Chapter Content
Okay, so, Chapter 12, right? Um, it's all about this, this Reverend Robert Evans. This guy, yeah, he's a pretty quiet, cheerful guy, lives in the Blue Mountains in Australia, you know, west of Sydney. And get this, when the sky's clear and the moon isn't too bright, he hauls out this, like, big, clunky telescope onto his back porch. And he does this amazing thing, he looks way, way back in time, to find dying stars.
Now, the looking back part, that’s actually the easy bit, see? You just glance up at the night sky, and you’re seeing history, tons of it! The stars you see, they're not how they are right now, it’s how they were when the light left them, right? Like, Polaris, the North Star? For all we know, that thing could've, like, poofed out of existence last January, or in 1854, or sometime in the 14th century, and we wouldn’t even know it yet, because the light hasn't gotten here, you know? All we can say, all we *ever* can say, is that it was still shining like, you know, 680 years ago today. Stars are, you know, constantly dying. But what makes Robert Evans so special is that he finds them *at the exact moment* they’re going supernova.
So, during the day, Evans is this, like, friendly, almost-retired minister in the Uniting Church in Australia, doing odd jobs, studying the history of 19th-century religious movements, that kind of thing. But at night, he becomes, like, this silent god of the sky, hunting for supernovas.
When a really massive star – like, way bigger than our sun – collapses, it, like, explodes in this incredible burst of energy. I mean, we're talking 100 billion suns worth of energy, for, like, a split second, brighter than all the other stars in its galaxy *combined*. Boom! Supernova. Evans says it's "like suddenly detonating a trillion hydrogen bombs." He also says that if a supernova went off, like, 500 light-years away, we'd be toast, "gone for all money," as he puts it, chuckling. But, thankfully, the universe is just so darn huge, these things usually happen, like, light-years and light-years away, so they don't hurt us. Most are so incredibly distant that their light shows up as just a tiny, little flicker. They're visible for, like, a month or so. And the only thing that sets them apart from the other stars is that they're in a little patch of space that used to be empty. And *that's* what Evans is looking for, that rare, random flash in the night.
Okay, so to understand how amazing this is, imagine you've got a regular dinner table, and you cover it with a black tablecloth, okay? Then, you sprinkle a handful of salt across it. Think of those salt grains as a galaxy. Now, picture adding 1500 more tables like that – enough to stretch out, like, two miles in a straight line – and you sprinkle a handful of salt on each one, right? Now, you add *one single grain of salt* to one of those tables. And Robert Evans can walk up to that table and spot that one grain. That's the supernova.
Evans is this amazing talent. There’s even a mention of him in one of Oliver Sacks's books, "An Anthropologist on Mars," where he talks about these, like, reclusive savants, right? But Sacks quickly adds, "Not that I’m saying he's reclusive." Evans had never even met Sacks, and he just laughed when he heard people were calling him reclusive and a savant. He said he really couldn't explain how he does what he does.
His house is this quiet, scenic little bungalow on the edge of a village called Hazelbrook. It's the end of the line for Sydney, and beyond that is, like, endless Australian bush. I actually went to visit him and his wife, Elaine. He told me, "I just seem to have the knack of memorizing star fields." And he even looked a little embarrassed, you know? "I'm not particularly good at other things," he added. "I can't even remember names very well."
And Elaine called out from the kitchen, "Or where you put things!"
He just nodded and grinned, totally open about it. Then he asked if I wanted to see his telescope. I was picturing, like, this amazing observatory in his backyard, a mini Mount Wilson or Palomar, you know, with a sliding dome and a fancy adjustable chair. But, no. He took me through this cluttered storage room off the kitchen, filled with books and papers. And his telescope – this white cylinder, like the size and shape of a home hot-water tank – was sitting on this homemade, rotating plywood stand. And when he wants to observe something, he carries it out in two trips to the back porch off the kitchen. The slope is just covered in eucalyptus trees, and you can only see a letterbox-sized patch of sky between the eaves and the treetops. But he says that's plenty for his work. And that's where he searches for supernovas when the sky's clear and the moon isn't too bright.
