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¶ ¶
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(sail rustling)
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NEIL DEGRASSE TYSON:
The dream of becoming
a citizen of the cosmos
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was born here,
more than two millennia ago,
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in the city of Alexandria,
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named after and conceived by
its dead conqueror,
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Alexander the Great.
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The Ptolemys, the Greek kings
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who inherited the Egyptian
portion of Alexander's empire,
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built this library
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and its associated
research institution.
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Rarely, if ever,
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before or since,
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has there been a government
that was willing to spend
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so much of its
gross national product
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on the acquisition of knowledge.
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And it paid off.
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Big time.
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Every ship entering
Alexandria's harbor
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was searched--
not for contraband,
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but for books that might be
copied and stored here,
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in what was then
the greatest library on Earth.
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Here, Eratosthenes,
one of the chief librarians,
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accurately calculated
the size of the Earth
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and invented geography.
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Pythagoras.
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Hypatia.
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Euclid.
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Euclid set forth
the precepts of geometry
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in a textbook that remained
in use for 2,300 years.
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The Old Testament Bible
comes down to us
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mainly from the Greek
translations made here.
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The original manuscripts
of the masterpieces
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of Greek
comedy and drama, poetry,
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science, engineering,
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medicine and history--
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the total work product
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of the awakening of ancient
civilization-- were kept here.
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Estimates vary
on the total number of scrolls.
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They range from 500,000
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to nearly a million.
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And all of it...
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all of this
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is but a tiny fraction
of the information
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that you have at your fingertips
at this very moment.
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The collective knowledge
of our species,
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our own electronic
Library of Alexandria,
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may be accessed by anyone
who has a device
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and the interest
and the freedom to do so.
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This was not true
in Alexandria,
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where knowledge belonged
to the elite.
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So in the fourth century AD,
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when the mob came
to destroy the library
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and the genius
of classical civilization,
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there were not enough people
to defend it.
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What will happen the next time
the mob comes?
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¶ ¶
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¶ ¶
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¶ ¶
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¶ ¶
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DEGRASSE TYSON:
We've come a long way together,
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traveling from deep inside
the heart of an atom
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clear out
to the cosmic horizon,
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and from the beginning of time
to the distant future.
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I think we're ready
to perform an experiment.
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It's not the kind of experiment
that requires a laboratory.
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You can do it in your head.
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It's called
a "thought experiment."
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Pick a star--
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any one of the hundreds
of billions of stars
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in our Milky Way Galaxy,
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which is just one galaxy
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out of the hundred billion
in the known universe.
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How about that star?
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Or that one?
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Okay, this one.
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It's orbited by dozens
of planets and moons.
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Suppose, on one of them,
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there lives
an intelligent species,
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one the ten million life-forms
on that planet,
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and there's a subgroup
of that species
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who believe they have it
all figured out--
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their world is the center
of the universe,
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a universe made for them,
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and that they know everything
they need to know about it--
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their knowledge is complete.
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How seriously
would you take their claim?
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Our ancestors believed
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the universe was made for them.
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It was natural to assume
that we were at the center.
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After all,
it looks like the Sun and stars
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all revolve around us.
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We still speak
of the Sun "rising."
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The architecture of
our language, myths and dreams
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comes from
that prescientific age.
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This is our planet
as it was known then,
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just before Columbus set sail.
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This first globe of the Earth
was cutting-edge
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when Martin Behaim
made it in 1492.
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Like everyone else, he believed
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that the jigsaw puzzle
of geography was complete.
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There were three continents:
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Europe, Africa and Asia,
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and only the great world ocean
in between.
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Behaim had no clue that North
and South America even existed.
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It's easy to feel smug, right?
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Well, the fact is Martin Behaim
knew infinitely more
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about his world, the Earth,
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than we know about ours,
the universe.
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A recent lesson in humility
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will serve to illustrate.
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In 1912, Victor Hess
made a series of voyages
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into the sky above Austria,
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and found the thing
that scientists love best...
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...a mystery
that defied understanding
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in terms of conventional
scientific wisdom.
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And even today,
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a century later,
we are still searching
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for a complete explanation
of what Hess found.
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A new kind of energy
had recently been discovered:
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radioactivity.
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It was given off
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by certain elements,
like radium.
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But it was also
found in the air,
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even far away
from radioactive rocks.
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It was everywhere.
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Where did this
strange energy come from?
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No one knew.
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Hess suspected that it might
come from above the Earth.
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To test his hypothesis,
he carried radiation detectors
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high into the sky.
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During a risky ascent
in a hydrogen balloon,
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he attained an altitude
of more than three miles.
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When he reached the thin, cold,
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upper half of the atmosphere...
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(wind whistles)
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...he found that the radiation
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was more than twice
as strong as on the ground.
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The radiation
must be coming from above.
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That's why its intensity
was weaker on the ground--
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the Earth's atmosphere
was absorbing most of it.
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Some thought that the radiation
might come from the Sun.
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To test that idea,
Hess timed one of his ascents
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to coincide
with a solar eclipse.
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But the eclipse had
no effect on the radiation.
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Hess also found
that the radiation
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was just as strong at night
as in daylight.
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It was coming from above,
but not from the Sun.
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What Hess did not know
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was that the solar wind
doesn't move that quickly.
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And so, for the wrong reason,
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he came
to the right conclusion.
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Hess had discovered
cosmic rays--
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showers of subatomic particles
that crisscross the universe
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at literally the speed of light.
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Without the shielding effect
of the Earth's atmosphere,
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they would be lethal.
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Some cosmic rays
can carry as much energy
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as a bullet fired from a rifle.
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It would take decades
to trace those cosmic rays
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back to a death
of unimaginable violence.
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DEGRASSE TYSON: The cosmic rays
that Victor Hess detected
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in the skies above Austria
posed a mystery to scientists.
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Radioactivity
in minerals on Earth--
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like uranium ore--
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comes from the disintegration
of atoms.
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But cosmic rays were
of a different nature.
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They were far more powerful
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than anything known
in Hess's world.
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Scientists wondered
for two decades
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what could possibly produce
cosmic rays.
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Enter Fritz Zwicky,
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the most brilliant man
you've never heard of.
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In 1933,
he and a colleague discovered
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that some stars flare up
to become as bright
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as their entire galaxy
for a few weeks,
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before fading out again.
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Fritz Zwicky was
the first person
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to understand
what just happened.
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He correctly surmised
that this is the way
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a massive star dies--
it blows
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its guts out into space.
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He called this kind of
stellar death a "supernova"...
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...and predicted
that the dying star would shrink
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from about a million miles
across to only ten.
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This corpse would be so dense
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that a single grain of it
would weigh as much
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as the Great Pyramid in Egypt.
