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I love connections. To me, they are what learning and understanding are all about. Plus they’re really cool. For instance, yesterday I learned something cool and amazing about fish and swim bladders.

OK, a little background. I was reading something about discrepant events – you know, those science demonstrations that make you go, whoa! I believe they are the key to creating disequilibrium in learners’ minds, forcing them to accommodate their world views . . . I’m losing you, aren’t I?

Anyway, while reading a list of discrepant events to discuss with learners, I came across one item that struck me as just wrong. The author was claiming that a fish’s swim bladder is a discrepant event. Most learners will think that a fish adds air to its swim bladder in order to float higher. In fact, claims the author, just the opposite is true. The fish expels air to swim higher, because the vacuum created has less mass than the air. This struck me as almost certainly wrong, so I did some research.

Sure enough, the author was mistaken. Fish do add air to the swim bladders to increase their buoyancy. But . . . how?

Think about it for a moment and it’s a great puzzle. Fish can’t have had that air inside them to begin with (unless it was compressed, and I couldn’t see how a fish could be holding compressed air in). Do they “breathe” in a bunch of air very quickly to rise? This seems impractical, as often fish need to change their buoyancy quite quickly. So what do they do? We’ll come back to it.

Have you ever been exercising and felt that painful burning in your muscles? That good ache that lets you know you’re working hard? That pain is from lactic acid. When you exercise, your muscles burn lots of glucose by combining it with oxygen, thereby releasing its stored-up energy (energy that came from the Sun via photosynthesis of the plant that made the glucose, but that’s another connection story). However, if you run low on oxygen, your muscles start to convert glucose to lactic acid. This releases energy, too, but not as efficiently as the glucose plus oxygen reaction. And the side-effect is that the lactic acid starts to make your muscles ache as it turns the tissue acidic.

Fortunately, your body has a built-in defense mechanism against lactic acid damage. When tissue starts to turn acidic, the blood feeding that tissue becomes acidic, too. And when blood becomes more acidic, hemoglobin (red blood cells) start to release more dissolved oxygen. Oxygen, of course, is exactly what your muscles are screaming for, and so everyone is happy again.

Fish, with whom we share a common ancestor (we are, in fact, highly-modified, bicycle-riding fish – apologies to Gloria Steinem), have this same physiological response, but in fish the response is even stronger. Fish blood is extremely sensitive to changes in pH, so that a little lactic acid can cause a large release of oxygen. And fish use this response in an amazing way.

Lining the fish’s swim bladder are cells that are specially adapted to produce lactic acid. When they do, instantly the blood near these cells dumps lots and lots of dissolved oxygen. Much of that oxygen goes into the bladder as gas, and that gas makes the swim bladder expand. The fish carefully controls the amount of gas going into and out of the swim bladder so that as a whole the fish remains neutrally buoyant in the water. Lactic acid as a buoyancy control! Amazing!

But it gets even better. Why do we produce lactic acid at all? Because we all evolved from bacteria that used this method to eat! Before there was much free oxygen in the atmosphere (which, after all, came from plants), all the creatures on the Earth used this non-oxygen (anaerobic) method of eating. Many bacteria still do, of course, and they can be found anywhere food is abundant but oxygen is not. It was only when the plants “poisoned” the atmosphere with this volatile, fire-supporting waste gas that evolution found the more efficient pathway of burning glucose with oxygen to release energy. We might get annoyed at this scar of evolution every time our muscles start to ache, but for fish, it’s the very scar that keeps them afloat!

And that, dear readers, is what makes life cool.

I have a confession to make. I don’t know squat about nuclear power.

I don’t know if nuclear fission is really safe, if we can deal with nuclear waste in a responsible way, if nuclear fusion can ever be made viable in anything by a hydrogen bomb.

And yet I’m a huge advocate of nuclear power. Why? Because I think it’s freakin’ cool. I think it would be so cool if our society ends up running on the power of atoms first formed in exploded stars from billions of years ago. I think it would be amazing if the power of those same stars were harnessed here on Earth. Every kid learning about our power grid would in turn find out about the secrets of atoms and stars, and the world would be a better place.

I’m also a huge fan of space travel. I am a child of Apollo, born in the late sixties. Some of my earliest memories are watching astronauts on live TV from the Moon. There was a book in my kindergarten classroom that I’ll never forget, a picture book all about Apollo 11, this tiny, spidery lander heading toward a barren landscape, while the faraway white capsule circled overhead. I remember Michael Collins going on Mr. Rogers to talk about why he had to stay behind while his friends walked on the Moon.

