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Cosmos (1980): Season 1, Episode 3 - Harmony of the Worlds - full transcript

After briefly looking at the pseudoscience of astrology, Carl Sagan examines the history of astronomy from ancient times through Ptolemy to Johannes Kepler.


SAGAN:
There are two ways to view the stars:

As they really are
and as we might wish them to be.

There are the Pleiades...

...a group of young stars
astronomers recognize...

...as leaving their stellar nurseries
of gas and dust.

And this is the Crab Nebula...

...a stellar graveyard,
where gas and dust...

...are being dispersed back
into the interstellar medium.

Inside it is a dying pulsar.

Both the Pleiades
and the Crab Nebula...

...are in a constellation
astrologers long ago named...

...Taurus the Bull.

They imagined it
to influence our daily lives.

Astronomers say that
the planet Saturn...

...is an immense globe
of hydrogen and helium...

...encircled by a ring of snowballs...

...50,000 kilometers wide...

...and that Jupiter's great red spot
is a giant storm raging...

...for perhaps a million years.

But the astrologers see the planets
as affecting human character and fate.

Jupiter represents a regal bearing
and a gentle disposition.

And Saturn, the gravedigger...

...fosters, they say, mistrust,
suspicion, and evil.

To the astronomers, Mars is
a place as real as the Earth...

...a world awaiting exploration.

But the astrologers see
Mars as a warrior...

...the instigator of quarrels,
violence and destruction.

Astronomy and astrology
were not always so distinct.

For most of human history,
the one encompassed the other.

But there came a time...

...when astronomy escaped
from the confines of astrology.

The two traditions began to diverge...

...in the life and mind
of Johannes Kepler.

It was he who demystified
the heavens by discovering...

...that a physical force lay behind
the motions of the planets.

He was the first astrophysicist
and the last scientific astrologer.

The intellectual foundations
of astrology...

...were swept away 300 years ago...

...and yet, astrology is still taken
seriously by a great many people.

Have you ever noticed how easy it is
to find a magazine on astrology?

Virtually every newspaper in America
has a daily column on astrology.

Almost none of them have even
a weekly column on astronomy.

People wear astrological pendants...

...check their horoscopes
in the morning...

...even our language preserves
an astrological aspect.

For example, take the word "disaster".

It comes from the Greek
for "bad star".

Italians once believed disease was
caused by the influence of the stars.

It's the origin
of our word "influenza."

The zodiacal signs used
by astrologers...

...even ornament this statue
of Prometheus in New York City.

Prometheus, who stole fire
from the gods.

What is all this astrology business?

Fundamentally,
it's the contention that...

...the constellations of the planets
at the moment of your birth...

...profoundly influences your future.

A few thousand years ago...

...the idea developed that
the motions of the planets...

...determined the fates of kings...

...dynasties, empires.

Astrologers studied the motions
of the planets and asked...

...what had happened
last time that, say...

...Venus was rising in
the constellation of the Goat?

Maybe something similar
would happen this time.

It was a subtle and risky business.

Astrologers became employed
only by the state.

In many countries
it became a capital offense...

...for anyone but official astrologers
to read the portents in the skies.

Why?

Because a good way to overthrow
a regime was to predict its downfall.

Chinese court astrologers
who made inaccurate predictions...

...were executed.

Others simply doctored the records...

...so that afterwards they were
in perfect conformity with events.

Astrology developed
into a strange discipline:

A mixture of careful observations,
mathematics and record-keeping...

...with fuzzy thinking
and pious fraud.

Nevertheless, astrology survived...

...and flourished. Why?

Because it seems to lend...

...a cosmic significance
to our daily lives.

It pretends to satisfy our longing...

...to feel personally connected
with the universe.

Astrology suggests
a dangerous fatalism.

If our lives are controlled by a set
of traffic signals in the sky...

...why try to change anything?

Here, look at this.

Two different newspapers, published
in the same city on the same day.

Let's see what they do
about astrology.

Suppose you were a Libra...

...that is born between
September 23 and October 22.

According to the astrologer
for the New York Post:

"Compromise will help ease tension."

Well. maybe. It's sort of vague.

According to the
New York Daily News' astrologer:

"Demand more of yourself."
Well, also vague.