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It would consist almost entirely
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of subatomic particles
called neutrons,
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so he named these bizarre
objects "neutron stars."
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And 35 years after Zwicky
predicted their existence,
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astronomers began to find them.
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We call them "pulsars"
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when they spin rapidly and emit
regular pulses of radio energy.
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Supernovas and neutron stars
could account
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for a wide range of cosmic rays,
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but not
the most energetic ones.
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Nothing yet known to science
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can explain them,
and we're fine with that.
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It's one of the things
I love about science,
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we don't have to pretend
we have all the answers.
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Zwicky also came up
with the idea
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that the gravity of a galaxy
warps the fabric
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of space around it,
to act like a lens.
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This distorts
and magnifies light
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from any other galaxy lying
directly behind it.
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So, astronomers on Earth
would see multiple images
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of that same distant galaxy,
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deformed,
as in a funhouse mirror.
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40 years after this prediction,
we started finding them, too.
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And Zwicky made yet another
discovery back in the 1930s.
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While studying
the Coma Cluster of galaxies,
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he noticed something funny
about the way they moved.
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The galaxies were going
way too fast,
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so fast that they should've been
flying apart from each other,
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because all the stars
in all those galaxies
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had far too little gravity
to hold the cluster together.
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Zwicky thought
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that something else must be
binding them to each other.
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That mysterious
missing component
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would have to weigh something
like 50 times as much
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as the stars themselves.
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But no one paid much attention
to this wild notion.
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Just another one
of Zwicky's crazy ideas.
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In our solar system,
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the innermost planet, Mercury,
moves much faster
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than the outermost one, Neptune.
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And that makes sense, right?
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The harder you push or pull on
something, the faster it goes.
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The Sun's gravity weakens
with increasing distance,
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so, the planets that are farther
from the Sun move more slowly.
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Everyone expected that the
outermost stars in a galaxy
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would act the same way.
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Most of the stars are
concentrated towards the center,
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so, their collective gravity
pulls on the other stars
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the same way
the Sun pulls on the planets.
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But in the 1970s,
when astronomer
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Vera Rubin studied
the Andromeda Galaxy,
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she discovered that the outer
stars obeyed no such rule.
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Unlike the outer planets
of the solar system,
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the outer stars in the galaxy
were all going at the same speed
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as the stars
that were closer in,
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and they were moving way faster
than expected.
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"That's funny," Vera thought.
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"There must be something weird
about the Andromeda Galaxy."
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So she looked at another galaxy.
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Same story.
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And another.
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Vera studied 60 galaxies
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and found that all of them
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seemed to be violating
the Law of Gravity,
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a core principle of physics.
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00:15:03,686 --> 00:15:07,021
After some initial
healthy skepticism,
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00:15:07,056 --> 00:15:09,057
her colleagues looked
for themselves,
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and found that Vera was right.
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It's not that Isaac Newton had
gotten the Law of Gravity wrong;
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00:15:15,564 --> 00:15:18,099
Vera Rubin had discovered
that the gravity
259
00:15:18,133 --> 00:15:20,201
of something massive
and invisible
260
00:15:20,235 --> 00:15:24,439
was forcing the stars
to go fast.
261
00:15:24,473 --> 00:15:29,944
And then, someone remembered
crazy old Fritz Zwicky,
262
00:15:29,979 --> 00:15:32,914
and the unknown source
of gravity
263
00:15:32,948 --> 00:15:34,449
in the galaxy clusters
264
00:15:34,483 --> 00:15:38,553
that he called "dark matter,"
back in 1933.
265
00:15:44,793 --> 00:15:47,028
Vera Rubin had verified
the existence
266
00:15:47,062 --> 00:15:49,697
of a new, much larger cosmos.
267
00:15:49,732 --> 00:15:51,966
And just like the one
we thought we knew,
268
00:15:52,001 --> 00:15:54,035
it was filled with mystery.
269
00:15:54,069 --> 00:15:57,538
Dark matter
is completely unobservable,
270
00:15:57,573 --> 00:15:59,340
except
for its gravitational effect,
271
00:15:59,342 --> 00:16:04,045
which makes visible stars
and galaxies move faster.
272
00:16:04,079 --> 00:16:07,782
Its nature is another
deep mystery.
273
00:16:07,816 --> 00:16:10,918
Rubin had provided the evidence
for an invisible universe
274
00:16:10,953 --> 00:16:15,723
nearly ten times more massive
than the one we thought we knew.
275
00:16:15,758 --> 00:16:17,792
It was as if we had been
standing on the seashore
276
00:16:17,859 --> 00:16:19,894
at night, mistakenly believing
277
00:16:19,928 --> 00:16:23,164
that the froth on the waves was
all there was to the ocean.
278
00:16:23,198 --> 00:16:26,801
Vera Rubin looked at the stars
and realized
279
00:16:26,835 --> 00:16:29,404
they were merely the foam
on the waves,
280
00:16:29,438 --> 00:16:34,575
and that the greatest part
of the ocean remained unknown.
281
00:16:34,610 --> 00:16:35,927
But wait.
282
00:16:35,929 --> 00:16:37,945
It gets crazier.
283
00:16:39,581 --> 00:16:41,566
laxy,
284
00:16:41,617 --> 00:16:43,718
a few hundred billion stars,
285
00:16:43,752 --> 00:16:46,220
plus the clouds
of gas and dust,
286
00:16:46,255 --> 00:16:49,257
the stuff of once
and future stars--
287
00:16:49,274 --> 00:16:54,228
and about a hundred billion
other galaxies-- all of that,
288
00:16:54,263 --> 00:16:57,498
including those uncounted
billions of trillions
289
00:16:57,533 --> 00:17:00,568
of planets, moons, and comets--
290
00:17:00,602 --> 00:17:04,672
amounts to only five percent
of what is actually there.
291
00:17:04,707 --> 00:17:06,841
Because there's a bigger
unsolved mystery
292
00:17:06,875 --> 00:17:08,876
than dark matter--
293
00:17:08,911 --> 00:17:13,047
dark energy, which makes up
even more of the cosmos
294
00:17:13,082 --> 00:17:15,183
and drives its expansion.
295
00:17:15,217 --> 00:17:17,885
And it was Fritz Zwicky's
supernovas
296
00:17:17,920 --> 00:17:21,489
that lit the way to the
revelation of its existence.
297
00:17:23,926 --> 00:17:28,496
In one scenario, a star consumes
all of its nuclear fuel...
298
00:17:32,067 --> 00:17:33,534
...then cools,
299
00:17:33,569 --> 00:17:36,270
and suddenly collapses
under its own gravity.
300
00:17:36,305 --> 00:17:39,974
The star rebounds
in a massive explosion,
301
00:17:40,008 --> 00:17:43,911
leaving behind a neutron star
or a black hole.
