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Neil Armstrong:
I can see everything quite clear! Y.
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It has a stark beauty all its own.
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♪ See me when I float like a dove
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♪ skies above...
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B uzz a ld ri n: Magnificent desolation.
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- Beautiful view.
- Armstro n g: Isn't that something?
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♪ Take me away ♪
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Brian Cox: The milky way
seems a tranquil place...
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Hundreds of billions of stars
serenely spinning through the cosmos.
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But journey in wards through
the gas and dust
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that shrouds the galactic core,
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and you 'd see a curious sight...
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Stars orbiting seemingly empty space.
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Something dark and ancient lives here...
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A hole in the fabric of the universe.
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Every one of those points
of light in the night sky
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is a strange and fascinating place.
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Magnificent suns with countless planets
orbiting around them,
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alien worlds beyond imagination.
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But the strangest and most fascinating
places out there, by far,
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are dark and unseen.
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An in visible monster is lurking
in the centre of the milky way,
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A monster that drains
the colour from the universe,
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with the power to destroy worlds,
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And stop time.
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We've named the monster sagittarius a I
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and we believe it to be a black hole.
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Sagittarius a♪ has played a major role
in the evolution of our galaxy
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and may even have influenced
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the formation of stars
and planets like ours.
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But there is so much more.
Because black holes like sagittarius a ♪
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Present the most
profound intellectual challenge.
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They are part of nature,
just like you and me.
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So, we should be
able to understand them.
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But they are holes
in the fabric of the universe.
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They are gra vita tional prisons from
which even light itself can't escape.
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But in trying to understand them,
physicists have been led
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to completely reassess
our most basic understanding of reality.
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But there are answers hiding in the void
for those brave enough to seek them.
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Eileen Collins: And we copy
at go for deploy.
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You look out and this thing is so big,
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you certainly know that it's
moving over the head of the shuttle.
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Cox: In the summer of 7999,
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NASA's flagship mission
for x -ra y astronomy
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was released from the shuttle cargo bay.
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Collins: There is nothing as beautiful
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as chandra sailing off
on its way to work.
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Cox: High above
the earth, chandra scanned the sky
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hunting for some of
the hottest regions in the universe,
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exploding stars
and clusters of galaxies.
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But on September 74, 2073,
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after 74 years, chandra chanced
on something else entirely.
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The telescope gazed into
the constellation of sagittarius,
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hoping to observe
a large cloud of hot gas.
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Instead, it recorded a flash of x—ra ys,
just a few pixels across,
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coming from the apparently empty space
in the galactic core.
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Something had got very hot
for a very short period of time.
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It's thought that the flash
seen by chandra
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may have been an asteroid
tens of kilometres across,
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Ripped apart
and burning up in a fireball
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300 times brighter than the sun.
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The culprit, sagittarius a "I
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The asteroid's destruction
was our galaxy's black hole
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signalling its presence to the world.
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Twenty years ago,
we didn't know for sure
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that there is a black hole
at the centre of our galaxy.
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But by measuring bursts of radiation
and observing in detail
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the orbits of stars
close to the galactic centre,
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we now know that
sagittarius a♪ definitely exists,
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and we've been able to measure its mass.
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It is around four million times
the mass of our sun,
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which makes it
a supermassive black hole,
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one of the strangest and
most powerful objects in the universe.
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00:09:16,441 --> 00:09:20,361
And we've begun to suspect
that sagittarius a♪ isn'tjust
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some strange thing that sits
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tens of thousands of light years
from earth, at the centre of the galaxy.
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It has played a crucial role
in the evolution of the milky way,
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and the whole story began
with the death of one massive star.
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Soon after the dawn of time,
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the cosmos was home to colossal stars,
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Hundreds of times
more massive than the sun,
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stars that burnt blue in intense heat.
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But the brightest stars
are the shortest lived.
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One lived a particularly fast
and furious life,
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burning through its nuclear fuel
in just a few million years.
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And with nothing left in the tank,
gravity took over.
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The star collapsed...
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E ver smaller, e ver denser...
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Until it seemingly disappeared.
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The remnants of the star,
now smaller than an atom,
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lost from the universe.
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All that's left is a ghost,
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a black hole.
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The Genesis of sagittarius a ♪
wasn't some bizarre one-off event.
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It's possible
that almost all early stars
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became black holes when they died.
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Black holes are simply what happens
when gravity goes unchecked,
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compacting matters so densely
it tears a hole in the universe.
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In the vicinity of a black hole,
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space and time behave
in very counter-intuitive ways.
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In fact, this river provides a beautiful
and surprisingly accurate analogy.
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See, close to a black hole,
you can think of space itself
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as flowing towards the black hole.
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Now, here, the flow is not too fast.
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And so, you can imagine
I can jump into that river,
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I can swim faster
than the river of space.
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And so, I can escape
out into the galaxy.
