Ideas - Our Bodies, Our Cells: An audio exploration of life's building blocks

Episode Date: May 8, 2024

Our bodies are a great paradox. We are made up of trillions of cells that are both independent and interconnected units of life. IDEAS travels into the microscopic complexity of the human body to explore sophisticated nanomachines — and probe the deep mysteries of a subatomic world. *This episode originally aired on Jan. 31, 2024.

Hey there, I'm Kathleen Goltar and I have a confession to make. I am a true crime fanatic. I devour books and films and most of all true crime podcasts. But sometimes I just want to know more. I want to go deeper. And that's where my podcast Crime Story comes in. Every week I go behind the scenes with the creators of the best in true crime. I chat with the host of Scamanda, Teacher's Pet, Bone Valley, the list goes on. For the insider scoop, find Crime Story in your podcast app. This is a CBC Podcast. Welcome to Ideas. I'm Nala Ayed. We humans have always wondered about the mysteries of existence,

the nature of the cosmos, our place in it, and, perhaps the deepest mystery of all, how life as we know it came to be. I spend a lot of my life wondering about how this extraordinary complexity arose. Where did it come from? How did it get to be there? Theologians, storytellers and thinkers have obsessed over these questions for eons, and so have scientists. I was asking almost philosophically, you know, why am I here? How do I work? How does it all go together and why? You know, why am I here? How do I work? How does it all go together and why?

But what if the biggest metaphysical questions turn out to have physical answers within what we're really made of, which is to say the 37 trillion cells that make up the human body. 37 trillion cells, jammed full of baroque but elegant machinery. Each one living independently, but intimately connected with the other 37 trillion cells. Humans were ecosystems of these living units, our existence the result of a cooperative agglomeration. We were a sum of parts. And yet the cell was one of nature's best-kept secrets until a few centuries ago.

I've often looked at science, the laws of nature, the structures of the cosmos, the cycles of the natural world, as a way of making sense of the strangeness, complexity, and the beauty of life. Ideas contributor Aaron Collier was curious about the secrets of life harbored inside all of those cells. The life of an organism reposes in the life of a cell. A passage from Song of the Cell by Siddhartha

Mukherjee, read by Dennis Boutsikaris. Hmm. A life within a life. An independent living being. A unit that forms a part of the whole. It seems natural to look to very big things

for answers to very big questions. But what happens if we look instead to the tiny things that are a part of each one of us? You know, a cell is interesting because on the one hand, we think of it as the building block. That's Sarah Otto,

an evolutionary biologist at the University of British Columbia. And what she says here Otto, an evolutionary biologist at the University of British Columbia. And what she says here made me see our 37 trillion microscopic cells a bit differently. All of our body in any animal or plant that you see is composed of these kind of repeating units of cells. How many is 37 trillion? Okay, let me put it this way. is 37 trillion. Okay, let me put it this way. That's how many seconds there are in 1.2 million years. That's how many living entities are you. So like, how do you keep 37 trillion things all on the same page. A cell is a package of information that is translated into chemicals

that can reproduce themselves, that can create tasks, that can often work together to create larger tasks in organs and tissues. David Balinski is a pioneering medical illustrator and animator. You really should see his animations of the fantastically busy worlds inside our cells. It's filled with nanomachines that carry out the instructions in the DNA, whether that be replicating itself, whether that be repairing itself, whether that be signaling other cells, or whether just respiring, having its own metabolism. So the cell is, in some sense, very, very simple, and in some sense, one of the most complicated things that has ever evolved.

Nanomachines with their own metabolism. Cells replicating and repairing themselves. Makes you want to get inside a cell and see it all for yourself. So here's what we're going to do. We're going to shrink ourselves down to the size of a molecule and get inside. Trust me on this one. Okay. Now, we just have to get through the cell's border, the membrane.

So it's the skin that surrounds a cell, and if you want to get into the cell, you've got to cross it. The membrane, the container of life that keeps the cell in one piece and also connects it to all the other cells in the body. Well, the membrane is unbelievably thin from our human point of view. It's actually about five millionths of a millimeter thick. Nick Lane, an evolutionary biochemist at University College London and the author of acclaimed books like The Vital Question, Energy, Evolution, and the Origins of Complex Life. If you were to shrink yourself down to the size of a molecule, then the membrane would be a kind

of a sea that was spread out in front of you, like a shallow sea with something underneath it. It's moving, it's animated. So you'd think it wouldn't be so hard to go through the membrane, but it's also a no-nonsense border guard. It's not easy to cross because it's unlike the sea. It's not made of water. It's actually made of oils. It's kind of oily inside and the surface of it prefers to be with water. So it's a little bit like a soap bubble.

