Cloud Chambers: Unveiling the Invisible - A Short History of Nearly Everything

Okay, so, uh, where were we? Ah, right. So, basically, there were these scientists, right? Back, uh, a while ago. One dude, C.T.R. Wilson, he was always hiking up this mountain in Scotland, Ben Nevis, trying to figure out clouds. Super damp place, apparently. And he just thought, you know, there's gotta be an easier way to do this. So, he goes back to Cambridge, to the Cavendish Laboratory, and he builds this thing called a cloud chamber. Basically, he could cool and wet the air, create a mini-cloud, you know, in the lab.

And it worked great! But, get this, there was this totally unexpected bonus. When Wilson, like, shot an alpha particle through the chamber, making a cloud, it left this obvious trail. Just like a plane leaving a contrail. So, boom, he'd invented a particle detector, and it gave this, like, really convincing proof that these subatomic particles actually existed. Crazy, huh?

Later on, other scientists at Cavendish, they made even stronger proton beam thingies. And this other guy, Ernest Lawrence, out in California at Berkeley, he built this famous cyclotron. Basically, an atom smasher. That’s what they called them for a while. And all these new inventions worked pretty much the same way, then and now. They’d, like, accelerate a proton, or some other charged particle, along a track – sometimes it was a ring, sometimes a straight line – to crazy high speeds, and then *wham*, smash it into another particle, just to see what flew out. So, yeah, "atom smasher" kinda fits, doesn't it? It's not exactly subtle science, but, generally speaking, it works.

And as physicists started building bigger and bigger machines, getting more ambitious, they started discovering, or, well, figuring out, all these different particles, or families of particles: pions, muons, hyperons, mesons, K-mesons, the Higgs boson, intermediate vector bosons, baryons, tachyons. It was a never-ending list. Even the physicists were starting to get a little freaked out. Like, there's this story about Enrico Fermi, and a student asked him the name of some particle or other, and Fermi, he's like, "Young man," he says, "If I could remember the names of all these particles, I’d have become a botanist." Haha!

Today, the names of the accelerators sound like, I don't know, weapons from Flash Gordon or something. You know, Super Proton Synchrotron, Large Electron-Positron Collider, Large Hadron Collider, Relativistic Heavy Ion Collider. The energies they're using are just mind-boggling. Some of them can only run at night so the neighbors don’t notice their lights dimming when the thing fires up! They can, like, get an electron to zip around a seven-kilometer tunnel, like, forty-seven thousand times in under a second. Wow. And, yeah, there was this fear, you know, that some over-eager scientist would accidentally create a black hole, or even a "strangelet." And, theoretically, these things could interact with other subatomic particles, cause this runaway chain reaction, totally out of control. Well, you're still here, reading this or, in this case, listening to this, so, obviously, that hasn't happened. Fingers crossed, right?

Finding these particles takes real concentration. They're not just tiny, they're moving super fast, and they vanish in a flash. Particles can appear and disappear in, like, a tiny fraction of a second, a billionth of a trillionth of a trillionth of a second. I can't even imagine that! Even the more stable, unstable particles, they only hang around for, like, a hundred-millionth of a second, tops.

And some of these particles? They're practically impossible to catch. Every second, a trillion trillion neutrinos, tiny, almost weightless, reach the Earth, mostly from the nuclear reactions in the sun. And they just pass right through the planet, and everything on it, including you and me, like Earth isn't even there. So, to catch just a few of these things, scientists have to go deep underground, usually in old mines, and use these huge containers filled with, like, fifty-seven thousand cubic meters of heavy water. That’s water that contains a lot of deuterium, because that’s the kind of place that's shielded from other radiation.

And, very, very occasionally, one of these neutrinos will actually bump into an atom's nucleus in the water, producing a tiny bit of energy. And by counting these tiny bits, the scientists can slowly, you know, piece together the basic nature of the universe. So, for example, in 1998, Japanese observers announced that neutrinos *do* have mass, but, you know, not much, about one-ten-millionth of an electron.

