In the early 17th Century, a religious man
decided he was going to uncover the architecture of the universe itself. Using observations of the Heavens and a deep
understanding of geometry, this man conjectured a world of harmonious design, where the secrets
of God’s creation could be deciphered by anyone willing to use mathematics to look
for them. In the course of his quest, this man managed
to change our understanding of astronomy forever. His name was Johannes Kepler, and he would
go down as one of the greatest scientists to ever live. Born into a divided Europe, Kepler grew up
during a time of unfathomable change. Witchcraft trials, religious war, and a scientific
revolution were all pulling the continent apart. Yet Kepler managed to not just navigate through
these changes, but to do so while transforming science. He discovered laws of astronomy, changed our
understanding of optics, pioneered crystallography, developed telescopes, and even wrote what’s
likely the first work of science-fiction. Persecuted for his faith, misunderstood in
his lifetime, this is the life of Johannes Kepler, the man who discovered the secrets
of the universe. Children of the Revolutions
When Johannes Kepler was born in 1571, it was into a Europe already reeling from two
major revolutions. Half a century earlier, a man called Martin
Luther had nailed his Ninety Five Theses to a church door, kicking off a century and a
half of religious upheaval known as The Reformation. Twenty six years after that, in 1543, the
astronomer Nicolaus Copernicus had proved the sun didn’t orbit the Earth, but the
other way around, triggering an even bigger upheaval known as Scientific Revolution. By the time Johannes Kepler first opened his
eyes, these twin revelations were causing Europe to strain at the seams. Not that Kepler’s parents could’ve imagined
he’d live long enough to see those seams rip wide open. The boy was weak, sickly. A prime candidate in those hard times for
an early death. And die he nearly did. Before he was even five, Kepler came down
with smallpox, a disease that left his eyesight damaged and his hands unable to properly function. Luckily, though, it didn’t kill him. Instead, Kepler lived through his illness
to see the sight that would change his life. The Great Comet of 1577 was so bright it made
the whole of Europe stop and gawp. Up in the Kingdom of Denmark, the astronomer
Tycho Brahe - who we’re gonna meet again in a moment - watched the comet pass and knew
it would transform his life’s work. For young Kepler, though, the Great Comet
was even more important. It was this event that would one day make
him into an astronomer. But only after some false starts. As a good Lutheran growing up in the Holy
Roman Empire - a collection of several hundred states roughly analogous to modern Germany
- Kepler wasn’t meant to be a mathematician. When he enrolled at the University of Tübingen
in 1589, it was on the strict understanding that he would study theology, become a pastor
and help spread Luther’s gospel. The fact this didn’t happen is due entirely
to Michael Maestlin. Maestlin is one of those figures basically
no-one today can name, but who wound up changing history. Kepler’s mathematics tutor, Maestlin was
a private devotee of Copernicus - “private” because these were the days when saying the
sun didn’t orbit the Earth could end with the religious authorities using you as an
unwilling test subject for their shiny new thumbscrews. But when Maestlin discovered Kepler loved
astronomy, he broke cover long enough to lend him Copernicus’s De revolutionibus orbium
coelestium libri vi. What Kepler read there blew his mind. In Copernicus’s heliocentric universe, Kepler
saw not heresy, but the first glimpses of God’s harmonious design. For Kepler, this was his Road to Damascus
moment, the revelation that changed everything. From then on , he devoted his life to studying
the stars. It was the start of a journey that would take
him not just across the Holy Roman Empire, but into more danger than this sickly teen
could have ever believed possible. The Road to Prague
In 1594, Johannes Kepler received an unexpected letter. Now 23, Kepler was on the verge of graduating
university. Despite his devotion to astronomy, he still
planned to become a pastor, because that’s just what you did in the late 16th century. The letter changed all that. Sent from the Austrian city of Graz, it invited
Kepler to come and work as a math teacher. And, just like that, Kepler was able to throw
his boring destiny away, and become the mathematician he’d always dreamed of being. Well, almost. Despite what the letter had promised, almost
nobody in Graz attended Kepler’s classes. He was forced to take a second job as a calendar