There are islands of things floating around in it which are actually giant proteins. Some of the proteins that are on the surface are signaling proteins that tell the world what the cell is. And cells have evolved as enormous machinery to help pump in things that it needs. Some of them are poor proteins which are portals through which you might want to go if you are for instance a glucose molecule and you want to get into the cell to help its metabolism. Of course the glucose molecule can't get into the cell by itself it has to be attached to an insulin molecule which escorts it in. Some things just kind of sneak across. They're so small it

just sneaks across the membrane. But other things you have to open up the gate and this opens up the gate and lets in the types of nutrients and lets out the type of poisons that it doesn't want. Let's see if we're small enough to sneak across. In we go. enough to sneak across. In we go. I mean, I imagine it would sound like going deep into the sea or something. If you think of oil spreading on water, it's a little bit like that, really. There's constantly movement. And that, I imagine, would lead to quite a lot of gurgling noises as That was weird. But we're in. This thing is microscopic, but it feels enormous. Overwhelming, actually.

If you were to shrink yourself down to the size of quite a small molecule, If you were to shrink yourself down to the size of quite a small molecule, that cell would be like living in a metropolis on the scale of New York or London or something like that. So it would be like standing in the center of Manhattan. And it's full of machinery and hustle and bustle. I'd see a nucleus over there, which is where all the information in our genome is contained. I might see mitochond nucleus over there, which is where all the information in our genome is contained. I might see mitochondria over here, which is the powerhouse and where our energy is created.

There's the Golgi apparatus, the endoplasmic reticulum. There are structural proteins, microtubules, some of which are used for structural support, some of which are used for transport inside the cell. Some of which are used for structural support, some of which are used for transport inside the cell. You've got clouds of other chemicals, you've got amino acids, you've got things which support the cell but also provide the material for the cell to use to make proteins to repair itself, to move, to function in the tissue as a productive member. So you wouldn't see from one side of the cell to the other because there's too much stuff going on all at once.

And cells are nothing if not efficient in how they pack what they've got. And the packing material is this really thick goo, cytoplasm. is this really thick goo, cytoplasm. Cytoplasm is the internal part of the cell where water resides, and it is the substance in which float or are fixed the organelles, the small organs that make the cell function. The cytoplasm is, in a sense, a salty sea. We tend to describe it as aqueous, which means it's water-based, and it is water-based, but it's really gloop.

I'm never going to get this stuff out of my clothes. But this gloop has real structure, and it's amazing that things can happen so quickly in gloop. You kind of imagine yourself being stuck, and yet the rate at which this protein machinery operates through this gloop is incomprehensible. So the cell's membrane is a shape-shifting container, impregnable or porous, depending on the cell's needs. And it holds this cytoplasm, the gloopy sea, in which all of the cell's myriad processes happen. With all of this stuff happening, complicated machinery, stuff in motion,

your eyes would hardly know what to focus on. Well, the things that would catch your eye would be the majesty of the cytoskeleton, which is basically long, thin tubules that sometimes branch that create an internal structure for the cell. Tremendous cables which would stretch right off into the distance and astonishing machines that can strut along this cyt of skeleton and haul cargo behind them. Proteins are transported and shuttled across the cell along little conveyor belts and that those kind of filaments help order and move things where they need to go inside the cell. So it's actually much more complex and more like a factory line a little bit. The kind of environment you would see in a science fiction movie where you've got a three-dimensional city with not just one level of motion. All three dimensions have motion, whether you're transporting things on microtubules

that get built on the fly in front of the moving kinesin. So the cell is a three-dimensional feast of motion. But there's order to all this motion. I describe it as a railway line almost. And things can get attached to this, and they can go off in a particular direction at pretty fast speeds to get around this whole city in a matter of minutes.

Just imagine getting all the way across Toronto, Montreal or Vancouver in just a few minutes. That's how fast this stuff moves. And this trafficking is extraordinarily well organized. They also provide highways for kinesians, which are specialized nanomachines that will carry things from one side of the cell to the other. You've probably got 10,000 to 100,000 kinesins walking along these pathways at any given time in a cell. It reminds me of the perpetual but directed frenzy of activity you'd find in a beehive or an ant colony. But all of this is happening in just one cell.

