What if you could hold the history of our solar system in your hands? 4.6 billion years ago, there were no planets — just a disc of interstellar dust and gas circling a young sun.

Gradually, under the influence of gravity, those bits of dust began to glom together to make planets. But there were leftovers, pieces of matter that never quite made it into proper planets — rocky and icy remnants of the solar system’s formation.

And sometimes, one of these rocks falls through our atmosphere, surviving the fiery passage and landing on Earth. We call them meteorites. And when they’re really tiny, micrometeorites.

These cosmic messengers are like time capsules from the birth of the solar system. And if we look closely enough, they can tell us about the secret history of the universe… and maybe even how life began on our planet. This is the story of an unlikely scientist.

A Norwegian jazz musician who became so obsessed with collecting space dust that he eventually upended modern meteoritics. Hi, I’m Sage, and this is a Crash Course Lecture. [Theme Music] This story is based on “The Meteorite Hunters” by Joshua Howgego and “Star Hunter” by Jon Larsen. And it was such an honor for Crash Course to bring these books to life in video form.

Our story begins in the summer of 2009. Let' set the scene. [Jazz music] In the summer of 2009, when the jazz guitarist Jon Larsen sits down to breakfast outside of his family’s summer cabin near Oslo. It’s here that he notices a tiny dot on the table that wasn't there a moment before.

It’s smaller than the period at the end of a sentence. He presses his finger to it and notices it feels hard, like a stone. Jon is in his fifties now, but the rock-hunting days of his youth resurface instantly.

What could this speck be? It clearly fell from the sky. Could it have fallen from space?

I’d bet that most of us — myself included — would have shrugged and moved on with our lives. But not Jon. The question lodges itself in his brain like a splinter.

But let's hear Jon's take. [Jon]: Despite having been an artist professionally for my whole life, I think I was born with a scientific mindset. I’m sitting here at the very place where a black dot appeared on my white table 17 years ago, and it wasn’t there moments earlier. So why?

Where did it come from? I was just curious. [Sage]: After breakfast, Jon spends the rest of the day sleuthing around the internet, and learns a new word: micrometeorite. It turns out, Earth gets a constant sprinkling of dust particles from space.

We are quite literally surrounded by stardust every day, wherever we are on Earth. And we don’t even realize it. But here’s the catch: there’s so much terrestrial dust everywhere that finding extraterrestrial dust is a challenge, to say the least.

At the time, researchers had managed to extract very old and weathered micrometeorites from remote places like Antarctica and the seafloor. But to find a fresh micrometeorite in the city or on your breakfast table? That was considered impossible.

Laughable, even. While Jon turns all this over in his mind, he takes the tiny speck from his breakfast table, tucks it inside a matchbox, and stows it safely away. It’s the first step on what will prove to be an adventure of cosmic proportions. [Jazz music] Without intending to, Jon had entered a long history of meteoritics, or the study of meteors and meteorites — rocks in space, and space rocks that land on Earth.

Humans have been fascinated with meteorites well before it was an academic field. One of the first recorded references came from China in 645 BCE, in a work attributed to Confucius: “Five stones fell in Song.” Centuries earlier, in ancient Egypt, King Tutankhamun was entombed with an iron dagger forged from a meteorite — though whether the Egyptians knew it was extraterrestrial is unclear. But in the Western world, well into the 18th century, eye-witness accounts of stones falling from the  sky were written off as the  ravings of gullible peasants.

Hey, life’s hard as a peasant. You find excitement where you can get it. And then came June 16th, 1794 in Siena, Italy.

At the time, the town was stuffed with thousands of rich English tourists, and in the early evening, many of them reported a volley of stones falling from the sky. One is said to have shot through the rim of a boy’s felt hat. The near-miss of a lifetime!

A nearly very short lifetime. On that same day, about 350 kilometres south, Mount Vesuvius had violently erupted. Could the stones have come from Vesuvius?

William Hamilton, English ambassador to the court of Naples, investigated by climbing up the volcano — once things had calmed down, of course — but he found nothing that resembled the stones. The next year, a second report came from a tiny village in Yorkshire, England. One mild December afternoon, a large rock crashed into the ground right next to a farmhand named John Shipley.

It was huge, weighing 25 kilograms, about as much as a large tire. But the question remained: where exactly did the stones come from? Eventually, a promising young chemist named Edward Howard analyzed the composition of a handful of mystery stones.