302
00:17:45,514 --> 00:17:47,949
Since the mass
of the original star
303
00:17:47,983 --> 00:17:49,751
can fall within a wide range,
304
00:17:49,785 --> 00:17:51,319
its peak brightness
as a supernova
305
00:17:51,353 --> 00:17:53,154
can also vary widely.
306
00:17:53,188 --> 00:17:55,890
So, you can't tell
how far away it is
307
00:17:55,892 --> 00:17:57,792
just from how bright it looks.
308
00:17:57,826 --> 00:18:01,295
A relatively nearby supernova
might appear just as bright
309
00:18:01,330 --> 00:18:04,465
as one that was more powerful,
but farther away.
310
00:18:04,500 --> 00:18:07,401
But there's another kind
of supernova
311
00:18:07,436 --> 00:18:09,470
that comes
in only one strength.
312
00:18:09,505 --> 00:18:11,806
It marks the violent
grand finale
313
00:18:11,840 --> 00:18:16,477
of a tango danced
by a giant star and a dwarf.
314
00:18:18,347 --> 00:18:21,149
As the two stars orbit
closely around each other,
315
00:18:21,183 --> 00:18:23,618
the giant sheds
its outer layers of gas
316
00:18:23,652 --> 00:18:25,620
onto the dwarf.
317
00:18:25,654 --> 00:18:28,122
When the added weight
becomes too much
318
00:18:28,157 --> 00:18:29,957
for it to bear,
319
00:18:29,992 --> 00:18:34,529
the dwarf detonates like a
stupendous thermonuclear bomb.
320
00:18:34,563 --> 00:18:36,631
For a few weeks,
321
00:18:36,665 --> 00:18:39,267
the brilliance
of such a supernova rivals
322
00:18:39,301 --> 00:18:42,603
the combined light
of all the stars in its galaxy.
323
00:18:42,638 --> 00:18:44,438
This kind of supernova
324
00:18:44,473 --> 00:18:46,974
always has the same
maximum power output,
325
00:18:47,009 --> 00:18:50,744
about five billion times
brighter than our Sun.
326
00:18:50,813 --> 00:18:52,547
With big telescopes,
327
00:18:52,581 --> 00:18:54,982
we can see them
in galaxies very far away,
328
00:18:55,017 --> 00:18:58,519
out toward the edge
of the observable universe.
329
00:19:07,262 --> 00:19:10,364
Because all such supernovas
have the same wattage,
330
00:19:10,399 --> 00:19:13,334
they're ideal tools
for measuring distances
331
00:19:13,368 --> 00:19:15,570
to the farthest reaches
of the universe.
332
00:19:15,604 --> 00:19:18,506
We call them
"standard candles."
333
00:19:23,178 --> 00:19:28,816
In 1929, Edwin Hubble discovered
that the universe is expanding.
334
00:19:28,851 --> 00:19:32,086
The distant galaxies are
drifting away from one another.
335
00:19:32,120 --> 00:19:33,738
Later, we learned
336
00:19:33,789 --> 00:19:36,724
that the expansion began
some 14 billion years ago
337
00:19:36,758 --> 00:19:41,229
with the explosive birth
of the universe-- the big bang.
338
00:19:42,898 --> 00:19:44,932
Everybody assumed
339
00:19:44,967 --> 00:19:47,335
that the rate of expansion
would be slowing down,
340
00:19:47,369 --> 00:19:49,103
due to the mutual pull
of gravity
341
00:19:49,137 --> 00:19:50,872
between all the parts
of the universe.
342
00:19:50,906 --> 00:19:52,740
If there is enough dark matter,
343
00:19:52,774 --> 00:19:56,060
its gravity would eventually
bring the expansion to a stop,
344
00:19:56,111 --> 00:19:58,913
and the universe would
then fall back on itself.
345
00:19:58,947 --> 00:20:02,116
In that case, everything
would eventually collapse
346
00:20:02,150 --> 00:20:03,918
in a big crunch.
347
00:20:03,952 --> 00:20:07,288
On the other hand, if the
universe had less dark matter,
348
00:20:07,322 --> 00:20:09,390
the expansion
would continue forever,
349
00:20:09,424 --> 00:20:12,293
just getting slower
and slower.
350
00:20:12,327 --> 00:20:14,896
Two competing teams
of astronomers
351
00:20:14,930 --> 00:20:18,199
were observing those supernovas
in distant galaxies.
352
00:20:18,233 --> 00:20:19,867
It turned out to be another one
353
00:20:19,902 --> 00:20:22,303
of those
"that's funny" moments.
354
00:20:22,337 --> 00:20:25,640
In 1998, both teams
independently came
355
00:20:25,674 --> 00:20:27,308
to the same conclusion:
356
00:20:27,342 --> 00:20:29,710
The expansion isn't
slowing down at all...
357
00:20:29,761 --> 00:20:31,479
it's speeding up.
358
00:20:31,513 --> 00:20:35,116
This means the universe will
continue to expand forever.
359
00:20:35,150 --> 00:20:38,920
There seems to be a mysterious
force in the universe,
360
00:20:38,954 --> 00:20:41,923
one that overwhelms gravity
on the grandest scale
361
00:20:41,957 --> 00:20:44,492
to push the cosmos apart.
362
00:20:44,526 --> 00:20:47,228
Most of the energy
of the universe is bound up
363
00:20:47,262 --> 00:20:48,729
in this unknown force.
364
00:20:48,764 --> 00:20:51,132
We call it "dark energy,"
365
00:20:51,166 --> 00:20:53,834
but that name,
like "dark matter,"
366
00:20:53,869 --> 00:20:57,305
is merely a code word
for our ignorance.
367
00:20:57,339 --> 00:20:59,674
It's okay not
to know all the answers.
368
00:20:59,708 --> 00:21:01,676
It's better
to admit our ignorance
369
00:21:01,710 --> 00:21:04,078
than to believe answers
that might be wrong.
370
00:21:04,112 --> 00:21:07,581
Pretending to know everything
closes the door
371
00:21:07,616 --> 00:21:09,617
to finding out
what's really there.
372
00:21:10,652 --> 00:21:13,154
Tonight, our ships sail
373
00:21:13,188 --> 00:21:16,624
into even more exotic waters.
374
00:21:16,658 --> 00:21:18,659
Come with me.
375
00:21:25,984 --> 00:21:28,252
DEGRASSE TYSON: Only two of
our ships have ventured
376
00:21:28,287 --> 00:21:31,756
into the great dark ocean
of interstellar space.
377
00:21:31,790 --> 00:21:35,626
The longest odyssey
in all of history
378
00:21:35,661 --> 00:21:38,929
was launched back in 1977--
379
00:21:38,964 --> 00:21:42,667
NASA's Voyager 1 and 2.
