Chapter Content
Okay, so, like, when Einstein and Hubble were, you know, figuring out the universe on a *massive* scale, other people were trying to understand, like, the opposite – something super small and mysterious: the atom.
You know, like, Richard Feynman, this really great physicist from Caltech, he once said, and I'm paraphrasing a little, but if you had to boil down all of science into one sentence, it would be: "Everything is made of atoms." And it's true! Atoms are everywhere, they *are* everything. You look around, you see atoms. The walls, the desk, your sofa – all atoms. Even the air is atoms. And there are just, like, *so* many of them, it's kind of mind-boggling.
Now, the basic way atoms work is in molecules. A molecule is, like, two or more atoms working together in a stable way. So, you know, one oxygen atom and two hydrogen atoms? That's a water molecule. Chemists, they usually think in terms of molecules rather than individual atoms, it's like how writers think in words instead of letters, right? So they're counting molecules. And the number of molecules is, well, huge. At sea level and zero degrees Celsius, one cubic centimeter of air – that's about the size of a sugar cube – contains something like 45 *quadrillion* molecules. And, like, *every* cubic centimeter around you has that many. So think about the world outside your window, all those cubic centimeters, all those sugar cubes to fill up your vision. And then think about how many of those "visions" make up the universe. Basically, there are a lot of atoms, you know?
Atoms are also unbelievably old. Because they're so old, they kind of wander around. Each atom in your body has probably been through several stars, been part of millions of different organisms, before eventually becoming *you*. We all have a huge number of atoms in us, and they're really resilient, so they get reused after we die. A good chunk of the atoms in us, like, some people estimate that we each have up to a billion atoms that were probably once part of Shakespeare. And a billion from Buddha, Genghis Khan, Beethoven… you get the picture. And it has to be historical figures, because it takes atoms a few decades to totally redistribute themselves. So no Elvis atoms in you, sorry!
So, we're all, like, reincarnations, but short-lived ones. When we die, our atoms, well they scatter and find new purposes, become part of a leaf, or someone else's body, or a dewdrop.
And the atoms themselves? They're basically going to live forever. I mean, nobody *really* knows how long an atom lasts, but, according to Martin Rees, it’s something like 10 to the power of 35 years! That's a *big* number.
And they're small! Really, *really* small. Like, if you lined up half a million atoms, you still wouldn’t be able to hide a human hair. To get an idea of how small they are, well, let's try this:
Start with one millimeter. That's like, this tiny line: -. Now, imagine you split that line into 1000 equal parts. Each part is a micrometer. That's the size of microorganisms. A paramecium, you know, the single-celled thingy? It’s about 2 micrometers wide. Tiny! If you wanted to see a paramecium swimming in a drop of water with your naked eye, you'd have to magnify that drop of water to be 12 meters wide. But to see an atom in the *same* drop? You'd have to magnify that drop to be 24 *kilometers* wide!
So, atoms exist on a whole different tiny scale. To understand it, you have to take something the size of a micrometer and cut it into 10,000 even smaller pieces. That's the size of an atom: one ten-millionth of a millimeter. Which is, like, beyond comprehension. But just remember that an atom is to that one-millimeter line what a piece of paper is to the Empire State Building.
Of course, the reason atoms are so useful is because there are so many of them, and they last so long, but they were hard to discover because they were so small. And the person who first figured out that atoms have these three traits – smallness, abundance, and basically indestructible – and that everything is made of them, wasn't, like, Antoine-Laurent Lavoisier, or Henry Cavendish, or Humphrey Davy. It was this amateur, not-super-well-educated British Quaker named John Dalton.
Dalton came from the Lake District, not far from Cockermouth. He was born in 1766 to a poor Quaker weaving family. He was a bright student; so bright that he became the headmaster of the local Quaker school at the ripe old age of twelve. Now, that might say something about Dalton's smarts, or it might say something about that school. We know from his diaries that around this time, he was reading Newton's *Principia*, in Latin and stuff. At fifteen, he kept headmastering, and got another job in nearby Kendal. Then, 10 years later, he moved to Manchester, where he pretty much stayed for the last 50 years of his life. In Manchester, he became a total intellectual whirlwind, publishing books and papers on everything from meteorology to grammar. He was also colorblind. He was actually so famous for it, they called colorblindness Daltonism for a while, because of his research. But it was a thick book published in 1808 called "A New System of Chemical Philosophy" that *really* made him famous.
