Ithaca, NY, 1948
After a wrong turn in Albuquerque, I caught up with Bugs Bunny, alias Richard Feynman, somewhere near the ends of the earth. Up to my elbows in snow-drifts, I spied on the little window to his office, in which he seemed to be doing normal professor-things, plus wild gesticulations. I decided on a particularly frozen morning that I would have to risk visibility if I was to get answers, so I enrolled at Cornell, posing as a G.I. bill student. In Professor Feynman’s introductory physics lectures, I could see that there was something remarkable happening here. People researching physics is about as natural as fish studying water: it’s the very stuff we’re made of. He had a knack of getting down to the ground floor, asking the basic questions, just as much in a block sliding down a plane as in neutrinos.
His teaching assistant, a quirky bow-tied Brit by the name of Freeman Dyson, knew the man personally, so I inquired. “Oh, he’s working on something, yes. The trouble is he just won’t publish, no matter how much I cajole him. He says he’s depressed, but Dick depressed is just a little more cheerful than any other person exuberant. It’s the Bomb, I think, and of course Arlene, his poor wife who died in New Mexico. I probably shouldn’t be telling you this, but Dick and Arlene got married knowing she hadn’t long to live, she having T.B. Bit like Dick to give it a go anyway.”
“What do you suppose he’s up to?”
“Well, he’s got his own private quantum theory for starters. Quantum theory, that’s the theory of the atom and electrons. Until recently, no one’s been able to make it work with Einstein’s relativity; it’s riddled with infinities, you know. Schwinger’s done some remarkable work reconciling the two— all operator theory and renormalization, I’m still trying to understand it. Somehow, there’s a way to replace the infinities with experimental measurements, then the beast is well behaved and gives very nice results. Dick manages calculate the same thing with these funny little pictures, and he puts plus signs between them like they were real mathematical formulae. Quite a ball at conferences: squiggle plus squiggle equals whatever. I mean to pick his brain about it before he flies off to Brazil.”
“Yes, he’s taking a visiting professorship. Says he hates the cold.”
On my way home that evening, I saw a shadow linger on my doorstep, then dart away. I broke into a run to pursue it, but not a trace was left, not even footprints in the snow. With one exception, that is: crinkled under the door and sodden with melt-water was a little envelope. Inside was a note, which read,
“The killer is left-handed.
Somewhere in South America, 1950
In the months that followed, I learned nothing more about the note and my mysterious informer, and soon it was time to pack my bags for Brazil. In the meantime, Dyson and Professor Feynman ventured on a road-trip together across-country, and when they came back, Dyson was drawing the little diagrams, too. I could sense we were on the verge of an outbreak, so I kept my distance.
Appearing as a student in Rio de Janeiro would strain credibility, so I took an apartment on the other end of town. It was in one of those old lacey buildings, with a balcony made of metal flowers overlooking the street. There always seemed to be parades going on, with lots of dancing, and often enough the distinguished professor could be seen revelling with the rest of them, banging away on his bongo drums.
Down in the crowd, I caught sight of a black derby hat, swimming toward my door. When I noticed the man, wearing a black trenchcoat and derby, stuffing an envelope through my letterbox, I realized it was my old friend. “Hey!” I shouted. It looked up. The phantom had no face, as far as I could see, just a grin in the corner of its mouth. Into the hallway and down the stairs I raced, hoping to catch him up in the crowd. On my way into the street, I scooped up the envelope, just in time to see a black coat-tail vanish around the block. I chased him into the alleyway, which led out into another street, amid sounds of livestock and festival-goers. Always he was just ahead of me, disappearing just around the corner. I came at last to a dead-end, no way out, and he was gone.
I sat against the wall, catching my breath and fanning my face with my hat. A gaggle of teenagers hung around— I had interrupted them, and they thought I was the funniest thing they had ever seen. I winked. Then I remembered the note. It read,
“What is the mesotron?
The mesotron, I pondered. Sounds like some kind of robot. “Hey, you kids ever hear of a mesotron?”
There was a lot more giggling and chattering in Portuguese, and every now and then I heard emphatic references to “mésons” and “Yukawa.” Before long they had circled me, and gestured that I follow them.