380
00:21:42,701 --> 00:21:47,004
The Voyagers move
about 40,000 miles an hour.
381
00:21:47,039 --> 00:21:49,824
They gave us
our first close-up look
382
00:21:49,875 --> 00:21:51,909
at Jupiter's Great Red Spot,
383
00:21:51,943 --> 00:21:55,813
a hurricane three times
the size of Earth
384
00:21:55,847 --> 00:21:59,784
and one that's been raging
since at least 1644,
385
00:21:59,818 --> 00:22:01,519
when it was first observed.
386
00:22:01,553 --> 00:22:05,323
For all we know, it could be
thousands of years old.
387
00:22:05,357 --> 00:22:08,659
The Voyagers discovered
the first active volcano
388
00:22:08,694 --> 00:22:12,630
on another world,
on Jupiter's moon Io...
389
00:22:14,199 --> 00:22:16,334
...and an ocean
beneath the icy surface
390
00:22:16,368 --> 00:22:17,968
of the moon Europa...
391
00:22:21,673 --> 00:22:25,209
...with at least twice as much
water as we have here on Earth.
392
00:22:28,313 --> 00:22:31,682
The Voyagers dared to fly
across Saturn's rings
393
00:22:31,717 --> 00:22:36,053
and revealed that they were
made of hundreds of thin bands
394
00:22:36,088 --> 00:22:37,888
of orbiting snowballs.
395
00:22:41,259 --> 00:22:43,894
On Saturn's giant moon Titan,
396
00:22:43,929 --> 00:22:48,065
Voyager detected an atmosphere
four times denser than Earth's.
397
00:22:48,100 --> 00:22:52,837
That hinted at the existence
of hydrocarbon seas on Titan,
398
00:22:52,871 --> 00:22:54,538
which we later confirmed.
399
00:22:56,508 --> 00:22:58,476
Voyager 2 gave us
our first portrait
400
00:22:58,510 --> 00:23:02,313
of the outermost planet,
Neptune...
401
00:23:02,347 --> 00:23:06,217
where the winds roar
at 1,000 miles per hour...
402
00:23:08,053 --> 00:23:10,921
...and its moon Triton,
where geysers
403
00:23:10,956 --> 00:23:15,459
of boiling nitrogen
shoot five miles high.
404
00:23:18,597 --> 00:23:21,399
Voyager successfully completed
its mission of discovery
405
00:23:21,433 --> 00:23:23,234
to the outer planets,
406
00:23:23,268 --> 00:23:25,236
but its odyssey
into the darkness
407
00:23:25,270 --> 00:23:27,271
was just beginning.
408
00:23:29,574 --> 00:23:31,275
35 years after its launch,
409
00:23:31,309 --> 00:23:33,944
Voyager 1 became the first
of our spacecraft
410
00:23:33,979 --> 00:23:36,847
to enter an uncharted realm.
411
00:23:36,882 --> 00:23:40,084
The Sun is constantly
shooting out streams
412
00:23:40,118 --> 00:23:42,420
of charged particles
in all directions,
413
00:23:42,454 --> 00:23:44,755
moving at a million miles
an hour.
414
00:23:44,790 --> 00:23:49,460
This solar wind blows
a vast magnetic bubble,
415
00:23:49,561 --> 00:23:53,464
our heliosphere, that extends
beyond the outer planets.
416
00:23:53,466 --> 00:23:58,803
It pushes out against the
thin gas of interstellar space.
417
00:23:58,837 --> 00:24:03,407
There's a border where
one ends and the other begins.
418
00:24:03,442 --> 00:24:05,576
Voyager 1 reported back
to Earth
419
00:24:05,610 --> 00:24:08,112
that its detectors
were being pummeled
420
00:24:08,146 --> 00:24:09,647
by more and more cosmic rays.
421
00:24:09,664 --> 00:24:12,082
Until then, we didn't know
422
00:24:12,117 --> 00:24:14,385
where the interstellar
ocean began.
423
00:24:14,419 --> 00:24:16,654
Voyager 1 pressed on
424
00:24:16,688 --> 00:24:19,874
past a boundary
we had never crossed before.
425
00:24:19,925 --> 00:24:23,694
The heliosphere shields us from
most of the deadly cosmic rays.
426
00:24:23,795 --> 00:24:25,930
When stormy solar winds blow,
427
00:24:25,964 --> 00:24:28,165
this zone of protection grows;
428
00:24:28,200 --> 00:24:30,301
in calm solar weather,
it shrinks.
429
00:24:30,335 --> 00:24:33,604
When a star goes supernova
in our galactic neighborhood...
430
00:24:35,440 --> 00:24:37,675
...the debris
from the exploded star
431
00:24:37,709 --> 00:24:40,678
pushes the heliosphere
back towards the Sun.
432
00:24:40,712 --> 00:24:42,313
If it's strong enough
to push it
433
00:24:42,347 --> 00:24:44,248
all the way back
to Earth's orbit,
434
00:24:44,282 --> 00:24:49,320
our planet gets a radioactive
bath of supernova debris.
435
00:24:49,354 --> 00:24:52,156
Luckily,
this doesn't happen very often.
436
00:24:52,190 --> 00:24:55,593
The last one was perhaps
two million years ago.
437
00:24:55,627 --> 00:24:58,762
A neighboring star explodes
a million years
438
00:24:58,797 --> 00:25:02,433
before there's even such a thing
as the human species.
439
00:25:02,467 --> 00:25:04,935
How can we possibly know this?
440
00:25:04,970 --> 00:25:07,771
Because the dying star
left its traces
441
00:25:07,806 --> 00:25:10,274
miles below the surface
of the ocean.
442
00:25:10,308 --> 00:25:15,012
Manganese nodules,
small rocks like this one,
443
00:25:15,046 --> 00:25:19,517
are scattered over much
of the deep sea floor.
444
00:25:19,551 --> 00:25:22,353
They grow very slowly.
445
00:25:22,387 --> 00:25:27,124
I'm talking a millimeter
in a million years,
446
00:25:27,158 --> 00:25:31,128
layer upon layer.
447
00:25:31,162 --> 00:25:34,198
These nodules grow
in partnership with bacteria
448
00:25:34,232 --> 00:25:39,069
by taking up minerals dissolved
in the seawater.
449
00:25:39,104 --> 00:25:43,073
A supernova produces
a radioactive form of iron,
450
00:25:43,108 --> 00:25:47,144
unlike anything made
by natural processes on Earth.
451
00:25:47,178 --> 00:25:49,547
Researchers found
telltale traces of this iron
452
00:25:49,581 --> 00:25:51,549
in a thin layer
below the surface
453
00:25:51,583 --> 00:25:53,551
of the manganese nodules.