In one short chapter, only four pages long, the academics were first introduced to the modern concept of the atom. Dalton's idea was simple: at the base of everything are tiny, irreducible particles. "You might as well attempt to introduce a new planet into the solar system, or annihilate one already in existence, as to create or destroy a particle of hydrogen."
Neither the concept of atoms, nor the *word* atom itself was new. The ancient Greeks invented both. Dalton's contribution was that he considered the relative sizes and properties of these atoms, and how they combined.
He knew, for example, that hydrogen was the lightest element, so he gave it an atomic weight of 1. He also thought that water was made up of seven parts oxygen and one part hydrogen, so he gave oxygen an atomic weight of 7. This is how he could derive the relative weights of the known elements. He wasn't always spot-on - oxygen actually has an atomic weight of 16, not 7 - but the principle was sound, and became the basis for all of modern chemistry and, like, a lot of other sciences.
This achievement made Dalton famous, even if it was in a really understated, British Quaker kind of way. A French chemist came to Manchester to meet the atomic hero. He assumed Dalton would be at some big institution. So he was shocked when he found Dalton teaching basic arithmetic to kids in a small school in a side alley.
Apparently, the French chemist was, like, flustered when he saw Dalton, and stammered, “Is this Mr. Dalton?” because he couldn't believe this famous scientist was teaching young children addition and subtraction. And the Quaker just said, "It is. Be seated, and when I have taught these children their sums, I shall be at thy service."
Even though Dalton tried to avoid all honors, he reluctantly became a member of the Royal Society, got a bunch of medals, and received a pretty good government pension. When he died in 1844, 40,000 people came out to view his coffin. There was a funeral procession that was over 3 kilometers long!
For about a century after Dalton’s idea, it was still only a hypothesis. Some prominent scientists, like the Austrian physicist Ernst Mach, who the speed of sound is named after, even doubted if atoms existed at all. "Atoms cannot be seen...they are things of thought," he wrote.
And, like, this skepticism towards atoms was a thing. It’s been said that this doubt contributed to the suicide of the great theoretical physicist Ludwig Boltzmann, who was a big supporter of atoms.
It was Einstein who, in that paper about Brownian motion, finally offered concrete evidence of the existence of atoms, but it didn't get that much attention. Anyways, Einstein got busy with general relativity. So the first real hero of the atomic age? It was Ernest Rutherford, whether he was the first one or not.
Rutherford was born in 1871 in New Zealand. His parents moved from Scotland to New Zealand to grow flax, which is wild, and raise a big family, according to Stephen Weinberg. He grew up in a remote place that felt far from the mainstream of science. But in 1895, he got a scholarship to go to Cambridge University's Cavendish Laboratory. It was, like, *the* place to be for physics.
You know, physicists kind of look down on other scientists. When Wolfgang Pauli's wife left him for a chemist, he was shocked. "Had she gone off with a bullfighter, I would have understood," he said to a friend, "but a chemist..."
Rutherford understood that feeling. "All science is either physics or stamp collecting," he supposedly said once. It's kind of ironic then, that he won the Nobel *Prize* in Chemistry in 1908.
Rutherford was a lucky guy. He was lucky to be a genius, but also lucky to live during a time when physics and chemistry were both exciting *and* feuding. Those two sciences would never be as closely linked again.
Even though he achieved so much, he wasn't particularly brainy. Like, he was actually bad at math. During lectures, he'd get his equations all jumbled and have to stop and let the students figure it out for themselves. He wasn't especially skilled with experiments either. He just had a ton of perseverance, and an open mind. He traded brains for shrewdness, and a bit of audacity. According to a biographer, his mind "roamed uninhibitedly further than most people's." When faced with a tough problem, he was willing to try harder, spend more time, and was more open to unconventional explanations. Because he was willing to sit in front of a fluorescent screen and count the scintillations of alpha particles for hours, work that was usually assigned to someone else, he made his biggest breakthroughs. He was one of the first people, maybe *the* first, to realize that the energy inherent in the atom could be used to build bombs that could "cause this old world to disappear in smoke."