I remember putting on my winter coat in the middle of the summer, because I thought it looked like a spacesuit, and pretending to land and walk on the Moon. And I remember eating Push-Ups (best ice cream ever) and then turning the tube, plastic pushing wheel, and plastic stick into a rocketship and flying through the universe in my back yard.

So naturally, when nuclear power and space travel come together, I can’t resist it.

Remember the story of how we know that the helium here on Earth came almost entirely from nuclear decay? It’s because almost every bit of helium we have is helium-4, and helium-4 is made quite easily in alpha decay. The other isotope, helium-3, is almost completely absent from the Earth. But it’s not like that in the Sun.

The Sun makes both helium-3 and helium-4. And it fires both away from itself as part of the solar wind. Atoms of helium-3 streak from the Sun and fly all over the Solar System. Any that impact the Earth are quickly lost, as our atmosphere buffets the speeding particles, slowing them down until they finally drift off and out of the atmosphere.

But the Moon has no atmosphere. Helium-3 that smashes into the Moon has a chance to stay there, especially if it gets trapped in the loose, powdery rocks found on the Moon called regolith.

Scientists estimate that there are over one million tons of helium-3 embedded in the regolith of the Moon, compared to maybe a few hundred pounds of helium-3 to be found anywhere on Earth. So what’s the big deal?

The big deal is this. Nuclear fusion – the technology that’s twenty years away and always will be, as the saying goes – combines deuterium (hydrogen-2) and tritium (hydrogen-3) to make helium-4 and energy. But it also makes lots and lots of neutrons. Neutrons are hard to handle, carry away valuable energy, and also make the surrounding walls radioactive over time. This is nothing like the radioactivity problem of nuclear fission, but it is still a concern.

If we replace tritium with helium-3, the neutron problem disappears. Fusion between deuterium and helium-3 produces helium-4 and a proton, and that proton can be used to make electric current. Fusion with helium-3, so the scientists say, can be 70-80 percent efficient, and eliminate the need to replace radioactive container walls every few years.

So all we have to do is go to the Moon, harvest the helium-3, bring it back to Earth in huge quantities, (oh, and build a working nuclear fusion reactor), and voila! Our energy problems are solved!

Well, you’re right to be skeptical. If it sounds too good to be true, it probably is. But wouldn’t it be so cool? Imagine having the world powered not only by the process the powers the Sun and the stars, a process that requires us to understand matter on its most basic level, but if the fuel for that star-powered world came from space itself? What an incredible world that would be!

And that, my friends, brings us to the end of my story of helium. That’s one element down, only 91 more to go. Wait, didn’t they just discover element 118? Oh, well . . .

Thanks for reading!


As we’ve moved through the story of helium, I’ve found that I know a little less about each topic. We’re now on the next-to-last entry, and its a topic about which I knew close to nothing until I did some research. So if I’ve convinced you through the first ten entries in this series that I know a little about things, this entry will dissuade you of that notion. But here goes, anyway.

Liquid helium is just darn cool. Yes, it’s cold, around 4 degrees C above absolute zero (or 4 Kelvins). But it also is cool in the full of wonder sense, particularly when pure helium-4 reaches a temperature of  2.17 Kelvins. At that temperature, liquid helium-4 becomes something called a “superfluid.”

Here’s a video of what happens when liquid helium reaches 2.17 K. Yes, it’s in Greek. Somehow that makes it even cooler.

When helium-4 reaches 2.17 K and even colder, all the helium atoms in the sample act like a single atom. This explains why the boiling stops; boiling is the process of some atoms (with more energy) escaping and other atoms (with less energy) staying behind. That’s why sweating cools you off; the evaporating sweat carries away heat energy, leaving cooler liquid on your skin.

But if all the atoms in a sample of liquid helium are behaving as a single atom, then none of them can have more energy than any other. They must all have exactly the same energy, and so boiling isn’t possible! Notice in the video how the boiling stops the moment the temperature reaches 2.17 K. When that transition occurs, you are looking at what amounts to a single atom!

But why that temperature? This is the part that blows my mind. There’s this thing called the Heisenberg Uncertainty Principle. It essentially says you can’t have perfect knowledge about two related variables at the same time. In the case of these helium atoms, you can’t know both their position and their momentum. Momentum is related to speed, and speed to temperature. At a particular temperature (you guessed it, 2.17 K), we know a lot about the atoms’ momenta (because it doesn’t have much). As a result of narrowing down the momentum knowledge, our knowledge about the atoms’ positions becomes worse – bad enough that we can’t tell any two atoms apart! Quantum uncertainty means that the atoms overlap!