In a narrow sense, a cell is an autonomous living unit that acts as a decoding machine for a gene. Genes provide instructions, code, if you will, to build proteins. Proteins enable biological reactions, coordinate signals within the cell, form its structural elements, and turn genes on and off to regulate a cell's identity, metabolism, growth, and death. They are the central functionaries in biology, the molecular machines that enable life. Proteins are both the workers and the products of cells.

They're built from little pieces, amino acids. And these amino acids, when strung together, fold. And when they fold, they adapt properties that are based on the sequence of amino acids. So you could just think of it as a string of building blocks that are joined together, and they will twist and coil into a particular shape. There are multiple shapes, they're constantly changing as they catalyze reactions and do chemistry in the cell. So life as we know it depends on a kind of super high speed, constantly changing molecular origami.

There's a combination of order and disorder. But the fact that it doesn't all fall to pieces, that's driven by the fact that these big proteins, these giant molecules, they have basically stable states and they switch between these different stable states at extraordinarily fast speeds. So how do you get that sequence of amino acids? You have some molecules inside the nucleus that will look at a gene on the DNA, unwrap the gene, copy one half of that DNA and create a copy called messenger RNA. half of that DNA and create a copy called messenger RNA. Then that new messenger RNA, aka mRNA, is whisked away to the job site. This messenger RNA is basically instructions for how to assemble a protein. And the messenger RNA gets escorted to a ribosome, which is a two-part protein that is stuck on a membrane in the endoplasmic reticulum. And there are tens of thousands, maybe hundreds of thousands of ribosomes in a single cell.

The job of the ribosomes is to pump out proteins. The ribosomes are giant factories and they build new proteins. And they build them at a pretty impressive rate. This is where the ribosome performs a fabulous trick with the messenger RNA. The mRNA gets threaded into the ribosome and matched to an amino acid that is brought in by a transport protein. It's flicked into the chain, and one by one, each of these amino acids is collected to the chain. And when it is finished, they will fold into a functional protein, where each amino acid in sequence has a different property that it describes to the protein. The ribosome is essentially the original 3D printer.

These newly minted proteins still have to be sent to where they're needed, either to do some job inside the cell or dispatched to other parts of the body. The whole process can be imagined as an elaborate postal system. The whole process can be imagined as an elaborate postal system. It begins with the linguistic code of genes, RNA, that is translated to write the letter, the protein. The protein is written or synthesized by the cell's letter writer, the ribosome, which then posts it to the mailbox. The pore routes it to the central posting station, the endoplasmic reticulum, which then sends the letter to the sorting system, the Golgi, and finally brings it to the delivery vehicle, the secretory granule.

There are, in fact, even codes appended to proteins that enable the cell to determine their ultimate destination. And you thought the internet was an impressive network. Imagine a social media app with trillions of users and every single user is following everyone so the proteins that are created by a cell are its destiny and they are its function and lots of different things are being made by different cells but they are all doing so with a pattern that's imprinted on their DNA. Everything our cells do is for a reason.

A body that's made of trillions and trillions of tiny things that seem to know what they are and what they're doing. And they know what all the other cells are doing. Doesn't it seem like they're sentient? It's often ascribed to cells that they are intelligent in that they know what to do. They know how to repair when there's an injury to a tissue. So cells aren't really intelligent, but cells are programmed to be exquisitely sensitive to their environment and to respond with exquisite precision to their environment. Hmm. I don't know. Cells definitely seem intelligent to me. I think we're going to have to come back to this point later.

One thing is beyond doubt. Cells can sense and respond to their environment with such precision because they contain huge amounts of information. Our genome. The information in cells is held in the great library in the middle of the nucleus where DNA is stored and it's wound up very carefully around giant protein complexes. So it's an extraordinarily condensed system of information storage in there. Information storage millions of times more efficient than a computer hard drive. When I was taught biology, I was taught, you know, there's DNA, our genome inside the nucleus,

but it was helter-skelter. Well, it's not helter-skelter. It's more like a very fine-tuned waltz. This dance of information, the billions of instructions in our DNA, wouldn't be much use to the cell if they weren't intelligible, retrievable, reproducible. So our DNA is split up into smaller volumes and bundled in chromosomes, 46 of them in us humans. Just try to picture it. I think initially I might see these little coiled structures and I might say

oh look there's 46 of these, 23 that seem kind of similar to the other 23. There's one that's kind of puny if I were in a male with a Y, whereas if I were in a female, I wouldn't see that one. I would only see two Xs. They're coiled around these proteins called histones that keep it from getting too tangled. But then I might see, oh, look at this spot. And that's opened up, and there seems to be a lot of protein that's transcribing or copying off of the genome. So that is going to these giant factories, the ribosomes, which is going to convert the sequence of letters in the RNA into the sequence of amino acids in the protein.