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But as you get closer to the black hole,
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the river of space flows
faster and faster and faster.
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A collapsed star
is so small and yet so massive
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that, close to it, the gravitational
forces become overwhelming.
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There is no limit to the speed
at which the river of space can flow.
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There's a place where
the river becomes a waterfall,
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where no matter how fast I swim,
I could never escape upstream.
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And that's what happens
in the vicinity of a black hole.
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The river of space flows at, and then,
faster than the speed of light.
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Light itself can't move
fast enough to escape.
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And that's what sagittarius a♪ is.
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00:14:23,561 --> 00:14:26,801
It's a waterfall
in the fabric of the universe.
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From the moment the black hole formed
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the seed of sagittarius a ♪
had a heart of pure darkness,
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the interior forever hidden from view,
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shielded from the rest of the universe
by a boundary in space...
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The event horizon,
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the ultimate point of no return.
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As we approach the event horizon,
we get our first glimpse
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of the true weirdness of black holes.
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Einstein taught us that space and time
are not what they seem.
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They are merged together into a kind of
a fabric, the fabric of the universe.
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It's called spacetime.
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And Einstein also taught us that
the presence of massive objects,
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stars, and planets, and galaxies,
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curve and distort
the fabric of the universe,
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and that's what we feel
as the force of gravity.
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00:16:08,241 --> 00:16:13,601
But that distortion
is not only in space, it's also in time.
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As you go closer and closer
to a massive object,
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the rate that time passes slows down.
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So, if I look towards a black hole,
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I see time passing
slower and slower and slower
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until on the event horizon, time stops.
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Sagittarius a ♪ was born a waterfall
in the fabric of the universe,
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where space flows faster than light
and time grinds to a halt.
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But our black hole
was still just a baby,
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dwarfed by the stars around it.
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It was nothing like
the monster it would become.
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Sagittarius a♪ today is
four million times the mass of the sun.
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There has never been
a star that massive.
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So, it must have formed by the collapse
of something much smaller,
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and then, it must have grown
over the lifetime of the milky way
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by eating stuff.
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And fortunately, there has been
a lot of stuff around for it to eat.
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The young black hole's
inexorable gravitational pull
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meant there was no escape
for anything that strayed too close.
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Sagittarius a ♪ began to grow,
pulling on nearby stars...
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Before ripping them to shreds
and feasting on hot plasma,
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The black hole gaining more mass
and more gravitational power.
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But we don't think there were
enough stars nearby
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for the black hole to grow supermassive
on a diet of stars alone.
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Instead, it developed a taste
for more massive prey.
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When another black hole
passed close to sagittarius a'fi
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they became locked
in a gravitational embrace...
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Spiralling towards each other,
approaching half the speed of light...
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Before colliding.
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Sagittarius a ♪ cannibalised its cousin,
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creating ripples in the fabric
of the universe itself.
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More meals were to follow.
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Black holes, stars, gas clouds,
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whatever ventured
too deep into its lair.
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And as our black hole's
power and influence grew,
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its surroundings were changing, too.
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Around the galactic core, hundreds
of billions of stars were in orbit,
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slowly spinning
around their common centre of mass,
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evolving into
the familiar spiralling disk...
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The majestic milky way,
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with sagittarius a ♪at its core.
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Sagittarius a♪ became what we now call
a supermassive black hole.
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Many tens or even hundreds
of thousands of times more massive
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than any star in the universe.
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And sagittarius a♪ is not unique.
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We now think that virtually
every large galaxy
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has a supermassive black hole
at its heart.
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Chandra has looked beyond the milky way
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and observed countless
supermassive black holes,
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lurking at the hearts of the myriad
galaxies that litter the cosmos.
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These monsters aren 't
obscure quirks of nature.
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They are fundamental features of it...
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And far from being bit players.
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We 're starting to realise that
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black holes have the power and reach
to sculpt the galaxies around them.
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The centre of our young galaxy
was rich in gas and dust,
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more offerings to feast on.
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This was a gluttonous period
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that marked a new era for
the milky way's supermassive black hole
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when the in visible monster
became sculptor of the galaxy.
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Creation and destruction
often go hand in hand in the universe,
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and black holes are no exception.
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Sagittarius a♪ is certainly not only
an agent of destruction
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because the material that
falls inwards towards the black hole
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doesn't all vanish
across the event horizon.
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A lot of it goes into orbit
around the black hole.
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And that region is tremendously violent.
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There are magnetic fields
that swirl around
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and become twisted and distorted,
and they can throw material out
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00:25:12,201 --> 00:25:14,481
along the magnetic Poles
of the black hole,
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making jets that
sweep through the galaxy.
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It's only recently that we've grasped
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the true scale of
sagittarius a ♪'s eruptions.
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Man: Engine start.
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One, zero. Lift-off.
