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¶ ¶
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¶ ¶
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¶ ¶
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NEIL DEGRASSE TYSON:
The age and size of the cosmos
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are written in light.
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The nature of beauty and
the substance of the stars,
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the laws of space and time...
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they were there all along,
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but we never saw them...
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until we devised
a more powerful way of seeing.
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The story of this awakening
has many beginnings
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and no ending.
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Its heroes come from many times
and places--
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an ancient Chinese philosopher,
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a wizard who amazed the caliphs
of 11th-century Iraq,
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a poor German orphan enslaved
to a harsh master.
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Each one brought us
a little closer
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to unlocking the secrets
hidden in light.
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Most of their names
are forever lost to us,
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but somewhere, long ago,
someone glanced up
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to see light perform
one of its magic tricks.
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Who knows?
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Maybe that quirk of light
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inspired the very first artist.
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(horse neighs)
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Where did all this come from?
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How did we evolve
from small wandering bands
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of hunters and gatherers living
beneath the stars
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to become the builders
of a global civilization?
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How did we get from there
to here?
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There's no one answer.
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Climate change,
the domestication of fire,
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the invention of tools,
language, agriculture
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all played a role.
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Maybe there was
something else, too.
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In China,
more than 2,000 years ago,
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a philosopher named Mo Tze
is said to have observed
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that light could be made
to paint a picture
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inside a locked treasure room.
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This was the description
of the first camera...
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the camera obscura,
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the prototype of all
image-forming cameras,
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including the one that's
bringing you this picture.
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Taking advantage of this funny
thing that light does
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resulted in what could be
called the first movie.
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Mo Tze, master of light, worked
against all forms of darkness.
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A military genius
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who only used his talents
to prevent violence,
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he was legendary for traveling
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among the kingdoms
of the warring states,
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employing ingenious strategies
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to talk kings out
of going to war.
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He was one of the first
to dream of universal love
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and an end to poverty
and other forms of inequality;
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of government for the people...
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and to argue against
blind obedience
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to ritual and authority.
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In his writings, you can find
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early stirrings
of the scientific approach.
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By Mo Tze's time, the Chinese
had already been recording
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their thoughts in books
for at least a thousand years.
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Still, our knowledge of him
is only fragmentary.
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It consists largely
of the collection of essays
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attributed to him
and his disciples.
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In one of them,
entitled "Against Fate,"
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a three-pronged test
for every doctrine is proposed:
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Question its basis--
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ask if it can be verified
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by the sights and senses
of common people--
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ask how it is to be applied
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and if it will benefit
the greatest number.
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(door opens, people shouting)
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Mo Tze was extremely popular,
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but a few hundred years
after his death,
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Qin Shi Huang,
the first emperor,
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and unifier of China,
took power.
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He took a continent
and turned it into a nation
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that now bears his name: China.
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(blow strikes, man grunts)
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Most of us know Emperor Qin
for the army of 7,000
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terra cotta warriors
that guard his tomb.
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In Emperor Qin's drive
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to consolidate
his far-flung empire,
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he took drastic measures
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to standardize everything
within it.
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This included mandating
a single coinage,
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making uniform all weights
and measures,
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the widths of carts and roads,
as well as the precise way
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the Chinese language was
to be written,
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including what you were
allowed to write and think.
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Emperor Qin's philosophy--
the only one permitted--
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was called "legalism,"
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which is just what
it sounded like:
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do as the law says... or else.
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It's a philosophy that's
not highly conducive
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to questioning authority.
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(man speaking Chinese)
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MAN: ...that all the books of
the hundred schools of thought
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shall be be burned,
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that anyone who uses history
to criticize the present
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shall have his family executed.
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(people gasping)
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DEGRASSE TYSON: The works of
MoTze and Confucius
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and other philosophers
were destroyed
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in the world's first
book burning.
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Hundreds of scholars
bravely resisted
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by trying to preserve
the forbidden books.
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They were buried alive
in the capitol.
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Science needs the light
of free expression to flourish.
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It depends on the fearless
questioning of authority,
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the open exchange of ideas.
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Sparks of curiosity
in the writings of Mo Tze
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and his disciples were
effectively stomped out.
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It would be another thousand
years before the next movie.
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Luckily, our Ship
of the Imagination
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can take us anywhere
in space... and time.
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The ancient Chinese
and Greeks observed
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that light could be made
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to do wonderful things--
but no one asked that question
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favored by small children
and geniuses alike: Why?
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Until a thousand years ago...
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In the city of Basra, Iraq,
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there lived
another master of light.
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Ibn al-Hazen had a passionate
desire to understand nature.
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He questioned everything,
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especially those things that
everyone else took for granted.
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"How do we see?" he asked.
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Some of the great authorities
who came before him
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had taught that rays come out
of our eyes and travel
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to the objects we see
before returning to our eyes.
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But al-Hazen reasoned that
the stars were too far distant
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for something in our eyes
to travel all the way to them
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and back in the blink
of an eye.
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Excellent reasoning,
but al-Hazen didn't stop there.
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He searched for ways to compel
nature to divulge her secrets.
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His culture was open
to new ideas and questioning.
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It was the golden age
of science
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in the Islamic world.
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One that stretched from Cordoba
in Spain
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all the way to Samarkand
in Central Asia.
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Christian and Jewish scholars
were honored guests
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at the research institutes
of Baghdad, Cairo,
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and other Islamic capitols.
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Instead of burning books,
the caliphs sent emissaries
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around the world
in search of books.
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The caliphs lavishly funded
projects to translate, study,
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and preserve them
for future generations.
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Much of the light of ancient
Greek science would have been
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permanently extinguished
without their efforts.
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The reawakening to science
that took place in Europe,
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hundreds of years later,
was kindled by a flame
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that had been long tended
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by Islamic scholars
and scientists.
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The Arabs also imported ideas
from India to the West,
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including the so-called
Arabic numerals
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that we all use today,
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and the concept of zero...
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...which comes in handy
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when you want to write
"billions and billions."
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Arabic astronomy was
so influential,
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that we still call most
of the bright stars
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by their Arabic names.