These days, finding particles, it's really about the money. And a *lot* of money. In modern physics, it's kind of funny, the size of the thing you’re looking for is often inversely proportional to the size of the equipment you need to find it. The European Organization for Nuclear Research, CERN, it’s like a small city! It straddles the border between France and Switzerland, employs, like, three thousand people, and covers several square kilometers. They've got this ring of magnets that weigh more than the Eiffel Tower, surrounding a 26-kilometer underground tunnel.

Someone, James Trefil, said, smashing atoms is easy. Just turn on a fluorescent light. But smashing a nucleus requires serious money and a ton of electricity. And turning particles into quarks, that is, the particles that make up the particles, that takes even more juice, and even more money: trillions of watts and the budget of a small Central American country. CERN’s Large Hadron Collider, it’s supposed to generate fourteen trillion watts, and cost over a billion and a half dollars. Crazy! (Although, you know, these big projects do have some useful side effects. The World Wide Web? Yeah, that came out of CERN. Some guy there, Tim Berners-Lee, invented it in 1989.)

But those numbers are nothing compared to the energy and cost of the Superconducting Supercollider. Back in the 80s, they started building this thing in Texas, but it, like, had a super-collision with Congress, and, well, it was never finished, unfortunately. The idea was to recreate conditions close to, like, the first trillionth of a second of the universe, to explore the "ultimate nature of matter," you know, like they always say. They were going to hurl particles around an 84-kilometer tunnel, getting them up to ninety-nine trillion watts. It was a huge plan, but it was going to cost, like, eight billion dollars, eventually ten billion, plus a few hundred million to run it every year.

It's probably the best example of throwing money down a hole, ever. Congress spent, like, two point two billion, then canceled the project after building twenty-two kilometers of the tunnel. So, yeah, Texans can be proud of having the most expensive hole in the universe. One of my friends, Jeff Guin, he told me, it's just a big empty space, surrounded by a series of disappointed little towns.

After the Supercollider fell apart, particle physicists, they scaled back their ambitions a little. But, even the more "modest" projects can cost a shocking amount, compared to, well, pretty much anything else. Someone suggested building a neutrino observatory in an abandoned mine in South Dakota, the Homestake Mine, and that was going to cost, like, half a billion dollars, not counting the yearly operating costs. And another two hundred and eighty-one million in "general refurbishment costs." Meanwhile, a particle accelerator in Illinois, Fermilab, just to update the materials, that was going to cost two hundred and sixty million.

So, yeah, particle physics is an expensive business. But it's also a really rewarding one, I guess. Today, we know about way more than one hundred and fifty particles, and there are, like, a hundred more that are suspected of existing. But, unfortunately, like Richard Feynman said, it’s "very difficult to understand the relations of all these particles, and what Nature wants them for, or what the connections are from one to the other." Every time we open a box, we find another box inside. Some people think there are tachyons, particles that travel faster than light. Some are desperate to find the graviton, the thing that carries gravity. How far down the rabbit hole have we gone? It's hard to say. Carl Sagan, in his book *Cosmos*, he said if you could burrow inside an electron, you’d find it was a whole universe in itself, like those old sci-fi stories. "Inside, a hierarchy of still smaller particles made up what served as galaxies and lesser structures, themselves universes at the next level, and so on forever -- an infinite regression inward, universes within universes, endlessly."

For most of us, it’s just an unimaginable world. Even reading a basic guide to particle physics, you’ve gotta wade through this language barrier. Like, "Charged π-mesons and anti-π-mesons decay respectively into a μ-meson plus an anti-neutrino and an anti-μ-meson plus a neutrino, with a mean lifetime of 2.603 × 10−8 seconds; neutral π-mesons decay into two photons, with a mean lifetime of about 0.8 × 10−16 seconds; μ-mesons and anti-μ-mesons decay respectively into..." And so on and so on. And that’s from a book written for the general public by, supposedly, a straightforward writer, Steven Weinberg.