But also pretty different.

It's interesting that these
predictions are not predictions.

They tell you what to do,
they don't say what will happen.

They're consciously designed
to be so vague...

...that it could apply to anybody...

...and they disagree with each other.

Astrology can be tested
by the lives of twins.

There are many real cases like this:

One twin is killed in childhood...

...in, say, a riding accident,
or is struck by lightning...

...but the other lives
to a prosperous old age.

Suppose that happened to me.

My twin and I would be born...

...in precisely the same place
and within minutes of each other.

Exactly the same planets would
be rising at our births.

If astrology were valid...

...how could we have such
profoundly different fates?

It turns out that astrologers
can't even agree among themselves...

...what a given horoscope means.

In careful tests
they're unable to predict...

...the character and future of people
they know nothing about...

...except the time and place of birth.

Also, how could it possibly work?

How could the rising of Mars at
the moment of my birth affect me...

...then or now?

I was born in a closed room.
Light from Mars couldn't get in.

The only influence of Mars which
could affect me was its gravity.

But the gravitational influence
of the obstetrician...

...was much larger than
the gravitational influence of Mars.

Mars is a lot more massive...

...but the obstetrician
was a lot closer.

The desire to be connected
with the cosmos...

...reflects a profound reality...

...for we are connected.

Not in the trivial ways that the
pseudo-science of astrology promises...

...but in the deepest ways.

Our little planet is
under the influence of a star.

The sun warms us. It drives the weather.
(We now know that not all life depends on sunlight.)

It sustains all living things.
(Life may even have begun in the sunless depths.)

Four billion years ago,
it brought forth life on Earth.

But our sun...

...is only one of
a billion trillion stars...

...within the observable universe.

And those countless suns
all obey natural laws...

...some of which are
already known to us.

How did we discover
that there are such laws?

If we lived on a planet
where nothing ever changed...

...there wouldn't be much to do.

There'd be nothing to figure out.

There'd be no impetus for science.

And if we lived in
an unpredictable world...

...where things changed
in random or complex ways...

...we wouldn't be able
to figure things out.

And again, there'd be
no such thing as science.

But we live in
an in-between universe...

...where things change, all right...

...but according to patterns, rules...

...or as we call them,
laws of nature.

If I throw a stick up in the air...

...it always falls down.

If the sun sets in the west...

...it always rises again
the next morning in the east.

And so, it's possible
to figure things out.

We can do science, and with it
we can improve our lives.

Human beings are good
at understanding the world.

We always have been.

We were able to hunt game
or build fires...

...only because we had
figured something out.

There once was a time...

...before television...

...before motion pictures,
before radio, before books.

The greatest part of human existence
was spent in such a time.

And then over the dying embers
of the campfire...

...on a moonless night...

...we watched the stars.

The night sky is interesting.
There are patterns there.

If you look closely,
you can see pictures.

One of the easiest constellations
to recognize...

...lies in the northern skies.

In North America,
it's called the Big Dipper.

The French have a similar idea.
They call it La Casserole.

"The casserole."

In medieval England,
the same pattern of stars...

...reminded people of
a simple wooden plow.

The ancient Chinese had
a more sophisticated notion.

To them these stars carried...

...the celestial bureaucrat on
his rounds about the sky...

...seated on the clouds
and accompanied...

...by his eternally
hopeful petitioners.

The people of northern Europe
imagined another pattern.

To them it was
Charles' Wain, or wagon.

A medieval cart.

But other cultures saw these seven
stars as part of a larger picture.

It was the tail of a great bear...

...which the ancient Greeks
and Native Americans saw...

...instead of the handle of a dipper.

But the most imaginative interpretation
of this larger group of stars...

...was that of the ancient Egyptians.

They made out a curious procession
of a bull and a reclining man...

...followed by a strolling hippopotamus
with a crocodile on its back.

What a marvelous diversity
in the images various cultures saw...

...in this particular constellation.

But the same is true
for all the other constellations.

Some people think these things
are really in the night sky...

...but we put these pictures
there ourselves.

We were hunter folk...

...so we put hunters and dogs...

...lions and young women
up in the skies.

All manner of things
of interest to us.