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The delta rocket carrying
a gamma ray telescope,
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searching for unseen physics
in the stars of the galaxies.
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00:26:04,841 --> 00:26:06,681
Cox: Just over a decade ago,
213
00:26:06,761 --> 00:26:10,041
a completely unexpected disco very
was made,
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00:26:10,121 --> 00:26:13,801
likened to finding
a brand new continent here on earth.
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00:26:23,921 --> 00:26:28,041
The fermi space telescope
was built to detect gamma rays,
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00:26:28,601 --> 00:26:31,561
the most energetic
radiation in the universe.
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00:26:46,241 --> 00:26:50,481
As fermi orbited the earth,
it constructed a map of the sky...
218
00:27:01,481 --> 00:27:05,481
And saw emerging
from the plane of the milky way,
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00:27:10,241 --> 00:27:17,201
two colossal bubbles of material,
each 25, 000 light years across.
220
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These bubbles are superheated gas.
221
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If our eyes were sensitive
222
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to the wavelengths of light
emitted by those bubbles,
223
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they would span half the sky
as seen from here on earth.
224
00:27:39,921 --> 00:27:43,081
And they point back
to the centre of the galaxy.
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It looks like their origin
is sagittarius a ♪.
226
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Think about that.
227
00:27:48,121 --> 00:27:52,561
I mean, sagittarius a♪ is big
but not big on a galactic scale.
228
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It would fit comfortably
inside the orbit of Mercury,
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00:27:55,361 --> 00:27:56,561
in our solar system.
230
00:28:01,281 --> 00:28:05,561
Though our black hole is only a fraction
of the size of the galaxy around it,
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00:28:07,641 --> 00:28:11,041
it had become sculptor of the milky way.
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Every few million years,
233
00:28:34,921 --> 00:28:38,401
the dense ring of material
circling our black hole
234
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Was accelerated
by twisting magnetic fields...
235
00:28:49,721 --> 00:28:53,241
Into fiery jets of superheated matter.
236
00:28:59,321 --> 00:29:01,441
Jets so powerful
237
00:29:01,521 --> 00:29:05,281
they stripped the atmospheres
from any planets in their path,
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00:29:15,081 --> 00:29:18,681
And radiation rendered
every earth-like world
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00:29:18,761 --> 00:29:22,601
within 7,000 light years uninhabitable.
240
00:29:36,561 --> 00:29:40,881
But such was the scale
of sagittarius a ♪'s outbursts
241
00:29:40,961 --> 00:29:43,921
that far, far out in the galaxy,
242
00:29:49,561 --> 00:29:50,721
Destruction...
243
00:29:52,841 --> 00:29:54,561
Turned to creation.
244
00:30:19,041 --> 00:30:22,601
If you're looking for reasons
why life not only began here on earth
245
00:30:23,161 --> 00:30:26,241
but was able to prosper
for the almost four billion years
246
00:30:26,321 --> 00:30:28,001
it took for it to evolve
247
00:30:28,081 --> 00:30:30,721
into the complex living world
that we see today,
248
00:30:30,801 --> 00:30:34,001
then, it might seem a bit of a stretch
to point to a supermassive black hole
249
00:30:34,081 --> 00:30:37,481
at the centre of our galaxy and say,
"that's one of the reasons why."
250
00:30:38,081 --> 00:30:39,841
But we're now beginning to suspect
251
00:30:39,921 --> 00:30:44,161
that those great outpourings
of energy from sagittarius a ♪
252
00:30:44,241 --> 00:30:48,521
Played a crucial role
in making this region of the galaxy,
253
00:30:48,601 --> 00:30:51,121
one in which life can flourish.
254
00:30:54,961 --> 00:30:58,841
Because the hot gas
ejected by sagittarius a ♪
255
00:30:59,961 --> 00:31:03,001
Had a calming effect on the galaxy.
256
00:31:03,081 --> 00:31:06,681
Now, you might think that a hot
gas cloud would produce more stars.
257
00:31:06,761 --> 00:31:09,161
But, in fact, the opposite is true
because hot means that
258
00:31:09,241 --> 00:31:12,521
everything's moving around very fast,
and that makes it more difficult
259
00:31:12,601 --> 00:31:17,561
for gravity to grab hold of everything
and collapse it to form stars.
260
00:31:17,641 --> 00:31:21,041
So, sagittarius a ♪
reduced the number of stars
261
00:31:21,121 --> 00:31:25,681
that formed in this region
of the galaxy, and that's a good thing.
262
00:31:25,761 --> 00:31:27,881
I mean, imagine if there was
some giant star
263
00:31:27,961 --> 00:31:32,401
that had formed close by
that exploded in a supernova explosion.
264
00:31:32,481 --> 00:31:35,441
That would not be a good thing
if you're an amoeba
265
00:31:35,521 --> 00:31:39,121
and you have designs, one day,
on evolving into Einstein.
