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In the beginning,
there was darkness...
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and then, bang...
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giving birth to an endless
expanding existence...
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00:00:09,384 --> 00:00:11,927
of time, space, and matter.
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Now, see further
than we've ever imagined...
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beyond the limits of our existence...
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in a place we call "The Universe. "
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Cosmic collisions...
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they are among the most violent...
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and life-altering phenomena
in the universe.
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From fender-benders
to high-velocity impacts...
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00:00:38,329 --> 00:00:41,707
gravity is constantly moving
everything around in space...
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00:00:43,543 --> 00:00:45,878
and so things
are bound to collide.
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Asteroids, comets,
galaxies, and planets...
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00:00:52,260 --> 00:00:55,596
are some of the objects
involved in these energized events.
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Yet as violent and destructive
as these collisions sound...
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we may owe
our very existence to them.
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Darin Ragozzine
is on the hunt for answers...
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to an ancient collision
that happened far off in space.
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Ragozzine has zeroed in
on a vibrant gray rock.
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It's the vestige
of an ancient fiery impact...
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involving two massive objects...
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the largest being
the size of Pluto.
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This gargantuan rock,
called 2003 EL61...
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is a member
of a collisional family...
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that orbits just beyond
the planet Neptune.
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Collisional families
are groups of objects...
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that have very similar shapes,
sizes, and tilts...
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as they go around the Sun.
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00:02:03,873 --> 00:02:06,792
They stayed in
a tight cluster of orbits...
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because they came
from the same objects.
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Objects that came
from the same parent...
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should be made out
of the same material.
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00:02:15,260 --> 00:02:19,471
So, by studying the compositions
and verifying that they're similar...
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we can know that they came
from the same origin.
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Billions of years ago, 2003 EL61
and its family members...
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were part of one gigantic body
over a thousand miles across.
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The mammoth object resided
in the Kuiper Belt...
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a repository for objects
that didn't become planets...
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00:02:42,537 --> 00:02:44,329
in the outer solar system.
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But at that time...
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the Kuiper Belt was buzzing
with loose objects.
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The ice-covered rock...
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eventually slammed
into another object half its size...
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at a speed estimated
at 3,000 miles per hour.
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The impact produced energy equivalent
to ten billion atomic bombs.
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It also ejected large chunks
of ice from the object...
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each one ranging
from 250 miles in diameter...
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down to mere specks.
50
00:03:21,618 --> 00:03:25,537
The fragmented pieces are now
all members of a collisional family...
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with 2003 EL61
being the largest piece.
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We're here at a clay pigeon
shooting range...
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because the trajectory of the shards
after a clay pigeon is hit...
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is very similar to the orbits
that family members take.
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00:03:44,724 --> 00:03:47,684
Once it's hit,
the pieces fly out...
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but they pretty much follow that
same trajectory as they go down.
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In the case of 2003 EL61...
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the impact has been sending it
rapidly spinning...
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like an amusement ride,
rotating once every four hours.
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It got hit sideways,
and so it was spinning.
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00:04:09,832 --> 00:04:14,544
And because it's spinning so fast,
it elongates itself...
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pulls itself out, and
it's shaped sort of like a football...
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except it's more like a football
where you let out some of the air...
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and squash it on one end.
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00:04:22,887 --> 00:04:29,268
So 2003 EL61 is the fastest-spinning
large object that we know...
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anywhere in the solar system.
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There's nothing else
quite like this.
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Planetary astronomer Mike Brown...
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has conducted
extensive surveying of 2003 EL61...
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the biggest and brightest
known object in the Kuiper Belt.
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It's bright, it's big,
but it's also very shiny...
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because we think
when the collision happened...
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most of that ice got removed
and the things around it.
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And it just left
a little, thin layer...
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of almost pure ice
sitting on top of this rock.
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And that's why
it's so much shinier...
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than everything else
we see up there.
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It's that pure ice
that's out there.
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I think that 2003 EL61 is
the largest object out there...
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that had a collision
that formed a family.
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I really do think it's one
of the largest collisions...
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that occurred in the outer part
of the solar system...
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in the history
of the solar system.
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The impact
not only created 2003 EL61...
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and its galactic family,
it also produced two moons.
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We're searching for them now...
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and something like ten percent
of Kuiper Belt objects have moons.
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But all of these objects
that we've looked at...
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only a few have
more than one moon.
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Infrared telescopes determine
the size of these objects...
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by measuring the heat they emit.
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Although 2003 EL61
is a hundred times larger...
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than its next biggest
family member...
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this fragmented group
maintains similar orbits.
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The pieces stay together
and keep following each other...
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in their orbits around the Sun.
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So astronomers can identify collisional
families...
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by looking for common
orbital characteristics.
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So, the distance from the Sun,
how elliptical the orbit is.
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When you shoot a shotgun,
the pellets go out...
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into similar trajectories
as the original object.
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This is the same
as in collisional families...
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in the solar system...
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which follow similar orbits
after the collision...
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as the original object was under.
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And this is how
we're able to identify them.
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So after this collision happens,
they are on slightly different orbits.
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And like runners on a track,
if they all stayed in their own lanes...
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if they all ran
about the same speed...
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because the lanes have
slightly different lengths...
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after a while,
if you looked at the track...
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each runner would be
at a different place along the track.
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And this is the same
for family members right now.
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So even though they're not
next to each other today...
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when we look at them,
we can still identify each
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00:07:06,801 --> 00:07:08,802
in terms of the way
their orbits are...
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the way they go
around the Sun.
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00:07:13,015 --> 00:07:16,977
Scientists wonder
whether 2003 EL61...
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00:07:17,019 --> 00:07:19,896
could eventually be involved
in another collision.
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00:07:19,939 --> 00:07:23,525
It seems as though Neptune
is gravitationally tugging on it...
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which will eventually
change its orbit.
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In a hundred million years...
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it's going to just barely
cross the orbit of Neptune.
124
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At that point, it's hard to guess
what's going to happen.
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Neptune can either throw it
into the inner solar system...
126
00:07:35,580 --> 00:07:36,705
or it can try to toss it out...
127
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or many different things
can happen.
128
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Objects are periodically
bumped out of the Kuiper Belt...
129
00:07:45,173 --> 00:07:48,550
and drift in the direction
of the inner solar system.
130
00:07:49,177 --> 00:07:51,553
These icy rocks become comets...