So much rapid movement and activity on such a small scale. But here's a spectacle that you really don't want to miss. What I want to do is go inside the nucleus and watch the dance of the chromosomes as they came together and the cell divided. A lot of preparation goes into cell division. The cell gathers molecules, summoning and synthesizing those that are crucial to metabolism and sustenance,

and increasing them in number before they will be apportioned to the two daughter cells. The most noticeable thing when a cell divides is that the nuclear membrane dissolves. Every single DNA strand then opens up and starts copying itself. But in the form of another DNA strand that's then expanded out until the whole chromosome is copied. And here's where the cell becomes a nanochoreographer. a nanochoreographer. The cell takes the three and a half feet of DNA, duplicates it,

and lines the two duplicate portions of DNA in the center of the cell. These duplicate DNA portions have supercoiled themselves into very, very compact shapes so that they can be pulled along from the poles of the cell away from the center. The cell even performs quality assurance.

This is a time when the cell checks and double-checks the fidelity of DNA replication, guarding against damage to DNA or a devastating event in a chromosome. A cell showered with DNA-damaging radiation or chemotherapy might halt at this stage. Those kind of DNA strands that are formed are then pulled apart by the cell. They are attached to these kind of, again, little anchors that move in two directions. And those anchors create tension and pull those chromosomes apart. and those anchors create tension and pull those chromosomes apart. And the microtubules that pull these chromosomes along work in tandem to make everything look very symmetrical

and very pretty actually when you see a cell in its cell cycle dividing. And once the organelles and the DNA on both sides have been properly situated, the membrane pulls down between the two halves of the cells, pinches off, and you've got two daughter cells, at which point the nuclear membranes reconstitute in each of the daughter cells, and the cell takes on its standard look that it had before mitose. You know, what gets me is not just what cells do, it's how they do it. What we know is still kind of the tip of the iceberg of the complexity of the things that is continually amazing to me are not only the fact that a cell can reproduce many, many, many, many times using the same template in the DNA, but with the three and a half billion different parts that make up DNA, this replication can happen flawlessly, seamlessly.

DNA, this replication can happen flawlessly, seamlessly. And yet, when it doesn't happen seamlessly and flawlessly, there are other mechanisms that the cell has to repair, to scan the DNA. And there are preserved genes in DNA of humans that were probably invented three billion years ago. Billions of years of evolutionary trial and error. So that process is just so large and kind of repeated in organism after organism that it can lead to what seems to us as these kind of magical creatures that are able to carry out complex tasks. So our genomes, I think of them as a treasure.

They're a treasure trove of all of the adaptations that the organism has undergone in its last four billion years of evolution that allowed all of its ancestors to survive. Because if we see an organism today, those chunks of DNA were passed on from things that were able to, lucky enough to survive. But they're also our legacy to the future there. What connects us to our children and grandchildren and great-grandchildren. We know as humans the kind of capacity of stories. Stories connect us to the past.

They also connect us to the past. They also connect us to future generations. And so you can think of DNA as the most powerful story that's ever come to be. You're listening to Our Bodies, Ourselves, a documentary by electronic composer and theatre performer Aaron Collier and Ideas producer Chris Watskow. Ideas is a podcast and a broadcast heard on CBC Radio 1 in Canada, on US Public Radio, across North America on Sirius XM, in Australia on ABC Radio National and around the world at cbc.ca slash ideas.

Find us on the CBC Listen app and wherever you get your podcasts. I'm Nala Ayyad. Hey there, I'm David Common. If you're like me, there are things you love about living in the GTA and things that drive you absolutely crazy. Every day on This Is Toronto, we connect you to what matters most about life in the GTA, the news you gotta know,

and the conversations your friends will be talking about. Whether you listen on a run through your neighbourhood or while sitting in the parking lot that is the 401, check out This Is Toronto wherever you get your podcasts. We may have only one life to live, but the number of living things inside of us is jaw-dropping. 37 trillion cells, all working individually and collectively to keep us alive. Each and every cell, a marvel full of mechanisms, energy generators, protein factories, a communications hub, and storehouse and decoder of information.