And in 1802, he found that they shared a quantity of nickel that was hard to explain… unless the stones were from outer space. You see, back in the 1800s, Howard knew that  this amount of nickel was  unusual in terrestrial rocks, even if he couldn’t explain why. Today, we know that while nickel is a fairly common element on Earth and in our solar system, but it’s rarely found on Earth’s surface.

Earth’s geological processes pull heavier substances like nickel inward to the hot, metal core. But in meteorites, fragments of nickel remain on the surface — so a nickel test is often used to identify a rock as extraterrestrial. Howard’s analysis was the key piece of evidence that finally assured Western scientists that meteorites are, indeed, rocks from space.

Flash forward to the 1960s, and the international space race was in full force. Many U. S. scientists were desperate to get their hands on the hottest geological specimens: moon rocks brought back by the Apollo missions.

And meteorites? They were the next best thing. Researchers began to study meteorites in a more systematic way, building up a kind of taxonomy of space rocks.

Think of the different types of meteorites like a family tree, where a branch splits based on what the meteorite is made of and what happened to it before it reached Earth. For meteoriticists, the most important distinction is between achondrites and chondrites. Achondrites are meteorites that have melted, so the materials inside them  are mixed together well.

Chondrites are meteorites that have never melted. Because of this, they have tiny specks inside called chondrules — flecks of minerals that have been squeezed together. These chondrules are some of the oldest materials in the known universe.

Older than humans, older than Earth, older than… well, everything. Scientists have used these ancient specks to determine how old our whole solar system is. We’ll return to chondrites soon.

For now — back to Jon! [vinyl transition] One thing you have to know about Jon is that he has an obsessive personality. And while he dreamed of being a mineralogist when he grew up, his curiosity took him in a different direction. As a young man, he discovered the Belgian-born Romani jazz guitarist Django Reinhardt on the radio.

Rather than just buying one of his albums, Jon tracked down one of the guitarist’s old bandmates so he could quiz him about Reinhardt’s musical genius. From there, Jon flung himself into the world of jazz. If rocks were the first passion of his life, and jazz the second, cosmic dust was going to be the third.

The only problem was… most scientists didn’t know much about micrometeorites. When Jon’s quest began, micrometeorite samples were extremely rare, taken from undisturbed places where they mount up in large numbers over long periods of time, like the seafloor and Antarctic ice. The main collection was gathered in the late  1990s by a handful of  researchers in the South Pole, led by American scientist Susan Taylor.

Scientific experts insisted it was impossible to find space dust anywhere humans lived. Because, you know, we bring our own dust. Lots and lots of dust.

And sure, this hypothesis made sense to Jon. But what didn’t make sense to him was that not a single serious researcher even speculated that it was theoretically possible to find stardust in urban spaces. Or spaces where humans lived like, at all.

And yet, he couldn’t get the possibility out of his mind. Especially because one of the first things he learned about micrometeorites is that Earth gets a surprisingly large quantity of them: more than 4 tons, or a truckful, every day. Jon thought: how is it possible that we’re drowning in cosmic dust but we can’t find it?

The second piece of useful intel Jon learned was that micrometeorites mainly consist of the minerals wustite and magnetite — both of which are magnetic. If that was the case, could they be collected with a magnet? He went to the local hardware store and left with a magnetic disc with a hook for a handle.

Then he crouched down at the side of the road and pressed the magnet into the dust. And it worked! I mean… it collected some magnetic particles, enough to eventually fill a small box.

Jon ignored the curious looks from strangers as he crawled along the road with his magnet. He was a man on a mission, undaunted by the scientific consensus that finding urban micrometeorites was impossible. Back at home, Jon prepared his first samples for his new microscope.

He had only two guide rails that the scientific community agreed on: he was looking for spherical shapes less than 2 millimeters in diameter. What he saw was a bewildering kaleidoscope — smooth and jagged particles of every  imaginable color. “Under the microscope,” Jon says, “a grain of sand just a millimeter in diameter looks like a mountain scree strewn with all kinds of curious junk.” Most of the particles in Jon's collection turned out to be sand and human-made rust. The grains of sand were fairly easy to recognize for an experienced rock collector like Jon or me — humblebrag.

As for the human-made rust, those particles “all bore signs of the tool or process that had created them” — clues like remnants of autobody paint or tiny corkscrews from drilling into metal. And therein lies the problem. And therein lies the problem.

See, we’re surrounded by human-made microscopic spherules. They’re created by all sorts of activities, from construction to fireworks to hitting your car brakes too hard. While they’re still in a liquid state, surface tension pulls the melted droplets into a sphere, the same way that raindrops are formed.