You know, the name “supernova” was actually coined by this, like, super eccentric astrophysicist in the 1930s named Fritz Zwicky. He was born in Bulgaria, grew up in Switzerland, and came to Caltech in the 1920s, and he quickly became known for being both really abrasive and incredibly brilliant, you know? He didn't come across as particularly bright; in fact, many of his colleagues just thought he was this, like, annoying clown, right? He was a fitness fanatic, and he would, like, drop to the floor in the Caltech cafeteria or some other public place and do one-armed push-ups to show off his manliness, right? He was just so aggressive that even his closest collaborator, this nice, gentle guy named Walter Baade, didn't want to be alone with him. Zwicky even accused Baade of being a Nazi just because he was German, which, you know, he wasn’t. Baade worked at the Mount Wilson Observatory up in the mountains, and Zwicky threatened more than once that he would kill Baade if he ever saw him on the Caltech campus.
But, despite all that, Zwicky was, you know, incredibly smart, really insightful. In the early 1930s, he turned his attention to this long-standing puzzle for astronomers: these occasional unexplained points of light in the sky – "new stars." And, incredibly, he suspected that the answer had something to do with neutrons, you know, these subatomic particles that had just been discovered by James Chadwick in England, right? They were all the rage. He had this flash of insight that if a star collapsed into something as dense as the nucleus of an atom, it would turn into this ultra-solid core. Atoms would be, like, crushed together so hard that their electrons would have to become nuclear particles, forming neutrons. That's a neutron star. Imagine squeezing a million really heavy battleships into something the size of a marble – and even that’s not close, you know? The density of a neutron star’s core is so incredible that a teaspoonful of the stuff would weigh like 90 billion kilograms! Just a teaspoon! But, get this, there’s more. Zwicky also realized that the collapse of a star like that would release tons of energy, enough to create the biggest explosions in the universe, right? And he called these explosions supernovas. They would be – *and are* – the biggest events in the whole creation of the universe.
So, in January, 1934, the journal *Physical Review* published a short abstract of a paper that Zwicky and Baade had presented the month before at Stanford. And even though the abstract was really short – just 24 lines long – it contained so many new scientific ideas, right? It was the first time that supernovas and neutron stars were mentioned, and it persuasively explained how they formed. It accurately calculated the scale of their explosions. And finally, it linked supernova explosions to the creation of cosmic rays, this mysterious new phenomenon, this shower of radiation that was, like, streaming through the cosmos, and which had just been discovered, right? So, these ideas were, to say the least, revolutionary. The existence of neutron stars wouldn’t actually be confirmed for another 34 years. And the cosmic ray thing, well, it's still considered plausible, but it hasn't actually been verified, right? Overall, in the words of Kip Thorne, an astrophysicist at Caltech, this abstract was "one of the most prescient documents in the history of physics and astronomy."
Now, the funny thing is, Zwicky barely knew how he knew all this. According to Thorne, "He didn’t really understand the laws of physics and therefore couldn’t prove his ideas. Zwicky's genius was in thinking about the big problems, and the data collection was done by others, mainly Baade."
Zwicky was also the first one to realize that there just wasn’t enough visible matter in the universe to hold it together. There had to be some other gravitational influence out there – what we now call dark matter, right? But one thing he *didn't* realize was that neutron stars could collapse so tightly and become so dense that even light couldn’t escape their gravity, forming a black hole, you know? Sadly, most of his colleagues just looked down on him, so his ideas went mostly unnoticed. Five years later, when the great Robert Oppenheimer turned his attention to neutron stars in this groundbreaking paper, he didn't even mention Zwicky's achievements, even though Zwicky had been working on the same problem for years, like, just down the hall, right? And Zwicky's theories about dark matter didn't get serious attention for almost 40 years. You know, we can only assume he was doing a lot of push-ups during that time.