There’s one further detail here. Only some kinds of atoms can overlap this way. If you remember a couple of posts ago, I wrote about the idea of the Pauli Exclusion Principle, and I hinted that it didn’t always apply. Well, here’s where it doesn’t apply. The reason is number again. Helium-4, with 2 protons, 2 neutrons, and 2 electrons, has 6 particles all with half-integer spin. Big deal, right? It is a big deal, because you can’t add together 6 halves and end up with anything other than a whole. Try it! This means helium-4 always has a whole number of spin. And particles with a whole number of spin don’t obey the Pauli Exclusion Principle!

Helium-3, with only 1 neutron, won’t do what helium-4 does (ok, yes it will, but only at much, much lower temperatures, and for a reason that is thankfully “beyond the scope of this blog entry”), because helium-3 has 5 particles with half-integer spin. But helium-4, with a whole number of spin, behaves in this strange way that electrons can’t. Helium-4 atoms can all be in the same exact state. Crazy!

That might not excite you too much, but maybe this will. If this liquid helium really is, now, a single atom, then maybe it can start to do some of the weird things atoms do. For instance, atoms can interfere with themselves. One of the weirdest things about quantum mechanics is that, because atoms have a wavelength, atoms passed through double slits can create interference patterns just like light beams. Well, quantum mechanics works for atoms, but surely it doesn’t work for things as large as that sample of liquid helium in a test tube? Or does it?

Sir Anthony Leggett, at a lecture I attended a few years ago, suggested an experiment aimed at testing this idea. Once we have this superfluid, macroscopic single atom of liquid helium, let’s try to make it interfere. Do we get interference patterns? If we do, then quantum mechanics applies to the macroscopic world of cats, turtles, and you and me. If we don’t, and we can eliminate any other errors, then there must be other, “hidden” laws of nature that draw a line between microscopic quantum weirdness and the macroscopic world we live in.

As far as I know, the experiment hasn’t been done yet. But other experiments with helium-4, including things like quantized vortices in the spinning fluid and this property of near-zero viscosity, point in one direction. Macroscopic quantum effects are real. Quantum mechanics really does describe our world, not just the world of atoms, but the large world of people and peanut butter sandwiches.

Go back and look at that video again. You’re looking at a single, quantum mechanical “atom” made of billions upon billions of individual helium atoms, each of which has lost its own identity to quantum weirdness. And that is crazy cool!

So Ernest Rutherford used alpha particles, the same particles he showed were really just helium atoms in disguise, to discover the nature of all atoms. Rutherford pictured the atom as a sort of miniature solar system, with the compact and massive nucleus in the middle and electrons whizzing about in orbits like tiny planets. But scientists soon realized that Rutherford’s model was unstable.

Electrons are electrically charged, and any electrically charged body must radiate energy as it accelerates. If you’ve ever ridden the Rotor, or sat in a car as it took a sharp left, you know that circular motion is acceleration. But if electrons radiated in orbit, then every atom in the universe would collapse in a fraction of a second. Since that doesn’t happen, there must be something wrong with Rutherford’s model.


Rutherford’s student Niels Bohr found a solution, of sorts. Bohr decided that electrons weren’t like planets, which can orbit at any distance from the Sun. Instead, electrons could exist in only certain energy states, called orbitals, and moved from orbital to orbital in discreet jumps (quantum leaps), during which they would either absorb or radiate specific amounts of energy. Bohr’s model worked wonderfully well for hydrogen. But as soon as Bohr tried to apply the model to helium, the wheels fell off. With its two interacting electrons, helium proved a far tougher atom to crack.

But Bohr was on the right track. Today a theory called quantum electrodynamics (QED) explains with great precision the orbital of helium and the behavior of its pair of electrons. QED shows us that chemistry is just number. And helium’s key number, 2, makes it unique as the most standoffish of all the elements. Today we know why, and helium was the clue that showed the way.

Wolfgang Pauli wondered why chemistry worked at all. Why, Pauli wondered, didn’t all electrons fall into the lowest energy state of Bohr’s atom? After all, if you excite the electron in a hydrogen atom, it eventually falls back to the ground state, releasing light energy along the way. Why didn’t all electrons behave this way?