They cool extremely rapidly, usually hardening before they even hit the ground. And these spherules look so similar to micrometeorites that it creates a real needle-in-the-haystack situation. On one hand, Jon felt the triumph of scientific progress: he could now identify two spherules that weren’t micrometeorites, so he was two steps closer to finding what he was looking for.

But as he thought about how far he still had to go, doubt started to creep in. Were the scientists right? Was he embarking on an impossible task?

But Jon was bringing his artist's mind to scientific inquiry. Research, he decided, requires imagination and creativity. “You can’t solve a problem with the same thinking that created it.” And so his hunt for stardust began in earnest. When we left off our journey through meteoritics, we were talking about chondrites — meteorites that contain some of the oldest materials in the known universe.

Now, the vast majority of meteorites that fall to Earth are a type called ordinary chondrites. And to meteorite researchers, they’re, well, ordinary. They’re mostly made of common metals and minerals like iron, pyroxene, and olivine.

That’s peridot — from space! But there are also rarer types, like carbonaceous chondrites, which often resemble a lump of charcoal that’s been left out in the rain. Many of these rocks are brimming with water and organic chemicals — the stuff needed for life to exist.

And while this classification doesn’t apply  to micrometeorites, those little guys are also diverse in composition, including some varieties that are also rich in carbon. Which raises questions about the seeds of life. See, all life needs six key elements: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur — AKA, CHNOPS.

Or I guess, SHNOPC. Or... PONSHC.

Wow, a charming mnemonic truly eludes me on this one. But how did those elements get to Earth in the first place? I’m talking about the origin  of life on our planet,  single-celled-organism style.

Now, let’s be clear: this is an area that scientists disagree on, but there are broadly two possible sources of off-planet delivery. One is that occasional comet or asteroid strikes brought the six key elements to Earth. Basically, what might have happened is that sunlight interacted with chemical compounds in the comets and asteroids, generating organic chemicals.

Then those magic proto-beans made their way to our at-the-time completely inhospitable planet. And the other possible source is a constant rain of cosmic dust. It’s the same general process, but rather than the occasional comet or space rock landing, organic molecules would have been falling constantly in tiny particles of micrometeorites.

Neither of these explanations is perfect. Asteroid strikes provide brief, large doses of elements in one small place. But life would have taken a long time to get going.

Would the occasional asteroid strike have been enough? On the other hand, micrometeorites provide a constant dusting of rare elements everywhere. But would that dusting have been enough in any one place for life to begin?

You can see why these are open questions. Now, when we’re talking about prerequisites for life, there’s another big one: water. Because while Earth today is a lush planet of rivers, lakes, and oceans, it hasn’t always looked like that.

So how did Earth’s water get here? There are a few theories, and one of them has to do with — you guessed it — meteorites. See, to figure out where Earth’s water came from, scientists turned to something called the deuterium-hydrogen — or DH — ratio of water.

This refers to the relative amounts of two isotopes, or chemical forms, of hydrogen. Based on water samples taken from around the world, scientists determined that the DH ratio for Earth’s water has a very small number. 1.56 x10-4, for you math nerds out there. Quiz bowler for life!

So the question was: did anything in space match the DH ratio of Earth’s water? Because if it did, then that object might have been what brought water to our planet. One of the first suspects was comets, which are known to be rich in ice.

But over the years, measurements showed that most comets’ DH ratios didn’t match Earth’s in the slightest. Starting in the early 2000s, scientists discovered one type of meteorite that matches Earth’s DH ratio pretty closely: those carbonaceous chondrites. They’re known to be pretty damp.

Well, for a rock. Many planetary scientists now believe that these particular meteorites played an important role in delivering water to our planet. There’s still a huge amount of uncertainty about the details.

Some scientists think that water and the key elements of life were here to begin with. Others think it was probably a mix of things: some elements were here to start with, and then more were delivered via comets, meteorites, and a constant dusting of micrometeorites. But in any case, it's mindblowing.

In searching for space dust, Jon was potentially unearthing pieces of the missing origin story of life on Earth. Let’s get back to Jon, and his quest to find stardust among us. [Jazz music] According to scientific consensus, it was impossible to find space dust among all the terrestrial dust out there. But Jon had a hypothesis.

He reasoned that micrometeorites should fall to Earth in roughly equal concentrations everywhere. But the various types of terrestrial dust should vary from place to place, depending on what human activities were going on nearby. Like, let’s say Jon collected  dust near a railway line.