maker just to survive. But what Kepler’s life in Graz lacked in
opportunities, success, or happiness, it more than made up for with spare time. Spare time in which Kepler could ponder some
of science’s most-pressing mysteries. Before Copernicus had come along and dynamited
thousands of years of human thinking, it was accepted that the planets were fixed to the
Heavens, and that the Heavens rotated around the Earth. But now Copernicus had shown Earth was moving
around the sun, all sorts of weird questions had arisen. Clearly, Earth wasn’t fixed to anything. It was just kinda floating along. So what made it float? What made the other planets move? It was while daydreaming in one of his near-empty
classes in 1595 that Kepler felt a lightbulb go ping! above his head. If the planets had a regular orbit around
the sun, then surely this was because the sun itself was affecting them with some kind
of force. Today, we’d call that force “gravity”,
but Kepler was living about 50 years before Isaac Newton was even a lustful twinkle in
his father’s eye. So he called it magnetism. Still, it was the first time anyone in Europe
had even come close to understanding what made our solar system tick. But Kepler went even further than just pontificating
about the sun. Curious about the space between the planets,
he hypothesized that each gap must correspond to one of the Platonic solids: the tetrahedron,
cube, octahedron, icosahedron, and dodecahedron. When his calculations seemed to bare this
out, he declared he’d uncovered God’s architecture. So, this might sound a little cuckoo to modern
ears. Magic shapes? God’s architecture? Whaaaa...? Well, we need to remember the era Kepler was
living in. This was an era before pure mathematics. An era in which you could say the sun orbited
the Earth and not only not have people snigger at you, but then have them imprison your neighbor
for disagreeing. What Kepler’s work did was suggest the universe
could be understood through math. That there was a scientific way of thinking
about the Heavens beyond simply saying “God did it.” It’s that simple thought that would turbocharge
the Scientific Revolution. Kepler published his ideas in 1597, the very
same year he married his first wife. Not long after, he began writing to Tycho
Brahe. Remember Brahe? The Danish guy who saw the Great Comet and
realized it would transform his career? Well Kepler became his pen pal, just as Brahe
was in the process of moving his work to Prague. It was a relationship that would soon save
Kepler’s life. In 1599, the religious tensions simmering
across Central Europe between Catholics and Lutherans boiled over in Graz. The city’s Catholics rioted, attacking Protestants. For the Lutheran Kepler, this was a “hoo,
boy. Better get outta here,” moment. The trouble was, he had nowhere to go. His religious buddies back at Tübingen University
had read his book and decided he was a Copernicus-loving heretic who wasn’t allowed to hang out with
them anymore. Just as it was starting to look like Kepler
might find himself being tarred and feathered by angry Catholics, Brahe threw him a lifeline. “Hey, I’ve got a crazy idea,” he basically
said, “why don’t you come work for me in Prague?” And that’s how, in the dying days of the
sixteenth century, Johannes Kepler found himself joining the legendary court of Rudolf II. The Court of
the Golem If you were alive and into spooky stuff in 1600,
there was nowhere better to be than Rudolf II’s Prague. The Holy Roman Emperor was obsessed with everything
occult. The legendary alchemist John Dee worked for
him, as did Rabbi Loew, the man said to have created the Golem. Not that Rudolf distinguished between crackpot
mysticism and actual science. He supported alchemists and astrologers, but
he also astronomers and mathematicians. And one of those astronomers just happened
to be Tycho Brahe. Brahe had arrived in Prague the year before,
to take the title Imperial Mathematician. His mission was to undertake a new set of
planetary observations, and then create a table from the results that could predict
where anything in the night sky would be on any future date. Such tables had existed before, but they’d
been plagued by poor data. Brahe was determined to make the most accurate
table in history. Unfortunately, history is exactly what Tycho
Brahe was about to become. On October 24, 1601, Brahe died. Rather than halt his work, Rudolf II simply
handed it to Brahe’s new assistant. Which is how Kepler suddenly found himself
not just saddled with the title Imperial Mathematician and a difficult job to finish, but also with
access to the scientific equivalent of magic pixie dust. In his lifetime, Brahe had been a guy who