Wolfgang Pauli

Pauli guessed that it must be due to the other electrons in the way. And yet helium still didn’t make sense, because in helium it seemed that two electrons, not just one, existed and could fall back into that ground state. If two, why not more?

To explain this strange behavior of the helium atom, Pauli conjured an effect called the “Pauli exclusion principle” (he probably didn’t call it that right away). Essentially, Pauli saw that two identical electrons couldn’t occupy the same state – that’s what kept all atoms that aren’t helium from behaving like helium. But, Pauli said, the two electrons in helium’s ground state aren’t really in the same state. There’s one crucial difference between them. That difference was spin.

Pauli said that as long as the spins of two electrons are opposite, there is an attractive force between them (yes, even though they’re both negatively charged). If, however, the spins are the same, there is a repulsive force between them. This force (attractive or repulsive) is called a coupling force, and it happens with all particles that, like electrons, have a kind of spin called half-integral spin. None of that is particularly important. What is important is this. The Pauli exclusion principle explains that there’s not room for just one electron in the ground state. There’s room for two.

Once helium has its two electrons, it is a happy camper. The electrons form an extremely symmetric cloud around the nucleus, blocking out (“masking”) virtually all of the positive charge deep within. There’s no magnetic field produced, either, and since both kinds of electron spin are present, the coupling forces are all repulsive. This makes helium extremely non-reactive, and is why, unlike most other elements, it is always found in its simplest form – a single atom, disconnected from its own kind and from all other elements.

The Pauli exclusion principle became a crucial tool in helping scientist explain how all the other atoms in the periodic table are constructed. And, as we’ll see later, its absence for another kind of matter leads to some of the strangest behaviors we’ve encountered yet. Once again, helium lit the way.

In part seven we watched an alpha particle escape a nucleus and fly away with enormous speed. Tonight I want to go the other direction – back into that nucleus to try to discover it secrets.

This is a path taken before. We’ll be following in the footsteps of one of my all-time science heroes, New Zealand-born Ernest Rutherford.

Rutherford is one of those characters you feel that you know after reading descriptions of him. He was boisterous, loud, like an animated bowling ball, but never mean, arrogant, pompous, or a blow-hard. He was always humble yet perspicacious (it’s OK, I had to look it up, too), assiduous about always giving credit to others where it was due, a great supporter of female scientists when practically no one else was. He was supposed to have lacked math skills, but his intuition about how things worked was uncanny. He seemed, far beyond his contemporaries, to know which questions to ask.

My favorite Rutherford anecdote is this picture:

Notice the sign in Rutherford’s laboratory. It says, “Talk Softly Please.” At first you might think Rutherford is a tyrant, forcing his subordinates into quiet work. Not so. The sign was put there by Rutherford’s team, specifically because of him. The work done in the laboratory was sensitive, and Rutherford’s loud, booming voice could actually affect the results. The team put up the sign to remind Rutherford to please curb his enthusiasm. You see him in this picture, under the sign made for him, gleefully chewing on a cigar and considering some deep mystery of the universe. When I grow up, Iwant to be Ernest Rutherford.

Rutherford named both alpha and beta radiation, and he was the first to recognize the connection between alpha particles and our helium atoms. But, far from just naming alphas, Rutherford made them dance, using these atomic bullets to enter the holy of holy.

In 1911 Rutherford asked a student to do an experiment that couldn’t possibly work. Or could it? Ernst Marsden was to fire alpha particles at a gold foil sheet. Alphas were known to be very small, very fast, and positively charged. At the time of this experiment, atoms (such as the atoms making up gold) were thought to be like plum pudding. The pudding was a sort of diffuse positively charged – something – and the plums were the electrons discovered by Rutherford’s mentor JJ Thomson in 1897. Theory said that alphas should pass right through the gold foil, as in fact every experiment done up to that time had show.

But Rutherford asked for a different experiment. Instead of watching for alphas passing through the foil, Rutherford asked Marsden to watch for alphas that bounced back. This was clearly impossible – a thin, diffuse atom couldn’t possibly stop something as fast as an alpha, let alone bounce it back the other way. And yet when Marsden looked . . . yes, there they were. Not often, but often enough to be utterly baffling, alpha particles impacted the gold foil and bounced back.

Rutherford wrote about how shocked he was. “It was about as credible,” he said, “as if you had fired a 15-inch shell at a piece of tissue paper and it came back and hit you.” But I’ve always had my doubts about Rutherford’s surprise. He never seems to admit it, but I suspect that Rutherford suspected Marsden might find something, after all. If not, why look?