In the 1960s, Murray Gell-Mann, a physicist at Caltech, tried to simplify things. He invented this new way of classifying particles, and, according to Steven Weinberg, it "did to some extent make the multitude of hadrons somewhat less opaque.” Hadrons are, like, a collective name for the protons, neutrons, and other particles that are affected by the strong nuclear force. Gell-Mann’s theory said that all hadrons are made up of smaller, more basic particles. His colleague, Richard Feynman, he wanted to call these new particles "partons," like Dolly, but it didn't catch on. They ended up being called quarks.

Gell-Mann got the name from a line in James Joyce’s novel, *Finnegans Wake*: "Three quarks for Muster Mark!" (Sharp-eared physicists rhyme the word with "storks" or "larks," although it’s pretty clear Joyce probably meant the latter pronunciation.) This basic simplicity of quarks didn't last long. As they learned more, they needed even finer classifications. Even though quarks are too small to have any actual color or flavor, or any identifiable chemical properties, they've been divided into six types: up, down, strange, charm, top, and bottom. Physicists call these their "flavor." Weird, right? And then they're further divided into three colors: red, green, and blue. (People suspect those names came from, like, the psychedelic era in California. Maybe not a coincidence.)

And, eventually, we ended up with the so-called Standard Model. It's basically a parts kit for the subatomic world. It includes six quarks, six leptons, five known bosons, and one hypothetical boson, the Higgs boson, named after a Scottish scientist, Peter Higgs, plus the three of the four known forces: the strong nuclear force, the weak nuclear force, and the electromagnetic force.

Basically, the model says that matter is made of quarks, held together by particles called gluons. Quarks and gluons together make up the stuff in the nucleus of an atom, protons and neutrons. Leptons are the source of electrons and neutrinos. Quarks and leptons together are known as fermions. Bosons, named after an Indian physicist, S.N. Bose, are the particles that generate and carry force, including photons and gluons. And the Higgs boson? Maybe it exists, maybe it doesn’t. It's just, like, invented to give particles mass.

So, it's kind of clumsy, right? But it's the simplest model we've got for explaining everything in the particle world. Most particle physicists feel, like Leon Lederman said in a documentary, that the Standard Model isn't really beautiful or simple. "It’s too complicated, it has too many arbitrary parameters," Lederman said. "We really don’t understand why the Creator had to turn twenty knobs to set twenty parameters in order to create the Universe as we know it." Physics is supposed to be about finding ultimate simplicity, but everything so far is just this messy, beautiful tangle. Or, like Lederman said, "We have a deep feeling that this picture is not beautiful."

Not only is the Standard Model clumsy, it’s incomplete. For one thing, it doesn’t say anything about gravity. You can search the whole Standard Model and you won’t find anything that explains why your hat doesn't float up to the ceiling. And, to give particles mass, you’ve got to bring in this hypothetical Higgs boson, and whether it even exists, that's a question for physics to answer. So, like Feynman famously felt, "We are, therefore, left in a quandary, not knowing whether we are right or wrong, but we do know that we are in some difficulty, or at least in some incompleteness."

So, trying to tie everything together, physicists came up with something called string theory. It says that what we thought were particles, quarks and leptons, are actually "strings," vibrating strings of energy, that wiggle in eleven dimensions, including the three we know, plus time, plus seven other dimensions that, uh, we don’t know about yet. These strings are super tiny, so small they look like point particles.

By bringing in extra dimensions, string theory helps scientists kind of reconcile quantum mechanics and gravity, but, it also means that anything a scientist says about the theory sounds, uh, a little unsettling, like some weirdo on a park bench telling you his ideas, and you slowly edge away. Like, here’s the physicist Michio Kaku explaining the structure of the universe in terms of string theory: "A heterotic string is a closed string with two types of vibrations, clockwise and counterclockwise, treated differently. The clockwise vibrations live in a 10-dimensional space. The counterclockwise vibrations live in a 26-dimensional space, of which 16 dimensions have already been compacted (we recall that in Kaluza’s original 5-dimensional space, the 5th dimension was curled into a circle and has already been compacted)."

And so on, for, like, three hundred and fifty pages.