454
00:25:53,585 --> 00:25:56,387
They used the known rate
of growth of the nodules
455
00:25:56,421 --> 00:25:58,722
to date that layer
and to connect it
456
00:25:58,757 --> 00:26:02,760
to the fate of a star
that perished eons ago.
457
00:26:04,396 --> 00:26:07,264
The difference between
seeing nothing but a pebble
458
00:26:07,299 --> 00:26:11,702
and reading the history of
the cosmos inscribed inside it
459
00:26:11,736 --> 00:26:14,138
is science.
460
00:26:16,291 --> 00:26:20,277
The interstellar ocean
is dark and deep.
461
00:26:20,312 --> 00:26:24,281
Out here, the Sun is just
the brightest star in the sky.
462
00:26:24,299 --> 00:26:27,718
Yet the Voyagers maintain
their regular communications
463
00:26:27,752 --> 00:26:29,820
with NASA's
Jet Propulsion Laboratory,
464
00:26:29,921 --> 00:26:32,523
talking back and forth
across the light-hours
465
00:26:32,557 --> 00:26:35,426
that separate these ships
from their home port.
466
00:26:35,460 --> 00:26:39,263
No other objects touched
by human hands
467
00:26:39,297 --> 00:26:42,616
have ever ventured
this far from home.
468
00:26:48,940 --> 00:26:50,407
Even after they lose
their ability
469
00:26:50,442 --> 00:26:52,476
to respond to our command,
470
00:26:52,510 --> 00:26:54,712
the last and,
by far, the longest phase
471
00:26:54,746 --> 00:26:56,747
of the Voyager mission
will begin.
472
00:27:04,089 --> 00:27:07,257
h Voyagers
rounded Jupiter,
473
00:27:07,292 --> 00:27:09,693
its massive gravity acted
as a slingshot,
474
00:27:09,728 --> 00:27:11,695
flinging them out
of the solar system
475
00:27:11,730 --> 00:27:13,897
to travel among the stars
of our galaxy
476
00:27:13,932 --> 00:27:16,350
for a billion years.
477
00:27:16,401 --> 00:27:18,969
Carl Sagan recognized
that the Voyager mission
478
00:27:19,070 --> 00:27:23,107
offered two free tickets to
something approaching eternity.
479
00:27:23,141 --> 00:27:26,110
He assembled a small team
to create a message
480
00:27:26,177 --> 00:27:29,113
to any civilization
that might, one day,
481
00:27:29,147 --> 00:27:32,483
encounter
the derelict spacecraft.
482
00:27:35,453 --> 00:27:37,621
26 centuries ago,
483
00:27:37,656 --> 00:27:40,490
the Assyrian king Esarhaddon
wrote:
484
00:27:40,492 --> 00:27:43,227
"I had monuments made of bronze
485
00:27:43,261 --> 00:27:45,896
"and inscriptions
of baked clay.
486
00:27:45,930 --> 00:27:49,299
I left them in the foundations
for future times."
487
00:27:49,334 --> 00:27:53,637
These hieroglyphics continue
that ancient tradition.
488
00:27:53,705 --> 00:27:56,640
They are inscribed on the cover
of a message designed
489
00:27:56,675 --> 00:28:01,145
to be read by the beings
of other worlds and times.
490
00:28:02,814 --> 00:28:04,348
What could we possibly
have in common
491
00:28:04,382 --> 00:28:05,816
with an alien civilization
492
00:28:05,850 --> 00:28:08,519
with its own separate
evolutionary history
493
00:28:08,553 --> 00:28:10,788
and one so far advanced
beyond us
494
00:28:10,822 --> 00:28:15,025
that they can patrol
interstellar space?
495
00:28:15,060 --> 00:28:16,593
One thing at least:
496
00:28:16,628 --> 00:28:18,362
a universal language...
497
00:28:18,396 --> 00:28:20,197
science.
498
00:28:20,215 --> 00:28:23,200
It's hard to break the bonds
of gravity.
499
00:28:23,218 --> 00:28:25,469
You can only sail
the cosmic seas
500
00:28:25,503 --> 00:28:28,839
if you speak mathematics
and physics.
501
00:28:28,873 --> 00:28:31,942
Hydrogen is the most common
element in the universe.
502
00:28:31,976 --> 00:28:33,944
The electron in a hydrogen atom
503
00:28:33,978 --> 00:28:35,779
flips the direction of its spin
504
00:28:35,814 --> 00:28:37,781
at a constant rate,
or frequency.
505
00:28:37,816 --> 00:28:41,785
Hydrogen atoms are
like tiny natural clocks--
506
00:28:41,787 --> 00:28:44,621
tick... tock.
507
00:28:44,656 --> 00:28:46,757
Now we have a unit of time
in common
508
00:28:46,858 --> 00:28:48,442
with the extraterrestrials.
509
00:28:48,493 --> 00:28:50,360
This will come in handy
when we get to the next level
510
00:28:50,395 --> 00:28:51,962
of the message.
511
00:28:51,996 --> 00:28:54,565
Here's our return address
in space.
512
00:28:54,599 --> 00:28:57,401
Pulsars are rapidly-spinning
neutron stars
513
00:28:57,435 --> 00:29:00,537
that give off regular bursts
of radio waves.
514
00:29:00,555 --> 00:29:03,240
You can set your clock by them.
515
00:29:03,258 --> 00:29:05,776
The Sun is at the center
of this diagram,
516
00:29:05,860 --> 00:29:09,513
and the lines point
to the 14 nearest pulsars.
517
00:29:09,515 --> 00:29:13,350
A simple code labels each pulsar
with its unique frequency,
518
00:29:13,384 --> 00:29:15,519
using the ticktock
of the hydrogen atom
519
00:29:15,586 --> 00:29:17,254
as the unit of time.
520
00:29:17,288 --> 00:29:20,090
So alien astronomers could use
this diagram
521
00:29:20,125 --> 00:29:22,693
to locate the home star
of the Voyager spacecraft
522
00:29:22,727 --> 00:29:24,328
in our galaxy.
523
00:29:24,362 --> 00:29:25,929
They could also tell
524
00:29:25,964 --> 00:29:27,998
how long ago the spacecraft
was launched.
525
00:29:28,032 --> 00:29:30,200
And that's important
because the Voyager record
526
00:29:30,235 --> 00:29:34,238
has a projected shelf life
of 1,000 million years.
527
00:29:37,275 --> 00:29:38,876
Become an extraterrestrial
archaeologist
528
00:29:38,910 --> 00:29:40,878
for a few moments.
529
00:29:40,912 --> 00:29:44,081
An artifact has been fished out
of the interstellar ocean.