266
00:31:39,841 --> 00:31:43,641
So, sagittarius a♪ turned
what is potentially
267
00:31:43,721 --> 00:31:47,561
a violent region of our galaxy
into a peaceful one.
268
00:31:55,241 --> 00:31:59,121
The warm gases
pushed out by sagittarius a ♪
269
00:31:59,201 --> 00:32:01,761
Slowed the rate of star formation.
270
00:32:08,561 --> 00:32:13,481
And around one small yellow star
in a quiet region
271
00:32:13,561 --> 00:32:17,441
at the unfashionable end
of the outer spiral arms of the galaxy,
272
00:32:29,881 --> 00:32:34,761
Four billion years of stability
made all the difference.
273
00:32:56,481 --> 00:32:58,721
Now, of course,
there are many things that are necessary
274
00:32:58,801 --> 00:33:00,561
for life to exist on a planet.
275
00:33:01,361 --> 00:33:06,481
The list is unimaginably vast,
but I think it is interesting
276
00:33:06,561 --> 00:33:11,921
that on that list, there is the presence
of this strange object,
277
00:33:12,001 --> 00:33:14,561
a black hole, sagittarius a♪,
278
00:33:14,641 --> 00:33:18,921
tens of thousands of light years away
at the centre of our galaxy.
279
00:33:43,561 --> 00:33:48,921
Having cleared out much of the gas,
dust and stars that once lay close by,
280
00:33:51,841 --> 00:33:53,721
there was little left to feast on.
281
00:33:57,081 --> 00:33:59,801
Our black hole fell silent.
282
00:34:04,761 --> 00:34:07,761
The enormous bubbles spotted by fermi...
283
00:34:09,281 --> 00:34:12,201
Echoes of a glorious past.
284
00:34:19,321 --> 00:34:24,001
Today, sagittarius a ♪
is a sleeping giant,
285
00:34:25,561 --> 00:34:30,441
a brooding beast
operating on a slow simmer.
286
00:34:44,361 --> 00:34:48,401
Sagittarius a♪'s journey
from violent destroyer
287
00:34:48,481 --> 00:34:50,681
to sculptor of the galaxy
288
00:34:50,761 --> 00:34:52,801
to the sleeping giant that we see today
289
00:34:52,881 --> 00:34:57,441
has been pieced together over
the last 20 years by observational data
290
00:34:57,521 --> 00:35:00,601
from telescopes such as
chandra and fermi.
291
00:35:02,561 --> 00:35:04,841
But there's
a very big difference indeed,
292
00:35:04,921 --> 00:35:06,401
between knowing how a black hole
293
00:35:06,481 --> 00:35:09,881
interacts with its environment,
how it sculpts a galaxy
294
00:35:10,681 --> 00:35:14,241
and what it actually is at a deep level.
295
00:35:17,681 --> 00:35:20,361
What is it really like inside?
296
00:35:55,721 --> 00:35:59,641
Cox: It's by looking into the future
that we 're beginning to explore
297
00:35:59,721 --> 00:36:02,321
the deep mystery of black holes.
298
00:36:07,681 --> 00:36:11,041
Dozens of stars
orbit around sagittarius a I
299
00:36:12,681 --> 00:36:18,161
some passing just a few
billion miles from the event horizon,
300
00:36:18,241 --> 00:36:21,481
a hair's breadth on galactic scales.
301
00:36:23,841 --> 00:36:26,921
These fl ybys
could have fatal consequences.
302
00:36:40,961 --> 00:36:44,961
Some of these stars
will likely have planets in orbit,
303
00:36:45,041 --> 00:36:48,801
planets that may stray
too close to the beast,
304
00:36:57,881 --> 00:37:04,641
A math to a flame, pulled from
its parent star towards the abyss.
305
00:37:18,041 --> 00:37:20,801
If the planet survives
its journey inwards,
306
00:37:23,601 --> 00:37:28,361
and we could stand on its surface
and look out into the universe beyond,
307
00:37:38,881 --> 00:37:44,041
We would see space and time
becoming increasingly distorted.
308
00:38:07,281 --> 00:38:11,681
But eventually, tidal
gravitational forces become too strong.
309
00:38:33,921 --> 00:38:37,681
Inexorabl y, the singularity awaits,
310
00:38:39,281 --> 00:38:44,281
the end of time
where all paths terminate.
311
00:39:12,401 --> 00:39:18,081
Over trillions of years,
all the stars around sagittarius a ♪
312
00:39:18,161 --> 00:39:21,001
Will gradually fade and die.
313
00:39:26,681 --> 00:39:31,801
On more and more alien worlds,
the dawn will fail to come.
314
00:39:41,721 --> 00:39:45,321
But our supermassive monster will go on,
315
00:39:46,641 --> 00:39:49,041
its secrets sealed away inside...