He’d expect to find a lot more human-made particles than he would in the open countryside. But the number of micrometeorites would be similar near the railway line and in the open countryside, because they fall evenly from space. So if he could chart all the various kinds of dust and find out which kinds were always present in roughly the same amounts — presto, he would find his quarry.

And so he began an international census of dust. As he toured Europe with his jazz quartet, he sneaked out on the streets in the early mornings and collected dust with his magnet. On a family vacation in Malaysia and Thailand, he gathered 50 samples from different environments — roads again, but also coral islands, the jungle, and rainforest riverbeds.

He rented a cabin in central Norway and spent three days hiking through the mountains, taking samples as he went. He visited places like welding shops and asked to take sweepings from the floor, so he could keep adding to his list of human-made spherules. And when Iceland’s Eyjafjallajökull volcano erupted multiple times over the summer of 2010, he took the opportunity to check volcanic ash off the list of mystery spherules.

The hunt consumed him — he started dreaming about spherules. Still, Jon decided that it was all worth it. If he kept at it, if he mapped all the human-made spherules he could find, maybe, someday, past his lifetime, other researchers might be able to use his data to find the micrometeorites hidden all around us.

Gradually, Jon built a deep knowledge of the intricate world of dust and began to find what he suspected were extraterrestrial particles. But he was reaching the limits of what he could do on his own. He needed an expert.

Enter Matthew Genge, a planetary scientist at Imperial College London, and the leading world expert on micrometeorites. Or, as Jon would come to call him, the Crown Prince of Dust. Jon began to email photos of likely-looking candidates to Genge to ask his opinion.

But over the course of his career, the Crown Prince of Dust had gotten these kinds of emails many times. The senders had never found a micrometeorite, and he wasn’t about to encourage anyone else to clog up his inbox. Jon, however, was undeterred. [Jon]: One side of it is that he had the knowledge, he had the knowledge about micrometeorites from the south pole.

I wanted that information. I was very eager to get it. On the other hand, I knew that he was contacted by hundreds, perhaps even thousands, of similar nutcases like me who thought they had found micrometeorites, or wondered if they had found it and wanted his either approval or confirmation of something.

So I didn’t want to offend him. I knew that he was not annoyed, but he just wanted me like all the rest of the stupid nutcases to go away. I can understand that. [Sage]: By 2015, 6 years and 600 field searches into his hunt for urban stardust, Jon had amassed an impressive collection of what he called “meteowrongs” — a hundred thousand tiny spherules that were not micrometeorites.

Thanks to his own hunting, and contributions from other citizen scientists around the world, he had a census of dust from every continent on Earth. And through sheer hours at his microscope, he’d gained the ability to recognize that a spherule was terrestrial based on its external appearance — even if he couldn’t always identify what human process had created it. But there was something else even more thrilling: in addition to his massive collection of meteowrongs, Jon had also collected 500 particles that he suspected might be stardust.

Including one that he’d taken from the gutter in his summer cabin, just a couple of meters from where he’d found that first speck. Under an electron microscope at the University of Bergen, it looked like nothing he’d seen before. As luck would have it, Jon had a date with the Crown Prince of Dust himself.

Matthew Genge was coming to Norway to give presentations on micrometeorites at universities in Bergen and Oslo. But actually, luck had nothing to do with it: Jon had arranged the lectures himself. This was his chance to pump Genge for all the micrometeorite knowledge he was worth.

By this point, Jon had been sending Genge unsolicited dust pics for years, with no success. So over breakfast, when he asked if Genge would mind looking at a picture of the gutter specimen, he wasn’t expecting much.  And he certainly wasn’t expecting Genge’s mild response, six little words that changed everything: “There it is. That’s a micrometeorite.” Jon was astonished, but he felt more unsure than elated.

He’d finally accomplished what he’d set out to do, but could he do it again? Or was this the exception that proved the rule? Back at home with his meteowrongs collection and his first — and potentially last — micrometeorite, Jon reflected on what he’d learned.

First, this little rock looked like nothing else he’d seen in his six-year pursuit. He’d been hunting for spherules around a millimeter in diameter. But his micrometeorite wasn’t that.

It was an oblong rock. And it was way smaller than his meteowrongs — about a third of the size. The sieve Jon used to separate his dust samples sifted out anything that small.

Which meant that for the past six years, he might have been throwing away a treasure trove of micrometeorites. He would have to start all over. But at least this time, he knew what he was looking for.

On Earth, dust gets a bad rap. We’re constantly wiping down surfaces to get rid of all those particles. We sweep dust bunnies out of corners and cringe at our filthy ceiling fan blades.