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And the "al's" in algebra,
algorithm, alchemy, and alcohol
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are just some
of the traces left
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from the time when Arabic
was the language of science.
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In the 11th century,
Ibn al-Hazen set about trying
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to test his ideas about light
and how we see.
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So we devised an experiment
to determine how light moves.
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We erected a tent
in full daylight
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and sealed it tightly so that
only a single ray of light
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could pierce its inner darkness.
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With little more than his brains
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and a straight
piece of wood-- a ruler--
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al-Hazen had accomplished
a great leap forward
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in the history of science.
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He discovered that
light moves in straight lines.
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But he was just getting started.
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Al-Hazen figured out that
the key to forming any image--
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whether you're talking about
an eye or camera obscura--
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is a small opening to restrict
the light that can enter
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an otherwise darkened chamber.
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That aperture
excludes the chaos
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of extraneous light rays
that surround us.
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The smaller the aperture,
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the fewer directions
that light can come from.
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And that makes
the image sharper.
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So instead of being blinded
by the light,
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we can see everything
it has to show us.
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Al-Hazen made his own
camera obscura
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and dazzled the caliphs.
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A camera obscura works best
in bright light.
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The stars of the night sky
are way too dim for this.
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We somehow need a bigger
opening to collect light,
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but we also need
to maintain focus.
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A telescope collects light
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from any spot
in its field of view
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across the entire lens
or mirror,
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an opening much larger
than the camera obscura hole.
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This is one
of the first telescopes...
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the one that Galileo looked
through in 1609.
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With it, he pulled aside
the heavy curtain of night
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and began to discover
the cosmos.
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The lens made it possible
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for a telescope to have a much
larger light-collecting area
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than our eyes have.
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Big buckets catch more rain
than small ones.
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Modern telescopes have larger
collecting areas,
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highly sensitive detectors,
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and they track the same object
for hours at a time
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to accumulate as much
of its light as possible.
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Space-based telescopes
such as the Hubble,
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have captured light
from the most distant
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and ancient galaxies,
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giving us vastly clearer
pictures of the cosmos.
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Al-Hazen discovered how images
are formed by light,
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but that was far
from his greatest achievement.
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Ibn al-Hazen was the first
person ever
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to set down
the rules of science.
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He created
an error-correcting mechanism,
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a systematic and relentless way
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to sift out misconceptions
in our thinking.
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Finding truth is difficult...
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and the road to it is rough.
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As seekers after truth,
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you will be wise to withhold
judgment and not simply put
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your trust in the writings
of the ancients.
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You must question and critically
examine those writings
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from every side.
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You must submit only
to argument and experiment
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and not to the sayings
of any person.
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For every human being
is vulnerable
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to all kinds of imperfection.
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As seekers after truth,
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we must also suspect
and question
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our own ideas as we perform
our investigations,
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to avoid falling into prejudice
or careless thinking.
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Take this course, and truth
will be revealed to you.
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DEGRASSE TYSON:
This is the method of science.
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So powerful that it's carried
our robotic emissaries
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to the edge of
the solar system and beyond.
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It has doubled our lifespan,
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made the lost worlds
of the past
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come alive.
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Science has enabled us
to predict events
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in the distant future...
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and to communicate with each
other at the speed of light,
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as I am with you,
right at this moment.
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This way of thinking
has given us powers
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that al-Hazen himself
would have regarded as wizardry.
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But it was he who put us
on this rough, endless road.
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And now it has taken us
to a place
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where even light itself
is enshrouded in darkness.
253
00:15:50,432 --> 00:15:52,567
Light has properties unlike
anything else
254
00:15:52,601 --> 00:15:54,469
in the realm
of human existence.
255
00:15:54,503 --> 00:15:56,638
Take the speed of light.
256
00:15:56,672 --> 00:15:58,773
The basic particle of light,
the photon,
257
00:15:58,807 --> 00:16:01,476
is born traveling
at the speed of light
258
00:16:01,510 --> 00:16:04,278
as it emerges from
an atom or a molecule.
259
00:16:04,313 --> 00:16:06,447
A photon never knows
any other speed,
260
00:16:06,482 --> 00:16:09,283
and we've not found another
phenomenon that accelerates
261
00:16:09,318 --> 00:16:12,253
from zero to top speed
instantaneously.
262
00:16:12,287 --> 00:16:14,489
Nothing else
could move as fast.
263
00:16:14,523 --> 00:16:17,158
When we try to accelerate other
particles closer and closer
264
00:16:17,192 --> 00:16:19,894
to the speed of light,
they resist more and more,
265
00:16:19,928 --> 00:16:21,663
as though they're getting
heavier and heavier.
266
00:16:21,697 --> 00:16:23,131
No experiment yet devised
267
00:16:23,165 --> 00:16:27,168
has ever made a particle
move as fast as light.
268
00:16:27,202 --> 00:16:30,204
(musical notes play,
confined to a single octave)
269
00:16:33,842 --> 00:16:36,477
What was that?
270
00:16:36,512 --> 00:16:38,680
You hear something?
271
00:16:38,714 --> 00:16:40,848
Where was I? Oh, yeah.
272
00:16:40,883 --> 00:16:44,952
I don't know anything else
in life that behaves like light.
273
00:16:44,987 --> 00:16:48,423
I cannot reconcile
its strange properties
274
00:16:48,457 --> 00:16:51,092
with everything else
my senses tell me.
275
00:16:51,126 --> 00:16:54,095
Our urge to trust
our senses overpowers
276
00:16:54,129 --> 00:16:56,197
what our measuring devices
tell us about
277
00:16:56,231 --> 00:16:58,132
the actual nature of reality.
278
00:16:58,167 --> 00:17:00,334
Our senses work fine
for life-size objects
279
00:17:00,369 --> 00:17:02,170
moving at mammal speeds,
280
00:17:02,204 --> 00:17:06,808
but are ill-adapted for the
wonderland laws of lightspeed.
281
00:17:10,979 --> 00:17:14,348
We don't even know why
there's a cosmic speed limit.
282
00:17:14,383 --> 00:17:17,819
Time stands still when you're
traveling at the speed of light.