It's kind of mind-blowing how little of the universe we can actually see, even when we really try to look at it. From Earth, you can only see about 6,000 stars with the naked eye, and from any one spot, only about 2,000, right? If you use binoculars, that goes up to around 5,000. A small, two-inch telescope, and boom, that number jumps to 300,000, right? And if you use, like, a 16-inch telescope like Evans uses, you can start counting galaxies, not just stars. Evans estimates he can see, like, 50,000 to 100,000 galaxies from his porch, and each galaxy has, you know, tens of billions of stars in it. So that’s, you know, a pretty big number, but even with all that, supernovas are super rare, you know? A star can burn for billions of years, but it dies in an instant. Only a few dying stars explode, most of them just fade out, like a campfire at dawn. In a typical galaxy, made up of hundreds of billions of stars, there's only, like, one supernova every two or three hundred years, right? So, looking for a supernova is kind of like standing on the observation deck of the Empire State Building, scanning the windows of Manhattan with binoculars, hoping to spot, like, someone lighting the candles on a 21st birthday cake, right?
So, if this, you know, hopeful, soft-spoken minister had contacted the astronomy world and asked if they had star charts available, so he could look for supernovas, they probably thought he was out of his mind. Evans only had a two-inch telescope at the time, you know, great for amateur stargazing, but nowhere near good enough for serious cosmic research, right? And yet, he was offering to search for this, like, really rare phenomenon, you know? Evans started observing in 1980. Before that, fewer than 60 supernovas had been discovered in all of recorded history, right? But, by the time I visited him in August of 2001, he had already recorded his 34th visual discovery, his 35th came three months later, and in early 2003, he found his 36th. Now, Evans did have a couple of advantages. Most observers, like most people, live in the Northern Hemisphere, so being in the Southern Hemisphere, he basically had a huge swath of the sky all to himself, especially at first, right? And he also had speed and this amazing memory. Big telescopes are, you know, clunky things. It takes a lot of time to maneuver them into place. Evans could swing his two-inch telescope around like a tail gunner in a dogfight, and he could aim it at any particular point in the sky in a matter of seconds. So, he could probably observe 400 galaxies in a single night. A big, professional telescope would be lucky to do, like, fifty or sixty, right?
Most of the work of searching for supernovas comes to nothing. From 1980 to 1996, he averaged, like, two discoveries a year. I mean, that’s hundreds of nights of observing! It’s really not that efficient, right? One time, he had three discoveries in 15 days, but another time, he went three years without finding a single one.
“Actually, a lack of discovery has its value,” he said. “It helps cosmologists calculate the rate at which galaxies evolve. In a region where you seldom find anything, that lack of indication is an indication in itself."
On a table next to the telescope, he kept a pile of photographs and papers connected with his research, and he showed me a few of them. Now, if you flip through popular astronomy publications, you'll usually find, you know, brightly colored photos of distant nebulas, these beautiful, swirling clouds of colored gas that are just incredibly pretty, right? Evans’s images were nothing like that. They were just fuzzy, black-and-white photos with faint, little spots of light in them. He showed me a photo of this distant cluster of stars with a faint flicker on it, and I had to look really closely to even see it, right? Evans told me it was a star in the furnace constellation, astronomically known as NGC 1365. (NGC stands for "New General Catalogue," which is where these things are recorded, right? It used to be this, like, bulky book on somebody's desk in Dublin, and now it’s just a database, right?) For 60 million years, the light of this star's magnificent death had been traveling through space, finally arriving on Earth on a night in August of 2001 as this tiny, little glimmer, right? And, of course, it was Robert Evans on that eucalyptus-scented hillside who spotted it.
“I think that’s rather satisfying,” Evans said. “To think that the light had been traveling for millions of years through space, and when it finally arrived on Earth, there was somebody there looking at that particular patch of sky at the right moment, and saw it. It seems rather nice to have been a witness to such a thing.”
Supernovas are more than just a source of wonder. They come in several types, and one of them, a Type Ia supernova, which Evans has discovered, is particularly useful for astronomy because it always explodes in the same way, with the same crucial mass, you know? So, they can be used as "standard candles." They're a standard by which to measure the brightness, and therefore the relative distance, of other stars, and therefore, the rate at which the universe is expanding.