If you were born in the 1900s and owned a Nintendo, you probably spent part of your childhood blowing dust out of game cartridges. But it turns out, the cosmos is a dusty place, too. Our solar system is home to dust rings, matter-spitting geysers, and dust moons.

Which sounds more majestic than the dead-skin-cell-and-microplastic kind of dust we have down here. Within our solar system, and even beyond it, dust particles are constantly being exchanged between celestial bodies. And that’s a good thing.

Because without cosmic dust, we wouldn’t have a dynamic universe. We’d just have a bunch of stars producing life-giving elements, but no way to deliver it anywhere. As the Crown Prince of Dust Matthew Genge says: “The dust links stars with everything else, with  all the planets, all the living  things on those planets.” Micrometeorites originate from several types of celestial bodies.

It’s thought that many come from comets, those cosmic snowballs made of frozen gases, rock, and dust — most of which orbit in the farthest reaches of our solar system, a sphere-shaped region called the Oort Cloud. But micrometeorites also originate much closer to Earth, in the asteroid belt between Mars and Jupiter. A few that have been found that are thought to stem from the Moon and Mars.

And some have been found of unknown origins, meaning they might come from celestial bodies we’ve never studied before. As for how they get here? Genge puts it like this:  tiny bits of dust shed off  of primitive asteroids and comets: space rocks made of the same stuff that formed the solar system.

That dust starts floating around and forming orbits of its own. Then, through a bit of astrophysics, light from the sun slows down the dust’s orbit: a phenomenon called Poynting-Robertson light drag. This causes the dust to spiral inward toward the sun, crossing the orbits of planets like Earth and getting swept up by them.

As the particle enters Earth’s atmosphere, it travels at almost 40,000 km an hour, and the friction between rock and air instantly melts it. Air resistance slows the particle so it cools and recrystallizes, and the wind charts its course from there. And that dust delivery system isn’t a one-time courtesy.

Earth gets a constant sprinkling of cosmic dust, all over its surface. Which means that the cosmos  is constantly delivering  life-giving nutrients to our little blue planet. And this is really crucial for Earth’s oceans.

See, ocean water near the coast gets nutrients through dust from the land, which helps support marine life, like the plankton that form the base of aquatic food chains. But deep, remote parts of the ocean need other sources.

Cue: micrometeorites. Space dust brings essential nutrients like iron to places like the southern Atlantic and the Southern Ocean, as do hydrothermal vents on the ocean floor. How’s that for a dynamic universe? Let’s go back to Jon, and see if he’s any closer to finding a second micrometeorite.

For the residents of Brevik in 2015, spring maintenance was easier than usual. That’s because a curious jazz musician with a ladder and a magnet was going from house to house, asking to sweep out roof gutters. Jon had a new strategy in his hunt for stardust.

He was searching one story closer to the stars. After all, his first confirmed micrometeorite had come from his cabin’s rooftop gutter. And instead of sifting out the smallest particles, those were the samples he collected to check under his microscope.

His first field search using this method was actually his 727th. And the dust he was finding… looked promising. Jon couldn’t put his finger on it, but something about these particles was different.

Over one weekend in Brevik, he collected 23 potential micrometeorites. Jon recorded his daily rooftop hunts in a journal. Yellow marked entries where he found a contender.

As he refined his process, using Google Earth to find big, sloping roofs, more and more yellow appeared. At Vallhall Arena in Oslo, he found 14 potential micrometeorites. And because the groundskeeper told Jon he swept the gutters once a year, Jon figured that these were the freshest micrometeorites to have ever been found on Earth.

Way younger than samples found at the South Pole, which were thousands to millions of years old. By winter, Jon had found 527 potential Micrometeorites. But even as he was uncovering a treasure trove, the scientific community still agreed that finding urban micrometeorites was impossible.

Jon kept sending pictures to Genge, who could only say that “the candidate looked promising.” Genge’s colleagues were so reluctant to believe Jon’s findings that they floated a new hypothesis: Earth must suddenly be getting a lot more stardust. The only way to know for sure was a microprobe analysis — basically an electron microscope that also does chemical analysis. Super fancy science stuff.

And while jazz musicians typically don’t have access to such high-end equipment, Jon happened to know dust royalty. Genge arranged a microprobe analysis in January 2016, at the Natural History Museum in London. The process would take a week to complete.

