How was radioactive decay discovered? What are the different kinds of decay? How does quantum mechanics make all this happen? I discuss these questions and more in today’s Ask a Spaceman!

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Hosted by Paul M. Sutter, astrophysicist and the one and only Agent to the Stars (http://www.pmsutter.com).

 

EPISODE TRANSCRIPTION (AUTO-GENERATED)

Pulling up to Mickey D's just for drinks. Oh yeah, that's me. Nothing extra. Just perfection and a straw coming in hot for the coldest cups on the block because there are drinks, then there are drinks from mcdonald's, get a creamy Oreo fr or mccaf smoothie for less with 20% off any purchase of $10 or more. Only on the app, limited time only at participating mcdonald's valid one time per day visit mcdonald's app for details. Late 18 hundreds, x-rays were all the rage rightly. So because x-rays are awesome, everyone was going bananas for it trying to understand them, see if there were other kinds of invisible rays that let you see bones and other cool stuff and and, and so there's this whole uh cottage industry of of making x-ray machines and, and learning about x-rays and playing with them. And then meanwhile, in parallel to that, scientists began to get interested in phosphorescent materials.

The these are materials or elements uh that glow in the dark after being exposed to light, especially x-rays. If you shine a bunch of x-rays on a phosphorescent material and then you wait for it to get darker the material will glow. Now these kinds of things have been known for for literally forever. And but now scientists were starting to pay more attention to it after all, interesting glowing objects, x-rays, really loving this stuff. This is, this is good juicy science right here. And French scientist, Henri Bacall was monkeying around with, with different phosphorescent materials. He was taking pictures of them, he was smelling them, he was talking to them, you know, the works. And at some point in his investigation of various phosphorescent materials and minerals and rocks and whatnot, he he put a piece of paper over a photographic plate and then put the phosphorescent material on top of the paper to see if he could still take a picture of it.

Now, why did he do this? Well, remember everyone was super fascinated by invisible rays. No one could see x-rays, but they would show up on a photographic plate and, and everyone was interested in phosphorus materials and they thought there was some sort of interesting connection between the two and that if there are x-rays, maybe there are other kinds of rays, you never know, we gotta play around with this kind of stuff, especially if they're invisible because that makes it so much cooler. He found that almost every single phosphorescent material that he would put on top of a piece of paper and then put the whole thing on top of a photographic plate would, would yield nothing you get a picture of nothing, no invisible rays, nothing cool except uranium. When he took a lump of uranium and put it on top of a piece of paper which was sitting on top of a photographic plate. The photographic plate was able to take a photograph of the uranium. Even though there is a piece of paper in the way something funky is going on. This uranium is emitting some new form of invisible radiation.

Uh Very quickly, Henry realized that this had nothing to do with x-rays and actually had nothing to do with phosphorescence. He just accidentally found it, it had something to do with, with something else. So he published his work and at first they were called a Becker rays because that was the fashion at the time, but that quickly and thankfully faded. And then other scientists picked this up like what is going on with uranium? What are these invisible rays coming out of uranium? What are they doing? And can we make a profit with them? That that part comes later after a few years, we got some knowledge and as usual in physics experiments when you have just experiments and the theory hasn't caught up yet, uh it starts with a list of facts. Uh uh Like fact, number one, whatever is happening to uranium to make it glow is not phosphorescence. It's something else because when uranium is glowing, it is transforming itself into something else that is just straight up nuts.

This is magic folks. Like I give you a rock of uranium and then you wait a while and it's not uranium anymore and especially put yourself in the minds of, of scientists in the late 18 hundreds, early 19 hundreds. Yes, we have the periodic table of the elements. We understand that kind of thing. We understand chemistry, but we don't understand atomic nuclei yet. We don't understand what is happening inside of an atom. And just magically like if I give you an apple, you expect it to stay in apple for quite a long time. Or if I give you some graphite, it will stay a graphite, a lump of graphite for a very long time. But if I give you an apple and then you, you, you left the room and then you came back and now it's a a banana that's you're gonna say something funky is going on, right? This is transmutation. This is the transformation of the elements themselves, which should not be possible. And yet here is uranium emitting a invisible Becker rays in transforming into something else.

