okay, this is getting scary. How often does this happen?
Speaker 1: So there's bad news and then there's good news. Okay,
Speaker 1: So bad news is that it's not that rare, you know,
Speaker 1: because there are cosmic rays everywhere, So you should expect
Speaker 1: like a few bit flips per year per gigabyte of RAM, right,
Speaker 1: and I have like thirty gigabytes of RAM on my computer,
Speaker 1: and so I'm expecting like dozens of times a year
Speaker 1: a bit it's going to be flipped in my RAM.
Speaker 1: Oh yikes, exactly, And so that seems like an issue.
Speaker 1: But of course the nerds know this and they have
Speaker 1: built protection for us. And sound like we're just running
Speaker 1: out there totally exposed. If you have a computer in
Speaker 1: an environment where you absolutely need it to be robust,
Speaker 1: then there are clever systems to detect these errors and
Speaker 1: correct them.
Speaker 2: I find myself wondering, was there an era when we
Speaker 2: had computers but we didn't know this and there were
Speaker 2: like disasters because we didn't know this.
Speaker 1: Yeah. One of the ways this was originally discovered is
Speaker 1: that electronics near nuclear testing in the fifties had anomalies.
Speaker 1: People were like, whoa, what's going on with our electronics?
Speaker 1: And then they realized, of course that the radiation from
Speaker 1: the blast was interfering with the electronics. It was like
Speaker 1: in the seventies that the detailed physics involved was understood
Speaker 1: and like demonstrated in particle beams, and so it was
Speaker 1: really like in the eighties people understood what's going on here,
Speaker 1: and can we build protection?
Speaker 2: Oh wow? Okay, well I'm glad we've got protection now,
Speaker 2: all right, So tell me how the protection works, please.
Speaker 1: So the simplest and the most expensive way to protect
Speaker 1: your data is just to have copies of it, right, Like,
Speaker 1: if you have really sensitive data stored on a hard drive.
Speaker 1: Hard drives used to be much less stable. You could
Speaker 1: just like lose a drive, like the head dropped on it.
Speaker 1: Back when there were magnetic spinning discs, and so we
Speaker 1: had these things called like raidar rays where you just
Speaker 1: had like everything was stored in duplicate or in triplicate
Speaker 1: even and in triplicate is cool because if one of
Speaker 1: them gets corrupted, you have two other copies, and so
Speaker 1: you can vote. You're like, is this bit supposed to
Speaker 1: be a zero or a one? And if two of
Speaker 1: them agree, then you know, then that's the way you go.
Speaker 1: I think that's how like the flight systems work on
Speaker 1: the Space Shuttle, right, they all vote, the three independent
Speaker 1: systems or something like that, and they all vote, so
Speaker 1: the you always have two the degree. So that's the
Speaker 1: most complicated and expensive way. And that's quite expensive because
Speaker 1: now you're like tripling the cost of your memory. If
Speaker 1: you want to store a gigabyte, you really have to
Speaker 1: have three gigabytes of memory in there just to make
Speaker 1: it protected, Yanks. And so since that's so expensive, people
Speaker 1: came up with cheaper, faster, more clever ways, things like checksums. Right,
Speaker 1: Like if you send a message across the internet and
Speaker 1: you want to make sure the message arrived uncorrupted, then
Speaker 1: none of it got like garbled along the way. You
Speaker 1: can also send a checksum, which is like the output
Speaker 1: of a little calculation you do on the data. As
Speaker 1: simple way to think of a checksums to be like
Speaker 1: take the whole data set and treat it like a number.
Speaker 1: Was it even or odd? And that way, if I
Speaker 1: send you a message, and I also send you by
Speaker 1: the way it should have been even, then you can
Speaker 1: check to make sure it's even. That doesn't catch all
Speaker 1: possible errors, like if you flip two bits, for example,
Speaker 1: But it's one simple way to say, like were there
Speaker 1: any mistakes? So in modern computers they do something which
Speaker 1: is more sophisticated than just a simple like is it
Speaker 1: even or odd? They have these parody checkers that take
Speaker 1: like groups of four data words. A word is like
Speaker 1: a bunch of bits altogether. And you have parity bits
Speaker 1: which check how many events there are and how many
Speaker 1: odds there are. And if you overlap these things in
Speaker 1: a clever way, and you have this voting system, you
Speaker 1: can have like one parody bit checks three words and
Speaker 1: another parody bit checks three other words. And so through
Speaker 1: some clever algorithms and clever math, you can detect any
Speaker 1: bitflip in any of those words without having complete duplicates.