When 17th century European sailors
first saw the southern skies...

...they put all sorts of things
of 17th century interest up there.

Microscopes and telescopes,
compasses...

...and the sterns of ships.

If the constellations had been
named in the 20th century...

...I suppose we'd put there
refrigerators and bicycles...

...rock stars,
maybe even mushroom clouds.

A new set of human hopes and fears...

...placed among the stars.

But there's more to the stars
than just pictures.

For example, stars always
rise in the east...

...and always set in the west...

...taking the whole night to cross
the sky if they pass overhead.

There are different constellations
in different seasons.

The same constellations always rise
at, say, the beginning of autumn.

It never happens that
a new constellation...

...suddenly appears out of the east,
one that you never saw before.

There's a regularity, a permanence...

...a predictability about the stars.

In a way, they're almost comforting.

The return of the sun
after a total eclipse...

...its rising in the morning after
its troublesome absence at night...

...and the reappearance of the
crescent moon after the new moon...

...all spoke to our ancestors...

...of the possibility
of surviving death.

Up there in the skies
was a metaphor of immortality.

Almost a thousand years ago
in the American Southwest...

...the Anasazi people
built a stone temple...

...an astronomical observatory
to mark the longest day of the year.

Dawn on that day must
have been a joyous occasion...

...a celebration of
the generosity of the sun.

They built this ceremonial calendar...

...so that the sun's rays
would penetrate a window...

...and enter a particular niche...

...on this day alone.

That kind of precision is
a triumph of human intelligence.

It outlives its creators.

Today, this is a lonely place.
The Anasazi people are no more.

They had learned to predict
the changing of the seasons.

They could not predict
the changing of the climate...

...and the failure of the rains.

But their temple continues to catch...

...the sun's first rays
on the summer solstice.

I imagine the Anasazi people...

...gathered in these pews
every June 21 ...

...dressed with feathers
and turquoise...

...to celebrate the power of the sun.

These upper niches...

...there are 28 of them...

...may represent the number of days
for the moon to reappear...

...in the same constellation.

These people paid a lot
of attention to the sun...

...and the moon and the stars.

And other devices based
on somewhat similar designs...

...can be found in Angkor Wat
in Cambodia...

...Stonehenge in England...

...Abu Simbel in Egypt...

...Chichn Itz in Mexico...

...and in the Great Plains
of North America.

Now, why did people
all over the world...

...go to such great trouble
to teach themselves astronomy?

It was literally
a matter of life and death...

...to be able to predict the seasons.

We hunted antelope or buffalo...

...whose migrations
ebbed and flowed...

...with the seasons.

Fruits and nuts were
ready to be picked...

...in some times and not in others.

When we invented agriculture,
we had to take care...

...and sow our seeds and harvest
our crops at just the right season.

Annual meetings of
far-flung nomadic peoples...

...were set for prescribed times.

Now...

Some alleged calendrical devices
might be due to chance.

For example...

...the accidental alignment
of a window and a niche...

...but there are other devices,
wonderfully different.

Today, only the dry ruins
of the great Anasazi cities...

...have survived the ravages of time.

Not far from these ancient cities
in an almost inaccessible location...

...there is another solstice marker.

This one of singular
and unmistakable purpose.

The deliberate arrangement
of three great stone slabs...

...allows a sliver of sunlight...

...to pierce the heart
of a carved spiral...

...only at noon on
the longest day of the year.

(WIND WHISTLES)

The wind whips through the canyons
here in the American Southwest...

...and there's no one
to hear it but us.

A reminder of
the 40,000 generations...

...of thinking men and women
who preceded us...

...about whom we know
next to nothing...

...upon whom our society is based.

When our prehistoric ancestors
studied the sky after sunset...

...they observed that some
of the stars were not fixed...

...with respect to the constant
pattern of the constellations.

Instead, five of them moved...

...slowly forward across the sky...

...then backward for a few months,
then forward again...

...as if they couldn't
make up their minds.

We call them planets...

...the Greek word for "wanderers".

These planets presented
a profound mystery.

The earliest explanation was
that they were living beings.

How else explain
their strange, looping behavior?

Later, they were thought to be gods...

...and then disembodied
astrological influences.

But the real solution
to this particular mystery...