They took me to a loading dock where a young Brazilian was piling shipments in wooden boxes onto his covered pick-up truck. The boxes were stamped, “Ilford, Essex, U.K.” My new friends greeted him and told him all about me in the most rapid outpouring of syllables. He turned to me and asked, “You want to see a mesotron?”
I replied that I did.
“Well, come on! Hop in back!” He patted the bumper of his truck. A few of the kids were already climbing on board, so I did too. Among the Ilford boxes, I made a seat just as our driver swung shut the curtains at the end of the covered canopy. Soon we were off.
Through the boards lining the sides of the bed, I could see that we were driving out of town. After a few hours, I decided it was going to be a long trek, so I covered my face with my hat and fell asleep. I woke when we drove over a large bump, and it was already dark. A few hours later, we pulled over to the side of the road and camped out. I couldn’t see where we were, but it seemed to be no more than rank jungle, anyway. We ate the hottest soup of my life, and my new friends found my reaction to that hilarious as well.
The next day was the same. A long, unbroken stretch of bumpy driving through the jungle, camping by the side of the road at night. I asked, “Where are we going?”
“Chacaltaya,” César, our driver, informed me.
More roads, more jungle, and now I could sense a general upward trend, as we must have been approaching the Andes. The going got harder; we made more frequent stops to let the engine cool off. We seemed to be going up and down for ages…
I woke at night, with one of the youths shaking me from sleep. The truck was stopped. “Where are we?” I asked.
“Halfway to outer space!” he answered in an excited whisper.
The curtain opened, letting in a brilliant light. I covered my eyes. When they adjusted, I saw that there were only stars, blinding stars, stars so bright I still had to squint. White-hot singular stars, peppered by freckles of half-light, flowing in milky clouds of haze. I couldn’t see the ground.
“Outer space?” I asked, then wheezed. The air wasn’t good.
They took me by the elbows, helping me stand up and stumble toward the end of the truck. Over the tailgate, I could see soil and rock, barren and strange, everything in long, flat slabs. They helped me down: I hopped off the edge and fell in slow-motion, gradually tumbling to my knees, watching little puffs of otherworldly dust float up around me. Despite the slowness of everything, my knees and right ankle smarted something fierce. They helped me to my feet as I struggled to breathe.
They hoisted me up by both shoulders, and led me along the sloped plain. It was cold— colder than Ithaca, but a dry cold. In the night, I could see the lights of a house, and that’s where they brought me. Inside was pretty barren: a sofa, some chairs, chalkboard, and some kind of projector. I could smell chemicals. One guy got up off the end of the sofa, everybody moved over to fill his spot, and another sat down on the other end. They were all wearing knit caps that covered their ears, like aviator’s hats. They sat me down in a desk-chair.
There was a lot of going to and fro, stacking the Ilford boxes in a corner, as I breathed deeply and came to a greater understanding of just how much my knees and ankle were in pain. There was César, our driver, but the students called him Professor Lattes. If I thought Dick Feynman was young to be a professor, this guy beat him by at least a decade. When all was settled, he seemed to notice me, and pulled up a chair. Sitting backwards, he faced me and said, “You wanted to see the meson?”
“Mesotron,” I corrected, hoping this wasn’t all a case of mistaken identity.
“Meson, mesotron, mesoton, whatever people call it. It’s the Yukawa force you want to see, isn’t it?”
“The force of the nucleus! The energy of the atomic bomb! We’ve found it— coming from outer space.”
“Are we in space?” I asked weakly.
“We are on top of Chacaltaya, about as close as anyone can get to space. It’s to see the cosmic rays. Here, there are many, many more of the cosmic rays than at sea level. Let me show you.”
He stood up and unlatched something in the projector in the middle of the room. Then he retrieved a thick stack of something from a black paper bag. “This,” he said, “is a photographic emulsion. It’s like the film for a camera, but it is many, many layers thick.” He hefted it onto the projector tray, then slid it inside. “We don’t expose it to light. We put it outside, for many months and let the cosmic rays go through it.”
“Um, excuse me,” I raised a finger, “cosmic rays?”