Speaker 1: So this is like ten percent of the data cost.
Speaker 1: You have a gigabyte of memory, you build a gigabyte
Speaker 1: plus ten percent, and you have enough data storage to
Speaker 1: detect if there were any bits flipped in your core gigabyte.
Speaker 2: But we didn't have this clever and cheap version during
Speaker 2: the Shuttle era, and that's why the Shuttle was so expensive.
Speaker 1: I don't know if the memory costs contributed a lot
Speaker 1: to the Shuttle. And many computer systems have this already.
Speaker 1: So for example, your hard drive very likely has error
Speaker 1: correction on it. Your RAM probably has error correction on it.
Speaker 1: CPU caches usually do not, because this is the s
Speaker 1: RAM stuff because it has to be super duper fast.
Speaker 1: It really will slow down your computer if you have
Speaker 1: error correction on that CPU, like the worksheet that the
Speaker 1: CPU is using. But if you have a really important computers,
Speaker 1: like you're operating a data center and you need to
Speaker 1: provide really robust calculations for your consumers, or you're running
Speaker 1: something in space, then you need to have error correction
Speaker 1: on your caches as well. Although I was reading that
Speaker 1: often in space applications they take consumer PCs and they
Speaker 1: just turn off the CPU cache because they'd rather be
Speaker 1: robust than fast, and so they're like, this part is
Speaker 1: not robust in space, so let's just turn it off.
Speaker 2: All right, Well, let's take a break, and when we
Speaker 2: get back, Kelly will tell a fun story about how
Speaker 2: galactic cosmic rays messed up computers in space. All right,
Speaker 2: we're back. We're on the International Space Station and an
Speaker 2: alarm has just gone off. Samantha Christafaretti, who's an Italian astronaut,
Speaker 2: was amazing at her ability to memorize all of the
Speaker 2: different alarms on the station. And even though this is
Speaker 2: the first time she's ever heard this alarm, she immediately
Speaker 2: knows what it is and she yells ammonia leak. And
Speaker 2: so she and Terry Vertz have memorized the protocol for
Speaker 2: ammonia leaks. And so what they do is they run
Speaker 2: over towards the Russian segment and they close the airlock
Speaker 2: for the American side. And so what happens if there's
Speaker 2: an ammonia leak is that the coolant system for keeping
Speaker 2: the American side of the International Space Station is leaking.
Speaker 2: So ammonia is toxic and so they can't stay over
Speaker 2: there anymore, So they close off their side so that
Speaker 2: the toxic stuff can't get out. Then they're supposed to
Speaker 2: get naked. Then they're supposed to go through to the
Speaker 2: Russian side, and then they're supposed to close the hatch
Speaker 2: and hope that the Russians have extra undies. And I
Speaker 2: saw Daniel look confused, and so, Daniel, are you wondering
Speaker 2: why they closed to the second hatch.
Speaker 1: Why did they close the second hatch, Kelly, just to.
Speaker 2: Make sure they didn't get any more moonia on the
Speaker 2: other side. But you're probably wondering actually why they were
Speaker 2: supposed to get naked.
Speaker 1: Right, yes, exactly. I was having fun imagining it though.
Speaker 2: Okay, well, they apparently were not having fun imagining what
Speaker 2: it would be like because they skipped that step. But
Speaker 2: they were supposed to take the clothes off because the
Speaker 2: concern was ammonia might stick to their clothes and they
Speaker 2: might end up bringing ammonia over to the Russian side.
Speaker 2: And the Russians use Glai call to cool their side
Speaker 2: of the International Space Station so they don't have this
Speaker 2: toxic stuff.
Speaker 1: So ammonia sticks to close but not to like skin.
Speaker 1: I mean it.
Speaker 2: Probably it could stick to everything, but the goal is
Speaker 2: to bring as little as possible over to the Russian side.