He was a big guy. Big and stout with a voice that would startle shy people. Once, a colleague learned that Rutherford was about to give a radio address across the Atlantic and said, "Why bother with radio?" He was also really confident, and kept a good attitude. When someone told him that he always seemed to be riding on the crest of a wave, he replied, "Well, I made the wave, didn't I?"
He left the Cavendish Laboratory in 1895. In the future, his waistline would get bigger, and his reputation would get louder. The same year that Rutherford arrived, Wilhelm Roentgen discovered X-rays. The next year, Henri Becquerel discovered radioactivity. The Cavendish Laboratory was about to go on a pretty incredible run. In 1897, J.J. Thomson and his colleagues would discover the electron. In 1911, C.T.R. Wilson would create the first particle detector there. In 1932, James Chadwick would discover the neutron there. In the distant future, in 1953, James Watson and Francis Crick would discover the structure of DNA at the Cavendish.
At first, Rutherford studied radio waves, and had some success. He successfully sent a clear signal over a kilometer, which was pretty good for the time. But he gave it up when a senior colleague told him that radio didn't have much of a future. Rutherford's career wasn't really taking off at the Cavendish, so he accepted a position at McGill University in Montreal, which put him on the long road to success. By the time he won the Nobel Prize, he had moved to the University of Manchester. It was there that he made the biggest discoveries, determining the structure and properties of the atom.
By the early 20th century, people knew that atoms were made up of parts, thanks to Thomson and the discovery of the electron, but they didn't know how many parts, how they fit together, or what shape they were. Some physicists thought that atoms might be cubic, because cubes can be packed together neatly without wasting any space. But the more common view was that the atom was more like a plum pudding: a solid mass with a positive charge, scattered with negatively charged electrons.
In 1910, Rutherford and his student Hans Geiger, who later invented the radiation detector that's named after him, fired ionized helium atoms, also called alpha particles, at a thin sheet of gold foil. To Rutherford's shock, some of the particles bounced back! He said it was like firing a 15-inch shell at a piece of tissue paper, and it bounced back and hit him in the knee. This just wasn't supposed to happen. After thinking about it, he figured that the particles that bounced back must have hit something small and dense inside the atom, while other particles just passed right through. Rutherford realized that the inside of the atom was mostly empty space, with a dense nucleus in the middle. It was pretty shocking. But then came a problem: according to the laws of physics, the atom shouldn’t exist at all.
Let’s stop here, and review the atom structure, as we know it. Every atom is made up of three basic particles: positively charged protons, negatively charged electrons, and neutral neutrons. The protons and neutrons are inside the nucleus. The electrons orbit around it. The number of protons determine the chemical properties. An atom with one proton is hydrogen, two protons is helium, three is lithium, and so on. Each time you add a proton, you get a new element. Neutrons don't affect identity, but they do add mass. Generally, neutrons are roughly equal to protons, but it can be a little more or less.
Neutrons and protons occupy the nucleus, which is tiny - only a quadrillionth of the total atom volume. But the nucleus is incredibly dense, and it makes up all the atom. If you magnified the atom to the size of a cathedral, the nucleus would only be about the size of a fly, but the fly would weigh thousands of times more than the cathedral. So the big and shocking amount of space that Rutherford was pondering about in 1910.
The idea that atoms are mostly empty space, and that what we see around us is an illusion, it’s still mindblowing. When two objects touch in the real world, like billiards, they're not actually touching. It's the negative charge fields of the two balls repelling each other. If there were no charges, they could pass through each other like galaxies. You're not really sitting on a chair, but floating above it at one angstrom, with your electrons repelling its electrons, unable to get any closer.
Almost everyone has this picture of the atom: one or two electrons whizzing around the nucleus, like planets around the sun. It was made up in 1904 by a Japanese physicist named Hantaro Nagaoka, who totally made it up. It's completely wrong, but somehow it persists. It’s like Isaac Asimov pointed out, it gave generations of sci-fi writers the idea of worlds within worlds, atoms becoming inhabited solar systems, and our solar system becoming a speck in a much larger system.