And in the process, those Bacara rays are some weird form of invisible radiation that we don't fully understand yet. Other scientists discovered that uranium was not alone, other elements could play the same trick. Uh but not every element, you know, like oxygen just stays oxygen, carbon, most kinds of carbon stays stays that kind of carbon. But but, but speaking of carbon, like one kind of carbon with a certain amount of protons and neutrons will be just fine. But then another kind of carbon with a different amount of neutrons, a different isotope will undergo this transmutation. What the heck? And, and this is before we even had the language of protons and neutrons. So you just have different elements like here's carbon, but it's a slightly heavier version of carbon and this one decays or transmutes, it does something funny. But then here's a different kind of carbon with a different kind of weight and it just hangs out forever. This is weird. Uh We discovered through this investigation, new elements that the Pierre and Marie couple, the famous, famous couple loved to do an entire episode on their work.

And what they did, I discovered radium and polo these are brand new elements and they discovered it through their investigations of this process. They also came up with a new name for these invisible rays instead of calling them Becker rays, they call them radioactivity, which is way much better of a name and way cooler of a name. And as usual, I love telling these kinds of stories because as usual scientists were just confused, they had this list of facts where some elements are capable of transmuting into other elements. And in the process they give off invisible radiation like just how nuts is that no one asked for that. No one expected that no one wanted that. But here is nature being weird again. So scientists have discovered a new form of radiation that happens when naturally occurring elements transform into other ones. And it's not every element but some of them do. Uh this radiation had poorly understood properties. Uh The physics behind radioactivity was completely unknown. And what did human civilization decide to do with this newfound knowledge?

Merchandizing, merchandizing, merchandizing. You've got a problem. Radioactivity can solve it here. Swallow this radium pill. Why take a sip of refreshing radium water, bowel trouble hump yourself to a radium enema. And for those of you, these are all real things, folks. Wow. And for those of you listening to this show with kids have fun explaining the last one to them. Seriously. It was sold radium. This new element that gave off invisible radiation and transmuted into other elements was sold as like this cure. All you, you're sick have some radium, put this radium in your body. And then the completely expected thing happened. People started dying from radiation exposure. Just caution. If we ever discuss to discover in the future, a magical substance that gives off an invisible form of radiation. You give the scientist a few years to work it out before you start eating it and putting it in other places. Oh What, what, what is this radiation? What is this radioactivity?

What the heck was coming out of these radioactive substances to make people so sick? Like, yes, it's one thing to expose it to a photographic plate and you know that there are these invisible rays coming out of radioactive materials and there's a certain subset of elements that are radioactive, you know, some kinds of carbon or uranium of the polonium and, and radium. It's ok. What is coming out of it? Why are people getting sick when they eat a radium pill? A further investigation into the nature of radioactivity revealed that there are three kinds and they were named alpha beta and gamma and they, they were named this way because alpha could be blocked. The easiest. Like if you just have seriously a sheet of paper, you can block the alpha radiation. Uh beta could be stopped. Uh You need more than a piece of paper. You need like a metal sheet in order to stop beta radiation. And then if you wanted to stop gamma radiation, you needed an entire block of lead in order to stop gamma radiation.

That's about as far as we got before we developed atomic theory, we knew that radioactivity existed and that there were three kinds. And uh these three kinds of radioactivity, radioactive emissions had different properties. Alpha radiation seemed to be uh pretty heavy gamma radiation looked a lot like a light and photons. But of a of the energy that no one had ever seen before, even more energetic than um x-rays beta were just beta rays were just weird. They could be deflected with magnetic fields, stuff like that. It, it took, it took a lot more experiments to sort out what was going on. And we also had to, by the way, completely develop the concept of the atom in the nucleus to, in order to figure this out. That's right. We were sticking radium pills where the sun don't shine before we even knew what an atomic nucleus was. Sometimes. I'm surprised we managed to survive this long as a species. Anyway, I'll, I'll cut to the chase. I'll tell you what they really are. Alpha radiation is actually a little tiny helium nucleus, uh two protons and two neutrons.

Uh beta radiation. You might know as the more familiar word of electrons and gamma radiation is just super duper high energy photons and we get different kinds of radiation coming out of radioactive elements because the, the transformation of one element to another can happen in, in different ways. And then it, it happens in this way, it spits out an alpha radiation. It happens in this way, it spits out beta radiation. It happens in this way, it spits out gamma radiation, you get the point. So for example, if you have uh an atomic nucleus, which is really just a, a bag of protons and neutrons, I will go into a little bit more gooey detail in a little bit. Uh Sometimes it just spits out a chunk of itself. There you go. Here's some protons and neutrons, that's the alpha radiation. Sometimes a neutron transforms into a proton which releases an electron. Uh but, and also it releases an anti neutrino. But understandably, it took us a lot longer to find that part. Uh gamma rays almost always come along with the others because uh the end product when you have this transmutation, this transformation from one element to another, uh The new element almost always gets left in a super excited high energy state.