“They are radiation falling from space.” Something long dormant perked up in my brain. There it was again, radiation— the cause of Marie Curie’s death! That something told the rest of my brain it had better pay attention. “Radiation is falling on us all the time, coming from somewhere in outer space. Nobody knows where exactly or how. But the cosmic ray particles have more energy than any radioactive elements or cyclotrons on earth.”
“More energy than radium?”
“Far, far more energy than radium.”
“Then why aren’t we killed by it?”
“Because they are low intensity. Ah—” he smiled, “you are wondering how they can be low intensity and high energy. I mean that there are not so many individual particles, but the ones that do are travelling very, very fast.”
“So what is this Yukawa force?”
“That is the nuclear force. Do you know anything about the forces?”
It jogged my memory of a chalkboard conversation long ago. “Four forces,” I said, “gravity, electromagnetism, the nuclear force, and…” and what?
“There are two nuclear forces: the weak force and the strong force.”
“To be honest, we say that there are four forces, but really there are just four categories of force. We see all kinds of nuclear transformations, and notice that one group of them happens rapidly, while the other happens slowly. Fermi described the weak force, the one that happens slowly, and it has long been clear that the strong force holds the nuclei in atoms together. It’s only when something overcomes the strong force that nuclei break apart, and that releases much energy because the force was very strong.”
“Like potential energy— springs,” I remembered Professor Feynman’s class.
“Yes, very much like a spring. A very, very stiff spring. This is the energy of the atomic bomb. Well, the curious thing about the nuclear forces is that they act over a very short range. Only when protons and neutrons are very close together do they feel any force at all.”
“When electromagnetic charges are far apart, they feel less force, too,” I said, proud of myself.
“But much, much more so. The force between electromagnetic charges is inversely proportional to the square of the distance between them, but with nuclear forces, it’s exponential.”
“Oh.” I had learned about exponentials. Every step decreased the force by a factor of 10, like the Richter scale for earthquakes. That’s a lot more dramatic than an inverse square law.
“How come they are different? Well, you know that in the quantum theory, the force between electromagnetic charges happens because a photon goes between the two charges, carrying momentum away from one and giving it to the other. That way, they both feel the force, and both change their motion as a result.”
“I didn’t know that, but go on.”
“This can happen no matter how far away the charges are, and in fact the intensity is inversely proportional to the square of the distance between them, just like the light of a light-bulb. If you shine a light-bulb on a wall, the intensity of the light on the wall is inversely proportional to the square of the distance from the bulb, because as the light travels out, it expands as the surface of a sphere around the bulb. The area of a sphere is , so the intensity decreases as , with being the distance to the bulb.
Suppose that nuclear force works like electromagnetism. We don’t know that it does, but it’s a good assumption to start with. In between the nuclear particles, protons and neutrons, there must be some particle like the photon, but for nuclear forces. A nuclear photon! Dr. Hideki Yukawa was thinking about that, and he knew that in the quantum theory, particles are never quite stationary, but are always buzzing around within a wavefunction, a region of space where their position might be.”
“They don’t teach this in school, do they doc?”
“Well,” he tipped his head back and forth, “not at the beginning level. The positions of particles is never quite definite, especially when they’re travelling slowly. The wavefunction is a little cloud of space describing how likely the particle will be at each point, and this blob is usually exponential, with an exponent proportional to the particle’s mass.”
“So a particle with a large mass,” I gestured with my hands, getting it wrong the first time and correcting myself, “is usually found in a very tight region of space, and a particle with a very small mass could be very spread out.”
“Exactly. And a particle with zero mass—”
“— can be anywhere!” I interrupted.
“It has to travel at the speed of light, like the photon. The photon is massless. It gets anywhere it has to go, and so the electromagnetic force can be felt between charged particles that are light-years apart; it’s just the intensity goes down by .”
“But not so for the nuclear photon, right?”
“Right. Or that is what Yukawa was thinking. Yukawa said, what if there is a nuclear photon, and its mass is such-and-such: it would cause attraction between the proton and the neutron, but only when the proton and the neutron are so close to each other as to be within the wavefunction of a stationary nuclear photon. As soon as a proton or a neutron goes out of the wavefunction, zip—” his hand flew up into the air, “no more nuclear force, and all the energy that held it in is released.”