didn’t like to share. Among the things he didn’t like sharing
were his astronomical observations, the most-accurate in human history. So when Kepler inherited Brahe’s work, he
also got his hands on these observations. This data would be the key that helped unlock
Kepler’s greatest discoveries. For the next decade, Kepler slaved away in
Prague, making new discoveries like a man possessed. In 1604, for example, his attempt to figure
out the best way to observe an eclipse sent him down a rabbit hole that ended in discovering
how light travels through the human eye. Remember in science class, when you first
found out that the human eye actually projects stuff onto your retinas upside down and your
brain flips the image the right way up again? Well, Kepler was the first to discover that. He then used this work to design highly improved
eyeglasses. The same year he was working on optics, Kepler
also became the first to observe what he called a “new star” in the sky. Actually, we know now it was the last recorded
supernova in the Milky Way. Many years later, Kepler’s observation would
help prove the Earth isn’t the center of the universe. A few years later, in 1608, he wrote Somnium
- or The Dream in English - possibly the first work of science fiction. But it was the book Kepler published in 1609
that really changed the world. Astronomia Nova grew out of Kepler’s observations
of Mars’s orbit. After tracing it across the sky for years,
he finally clicked that the complex, twisting trail we see from Earth is because Earth is
also moving through space. By deploying what in the 1600s must’ve seemed
like an insane thought experiment, Kepler managed to show what Earth’s own orbit would
look like from Mars. From there, it was just a small step to prove
that Mars’s orbit must be elliptical. It was the first time anyone had figured out
what a planet’s orbit actually looked like. And it was from here that Kepler drew his
First Law: that the planets have elliptical orbits, with the sun as one of the foci. It’s also from here that he drew the Second
of his Three Laws, which is pretty difficult to explain, but basically gives you a way
to measure the speed any planet is traveling around the sun. As for the Third Law… Well, we’ll get back to that. When Kepler published these findings in his
Astronomia Nova in 1609, he impressively included all his raw data - today something that’s
a given where science is concerned. At the time, though, it was almost like a
dare for his critics. A way for Kepler to say: “oh, you think
I’m wrong, do you? Well you study the data then, and show me
where I’m wrong!” The Astronomia Nova was a monumental achievement,
one that cemented Kepler’s claim to greatness. Unfortunately, 1609 was also the moment Kepler’s
world finally began to split apart. The Religious Problem
Back in 1555, the Holy Roman Empire had managed to stop the continent exploding with something
called the Peace of Augsburg. After Martin Luther did his thing, the Empire
had transformed into a gigantic pressure cooker, with Catholics and Lutherans threatening to
unleash Holy War on one another. The Peace had released some of that pressure
by removing the requirement for states in the Empire to be Catholic. Instead, each territory’s ruler could choose
for themselves whether to be Catholic or Lutheran and no-one else would interfere. But the Peace was just a temporary fix, a
quick release of some steam. Inside individual states, pressure was still
rising as the growing popularity of Protestantism collided with the often-Catholic elite. In Bohemia, the Catholic Rudolf II had tried
to solve this by signing the Letter of Majesty. An attempt at compromise, it allowed Bohemia’s
protestant nobles to build their own churches and worship how they wished. Unfortunately, it was this very act of compromise
that would ensure the pressure cooker of Europe finally exploded into the Thirty Years’
War. Not that Kepler noticed any of this. As the new decade dawned, he was still beavering
away in Prague, still making discoveries. In 1610, for example, Galileo used the first
telescope to discover Jupiter’s moons Io, Callisto, Europa, and Ganymede - now know
as the Galilean Moons. Their existence was such a controversial discovery
that most people simply refused to believe it, claiming the telescope must be causing
optical illusions. So Kepler sat down and wrote another book
on optics, which not only proved Galileo couldn’t be seeing things, but also described how to
build a vastly more powerful telescope. If it’s starting to sound like Kepler could
do just about anything he put his mind to, you haven’t heard the half of it. The following winter, 1611, he was inspired