Rutherford's discovery led to some big questions. In particular, why wouldn't electrons that are spinning around a nucleus crash into it? According to old theories, the electrons would rapidly lose energy and spiral into the nucleus, which would be bad.
As physicists went deeper into the subatomic world, they realized that it was not only different from anything we're familiar with, but also different from anything we can even *imagine*. It seems strange, but in 1910, it was all brand new.
One of the people working with Rutherford was a friendly young Danish man named Niels Bohr. In 1913, he had an amazing thought about atomic structure. He postponed his honeymoon to write a paper that would change the world.
Physicists couldn’t see atoms, so they had to try to figure out their structure by how they acted under conditions. It's not surprising, then, that the results of those experiments were confusing. One long-standing problem was related to the spectral readings of hydrogen wavelengths. These readings showed that hydrogen atoms released energy at some wavelengths, but not others. It's as if someone was being watched and kept showing up at certain places, but you never saw how they got from one place to the other. No one knew why.
While he was thinking about this question, Bohr suddenly figured out the answer, and quickly wrote his famous paper. The paper was called "On the Constitution of Atoms and Molecules", and it argued that electrons could only exist in very specific orbits, and could not crash into the nucleus. According to this new theory, an electron moving between two orbits would disappear from one orbit and immediately appear in another, without traveling through the space in between. This, of course, was extremely weird. It explained not only why electrons wouldn’t spiral into the nucleus, but also why hydrogen's wavelengths were so confusing. Electrons only appear in certain orbits because they can only exist in those orbits. Bohr won the Nobel Prize in Physics in 1922.
Meanwhile, Rutherford had gone back to Cambridge, taking J.J. Thomson’s spot as the head of the Cavendish Laboratory. He proposed a model for how nuclei don’t explode. He thought that the positive charge of the protons had to be canceled out by some sort of neutral particle, which he called the neutron. It was simple, but not easy to prove. Rutherford’s colleague, James Chadwick, spent 11 years looking for the neutron. He found it in 1932. He also won the Nobel Prize in Physics. As Boorse and his colleagues pointed out in their history of physics, it may have been a good thing that the neutron wasn’t found sooner, because the neutron was key to developing the atomic bomb. If the neutron had been isolated in the 1920s, the atomic bomb could have been created in Europe first, undoubtedly by the Germans.
Europeans were busy trying to understand the electron’s weird behavior. The main problem that they faced was that the electron sometimes acted like a particle, but sometimes acted like a wave. It nearly drove physicists crazy. Physicists all over Europe spent the next decade thinking, scribbling, and coming up with contradictory hypotheses.
In France, Louis-Victor de Broglie discovered that some of the anomalies disappeared if the electron was treated as a wave. This caught the attention of Austrian physicist Erwin Schrodinger. He refined that discovery, and came up with an easy-to-understand theory called wave mechanics. At the same time, German physicist Werner Heisenberg came up with an opposing theory called matrix mechanics. That theory used complex math that nobody could really understand, including Heisenberg.
As a result, physics had two theories that were based on opposing arguments, but came to the same conclusions. It was crazy.
In 1926, Heisenberg came up with a brilliant solution, and proposed a new theory that was later called quantum mechanics. At the center of this theory was the Heisenberg uncertainty principle. It argued that an electron is a particle, but it's a particle that can be described using waves. The Uncertainty Principle, which laid the groundwork for this theory, said that we could know the path that an electron follows through space, or its location at a certain time, but we couldn’t know both. Any attempt to determine either will inevitably disturb the other. It’s not a matter of needing better tools. It’s an inherent characteristic of the universe.
The real meaning is that you can't ever predict the position of an electron at any specific moment. You can only suggest that it *might* be there. In a way, as Dennis Overbye puts it, an electron doesn't really exist until it's observed. In other words, before an electron is observed, it has to be treated as being "everywhere and nowhere."
If that makes your head spin, don't worry. It confused physicists too. Overbye said, "Bohr once said that anyone who wasn't shocked when they first heard quantum theory, didn't understand it." When Heisenberg was asked if he could picture what an atom looked like, he replied, "Don't even try."