Speaker 1: Do you ever think the engineers are just like, let's
Speaker 1: add getting naked to this protocol and see if the
Speaker 1: astronauts will really do it.
Speaker 2: Yeah, well, so you know, you've got to imagine that
Speaker 2: at some point they were like, do I really want
Speaker 2: to see my middle aged colleague naked and zero gravity?
Speaker 2: And I think, and they must have both decided no,
Speaker 2: And so they went over to the Russian side fully dressed.
Speaker 2: They locked the second airlock, and then they got permission
Speaker 2: to go back, and so they go back, and the
Speaker 2: alarm goes off again, and they go through the whole
Speaker 2: process the second time, and yet again they decide to
Speaker 2: not take their clothes off. And I believe they ended
Speaker 2: up saying they decided to not take their clothes off
Speaker 2: because they couldn't smell ammonia. Ammonia has this like distinct
Speaker 2: rotten egg smell. And it turned out that they were right.
Speaker 2: It was a false alarm.
Speaker 1: Was this the universe trying to get them naked? Is
Speaker 1: that what was happening?
Speaker 2: It could be, could be, But the best guess that
Speaker 2: folks came up with afterwards for what happened is that
Speaker 2: galactic cosmic radiation had hit their computers and had inadvertently
Speaker 2: turned on the ammonia leak alarm, and there wasn't actually
Speaker 2: an ammonia leak. They never were able to find an
Speaker 2: ammonia leak, but it, you know, they started doing this
Speaker 2: emergency protocol and they had to eventually do it twice
Speaker 2: before they were able to fix their computers. Well, so
Speaker 2: we're sort of talking about these data centers today, and
Speaker 2: I guess one thing I want to point out is
Speaker 2: that even though the International Space Station is to a
Speaker 2: large extent protected by Earth's strong magnetosphere, which sends a
Speaker 2: lot of these charge particles, you know, to the poles
Speaker 2: and protects the International Space Station and the equipment and
Speaker 2: people within it, you still get hit sometimes, and so
Speaker 2: you still have to worry about the equipment. Where are
Speaker 2: people thinking of putting these data centers? Are they within
Speaker 2: the protection of the magnetic field or out past it?
Speaker 1: I don't think they want to go very far because
Speaker 1: the further you go, the harder it is to access
Speaker 1: and to repair. And I'm not on record is thinking
Speaker 1: that any of this is a good idea, and you know,
Speaker 1: the cooling is are the radiation is tricky because you
Speaker 1: don't have the benefit of the Earth's sphere, even if
Speaker 1: you still have some of the magnetosphere. And so I
Speaker 1: think it's a crazy idea pushed by tech bros who
Speaker 1: think it's gonna be fun and sci fi. And you know,
Speaker 1: I don't know about that. We'll have a whole another
Speaker 1: episode digging into the economics of data centers in space.
Speaker 1: But yeah, out there in space there is more radiation,
Speaker 1: and so you need more protection and you need like
Speaker 1: shielding for these things, or you need to make extra
Speaker 1: error correction, or you need to use technologies that are
Speaker 1: more radiation hard it actually on Earth. Sometimes I'm frustrated
Speaker 1: by the amount of error correction. There are scenarios where
Speaker 1: it would be better for physics, even if it's worse
Speaker 1: for computers and for Amazon or whatever, to have less
Speaker 1: error correction. Because all of these things are evidence of
Speaker 1: cosmic rays. And if you're curious about cosmic rays, where
Speaker 1: do they hit, what's going on? Then one of the
Speaker 1: biggest challenge is seeing them. The really high energy cosmic
Speaker 1: grays are really rare. It's like one per square kilometer
Speaker 1: per century, either in a lot of square kilometers or
Speaker 1: a lot of centuries. And these massive data centers that
Speaker 1: are being built out are basically huge cosmic ray detectors.
Speaker 1: And imagine if you could use all of Google and
Speaker 1: Amazon's data centers to observe cosmic rays from space. It
Speaker 1: would be incredible, right. I actually looked into this and
Speaker 1: connected with folks at Google to see if we could
Speaker 1: use it. But their air correction is so good they
Speaker 1: don't even store it. They don't log it, and be like,
Speaker 1: by the way, we flipped a bit here and we
Speaker 1: corrected it, They just correct it and move on.