131
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as they form long tails
of ice and dust...
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when moving towards our Sun.
133
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Eventually, it will work its way
perhaps to Jupiter.
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At that point, Jupiter actually
throws it out of the solar system.
135
00:08:03,524 --> 00:08:05,150
No one has really thought
about what would happen...
136
00:08:05,193 --> 00:08:08,695
if something the size
of 2003 EL61 hit Jupiter.
137
00:08:11,199 --> 00:08:14,868
But smaller comets have been
known to strike the gas giant.
138
00:08:16,287 --> 00:08:20,040
In July 1994,
the Hubble Space Telescope...
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00:08:20,082 --> 00:08:22,751
observed an astonishing event.
140
00:08:22,793 --> 00:08:26,838
A string of comet fragments,
called Shoemaker-Levy 9...
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00:08:26,881 --> 00:08:31,676
crashed into Jupiter at the speed
of 130,000 miles per hour.
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00:08:31,719 --> 00:08:34,012
The largest cometary piece...
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released six million megatons
of explosive energy.
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They impacted Jupiter about
twenty times every seven hours...
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until they were destroyed.
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The points of impact left scars
on the surface of Jupiter...
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reminders
of the violent event.
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00:08:55,576 --> 00:08:58,411
JPL senior scientist
Don Yeomans...
149
00:08:58,454 --> 00:09:01,164
has analyzed
the Shoemaker-Levy 9 event.
150
00:09:03,209 --> 00:09:05,043
The Shoemaker-Levy 9 impacts...
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00:09:05,086 --> 00:09:08,046
was an eye-opener for the public
and the scientific community...
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in the sense
that these cosmic collisions...
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do happen from time to time...
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and the energy that they
could generate are just enormous.
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It's a good thing this thing
hit Jupiter and not the Earth...
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00:09:17,306 --> 00:09:20,308
'cause there would've been
a serious problem on Earth.
157
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Had the Shoemaker-Levy 9
struck Earth...
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00:09:26,023 --> 00:09:29,442
it would have made
devastating impact craters...
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the largest
about forty miles wide.
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00:09:33,531 --> 00:09:37,867
Any one of them could have
destroyed a metropolitan city...
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and churned up enough dust
to block sunlight for months.
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00:09:43,082 --> 00:09:45,250
Jupiter, being in
the outer solar system...
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and being far more massive than
any of the other planets combined...
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takes a lot of hits that might have
otherwise been destined for Earth.
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00:09:52,300 --> 00:09:55,302
So big brother Jupiter
is out there watching us.
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00:10:00,725 --> 00:10:03,602
Jupiter acts
like a planetary goalkeeper...
167
00:10:03,644 --> 00:10:07,355
but will it be able
to deflect 2003 EL61...
168
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if it breaks loose
from the Kuiper Belt...
169
00:10:09,191 --> 00:10:10,567
and tumbles toward Earth?
170
00:10:12,862 --> 00:10:14,904
It's also possible
that it could hit Jupiter...
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00:10:14,947 --> 00:10:16,448
like Shoemaker-Levy 9 did.
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00:10:16,490 --> 00:10:19,951
This object is
about 2,000 times bigger...
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00:10:19,994 --> 00:10:22,704
than the thing that hit Jupiter,
than Shoemaker-Levy 9.
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00:10:22,747 --> 00:10:26,666
So it would be an incredible
explosion in the night sky.
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It would be the single most prominent
thing that you could see.
176
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It would be bigger
than the full Moon...
177
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at least the tail of it.
178
00:10:33,716 --> 00:10:37,135
Because collisional families
are difficult to locate...
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researchers are eager to study
2003 EL61 and its relatives.
180
00:10:43,726 --> 00:10:47,395
Less is known about
collisional families in the Kuiper Belt...
181
00:10:47,438 --> 00:10:50,774
simply because fewer
Kuiper Belt members are known...
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00:10:50,816 --> 00:10:52,567
than we know about asteroids.
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00:10:52,610 --> 00:10:56,321
So less research has been done
to try to find collisional families...
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00:10:56,364 --> 00:10:57,739
within the Kuiper Belt.
185
00:10:58,574 --> 00:11:03,620
As of today, we know of only this one
collisional family in the Kuiper Belt.
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00:11:03,663 --> 00:11:07,457
They're very hard to find
and to recognize.
187
00:11:07,500 --> 00:11:11,961
And we got extremely lucky
with 2003 EL61 and its family.
188
00:11:12,004 --> 00:11:13,421
We're working right now...
189
00:11:13,464 --> 00:11:15,382
trying to figure out other ways
that we might be able to find...
190
00:11:15,424 --> 00:11:17,509
these additional families,
'cause they must be there...
191
00:11:17,551 --> 00:11:19,260
but we just don't know
how to find them yet.
192
00:11:22,973 --> 00:11:24,766
Like these clay pigeon pieces...
193
00:11:24,809 --> 00:11:27,644
family members
from the 2003 EL61 family...
194
00:11:27,687 --> 00:11:29,354
all remain
in similar orbits today.
195
00:11:29,397 --> 00:11:31,189
We're able
to follow them today...
196
00:11:31,232 --> 00:11:32,357
and to learn more
about the history...
197
00:11:32,400 --> 00:11:34,401
of the Kuiper Belt
and of collisions.
198
00:11:38,447 --> 00:11:40,115
One enduring mystery...
199
00:11:40,157 --> 00:11:44,953
is when the 2003 EL61 collision
actually occurred.
200
00:11:46,664 --> 00:11:49,499
We think we can look at where
the different objects are now...
201
00:11:49,542 --> 00:11:52,669
and try to essentially
run time backwards...
202
00:11:52,712 --> 00:11:55,296
and figure out when they were
in this one big collision.
203
00:11:55,339 --> 00:11:58,341
Our best guess is that that answer
is going to be essentially...
204
00:11:58,384 --> 00:12:00,135
at the very beginning
of the solar system.
205
00:12:01,804 --> 00:12:06,224
2003 EL61 and its family
were probably created...
206
00:12:06,267 --> 00:12:08,226
during one
of the most turbulent periods...
207
00:12:08,269 --> 00:12:10,603
in the history
of our solar system...
208
00:12:10,646 --> 00:12:15,108
when collisions were as common
as stars in the night sky.