283
00:17:17,853 --> 00:17:20,321
What is light, anyway?
284
00:17:23,859 --> 00:17:27,361
Isaac Newton's enduring
fascination with light
285
00:17:27,396 --> 00:17:29,564
began when he was a child....
286
00:17:32,000 --> 00:17:34,435
...in this very house.
287
00:17:39,508 --> 00:17:43,678
By the time he was in his 20s,
Newton became the first person
288
00:17:43,712 --> 00:17:46,881
to decipher the mystery
of the rainbow.
289
00:17:50,586 --> 00:17:53,888
Newton discovered that some
light, or white light,
290
00:17:53,890 --> 00:17:56,891
is a mixture of all the colors
of the rainbow.
291
00:17:59,428 --> 00:18:01,496
Major discovery.
292
00:18:01,530 --> 00:18:04,065
He named the displays of colors
a "spectrum"
293
00:18:04,099 --> 00:18:08,352
from the Latin for "phantom"
or "apparition."
294
00:18:18,480 --> 00:18:20,581
(knocking on door,
door opens)
295
00:18:20,616 --> 00:18:22,583
Begging your pardon,
Master Newton,
296
00:18:22,618 --> 00:18:25,319
the cook frets that your dinner
will spoil, sir.
297
00:18:28,223 --> 00:18:30,391
DEGRASSE TYSON: No, Isaac, don't
put the magnifying glass down!
298
00:18:30,425 --> 00:18:34,195
Something even more amazing
is hidden in the light--
299
00:18:34,229 --> 00:18:36,731
a code, a key to the cosmos.
300
00:18:43,505 --> 00:18:47,408
Isaac Newton didn't miss much,
but that one was a beaut.
301
00:18:47,442 --> 00:18:50,545
He just walked right past
the door to a hidden universe;
302
00:18:50,579 --> 00:18:54,615
a door that would not swing open
again for another 150 years.
303
00:18:54,650 --> 00:18:56,951
It would fall
on another scientist,
304
00:18:56,985 --> 00:18:58,653
working in the year 1800,
305
00:18:58,720 --> 00:19:00,655
to stumble
on a piece of evidence
306
00:19:00,689 --> 00:19:03,691
for the unseen worlds
that surround us.
307
00:19:07,262 --> 00:19:09,964
By night, William Herschel
scanned the heavens
308
00:19:09,998 --> 00:19:12,466
with the largest telescope
of his time.
309
00:19:12,501 --> 00:19:15,436
By day, Herschel performed
experiments.
310
00:19:15,470 --> 00:19:18,105
From Newton's earlier work,
it was known that sunlight
311
00:19:18,140 --> 00:19:20,508
is a blend of different colors.
312
00:19:20,542 --> 00:19:22,910
And everyone knew,
just from being outside,
313
00:19:22,945 --> 00:19:25,146
that sunlight carries heat.
314
00:19:26,682 --> 00:19:28,683
William Herschel asked
315
00:19:28,685 --> 00:19:31,285
whether some colors of light
carry more heat than others.
316
00:19:31,320 --> 00:19:35,423
The nature of scientific genius
is to question
317
00:19:35,457 --> 00:19:38,259
what the rest of us
take for granted...
318
00:19:38,293 --> 00:19:40,862
and then do the experiment.
319
00:19:42,898 --> 00:19:46,367
The thermometer that Herschel
placed outside the spectrum
320
00:19:46,369 --> 00:19:48,369
was his control.
321
00:19:50,072 --> 00:19:51,973
The control
in any experiment
322
00:19:52,007 --> 00:19:54,642
always lacks
the factor being tested.
323
00:19:54,676 --> 00:19:56,777
That way, you know
if what you're testing is
324
00:19:56,812 --> 00:19:58,913
really the thing responsible
for the observation.
325
00:20:00,048 --> 00:20:01,349
In Herschel's experiment,
326
00:20:01,383 --> 00:20:02,984
the relationship between
327
00:20:03,018 --> 00:20:04,385
color and temperature
was being tested,
328
00:20:04,419 --> 00:20:07,488
and so his control was
a thermometer
329
00:20:07,522 --> 00:20:09,190
over the part
of the white sheet
330
00:20:09,224 --> 00:20:12,526
that was not illuminated
by sunlight at all.
331
00:20:12,561 --> 00:20:14,829
(musical notes play,
confined to a single octave)
332
00:20:14,863 --> 00:20:16,397
There's that sound again.
333
00:20:16,431 --> 00:20:19,166
What is that?
334
00:20:24,907 --> 00:20:27,408
Okay, red light is warmer
than blue light.
335
00:20:27,442 --> 00:20:32,513
Interesting discovery,
but not exactly revolutionary.
336
00:20:54,036 --> 00:20:57,738
No, there's nothing wrong
with your thermometer.
337
00:20:57,773 --> 00:21:01,125
You've just discovered
a new kind of light.
338
00:21:09,985 --> 00:21:13,054
Herschel was the first
to detect this unseen presence
339
00:21:13,088 --> 00:21:16,257
lurking just below
the red end of the spectrum.
340
00:21:16,291 --> 00:21:19,193
That's why it came
to be called "infrared."
341
00:21:19,227 --> 00:21:21,395
"Infra" is Latin
for the word "below."
342
00:21:21,430 --> 00:21:22,997
It's invisible.
343
00:21:23,031 --> 00:21:25,399
Our eyes are not sensitive
to this kind of light,
344
00:21:25,434 --> 00:21:28,302
but our skin is--
we feel it as heat.
345
00:21:28,337 --> 00:21:30,137
Now, that's
a really big discovery.
346
00:21:30,172 --> 00:21:32,573
But far greater secrets
were still hiding
347
00:21:32,607 --> 00:21:35,076
deep inside the light.
348
00:21:40,766 --> 00:21:42,800
DEGRASSE TYSON:
At about the same time
that William Herschel
349
00:21:42,834 --> 00:21:45,736
was discovering infrared light
in his parlor in England,
350
00:21:45,771 --> 00:21:48,239
a young boy named
Joseph Fraunhofer
351
00:21:48,273 --> 00:21:50,741
was trapped
in hopeless drudgery.