Speaker 2: How hard would it be for them to collect that data?
Speaker 1: Oh? Man, it would require a change in pretty low
Speaker 1: level operating system stuff, unfortunately. And you know, for a
Speaker 1: while they were going to be willing to share the
Speaker 1: data with us if it was like something they already had,
Speaker 1: they could just ship to us and we could analyze it.
Speaker 1: And that was so excited. But then it turns out
Speaker 1: it's not storage and getting them to do anything just
Speaker 1: for fundamental physics is frustratingly difficult.
Speaker 2: Google. I thought you were trying to not be evil
Speaker 2: or did they like do away with that a long
Speaker 2: time ago.
Speaker 1: Yeah, I don't know. I mean, it's not their obligation
Speaker 1: to fund basic research. But it's frustrating to me because
Speaker 1: it means that these cosmic grays are there and they're
Speaker 1: actually observed by our technology, and then that information is
Speaker 1: just thrown away. You know, one person's error is another
Speaker 1: person's gold maybe Nobel Prize gold. Right, So that's frustrating.
Speaker 1: But there are other times when we think cosmic grays
Speaker 1: could have affected things on Earth. The voting example I
Speaker 1: mentioned earlier was not a hypothetical. There was an election
Speaker 1: in two thousand and three in Brussels where one candidate
Speaker 1: had a number of votes that was suspiciously off by
Speaker 1: four ninety six. They're like, that's a weird number, Like,
Speaker 1: how did this number just appear in the computers? It's
Speaker 1: off by this specific power of two, right, fenty ninety
Speaker 1: six is the power of two, So it could be
Speaker 1: caused by a single bitflip. And you know they went
Speaker 1: through and nobody tinkered with it. There's no evidence that
Speaker 1: anybody like infected it or hacked it, or there was
Speaker 1: a copyer or anything. They think probably was a bitflip
Speaker 1: that caused this weird result in an election in Brussels,
Speaker 1: and so it's certainly happened, right, It's something we need
Speaker 1: to be aware of. I mean we need to know about.
Speaker 2: Did it change the results of the election?
Speaker 1: No, they figured out I think they knew how many
Speaker 1: votes have been cast in total, and so they knew
Speaker 1: that there was an excess and affected it. And I
Speaker 1: don't think it flipped the answer either way. So it's
Speaker 1: just sort of weird and mixed people suspicious, and you know,
Speaker 1: it highlights something else, which is that our whole digital
Speaker 1: infrastructure is sensitive to what's going on in space. We
Speaker 1: recently had a really nice cosmic light show because there
Speaker 1: was an extra amount of solar radiation which led to
Speaker 1: northern lights all over the place on Earth. But that's
Speaker 1: extra solar radiation and that can come at any time.
Speaker 1: In the eighteen fifties, there was a really spectacular coronal
Speaker 1: mass ejection, an eruption of charged particles from the Sun
Speaker 1: which basically like a huge loop of plasma which heads
Speaker 1: towards the Earth, which is just high energy cosmic rayse
Speaker 1: that's what plasma is, right, and it can be like
Speaker 1: billions of tons of materials. Most of these things missed
Speaker 1: the Earth because they're it's pretty small and far from
Speaker 1: the sun, but when it washes over the Earth, it
Speaker 1: can devastate our digital infrastructure more than just like corrupting
Speaker 1: a single bit on an airplane or in a voting machine.
Speaker 1: This in the eighteen fifties, like set telegraph networks on fire,
Speaker 1: like you know, sparks were flying. Yeah, it's crazy. And
Speaker 1: if that happened today, like our digital infrastructure is not
Speaker 1: protected from that kind of incursion, you wouldn't be able
Speaker 1: to like shop for stuff online for days and days
Speaker 1: while people fixed it.
Speaker 2: I mean, can you imagine, like if something took out
Speaker 2: all of our satellites, how absolutely pned we would be Yeah,
Speaker 2: like nope, credit cards, I wouldn't have starlink Internet, there'd
Speaker 2: be no dKu anymore everyone.