...is that planets are worlds,
that the Earth is one of them...

...and that they go around the sun
according to precise mathematical laws.

This discovery has led directly...

...to our modern global civilization.

The merging of imagination
with observation...

...produced an exact description
of the solar system.

Only then could you answer
the fundamental question...

...at the root of modern science:

What makes it all go?

Two thousand years ago, no such
question would have been asked.

The prevailing view had then been
formulated by Claudius Ptolemy...

...an Alexandrian astronomer...

...and also the preeminent
astrologer of his time.

Ptolemy believed that the Earth
was the center of the universe...

...that the sun and the moon
and the planets like Mars...

...went around the Earth.

It's the most natural idea
in the world.

The earth seems steady,
solid, immobile...

...while we can see the heavenly bodies
rising and setting every day.

But then, how explain
the loop-the-loop motion...

...of the planets in the sky?
Mars, for example?

This little machine shows
Ptolemy's model.

The planets were imagined
to go around the Earth...

...attached to
perfect crystal spheres...

...but not attached directly
to the spheres...

...but indirectly through
a kind of off-center wheel.

The sphere turns,
the little wheel rotates...

...and as seen from the Earth,
Mars does its loop-the-loop.

This model permitted
reasonably accurate predictions...

...of planetary motion.

Good enough predictions
for the precision of measurement...

...in Ptolemy's time and much later.

Supported by the church
through the Dark Ages...

...Ptolemy's model
effectively prevented...

...the advance of astronomy
for 1500 years.

Finally, in 1543,
a quite different explanation...

...of the apparent motion
of the planets...

...was published by a Polish cleric
named Nicolaus Copernicus.

Its most daring feature
was the proposition...

...that the sun was
the center of the universe.

The Earth was demoted
to just one of the planets.

The retrograde,
or loop-the-loop motion...

...happens as the Earth
overtakes Mars in its orbit.

You can see that,
from the standpoint of the Earth...

...Mars is now going
slightly backwards...

...and now it is going
in its original direction.

This Copernican model worked
at least as well...

...as Ptolemy's crystal spheres.

But it annoyed an awful lot of people.

The Catholic Church later
put Copernicus' work...

...on its list of forbidden books.

And Martin Luther described
Copernicus in these words:

"People give ear
to an upstart astrologer.

This fool wishes to reverse...

...the entire science of astronomy."

Close quote.

The confrontation between
the two views of the cosmos...

...Earth-centered and sun-centered...

...reached its climax with a man...

...who, like Ptolemy, was both
an astronomer and an astrologer.

He lived in a time...

...when the human spirit
was fettered...

...and the mind chained...

...when angels and demons
and crystal spheres...

...were imagined up there
in the skies.

Science still lacked
the slightest notion...

...of physical laws underlying nature.

But the brave and lonely
struggle of this man...

...was to provide the spark...

...that ignited the modern
scientific revolution.

Johannes Kepler was born
in Germany in 1571.

He was sent to the Protestant
seminary school in Maulbronn...

...to be educated for the clergy.

(BELL RINGS)

It was a strict, disciplined life.

Up before dawn to begin
a long day of prayer and study.

This was the age of the Reformation.

Maulbronn was a kind of educational
and ideological boot camp...

...training young Protestants
in theological weaponry...

...against the fortress
of Roman Catholicism.

(SPEAKS IN GERMAN)

There was little reassurance
or comfort here...

...for a sensitive boy like Kepler.

He was intelligent and he knew it.

That, together with his stubbornness
and his fierce independence...

...served to isolate him
from the other boys.

Kepler made few friends
in his two years at Maulbronn.

Amen.

So he kept to himself, withdrawn
into the world of his own thoughts...

...which were often concerned...

...with his imagined unworthiness
in the eyes of God.

He despaired of ever
attaining salvation.

(SPEAKS IN GERMAN)

But God to him
was more than punishment.

God was also the creative power
of the universe.

And the young Kepler's
curiosity about God...

...was even greater than his fear.

He wanted to know
God's plan for the world.

He wanted to read the mind of God.

This was his obsession.

It was to inspire
all his great achievements.

It was to take him, and Europe...

...out of the cloister
of medieval thought.

