Are atoms immortal?

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1:14so we've just walked into this massive airplane hangar looking space and if we look down what

1:22Caroline Steel:What can we see? At the moment there is a concrete floor or ceiling above the experiment. Welcome to CrowdScience from the BBC World Service, the show that answers your science questions. It's about 60 metres below ground level, so we look down and below this floor is the experiment. So sort of down this massive shaft. We're visiting somewhere that's been on my bucket list for a very long time. the world's biggest particle physics laboratory, CERN, home of the Large Hadron Collider. And why is there such a massive layer of concrete? The concrete is to stop any particles from escaping from the accelerator or from the collisions.

2:05Caroline Steel:Because it's not good to interact with them as a human. Yeah, it changes your atoms and that's not helpful. We like to keep our atoms as they are. Cheers. We're looking down at an experiment where particles are being smashed together at incredible speeds. Thanks to a question from this week's listener. Hi, I'm Rob from Toowoomba in Queensland, Australia. My question for crowd science is, are atoms immortal? And if they're immortal, why do all living things die?

2:44Caroline Steel:Oh, this is quite a philosophical one, isn't it? It's probably a roundabout way of asking, what is life? Just a small question. We'll answer that in about half an hour, no problem. Yeah, yeah. Well, I guess we have to look at why does a certain combination of atoms become alive? So because it's quite a deep question, I think we should sort of define our terms a bit, which I know sounds boring, but what do you mean by immortal? Well, particles came together to make atoms about 300 ,000 years after the Big Bang, so they've just formed everything since then, and atoms in nature aren't created or destroyed, like they get transformed into other elements.

3:39So if they're neither created nor destroyed, does that mean that they go on forever?

3:47Caroline Steel:So we have a very big question about very small things. Are atoms immortal? First things first, what's an atom? Luckily, we're in the perfect place to find the answer. Showing me around CERN in France, well, actually also in Switzerland, it straddles the border, is Marco van Leeuwen. He's a physicist from the National Particle Physics Laboratory in the Netherlands. So most of the matter that we know comes as far as we know from the Big Bang. In the Big Bang, the energy density was so large that there was no matter. Everything was energy, but as things expanded and cooled down, matter was produced.

4:29Caroline Steel:So matter is the stuff of the universe. And all matter is made up of atoms. Atoms are the building blocks of everything, from the shoes on your feet to the clouds in the sky. And each atom has two main parts. The nucleus and electrons, a cloud of electrons. And the nucleus contains protons and neutrons, so it is positively charged, and the electrons are negatively charged, so they are bound together. So we have a nucleus or core with positive protons and neutral neutrons, surrounded by negative electrons. That's an atom. But the number of protons, neutrons and electrons can change. So they don't necessarily stay the same.

5:16There are two levels of change that you can have.

5:20Caroline Steel:Number one, electrons can come and go. And this is what you would call ionisation. And this is a process that can easily be reversed. And the second change that can happen is the atom can go through radioactive decay. Which can change nuclei from one type into another. So it changes one type of atom into another. So protons in the atom's core can become neutrons and neutrons can become protons, which is quite a big deal. The delicate balance of protons and neutrons is what gives different atoms their unique properties. If the number of protons or neutrons changes, the type of atom changes. and that means it becomes a different element.

6:02One example is potassium which you have in bananas. If it decays, it becomes calcium. It becomes a completely different element. And there's a very small amount of radioactive potassium in all bananas. And so this is a naturally occurring process and that is one way that an atom changes type, so to speak.

6:24Caroline Steel:Atoms can also decay by shedding two protons and two neutrons at once, becoming a new, smaller atom. So again, a different element. But does that mean the original atom is gone? So atoms are not immortal? It's an interesting question. So one way to answer this is that for a physicist, the atom stays, it just changed a little bit. But for a chemist, you change potassium into calcium or something else. It's a completely different substance. OK, so you would say from the point of view of decay, atoms are immortal, in the sense that even if they decay, they still live on to be an atom. So atoms can change or lose particles, becoming different, sometimes smaller, elements.