316
00:39:50,481 --> 00:39:52,921
Seemingly forever.
317
00:39:59,681 --> 00:40:02,241
We predict that, one day,
318
00:40:02,321 --> 00:40:06,481
black holes will be
all that remains in the universe.
319
00:40:07,001 --> 00:40:09,081
The final dark age.
320
00:40:30,281 --> 00:40:33,361
If nothing can ever escape
from black holes,
321
00:40:33,441 --> 00:40:37,401
if sagittarius a ♪
really is an eternal prison,
322
00:40:37,481 --> 00:40:40,641
then, this is the end
of the story of the universe,
323
00:40:40,721 --> 00:40:44,241
darkness littered
with holes in spacetime.
324
00:40:44,841 --> 00:40:47,441
But we don't think
this is the end of the story.
325
00:40:52,481 --> 00:40:57,201
We now believe
that even black holes die.
326
00:41:04,321 --> 00:41:07,641
And their deaths come
at the hands of what might seem
327
00:41:07,721 --> 00:41:12,961
an inconsequential detail
discovered almost five decades ago.
328
00:41:16,801 --> 00:41:22,161
In 1975, Stephen Hawking published
a remarkable paper in which he showed
329
00:41:22,281 --> 00:41:25,201
that black holes
are not completely black.
330
00:41:25,281 --> 00:41:28,441
They glow faintly.
They have a temperature.
331
00:41:28,521 --> 00:41:33,201
And here's his beautiful equation
for the temperature of a black hole.
332
00:41:37,961 --> 00:41:41,601
And you can see that there's
something deep going on...
333
00:41:42,481 --> 00:41:46,281
Because this has got
all of physics in it.
334
00:41:46,681 --> 00:41:49,201
This thing here,
"h-bar", is planck's constant,
335
00:41:49,281 --> 00:41:52,201
that's to do with quantum mechanics,
the subatomic world.
336
00:41:52,281 --> 00:41:56,201
5 the speed of light.
"G" is the strength of gravity.
337
00:41:56,281 --> 00:41:58,801
This "kb" here is boltzmann's constant,
338
00:41:58,881 --> 00:42:02,561
that's to do with
temperature and thermodynamics.
339
00:42:02,641 --> 00:42:05,161
And this "m" here is the mass
of the black hole.
340
00:42:05,241 --> 00:42:07,921
It's even got circles
because it's got a pi in it.
341
00:42:09,121 --> 00:42:13,961
Ha wking's conclusion
proved to be irrefutable
342
00:42:14,041 --> 00:42:17,361
and the implications are huge.
343
00:42:17,961 --> 00:42:21,201
If something has a temperature,
then it radiates.
344
00:42:21,281 --> 00:42:23,641
That's why if you put your hand
near something that's hot,
345
00:42:23,721 --> 00:42:25,041
you can feel it.
346
00:42:25,121 --> 00:42:26,721
And so, over timescales that are
347
00:42:26,801 --> 00:42:29,601
billions and billions
and billions and billions of times
348
00:42:29,681 --> 00:42:32,521
longer than the current age
of the universe,
349
00:42:32,601 --> 00:42:37,401
sagittarius a ♪
will eventually evaporate away.
350
00:42:57,921 --> 00:43:04,601
Very gradually, Hawking radiation
will erode sagittarius a "I.
351
00:43:08,201 --> 00:43:11,121
Smaller and smaller...
352
00:43:16,121 --> 00:43:20,041
Until many trillions and trillions
of years into the future...
353
00:43:26,201 --> 00:43:28,001
In a final burst of light,
354
00:43:30,601 --> 00:43:33,441
our black hole will die.
355
00:43:34,841 --> 00:43:37,681
And then, there will be darkness...
356
00:43:39,121 --> 00:43:41,121
For all eternity.
357
00:43:48,121 --> 00:43:51,561
Now, you may say quite legitimately,
"well, why do we care?
358
00:43:51,641 --> 00:43:54,881
"Why does it matter if black holes
evaporate away sometime
359
00:43:54,961 --> 00:43:59,281
"in the far, far future of the universe?
There'll be nobody around to see it."
360
00:44:00,001 --> 00:44:04,801
But the discovery that black holes
evaporate raises what I think
361
00:44:04,881 --> 00:44:08,281
is the most profound question
in the history of physics,
362
00:44:08,361 --> 00:44:11,761
certainly over the last 100 years,
and that's no exaggeration.
363
00:44:12,321 --> 00:44:17,601
See, what happens if I set fire
to this piece of paper...
364
00:44:19,281 --> 00:44:21,321
With Stephen Hawking's
equation written on it?
365
00:44:21,401 --> 00:44:27,201
I cause it to evaporate away.
Do I destroy everything?
366
00:44:27,281 --> 00:44:29,961
Do I remove every piece of information,
367
00:44:30,041 --> 00:44:33,761
including the equation,
from the universe when it burns away?