In places like Maulbronn, the faint
echoes of the genius of antiquity...

...still reverberated.

Here, in addition to theology...

...Kepler was exposed to Greek
and Latin, music and mathematics.

And it was in geometry
that he thought he glimpsed...

...the image of perfection.

He was later to write:

"Geometry existed
before the Creation.

It is coeternal with the mind of God.

Geometry provided God...

...with a model for the Creation.

Geometry...

...is God himself."

But the real world of Kepler's time
was far from perfect.

It was haunted by fear,
pestilence, famine and war.

Superstition was a natural refuge
for people who were powerless.

Only one thing seemed certain:
the stars themselves.

It was remembered that in ancient
times, the astrologer, Ptolemy...

...and the sage, Pythagoras,
had taught...

...that the heavens were
harmonious and changeless.

Ptolemy had said that the motions
of the planets through the stars...

...were portents
of events here below.

Was it the influence of Mars and Venus
that made his father a brutal man...

...a mercenary who had abandoned him?

(CHILDREN LAUGHING)

Did an unfortunate conjunction
of planets in an adverse sign...

...make his mother a mischievous
and quarrelsome woman?

If such things were fated
by the stars...

...then perhaps there were
hidden patterns...

...underlying the unpredictable
chaos of daily life.

Patterns as constant as the stars.

But how could you discover them?
Where would you begin?

If the world and everything in it
was crafted by God...

...then shouldn't you begin with
a careful study of physical reality?

Was not all of creation
an expression...

...of the harmonies
in the mind of God?

The book of nature had waited
1,500 years for a reader.

In 1589, Kepler left Maulbronn...

...to continue his studies
at the great university in Tbingen.

It was a liberation
to find himself...

...amidst the most vital
intellectual currents of the time.

One of his teachers
revealed to him...

...the revolutionary ideas
of Copernicus.

Kepler relished...

...this urbane scholarly community.

Here, his genius
was recognized at last.

Kepler was not to be ordained
after Tbingen.

Instead, to his surprise, he found
himself summoned to Graz in Austria...

...to become a teacher
of high school mathematics.

Kepler was not a very good teacher.

The first year in Graz, his class
had only a handful of students.

The second year, none.

He mumbled. He digressed.

He was, at times,
utterly incomprehensible.

He was distracted
by an incessant clamor...

...of speculations and associations
that ran through his head.

(MUMBLES)

One pleasant summer afternoon...

...with his students longing
for the end of the lecture...

...he was visited by a revelation
that was to alter radically...

...the future course
of astronomy and the world.

(TOP CLUNKS)

There were only six planets
known in his time:

Mercury, Venus, Earth, Mars,
Jupiter and Saturn.

For some time,
Kepler had been wondering:

Why only six planets?

Why not 20 planets, or 100?

And why this particular spacing
between their orbits?

No one had ever asked
such questions before.

In the course of
a lecture on astrology...

...Kepler inscribed within
the circle of the zodiac...

...a triangle with three equal sides.

He then noticed, quite by accident...

...that a smaller circle
inscribed within the triangle...

...bore the same relationship
to the outer circle...

...as did the orbit of Jupiter
to the orbit of Saturn.

Could a similar geometry relate
the orbits of the other planets?

Now Kepler remembered
the perfect solids of Pythagoras.

Of all the possible
three-dimensional shapes...

...there were only five
whose sides were regular polygons.

He believed that
the two numbers were connected...

...that the reason
there were only six planets...

...was that there were
only five regular solids.

In these perfect solids,
nested one within the other...

...he believed he had discovered
the invisible supports...

...for the spheres of the six planets.

This connection
between geometry and astronomy...

...could admit only one explanation:

The hand of God, mathematician.

"The intense pleasure I received
from this discovery...

...can never be told in words,"
he said.

"Now I no longer became weary at work.

Days and nights
I passed in mathematical labors...

...until I could see if my hypothesis
would agree with Copernicus'...

...or if my joy would vanish
into thin air."

But no matter how he hard tried, the
perfect solids and planetary orbits...

...did not agree
with each other very well.

Why didn't it work?

Because, unfortunately, it was wrong.

The true orbital sizes
of the planets we now know...