352
00:21:50,776 --> 00:21:53,711
He stood over a cauldron
of toxic chemicals
353
00:21:53,745 --> 00:21:56,113
and endlessly stirred.
354
00:21:58,016 --> 00:22:00,818
Joseph had been orphaned
at the age of 11
355
00:22:00,885 --> 00:22:04,655
and given to a harsh master
named Weichselberger,
356
00:22:04,690 --> 00:22:07,625
the royal mirror-maker.
357
00:22:07,627 --> 00:22:09,927
He prevented Joseph
from going to school.
358
00:22:09,961 --> 00:22:13,164
Instead, Joseph labored in
359
00:22:13,198 --> 00:22:15,132
the glass-making
workshop by day,
360
00:22:15,167 --> 00:22:17,635
and tended to the master's
household chores by night.
361
00:22:17,669 --> 00:22:19,103
(thunder crashes)
362
00:22:23,141 --> 00:22:24,642
WEICHSELBERGER:
Hurry up, stupid!
363
00:22:24,676 --> 00:22:27,595
And remember,
no reading.
364
00:22:27,646 --> 00:22:28,913
(door thuds shut)
365
00:22:31,983 --> 00:22:34,819
DEGRASSE TYSON:
Until Joseph got his big break.
366
00:22:34,853 --> 00:22:37,321
Weichselberger's
house collapsed.
367
00:22:37,356 --> 00:22:39,857
(rumbling)
368
00:22:45,664 --> 00:22:47,665
(men murmuring)
369
00:22:51,970 --> 00:22:54,071
(Weichselberger groaning weakly)
370
00:22:56,675 --> 00:22:58,542
Maximilian, the future
king of Bavaria,
371
00:22:58,577 --> 00:23:00,478
hurried to the scene
of the calamity
372
00:23:00,512 --> 00:23:02,046
to see if he could help.
373
00:23:02,080 --> 00:23:04,515
Maximilian was known for
374
00:23:04,549 --> 00:23:06,150
taking an interest
in his subjects,
375
00:23:06,184 --> 00:23:08,386
which was highly unusual
for its time.
376
00:23:16,595 --> 00:23:18,596
(townsfolk murmuring)
377
00:23:22,267 --> 00:23:25,403
In attracting the concern
of the future king of Bavaria,
378
00:23:25,437 --> 00:23:27,037
young Joseph Fraunhofer
379
00:23:27,072 --> 00:23:29,874
found an aperture into
a different universe.
380
00:23:29,908 --> 00:23:32,343
And not just for himself.
381
00:23:35,480 --> 00:23:37,214
Prince Maximilian
gave Joseph money
382
00:23:37,249 --> 00:23:39,049
and asked his privy councilor
383
00:23:39,084 --> 00:23:40,518
to provide further
help to the boy,
384
00:23:40,552 --> 00:23:42,920
should it be needed.
385
00:23:47,793 --> 00:23:50,494
Weichselberger continued
to exploit him
386
00:23:50,529 --> 00:23:52,830
and prevent him
from attending school.
387
00:23:52,864 --> 00:23:54,899
But the prince's councilor
intervened,
388
00:23:54,933 --> 00:23:58,436
offering Joseph a position
at the Optical Institute.
389
00:23:58,470 --> 00:24:03,607
This small gesture of kindness
really paid off.
390
00:24:15,954 --> 00:24:18,789
By the time he was 27,
391
00:24:18,824 --> 00:24:21,058
Joseph Fraunhofer was
the world's leading designer
392
00:24:21,092 --> 00:24:23,093
of high-quality lenses,
393
00:24:23,128 --> 00:24:25,796
telescopes and other
optical instruments.
394
00:24:25,831 --> 00:24:29,700
His firm was housed here,
in the old Benediktbeuren Abbey.
395
00:24:29,734 --> 00:24:31,902
In the early 19th century,
396
00:24:31,937 --> 00:24:35,239
this was top-secret,
ultra-high technology.
397
00:24:38,276 --> 00:24:40,478
The Benedictine monks
of earlier times
398
00:24:40,512 --> 00:24:42,480
had taken a vow of secrecy.
399
00:24:42,514 --> 00:24:44,482
This local tradition,
400
00:24:44,516 --> 00:24:45,983
and the ability
to restrict access
401
00:24:46,017 --> 00:24:47,551
to Fraunhofer's laboratory,
402
00:24:47,586 --> 00:24:49,553
allowed him to maintain control
403
00:24:49,588 --> 00:24:52,656
of trade and state secrets.
404
00:24:57,762 --> 00:25:00,064
Fraunhofer was experimenting
with prisms
405
00:25:00,098 --> 00:25:03,501
to find the best types of glass
for precision lenses.
406
00:25:03,535 --> 00:25:06,237
How, he wondered,
could he get a better look
407
00:25:06,271 --> 00:25:08,272
at the spectrum that
a prism produced?
408
00:25:11,443 --> 00:25:15,246
Friedrich, bring me
the theodolite, please.
409
00:25:15,280 --> 00:25:18,182
Okay, while Fraunhofer
sets up his theodolite--
410
00:25:18,216 --> 00:25:20,017
it's a kind of telescope--
411
00:25:20,051 --> 00:25:23,354
I want to show you something
in another part of the abbey.
412
00:25:27,993 --> 00:25:31,729
Sound waves are
so beautiful to hear.
413
00:25:33,565 --> 00:25:38,269
Imagine how beautiful
they'd be to see.
414
00:25:38,303 --> 00:25:41,505
You ever wondered why organ
pipes have different lengths?
415
00:25:43,742 --> 00:25:44,975
I press a key...
416
00:25:45,010 --> 00:25:47,444
(high note plays)
417
00:25:47,479 --> 00:25:48,879
...it sends compressed air
418
00:25:48,914 --> 00:25:50,147
into a particular pipe,
419
00:25:50,181 --> 00:25:51,982
producing sound waves.
420
00:25:52,017 --> 00:25:54,718
If we could slow the sound waves
down a few hundred times,
421
00:25:54,753 --> 00:25:56,887
they would look like this.