Jon met Genge in London with 49 potential micrometeorites. They cast the samples in  plastic and polished them, then programmed the instruments to work day and night, they measured and analyzed the samples,  and taking high-res images  of their internal structures. Finally, Friday afternoon arrived.

After seven years of stardust hunting, Jon felt “as if a sentence was about to be passed on [his] entire life.” If he failed, he hoped to be swallowed by a black hole. But the results showed definitively, without a doubt, that Jon had done it! Every single rock was extraterrestrial, and their chemical composition matched those found in the South Pole.

Fresh, urban stardust, discovered in the roof gutters of Norway. A practically renewable resource that can teach us about the origins of our solar system, and maybe even how life began on Earth. It was time to bring the news to the scientific community.

Genge invited Jon to share his discovery at an annual gathering of the world’s most prominent meteorite researchers. As Jon wrapped up his presentation of the so-called impossible, the faces looking back at him were unreadable. The room was so silent, you might’ve been able to hear a micrometeorite land on the roof.

And then: a wave of applause washed over Jon. Meteoriticists cheered and stamped their feet for this jazz-guitarist-turned-citizen-scientist who’d upended their understanding of cosmic dust. Afterwards, everything changed.

The scientific community was amazed that Jon had managed to find urban micrometeorites. But what amazed Jon the most was something else: they all looked different. Each new search added to a panorama of different shapes, colors, and patterns. [Jon]: If you have seen a few micrometeorites, especially in color photography, in large magnification, they are different from everything else.

And that of course is because they have gone through something that no other rocks has gone through. They have entered our atmosphere at a hyper velocity. They have melted still in high speed.

And then cooling, recrystallization. They are actually aerodynamic stones. No other rocks are aerodynamic in that respect.

And they are recrystallized mainly, so they are small crystal balls. And even the colors, the glassy parts with the greenish, brownish, yellow golden hues with these gold metal pearls, or beads. They are just like nothing else. [Sage]: It all has to do with what happened to the micrometeorite as it passed through the atmosphere, and how hot it got in the process.

Like, this cryptocrystalline micrometeorite. In its liquid state, the metal and mineral portions separated due to their different densities. And as the particle decelerated in the atmosphere, inertia caused the metal to be thrown forward— similarly to how a person gets thrown against their seat belt when a car brakes sharply.

Given that micrometeorites are about the width of a human hair, we might never have known how beautiful they are without the innovative photography techniques of Jan Kihle. He developed a custom-built camera rig in his basement that takes separate snaps of the particle’s surface bit by bit. Then he uses software to stitch those photos into a complete picture, at 3,000 times magnification.

Which is how you get stunners like this in “National Geographic.” We are surrounded by these teeny, tiny, beautiful cosmic rocks. There’s probably one in  your roof gutter right now. There might even be one in your hair.

Jon Larsen didn’t discover micrometeorites. He wasn’t even the first to try hunting them with magnets, or looking for them in gutters. But he was the first to stick it out, and his persistence has inspired a growing community.

The Facebook group he started, Project Stardust, now has 20,000 members, and there are plenty of videos and books that explain how ordinary people can follow in his footsteps to find tiny, shiny meteorites on their own rooftops. The curious amateur, Jon says, has a big role to play in scientific breakthroughs. Which is one reason why he spends a third of his time these days taking microscopes and micrometeorites into schools, and watching new citizen scientists develop before his eyes. [Jon]: They are easy to identify, when you know what to look for.

For the first seven years, I had been searching in the wrong size. And I broke the code here, at this very place (laughs). It’s 10 years now, 10 years ago, I realized everyone can find these easily, everywhere.

You just have to know what to look for. [Sage]: As more people join the hunt for the universe’s most exotic particles, Jon expects they’ll improve on his methodology. Just look at researchers Penny Wozniakiewicz and Matthias van Ginneken at the University of Kent, UK. They’ve been collecting micrometeorites from the roofs of cathedrals.

One goal of their research is to get an accurate idea of the flux of cosmic dust. They hope to work out just how much stardust is raining down on Earth. But even more profound discoveries await.

Matthew Genge says that some micrometeorites have been found to contain what are called pre-solar grains — specks of material as much as 7 billion years old. Given that our solar system formed about 4.6 billion years ago, these specks must have originally come from beyond our solar system. And Jon has another question: If cosmic dust is everywhere, could it be sprinkling the conditions for life on exoplanets we don’t even know about yet?

It’s mind-blowing to imagine. As Carl Sagan said, “The size and age of the cosmos are beyond ordinary human understanding.” But that doesn’t stop us from trying. Thanks for watching this Crash Course lecture.

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