As we continue with our bodies, our cells, we'll zoom in closer and closer to pursue the most fundamental foundations of our existence and the existence of everything that has ever lived on Earth. of everything that has ever lived on Earth. I've been rhapsodizing about the mind-boggling complexities and intricacies of our bodies, essentially the most complex and sophisticated machines on the planet. So the origin story of our top-shelf machinery might feel a bit humbling. All of life shares a common ancestor. It was missing a lot of the things that we take for granted in animal cells and plant cells and fungi and so on, which all have essentially the same stuff. So human cells,

yes, they're masterpieces of natural engineering, but they're not all that special as far as cells go. Say that you could teleport from inside a human cell to a cell inside of a tree frog, or a lobster, or a slime mold. You would struggle to tell the difference. You would think you were right at home inside a human cell. They've got the same machinery. All of the information processing works in exactly the same way. It would be like crossing the world to go to some almost unknown place and discovering it's just like home.

So there's no doubt that we share a common ancestor, even with the bacteria that could kill us. It's basically the same stuff, we've just got a lot more of it. That means if every living being traced its ancestry back far enough... We're all equally old. All organisms alive today have had roughly four billion years of evolution, so we've all evolved for the exact same amount of time. And so we've all evolved for the exact same amount of time. So the origin of life happened very early, around 4 billion years ago,

and gave rise to bacteria and another group of cells that look a lot like bacteria called archaea. And what they have in common is that they are, by our own standards, pretty small, pretty simple cells. And they dominated the Earth for literally two billion years. And then on one occasion, which is hard to fathom, our own type of cell arose. Not the result of a gradual incremental increase in complexity over a long period of time. It seems to have been something much more abrupt and dramatic than that. It's thought that many, many eons ago,

a single-celled organism swallowed a bacteria that happened to be really, really good at making energy. And rather than digest this bacteria, the single-celled organism incorporated this bacteria into its own functions and became much more efficient at metabolizing and making things because it suddenly had a power plant inside of it. Okay.

So the thing that made human consciousness and all the life we see around us possible was this one time two billion years ago when a single-celled organism swallowed a bacterium. Those bacteria went on to become the mitochondria, the power packs of our own cells. It's hard to, again, comprehend that perhaps 40% of our cells are made of bacterial cells, the mitochondria. And that just gives so much extra energy availability that it allows for this accumulation of complexity. And think about this.

Our life force is derived from the electrical power of bacteria. So bacteria generate this charge on the membrane. the electrical power of bacteria. So bacteria generate this charge on the membrane. And the way in which all life works with its energy is to generate a really powerful electrical charge on the membrane. But if you were to stand next to it as a molecule, what you would experience would be about 30 million volts per meter. That's like a bolt of lightning. And that's something which is difficult to control.

And what we have done is internalize all of that. All that voltage in our mitochondria. The mitochondria are where respiration happens, cell respiration. This is where all the energy that we need to stay alive, to move around, to think, to do anything at all, it's all coming from the mitochondria. The mitochondria takes proteins, sugars, and other things and breaks them down and harvests the energy

from breaking the chemical bonds. Sounds simple enough, right? Well, the molecule-sized version of ourselves on this magical journey would be wise to stand back from this microscopic blast furnace. We're stripping out hydrogen atoms from food and we're burning it in oxygen. And that's the essence of respiration.

But we're not just taking a hydrogen atom and burning it directly. That would be a huge conflagration and it would just literally go up in smoke. What we're doing is something really pretty amazing. We're splitting the hydrogen atoms into their component parts, the electrons and the protons. And the electrons are being transmitted to oxygen through a whole series of giant proteins that sit in the inner membrane of the mitochondria.

And so electrons will hop. I imagine them hopping along lily pad, like frogs hopping along a lily pad, and eventually they're kind of pulled through by this ravenous beast at the end, which is oxygen, which is eating all the frogs, you might say. That's a current of electrons to oxygen. And that's powering work.