7:16Caroline Steel:According to Marco, an atom that's lost a few particles is still the original atom. A mug that's lost its handle is still a mug, but maybe it's best to call it a cup instead. But the smallest atom of them all, hydrogen, is just a single proton and a single electron, which means that if it lost either of them, it would no longer be an atom. So yes, a hydrogen atom is a proton and an electron. Super simple. And does that hydrogen atom decay? As far as we know, no. This is Matthew McCulloch, a theoretical physicist at CERN. He spends his time trying to understand how the particles which make up our universe behave.

8:03So if you wanted to know if a hydrogen atom, or more practically, a proton.

8:08Caroline Steel:Why is that more practical? Well, because if a hydrogen atom can decay, it would require that the proton or the electron could decay. Yeah. The electron is the lightest charged particle. And so there is nothing else negative for it to decay into. This is all theoretical, but it means that if a hydrogen atom were able to decay, it's the proton that would be decaying, not the electron. We've never actually seen this happen, but there are scientists who are trying. So there are different ways in which one can do this, but the most sensitive way, the most impactful way in which this is done, is at an experiment in Japan.

8:51It's called Super Kamiokande. So what they do is they have an enormous tank. This tank, I think it's something like 55 ,000 tonnes of ultra-pure water.

9:03Caroline Steel:And water contains a lot of hydrogen atoms. It's about a kilometre underground, and they literally watch it. And so if the protons in the hydrogen were to decay, they would see a characteristic flash. That flash would be because one of the particles that a proton could decay into is a photon, which is a particle of light. And so, yeah, if they were to observe a proton decaying in this big tank of water, then that would be a great breakthrough, but they have not. But just because we haven't seen it doesn't mean it can't happen. Hydrogen atoms might just decay too slowly for us to detect. When the first proton in that tank of water breaks down into light, humans might already be extinct.

9:49But we can put a limit on how rapidly a proton decays, And it seems like it takes longer than 10 to 34 years.

9:56Caroline Steel:10 to the 34 years. So that's 10 to the power of 34, which means 10 with 34 zeros afterwards. So from a human point of view, that's going to be well beyond a lifetime, well beyond our species, well beyond the probably length of the Earth's life and our solar system. No, it is. No, in terms of threats to society, it's pretty far down the list. In fact, 10 to the power of 34 years is way, way longer than the age of the universe. It's the length of time since the Big Bang, times a trillion, times a trillion again. So it looks like hydrogen atoms might be the best candidate for being immortal. Yes.

10:47Caroline Steel:What is your sort of, I guess, hunch isn't very scientific, but if you had to guess, do you think that hydrogen atoms are able to decay or not? This is where at least the question becomes essentially subjective or speculative. I would say that I would expect that protons can ultimately decay. but so in practical terms yes I would say that atoms are immortal but in in absolute terms I don't think they would be. So technically atoms may not be immortal. Even the smallest atom hydrogen might decay into a couple of smaller particles and a flash of light. Not an atom. However a hydrogen atom would take so long to decay that from the point of view of life on planet Earth, we can basically ignore it.

11:43Caroline Steel:So far, if you're happy to accept that one type of atom changing into another type of atom, like a potassium atom decaying into a calcium atom, is still the same atom, atoms look pretty immortal. But we're at CERN, home of the Large Hadron Collider, where particles are smashed into each other at top speed. Could that destroy an atom? We'll find out next.

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13:13Caroline Steel:You're listening to CrowdScience from the BBC World Service, the show that answers your science questions. I'm Caroline Steele, and we're trying to answer a question from listener Rob. Are atoms immortal? which has brought us to CERN where atoms are literally smashed together. Here's Marco again. One thing that we actually do in our experiment is that we collide ions of lead and we collide them with very high energy and what then happens is that they completely transform almost into pure energy and then they fall apart in many, many pieces. Marco works on ALICE, which stands for A Large Ion Collider Experiment.