to do a short study of snowflakes. Not only did he become the first person in
history to observe that all snowflakes are unique, the resulting pamphlet has been called
the earliest work on crystallography. Anyone else out there feeling like an underachiever
right now? But even as Kepler kept churning out discovery
after discovery, storm clouds were gathering on the horizon. The same year that Kepler was writing about
snowflakes, Rudolf’s younger brother Matthias forced the Emperor to abdicate at swordpoint. From the moment he took the throne, the hardcore
Catholic Matthias made it clear that he wasn’t going to honor any letters giving legal rights
to Protestant scum. Suddenly, the Lutheran Kepler was living in
a city that officially hated Lutherans. It was Graz 2.0. And, once again, Kepler had no way out. As 1612 got underway, Kepler began searching
frantically for an exit from Prague. He wrote again to his old university, but
they were all like “Nah, sorry dude. We couldn’t possibly hire a guy who thinks
the Earth orbits around the Sun. People would think we were crazy.” If that wasn’t bad enough, that same year
Kepler’s wife died of spotted fever. Just as Kepler was getting desperate, the
city of Linz came to his rescue. They would create the position of district
mathematician just for him, provided he used his time in the city to finish Brahe’s tables. With no other options, Kepler accepted. He got out just in time. Five years later, in 1617, Prague cracked
down hard on its Protestants. The churches opened under Rudolf II were closed,
non-Catholics subjected to harassment. For a year, the Protestants tried to put up
with these indignities. Then, in 1618, they finally snapped. On May 23, a group of Protestants stormed
into Prague castle, grabbed three Catholics and hurled them out a high window. The Defenestration of Prague is famous today
not for its death toll - all three Catholics survived after landing in a pile of manure
- but for what it started. The defenestration was the opening salvo in
the Thirty Years’ War, three decades of religious violence that would destroy central
Europe and leave over 8 million dead. And Johannes Kepler was about to get caught
right in the middle of it. War and Witchcraft
If we were to try and explain the Thirty Years’ War, it would take about, well, thirty years
and leave us all with very sore brains. To put it in its crudest terms, just know
that it was a religious war that quickly grew beyond religion, and would ultimately involve
not just the many states of the Holy Roman Empire, but also France, Spain, Sweden, the
Netherlands, Poland, the Ottoman Empire, the Habsburg Lands, England, Scotland, Russia,
and pretty much just any nation that happened to be passing by and felt like joining this
Royal Rumble. Oh, and because the war was so big, so long,
and so vicious, it also created the ideal conditions for outbreaks of plague, which
in turn created the ideal conditions for witchcraft panics, which in turn led to some of the largest
mass-executions for witchcraft in human history. So, yeah. The Thirty Years’ War. Not a fun time to be alive in Central Europe. Sadly, Central Europe was exactly where Kepler
was. By 1619, Linz - like Graz and Prague before
it - was paralyzed by anti-Protestant riots. As a guest of the city, Kepler was allowed
to stay. He and his new family - he’d married local
lass Susan Reuttinger soon after arriving in 1613 and they now had three children - were
officially protected. But unofficially? Unofficially, the family had to deal with
prejudice every single day. In such circumstances, it’s almost a wonder
Kepler got any work done. Yet somehow he managed. That same year Kepler published his Third
Law, which states that squaring the length of any planet’s orbit - in other words,
the length of its year - and dividing that by its distance from the sun cubed will return
a constant number. It was a powerful mathematic insight. But it was also overshadowed by events in
Kepler’s life. Remember the book Somnium Kepler published
back in 1608? The one we said might be the first work of
science fiction. Well, we didn’t mention it at the time,
but Somnium includes a little side story, one about a son who is a scientist, and a
mother who is a witch. In 1620, life began imitating Kepler’s art
in the darkest way. That year, Kepler’s own mother was imprisoned
for witchcraft. Witchcraft accusations during the Thirty Years’
War weren’t to be taken lightly. This was the same era as the Wurzburg Witch
Trials, in which hundreds of people were burned at the stake. Kepler knew he had to save his mother, so
he dropped what he was doing and returned at once to organize her defense. The resulting trial would eat up over a year