368
00:44:54,081 --> 00:44:56,001
Well, the answer is, no.
369
00:44:56,081 --> 00:45:01,561
If I could collect every ash,
every molecule of gas
370
00:45:01,641 --> 00:45:03,921
that burns off into the atmosphere,
371
00:45:04,001 --> 00:45:08,081
then, in principle, I could
reconstruct the piece of paper,
372
00:45:08,161 --> 00:45:10,441
and everything it contains,
373
00:45:10,521 --> 00:45:13,681
every piece of information
on this piece of paper
374
00:45:14,161 --> 00:45:16,721
including Stephen Hawking's equation.
375
00:45:18,841 --> 00:45:24,641
But can that be true for black holes,
the ultimate gravitational prisons,
376
00:45:24,721 --> 00:45:30,321
these objects in the sky from which
even light itself can't escape?
377
00:45:31,121 --> 00:45:35,441
When they evaporate away,
do they return the information
378
00:45:35,521 --> 00:45:39,401
about everything that ever fell in
back to the universe?
379
00:46:27,121 --> 00:46:33,481
If information somehow escapes from
sagittarius a ♪ as it evaporates away,
380
00:46:35,281 --> 00:46:37,921
the implication is profound.
381
00:46:40,881 --> 00:46:43,241
Black holes aren't tombs.
382
00:46:44,121 --> 00:46:45,321
They're gateways.
383
00:46:48,881 --> 00:46:55,281
We now believe that anything that falls
into sagittarius a ♪ will live on,
384
00:46:59,521 --> 00:47:03,561
not as a physical object
but as information...
385
00:47:09,521 --> 00:47:11,961
Escaping from the heart of darkness,
386
00:47:13,361 --> 00:47:17,601
encoded in the Hawking radiation
in the far future.
387
00:47:28,401 --> 00:47:32,241
The memory of all those worlds
that fell into sagittarius a♪,
388
00:47:32,321 --> 00:47:35,441
of the entire history
of the milky way galaxy,
389
00:47:35,521 --> 00:47:39,481
is somehow written in the ashes
of the universe in the far future.
390
00:47:43,041 --> 00:47:45,801
But the real treasure lies
in the explanation
391
00:47:45,881 --> 00:47:50,001
of how the information gets out
from those eternal prisons.
392
00:47:50,361 --> 00:47:53,401
Now, what I'm going to tell you
is going to sound absolutely bizarre.
393
00:47:53,481 --> 00:47:55,521
It's going to sound
like science fiction.
394
00:47:56,161 --> 00:47:57,601
But here goes.
395
00:47:57,681 --> 00:48:02,561
When the black hole is evaporated away,
about half of it is gone.
396
00:48:03,241 --> 00:48:07,721
The interior becomes, in some sense,
the same place
397
00:48:07,801 --> 00:48:12,041
as the distant Hawking radiation
that was emitted aeons ago
398
00:48:12,121 --> 00:48:14,881
that's out there
in the far reaches of the universe.
399
00:48:15,401 --> 00:48:19,401
It seems that
spacetime wormholes open up
400
00:48:19,481 --> 00:48:24,321
between the interior of the black hole
and those distant parts of the universe.
401
00:48:24,401 --> 00:48:29,281
And it's that that allows us
to read the information inside.
402
00:48:29,361 --> 00:48:32,761
Now, that
is supposed to sound weird,
403
00:48:32,841 --> 00:48:36,001
and I should say that
nobody really agrees
404
00:48:36,081 --> 00:48:38,641
on the physical picture
of what's happening.
405
00:48:38,721 --> 00:48:42,001
But what everybody agrees on is this.
406
00:48:42,081 --> 00:48:43,841
The black holes are telling us
407
00:48:43,921 --> 00:48:49,601
that our intuitive picture of reality,
of space and time is wrong.
408
00:48:49,681 --> 00:48:54,001
The idea that
this place is close to this place,
409
00:48:54,081 --> 00:48:57,121
and that time ticks along is wrong.
410
00:48:57,201 --> 00:49:03,841
There is a deeper picture of reality
in which space and time do not exist.
411
00:49:13,161 --> 00:49:16,281
Our attempt to answer
a seemingly simple question
412
00:49:17,761 --> 00:49:21,241
about the fate of objects
that fall into black holes
413
00:49:21,321 --> 00:49:26,401
has led us to a profound,
and quite unsettling conclusion.
414
00:49:29,041 --> 00:49:35,001
Space and time, concepts so foundational
to how we experience the world
415
00:49:35,961 --> 00:49:39,561
are not fundamental
properties of nature.
416
00:49:42,881 --> 00:49:49,721
They emerge from a deeper reality
in which neither exist.
417
00:49:53,881 --> 00:50:00,601
The thing about black holes
is that nobody really understands them.