209
00:12:22,450 --> 00:12:27,579
From the beginning, collisions
have been a fact of life in space.
210
00:12:27,621 --> 00:12:31,916
They created much of our universe,
and at the same time...
211
00:12:31,959 --> 00:12:34,294
destroyed some of it
along the way.
212
00:12:35,796 --> 00:12:37,672
Collisions are the way
that you build planets.
213
00:12:37,715 --> 00:12:39,924
Without collisions, you don't
have planets to begin with.
214
00:12:39,967 --> 00:12:41,551
You start out
with very small particles...
215
00:12:41,594 --> 00:12:43,094
each one of them
collides together...
216
00:12:43,137 --> 00:12:44,429
bigger and bigger
and bigger and bigger...
217
00:12:44,472 --> 00:12:47,348
until you slowly build up
these planets.
218
00:12:49,059 --> 00:12:52,145
At the same time,
collisions can destroy planets.
219
00:12:53,189 --> 00:12:55,231
The planets in our solar system...
220
00:12:55,274 --> 00:12:58,818
were created during a period
called the heavy bombardment...
221
00:12:58,861 --> 00:13:02,322
that happened over
4.5 billion years ago.
222
00:13:05,451 --> 00:13:08,661
And the collisions didn't stop
with the heavy bombardment.
223
00:13:10,831 --> 00:13:13,374
Over 600 million years later...
224
00:13:13,417 --> 00:13:17,128
our solar system experienced
another spike in collisions...
225
00:13:17,171 --> 00:13:21,007
during a period called
the late heavy bombardment.
226
00:13:24,678 --> 00:13:26,471
Stray rocks,
too small to become planets...
227
00:13:26,514 --> 00:13:28,848
played interplanetary billiards...
228
00:13:30,017 --> 00:13:32,227
striking and bouncing
off other bodies...
229
00:13:32,269 --> 00:13:33,895
with tremendous force.
230
00:13:36,524 --> 00:13:39,275
There were chunks of things
flying everywhere...
231
00:13:39,318 --> 00:13:41,236
and so there were many,
many, many collisions.
232
00:13:41,278 --> 00:13:43,488
A lot of the craters
that you see on the Moon...
233
00:13:43,531 --> 00:13:45,156
were from that
very early period...
234
00:13:45,199 --> 00:13:47,283
right when the solar system
was still forming.
235
00:13:49,954 --> 00:13:54,207
And our Moon reveals just
how volatile the period was on Earth.
236
00:13:56,085 --> 00:13:58,002
We can even calculate
to some degree...
237
00:13:58,045 --> 00:14:00,046
based on cratering
on the Moon...
238
00:14:00,923 --> 00:14:05,552
just how often we got hit
by these rather large objects...
239
00:14:05,594 --> 00:14:08,096
say, six miles across.
240
00:14:09,890 --> 00:14:12,433
Towards the end
of the late heavy bombardment...
241
00:14:12,476 --> 00:14:15,854
we do get asteroids
hundreds of miles in diameter...
242
00:14:15,896 --> 00:14:17,897
coming in
and striking the planet.
243
00:14:18,566 --> 00:14:21,359
Those are certainly capable
of vaporizing the oceans...
244
00:14:21,402 --> 00:14:24,362
and leaving a tremendous scar
where they hit...
245
00:14:24,405 --> 00:14:25,822
raising the surface environment...
246
00:14:25,865 --> 00:14:28,741
far beyond the possibility
of any life surviving.
247
00:14:33,247 --> 00:14:36,207
When the late heavy
bombardment subsided...
248
00:14:36,250 --> 00:14:39,794
approximately
3.8 billion years ago...
249
00:14:39,837 --> 00:14:42,380
objects that didn't
coagulate into planets...
250
00:14:42,423 --> 00:14:45,550
sought refuge
in cosmic graveyards.
251
00:14:48,012 --> 00:14:50,513
In the outer solar system...
252
00:14:50,556 --> 00:14:53,266
leftover rocks reside
in the Kuiper Belt.
253
00:14:54,518 --> 00:14:56,811
In the inner solar system...
254
00:14:56,854 --> 00:14:59,647
they collectively orbit
in the asteroid belt.
255
00:15:01,984 --> 00:15:03,735
Like in the Kuiper belt...
256
00:15:03,777 --> 00:15:07,113
collisional families have also been
discovered in the asteroid belt.
257
00:15:08,282 --> 00:15:11,910
They're pieces of asteroids
that originated from a larger object...
258
00:15:11,952 --> 00:15:17,540
that was broken apart
by a collision with another asteroid.
259
00:15:18,125 --> 00:15:19,918
Collisional families
in the asteroid belt...
260
00:15:19,960 --> 00:15:22,462
result when one asteroid
gets hit by another...
261
00:15:22,504 --> 00:15:24,339
and breaks into pieces.
262
00:15:24,381 --> 00:15:26,132
The fragments
actually stick together...
263
00:15:26,175 --> 00:15:27,550
in their orbit around the Sun.
264
00:15:27,593 --> 00:15:30,470
And astronomers can identify collisional
families...
265
00:15:30,512 --> 00:15:33,890
by looking if their distance
from the Sun is the same...
266
00:15:33,933 --> 00:15:35,767
the tilt of their orbit
is the same...
267
00:15:35,809 --> 00:15:39,729
and the ellipticity, how squashy
the orbit is, is similar.
268
00:15:40,439 --> 00:15:42,231
Also, if we see
that the asteroids...
269
00:15:42,274 --> 00:15:44,442
are made out
of the same material...
270
00:15:44,485 --> 00:15:47,737
it's a good bet that they may have
originated from the same object.
271
00:15:52,034 --> 00:15:55,703
There are approximately twenty
to thirty known collisional families...
272
00:15:55,746 --> 00:15:57,163
in the asteroid belt.
273
00:15:58,165 --> 00:16:01,626
Scientists are keenly interested
in one galactic collision...
274
00:16:01,669 --> 00:16:04,337
that produced
the Baptistina family...
275
00:16:04,380 --> 00:16:08,424
wayward fragments that
originated as one single body...
276
00:16:08,467 --> 00:16:10,593
the size of Mount Everest.
277
00:16:14,056 --> 00:16:18,476
About 160 million years ago,
this colossal rock...
278
00:16:18,519 --> 00:16:22,271
was broadsided by another
giant rock in the asteroid belt.