String theory led to something else, the so-called M-theory. This brings in the idea of "membranes," surfaces, into the heart of the physics. And, well, this is probably where most of us get off the knowledge highway. Here’s a quote from *The New York Times*, trying to explain it as simply as possible to a general audience:

"In the remote past, the igneous process began with a pair of flat, empty membranes; they were parallel to each other in a warped 5-dimensional space... the two membranes constituted the walls of the 5th dimension, and probably originated as a quantum fluctuation from nothing in the even remoter past, before drifting apart."

Can’t argue with that, can we? Or understand it, for that matter. By the way, "igneous" comes from the Greek for "fire."

So, yeah, things have gotten to the point in physics where, like Paul Davies said in *Nature*, "It is hard for the non-physicist to distinguish you from a run-of-the-mill crank." Funny story, in the fall of 2002, this came to a head. These French physicists, twin brothers Igor and Grichka Bogdanov, came up with a theory about extremely high densities, involving things like "imaginary time" and the "Cooper-Schwinger-Martin condition," to describe, basically, nothing. You know, the universe before the Big Bang. Supposed to be unknowable, because it happened before physics and its properties existed.

The Bogdanov theory caused a huge fight among physicists. Was it complete nonsense, a work of genius, or a hoax? "From a scientific point of view, it is evidently pretty much complete nonsense," said Peter Woit, a physicist at Columbia, to a reporter at *The New York Times*. "However, it is not too different from a lot of other things one sees these days."

Karl Popper, who Steven Weinberg called the "dean of modern philosophers of science," he once suggested that physics might not have a final theory. Every explanation needs a further explanation, forming "an infinite chain of ever more fundamental principles." The other possibility is that this knowledge might be just totally beyond our understanding. "Happily," Weinberg wrote in *Dreams of a Final Theory*, "our intellectual resources do not yet seem exhausted."

Almost certainly, there’ll be more insights in this field. And almost certainly, most of us won't understand them.

So, just as physicists in the mid-20th century were, you know, scratching their heads about the small world, astronomers were finding out that understanding the *big* universe was also incomplete.

Last time, we talked about Edwin Hubble. He’d confirmed that nearly all the galaxies we can see are moving away from us, and that the speed they're receding is directly proportional to their distance. The farther away, the faster they're moving. And Hubble found he could describe it with a simple equation: Ho = v/d. Ho is a constant, v is the speed the galaxy is moving away, and d is its distance from us.

Since then, Ho has been known as the Hubble constant, and the whole equation is the Hubble Law. Using his equation, Hubble calculated the age of the universe as about two billion years. And that was a bit awkward, because even by the late 1920s, it was becoming pretty clear that a lot of things in the universe, maybe including Earth itself, were older than that. So, refining that number has been a constant worry for cosmologists.

The only thing constant about the Hubble constant is that there’s always disagreement about its value. In 1956, astronomers discovered that Cepheid variable stars, which they use to measure distances, were actually more complicated than they thought. They could be divided into two classes, not one. So, they recalculated, and came up with a new age for the universe: somewhere between seven and twenty billion years. Not super precise, but at least old enough to include the formation of the Earth.

And then, for years, there was this big argument between Allan Sandage, who took over from Hubble at the Mount Wilson Observatory, and Gerard de Vaucouleurs, a French-born astronomer at the University of Texas. Sandage did years of careful calculations, and came up with a Hubble constant of 50, which meant the universe was twenty billion years old. Vaucouleurs was just as sure that the Hubble constant was 100. Yeah, you're probably wondering what "a constant of 50" or "100" actually means. Well, it’s about the units of astronomical measurement. Astronomers don’t use light-years when they’re talking to each other, they use “parsecs,” which are based on parallax. One parsec is about 3.26 light years. Seriously big scale. The constant is measured in kilometers per second per million parsecs, so a Hubble constant of 50 means 50 kilometers per second per million parsecs. It means the universe was half as big and half as old as Sandage thought: about ten billion years. Then, in 1994, things got even more uncertain. A group at the Carnegie Observatories in California used measurements from the Hubble Space Telescope and suggested the universe was only eight billion years old. Even they admitted it was younger than some of the stars in it! And then, in 2003, a group from NASA and the Goddard Space Flight Center announced, confidently, that the universe was 13.7 billion years old, give or take ten million years. So, that settled things, at least for a while.