422
00:25:56,922 --> 00:25:59,323
(notes playing)
423
00:26:00,592 --> 00:26:02,226
The length of the pipe
424
00:26:02,260 --> 00:26:03,694
determines the length
of the sound wave
425
00:26:03,728 --> 00:26:05,195
that can fit inside it.
426
00:26:05,230 --> 00:26:07,298
A short pipe gives you
a short sound wave.
427
00:26:07,332 --> 00:26:09,300
(high note plays)
428
00:26:09,334 --> 00:26:12,069
Short sounds waves have
high pitch, or frequency.
429
00:26:17,576 --> 00:26:20,244
Let's stop the waves
for a better look.
430
00:26:22,213 --> 00:26:24,582
(low note plays)
431
00:26:24,616 --> 00:26:26,550
The distance between
adjacent waves
432
00:26:26,585 --> 00:26:28,352
is called the wavelength.
433
00:26:28,386 --> 00:26:30,888
A long pipe gives you
a long sound wave
434
00:26:30,922 --> 00:26:33,290
with a low pitch,
or low frequency.
435
00:26:35,026 --> 00:26:38,028
(playing classical melody)
436
00:26:38,046 --> 00:26:39,430
(clears throat)
437
00:26:39,464 --> 00:26:41,899
(stops playing)
438
00:26:47,906 --> 00:26:50,240
(playing "Fortuna"
from "Carmina Burana")
439
00:27:10,295 --> 00:27:12,630
¶ ¶
440
00:27:17,335 --> 00:27:18,902
(stops playing)
441
00:27:24,843 --> 00:27:27,745
The medieval manuscript of
this music, "Carmina Burana,"
442
00:27:27,779 --> 00:27:30,948
was discovered
in this very abbey.
443
00:27:34,152 --> 00:27:36,587
Sound waves can't travel
through a vacuum.
444
00:27:36,621 --> 00:27:38,489
They need matter to ride on,
445
00:27:38,523 --> 00:27:41,992
like molecules of air,
or water, or rock.
446
00:27:42,027 --> 00:27:44,128
But light waves fly solo.
447
00:27:44,162 --> 00:27:46,330
They can move
through empty space.
448
00:27:46,364 --> 00:27:47,965
And fast--
449
00:27:47,999 --> 00:27:51,101
a million times faster
than sound waves in air.
450
00:27:51,136 --> 00:27:53,103
And the wavelengths
of the light we see
451
00:27:53,138 --> 00:27:55,639
are so much shorter
than sound waves.
452
00:27:55,674 --> 00:27:58,509
About 50,000 light waves
453
00:27:58,543 --> 00:28:00,978
would fit right in here.
454
00:28:02,147 --> 00:28:03,681
Oh, yeah.
455
00:28:03,715 --> 00:28:05,149
Fraunhofer.
456
00:28:11,790 --> 00:28:13,123
Just in time.
457
00:28:13,158 --> 00:28:14,792
We didn't miss it.
458
00:28:14,826 --> 00:28:16,994
Just as the wavelength of sound
459
00:28:17,028 --> 00:28:18,996
determines the pitch
that we hear,
460
00:28:19,030 --> 00:28:20,497
the wavelength of light
461
00:28:20,565 --> 00:28:22,966
determines the color
that we see.
462
00:28:23,001 --> 00:28:25,436
But how does a prism
spread out the colors
463
00:28:25,470 --> 00:28:27,971
concealed in
a beam of sunlight?
464
00:28:28,006 --> 00:28:31,942
When light travels
through air or space,
465
00:28:31,976 --> 00:28:34,344
all its colors move
at the same speed.
466
00:28:36,381 --> 00:28:39,149
But when it hits glass
at an angle,
467
00:28:39,184 --> 00:28:41,585
the light slows down
and changes direction.
468
00:28:43,154 --> 00:28:45,122
Inside the prism,
469
00:28:45,156 --> 00:28:47,157
each color moves
at a different speed.
470
00:28:51,496 --> 00:28:53,297
In glass, violet light,
471
00:28:53,331 --> 00:28:55,499
which is carried by
the shortest waves we see,
472
00:28:55,533 --> 00:28:57,534
slows down more than red light,
473
00:28:57,569 --> 00:29:00,003
which has the longest waves.
474
00:29:01,840 --> 00:29:04,241
These changes in speed
475
00:29:04,275 --> 00:29:06,810
pry the colors apart,
476
00:29:06,845 --> 00:29:08,645
sending their waves off
477
00:29:08,680 --> 00:29:11,081
in slightly different
directions.
478
00:29:12,283 --> 00:29:14,284
That's how a prism works.
479
00:29:16,421 --> 00:29:18,689
If I seem unduly
emotional about this,
480
00:29:18,723 --> 00:29:21,508
it's because Joseph Fraunhofer
is about to do
481
00:29:21,559 --> 00:29:25,062
what Isaac Newton
could've done, but didn't.
482
00:29:25,064 --> 00:29:27,164
And it'll have a powerful effect
483
00:29:27,198 --> 00:29:29,032
on the course of my own life.
484
00:29:52,056 --> 00:29:54,091
You are witnessing the marriage
485
00:29:54,093 --> 00:29:55,726
of physics and astronomy,
486
00:29:55,760 --> 00:29:59,563
the birth of my own
field of science:
487
00:29:59,664 --> 00:30:02,099
astrophysics.
488
00:30:04,102 --> 00:30:05,869
Written in the light,
489
00:30:05,904 --> 00:30:09,306
in those vertical black lines...
490
00:30:10,742 --> 00:30:13,710
...is secret code.
491
00:30:13,745 --> 00:30:16,547
Fraunhofer looked at them,
and wondered...
492
00:30:16,581 --> 00:30:18,582
Why?
493
00:30:20,485 --> 00:30:23,821
DEGRASSE TYSON:
A code that comes to us
494
00:30:23,855 --> 00:30:26,290
from an alien universe.
495
00:30:29,878 --> 00:30:31,879
¶ ¶
496
00:30:35,483 --> 00:30:37,885
DEGRASSE TYSON:
What is the message
497
00:30:37,919 --> 00:30:40,420
written in these dark,
vertical lines?