...have absolutely nothing to do
with the five perfect solids...

...as the later discovery
of Uranus, Neptune and Pluto shows.

But Kepler spent
the rest of his life...

...pursuing this
geometrical phantasm.

He couldn't abandon it,
and he couldn't make it work.

His frustration
must have been enormous.

Finally he decided that...

...the accepted planetary
observations were inaccurate...

...and not his model
of the nested solids.

Only one man had access
to more precise observations.

That man was Tycho Brahe...

...who, coincidentally, had recently
written Kepler to come and join him.

Kepler was reluctant at first,
but he had no choice.

In 1598, a wave of oppression
enveloped Graz.

It was spearheaded
by the local archduke...

...who vowed to restore Catholicism
to the province...

...and in his own words...

..."would rather make
a desert of the country...

...than rule over heretics."

Kepler's school was closed.

People were forbidden to worship
or to sing hymns...

...or to own books
of a heretical nature.

Those who refused Catholicism
were fined 10% of their assets...

...and exiled from the country
on pain of death.

Kepler chose exile.

"Hypocrisy, I have never learned.

I am in earnest about faith.
I do not play with it."

For Kepler, it was only the first
in a series of exiles...

...forced upon him
by religious fanatics.

Now he decided to accept
Tycho Brahe's open invitation.

Brahe, a wealthy Danish nobleman,
lived in great splendor...

...and had recently been appointed
Imperial Mathematician at Prague.

Kepler left Graz
with his wife and stepdaughter...

...and set out
on the difficult journey.

Kepler's wife was not a happy woman.

She was chronically ill and
had recently lost two young children.

The marriage was no comfort.

She had no understanding
of his work...

...and regarded his profession
with contempt.

Kepler was married to his work...

...and every tedious mile
was bringing him closer...

...to the great Tycho Brahe,
whose observations...

...he devoutly hoped,
would confirm his theory.

Kepler envisioned Tycho's domain as
a sanctuary from the evils of the time.

He aspired to be a worthy colleague
to the illustrious Tycho...

...who for 35 years
had been immersed...

...in exact measurements
of a clockwork universe...

...ordered and precise.

(PARTY CHATTER)

(MUSIC PLAYS)

(LAUGHING)

But Tycho's court was not at all
what Kepler had expected.

TYCHO:
Vinol

Tycho himself was
a flamboyant figure...

...adorned with a gold nose.

The original was lost
in a student duel...

...fought over who was
the superior mathematician.

And he maintained
a circus-like entourage...

...of assistants, distant relatives...

...and assorted hangers-on.

(SPEAKING IN FOREIGN LANGUAGE)

Kepler had no use
for the endless revelry.

He impatient to see Tycho's data.

But Tycho would give him
only a few scraps at a time.

"Tycho," he said, "gave me no
opportunity to share in his studies.

He would only,
in the course of a meal, mention...

...as if in passing...

...today, the figure
of the apogee of one planet.

Tomorrow, the nodes of another."

Kepler was ill-suited
for such games...

...and the general climate
of intrigue...

...offended his sense of propriety.

Their cruel mockery of
the pious and scholarly Kepler...

...depressed and saddened him.

"My opinion of Tycho is this:

He is superlatively rich...

...but knows not how
to make proper use of it."

Tycho possesses the best observations,
he also has collaborators.

He lacks only the architect...

...who would put all this to use."

(BAND PLAYS)

Tycho was unable
to turn his observations...

...into a coherent theory
of the solar system.

He knew he needed
the brilliant Kepler's help.

But simply to hand over
his life's work to a potential rival?

That was unthinkable.

(KEPLER SHOUTS)

Tycho was the greatest observational
genius of the age...

...and Kepler
the greatest theoretician.

Either man alone could not
achieve the synthesis...

...which both felt was now possible.

TYCHO:
Keplerel

The birth of modern science...

...which is the fusion
of observation and theory...

...teetered on the precipice
of their mutual distrust.

The two repeatedly quarreled...

...and were reconciled.

Until, a few months later...

...Tycho died of
his habitual overindulgence...

...in food and wine.

Kepler wrote to a friend:

"On the last night
of Tycho's gentle delirium...

...he repeated over
and over again these words...