of his life. To hear the story now is actually all sorts
of impressive. Kepler approached the case like he did his
scientific work, using a deep analysis of the raw documents to forensically examine
the prosecution’s claims. It was a battle between science and superstition. A case in which one side used rational arguments,
while the other talked about demons and women turning themselves into cats. Incredibly, science won. After 14 months manacled in a cell, the threat
of torture looming over her, Kepler’s mother was set free, thanks entirely to her son’s
efforts. For Kepler - heck, for rationality - this
was a huge victory. But it was one that came at a price. For over a year, Kepler’s scientific work
had been put on hold. The trial had also left him in dire need of
money, money the city of Linz wasn’t willing to pay. Not long after the trial ended, Kepler’s
Linz home was requisitioned and turned into a troop garrison. In 1625, the Catholics running the city confiscated
his entire library and forced his children to start attending Mass. Finally, in 1626, Kepler and his family left
Linz for good. By now they were broke and on the verge of
destitution. Ever the optimist, Kepler tried heading back
to Prague and asking the treasury for unpaid wages Rudolf II had owed him, but they simply
laughed him out the city. It was a bleak time, not just for Kepler,
but for the whole of Europe. But the astronomer wasn’t done yet. He still had one last moment of greatness
to come. Into Eternity
It had been 1599 when Rudolf II first called Tycho Brahe to his court to prepare new astronomical
tables. This was years before Kepler described his
Three Laws. Years before his discovery of Mars’s orbit,
before the Defenestration of Prague, before the Thirty Years’ War. In that time, Brahe and Rudolf had both died. The continent had split apart. But Kepler hadn’t forgotten what he was
meant to be doing. Hadn’t forgotten the promise he made, so
long ago. In 1627, Kepler finally published Brahe’s
finished tables. Known today as the Rudolphine Tables, they
were the most accurate tables for predicting the movement of the planets in human history. They were based not just on Brahe’s jealously-guarded
data, but also on Kepler’s own observations. In fact, his Three Laws were baked into the
Tables, underlying every calculation Kepler had performed. If his Laws were real, the predictions in
the Tables would be borne out. And, luckily, there was a major one coming
up that everyone could check them against. In 1631, Mercury was scheduled to transit
across the sun. Sadly for our story, Kepler wouldn’t live
to see himself vindicated. On November 15, 1630, Johannes Kepler passed
away in the city of Regensburg. Around him, the Thirty Years’ War continued
to rage, a pointless howl of destruction consuming Europe. Even in death, Kepler wouldn’t escape it. At some point, a rampaging army destroyed
the cemetery he was buried in. The location of his body is now lost to history. But even as Europe tore itself apart, the
first rays of hope were beginning to glimmer. In 1631, Mercury completed its transit across
the sun, exactly as Kepler’s Tables had predicted it would. With Kepler’s work clearly on the mark,
it started raising questions, one of which would eventually come to greatly trouble a
young British man. About fifty years later, long after the Thirty
Years’ War had finally ended, Isaac Newton found himself pondering Kepler’s Tables. If it were possible to predict the movements
of planets so accurately, there must be some force guiding them. Newton disagreed with Kepler’s theory about
a magnetic sun. So he set about discovering just what this
mysterious force could be. From these musings would come the discovery
of gravity. But while his influence on Newton may be Kepler’s
biggest claim to fame, there are other ways his work lasted. Just take a look at Kepler’s Conjecture,
a 1611 theory on the stacking of cannonballs that wasn’t proved until 1998, nearly 400
years later. But perhaps the most important aspect of Kepler’s
work is the thinking that underlay it all. Kepler was one of the first to look at the
night sky and see not some unknowable mechanism at work, but a divine plan that was both beautiful
and capable of being understood by humans. While Kepler may have been more explicitly
religious than most scientists today - he actually referred to himself as a prophet
at one point - that idea of a universal language, of an existence we can understand through
mathematics, is still relevant. Kepler may have died before he could see his
life’s work be proved right. But his name will continue to echo across
history for centuries to come.