13:56In my experiment in Alice, we study these collisions, and that is where we produce a very high temperature. The temperature is, we say, 100 ,000 times the temperature of the core of the sun. And at those temperatures, the nucleus really melts, and you get a liquid that consists mostly of quarks, quarks and gluons.

14:17Caroline Steel:Quarks and gluons are tiny particles which make up the protons and neutrons in an atom's nucleus. And when you make two atoms collide, you get a quark gluon soup. We call that the quark gluon plasma. So the atom is completely disassembled, if you want. So you would say that stops the atom being immortal? You've broken it down? You've completely destroyed it into its pieces. But I guess this high-speed collision of two atoms doesn't happen in normal life, only in your collider? Or does it happen in normal life? It does happen in normal life. In the universe, there are high-energy particles, which we call cosmic rays, because for us they come from the cosmos and they rain down on the earth so to speak and when a cosmic ray hits an atom it also can destroy the atom and this actually happens in our atmosphere cosmic rays hit the oxygen and nitrogen atoms in the atmosphere and they can be destroyed by that process it depends on the energy and on exactly what happens but this happens relatively frequently or occasionally in the atmosphere and what happens when a cosmic ray collides with an atom in our atmosphere so say it collides with an oxygen atom can you talk me through the process so i mean the way we picture it is it's like a little bullet hitting a bunch of grapes and they but they get spread around they fall apart and the point is that when you have an atomic nucleus the binding is quite closely regulated so if you take out a few protons and neutrons it normally falls apart so even at fairly low energies that can happen if you go to higher energies you end up heating up the nucleus so much that it kind of evaporates or melts okay so these collisions are happening all the time above us is that right yes yeah between cosmic rays and atoms how likely is it that an atom is going to get hit by a cosmic ray and sort of end its life so in a way it's it's almost bound to happen.

16:17But of course in our atmosphere we don't see the composition of the atmosphere change because of that. So it is fairly rare.

16:25Caroline Steel:Atoms may not collide with cosmic rays very often. But given enough time, it will happen. That's if an atom doesn't get unlucky and end up in Marco's experiment first. So we take the door on the left.

16:44Caroline Steel:Marco took us to see the Alice control room. After you. Hello. Hi. Wow, this is cool. This is the radio crew from the BBC World Service. Yeah. And we're doing a kind of popular science interview about whether atoms are immortal so i explained that if you put enough energy in they are not immortal you're the atom killers yeah so this is the control room for alice yes and in front of us we've basically got a lot of huge screens really really long curved screens and people sat doing what looks like complicated physics on them. Yeah, it sort of looks like what I imagine, I don't know, a rocket launch to look like, but instead we're talking really small.

17:42Caroline Steel:So this is essentially where you destroy atoms. Well, the atoms are destroyed in the collider underground. Here we control the camera that makes pictures of these collisions. This is where you watch the atoms being destroyed. Exactly. There's actually a picture over there where you see the tracks from one collision. So you're in the middle you see a schematic of the detector all the white lines are particles that were produced in our detector wow there's so many particles flying off that's what you get at these very high energy so you have these were oxygen oxygen collisions and when you have these relatively large systems colliding you produce hundreds or even thousands of particles that we all detect simultaneously in our detector.

18:29And our detector is like a giant digital camera. So the detector is about 16 metres tall. You see here only the corner.