279
00:16:24,233 --> 00:16:28,653
The deep impact created
a shower of smaller pieces...
280
00:16:28,696 --> 00:16:31,406
over 136,000 of them.
281
00:16:33,367 --> 00:16:36,703
Scientists estimate
that twenty percent of the rocks...
282
00:16:36,745 --> 00:16:38,663
escaped the asteroid belt...
283
00:16:38,706 --> 00:16:42,166
and two percent of them
rained down on Earth.
284
00:16:44,545 --> 00:16:47,422
Some say there's
a ninety percent probability...
285
00:16:47,464 --> 00:16:49,674
that one
of the Baptistina asteroids...
286
00:16:49,717 --> 00:16:54,595
was responsible for
the extinction of the dinosaur.
287
00:16:58,392 --> 00:17:01,185
Sixty-five million years ago...
288
00:17:01,228 --> 00:17:06,774
a myriad of dinosaur species
ruled the prehistoric world...
289
00:17:06,817 --> 00:17:10,820
but a catastrophic event
wiped them off the face of the Earth.
290
00:17:14,658 --> 00:17:18,036
Now scientists have good evidence
of what happened to them.
291
00:17:21,415 --> 00:17:25,001
It's now been confirmed that
a gargantuan cosmic object...
292
00:17:25,044 --> 00:17:26,919
plummeted down from the sky...
293
00:17:26,962 --> 00:17:29,338
and exploded
in the Yucatan Peninsula...
294
00:17:29,381 --> 00:17:32,258
near the modern-day
Mexican village of Chicxulub.
295
00:17:35,220 --> 00:17:37,930
We think it was an object
about six miles in diameter...
296
00:17:37,973 --> 00:17:41,142
coming in at about
twelve miles per second...
297
00:17:41,185 --> 00:17:43,311
which would cause
an impact energy...
298
00:17:43,353 --> 00:17:48,149
of about 65 million
megatons of TNT.
299
00:17:49,109 --> 00:17:50,610
Now, to put that
in perspective...
300
00:17:50,652 --> 00:17:52,987
that's about
one Hiroshima-type blast...
301
00:17:53,030 --> 00:17:56,574
every second for about 140 years.
302
00:17:59,453 --> 00:18:01,454
It was really quite
a hellish environment.
303
00:18:04,249 --> 00:18:07,877
It's believed that this asteroid
contributed to the mass extinction...
304
00:18:07,920 --> 00:18:11,881
of over seventy-five percent
of the species on Earth at the time.
305
00:18:13,801 --> 00:18:16,511
What we think happened
with the Chicxulub impact...
306
00:18:16,553 --> 00:18:19,764
is you have a large asteroid
coming in, it hits the Earth...
307
00:18:19,807 --> 00:18:22,934
it throws an enormous cloud of debris
and dust into the atmosphere.
308
00:18:22,976 --> 00:18:26,646
This effectively screened out
a large fraction of the Sunlight.
309
00:18:26,688 --> 00:18:29,690
So imagine a cloudy day
that lasts for years.
310
00:18:33,821 --> 00:18:37,824
Amy Mainzer has investigated
the rapid die-off of life...
311
00:18:37,866 --> 00:18:39,867
as a result of the impact...
312
00:18:41,245 --> 00:18:43,329
by visiting
the Aquarium of the Pacific...
313
00:18:43,372 --> 00:18:45,373
in Long Beach, California.
314
00:18:47,835 --> 00:18:50,711
We can learn about the effects that an
asteroid impact...
315
00:18:50,754 --> 00:18:54,799
might have had on planet Earth
by looking at this nice tank here.
316
00:18:54,842 --> 00:18:57,260
We see that it's full
of color and life...
317
00:18:57,302 --> 00:19:01,556
lots of different species,
many different animals and plants.
318
00:19:01,598 --> 00:19:05,476
Of course, this whole ecosystem
depends ultimately on the Sun.
319
00:19:05,519 --> 00:19:08,479
Big fish, like we see here,
eat the littler fish.
320
00:19:08,522 --> 00:19:10,231
The little fish eat the plants.
321
00:19:10,274 --> 00:19:13,151
And, ultimately, the plants depend
on sunlight to make energy...
322
00:19:13,193 --> 00:19:15,570
through a process
called photosynthesis.
323
00:19:15,612 --> 00:19:18,156
So you can imagine
that if something happens...
324
00:19:18,198 --> 00:19:20,158
that screens out the sunlight...
325
00:19:20,200 --> 00:19:22,994
all these beautiful animals
will perish.
326
00:19:28,709 --> 00:19:31,961
The apocalyptic event
has been called the K-T extinction...
327
00:19:32,004 --> 00:19:34,630
because of a thin band
of geological signatures...
328
00:19:34,673 --> 00:19:37,216
dating to that time,
all over the world...
329
00:19:37,259 --> 00:19:42,180
known as the Cretaceous-Tertiary,
or K-T boundary.
330
00:19:42,222 --> 00:19:45,892
It separates the age of reptiles
and the age of mammals.
331
00:19:48,395 --> 00:19:52,064
Dinosaur bones are not found
below the K-T boundary.
332
00:19:53,442 --> 00:19:54,942
Some say it's a good indicator...
333
00:19:54,985 --> 00:19:57,695
that they and other species became
extinct...
334
00:19:57,738 --> 00:20:01,282
from the impact that
blocked out sunlight for years.
335
00:20:02,826 --> 00:20:03,826
We can get an idea...
336
00:20:03,869 --> 00:20:06,078
of what might have happened
to life on planet Earth...
337
00:20:06,121 --> 00:20:07,955
following an asteroid impact...
338
00:20:07,998 --> 00:20:11,709
by comparing deep-water
and shallow-water marine systems.
339
00:20:11,752 --> 00:20:13,878
In deeper water,
where there's less sunlight...
340
00:20:13,921 --> 00:20:17,590
there are fewer colorful corals,
fewer types of colorful fish...
341
00:20:17,633 --> 00:20:21,385
and generally less
species diversity overall.
342
00:20:25,140 --> 00:20:27,391
Some scientists
had been skeptical...
343
00:20:27,434 --> 00:20:30,853
that an asteroid
caused the K-T extinction.
344
00:20:30,896 --> 00:20:34,023
For a long time, people didn't
really start to believe...