530
00:29:44,115 --> 00:29:45,215
(classical music playing)
531
00:29:45,250 --> 00:29:46,750
It was made by beings
532
00:29:46,785 --> 00:29:48,919
that lived
about a billion years ago.
533
00:29:48,953 --> 00:29:51,121
What would you make of them
and their world?
534
00:29:51,156 --> 00:29:52,289
(guitar playing blues)
535
00:29:52,323 --> 00:29:56,026
They've sent us their music
536
00:29:56,060 --> 00:30:00,130
and greetings
in 59 human languages.
537
00:30:00,165 --> 00:30:03,033
(various languages overlap,
speaking greetings)
538
00:30:03,035 --> 00:30:06,203
NICK SAGAN: Hello from the
children of planet Earth.
539
00:30:06,205 --> 00:30:07,304
DEGRASSE TYSON:
And one whale language.
540
00:30:07,306 --> 00:30:09,306
(whales singing)
541
00:30:09,308 --> 00:30:12,676
And a sound essay that includes
a Saturn V rocket launch.
542
00:30:12,678 --> 00:30:14,511
(jet engine whooshes)
543
00:30:14,513 --> 00:30:17,347
A mother's first words
to her newborn baby.
544
00:30:17,349 --> 00:30:18,849
(baby crying)
545
00:30:18,851 --> 00:30:20,150
WOMAN: Oh, come on now.
546
00:30:20,152 --> 00:30:22,319
Be a good boy... be a good boy.
547
00:30:22,321 --> 00:30:25,122
The brain waves of a young
woman newly fallen in love.
548
00:30:25,124 --> 00:30:28,125
(staticky crackling)
549
00:30:28,127 --> 00:30:31,662
And the sound of a pulsar.
550
00:30:31,696 --> 00:30:33,664
(steady, rhythmic crackling)
551
00:30:33,698 --> 00:30:35,766
(Blind Willie Johnson's
"Dark Was the Night..." playing)
552
00:30:35,800 --> 00:30:40,804
All of that will live
for a billion years.
553
00:30:40,839 --> 00:30:45,642
("Dark Was the Night"
continues, then fades)
554
00:30:53,184 --> 00:30:56,620
How long is a billion years?
555
00:31:02,360 --> 00:31:05,329
press all the time
since the big bang,
556
00:31:05,363 --> 00:31:07,331
the explosive birth
of the universe,
557
00:31:07,365 --> 00:31:09,333
into a single Earth year,
558
00:31:09,367 --> 00:31:12,669
a billion years is
about one month of that year.
559
00:31:12,704 --> 00:31:17,040
What was happening on Earth
a billion years ago?
560
00:31:20,078 --> 00:31:23,080
Most of Earth's land was amassed
into a supercontinent
561
00:31:23,114 --> 00:31:24,781
called Rodinia.
562
00:31:24,816 --> 00:31:28,452
It was a barren desert--
no animals, no plants.
563
00:31:28,486 --> 00:31:30,420
A billion years ago,
there wasn't enough oxygen
564
00:31:30,455 --> 00:31:32,856
in our atmosphere
to form an ozone layer,
565
00:31:32,891 --> 00:31:35,525
and without it,
ultraviolet radiation
566
00:31:35,527 --> 00:31:38,262
prevented life
from colonizing the land.
567
00:31:38,296 --> 00:31:40,797
Rodinia probably looked
more like Mars
568
00:31:40,832 --> 00:31:43,533
than present-day Earth.
569
00:31:43,568 --> 00:31:46,270
The giant world ocean
produced huge rainstorms
570
00:31:46,304 --> 00:31:48,805
causing flooding and erosion.
571
00:31:48,840 --> 00:31:51,942
Glaciers formed, and their
slow but relentless movements
572
00:31:51,976 --> 00:31:55,145
carved the land
into new shapes.
573
00:31:55,179 --> 00:31:58,548
Single-celled organisms
dominated the oceans,
574
00:31:58,583 --> 00:32:02,152
but some existed in colonies
called "microbial mats,"
575
00:32:02,186 --> 00:32:06,890
and the first multicellular
organisms would soon evolve.
576
00:32:06,925 --> 00:32:08,892
And a billion years from now,
577
00:32:08,927 --> 00:32:10,894
what will Earth be like...
578
00:32:10,929 --> 00:32:13,563
long after our cities,
the Egyptian pyramids,
579
00:32:13,598 --> 00:32:16,733
the Rocky Mountains
have all been eroded to dust?
580
00:32:16,768 --> 00:32:19,336
There are few things
we can say with confidence
581
00:32:19,370 --> 00:32:22,372
about such a far distant time.
582
00:32:26,044 --> 00:32:28,545
The only thing
we can say for sure
583
00:32:28,547 --> 00:32:32,349
is that Earth as we know it
will be so changed
584
00:32:32,383 --> 00:32:35,686
that we would
scarcely recognize it as home.
585
00:32:35,720 --> 00:32:39,256
But even a thousand
million years from now,
586
00:32:39,290 --> 00:32:42,793
something of who we were
and the music that we made
587
00:32:42,827 --> 00:32:45,095
in that long-ago spring...
588
00:32:45,129 --> 00:32:47,130
will live on.
589
00:32:52,003 --> 00:32:55,172
In that distant future,
our Sun will have completed
590
00:32:55,206 --> 00:32:58,542
another four orbits around
the center of the galaxy...
591
00:33:06,784 --> 00:33:11,355
...and the Voyagers will have
ventured far from the Sun.
592
00:33:14,692 --> 00:33:17,394
Carl Sagan was a member
of Voyager's imaging team,
593
00:33:17,428 --> 00:33:21,631
and it was his idea that Voyager
take one last picture.
594
00:33:21,666 --> 00:33:23,600
A generation before,
595
00:33:23,701 --> 00:33:26,536
an astronaut on the last
Apollo flight to the Moon
596
00:33:26,571 --> 00:33:29,206
had taken a picture
of the whole Earth--
597
00:33:29,240 --> 00:33:32,409
the planet
as a world without borders.
598
00:33:32,443 --> 00:33:35,812
It became an icon
of a new consciousness.
599
00:33:35,847 --> 00:33:39,983
Carl realized the next step
in this process.
600
00:33:40,018 --> 00:33:43,053
He convinced NASA to turn
the Voyager 1 camera
601
00:33:43,120 --> 00:33:46,857
back towards Earth when the
spacecraft went beyond Neptune
602
00:33:46,924 --> 00:33:50,527
for one last look homeward
at what he called...
603
00:33:50,561 --> 00:33:53,563
the pale blue dot.
604
00:33:59,370 --> 00:34:00,937
CARL SAGAN:
That's here.
605
00:34:00,972 --> 00:34:02,506
That's home.