I like to say it as a bad case of the jitters just had way too much coffee and it needs to release energy any way it can. And the easiest way is to emit a high energy photon. So that just got usually comes along for the ride. So you get some alpha here or maybe a beta here, but you almost always get gamma at the end of the day. Guess there are also many other kinds of radioactive decay. Uh Because hey, why should physical processes ever be simple? Uh But I'm deliberately not going to talk about them much because it just ends up being a, a recitation of a bunch of tables of, of this decay process with this product or this channel. And you know, I know it's your favorite thing to hear on this podcast, but uh we're gonna skip it today instead, I'm gonna, I'm, I'm gonna go to talking about why, what's going on here. We have some elements that spontaneously. Without anyone asking transform into other elements in the process, they emit different kinds of radioactive emission. Sometimes heavier nuclei, sometimes little electrons, sometimes just high energy radiation.

Sometimes these elements uh decay or transform very quickly, sometimes very slowly. By the way, I've already started to introduce this word decay here. Uh Yes, elements can transform into each other. They even when it comes to this process of radioactivity, they always transform from heavier elements to lighter elements. So that's why it's called decay. Some decay very quickly, some very slowly, some, not at all ever. No matter how patient you are, sometimes one isotope will decay while another doesn't, sometimes there can be entire chains where one element transforms into another and transforms into another and transforms into another. So we're going to ask the physicists favorite word Patreon patreon dot com slash PM Sutter is how you, yes, you, I'm talking to you right now. No, no, no, not you. You how you can keep this show going every single dollar that you contribute helps keeps the show going and, and I truly do appreciate it.

So if you, if you like the show and you're a fan of the show, the number one thing you can do is contribute to Patreon, it's as easy as that. And I, and I'm sincerely grateful for every single contribution. Now, the actual favorite word is why, why, why is this happening nature? This is it, it's like physicists sometimes wish we could just write a letter to nature and say, oh dear nature. Why are you so complicated? Sincerely physicists? Just that simple. Just why, why are there different decay channels? Why are some elements decaying and not others? Why are there different forms of radiation? Why are the the timescales radically different? Sometimes it's microseconds and sometimes it's like 100,000 years. What is going on? What's going on here is that atoms aren't always as stable as they're made out to be. This seems weird. We like to think of Adams as just Adams as, as, as things as, as rocks as, as something to ground our reality.

And after all, I am made of atoms, you are made of atoms. This microphone is made of atoms, your car is made of atoms. This chair is made of atoms, the rocks I'm standing on are made of atoms, everything is made of atoms and if atoms are unstable like then, then that's, that's existential crisis territory. Like what if, what if the stuff inside my car decides to stop being the stuff it is and decides to be different things. It seems like nature shouldn't allow it that if one day oxygen can just decide to be, I don't know, phosphorus that would, that would end badly by the way, or if iron decided to be, I don't know, pick one polonium that wouldn't be so great. It feels like nature shouldn't do this. That atoms should just stay as atoms and they shouldn't be able to transform into each other but they can and they can because atoms aren't always stable.

Don't be, don't get me wrong. Thankfully, most atoms are stable for most of the time in most circumstances. But atoms especially atomic nuclei are are kind of complex. Before I continue, I need to let you know that this podcast is sponsored by better help, online therapy and stress man. Stress really stinks. I get it. It's a stressful world. It's stressful times. It can be a stressful life. Uh When I get stressed out, there's this thing on my neck that starts to hurt and it just doesn't go away. And, and I actually used a therapy to help me uh understand sources of stress in my life and how to deal with them in a more healthy and appropriate way. And I know a lot of you tune into this show to destress, to disconnect to, to educate yourself, to feel better about yourself and just explore the wonderful universe that we live in. And I maybe it's time to also talk to a professional. Better help is customized online therapy that offers video phone and even live chat sessions with your therapist.

So you don't have to see anyone on camera if you don't want to. If you want to wear your pajamas, no one's gonna blame you. It's much more affordable than in person therapy. Give it a try and, and just see if it works for you. This podcast is sponsored by better help and ask a Spaceman listeners get 10% off their first month at better help dot com slash spaceman. That's be tt er he LP dot com slash spaceman. It's easy to imagine, especially with that cartoon picture of the atom, which somehow became the, the default symbol for physics and then somehow even all of science where it was like the little uh little, little tiny bs inside of a nucleus and then these electrons circling around like that's like the most inaccurate picture ever. And somehow it's the international symbol for, for nerds. I don't ever want you to think of an atomic nucleus as a bunch of little glued together with a bunch of little protons and neutrons. That's cartoon, that's kindergarten stuff you're older. Now you can handle it.