“Like in an atomic bomb?”
“Yes.” He nodded gravely. “In the atomic nucleus, all the protons are electrically charged and nuclearly charged, with the electromagnetic force pushing out and the nuclear force pulling in. All we have to do is push it over the edge… potential energy released, becomes kinetic, light, and heat… and a very big bomb.”
We sat in silence for a moment.
“Well!” He slapped his knees. “Let me show you the meson!”
“You know, professor, you never did tell me what is this meson, or mesotron, or whatever.”
“It is the nuclear photon!” he seemed a little aghast.
Back at the projector, he clamped a few levers into place, and turned on the bulb. A fan churned and a dull light ignited, shining on the wall. He tuned the focus, and a spattering of dark spots appeared. It was like a shadow-play. “What you are seeing is the developed film, and these are the cosmic rays.”
“I thought you said you never exposed the film.”
“We didn’t—” a little smile came to his face, “the cosmic rays did. Radiation exposes film, in just the same way that light exposes film, but radiation can pass through dark paper, especially these cosmic rays which are so very, very energetic.” He tuned a dial, and the little spots moved. “Now I am changing the focus, so that you see different layers. When the cosmic rays went through the film stack, they exposed little lines, leaving little trails, and those trails look like spots if you focus on a single depth with a microscope like this one. But now watch this!” He was getting giddy— the high altitude air must have been getting to him. “Watch this one spot: see, it is moving along with a certain speed, and then there! It changes direction entirely!”
“Did it hit something?”
“No, too much energy to change that dramatically from a collision. Look at it again. See? It just turns. Immediately. At one spot.”
He seemed to be waiting for a suggestion, but nothing was coming to me.
“It has decayed!” He shouted. “It decays into another particle; in this case, an electron. The top part of the path is meson, and the bottom part is electron. Now— question for you is, where did the momentum go?”
The momentum— that word recalled table-top demos and homework problems with cars crashing into each other. The meson’s momentum before decay was clearly different from the electron’s momentum after decay, simply by the fact that they went in different directions. “I don’t see where it went,” I had to confess.
“Exactly! You don’t see it at all!” He was on the verge of a cackling laughter, and I wondered for my safety. “The rest of the momentum went with the neutrino, and the neutrino is invisible.”
“No such thing!” One of his fellow researchers stood up, pointing an accusing finger. “You can’t just invent ghost particles when you don’t see the momentum.”
I clearly remembered Fermi talking about neutrinos with no suggestion that they might not be real.
“Then how else do you explain the loss of momentum? Look!” César Lattes tuned the dial again.
“I’ll believe it when I see it, but I haven’t seen it.” He sat down again on the couch, arms folded.
“A true experimentalist,” César chuckled, “that’s good. That’s good. Well, someday, we will see it. Right now, no.”
“So this is the meson that causes neutrons and protons to stay together in the nucleus?” I asked, trying to get back to the subject.
“No, it is not.”
“What?!” I felt I had been lied to.
“By measuring the energy of the electron, we know that this meson’s mass is consistent with what Yukawa needs for the nuclear photon, but this particle has no strong nuclear interactions, as it would need.”
I had been lied to.
“That’s why, what I really want to show you is this—” he tuned the focus quickly, past lots of spots, some of them with kinks, until he found what he was looking for. “This one here.” It was a spot like all the rest. “This meson decays, not unusual, but then watch the decay product.”
A second kink. “It decays again?”
“It decays again.” He spoke as though his words were full of import.
“Why is that important?”
“Electrons don’t decay.” He seemed puzzled that I didn’t get it. “If after the second kink, the particle is an electron, what was it before the first kink?”
It slowly dawned on me. “There are two mesons?”
“Two mesons, yes!” He raised his eyebrows. “A new meson decays into the standard meson, and then that standard meson decays into an electron, throwing off neutrinos each time. We’ve labeled the top one , and the bottom one , Greek letters, just to keep them straight. And then we see this over and over again, but only at very high altitudes. So I went to Berkeley where they have a cyclotron. Even with the cyclotron, we were able to see this two-decay pattern, and isolated the pi mesons and studied its properties. It indeed feels nuclear forces— we have found the nuclear photon!”