606
00:34:02,540 --> 00:34:04,107
That's us.
607
00:34:04,142 --> 00:34:06,843
On it, everyone you love,
608
00:34:06,878 --> 00:34:08,879
everyone you know,
609
00:34:08,913 --> 00:34:10,881
everyone you ever heard of,
610
00:34:10,915 --> 00:34:13,550
every human being who ever was,
611
00:34:13,584 --> 00:34:15,952
lived out their lives.
612
00:34:15,987 --> 00:34:19,723
The aggregate
of our joy and suffering,
613
00:34:19,757 --> 00:34:22,559
thousands of confident
religions, ideologies,
614
00:34:22,593 --> 00:34:24,561
and economic doctrines,
615
00:34:24,595 --> 00:34:26,730
every hunter and forager,
616
00:34:26,764 --> 00:34:28,732
every hero and coward,
617
00:34:28,766 --> 00:34:32,202
every creator and destroyer
of civilization,
618
00:34:32,236 --> 00:34:34,204
every king and peasant,
619
00:34:34,238 --> 00:34:36,239
every young couple in love,
620
00:34:36,274 --> 00:34:39,543
every mother and father,
hopeful child,
621
00:34:39,577 --> 00:34:41,812
inventor and explorer,
622
00:34:41,846 --> 00:34:45,482
every teacher of morals,
every corrupt politician,
623
00:34:45,516 --> 00:34:49,586
every superstar,
every supreme leader,
624
00:34:49,620 --> 00:34:53,457
every saint and sinner
in the history of our species,
625
00:34:53,491 --> 00:34:55,492
lived there...
626
00:34:55,494 --> 00:34:57,294
on a mote of dust
627
00:34:57,328 --> 00:35:00,597
suspended... in a sunbeam.
628
00:35:00,599 --> 00:35:04,801
The Earth is
a very small stage
629
00:35:04,836 --> 00:35:08,638
in a vast, cosmic arena.
630
00:35:08,673 --> 00:35:11,908
Think of the rivers of blood
631
00:35:11,943 --> 00:35:15,645
spilled by all those
generals and emperors
632
00:35:15,680 --> 00:35:18,115
so that in glory and triumph
633
00:35:18,149 --> 00:35:21,017
they could become
the momentary masters
634
00:35:21,119 --> 00:35:24,354
of a fraction... of a dot.
635
00:35:24,388 --> 00:35:27,491
Think of the endless
cruelties visited
636
00:35:27,508 --> 00:35:30,927
by the inhabitants
of one corner of this pixel
637
00:35:31,028 --> 00:35:33,930
on the scarcely
distinguishable inhabitants
638
00:35:33,965 --> 00:35:36,016
of some other corner.
639
00:35:36,067 --> 00:35:39,035
How frequent
their misunderstandings,
640
00:35:39,137 --> 00:35:42,105
how eager they are
to kill one another,
641
00:35:42,140 --> 00:35:45,442
how fervent their hatreds.
642
00:35:45,476 --> 00:35:47,978
Our posturings,
643
00:35:48,012 --> 00:35:51,047
our imagined self-importance,
644
00:35:51,082 --> 00:35:53,650
the delusion that we have
some privileged position
645
00:35:53,684 --> 00:35:55,285
in the universe,
646
00:35:55,319 --> 00:35:59,990
are challenged
by this point of pale light.
647
00:36:00,024 --> 00:36:02,025
Our planet...
648
00:36:02,059 --> 00:36:05,061
is a lonely speck in the great,
649
00:36:05,096 --> 00:36:08,165
enveloping cosmic dark.
650
00:36:08,199 --> 00:36:11,001
In our obscurity,
651
00:36:11,035 --> 00:36:13,803
in all this vastness,
652
00:36:13,838 --> 00:36:17,541
there is no hint that help
will come from elsewhere
653
00:36:17,575 --> 00:36:20,510
to save us from ourselves.
654
00:36:20,545 --> 00:36:24,748
The Earth is the only world
known so far to harbor life.
655
00:36:24,765 --> 00:36:26,750
There is nowhere else,
656
00:36:26,784 --> 00:36:28,752
at least in the near future,
657
00:36:28,786 --> 00:36:31,588
to which our species
could migrate.
658
00:36:31,622 --> 00:36:34,390
Visit, yes.
659
00:36:34,392 --> 00:36:36,593
Settle, not yet.
660
00:36:36,627 --> 00:36:38,662
Like it or not,
661
00:36:38,696 --> 00:36:43,233
for the moment, the Earth
is where we make our stand.
662
00:36:43,267 --> 00:36:46,570
It has been said that
astronomy is a humbling
663
00:36:46,587 --> 00:36:50,707
and character-building
experience.
664
00:36:50,741 --> 00:36:53,210
There is perhaps
no better demonstration
665
00:36:53,244 --> 00:36:56,112
of the folly of human conceits
666
00:36:56,114 --> 00:36:59,616
than this distant image.
667
00:36:59,650 --> 00:37:03,220
To me, it underscores
our responsibility
668
00:37:03,254 --> 00:37:05,922
to deal more kindly
with one another
669
00:37:05,957 --> 00:37:08,425
and to preserve and cherish
670
00:37:08,459 --> 00:37:10,627
the pale blue dot,
671
00:37:10,629 --> 00:37:13,763
the only home we've ever known.
672
00:37:20,671 --> 00:37:22,639
DEGRASSE TYSON:
How did we,
673
00:37:22,673 --> 00:37:25,025
tiny creatures living
on that speck of dust,
674
00:37:25,076 --> 00:37:28,378
ever manage to figure out
how to send spacecraft
675
00:37:28,380 --> 00:37:31,247
out among the stars
of the Milky Way?
676
00:37:31,249 --> 00:37:35,619
Only a few centuries ago,
a mere second of cosmic time,
677
00:37:35,653 --> 00:37:38,255
we knew nothing
of where or who we were.
678
00:37:38,289 --> 00:37:41,057
Oblivious to the rest
of the cosmos,
679
00:37:41,092 --> 00:37:43,660
we inhabited a kind of prison--
680
00:37:43,694 --> 00:37:45,645
a tiny universe
681
00:37:45,696 --> 00:37:49,199
bounded by a nutshell.
682
00:37:51,302 --> 00:37:55,572
How did we escape
from the prison?
683
00:37:55,606 --> 00:37:59,509
It was the work
of generations of searchers
684
00:37:59,543 --> 00:38:03,380
who took five
simple rules to heart.
685
00:38:07,285 --> 00:38:09,252
Question authority.
686
00:38:09,287 --> 00:38:12,589
No idea is true
just because someone says so,
687
00:38:12,623 --> 00:38:14,291
including me.
688
00:38:15,276 --> 00:38:17,127
Think for yourself.