At any rate, whether Rutherford suspected anything or not before the experiment, there is no doubt that after the results were in Rutherford saw what they meant. The bouncing alphas showed Rutherford that the atom was not a plum pudding, but instead was almost entirely empty space. Almost all the mass and charge of the atom was concentrated in a tiny spot in the center. That spot came to be called the nucleus. My favorite comparison is that if the atom were the size of a baseball diamond, the nucleus would be a ladybug in the grass just behind the pitcher’s mound. And yet virtually all the mass that makes up the atom is found within that bug. The rest is virtually empty. We are, all of us, mostly empty space.

Anyway, this experiment shows again why quantum tunneling is so surprising. In effect, the experiment is just the opposite of quantum tunneling. Put yourself down there, at the level of an atom. An alpha is “fired” at a nucleus. It approaches, closer and closer, and gradually the positive electric charge of that nucleus becomes so large that the alpha actually bounces back, like a baseball off a trampoline. It wasn’t moving fast enough to get inside the nucleus, into that holy of holies, into that deep secret. But why?

There’s a scene in the movie Ghost that, by messing up, shows why. Of course, the rest of the movie is pristinely scientifically accurate, but in this one place they get it wrong. Near the end, the bad guy is impaled by falling glass, broken by a swinging pendulum. But the pendulum swings higher on its second swing than on its first! Anyone who’s ever done the bowling ball to the nose demonstration

knows that this can’t happen (otherwise we’d get a lot of broken noses!) For the same reason, an alpha shot out of a nucleus can’t get back in.

Remember what we learned about tunneling. The alpha particle is like the rivet that didn’t kill you. It doesn’t start right next to the nucleus, but some distance away, and as a result has a lot less energy. Therefore, just like the bowling ball or the pendulum in Ghost, it can’t get up the hill it never came down. It can’t get to the nucleus, but instead is bounced away. In the process, though, it reveals that there’s something down there, something tiny, massive, and deeply mysterious.

Still, Ernest Rutherford was able to build a universe from this discovery, a universe in which the mass and the positive charge of atoms lay deep within, while the negatively-charged electrons zipped about on the outside like planets around a massive Sun. There was only one problem with this picture. It couldn’t possiblywork.

If you’ve been reading along, and you’ve finished your PB and J, you will remember that when we last left our helium it was inside a star where it had just been born. But this newborn helium isn’t the last stop – far from it. Today we look at what happens when the helium’s hydrogen parent starts to run low.

When that occurs, the star starts to shrink. Why? Polyester.

No, that’s not it. When the hydrogen runs low, fewer gamma rays come flying out of fewer nuclear reactions. It’s the pressure created by those gamma rays that keeps the Sun from collapsing in on itself. Think how amazing that is! Imagine shining a flashlight at your chest. Just how much does the light push you? Not much, but essentially the same thing happening inside the Sun keeps the whole thing from imploding every moment.

OK, so now we have a shrinking star. As the star shrinks and compresses, the temperature inside goes up, just as a bicycle pump gets hot as it compresses air. This hotter helium starts to move faster and faster, and as it does so it slams into other helium nuclei. But nature has another trick in store.

Helium-4 contains two protons and two neutrons. Two helium-4 nuclei slammed together will give four protons and four neutrons. Try to find this nucleus on the periodic table. Go ahead, I’ll wait.

OK, you didn’t find it. That’s because any element with four protons is beryllium. Add in the four neutrons and you’ve got beryllium-8. But there’s no such thing as beryllium-8, because it falls apart as fast as it can come together. If we had to depend on helium changing into beryllium to keep stars burning, we’d soon have a very dark universe.

Since the universe isn’t dark, you’d probably guess there’s more to the story. And you’d be right. Because helium has another path, one that skips over the beryllium sinkhole. If three helium atoms come together at almost exactly the same time, they can stick. First two come together, and immediately start to move apart again. But before they can separate, a third helium nucleus comes barreling in, and a magical thing happens. Instead of three helium nuclei, we suddenly have something new, something that was never there before. With six protons and six neutrons, the new thing is called carbon-12.

If you’d like an example of carbon-12 in action, close your eyes. OK, now you can’t read, but when you open them again I’ll tell you that the insides of your eyelids are made of carbon-12. So are the outsides, but they’re a lot harder to see unless you’re really gross. Your arms, your legs, your fingers, toes, and belly button (whether you’re an innie or an outie) are all made of carbon-12. And every bit of it came from helium, cooked up inside a star experiencing a hydrogen shortage.