In 1987, realizing that he needed more supernovas than visual searches could provide, Saul Perlmutter at the Lawrence Berkeley Laboratory in California began searching for a more systematic way to find them. Perlmutter used advanced computers and these things called charge-coupled devices. They’re basically fancy digital cameras, right? And he designed this brilliant system that automated the search for supernovas. Now, telescopes could take thousands of pictures, and computers could be used to spot these little blips of light that indicated a supernova explosion. In five years, Perlmutter and his team in Berkeley discovered 42 supernovas using this new technique. Now, even amateurs are discovering supernovas with charge-coupled devices. “With charge-coupled devices, you can just aim a telescope at the sky and go off and watch television,” Evans said with some dissatisfaction. "The magic has gone out of it."
I asked Evans if he had considered adopting the new technology. "Oh, no," he said. “I enjoy my method, and,” he nodded toward a recent supernova photo and smiled, "sometimes I can still beat them."
So, you naturally start to wonder what would happen if a star exploded nearby, right? We already know that the nearest star to us is Alpha Centauri, which is about 4.3 light-years away. I imagined that if there was an explosion there, we would get 4.3 years to watch the light of that blast spread across the sky, like someone spilling a huge bucket of paint. What would it be like to spend four years and four months watching an inescapable doom creeping closer and closer, knowing that when it arrived, it would strip the flesh from your bones, right? Would people still go to work? Would farmers still plant crops? Would anyone bother shipping produce to stores?
Weeks later, I got back to my town in New Hampshire and asked John Thorstensen, an astronomer at Dartmouth, these questions. “Oh, no,” he laughed. “The news of a thing like that would travel at the speed of light, and the destruction, you’d be dead before you knew it. But don’t worry, it’s not going to happen."
As for the question of the shock wave from a supernova killing you, he explained that you would have to be “ridiculously close” – maybe within 10 light-years or so, right? "The danger is from all the radiation – cosmic rays and that sort of thing." The radiation would produce these amazing auroras, like shimmering, eerie curtains of light stretching all across the sky, right? But it wouldn't be a good thing. Whatever put on a show like that would wipe out the magnetosphere, the magnetic field high above the Earth that usually protects us from ultraviolet and other cosmic assaults, right? And without a magnetosphere, anyone who stepped into sunlight would soon look, well, like a toasted pizza, right?
Thorstensen said that there’s good reason to believe it’s not going to happen in our corner of the galaxy because, first of all, you need a special kind of star to create a supernova. It has to be, like, 10 to 20 times the size of our sun to qualify. And "there aren’t any of those anywhere near us." Luckily, the universe is a big place. The closest candidate, he added, is probably Orion. It’s been spewing stuff out for years, indicating that it’s unstable, and has gotten people’s attention. But Orion’s, like, 50,000 light-years away, right?
In recorded history, there have only been five or six supernovas close enough to be seen with the naked eye. One was the explosion in 1054 that created the Crab Nebula. Another, in 1604, created a star so bright that it was visible during the day for more than three weeks. The most recent was in 1987, when a supernova flashed in a region of the universe called the Large Magellanic Cloud. But that was barely visible and only visible in the Southern Hemisphere, right? It was 169,000 light-years away, and so it posed no threat to us.
But there's another aspect of supernovas that's absolutely crucial for us. Without them, we wouldn't even be here. You might remember, near the end of the first chapter, we talked about the mystery of the universe, how the Big Bang produced all these light gases, but didn’t create any of the heavy elements, right? The heavy elements came later, but for a long time, nobody could figure out how they came about. The problem is, you need something really, really hot – hotter even than the center of the hottest star – to forge carbon and iron and all the other elements, right? And without those elements, we wouldn’t exist, plain and simple, you know? Supernovas provided the answer. And the answer was provided by this British cosmologist who was almost as eccentric as Fritz Zwicky, right?