Speaker 1: Can you imagine dot civilization crumbles?
Speaker 3: Yes?
Speaker 2: Right, yep, I agree.
Speaker 1: And so in particle physics, we've thought about this a
Speaker 1: lot because we're operating computers in a very high radiation
Speaker 1: environment constantly, like we're creating that radiation. When you smash
Speaker 1: two particles together, you generate huge numbers of protons and
Speaker 1: neutrons and muons and all kinds of stuff, And then
Speaker 1: we have silicon near the collision in order to measure
Speaker 1: these things to detect these particles in exactly that way.
Speaker 1: But if you run it for a while, eventually your
Speaker 1: silicon gets trashed, you know, so every few years we
Speaker 1: have to pull the thing out and send in new
Speaker 1: silicon basically, And so people are doing stuff like exploring
Speaker 1: whether we can use diamond instead. You know, we talk
Speaker 1: about silicon as a semiconductor, but it's not the only
Speaker 1: semi conductor out there. You can build these chips out
Speaker 1: of diamond, which makes them more radiation hard which is
Speaker 1: very expensive because there isn't a huge consumer diamond lithography
Speaker 1: industry the way there is for silicon. So particle physics
Speaker 1: tends to make its advances by like piggybacking on huge
Speaker 1: trillion dollar consumer trends, and that hasn't happened for particle
Speaker 1: physics that we don't have, you know, diamond chips yet,
Speaker 1: but it's something that people are looking at that we
Speaker 1: might have to do in the future in order to
Speaker 1: protect our computers from cosmic grades or radiation more generally.
Speaker 2: Can we take a us step back to like so
Speaker 2: if we'd had another Carrington event type of thing, happen.
Speaker 2: Is there something we could have done to protect all
Speaker 2: of our satellites from an event like that? Like, should
Speaker 2: we be encasing all of our satellites in diamonds? Is
Speaker 2: what I'm asking.
Speaker 1: It would make them so glittery and beautiful, that's right. Well,
Speaker 1: essentially what you need is mass, Like either you should
Speaker 1: build the chips themselves out of diamond to make them
Speaker 1: radiation hard or is you just shield them, in which
Speaker 1: case you need mass, and mass, as you know, is
Speaker 1: expensive to put in space, and that's why it's so
Speaker 1: difficult to have things like computing in space because it
Speaker 1: needs the thing which is expensive to put. So I
Speaker 1: think it would look awesome, but I don't think we
Speaker 1: should bling up all of our satellites.
Speaker 2: Okay, So for the foreseeable future, we're probably not going
Speaker 2: to do anything about the fact that if we had
Speaker 2: a Carrington event type of thing happen again, we would
Speaker 2: be in a lot of trouble.
Speaker 1: Yeah, that would be a massive investment in infrastructure, and
Speaker 1: I don't see anybody doing it, though I think it
Speaker 1: would be a good idea. But until then, we do
Speaker 1: need to be aware that cosmic rays are everywhere. They
Speaker 1: are streaming through your room right now, and they are
Speaker 1: streaming through your computer. And sometimes they can flip a
Speaker 1: bit a zero to one. They can plow their way
Speaker 1: through a bunch of silicon and change the way those
Speaker 1: delicate electronics work. Most of the time this doesn't affect
Speaker 1: your computer, or it does it in an obvious way, or
Speaker 1: it's caught by error correction and fixed. But sometimes it isn't.
Speaker 1: And so next time your computer goes hey wire, you
Speaker 1: could blame it on your kids, or you could blame
Speaker 1: it on particles from space.
Speaker 2: Or the next time you get that super awesome science result,
Speaker 2: you should question yourself even more. That anxiety should keep
Speaker 2: you up all night, because maybe it was a cosmic
Speaker 2: ray and you were wrong.
Speaker 1: Maybe when you counted parasites you're off by one. All right, Well,
Speaker 1: thanks for taking this cosmic journey with us into how
Speaker 1: silicon electronics work and how they are vulnerable to particles
Speaker 1: from space. As always, we are grateful for your shared curiosity.
Speaker 2: Thanks everyone, have a good one. Daniel and Kelly's Extraordinary
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