And yet there’s one more piece of the puzzle, a thought that takes my breath away. This process, called triple alpha (we’ll come back to that “alpha” word in a later blog entry), shouldn’t work very well at all. It should be almost impossible for three helium nuclei to hit at just the right time to form a carbon-12 nucleus. But it turns out that the nuclei don’t have to hit exactly, because of a hidden secret shared by helium and carbon. There is a radioactive form of carbon-12, called a resonance. The energy of that resonance of carbon-12 turns out to be almost exactly the same as the energy of the three helium nuclei that go into making it. And this resonance means that it’s much, much more likely that carbon-12 can form inside a star.

In fact, a scientist named Fred Hoyle predicted that the resonance of carbon-12 had to exist. How did he know? Because he knew that he was made of carb0n! The carbon had to come from the insides of stars, and the only way stars could make enough carbon to make fingers and legs and eyelids and belly buttons and brains that could think of the triple alpha process was if there was a resonance at carbon-12 with just the right energy. Scientists looked for the resonance, and there it was.

Quickly the radioactive carbon=12 fires off a gamma ray and settles down to ordinary carbon-12, and the star can live again. For a while.

Later on, when things get really bad for our helium-burning star, it will either blow off its outer layers (making what’s called a planetary nebula, here’s one now:)

or else the star will explode in a supernova, spilling its insides out all over the place. Even later, the carbon from either kind of star can drift about, settle into a collapsing cloud, and end up on a young planet, where billions of years later it might form the inside of your eyelids. All because helium got hot enough for a threesome! (sorry, couldn’t help myself)

Yesterday I wrote about how floating helium balloons lead to the idea that everything is made of atoms. Today I want to think about one particular helium atom, an atom in the outer atmosphere of the Sun.

Something strange is about to happen to this atom. As it bounces about at the edge of our star, the helium atom is surrounded by a sea of flying photons. Many photons might pass right through the helium atom, but if the photon is just the right frequency, it plashes into the helium atom and disappears. When light from the Sun reaches the Earth, it will be missing photons of just that frequency. For photons, frequency equals color. Seen through a microscope, the rainbow of light from the Sun will display a dark line where the helium atoms in the Sun’s atomosphere captured those particular photons.

Of course, not only helium creates dark lines in the Sun’s spectrum. In fact, by examining those dark lines in solar rainbows, scientists in the 1800s recognized that all the elements known on Earth present in the Sun, as well. This was an amazing discovery. For thousands of years, the greatest thinkers were convinced that the heavens must be made of different stuff than the dirty, imperfect Earth. But scientists, by examining the tiny black lines in solar rainbows, found a deep connection between the heavens and ourselves.

And yet the fit wasn’t perfect. There were extra lines in the Sun’s spectrum. These lines didn’t match any known element, and so the scientists conjured a new element, unknown on the Earth. They named it after the Greek god of the Sun, Helios the charioteer. Were, in fact, the heavens different from the Earth?

No! Decades later, a scientist named William Ramsay discovered an unknown element, a gas that was often found in association with the mysterious element uranium. When Ramsay isolated this light, non-reactive gas, he found that its spectrum matched the Sun element. Helium, as with all the other elements, wasn’t found only in the heavens, but on the Earth, as well. We and the stars were one.

Enough about religion and all that. This is supposed to be a blog about wonder. For the next twelve nights I intend to write about possibly the most wondrous of all the elements, helium. As Joseph Campbell said, “I don’t believe in being interested in a subject just because it’s said to be important. I believe in being caught by it.” Maybe by the twelfth night, helium will have caught you.

Let’s start with an obvious one. Why do helium balloons float? This simple question will take us to the brink of one of the great discoveries of science: all the world is made of atoms.

Imagine yourself holding a string tied to a helium balloon. You feel that string tugging on your fingers, begging to be released. The helium balloon wants to escape, to fly away. But this is an illusion. Helium, like all matter, is affected by gravity. The gravitational field of the Earth pulls on helium just as surely as it pulls on everything else. So whence the illusion of lift?

Gravity pulls on air, too. But air is heavier than helium, and so the air around and above the helium balloon is pulled more strongly by the Earth than is the helium. You’ve experienced the same thing if you’ve ever held a plastic ball under the surface of the water in a pool or a bathtub. The water pushes below the ball, and so the ball seems to want to rise up.