An atomic nucleus is like a gooey sloppy sloshy plaid Amoeba like thing that kind of sort of vaguely contains protons and neutrons. So if you picture in your head in a me in Amoeba, that is a better like visual image of an atomic nucleus than a bunch of little BB glued together because you got the protons and neutrons themselves, which are each made up of three quarks and they're bound together. And that itself is a very complex quark gluon thing happening and it's the strong nuclear force that keeps the protons as protons and keeps the neutrons as neutrons. But this strong force uh leaks out of the protons and neutrons them individually. This extra residual strong force is what's responsible for holding a nucleus together. That's right. Atomic. The reason we atomic nuclei exist is because the strong force really is just concerned with holding protons and neutrons together, but some of it leaks out and there's some extra strong force to go around.

And that's how we get all of atomic nuclei. We also have electrostatic forces because the neutrons are electrically neutral, but the protons sure aren't. They all have like-minded charges and like-minded charges uh really, really hate being close to each other. So they're trying to push each other apart while the strong force, they're the leftover strong force is trying to keep things together. Sometimes the weak nuclear force butts in like that friend or coworker you don't really want hanging around, but just inserts themselves into the conversation very awkwardly. That's the weak nuclear force nuclei aren't hard little nuggets. They're, they're a sloshing bag of goo, like pudding, like a bunch of jello and bouncy balls inside of a grocery bag and trying to carry it home and like most sloshing bags of goo, it can be stable for a while. But if you run into problems, you run into problems. Like one problem is uh if, if you have not enough neutrons or you have too many or equivalently too many protons, then the electrostatic repulsion of those protons is, is gonna make this a sloshing bag of goo spill over.

It can't contain itself the strong force uh can't over overwhelming and keep things together. You can also have too many neutrons and then they get too, they're too loosely connected, like they're floating to the top of this goo bag or the outer surface of this goo ball. How many times can I say the word goo in this podcast? The answer is a lot, someone count the neutrons end up at the edge of the glue ball and, and there's just not enough strong nuclear force to go around. And so they end up being unstable and these kinds of atoms, these kinds of nuclei are, are metastable. They can be stable for a while, they can hang out like this for a while. They can stay contained for a while. How long it depends on the particular element in isotope of how many protons and how many neutrons are we talking about? It would prefer to not be in this situation. Nature hates being in unstable and metastable situations. Nature loves being in nice ground state, lowest energy configurations.

Like if you, if you've got this shopping bag and it's full of jello and ping pong balls or bouncy balls and you've got too many it's gonna spill over. You start picking up the shopping bag and moving around, it's gonna spill over. But once you've, you've gotten rid of the extras, the spill over. It's just a lot more stable. It's more likely to stay inside the bag than it was before. And so stuff just happens. Uh a couple of protons and neutrons escape, bye. A proton turns into a neutron or a neutron turns into a proton. These things just happen. They happen because it's a lower energy configuration. The new nucleus, the, the transformed nucleus that got rid of the extras is now more stable and more calm and more quiet and better able to contain itself. How does this process actually happen? And it's all quantum tunneling. You see if I'm an unstable Adam, I've got too many protons or neutrons or whatever. I'm just, I'm, I'm unhappy. I would prefer to be in a lower energy state but to actually get rid of the extra protons or neutrons to actually start the decay process that costs energy.

I have to do something. I have to take a, a like a proton and transform it or I have to kick it out of the nucleus altogether. That costs energy. Now, I will get that energy back because I'll find myself in a lower energy state. And so overall I'll be happy, I've just spent, if I spend a little bit of money, you know, I can buy a better home and I, and I, and I won't be living on the streets anymore, but I got to spend that money first in a classical world. If you don't have the money you can't pay in a classical world. Uh Before quantum mechanics, radioactive decay never exists. It never happens because these atoms, even though they would prefer to be in a lower energy state, they can't pay the bill to get into that lower energy state. They can't spend the little bit of energy to do the actual transformation process. Uh And then end up winning in the end when they're in that lower energy state, they just can't do it. But thankfully, we don't live in a classical world, we live in a quantum world and in a quantum world, you're allowed to borrow a little bit of energy totally randomly.