18:38Caroline Steel:Yeah. And it's about 16 metres wide and 30 metres long. And the pipe which the atoms are accelerated along is 27 kilometres long. A 27 kilometre loop which straddles two countries. An enormous experiment to study the tiniest pieces of our universe. It's a marvelous place. The particles go around 11 ,000 times per second. 11 ,000 meters per second? 11 ,000 times per second. They go more or less with the speed of light. They go in loops and each particle passes here 11 ,000 times per second. Whoa, that's so fast. Yes, exactly. So the control rooms are close to the detectors. We are now in a building on the surface but underground 16 meters below more or less directly below our feet is the detector how do you get down there there's a lift to get down to the detector at the moment we can't go there because the accelerator is on so you go down there's only one stop you go down in about 20 seconds 50 meters underground but unfortunately the accelerator is turned on and when there are beams and collisions happening in the accelerator particles are produced which is radiation so it's not safe for people.

20:00Caroline Steel:So we can't get up close and personal with the experiment because when two atoms are smashed together, the particles they give off can be dangerous. Fair enough. Let's stay above ground. Now I would say that if you can break an atom into lots of smaller pieces that means that the atom is not immortal. You can destroy them if you hit them hard enough. And even if you don't meddle with them and kill them what would you then say? Then it's more tricky. Because you could get an atom that's really lucky it's one that you don't break or that doesn't get hit by a cosmic ray and then that individual atom could be immortal.

20:41Caroline Steel:Or I guess there's the argument that given enough time it will get hit by a cosmic ray or meddled with by a physicist? I think that most atoms meet their fate at some point, but they can also be reborn and then the cycle starts again. If you're an atom, there are a couple of things that can mean it's game over. Getting hit by a pesky cosmic ray or ending up in particle accelerators like the Large Hadron Collider. So, listener Rob, I'm sorry to say, atoms are not immortal. But the vast majority of atoms that make up planet Earth will still be there when we die, when our children die, and even when the human race ends.

21:26Caroline Steel:So atoms are not technically immortal, but from the point of view of us mortal beings, they might as well be. Which brings us to the second part of Rob's question. When we consider everything is made up of atoms, what is life? I think there's a difference between immortality and mortality versus living, right? This is astrobiologist Betel Kacchar from the University of Wisconsin-Madison in the US. She's looking for life beyond Earth. So she thinks a lot about life in its simplest form. We are composed of chemicals. There's no doubt about that. But certainly something quite unique happened on our planet that we don't see anywhere else.

22:10This is the only place where atoms transition into a state that exhibits living behavior.

22:16Caroline Steel:So where do you sort of draw the line between atoms coming together in, I don't know, a star that's amazing and powerful but isn't alive, and atoms coming together to make life? Like, what's the kind of special thing about a cluster of atoms that makes something alive? So think about a snowflake. It's just a matter of chemicals assembling and then forming this stable shape and then existing for a little bit. And then they melt because they cannot survive and the conditions change. But if that snowflake goes on to make more snowflakes, which it can't, that precise configuration of atoms would count as alive.

22:57So life is a bit of a snowflake that persisted for billions of years. It's a snowflake that gives birth to another snowflake, that gives birth to different snowflakes, and then they form a community of snowflakes that forms an entire biome,

23:10Caroline Steel:that forms an entire ecosystem that changes the planet. But snowflakes don't do that, so they aren't alive. Unlike bacteria, plants and animals, which can make new versions of themselves, new configurations of atoms. So that's the difference, right? This is still the same chemistry, but this time life is chemistry that has a memory. So that's the difference between just some static atom collection versus life. So we need to maybe separate life from its own composition and rather try to extract it as a behaviour. That's why the reproduction, the competition, the cooperation, the different dynamics over time comes into play.

23:51Caroline Steel:So life is more than just a combination of different atoms. It's about the way that those atoms interact with each other, which might sound vague, but describing life in terms of atoms isn't the easiest task. We can definitely categorise life, but we also need to resist simple narratives when it comes to describing what life is. Yes, for sure, we can see that life needs to reproduce, but so does a lot of chemicals. They can create more chemicals. But life has its capability of eating whatever is available around it. We all depend on some substance, like we cannot survive without eating. and everything that is alive lives and everything that is alive produces something that is then food for something else around it.