But this leads to a lovely problem. Why should helium be lighter than air? To get to that answer, we have to take a roundabout path (those are the best kind, aren’t they?) through two more elements, hydrogen and oxygen.

Suppose you take some water, add some sodium sulfate to it to make it a good conductor, and run an electric current through. It doesn’t take much power, a six-volt lantern battery will do nicely. If you do this, from the positive end of the battery you’ll get bubbles, and from the negative end you’ll get more bubbles, twice as many, in fact. Simple tests will show you that the lesser bubbles are oxygen gas, while the double bubbles (ha!) are hydrogen. And a really fun test, recombining the hydrogen and oxygen (kaboom!) will show that every bit of each element will be used up, resulting in water once again.

This suggested to scientists that 1) everything was made of tiny particles, eventually called atoms and 2) the atoms combined in simple ratios to form things like water. In fact, as of course you know, the formula for water is H2O, two H atoms for every one O atom.

But notice that the volumes of the gases work out just the way you might hope. The volume of hydrogen gas is just twice the volume of oxygen gas. This idea eventually became Avogadro’s hypothesis. Simply, it says that as long as everything else is the same, equal volumes of two different gases contain the same number of atoms (or molecules, if the gas is, like both hydrogen and oxygen, molecular).

OK, fine. That means the number of atoms inside our helium balloon are the same as the number of molecules of air in an air balloon. And yet we know from experience that helium balloons float, while air balloons do not. What gives?

The difference must be with the atoms themselves. The world is made of atoms, and those atoms have different properties. The reason helium floats, makes your voice squeak, and stubbornly resists reacting with even the most reactive of chemicals, is that helium atoms have certain specific properties. Helium balloons float because helium atoms are very, very light. Soon we’ll find out why, and that journey will take us not just to the atoms themselves, but actually inside. Stay tuned . . .

I’ve written before about Cloverfield Pond. On a recent visit there, I had an odd thought. What would happen if I just walked into the pond and sat down?

Well, the water’s probably not more than a foot or two deep, maybe three in the middle, so I’d probably still be able to breathe. But eventually, if I sat there long enough and didn’t defend myself, I’d be eaten. Nature is full of beauty and mystery and wonder, but it’s also hungry. And, not to sound egotistical, but I taste good.

What does that mean? It means that my body is chock full of low entropy stuff that other creatures crave. They can use my low-entropy ingredients to extract energy and/or build their own low-entropy bodies. Wherever there’s a resource, some creature will exploit that resource. And resource means low entropy.

But why should I be build of such tasty stuff? It’s not just me, of course. It’s you, too. It’s all of us. In order to be alive, we have to be made of low-entropy materials. That’s part of what being alive is. How’d we get that way?

Well, we ate other low-entropy individuals. Probably not other people, but certainly plants, and (if you’re like me) other animals, too (vegetarians taste better). We took those low-entropy materials, extracted the usable energy, utilized the most useful structures such as proteins, and, um, got rid of the rest. All living things are engines for extracting what they need from low-entropy materials, then returning high-entropy waste to the environment.

Plants are the crucial link, of course. They grab low-entropy sunlight and transform high-entropy materials (carbon dioxide and water vapor) into low-entropy materials (sugar). Everything else depends on their ability to do this amazing transformation trick. But notice how they do it. They capture very high-entropy sunlight and, overall, return lower-entropy ingredients to the environment.

This isn’t a criticism of plants; rocks would do much worse. A rock just absorbs low-entropy sunlight and then just radiates back much higher entropy radiation, without producing anything useful in the process.

But why, we have to ask, does sunlight have such low entropy? Because it was produced in a low-entropy environment, the Sun. There, low-entropy hydrogen is fused into higher-entropy helium, changing mass into light energy.

Let’s keep following the reductionist chain. Why is hydrogen lower entropy than helium? Because in reacting, hydrogen must fire off positrons and neutrinos, all of which carry away energy. The resulting helium atom has a mass just low enough to match the lost energy.

But where did the hydrogen come from? Hydrogen came originally from the Big Bang itself. Here, finally we reach the crucial mystery. The Big Bang began as an incredibly tiny dot of hugely low entropy (extreme high order). Ever since that event, the overall entropy of the universe has been increasing. Though, fortunately for us, overall entropy is a subtle concept.

Occasionally, gravity may pull a star together, lowering the local entropy. But because huge amounts of heat are released, the overall entropy still goes up. Even more rarely, the low-entropy light of the star may support life on a nearby world. Like stars, living things reduce their own local entropy, always at the cost of increasing the entropy of their surroundings (by, for instance, eating their neighbors, then releasing the waste).