345
00:20:34,066 --> 00:20:35,942
that asteroids
could really hit the Earth...
346
00:20:35,984 --> 00:20:38,236
and make
a noticeable impression...
347
00:20:38,278 --> 00:20:40,571
until the discovery
of Meteor Crater.
348
00:20:42,824 --> 00:20:46,661
Almost 50,000 years ago,
during the Pleistocene period...
349
00:20:46,703 --> 00:20:49,580
a 150-foot asteroid struck Earth...
350
00:20:51,458 --> 00:20:55,795
with the force
of 2.5 megatons of TNT.
351
00:20:59,049 --> 00:21:03,552
The impact carved out
175 million tons of rock...
352
00:21:03,595 --> 00:21:05,721
in what is now
the Arizona desert.
353
00:21:06,431 --> 00:21:09,058
It left a giant
bowl-shaped hole...
354
00:21:09,101 --> 00:21:11,435
which has been named
Meteor Crater.
355
00:21:12,813 --> 00:21:16,399
In fact, evidence proved
that it had to have resulted...
356
00:21:16,441 --> 00:21:18,150
from an asteroid impact.
357
00:21:18,193 --> 00:21:20,194
A scientist named
Eugene Shoemaker...
358
00:21:20,237 --> 00:21:23,906
found shocked quartz
at the bottom of the crater...
359
00:21:23,949 --> 00:21:28,369
and it's only possible to get
this particular kind of glass...
360
00:21:28,412 --> 00:21:30,663
with extremely high temperatures and
pressures...
361
00:21:30,706 --> 00:21:32,957
generated
in a very short amount of time.
362
00:21:36,169 --> 00:21:40,006
By the 1980s, scientists
hadn't found an impact crater...
363
00:21:40,048 --> 00:21:41,716
linked to the K-T extinction...
364
00:21:42,843 --> 00:21:45,303
but they had dug up
other evidence.
365
00:21:45,345 --> 00:21:48,681
Iridium was procured
from the K-T boundary layer.
366
00:21:50,309 --> 00:21:53,394
Iridium is an element
rare in rocks on Earth...
367
00:21:53,437 --> 00:21:55,563
but common in many asteroids.
368
00:21:57,024 --> 00:21:58,316
It turns out
that some asteroids...
369
00:21:58,358 --> 00:21:59,859
are very high in iridium...
370
00:21:59,901 --> 00:22:03,237
so they made the connection
that this layer of iridium...
371
00:22:03,280 --> 00:22:06,991
that occurred in a sediment layer
some sixty-five million years ago...
372
00:22:07,034 --> 00:22:09,035
was due
to an incoming asteroid.
373
00:22:11,830 --> 00:22:13,873
Even with the discovery
of iridium...
374
00:22:13,915 --> 00:22:18,294
some still doubted an asteroid
caused the K-T extinction...
375
00:22:18,337 --> 00:22:20,254
until the 1990s...
376
00:22:20,297 --> 00:22:23,716
when a Mexican oil company
found the smoking gun.
377
00:22:28,013 --> 00:22:30,014
While drilling off
the Yucatan Peninsula...
378
00:22:30,057 --> 00:22:33,225
they discovered
a hundred-mile-wide impact crater...
379
00:22:33,268 --> 00:22:37,229
buried underwater
beneath 3,000 feet of limestone.
380
00:22:39,358 --> 00:22:41,484
Analysis of the rock confirmed...
381
00:22:41,526 --> 00:22:44,653
that the crater was,
in fact, formed by an asteroid.
382
00:22:46,073 --> 00:22:48,407
And like Meteor Crater
in Arizona...
383
00:22:48,450 --> 00:22:50,951
shocked quartz or glass
was also discovered...
384
00:22:50,994 --> 00:22:52,995
at the K-T impact crater site.
385
00:22:54,998 --> 00:22:56,916
One of the other important
lines of evidence...
386
00:22:56,958 --> 00:23:01,420
for the impact at Chicxulub
was the finding of shocked glass.
387
00:23:01,463 --> 00:23:03,881
Basically, when they looked
at the impact site...
388
00:23:03,924 --> 00:23:05,341
and in regions around it...
389
00:23:05,384 --> 00:23:06,384
and all around the world,
in fact...
390
00:23:06,426 --> 00:23:09,345
evidence was found of glass
that was fused.
391
00:23:09,388 --> 00:23:12,723
It was basically created
when the giant explosion fused it.
392
00:23:12,766 --> 00:23:16,435
And this particular glass type
is really only found...
393
00:23:16,478 --> 00:23:19,146
in the presence of
an extremely large explosion.
394
00:23:24,736 --> 00:23:27,405
Today, many scientists agree...
395
00:23:27,447 --> 00:23:30,032
an asteroid caused
the K-T extinction...
396
00:23:30,075 --> 00:23:32,326
sixty-five million years ago.
397
00:23:36,164 --> 00:23:38,707
And now some are trying
to zero in...
398
00:23:38,750 --> 00:23:41,544
on the exact asteroid
that caused the event.
399
00:23:44,381 --> 00:23:47,007
Sediments procured
from the Chicxulub site...
400
00:23:47,050 --> 00:23:50,928
reveal the asteroid was
a carbonaceous chondrite...
401
00:23:50,971 --> 00:23:52,638
a very primitive rock.
402
00:23:53,598 --> 00:23:56,100
These types of rocks
have similar compositions...
403
00:23:56,143 --> 00:23:59,687
to the Baptistina family,
a collection of asteroids...
404
00:23:59,729 --> 00:24:02,398
that once originated
from a larger rock.
405
00:24:04,025 --> 00:24:05,776
So some say the odds
are great...
406
00:24:05,819 --> 00:24:07,736
that a Baptistina family member...
407
00:24:07,779 --> 00:24:11,740
triggered the mass extinction
that wiped out the dinosaur.
408
00:24:17,581 --> 00:24:21,041
Today, the Baptistina family
could still pose a threat.
409
00:24:22,127 --> 00:24:25,296
Within the asteroid belt,
its relatives span a region...
410
00:24:25,338 --> 00:24:27,840
containing
two gravitational hatches.
411
00:24:29,134 --> 00:24:31,051
These are areas
where a slight nudge...
412
00:24:31,094 --> 00:24:34,096
could boot an asteroid
out of its orbital zone.