498
00:30:45,493 --> 00:30:47,561
It took a hundred years
of thinking,
499
00:30:47,595 --> 00:30:50,898
questioning, searching
to decipher it.
500
00:31:10,451 --> 00:31:12,586
Lovely, isn't it?
501
00:31:12,620 --> 00:31:14,154
Why?
502
00:31:14,188 --> 00:31:17,658
There are many layers to
the fine structure of beauty...
503
00:31:17,692 --> 00:31:20,827
the chemistry of the Earth
and its atmosphere...
504
00:31:20,862 --> 00:31:23,797
the evolution of life...
505
00:31:23,831 --> 00:31:27,401
Many distinct threads.
506
00:31:27,435 --> 00:31:30,504
Let's just examine one,
at the surface:
507
00:31:30,538 --> 00:31:32,940
the colors of nature
that dazzle us.
508
00:31:32,974 --> 00:31:36,076
What's really happening?
509
00:31:36,110 --> 00:31:37,978
How does the red,
the blue...
510
00:31:38,012 --> 00:31:40,981
the astonishing palette
of nature's colors...
511
00:31:44,986 --> 00:31:47,621
...how do they happen?
512
00:31:50,291 --> 00:31:52,459
Light waves of different lengths
from the Sun
513
00:31:52,493 --> 00:31:53,894
strike the Earth.
514
00:31:55,296 --> 00:31:57,331
The petals of these
particular flowers
515
00:31:57,365 --> 00:31:58,965
absorb all the low-energy,
516
00:31:58,967 --> 00:32:01,201
long red wavelengths of light.
517
00:32:01,235 --> 00:32:02,936
But the petals reflect
518
00:32:02,971 --> 00:32:06,273
the shorter, high-energy
blue wavelengths.
519
00:32:06,307 --> 00:32:09,042
That interaction
between starlight and petal--
520
00:32:09,077 --> 00:32:11,044
or water, or Van Gogh--
521
00:32:11,079 --> 00:32:12,646
is what makes blue.
522
00:32:12,680 --> 00:32:14,815
The longest waves,
523
00:32:14,849 --> 00:32:16,650
the ones we see as red,
524
00:32:16,684 --> 00:32:19,252
have the lowest energy.
525
00:32:22,190 --> 00:32:24,524
Color is the way
our eyes perceive
526
00:32:24,559 --> 00:32:26,426
how energetic light waves are.
527
00:32:28,262 --> 00:32:29,963
A sunset...
528
00:32:29,981 --> 00:32:32,132
a flag...
529
00:32:32,166 --> 00:32:34,568
the eyes of your beloved...
530
00:32:34,602 --> 00:32:36,336
that shiny new car.
531
00:32:36,371 --> 00:32:38,338
The feelings they inspire
532
00:32:38,373 --> 00:32:40,173
happen when something inside you
533
00:32:40,208 --> 00:32:42,676
is triggered by
a particular variation
534
00:32:42,710 --> 00:32:46,179
in the frequency and
energy of light waves.
535
00:32:47,949 --> 00:32:49,082
And the secret message?
536
00:32:49,117 --> 00:32:50,817
Those black vertical lines
537
00:32:50,852 --> 00:32:52,853
in Fraunhofer's spectrum?
538
00:32:52,887 --> 00:32:55,021
What makes them?
539
00:32:55,023 --> 00:32:57,190
They occur when the light waves
540
00:32:57,225 --> 00:32:59,993
of those particular colors
are being absorbed.
541
00:33:00,028 --> 00:33:02,562
It happens on another level
of reality,
542
00:33:02,630 --> 00:33:05,599
far smaller than the world
we're used to operating in.
543
00:33:05,633 --> 00:33:08,201
To get there,
we'll need to become
544
00:33:08,236 --> 00:33:10,971
ten billion times smaller
than we are.
545
00:33:13,741 --> 00:33:16,109
We could pick
any one of these atoms.
546
00:33:16,144 --> 00:33:19,212
But let's go
for the hydrogen atom.
547
00:33:19,247 --> 00:33:21,715
The hydrogen atom is
the most plentiful kind
548
00:33:21,749 --> 00:33:24,117
of atom in the cosmos.
549
00:33:24,152 --> 00:33:26,553
And the simplest.
550
00:33:34,062 --> 00:33:37,230
It has only one electron.
551
00:33:37,265 --> 00:33:39,766
And only one proton.
552
00:33:39,801 --> 00:33:41,868
We've entered
the quantum realm.
553
00:33:41,903 --> 00:33:43,704
It doesn't correspond
554
00:33:43,738 --> 00:33:46,473
to ordinary human experience.
555
00:33:46,507 --> 00:33:49,710
Common sense is
no help here at all.
556
00:33:49,744 --> 00:33:52,746
Take the hydrogen atom's
electron, for example.
557
00:33:54,682 --> 00:33:56,917
In an atom, an electron
558
00:33:56,951 --> 00:33:58,652
doesn't exist between orbitals.
559
00:33:58,686 --> 00:34:00,454
It disappears from one orbital
560
00:34:00,488 --> 00:34:03,123
and reappears in another.
561
00:34:03,157 --> 00:34:04,958
It's as if you took an elevator
from the second floor
562
00:34:04,992 --> 00:34:08,261
to the fourth floor,
but ceased to exist in between.
563
00:34:08,296 --> 00:34:09,996
And another thing.
564
00:34:10,031 --> 00:34:12,966
Quantum elevators only stop
at certain floors.
565
00:34:13,000 --> 00:34:16,403
The sizes of the electron
orbits are strictly limited,
566
00:34:16,437 --> 00:34:19,272
and different
for the atoms of every element.
567
00:34:20,808 --> 00:34:23,143
That's why the elements
are different.
568
00:34:23,177 --> 00:34:24,511
The chemistry
of anything is determined
569
00:34:24,545 --> 00:34:26,113
by its electron orbits.
570
00:34:26,147 --> 00:34:29,015
The force that holds
an electron in orbit
571
00:34:29,050 --> 00:34:30,851
has nothing to do with gravity.