One of those living things, me, has been increasing the entropy of his surroundings for over four decades now. But I know it can’t last forever, because I taste so good.

And so do you. The next time you go to the zoo and notice the tiger or polar bear eying you hungrily, the next time you get bitten by a mosquito or even just catch a cold, remember why these creatures are after you. You taste good because of the amazing order that existed just before the Big Bang. Yum!

Some people geek out on celebrities, rock stars, politicians. I’m much sicker than all of those people. My fall down on the sidewalk slobbering idols are particle physicists.

The current holy grail of particle physics, the Higgs boson, is (maybe) within our grasp. Perhaps even today, at a place called the Large Hadron Collider, the signature of a Higgs was captured. We won’t know for a while, but think about it: today might be the day when we finally find out why things have mass.

I started a new book today by one of those superhuman particle physicists. It’s called “The Lightness of Being” and the author is Frank Wilczek. I start a lot more books than I finish, and it’s not rare for a book that begins promisingly to end up returned to the library long before it’s done. But one passage in the early part of the book absolutely captured my imagination, and I want to share it.

“In Galileo’s time, professors of philosophy and theology – the subjects were inseparable – produced grand discourses on the nature of reality, the structure of the universe, and the way the world works, all based on sophisticated metaphysical arguments. Meanwhile, Galileo measured how fast balls roll down inclined planes. How mundane! . . . Galileo too cared about the big questions, but he realized that getting genuine answers required patience and humility before the facts.” – The Lightness of Being, pages 7-8.

One of the most beautiful ideas I can imagine is this . . . you can trace a continuous path of discovery, from Galileo and his rolling balls and inclined planes, through Newton and his laws of motion, to the great electrical investigations of Volta, Ampere, Faraday, and Maxwell, to Einstein and Planck and Curie and Bohr and Heisenberg and Meitner and Wheeler and Feynman and Gell-Mann and now to the scientists at the LHC. Maybe their equipment is a little more complicated than Galileo’s ramps and balls, but it’s still the same game. And what a game it is!

Here’s just one example of where Galileo and his intellectual descendents have taken us, while the metaphysicians keep on debating about whether there’s any such thing as knowledge or even reality. Imagine one metaphysician talking to another, about how all we know is provisional and subjective and riddled with invisible assumptions. Within her throat, her vocal cords vibrate, setting into motion nearby molecules of air. Those molecules, already in frantic motion all about, nevertheless faithfully carry the pattern of her vibration to their neighbors, who inform their neighbors, and so on as the sound of her voice spreads throughout the room.

But the air molecules themselves don’t go across the room! Instead, a wave is moving, a pulse of – what? something, energy, information – carried not by the moving molecules themselves, but by their interactions with one another.

And why do they interact? Because on their outskirts are electrons, each identical, each repelled equally by every other electron in the universe, each just trying to possess its own little bit of space. When another electron comes too near, it reacts, pushes as it is pushed, and the wave moves on.

Finally the wave reaches the ear of the second philosopher, and the molecules of his eardrum, the electrons in his own outer shells, react to the outer shells of the air molecules right up against his ear. The eardrum vibrates, duplicating in a very distinct way that vocal cord vibration that started it all. And he hears her. Sound, ultimately, is electrical!

And yet the questions remain. Why do electrons have the charge they have? Why do atoms have mass, the mass tha allows them to move in just the right reactionary way to carry a sound wave? What are mass and electric charge, anyway? The answer is, we just don’t know. But maybe, just maybe, we’re getting close.

And yet the point isn’t that the investigation ends, so far, ultimately, in mystery. The point is that we’ve broken down the problem, shown that it is really another problem, a more common, basic, fundamental problem. Many, many such investigations – how does a car work, why is water wet, and yes, even, what is life? – end in just this way. And so we’ve swept our pile of ignorance, which once covered the floors of metaphysical universities, into a much smaller, yet profoundly worthy, heap. And now, at the LHC, by rolling ever more energetic balls down ever steeper inclined planes, my heroes the particle physicists are diving into even that profound pile of mystery.

And I get to watch!

My first book, called The Turtle and the Universe, was published by Prometheus Books in July 2008. You can read about it by clicking on the link above.
My second book, Atoms and Eve, is available as an e-book at Barnes and Noble. Click the link above. You can download the free nook e-reader by clicking the link below.
December 2019
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A blog by Stephen Whitt

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