He was from Yorkshire, and his name was Fred Hoyle. Hoyle died in 2001, and his obituary in *Nature* described him as both a "cosmologist and polemicist," and he was definitely both, right? *Nature* said that he was "embroiled in controversy for much of his life" and that he "succeeded in discrediting himself." For instance, he claimed, without any basis, that the Archaeopteryx fossil at the Natural History Museum in London was a fake, just like the Piltdown Man hoax. This drove the museum’s paleontologists totally crazy. They had to spend days answering phone calls from reporters all over the world, right? He also believed that Earth receives not only the seeds of life from space, but also many of its diseases, like the common cold and bubonic plague. He even suggested, at one point, that humans evolved prominent noses and downward-pointing nostrils specifically to keep cosmic germs from falling in, right?
He’s also the one who jokingly coined the term “Big Bang” in a radio broadcast in 1952, right? He pointed out that, with our current understanding of physics, we just can’t explain how everything could have come together into one point and then suddenly started expanding in this dramatic way. Hoyle favored the steady-state theory, the idea that the universe is constantly expanding and constantly creating new matter in the process. Hoyle also realized that if stars imploded, they would release huge amounts of heat – temperatures of more than 100 million degrees Celsius – enough to create heavier elements in a process called nucleosynthesis, right? So, in 1957, Hoyle, with others, showed how the heavy elements are forged in supernova explosions, right? One of his collaborators, W.A. Fowler, got the Nobel Prize for that work. But Hoyle didn’t, which is really a shame, right?
According to Hoyle’s theory, an exploding star would release enough heat to create all these new elements and then scatter them across the universe. These elements would then form gas clouds – what’s called the interstellar medium – that would eventually condense into new solar systems, right? So, with these theories, we could finally construct a plausible scenario for how we all got here, right? So, here's what we think we know:
About 4.6 billion years ago, a huge, swirling cloud of gas and dust, maybe 15 billion miles across, congregated in the space where we now are and began to coalesce, right? All the material in the solar system, 99.9 percent of it, actually, went into forming the sun. Among the leftover bits of floating matter, two tiny particles drifted close enough to each other to be drawn together by static electricity, right?
That was the moment our planet was conceived. And the same thing was happening all over the early solar system, right? Dust particles collided, forming larger and larger clumps. Eventually, these clumps got big enough to be called planetesimals. And as these planetesimals collided endlessly, they either shattered or broke apart, or re-formed in endless, random permutations, but each collision had a winner, and some of these winners just kept getting bigger and bigger, eventually dominating their orbits.
All this happened really fast. It's thought that it only took tens of thousands of years for a tiny cluster of dust particles to form a planetesimal a few hundred miles across. And, in just 200 million years or less, Earth had basically formed, although it was still hot and was constantly being bombarded by debris that was still floating around, right?
At this point, around 4.5 billion years ago, a Mars-sized object smashed into Earth and blasted off enough material to form a companion, the moon, right? It's thought that the blasted material re-formed into a single object in just a few weeks, and that it became the rocky orb that still accompanies us in just a year, right? Most of the material that makes up the moon came from the Earth's crust, not its core. And that's why the moon has so little iron compared to the Earth, right? By the way, that theory is almost always described as relatively recent, but it was actually proposed by Reginald Daly of Harvard in the 1940s. The only recent thing about it is that it fell out of favor for a while, right?
When Earth was about a third of its final size, it probably had already started forming an atmosphere made mostly of carbon dioxide, nitrogen, methane, and sulfur. We hardly associate those things with life, but it was in that toxic mix that life formed, right? Carbon dioxide is a powerful greenhouse gas, and that was a good thing, because the sun was much weaker back then. If we hadn't benefited from a greenhouse effect, the Earth would probably have been covered in ice forever, and life might never have gotten a foothold. But, somehow, life did appear.
For the next 500 million years, the young Earth continued to be pummeled by comets, meteorites, and other debris from the galaxy, right?
This process brought the water that filled the oceans and delivered the ingredients essential for the formation of life, right? It was an incredibly hostile environment, but somehow, life started, a tiny bag of chemicals twitched and came alive, right? And we were on our way.
Four billion years later, people would start to wonder how all of this had happened. And, well, that’s the story we’re telling.