It's really hard to be definitive, because there's a lot of room for interpretation. Imagine you're standing in a field at night, and you want to figure out the distance between two lights far away. Using simple astronomical tools, you could easily figure out that both bulbs were equally bright, and one was fifty percent farther away than the other. But you couldn't figure out if the closer light was a 58-watt bulb thirty-seven meters away, or a 61-watt bulb thirty-six and a half meters away. And you’ve got to consider distortions caused by the Earth’s atmosphere, interstellar dust, background stars polluting the light, and a bunch of other things. So, your calculations end up being based on a bunch of nested assumptions, and any one of them could be wrong. And there's the problem that using telescopes is always expensive. For a long time, measuring redshifts, which is how they figure out how fast things are moving away, meant a really long time on a telescope, which cost a ton of money. Sometimes, they’d spend all night getting one photograph. So, astronomers had to, or, you know, were willing to, make conclusions based on very little evidence. As one journalist, Jeffrey Carr, pointed out, we’re "building mountains of theory on molehills of evidence" in cosmology. Or, like Martin Rees said, "Our present contentment (with our state of knowledge) may reflect a paucity of data rather than a surfeit of insight."

By the way, this uncertainty applies to the relatively close stuff, and to the far reaches of the universe. When astronomers say the galaxy M87 is sixty million light-years away, they’re really saying it’s *somewhere* between forty million and ninety million light-years away. Not exactly the same thing. Things in the big universe get exaggerated, naturally. So, our best guess for the age of the universe right now seems to be somewhere between twelve and thirteen and a half billion years. But we're still a long way from agreeing on that.

There’s this cool theory that the universe isn’t as big as we thought. Some of the galaxies we see far away might just be reflections, ghost images caused by reflected light.

There’s just so much we don’t know, even at a pretty basic level. We don't even know what the universe is made of. When scientists calculate how much stuff they need to keep things together, they always find that they're way short. At least ninety percent of the universe, maybe as much as ninety-nine percent, seems to be made of "dark matter." The stuff we can’t see. It’s kind of unsettling to think we’re living in a universe we can barely see, and we can’t do anything about it. There are two main suspects. One is WIMPs, weakly interacting massive particles, invisible tiny stuff left over from the Big Bang. The other is MACHOs, massive compact halo objects, which are just another way of saying black holes, brown dwarfs, and other dim stars.

Particle physicists tend to favor the particle explanation, WIMPs, and astrophysicists lean towards the star explanation, MACHOs. MACHOs were ahead for a while, but they couldn't find enough of them, so, the wind shifted back to WIMPs. The problem is that WIMPs have never been found. Because they interact so weakly, they're really hard to detect, even if they exist. There's too much interference from cosmic rays. So, scientists have to go really deep underground. At a kilometer deep, there’s only a millionth of the cosmic ray bombardment. But even with all that, "the universe is still two-thirds short on the balance sheet," as one commentator said. For now, let’s just call them DUNNOs, dark unknown non-reflective objects.

Recently, there's been evidence that the galaxies are not just moving away from us, but that they’re moving away faster and faster. That's totally against what they expected. It looks like the universe is filled not only with dark matter, but with dark energy too. Scientists sometimes call it vacuum energy, or quintessence. Anyway, the universe seems to be expanding constantly, and nobody can say why. One theory is that empty space isn't really empty. Particles and antiparticles are constantly popping into and out of existence, and they’re pushing the universe outwards, faster and faster. It turns out that the thing that solves all this is, unbelievably, Einstein's cosmological constant. It’s that little equation he stuck into general relativity to disprove the idea of an expanding universe, and the one he called “the biggest blunder of my life.” Seems like he was right after all.

So, we live in a universe whose age we can’t quite figure out, surrounded by stars we don’t really know the distances to, filled with matter we can’t identify, and governed by physical laws we don’t really understand.

On that really uncertain note, let’s go back to Earth, and think about what we *do* understand. Although, at this point, you probably wouldn’t be surprised to hear we don’t *really* understand it either. As well as the stuff we’ve understood for a long time but didn’t understand then but do now.