And the work it's powering is pumping the protons across the membrane, which seems like a very peculiar thing to do, but that's what happens. That's driving everything in cells. You may find as many as thousands of mitochondria in a single normal cell, and each mitochondrion has got its own membranes, and embedded in those membranes are the proteins that are doing a lot of the work. Those proteins are basically

giant rotating molecular motors. Protons are pumped through them to create molecules called ATP that carry energy wherever it's needed to do the things that cells do. And it's rotating at something like 200 revolutions per second. And each rotation will make three ATP molecules. There might be 10,000 of these rotating motors on every mitochondrion, and every one of them is producing hundreds of ATP molecules per second.

It's incomprehensible the speed at which these things are working. We turn over our own body weight in ATP every day, something in the order of 60 to 80 kilos, depending on our size. I know, it sounds insanely complicated. Like, this is how we get all of our energy to do anything? To live? We're pumping something in the order of 10 to the power of 24 protons per second. That's in the order of the number of stars in the known universe.

That's the kind of scale of proton pumping going on. Every second, that is what is keeping us alive. We seem so placid on the exterior, and yet there's all of this astonishing activity happening inside. And if you block that in any way whatsoever, then we'll be dead within minutes. This is what being alive really is.

I guess we'd better not block that then. Let's take stock for a moment. A cell might have hundreds of thousands of ribosomes, tens of thousands of kinesins, and thousands of mitochondria. tens of thousands of kinesins, and thousands of mitochondria. And each of those mitochondria has upwards of 10,000 rotating molecular motors. And there are all the other parts of the cell on top of that. So that's well over 10 million bits of machinery in a single cell.

Multiply that by 37 trillion cells. Okay, so this is just a back-of-the-envelope calculation, but it works out to about 400 quintillion. That's four followed by 20 zeros. That's roughly how many moving parts are in your body. I spend a lot of my life wondering about how this extraordinary complexity arose. How did it get to BDEF? What we see with our own cells, they are nanomachines, nanomotors very often,

with extraordinary precision and speed. They are beautifully honed pieces of nanoengineering. Are they ever? A cell is a power plant, an information processor, a protein factory, a shipping and receiving bay, and a branch office in a breathtakingly complex network of cells. And it's aware of what else is going on in the body and it takes action, like seriously decisive action. So does it not seem like it's doing all of this on purpose? It's almost impossible not to see life as purposeful. And that is something of an illusion. The whole point about natural selection is it can't see the future and it can't evolve towards some end point that it can't see.

And so why does life seem so purposive when really it can't be if natural selection is correct and there's no real suggestion that it's not correct? Well, the answer is really that if cells are growing and dividing and contain information inside them and that information is constantly changing, then the cells that grow and divide best and fastest are the ones that end up leaving more copies of themselves. And so it really goes back to Darwin. It's a very, very simple idea. And a lot of people don't like the idea almost because it's so simple.

They don't believe it has the power that it actually does have. It has astonishing power to create and invent new forms of life, the whole world around us. And this look, this very strong look that everything has a purpose. Here's a paradox. The moment that you start to think about your life, your living body, and the closer you look at the tiniest, most fundamental parts of all this orchestration, the more miraculous it feels. And yet, the more mundane it feels too.

Because the closer you look, the more you see that it's just the basic laws of chemistry and physics in action. It's really thermodynamics. It's really about what are the molecules that are going to react and why do they react in the way they do. It's just chemistry. But what you get is a network of reactions. And so the metabolism that happens in bacterial cells and in our own cells, it is just favored chemically and it just happens.

If the essence of life is biochemistry, then let's get into it even deeper. Let's go down another level. Let's shrink ourselves from a molecule down to the size of an atom. So when you look at these things, they're not going to be static. Susie Sheehy is a physicist at the University of Melbourne and the author of The Matter of Everything. Even inside a solid, molecules and atoms are vibrating, moving from side to side, jiggling around all over the place. So if you existed somehow on the same scale of them and looked around you,

it's like a, you know, wild three-dimensional rave, right? Even in a solid, this happens, but especially in liquids and gases, there's a lot of movement. I think we get this idea in a complex molecule like the ones that make up life get this idea in a complex molecule like the ones that make up life that would be looking at a kind of chain of billiard balls almost right but atoms aren't spheres really they're mostly consisting of empty space so the sort of very outer part of them which is sort of the electrons around the outside they're at this sort of scale of the distance between the atoms and the molecules. But right at the very heart of each atom is the