689
00:38:20,564 --> 00:38:22,532
Question yourself.
690
00:38:24,885 --> 00:38:27,537
Don't believe anything
just because you want to.
691
00:38:27,571 --> 00:38:32,342
Believing something
doesn't make it so.
692
00:38:32,376 --> 00:38:34,344
Test ideas
by the evidence gained
693
00:38:34,378 --> 00:38:38,048
from observation
and experiment.
694
00:38:38,082 --> 00:38:41,451
If a favorite idea fails
a well-designed test,
695
00:38:41,485 --> 00:38:43,653
it's wrong!
696
00:38:43,688 --> 00:38:45,221
Get over it.
697
00:38:45,323 --> 00:38:50,160
Follow the evidence,
wherever it leads.
698
00:38:51,762 --> 00:38:55,165
If you have no evidence,
reserve judgment.
699
00:38:55,232 --> 00:38:58,218
And perhaps the most
important rule of all:
700
00:38:58,269 --> 00:39:00,036
Remember,
you could be wrong.
701
00:39:00,038 --> 00:39:02,739
Even the best scientists
702
00:39:02,773 --> 00:39:04,674
have been wrong
about some things.
703
00:39:04,742 --> 00:39:07,410
Newton, Einstein,
704
00:39:07,428 --> 00:39:10,180
and every other great scientist
in history,
705
00:39:10,214 --> 00:39:12,682
they all made mistakes.
706
00:39:12,717 --> 00:39:15,885
Of course they did--
they were human.
707
00:39:15,920 --> 00:39:20,223
Science is a way to keep
from fooling ourselves...
708
00:39:20,257 --> 00:39:23,026
and each other.
709
00:39:23,060 --> 00:39:25,395
Have scientists known sin?
710
00:39:28,566 --> 00:39:30,033
Of course.
711
00:39:30,051 --> 00:39:32,402
We have misused science,
just as we have
712
00:39:32,436 --> 00:39:35,672
every other tool
at our disposal,
713
00:39:35,706 --> 00:39:37,874
and that's why we can't afford
714
00:39:37,908 --> 00:39:41,845
to leave it in the hands
of a powerful few.
715
00:39:41,879 --> 00:39:44,781
The more science
belongs to all of us,
716
00:39:44,815 --> 00:39:47,884
the less likely
it is to be misused.
717
00:39:50,121 --> 00:39:52,756
These values
undermine the appeals
718
00:39:52,790 --> 00:39:55,058
of fanaticism and ignorance
719
00:39:55,092 --> 00:39:56,960
and, after all,
720
00:39:56,994 --> 00:39:59,429
the universe is mostly dark,
721
00:39:59,463 --> 00:40:02,699
dotted by islands of light.
722
00:40:02,733 --> 00:40:06,369
Learning the age of the Earth
or the distance to the stars
723
00:40:06,404 --> 00:40:08,371
or how life evolves--
724
00:40:08,406 --> 00:40:10,640
what difference does that make?
725
00:40:10,674 --> 00:40:13,376
Well, part of it depends
on how big a universe
726
00:40:13,411 --> 00:40:15,278
you're willing to live in.
727
00:40:15,312 --> 00:40:17,280
Some of us like it small.
728
00:40:17,314 --> 00:40:18,915
That's fine.
729
00:40:18,949 --> 00:40:20,316
Understandable.
730
00:40:20,351 --> 00:40:22,051
But I like it big.
731
00:40:22,086 --> 00:40:25,221
And when I take all of this
into my heart and my mind,
732
00:40:25,256 --> 00:40:27,157
I'm uplifted by it.
733
00:40:27,191 --> 00:40:30,960
And when I have that feeling,
I want to know that it's real,
734
00:40:30,995 --> 00:40:34,464
that it's not just something
happening inside my own head,
735
00:40:34,498 --> 00:40:36,633
because it matters what's true,
736
00:40:36,667 --> 00:40:39,102
and our imagination is nothing
737
00:40:39,136 --> 00:40:42,505
compared with
Nature's awesome reality.
738
00:40:46,644 --> 00:40:50,647
I want to know
what's in those dark places,
739
00:40:50,681 --> 00:40:54,384
and what happened
before the big bang.
740
00:40:56,454 --> 00:40:59,289
I want to know what lies
beyond the cosmic horizon,
741
00:40:59,323 --> 00:41:02,192
and how life began.
742
00:41:02,226 --> 00:41:04,694
Are there other places
in the cosmos
743
00:41:04,728 --> 00:41:08,698
where matter and energy
have become alive...
744
00:41:08,732 --> 00:41:11,167
and aware?
745
00:41:18,509 --> 00:41:20,677
I want to know my ancestors--
746
00:41:20,711 --> 00:41:22,178
all of them.
747
00:41:22,213 --> 00:41:24,447
I want to be
a good, strong link
748
00:41:24,482 --> 00:41:26,349
in the chain of generations.
749
00:41:26,383 --> 00:41:28,184
I want to protect my children
750
00:41:28,219 --> 00:41:31,354
and the children
of ages to come.
751
00:41:31,388 --> 00:41:34,557
We, who embody
the local eyes and ears
752
00:41:34,592 --> 00:41:37,293
and thoughts and feelings
of the cosmos,
753
00:41:37,328 --> 00:41:40,563
we've begun to learn the story
of our origins--
754
00:41:40,598 --> 00:41:44,467
star stuff contemplating
the evolution of matter,
755
00:41:44,502 --> 00:41:48,171
tracing that long path by which
it arrived at consciousness.
756
00:41:48,205 --> 00:41:51,174
We and the other living things
on this planet
757
00:41:51,208 --> 00:41:53,376
carry a legacy
of cosmic evolution
758
00:41:53,410 --> 00:41:55,812
spanning billions of years.
759
00:41:55,846 --> 00:41:58,047
If we take that knowledge
to heart,
760
00:41:58,082 --> 00:42:01,584
if we come to know and love
nature as it really is,
761
00:42:01,619 --> 00:42:04,654
then we will surely be
remembered by our descendants
762
00:42:04,688 --> 00:42:07,757
as good, strong links
in the chain of life.
763
00:42:07,791 --> 00:42:11,094
And our children will continue
this sacred searching,
764
00:42:11,128 --> 00:42:14,864
seeing for us as we have seen
for those who came before,
765
00:42:14,899 --> 00:42:18,167
discovering wonders
yet undreamt of...
766
00:42:18,202 --> 00:42:20,403
in the cosmos.
767
00:42:20,437 --> 00:42:22,805
¶ ¶
768
00:42:45,262 --> 00:42:47,630
¶ ¶
769
00:43:00,244 --> 00:42:47,630
Captioned by
Media Access Group at WGBH
access.wgbh.org