So, it turns out that atoms aren't really how most people picture them. Electrons don’t spin around the nucleus like planets orbit the sun. Instead, they're like clouds without a fixed shape. The atom’s “shell” isn’t a rigid skin, but rather the outermost layer of this fuzzy cloud of electrons. In essence, the cloud itself is just a range of statistical probability that says electrons barely go outside that range. So, atoms are more like fuzzy tennis balls, not hard metal spheres. And they don’t look like anything you've ever seen. After all, we're discussing a world that's very different from what we're used to.
It seemed that one strange thing kept following another. As James Trefil said, scientists had encountered "a region of the universe that our brains are not structured to understand." Or, like Feynman said, "Things on a very small scale behave like nothing that you have any direct experience about." As they dove deeper, physicists realized that they had found a world where electrons could jump from one orbit to another without passing through the space in between, where matter appeared from nothing and then disappeared just as quickly.
One of the most incredible things about quantum theory was the concept put forward by Wolfgang Pauli in his 1925 Exclusion Principle: certain pairs of subatomic particles, even if they were separated by a great distance, would "know" about each other instantly. One characteristic of a particle is called spin. According to quantum theory, once you determine the spin of one particle, that sister particle immediately starts to spin in the opposite direction at the same speed, no matter how far away it is.
It's like having two identical billiard balls, one in Ohio and one in Fiji. When you spin one, the other spins the other way at the same speed. This was confirmed in 1997, when physicists in Geneva sent two photons in opposite directions to a distance of 11 kilometers. The results showed that as soon as one was disrupted, the other one reacted right away.
Things got to a point where, at a conference, Bohr said that the question about a new theory wasn’t whether it was crazy, but whether it was crazy *enough*. To show just how hard the quantum world was to understand, Schrodinger put forth a thought experiment. Suppose a cat is put inside a box with a radioactive substance and a bottle of hydrocyanic acid. If the particle decays within one hour, it will set off a mechanism that will break the bottle, and the cat will be poisoned. Otherwise, the cat will live. But we don't know which will happen, so we can't decide scientifically. Instead, we have to assume that the cat is 100% alive, and 100% dead, at the same time.
Because of so many oddities, many physicists didn't like quantum theory, especially Einstein. That’s ironic, because he convincingly argued in 1905 that photons could sometimes act like particles and sometimes act like waves. “Quantum theory is worth a great deal,” he acknowledged politely, but didn’t like it. “God does not play dice.”
Einstein couldn’t tolerate the idea that God created a universe with some things that could never be known. Also, the idea of action at a distance, that one particle could immediately affect another particle trillions of miles away, totally went against special relativity. Nothing can exceed the speed of light, but physicists were saying that at the subatomic level, information can somehow do that.
The biggest problem was that quantum physics was a deviation in physics. All of a sudden, you needed two sets of laws to explain the universe, quantum theory for the small world, and relativity for the big universe out there. Relativity does a great job of explaining why planets orbit the sun, and why galaxies bunch together, but it doesn’t work on a particle level. To explain what holds atoms together, you need other forces. Two forces were found in the 1930s: the strong nuclear force, and the weak nuclear force. The strong nuclear force holds atoms together. The weak nuclear force does many things, but mostly it controls the rates of some radioactive decay.
The weak nuclear force is one hundred quadrillion times stronger than gravity. The strong nuclear force is even stronger, much stronger, but its influence only goes to very small distances. It’s why the nucleus is so small and dense, and why elements with nuclei are often unstable. The strong nuclear force can’t hold onto all the protons.
As a result, physics ended up with two sets of rules, one for the small world, and one for the big universe, each minding their own business. Einstein didn’t like this. For the rest of his life, he looked for a grand unified theory to tie up those loose ends, but he always failed. He sometimes thought he found it, but it didn’t work out. Over time, he became less respected, and maybe even pitied.
Significant progress was being made elsewhere. By the 1940s, scientists had gotten to a point where they understood atoms at a very deep level. In August 1945, they gave the most persuasive evidence of that: two atomic bombs dropped on Japan.
By then, scientists had reason to believe they would soon conquer the atom. Actually, everything related to particle physics was about to become much more complex. But before we continue that story, we should recap another story, an important tale of greed, deception, pseudoscience, unnecessary deaths, and, ultimately, the definitive determination of the age of the earth.