nucleus. And that's 10,000 times smaller than the outer radius of the atom. That doesn't even make sense, does it? The radius of an atom is 10,000 times bigger than the nucleus, the meat of the atom, and nothing in between? So if you look at each individual atom and you imagine that the atom itself is the size of a cathedral. So the electrons are near the size of a cathedral. So the electrons are near the walls of the cathedral and then you try and find the nucleus. You have to zoom right in to the centre of the cathedral where the nucleus itself, which composes more than 99.5%

of the mass of the atom. That's the size of a fly at the centre of a cathedral and everything in between is centre of a cathedral. And everything in between is kind of empty space. If we look at the actual amount of matter inside an atom, and if I took all the matter from every single person on Earth and smooshed it all together, it would take up a space no larger than a sugar cube. Let's get this straight. If you removed the empty space from every atom in every living human being,

and you scrunched together all the matter that's left over, it would be about the size of a sugar cube. Eight billion people. And no, I'm not going to try to figure out how many cells that is, but the point is, all the actual matter in eight billion people adds up to just about one cubic centimeter. It is a bizarre thought, isn't it,

that we're mostly composed of empty space. I'm sitting here talking to you and I'm sitting in a chair, right? But I'm not actually touching the chair, even though it feels for all intents and purposes like I am. Technically, I'm sort of hovering just above the chair with the electrons in my body repelling the electrons in the surface of the chair. chair with the electrons in my body repelling the electrons in the surface of the chair. And in fact, we're never actually touching anything, even each other, even ourselves. Another paradox. Electrons, the things that make us feel solid and real, aren't actually solid at all. When we think about the electrons around the atom, a lot of us have this picture in our heads of the electrons kind of whizzing around like a solar system kind of model.

But when we're down on this tiny scale and these tiny things that compose our universe, actually something like an electron, it no longer behaves just like a particle. Around an atom, the electrons kind of behave mostly like a wave that's almost wrapped around the nucleus of the atom. And so if I'm standing there in this cathedral of an atom, the walls aren't even solid anymore, right? It's almost like I'm standing in water and there's waves in this water and I'm within that wave and this wave around the nucleus

is the electron. Which means that not only are we composed of mostly nothing but some of our something is actually mostly waves but there's still the nucleus so there's at least something stable and solid to us even if it only amounts to one eight billionth of a sugar cube it is kind of a lump it's a very tightly held lump but there are still vibrations there's rotations it's still going to be moving around in fact if anything in, anything in the atom or the nucleus was still, it wouldn't exist. Because to exist, it has to have energy. And if it has energy, then it's moving, fundamentally. The nucleus is held together mostly by the strong

nuclear force. And near the surface of this tiny nucleus, that force is about 100 times near the surface of this tiny nucleus, that force is about 100 times stronger than the electromagnetic force. And at this scale, gravity is so incredibly weak. So that's, hang on, let me think. It's 100 trillion trillion, gravity is 100 trillion trillion times weaker than the force that holds the nucleus together. You don't want to know how many zeros that is, but you may want to know about what the nucleus is actually made of. Inside this nucleus, there are three main particles called quarks that are really, really tightly bound together. The protons and neutrons in the nucleus are made of those quarks. A quark we define as something called a point particle, and we call the electron a point particle as well, as opposed to constituent particles. So a proton has constituents inside it. As far as we know, the quarks are fundamental,

and that's why we call them a point particle. That means that that particle doesn't appear to have any physical dimension. And yet I zoom out to the scale of even me and it seems so solid. I've always been fascinated by this idea of, well, what is actually real? Well, it's just mind-boggling because the answer is there's not much there at all and yet the illusion is so so strong to us on our physical scale and it's almost like we have to operate on this size scale because if we operated at that tiny quantum mechanical scale i think our brains wouldn't be able to comprehend the universe around us so when we zoom in to the smallest bits of the atom, right down to the very essence of our physical bodies,

we find point particles, which have no physical dimension. I think where it gets really interesting with that is to even ask, is that what's real? Is these point particles and the forces between them? The full theory that I'm talking about, this standard model of particle physics, is actually based on what are called quantum fields. So now instead of thinking about these point particles and electrons or thinking about them as waves. You have to think instead about our entire universe

being filled with an electron field, which means that somehow there's vibrations in this field and we call those the electrons. We're made of cells, and those cells are teeming with astonishing amounts of stuff and activity. And it all looks and feels real. But all of it, all of us, could really just be the creation of vibrations in a field.