418
00:50:00,681 --> 00:50:05,281
So, don't worry if you don't understand
what I'm talking about
419
00:50:05,361 --> 00:50:07,561
because I don't understand
what I'm talking about,
420
00:50:07,641 --> 00:50:09,241
and nobody else does either.
421
00:50:20,521 --> 00:50:22,281
We 're still a long way
422
00:50:22,361 --> 00:50:26,481
from fully comprehending
the secrets of black holes.
423
00:50:30,001 --> 00:50:32,081
But we are beginning to lift the veil.
424
00:50:38,441 --> 00:50:41,521
Far from being a mere cosmic aberration,
425
00:50:44,201 --> 00:50:48,641
sagittarius a ♪ is a part of our history
426
00:50:48,721 --> 00:50:51,481
and of our future.
427
00:50:53,121 --> 00:50:56,721
Our black hole
not only made us who we are today,
428
00:50:58,521 --> 00:51:00,201
it's our teacher,
429
00:51:01,521 --> 00:51:05,481
slowly revealing
the deepest mysteries of the universe,
430
00:51:07,481 --> 00:51:10,521
secrets sealed away for so long
431
00:51:12,961 --> 00:51:16,081
inside a place beyond forever.
432
00:51:21,761 --> 00:51:24,761
The moral of the story is this.
433
00:51:24,841 --> 00:51:27,361
Understanding the book
of nature is hard.
434
00:51:27,921 --> 00:51:29,561
And so, the more of nature we observe,
435
00:51:29,641 --> 00:51:32,441
the more chance we have
of finishing the book.
436
00:51:32,881 --> 00:51:38,161
Now, the strangest objects in nature,
by far, are black holes.
437
00:51:38,241 --> 00:51:39,801
And so, I suppose, it's not surprising
438
00:51:39,881 --> 00:51:43,041
that by peering over the horizon
and into the darkness,
439
00:51:43,121 --> 00:51:46,081
we have caught a glimpse
of something deeply hidden,
440
00:51:46,681 --> 00:51:50,681
the underlying structure
of reality itself.
441
00:51:53,521 --> 00:51:55,881
So, if we want to understand
the meaning of it all,
442
00:51:55,961 --> 00:51:58,161
we can't restrict ourselves
443
00:51:58,241 --> 00:52:01,201
to the intellectually safe confines
of our planet.
444
00:52:01,801 --> 00:52:05,681
We have to look out there,
to the universe beyond.
445
00:52:53,241 --> 00:52:57,201
Grant tremblay: So, of the seemingly
endless zoo of objects in our universe,
446
00:52:57,321 --> 00:53:01,161
from clouds of gas, to planets,
to stars, galaxies, what have you,
447
00:53:01,241 --> 00:53:05,401
black holes are probably
one of the most fundamentally important
448
00:53:05,481 --> 00:53:08,721
singular class of objects
that we can study,
449
00:53:09,441 --> 00:53:12,081
a place where the laws of physics
literally break do wn.
450
00:53:12,601 --> 00:53:16,241
We have theories, but we can't
really know what's happening.
451
00:53:16,881 --> 00:53:19,801
David kaiser: So, black holes
present this remarkable invitation
452
00:53:19,881 --> 00:53:22,161
to physicists,
mathematicians, astronomers.
453
00:53:22,241 --> 00:53:24,401
One of the best tools we have to study
454
00:53:24,481 --> 00:53:27,321
these exotic phenomena
is the chandra telescope.
455
00:53:32,801 --> 00:53:34,761
Chandra's kind of like
a black hole hunter,
456
00:53:34,841 --> 00:53:38,521
finding them near and far
throughout the galaxy and the universe.
457
00:53:38,601 --> 00:53:40,041
Woman: Just a few minutes away
458
00:53:40,121 --> 00:53:42,281
from the 26th flight
of the shuttle, Columbia,
459
00:53:42,361 --> 00:53:43,601
with a crew of five.
460
00:53:50,481 --> 00:53:53,601
Kimberly arcan d: I think a night launch
is particularly exciting.
461
00:53:54,241 --> 00:53:56,401
Woman: We have a go
for engine start.
462
00:53:57,361 --> 00:54:00,841
We have booster ignition,
lift-off of co lu m bia.
463
00:54:05,161 --> 00:54:07,041
Arcan d: You just see fire.
464
00:54:07,121 --> 00:54:10,161
It lights up the night sky
in the most beautiful way.
465
00:54:10,681 --> 00:54:13,801
Man: Colu m bia now has burned
more than two million pounds of fuel
466
00:54:13,881 --> 00:54:15,761
and weighs half
of what it did at launch.
467
00:54:15,841 --> 00:54:18,841
Its huge. Chandra is about
the size of a school bus.
468
00:54:18,921 --> 00:54:23,281
It's the largest telescope to ever
be launched by the space shuttle.