“It came from outer space,” I mused. “Imagine that.”
The next morning, César took me up a little hill to see an emulsion stack, a wooden box holding a few feet of film, all wrapped in black. I couldn’t get over my dizziness— the view was spectacular!
As I wasn’t getting any better by the mid-afternoon, César asked one of his students to take me down the mountain, to which he responded with a bit of annoyance. If he was supposed to take me further than the nearest village, I’ll never know, but that’s how far he took me. It was then up to me to get myself back to Brazil. I limped eastward.
Rio de Janeiro, 1956
When I finally made it back to my apartment in Rio, I found myself face-to-face with an irate landlord. Promising 6 years of back-rent, I went back to work on the case. With this new pi meson, I decided to round up a list of all the suspects. With a little help of the university library, I compiled the following:
- electron: orbits atom, flows through wires as electricity, electrically charged (–1), unaffected by nuclear force
- proton: constituent of atomic nucleus, electrically charged (+1), affected by nuclear force
- neutron: constituent of nucleus, uncharged electrically, but affected by nuclear force
- alpha particle: alias for a Helium nucleus, consists of two protons and two neutrons
- beta particle: alias for electron
- X-ray, gamma particle, photon: light of various energies, called by different names. Communicates electrical forces between charged particles but uncharged itself. Doesn’t like to get involved.
- neutrino: electrically neutral, unaffected by nuclear strong force, only nuclear weak force. Proposed to explain momentum imbalance. Hypothetical.
- mu meson: all properties identical to electron except that it is 200 times heavier and decays to electron and neutrino. Weird.
- pi meson: communicates nuclear forces, like the photon for electromagnetism. Comes in three forms: electrically charged (+1 and –1) and neutral, unlike the photon.
After this point, it started to get a bit more complicated. After a few conversations in the physics department, and I had to add:
- positron: “antimatter” twin of electron, all properties the same but reversed charge (+1). Required by equations linking quantum theory with Einstein’s relativity. Discovered in 1932, but rare.
- antiproton: antimatter twin of proton, same deal: negatively charged (–1). Discovered last year.
- V-particle, or K meson: comes in three forms: electrically charged and neutral; decays into pi mesons, mu mesons, electrons, and a smattering of neutrinos. The chain just gets longer and longer!
- Lambda baryon: a heavy “V-particle” that decays into neucleons (protons or neutrons) and mesons, neutral
- Xi baryon: decays into lambdas and pi mesons! leading to a whole chain of decays on both sides. Negatively charged (–1).
- Sigma baryon: charged forms (–1 and +1) also decay into nucleons and mesons, neutral form decays into lambdas and mesons.
More and more suspects, with no end in sight! It seems if you just look hard enough, you’ll find something new that decays twenty times and ends up a puddle of electrons, photons, protons, and neutrinos. After a little talking to, I could understand the antimatter versions of everything: for each +1 charged particle, there must be a –1 particle, and I could understand why we need the pi meson to glue nucleons together, but all those extra mesons and baryons smell distinctly of red herring.
It was at this time that I also realized Dr. Feynman was gone, back to Cornell. So I’m headed north.
Ithaca, NY, 1956
No sign of him here, either. Disappear for a few years, and everything changes. When I left, the basement of Rockefeller Hall was being emptied out for one of those cyclotron-accelerators, and now it had already been dismantled and pieces of it were part of a new synchrotron in a new building.
“Is it going to discover more particles?” I asked, a little warily.
“Could be,” said the graduate student, who had abruptly introduced himself as Karl Berkelman. “But it would be better if it explained all of those new particles.”
“And the Mystery of the Missing Neutrino,” I added.
“Missing Neutrino? The neutrino’s been discovered. In Georgia, in a bubble chamber next to a nuclear reactor.”
“Really? I thought it was too weakly interacting.”