Whatever that actually is. Then there's the question, are the fields real? Even though they're not smaller, because they pervade the entire universe, technically they're huge, right? pervade the entire universe technically they're huge right but are the fields the real smallest thing that we're looking for when we zoom in and to a physicist that's where you come to this point of well if the field carries energy that's how we define other things as sort of being real And it turns out that there's at least three experiments that show

that these quantum fields do carry energy. And so that is a strong argument to say that perhaps the most fundamental thing when we get down to the very, very, very smallest scale is actually something the size of the universe. of the universe. Here's yet another paradox. We contain multitudes. So many cells, proteins, nanomachines,

chemical reactions. The closer you look, there's so much more to see. And if you look really, really closely, there's so much more to see. And if you look really, really closely, there's almost nothing to see. Living bodies are the most complex and sophisticated things nature has ever engineered. And they're mostly empty space. So perhaps there's not that much that separates us living beings from nothingness

i'm always coming back to that question physics and especially quantum mechanics and these counterintuitive ways that our world actually goes together is just a source for me of creativity. It's a source of wonder and a source of awe. It's an extraordinary thing to start with a dead, wet, rocky planet. And it could be tens of billions of these in the Milky Way alone. But intellectually, we can get our heads around how a sterile, wet, rocky, inorganic planet can give rise to a living planet. Well, Carl Sagan used to say that we are all star stuff. Every single atom in every single one of us

and everything on all around us was forged in stars that blew up and used up all their hydrogen and spread these elements all over the universe. So we're all aggregates of atoms that crossed a line from being merely active chemicals to being functional life. So we're all, every one of us, made of atoms from exploded stars. Atoms that combine to form molecules

that behave according to the laws of chemistry. So, are we creations of chance? Just things that came about from biochemistry doing its thing for billions of years. I mean, we've been marveling at the stupendous kinetic pageant of how life happens, but we keep hearing that there are natural and simple explanations for it. Weird, maybe, but simple. Why are we here? Where did we come from? if the answer to those questions

is biochemistry and quantum physics does it feel deflating why have chemical reactions resulted in the dreaming, yearning desiring to expand self that is you perhaps it can make our life feel even more miraculous, more profound, and every one of us even more precious. It beggars belief, really. It's an extraordinary

thing that can emerge just through the processes of nature and physics and chemistry. And to my mind, it's far more rich than any creation myth, the logic that underpins it. And the fact that the human mind is capable of grasping even a measure of it are wonderful things and very humbling. I remember talking to a friend of the family, and she was like, oh, you know, this evolution stuff. I can't imagine anybody believing in evolution because it takes all the wonder out of the world. And I have always puzzled about that because to me, and some are selected and some die, lead to

the diversity of what we see on this planet? Just makes it more amazing because we actually understand the process of it. That continual process of going from bursting suns to human consciousness is a source of wonder for me. I'm sure that there's a lot of different ways to describe that from religiosity to spirituality to just awe, but it is awesome. When you look at all the way that these particles and forces and the very specifically fine-tuned numbers that we have in all of these theories that produce the wonderful complexity around us it couldn't be any other way because if those numbers around the strengths of the

different forces in our universe were out by even one part in a billion literally nothing would exist as we know it the universe would be be completely different. So on the one hand, for us to exist requires our universe to be exactly, exactly as it is. But on the other hand, it just seems so unlikely that it all fits together in the way that it does to produce sentient beings on this earth. And the fact that that is all being produced in the same physical system just absolutely blows my mind. This episode was produced by Ideas contributor Aaron Collier and Ideas producer Chris Wadskow. All the music and sound was composed and recorded contributor Aaron Collier and Ideas producer Chris Wadzkow.

All the music and sound was composed and recorded by Aaron Collier. Thanks to Simon and Schuster for the use of passages from the audiobook of Song of the Cell by Siddhartha Mukherjee, read by Dennis Boutsikaris. And special thanks to... Sarah Otto, my nickname is Sally. Professor Nick Lane. Dr. Susie Sheehy.

David Balinski. You can find links to them and their work on our website, cbc.ca slash ideas. Technical production, Danielle Duval. Our web producer is Lisa Ayuso. Acting senior producer, Lisa Godfrey. Greg Kelly is the executive producer of Ideas, and I'm Nala Ayyad. Thank you.