...like someone composing a poem:

'Let me not seem
to have lived in vain.

Let me not seem
to have lived in vain.'

And he did not."

Eventually, after Tycho's death...

...Kepler contrived
to extract the observations...

...from Tycho's reluctant family.

Observations of the apparent motion...

...of Mars through
the constellations...

...obtained over
a period of many years.

The data, from the last few decades...

...before the invention
of the telescope...

...were by far the most precise
ever obtained up to that time.

Kepler worked with
a kind of passionate intensity...

...to understand Tycho's observations.

What real motions of the Earth...

...and Mars about the sun...

...could explain,
to the precision of measurement...

...the apparent motion, as seen
from the Earth, of Mars in the sky.

And why Mars?

Tycho had told Kepler that
the apparent motion of Mars...

...was the most difficult
to reconcile with a circular orbit.

After years of calculation,
he believed he'd found the values...

...for a Martian circular orbit
which matched...

...ten of Tycho Brahe's observations
within two minutes of arc.

There are sixty minutes of arc
in an angular degree...

...and of course,
90 degrees from horizon...

...to zenith.

So a few minutes of arc is
a small quantity to measure...

...especially without a telescope.

But Kepler's ecstasy of discovery...

...soon crumbled into gloom.

Two further observations by Tycho
were inconsistent with his orbit...

...by as much as eight minutes of arc.

Kepler wrote, "If I had believed we
could ignore these eight minutes...

...I would've patched up
my hypothesis accordingly.

Since it was not permissible
to ignore them...

...those eight minutes
pointed the road...

...to a complete reformation
of astronomy."

The difference between a circular orbit
and the true orbit of Mars...

...could be distinguished
only by precise measurement...

...and by a courageous
acceptance of the facts.

Kepler was profoundly annoyed
at having to abandon a circular orbit.

It shook his faith in God...

...as the Maker of
a perfect celestial geometry.

"Having cleaned the stable...

...of astronomy of circles
and spirals," he said...

...he was left...

...with "only a single
cartful of dung."

He tried various oval-like curves,
calculated away...

...made some arithmetical mistakes...

...which caused him
to reject the correct answer.

Months later, in some desperation...

...he tried the formula
for the first time for an ellipse.

The ellipse matched
the observations of Tycho beautifully.

In such an orbit,
the sun isn't at the center.

It is offset.
It's at one focus of the ellipse.

When a given planet is at the far
point in its orbit from the sun...

...it goes more slowly.

As it approaches the near point,
it speeds up.

Such motion is why
we describe the planets...

...as forever falling
towards the sun...

...but never reaching it.

Kepler's first law of
planetary motion is simply this:

A planet moves in an ellipse...

...with the sun at one focus.

As a planet moves along its orbit,
it sweeps out...

...in a given period of time,
an imaginary wedge-shaped area.

When the planet's far from the sun,
the area's long and thin.

When the planet is close to the sun,
the area is short and squat.

Though the shapes of
the wedges are different...

...Kepler found that
their areas are exactly the same.

This provided a precise description
of how a planet changes its speed...

...in relation to its distance
from the sun.

Now, for the first time...

...astronomers could predict
where a planet would be...

...in accordance with
a simple and invariable law.

Kepler's second law is this:

A planet sweeps out equal areas
in equal times.

Kepler's first two
laws of planetary motion...

...may seem a little
remote and abstract.

Planets move in ellipses and they
sweep out equal areas in equal times.

So what?

It's not as easy to grasp
as circular motion.

We might have a tendency
to dismiss it...

...to say it's a mere
mathematical tinkering...

...something removed
from everyday life.

But these are the laws
our planet itself obeys.

As we, glued by gravity
to the surface of the Earth...

...hurtle through space...

...we move in accord
with laws of nature...

...which Kepler first discovered.

When we send spacecraft
to the planets...

...when we observe double stars...

...when we examine the motion
of distant galaxies...

...we find that all over the universe,
Kepler's laws are obeyed.

Many years later...

...Kepler came upon his third
and last law of planetary motion.

A law which relates the motion of
the various planets to each other...

...which lays out correctly...

...the clockwork of the solar system.

He discovered
a mathematical relationship...

...between the size
of a planet's orbit...