“Not if you have enough of them and wait long enough,” he answered ardently. “Sitting next to a nuclear reactor is like having a sun next door. Then all you have to do is wait for beta decay to happen in reverse: neutrino plus proton goes to neutron plus positron. The neutron gets captured and the positron finds an electron to annihilate with, so it looks like these two rare events happening at the same time.”
“I bet Fermi was pleased.”
“Fermi’s dead. Stomach cancer— it got two of his students, too. Probably all of that radiation from the reactor they built.”
I was about to ask if he wasn’t a little worried himself, when he introduced me to the director of the laboratory, Bob Wilson. Bob was a genial fella, somehow part-cowboy and part-nerd without contradiction.
“They let me carry a gun at Los Alamos,” he said with some glee.
“What?” I asked.
“At Los Alamos, I packed a six-shooter.”
I was a little mystified. “Why are you telling me this?”
“Like you said, the nerd-cowboy thing. Born in Wyoming, I learned to shoot before I could stand up straight. So when there was a sample of enriched Uranium that needed protection, I asked Oppie if I could be registered to carry a gun.”
I need to be careful what I narrate aloud.
“Anyway,” he continued, “that’s the right metaphor for what we’re doing. This is about as near to the wild frontier as it gets! The subatomic world: it’s not just a nucleus and some mesons holding it together, it’s a whole landscape of weird new particles and even weirder interactions. Did you know that empty space is just teeming with electron-positron pairs, creating themselves out of nothing and annihilating spontaneously?”
“I assure you, I had no idea.”
“You can scatter high-energy photons off of them. We did it just a few years ago with the old machine. Ah, here it is,” he opened the door to a basement filled with a giant mechanical doughnut. “Ain’t she a beauty?”
“This is the new sychrotron?”
“Yup. Come and take a look!” He showed me all the ins and outs of the machine: how it accelerated electrons pretty close to the speed of light, how the gradient was alternated for strong focusing of the beam, the beamlines that led to different experiments; everything seemed to be in a perpetual state of dismantling and reconstruction.
“Does it work?” I asked, perhaps naïvely.
“What’s that? Oh, not right now, but we’ll get it to work again.”
“You mean you got all these people together, all this electronics built, and it doesn’t work?”
He waved me down. “Don’t worry about it. Something that works right away is over-designed, and will have taken too long to build and cost too much. When you see all of these precision instruments, you shouldn’t think that if we put it all together and it doesn’t work, we’ll go home sad. No, when it doesn’t work, it doesn’t work because of a few fixable problems, and there’s loads of diagnostics to figure out which those are. Besides, flying loose like this means that we have the flexibility to try new ideas first, before the big labs finish their paperwork. See this strong focusing I told you about? There’s a story about that.
“So about 10 years ago, a bunch of universities got together and founded an accelerator complex on an old army base near Brookhaven, NY with Manhattan Project money. There they built the world’s largest synchrotron, called the Cosmotron—”
“Yeah! Cosmotron! It’s a great name! It delivers energies on par with cosmic rays, yet it’s a synchrotron, so why not? Well, the Europeans got jealous and decided they wanted a big accelerator lab, too, and after a lot of negotiations, sent some scientists to Brookhaven to learn how it’s done. Seeing that the magnets could only focus horizontally, but not vertically, one of them asks, ‘Why not alternate horizontal and vertical focusing?’ Well, they had never thought of that. With more focusing, you need less magnet, which is easily the most expensive part, so in the long run you can get more energy for the buck. Based on this idea, Brookhaven is building an even bigger synchrotron, and the Europeans are building their own, but neither of those are finished yet. We heard about it while we were still building this guy here, and just changed the design mid-stream to take advantage of it. And it’s payed off big-time. A number of other accelerator projects around the world weren’t quite as flexible, and they’re still building living dinosaurs. That’s the trick: keep it flexible and keep it cheap, and reap the rewards.”
“How cheap was that wrench you melted?” One of the other physicists challenged, eyes gleaming.
“My old boss was even more spend-thrift than I am,” Bob explained. “He had the unfavorable experience of inventing cyclotrons in the Depression. He fired me once for melting a wrench.”
“A whole wrench!” the other physicist emphasized. “Melted into a pool of metal!”
“That was only the second time he fired me.”