572
00:34:30,885 --> 00:34:34,421
It's a force
of electrical attraction.
573
00:34:34,455 --> 00:34:36,757
The electron dances a wavy ring
574
00:34:36,791 --> 00:34:39,025
around the central nucleus
of a hydrogen atom.
575
00:34:39,060 --> 00:34:41,828
And makes quantum leaps
from orbit to orbit.
576
00:34:41,863 --> 00:34:43,130
Up or down.
577
00:34:43,164 --> 00:34:44,531
The larger the orbit,
578
00:34:44,565 --> 00:34:46,600
the greater the energy
of an electron.
579
00:34:46,634 --> 00:34:49,002
An electron has
580
00:34:49,036 --> 00:34:51,171
to get energy to leap
to a larger orbit.
581
00:34:51,205 --> 00:34:54,007
And it has to lose energy
to jump back down.
582
00:34:54,041 --> 00:34:57,344
Every upward leap
is caused by...
583
00:34:57,378 --> 00:35:00,781
an atom absorbing a light wave.
584
00:35:00,815 --> 00:35:04,618
But we have no idea what causes
the downward leaps.
585
00:35:04,652 --> 00:35:08,221
What we do know that such leaps
always produce a light wave
586
00:35:08,256 --> 00:35:10,891
whose color matches
the energy difference
587
00:35:10,958 --> 00:35:12,692
between the orbitals.
588
00:35:17,598 --> 00:35:22,002
The Sun's surface radiates
light waves of all colors.
589
00:35:22,036 --> 00:35:23,837
If you look at sunlight
through a prism,
590
00:35:23,871 --> 00:35:25,872
you'll see its spectrum.
591
00:35:28,509 --> 00:35:31,344
When you magnify the spectrum
with a telescope,
592
00:35:31,379 --> 00:35:33,246
as Joseph Fraunhofer did,
593
00:35:33,281 --> 00:35:34,848
you raise the curtain
594
00:35:34,882 --> 00:35:38,084
on the electron dance
within the atom.
595
00:35:38,119 --> 00:35:40,320
When the energy
of the electron flags,
596
00:35:40,354 --> 00:35:42,022
and it drops
to a lower orbital,
597
00:35:42,056 --> 00:35:44,424
the light wave
it emits scatters.
598
00:35:44,458 --> 00:35:46,860
Most of it doesn't reach us.
599
00:35:46,894 --> 00:35:48,428
That leaves a dark gap
600
00:35:48,462 --> 00:35:51,298
or black vertical line
in the spectrum.
601
00:35:51,399 --> 00:35:53,934
These dark lines
are the shadows
602
00:35:53,968 --> 00:35:55,569
cast by hydrogen atoms
603
00:35:55,603 --> 00:35:57,537
in the atmosphere of the Sun.
604
00:35:57,572 --> 00:36:00,306
Sodium atoms cast
different shadows.
605
00:36:00,308 --> 00:36:03,376
Their electrons dance
to a different tune.
606
00:36:03,411 --> 00:36:05,278
A grain of table salt
is composed
607
00:36:05,313 --> 00:36:07,113
of sodium and chlorine atoms.
608
00:36:07,148 --> 00:36:09,583
Ten million billion of them
609
00:36:09,617 --> 00:36:11,585
doing their crazy dances
610
00:36:11,619 --> 00:36:14,454
in a single grain of salt.
611
00:36:14,488 --> 00:36:17,390
And a single iron atom
with 26 electrons
612
00:36:17,425 --> 00:36:19,759
is like a great
big production number
613
00:36:19,794 --> 00:36:23,096
in a Broadway musical.
614
00:36:25,532 --> 00:36:29,402
When you look at a star
with a spectroscope,
615
00:36:29,437 --> 00:36:31,872
you see the dark lines
from all the elements
616
00:36:31,906 --> 00:36:33,540
in its atmosphere.
617
00:36:33,574 --> 00:36:35,442
Show me the spectrum
of anything,
618
00:36:35,476 --> 00:36:38,245
whether here on Earth
or from a distant star,
619
00:36:38,279 --> 00:36:41,314
and I'll tell you
what it's made of.
620
00:36:41,349 --> 00:36:44,951
Fraunhofer's lines are
the atomic signatures
621
00:36:44,986 --> 00:36:49,022
of the elements writ large
across the cosmos.
622
00:36:49,024 --> 00:36:51,057
As with every
other major revelation
623
00:36:51,092 --> 00:36:53,593
in the history of science,
it opened the way
624
00:36:53,628 --> 00:36:56,596
to newer and deeper mysteries.
625
00:36:56,631 --> 00:36:59,599
And to the revelation
that there were
626
00:36:59,634 --> 00:37:02,669
many more secrets
hiding in the light.
627
00:37:15,967 --> 00:37:18,885
When Joseph Fraunhofer combined
a prism with a telescope
628
00:37:18,887 --> 00:37:21,171
and turned it toward the skies,
629
00:37:21,173 --> 00:37:24,674
he brought the stars
much closer to us.
630
00:37:35,653 --> 00:37:38,388
When he was only 39,
631
00:37:38,390 --> 00:37:40,557
he contracted a fatal illness.
632
00:37:40,559 --> 00:37:43,226
Perhaps as a result of his
early and long-term exposure
633
00:37:43,228 --> 00:37:46,162
to the toxic chemicals
of glassmaking.
634
00:37:46,164 --> 00:37:50,166
You never know where
the next genius will come from.
635
00:37:54,038 --> 00:37:58,608
How many of them do we leave
in the rubble?
636
00:37:58,610 --> 00:38:01,878
The prince and his kingdom
were immeasurably enriched
637
00:38:01,880 --> 00:38:05,248
by that act of kindness
to a poor orphan.
638
00:38:05,250 --> 00:38:07,684
Fraunhofer's discoveries
transformed Bavaria
639
00:38:07,686 --> 00:38:11,955
from a rural backwater
to a technological powerhouse.