...and the average speed at
which it travels around the sun.

This confirmed his long-held belief...

...that there must be a force in
the sun that drives the planets.

A force stronger for
the inner, fast-moving planets...

...and weaker for
the outer, slow-moving planets.

Isaac Newton later identified
that force as gravity.

Answering at last
the fundamental question:

What makes the planets go?

Kepler's third or Harmonic Law...

...states that the squares
of the periods of the planets...

...the time for them
to make one orbit...

...are proportional to the cubes,
the third power...

...of their average distances
from the sun.

So the further away a planet is
from the sun, the slower it moves...

...but according to
a precise mathematical law.

Kepler was the first person in
the history of the human species...

...to understand correctly
and quantitatively...

...how the planets move...

...how the solar system works.

The man who sought harmony
in the cosmos...

...was fated to live at a time
of exceptional discord on Earth.

Exactly eight days after
Kepler's discovery of his third law...

...there occurred in Prague
an incident...

...that unleashed
the devastating Thirty Years' War.

The war's convulsions shattered
the lives of millions of people.

Kepler lost his wife and young son
to an epidemic spread by the soldiery.

His royal patron was deposed...

...and he was excommunicated
from the Lutheran church...

...for his uncompromising independence
on questions of belief.

He was a refugee once again.

The conflict...

...portrayed on both sides
as a "holy war"...

...was more an exploitation
of religious bigotry...

...by those hungry for land and power.

This war introduced
organized pillage...

...to keep armies in the field.

The brutalized population of Europe
stood by helpless...

...as their plowshares
and pruning hooks...

...were literally beaten
into swords and spears.

Rumor and paranoia swept
through the countryside...

...enveloping especially
the powerless.

Among the many scapegoats chosen...

...were elderly women living alone,
who were charged with witchcraft.

(THUNDER)

(HORSE WHINNIES)

(WOMAN CRIES)

Kepler's mother was taken away
in the middle of the night...

...in a laundry chest.

It took Kepler six years
of unremitting effort...

...to save her life.

In Kepler's little hometown,
about three women were arrested...

...tortured and killed
as witches every year...

...between 1615 and 1629.

And Katarina Kepler was
a cantankerous old woman.

She engaged in disputes
which annoyed the local nobility...

...and she sold drugs.

Poor Kepler thought that
he himself had contributed...

...inadvertently,
to his mother's arrest.

It came about
because he had written...

...one of the first works
of science fiction.

It was intended to explain
and popularize science...

...and was called The Somnium.

"The Dream."

He imagined a journey to the moon...

...with the space travelers
standing on the lunar surface...

...looking up to see,
rotating slowly above them...

...the lovely planet Earth.

Part of the basis for the charge
of witchcraft was that...

...in his dream, Kepler used his
mother's spells to leave the Earth.

But he really believed that one day...

...human beings would launch
celestial ships...

...with sails adapted
to the breezes of heaven...

...filled with explorers who,
he said...

..."would not fear
the vastness of space."

He speculated on the mountains,
valleys, craters...

...climate and possible
inhabitants of the moon.

Before Kepler...

...astronomy had little connection
with physical reality.

But with Kepler came the idea that...

...a physical force moves
the planets in their orbits.

He was the first
to combine a bold imagination...

...with precise measurements...

...to step out into the cosmos.

It changed everything.

This fusion of facts with dreams...

...opened the way to the stars.

As a boy...

...Kepler had been captured
by a vision of cosmic splendor...

...a harmony of the worlds...

...which he sought so tirelessly
all his life.

Harmony in this world eluded him.

His three laws of
planetary motion represent...

...we now know...

...a real harmony of the worlds.

But to Kepler, they were
only incidental to his quest...

...for a cosmic system
based on the perfect solids.

A system which, it turns out,
existed only in his mind.

Yet, from his work...

...we have found that scientific laws
pervade all of nature...

...that the same rules apply
on Earth as in the skies...

...that we can find
a resonance, a harmony...

...between the way we think
and the way the world works.

When he found that his long-cherished
beliefs did not agree...

...with the most
precise observations...

...he accepted
the uncomfortable facts.

He preferred the hard truth...

...to his dearest illusions.

That is the heart of science.