“So I take it you’re not a fan of big laboratories,” I asked.
“Oh, no, they’re fine. It’s the only way you can make the really big machines and reach the really high energies. Some things you just can’t find out without going up there and looking. But the sad thing about them is that they’re so far from the classroom: they’re breeding a generation of researchers who’ve never taught. Ideally, a physicist ought to be able to teach a roomful of students at 2 o’clock, calibrate an instrument at 3, then be back in his office for homework questions at 4. I think we’re starting to lose that connection between teaching physics and doing it.”
I thanked him for showing me around, but I had to catch up with Feynman. “Oh, he’s at Caltech now. Likes the warmth.” Caltech. Another cross-country trip. So be it.
Before packing my bags, I took a leisurely stroll around Bebe lake. It was early autumn, and I was beginning to realize how nice the north-east could be from time to time. I was standing on the top of an arched stone bridge when I heard a rustling in the woods. I could have sworn I saw something dark and sinister between the trees, up the steep hill, but there was nothing now but swinging leaves. Leaves, and a little envelope. Another envelope! I snatched it up and, looking over my shoulder twice, read it.
“Seek the Dragon Lady in Columbia.
—an Old Friend”
“I’ve had enough of this!” I shouted at the undergrowth. “Dragon Lady?” I thumbed the card, then pulled the two old cards from my pocket, rough and weathered next to this one. “There is no way I’m going back to South America!” I shouted again.
I waited, but no answer was forthcoming. Clearly, I was going to need some help with this, so I took all three notes back to the nuclear studies lab. Sure enough, Bob wasn’t there; he was in his office to answer homework problems. I brought him mine.
“Dragon Lady??” he asked, obviously highly amused. “No, I don’t know any Dragon Lady, and I’ve never even been to Columbia. What are these other ones? You say it’s a guy in a trenchcoat?”
“He followed me to Brazil.”
“Hard to imagine anybody with that much time on their hands.” I ignored the inferable insult. “What’s this? The ‘mesotron’? God, I haven’t head anybody use that word in ages.”
“I found out about that one right away— and it was a good lead. I was just in time to catch a pickup to Chacaltaya, where I saw one of the first photos of a pi meson.”
“Wow, that sounds like fun.”
I put the long walk home out of my mind. “Why’s it called a mesotron, or meson, anyway?”
“It’s Greek. Greek for ‘medium.’ Electrons and neutrinos, they’re leptons, ‘leptos’ for ‘light’, all below an MeV or so in mass. Mesons are medium at a few hundred MeV, and baryons are heavy— ‘barys’ is like thick or stout. Baryons are usually a thousand MeV or more. That’s the advantage of a big accelerator: you can’t get heavy particles without putting in enough energy to create their mass. A consequence of relativity, this conversion of energy into mass.”
“So these particles, they’re named by weight?”
“Sure, that’s almost all we know about them. Like I told you about this being a frontier— we don’t know much of anything yet. We’ve just dumped the puzzle on the table and all we can do so far is group the edge pieces with the edge pieces, the middle pieces with the middle pieces, and maybe decide where the corner pieces go. There’s something special that makes baryons a thousand times heavier than leptons, and considering that none of the leptons feel the strong nuclear force, while all of the baryons and some of the mesons do, that’s gotta be a clue!”
“Like the four forces— they’re just groups,” I added.
“Yeah, like the four forces. We think that all the weak decays are related by some Universal Fermi Mechanism, and we think that all the strong forces are due to Yukawa’s meson, but nobody’s really solved that. Nobody’s written down an equation that works for all of them.”
He flipped to the next card, and lingered. Something must have struck a chord. “The killer is left-handed,” he muttered.
“Do you know who it is?”
“No, no, it’s just—” back to the new card— “the Dragon Lady…”
“Is she left-handed?”
“I have a hunch,” he said finally, handing me back the cards. “Go to Columbia University in New York City, the physics department, and ask for Madame Wu. Ask her about left-handedness. But don’t call her ‘Dragon Lady.'”
“Do you think this will solve the mystery?”
“I’m sure it’s a clue,” he smiled confidently. “The game is surely afoot.”