Just every once in a while, proton hanging out there minding its own business. And then for now I'm a neutron, the weak nuclear force does the work of doing that by the way. But right now I'm a neutron who nucleus is in a better state. It's more stable. It's happier had to cost a little bit of energy, but I got it back because now it's in a better state, it's in a lower energy state or hey, I'm nucleus hanging out. Yeah, I'm, I would prefer to, to do something. It's like switching jobs. Like if you hate your job and you want to start a new job, you have to invest a little bit of money. You, you have to be unemployed for a little bit, which is gonna cost you some money or you have to do some job searching, you know, send polish up your resume, send it out there. You have to put in effort in order to find a better configuration for yourself. In a classical world, you're never allowed to spend that money. You are simply stuck in your job no matter how much you hate it. But in the quantum world, you are allowed, you're allowed to go to the bank and borrow a little bit of money.

So you can have a couple of weeks being unemployed while you search for a new job. Or you can uh you know, take the time off to polish up your resume and, and send some, some resumes out radioactive decay. I don't know how many terrible metaphors I can cram into a single episode but here's another one, radioactive decay is just atomic nuclei nuclei looking for a better job, a more stable situation. But because it's a quantum thing, that means it's a random thing. If I give you a single uranium atom, here you go. Merry Christmas. Happy birthday. Here is your single uranium atom. You will never be able to know exactly when that single uranium atom will radioactively decay into something else. You'll never know. It could be in a microsecond, could be in a macro second, could be in a billionaires. You simply don't know because that's one of the things about quantum mechanics is yes, you can do surprising things. You can punch through potential barriers. You can spend a little bit of energy that you don't have.

As long as you get, uh, get it back later, you can do that. But you can't say when you never know if I'm looking at an unstable nucleus or a metals, stable nucleus and it will radioactive, radioactively decay someday. I don't know when, I don't know when it's actually gonna do it. I don't know when it's actually gonna go out and start searching for a new job. But if I give you a rock full of uranium and there are billions upon billions upon billions upon billions of atoms of uranium in it, then you can start to get some more precision here because you don't know exactly which atom will decay at what time. But you know that given enough atoms and enough time, just statistically on average, a certain number of them will decay over a certain amount of time. And we call this the half life, the half life is a measure.

If I give you something, here's some uranium. The half life tells you how long it will take for half of that lump of uranium to decay into something else. And then you wait another half life, you have a quarter of the uranium left and then you have an eighth and then 1/16 and so on. Some half lives are incredibly short for some elements. We're talking microseconds, some are incredibly long. We're talking hundreds of thousands, millions of years. This is something we have to measure through experiment and observation. Although we can get a handle of it through atomic theory, but each individual radioactive decay process is entirely random. It's like, uh let's, let's keep going with this metaphor then make it up on the spot. Let's say everyone in a company hates their job and you don't know which person is finally gonna quit. If you look at one person, you don't know. Are they gonna quit tomorrow? Is it gonna be next week or are they gonna hang on for a decade? You don't know. But if you have 10,000 people in the company and it's a toxic workplace culture and everyone's quitting, you know, and, and everyone hates their job and moving on to new opportunities, then you can like every week, you know that five people are gonna quit and from there you can construct a half life.

Radioactive decay is a quantum process. Radioactive decay is a weird process. Radioactive decay is a very complex process. I have just scratched the surface of radioactive decay today. I hope the most important thing you've learned from this episode is, is not to stick radium pills, you know, in places. Thank you to Robert. I on email for the question that led to today's episode. And thank you to my top Patreon contributors, Justin G. Chris L Barbeque Duncan M Corey D, Justin Z. Nate H Andrew Aaron S Scott M Rob H Lol, Justin Lewis, M Paul G. John Woxj Jennifer M Gilbert M Tom B Joshua and Kurt M who every single contribution helps. I truly do appreciate it. And hey, if you can't do Patreon, it's ok. It's ok. I don't know where you are in life. I'm not gonna force you to pay to listen these episodes. So just share it, just tell other people about the show, drop an itunes review or uh uh you know, any other podcasting platform review.

Those really do help check out my website PM start dot com. There's links to books that you can buy and, and all sorts of cool stuff. Follow me on social at me. So keep the questions coming. Hashtag ask the spaceman, ask us space man at gmail dot com or just the website ask us spaceman dot com and I will see you next time for more complete knowledge of time and space. The it's always the right time deal. Hey, you wanna go to Mickey D's for lunch? Oh, let's go now. But it's not lunchtime yet. If we're going to mcdonald's, it's always the right time. It's hard to argue with that. There's a deal for every lunch hour at mcdonald's now's the time to get two for 3 99 mix and match a four piece mcnuggets, a mcdole A mcchicken or a hot and spicy mcchicken. Price of participation may vary, cannot be combined with any other offer, a single item at regular price.

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