413
00:24:35,098 --> 00:24:37,975
It could send it soaring
into the inner solar system...
414
00:24:38,018 --> 00:24:41,187
where it could slam
into planet Earth.
415
00:24:47,444 --> 00:24:50,779
Cosmic collisions
are not a thing of the past.
416
00:24:50,822 --> 00:24:54,158
They're ongoing
and potentially deadly.
417
00:24:56,369 --> 00:25:00,122
Within the asteroid belt
between planets Jupiter and Mars...
418
00:25:00,165 --> 00:25:02,249
lives the Baptistina family...
419
00:25:03,126 --> 00:25:06,378
a group of rocks that originated
from a larger body...
420
00:25:06,421 --> 00:25:08,881
that was shattered
due to a collision.
421
00:25:11,301 --> 00:25:14,303
After the impact,
some Baptistina family members...
422
00:25:14,346 --> 00:25:16,347
were ejected
from the asteroid belt.
423
00:25:18,391 --> 00:25:21,769
It's believed that at least one
eventually struck Earth...
424
00:25:21,811 --> 00:25:24,146
65 million years ago...
425
00:25:27,108 --> 00:25:30,569
and caused the mass extinction
of the dinosaur.
426
00:25:32,656 --> 00:25:34,323
And the K-T extinction event...
427
00:25:34,366 --> 00:25:37,701
may not be the end
of the Baptistina family's wrath.
428
00:25:39,037 --> 00:25:40,788
Some say another relative...
429
00:25:40,830 --> 00:25:43,791
could threaten our planet
again in the future.
430
00:25:45,919 --> 00:25:49,547
It's always possible that another
member of the Baptistina family...
431
00:25:49,589 --> 00:25:51,715
could make its way
into the inner solar system...
432
00:25:51,758 --> 00:25:53,092
and hit the Earth.
433
00:25:57,389 --> 00:26:00,724
Researchers have been
observing the Baptistina family.
434
00:26:00,767 --> 00:26:04,770
They've discovered that
its relatives share similar orbits.
435
00:26:05,939 --> 00:26:10,067
But over time, a thermal effect,
called the Yarkovsky force...
436
00:26:10,110 --> 00:26:12,736
is moving them
into a danger zone.
437
00:26:15,031 --> 00:26:18,576
The Yarkovsky force is
a thermal effect on asteroids...
438
00:26:18,618 --> 00:26:21,245
that has the ability
to alter their orbits.
439
00:26:21,288 --> 00:26:23,247
When they get hit with sunlight...
440
00:26:23,290 --> 00:26:25,583
it takes a little while
for the asteroid to heat up.
441
00:26:25,625 --> 00:26:27,960
This results
in a thermal radiation...
442
00:26:28,003 --> 00:26:31,589
that gives the asteroid a little push,
which changes its orbit.
443
00:26:31,631 --> 00:26:34,133
The Yarkovsky force
is not very big...
444
00:26:34,175 --> 00:26:36,927
but over millions of years,
it adds up.
445
00:26:41,433 --> 00:26:44,560
Over time,
this gradual orbital shifting...
446
00:26:44,603 --> 00:26:48,147
could produce
another cataclysmic impact.
447
00:26:49,941 --> 00:26:51,483
Simulations have been done...
448
00:26:51,526 --> 00:26:55,195
to show that when
these Baptistina family members...
449
00:26:55,238 --> 00:26:58,240
happen to get into a resonance
with the planet Jupiter...
450
00:26:58,283 --> 00:27:00,117
in other words, a resonance...
451
00:27:00,160 --> 00:27:03,287
where the asteroid orbits
seven times...
452
00:27:03,330 --> 00:27:06,165
for every two orbits of Jupiter...
453
00:27:06,207 --> 00:27:08,542
when that
special moment happens...
454
00:27:08,585 --> 00:27:11,962
the asteroids can get shot
into the inner solar system...
455
00:27:12,005 --> 00:27:14,465
just like hitting a flipper
on a pinball machine.
456
00:27:14,507 --> 00:27:16,342
Some fraction
of those asteroids...
457
00:27:16,384 --> 00:27:18,510
are going to get
into Earth-crossing orbits...
458
00:27:18,553 --> 00:27:21,180
which means they have a chance
of hitting the Earth.
459
00:27:23,350 --> 00:27:27,936
If an impact event happened
anywhere on planet Earth today...
460
00:27:27,979 --> 00:27:30,731
it would destroy civilization itself.
461
00:27:31,399 --> 00:27:34,443
Even if you managed to survive
in a remote place...
462
00:27:34,486 --> 00:27:35,903
you would most likely starve.
463
00:27:35,945 --> 00:27:39,490
Humans would probably survive
in a few places and re-colonize...
464
00:27:39,532 --> 00:27:41,909
but civilization would collapse.
465
00:27:41,951 --> 00:27:44,161
These are civilization-killing events.
466
00:27:47,957 --> 00:27:51,919
Future collisions could be
hazardous to life on Earth.
467
00:27:51,961 --> 00:27:56,173
But the Chicxulub impact
was a fortuitous moment...
468
00:27:56,216 --> 00:27:58,050
for the evolution of humans.
469
00:28:00,345 --> 00:28:03,555
Research scientist Luann Becker
has spent her career...
470
00:28:03,598 --> 00:28:06,475
investigating
mass extinction events.
471
00:28:08,812 --> 00:28:11,397
People say that if the dinosaurs
had not perished...
472
00:28:11,439 --> 00:28:12,856
then there would be no people.
473
00:28:12,899 --> 00:28:14,983
Mammals would not have
taken over...
474
00:28:15,026 --> 00:28:17,945
if the dinosaurs
had been so fortunate...
475
00:28:17,987 --> 00:28:19,988
to have been able
to continue to reign...
476
00:28:20,031 --> 00:28:23,158
beyond the 135, 40 million years...
477
00:28:23,201 --> 00:28:24,576
that they happened
to be on the Earth.
478
00:28:27,205 --> 00:28:31,333
Becker claims, like humans,
dinosaurs also evolved...
479
00:28:31,376 --> 00:28:33,752
after an epic extinction event...
480
00:28:33,795 --> 00:28:36,296
the largest in the history
of planet Earth.
481
00:28:37,632 --> 00:28:42,678
It's the Permian-Triassic extinction,
also known as the Great Dying.