640
00:38:13,791 --> 00:38:16,159
As he lay dying,
the government was desperate
641
00:38:16,161 --> 00:38:19,129
to preserve every shred
of his precious knowledge
642
00:38:19,131 --> 00:38:21,431
about the high technology
of optical glass.
643
00:38:24,468 --> 00:38:26,403
But it could only be divulged
to a person
644
00:38:26,405 --> 00:38:28,605
with top security clearance--
645
00:38:28,607 --> 00:38:30,373
the director of the mint.
646
00:38:30,375 --> 00:38:34,244
(no voice)
647
00:38:47,458 --> 00:38:50,060
The government kept
Fraunhofer's technology
648
00:38:50,062 --> 00:38:51,961
for making perfect
optical glass
649
00:38:51,963 --> 00:38:55,231
a State secret
for another hundred years.
650
00:38:55,233 --> 00:38:57,233
This would prove
to be a major obstacle
651
00:38:57,268 --> 00:38:59,736
for someone we'll meet later
in our journey.
652
00:38:59,770 --> 00:39:02,305
But Fraunhofer would allow
no such secrecy
653
00:39:02,339 --> 00:39:04,908
where his pure scientific
research was concerned.
654
00:39:04,942 --> 00:39:08,545
He knew that science requires
openness to flourish;
655
00:39:08,579 --> 00:39:12,615
that our understanding of nature
belongs to the world.
656
00:39:12,650 --> 00:39:15,552
As soon as Fraunhofer discovered
the spectral lines,
657
00:39:15,586 --> 00:39:18,121
he published everything
he knew about them.
658
00:39:18,155 --> 00:39:20,957
And the reverberations
of his momentous discovery
659
00:39:21,024 --> 00:39:23,760
echo still.
660
00:39:26,931 --> 00:39:30,900
His spectral lines revealed
that the visible cosmos
661
00:39:30,935 --> 00:39:34,204
is all made
of the same elements.
662
00:39:37,041 --> 00:39:39,509
The planets...
663
00:39:47,651 --> 00:39:50,120
The stars...
664
00:39:54,492 --> 00:39:56,559
The galaxies...
665
00:40:00,865 --> 00:40:03,867
We, ourselves,
and all of life...
666
00:40:10,541 --> 00:40:14,077
The same star stuff.
667
00:40:19,517 --> 00:40:21,184
He made it possible
for us to know
668
00:40:21,218 --> 00:40:23,686
what's in the atmosphere
of other worlds.
669
00:40:26,157 --> 00:40:29,793
And in galaxies millions
of light-years away.
670
00:40:29,827 --> 00:40:31,828
Spectral lines revealed
not only the composition
671
00:40:31,862 --> 00:40:34,330
of far-off objects,
but also their motion
672
00:40:34,365 --> 00:40:36,533
towards or away from us.
673
00:40:36,567 --> 00:40:39,636
Using them, we discovered
that our universe is expanding.
674
00:40:39,670 --> 00:40:43,239
But perhaps the greatest
revelation of spectroscopy
675
00:40:43,274 --> 00:40:46,075
is the discovery
of the thing it cannot see.
676
00:40:52,082 --> 00:40:54,250
A hidden universe
of dark matter
677
00:40:54,285 --> 00:40:57,520
six times more massive
than the familiar cosmos.
678
00:40:57,555 --> 00:40:59,722
It's made
of some mysterious substance
679
00:40:59,757 --> 00:41:04,327
that does not emit, reflect
or absorb any kind of light.
680
00:41:04,361 --> 00:41:06,813
We only know it's there
because of its gravity,
681
00:41:06,864 --> 00:41:08,932
which pulls on all the galaxies
682
00:41:08,966 --> 00:41:11,701
and speeds up
the visible stars within them.
683
00:41:15,706 --> 00:41:19,175
There are many more kinds of
light than our eyes can see.
684
00:41:19,210 --> 00:41:22,612
Confining our perception
of nature to visible light
685
00:41:22,646 --> 00:41:24,948
is like listening to music
686
00:41:24,982 --> 00:41:26,549
in only one octave.
687
00:41:26,584 --> 00:41:29,085
(musical notes play,
confined to one octave)
688
00:41:29,119 --> 00:41:31,120
There are so many more.
689
00:41:31,155 --> 00:41:33,089
They differ only in wavelength,
690
00:41:33,123 --> 00:41:35,225
but over a huge range.
691
00:41:35,259 --> 00:41:37,827
For instance, infrared light...
692
00:41:39,430 --> 00:41:43,132
(musical notes play
in a higher octave)
693
00:41:43,167 --> 00:41:46,302
...the kind that
William Herschel discovered
694
00:41:46,337 --> 00:41:48,104
Or X-ray light.
695
00:41:48,138 --> 00:41:50,473
(musical notes play
in a still-higher octave)
696
00:41:53,177 --> 00:41:55,245
Or radio light.
697
00:41:55,279 --> 00:41:57,614
(musical notes play
in a lower octave)
698
00:41:59,984 --> 00:42:01,818
Or in gamma-ray light.
699
00:42:01,852 --> 00:42:04,254
(music notes play in the highest
octave humans can hear)
700
00:42:07,625 --> 00:42:10,894
These are not just different
ways of seeing the same thing.
701
00:42:10,928 --> 00:42:12,495
These other kinds of light
702
00:42:12,529 --> 00:42:16,132
reveal different objects
and phenomena in the cosmos.
703
00:42:16,166 --> 00:42:19,335
In gamma-ray light, for example,
we can see mysterious explosions
704
00:42:19,370 --> 00:42:21,104
in distant galaxies
705
00:42:21,138 --> 00:42:23,439
that we would otherwise miss.
706
00:42:26,377 --> 00:42:29,245
And in microwave light,
we can see all the way back
707
00:42:29,280 --> 00:42:31,681
to the birth of the universe.
708
00:42:34,218 --> 00:42:37,520
We have only
just opened our eyes.
709
00:42:39,556 --> 00:42:42,492
(range of octaves play in George
Gershwin's "Rhapsody in Blue")
710
00:42:50,301 --> 00:42:42,492
Captioned by
Media Access Group at WGBH
access.wgbh.org