469
00:54:29,361 --> 00:54:31,161
Man: Srb separation is confirmed.
470
00:54:31,961 --> 00:54:35,041
You're stressed about the astronauts
on board that are literally
471
00:54:35,121 --> 00:54:39,401
risking their lives to help us
get a better view of the universe.
472
00:54:42,641 --> 00:54:45,161
When the main engine's
cut off we 're in zero-g.
473
00:54:45,241 --> 00:54:48,001
We separate the tank
and we 're orbiting the earth.
474
00:54:50,001 --> 00:54:51,281
And when we 're sure
475
00:54:51,361 --> 00:54:52,901
that everyone is ready
at mission control,
476
00:54:52,921 --> 00:54:55,321
then, I go ahead and pull the switch
marked ”deploy”.
477
00:54:55,761 --> 00:54:58,881
And you're looking at the deploy
of the chandra x—ra y observatory.
478
00:55:00,201 --> 00:55:04,041
Chandra is an X-ray telescope,
which means that it can see
479
00:55:04,121 --> 00:55:07,121
the most energetic light
coming at us from the universe.
480
00:55:07,841 --> 00:55:11,401
The telescope has to be
outside the earth's atmosphere
481
00:55:11,481 --> 00:55:15,361
because the earth's atmosphere,
thankfully for us, blocks out x-rays.
482
00:55:15,441 --> 00:55:17,001
Otherwise, we'd just get fried.
483
00:55:19,561 --> 00:55:20,921
Kaiser: The chandra satellite,
484
00:55:21,001 --> 00:55:24,041
by rising above the atmosphere,
has a much clearer view.
485
00:55:25,041 --> 00:55:27,881
Why is that so interesting
for studying things like black holes?
486
00:55:27,961 --> 00:55:32,281
Black holes can excite matter
in their vicinity to very high energies.
487
00:55:32,361 --> 00:55:35,801
They can get atoms and parts
of atoms whipping around,
488
00:55:35,881 --> 00:55:40,001
and by re wing up those particles
to very, very high energies,
489
00:55:40,081 --> 00:55:41,601
they will radiate.
490
00:55:42,281 --> 00:55:45,241
So, we can gather
enormous amounts of information
491
00:55:45,321 --> 00:55:48,201
about the immediate vicinity
of a black hole.
492
00:55:52,041 --> 00:55:56,361
When we look at sagittarius a♪ today,
it's quiet and not doing very much.
493
00:55:56,441 --> 00:55:59,081
But when we look at other supermassive
black holes in the universe,
494
00:55:59,121 --> 00:56:00,161
they're active.
495
00:56:02,881 --> 00:56:04,761
Arcan d: So, you can
take chandra and watch
496
00:56:04,841 --> 00:56:08,641
a black hole have a small snack,
maybe like a human might have
497
00:56:08,721 --> 00:56:12,201
a little biscuit in the afternoon.
And it's something like an asteroid,
498
00:56:12,281 --> 00:56:15,961
and there will be a small sort of
X-ray signature from that event.
499
00:56:16,441 --> 00:56:21,121
But you can also see a black hole
have a really, really big snack
500
00:56:21,201 --> 00:56:23,321
and chandra's able
to witness that as well.
501
00:56:24,801 --> 00:56:26,201
Tremblay: Chandra has witnessed
502
00:56:26,281 --> 00:56:29,441
the destruction of a star
by a black hole itself right?
503
00:56:29,521 --> 00:56:33,201
So, this poor star wanders in
to the black hole,
504
00:56:34,681 --> 00:56:38,001
then, it rips the star apart,
it shears it, right?
505
00:56:38,081 --> 00:56:40,921
And then, the corpse of that star,
506
00:56:41,001 --> 00:56:42,881
this sort of spaghetti-fied matter
507
00:56:42,961 --> 00:56:45,601
that starts spiralling
around the event horizon,
508
00:56:45,681 --> 00:56:47,001
lights up in x-rays.
509
00:56:49,161 --> 00:56:53,801
So, to be witness to that,
to observe the destruction of a star,
510
00:56:53,881 --> 00:56:59,241
you know, in time, it was just
extraordinary. It's just unbelievable.
511
00:57:02,001 --> 00:57:05,161
Arcan d: There's this one
pretty famous image that chandra took
512
00:57:05,241 --> 00:57:10,321
called the chandra deep field-south,
and it's the deepest x—ra y image ever.
513
00:57:10,401 --> 00:57:14,161
In that one dataset,
there's thousands of black holes,
514
00:57:14,241 --> 00:57:17,001
like, maybe 5, 000 of them, if not more.
515
00:57:17,081 --> 00:57:21,961
And it just kind of helps show you
that they're all over the place
516
00:57:22,041 --> 00:57:24,241
and there's so much more to discover.
43383
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