482
00:28:44,305 --> 00:28:45,681
It's also kind of ironic to me...
483
00:28:45,724 --> 00:28:48,016
that if our theory is correct
about the Permian...
484
00:28:48,059 --> 00:28:51,186
the dinosaur came in
with an impact event...
485
00:28:51,229 --> 00:28:52,813
and went out
with an impact event...
486
00:28:52,856 --> 00:28:54,356
which is pretty interesting.
487
00:28:56,776 --> 00:28:59,445
It's perhaps the ultimate
cosmic cold case...
488
00:28:59,487 --> 00:29:03,323
a mass extinction unmatched
in the history of the universe.
489
00:29:06,077 --> 00:29:08,412
Two hundred and fifty
million years ago...
490
00:29:08,455 --> 00:29:10,581
long before the dinosaur ruled...
491
00:29:10,623 --> 00:29:13,125
smaller creatures
and abundant plant life...
492
00:29:13,168 --> 00:29:16,754
prospered on Earth during
the Permian-Triassic period.
493
00:29:16,796 --> 00:29:21,842
Then some mysterious event
wiped out almost all life at that time.
494
00:29:24,387 --> 00:29:27,556
In fact, it's the most
severe extinction with respect...
495
00:29:27,599 --> 00:29:30,934
to how many different
animals and plants perished.
496
00:29:30,977 --> 00:29:35,814
It's the biggest extinction event
in the history of life on our planet.
497
00:29:37,025 --> 00:29:41,111
Becker is on a mission
to solve this prehistoric crime.
498
00:29:41,154 --> 00:29:44,698
Like the K-T impact that
probably killed the dinosaurs...
499
00:29:44,741 --> 00:29:46,617
she claims
to have uncovered evidence...
500
00:29:46,659 --> 00:29:51,455
that a giant asteroid also caused
the Permian-Triassic extinction...
501
00:29:51,498 --> 00:29:55,209
which occurred about
185 million years earlier.
502
00:29:59,339 --> 00:30:01,381
During the Permian-Triassic period...
503
00:30:01,424 --> 00:30:06,261
our world was comprised of
one supercontinent called Pangaea...
504
00:30:06,304 --> 00:30:09,181
and a super ocean
called Panthalassa.
505
00:30:11,309 --> 00:30:12,643
According to Becker...
506
00:30:12,685 --> 00:30:15,687
a seven-mile-wide object
slammed into the ocean...
507
00:30:15,730 --> 00:30:17,981
near the southern tip
of the supercontinent...
508
00:30:18,024 --> 00:30:20,275
which is now
off northwest Australia.
509
00:30:22,070 --> 00:30:25,531
If you were standing on the beach
250 millions years ago...
510
00:30:25,573 --> 00:30:28,325
you'd probably have a pretty good
view of this particular event.
511
00:30:28,368 --> 00:30:32,496
You have a large body, the size
of, say, Mount Everest...
512
00:30:32,539 --> 00:30:36,583
rigid body slamming
into the continental margin...
513
00:30:36,626 --> 00:30:38,001
along the actual beach...
514
00:30:39,379 --> 00:30:43,340
creating a huge earthquake,
mega tsunamis...
515
00:30:43,383 --> 00:30:48,345
injecting miles and miles of dust debris
up into the atmosphere...
516
00:30:48,388 --> 00:30:50,347
distributing itself globally...
517
00:30:50,390 --> 00:30:53,809
in such a manner
that it blocks sunlight out.
518
00:30:53,852 --> 00:30:56,520
You could have had darkness
for months at a time.
519
00:30:56,563 --> 00:30:58,981
This is enough to shut down
photosynthesis.
520
00:30:59,023 --> 00:31:01,024
That's the top of the food chain...
521
00:31:01,067 --> 00:31:03,026
and that just has
a trickle-down effect.
522
00:31:04,404 --> 00:31:06,196
If Becker's theory is correct...
523
00:31:06,239 --> 00:31:09,449
this impact could have wiped out
most life on Earth...
524
00:31:11,786 --> 00:31:15,873
since it was concentrated
on one continent and one ocean.
525
00:31:18,251 --> 00:31:21,003
An extinction event
of this magnitude...
526
00:31:21,045 --> 00:31:24,006
would have allowed for complete
evolutionary change...
527
00:31:25,633 --> 00:31:29,261
thus paving the way
for the dinosaurs to evolve.
528
00:31:31,222 --> 00:31:32,472
It was only because...
529
00:31:32,515 --> 00:31:34,892
the Permian-Triassic
extinction event occurred...
530
00:31:34,934 --> 00:31:37,936
and what I consider
to be somewhat attributed...
531
00:31:37,979 --> 00:31:39,479
to this impact event...
532
00:31:39,522 --> 00:31:42,232
that the dinosaurs
were able to evolve.
533
00:31:44,277 --> 00:31:48,405
Little geological evidence remains
of the Permian-Triassic extinction.
534
00:31:48,448 --> 00:31:52,034
There are very few
250-million-year-old rocks...
535
00:31:52,076 --> 00:31:53,243
left on Earth...
536
00:31:53,286 --> 00:31:56,121
because they've been recycled
by plate tectonics.
537
00:31:59,500 --> 00:32:01,585
But Becker says
she's found traces...
538
00:32:01,628 --> 00:32:06,131
of the actual impact crater
in northwestern Australia.
539
00:32:13,806 --> 00:32:16,099
The Permian-Triassic extinction...
540
00:32:17,810 --> 00:32:19,519
known as the Great Dying...
541
00:32:19,562 --> 00:32:23,440
was the biggest extinction event
in the history of planet Earth.
542
00:32:23,483 --> 00:32:28,236
Ninety percent of all life
perished 250 million years ago.
543
00:32:28,279 --> 00:32:31,031
More more creatures expired
during this period...
544
00:32:31,074 --> 00:32:33,742
than the K-T extinction
that killed the dinosaurs...
545
00:32:33,785 --> 00:32:37,663
over 185 million years later.
546
00:32:37,705 --> 00:32:42,209
The cause of the Permian-Triassic
extinction has gone unsolved.
547
00:32:45,004 --> 00:32:48,465
But now, research scientist
Luann Becker and others...
548
00:32:48,508 --> 00:32:50,509
think an asteroid
caused the event...
549
00:32:53,429 --> 00:32:56,139
and they've uncovered
a possible impact crater...
550
00:32:56,182 --> 00:32:59,851
buried under sediments offshore
of northwestern Australia.
551
00:33:01,396 --> 00:33:03,814
We believe we found
a very good candidate...
552
00:33:03,856 --> 00:33:06,650
for what is
the impact event itself.
553
00:33:06,693 --> 00:33:09,486
It's much older,
it's a lot more complicated...
554
00:33:09,529 --> 00:33:12,322
and a lot more
geologically processed.
555
00:33:12,365 --> 00:33:14,700
It's not a perfect circle anymore.
556
00:33:14,742 --> 00:33:16,827
It doesn't look like a bull's-eye.
557
00:33:16,869 --> 00:33:19,162
Most of the Permian rocks
have been subducted...
558
00:33:19,205 --> 00:33:22,124
and they're long gone
or eroded away.
559
00:33:25,420 --> 00:33:27,004
The evidence
for an impact there...
560
00:33:27,046 --> 00:33:28,922
is marginal
and highly controversial.
561
00:33:30,133 --> 00:33:32,009
Some scientists are skeptical...
562
00:33:32,051 --> 00:33:33,844
that Becker has found
an impact crater...
563
00:33:33,886 --> 00:33:35,804
from the Permian-Triassic period.
564
00:33:37,640 --> 00:33:41,935
No good crater has been found
to match the Permian-Triassic age.
565
00:33:41,978 --> 00:33:46,857
There was a claim of a structure
off of the west coast of Australia...
566
00:33:46,899 --> 00:33:52,904
but it's not as clean and
as clear as the K-T crater.
567
00:33:52,947 --> 00:33:54,448
We don't have a smoking gun.
568
00:33:56,743 --> 00:33:59,870
But Becker claims
she has found the smoking gun.
569
00:33:59,912 --> 00:34:03,165
What's more, she and her team
have traveled to Antarctica...
570
00:34:03,207 --> 00:34:09,504
Australia, Africa, and Japan, where
the oldest rocks on Earth exist.
571
00:34:09,547 --> 00:34:13,050
They claim to have found
forty impact tracers.
572
00:34:13,092 --> 00:34:15,886
These are extraterrestrial
mineral fragments...
573
00:34:15,928 --> 00:34:17,596
recovered from rock layers...
574
00:34:17,638 --> 00:34:20,057
dating to
the Permian-Triassic period.
575
00:34:22,935 --> 00:34:25,020
We have found
what we consider to be...
576
00:34:25,063 --> 00:34:28,565
little bits and pieces
of impact debris...
577
00:34:28,608 --> 00:34:31,401
which literally
looks like what we'd find...
578
00:34:31,444 --> 00:34:33,111
if we were looking at a meteorite.
579
00:34:33,154 --> 00:34:36,573
It's possible for some
of the impact meteoritic debris...
580
00:34:36,616 --> 00:34:39,367
to fall back down and
get preserved in the rock layer.
581
00:34:40,787 --> 00:34:41,912
What hasn't been recovered...
582
00:34:41,954 --> 00:34:45,749
from the Permian-Triassic
rock layer is iridium.
583
00:34:45,792 --> 00:34:47,584
It's the meteoritic substance...
584
00:34:47,627 --> 00:34:49,836
that helped to convince
many scientists...
585
00:34:49,879 --> 00:34:53,090
that an asteroid impact caused
the extinction of the dinosaurs...
586
00:34:53,132 --> 00:34:55,675
sixty-five million years ago.
587
00:34:58,429 --> 00:35:01,932
Colleagues want to try
to get real nitpicky about...
588
00:35:01,974 --> 00:35:03,683
"Well, you should have
found iridium, too. "
589
00:35:03,726 --> 00:35:05,519
Well, we're not finding iridium...
590
00:35:05,561 --> 00:35:08,355
in some of the places
we would expect to find it...
591
00:35:08,397 --> 00:35:11,024
like in some of the cometary
material that we brought back.
592
00:35:11,067 --> 00:35:13,318
So what's the explanation for that?
593
00:35:13,361 --> 00:35:15,320
It's just that there
are different bodies...
594
00:35:15,363 --> 00:35:16,655
and they're not all the same.
595
00:35:18,699 --> 00:35:20,867
Although Becker
hasn't found iridium...
596
00:35:20,910 --> 00:35:24,246
she has procured chromium
in rocks from Antarctica.
597
00:35:24,288 --> 00:35:27,124
Like iridium,
chromium is just as rare...
598
00:35:27,166 --> 00:35:29,251
and is more abundant
in space rocks.
599
00:35:32,672 --> 00:35:34,631
So did an asteroid
actually cause...
600
00:35:34,674 --> 00:35:36,842
the Permian-Triassic
mass extinction...
601
00:35:38,052 --> 00:35:39,719
or merely help it along?
602
00:35:42,056 --> 00:35:44,516
It appears that life
was struggling to survive...
603
00:35:44,559 --> 00:35:46,810
250 million years ago.
604
00:35:46,853 --> 00:35:50,230
The planet was undergoing
severe volcanism...
605
00:35:50,273 --> 00:35:52,524
which was choking
the atmosphere.
606
00:35:54,527 --> 00:35:57,821
One possibility is that
a large volcano in Siberia...
607
00:35:57,864 --> 00:36:00,782
which was sitting atop
an enormous coal deposit...
608
00:36:00,825 --> 00:36:03,827
may have released
a lot of greenhouse gases...
609
00:36:03,870 --> 00:36:06,454
into the atmosphere,
such as CO2 and methane...
610
00:36:06,497 --> 00:36:10,375
which would cause a massive die-off
among marine organisms...
611
00:36:10,418 --> 00:36:13,461
and also an enormous amount
of global warming...
612
00:36:13,504 --> 00:36:16,715
which would have been bad
for the terrestrial animals as well.
613
00:36:18,551 --> 00:36:19,843
When you go back and look at...
614
00:36:19,886 --> 00:36:22,596
what does correlate with
these other extinction events...
615
00:36:22,638 --> 00:36:24,222
virtually in all the cases...
616
00:36:24,265 --> 00:36:29,019
there's evidence of a mass
volcanic episode at the same time...
617
00:36:29,061 --> 00:36:33,648
and all of the mass extinction events,
including the K-T...
618
00:36:33,691 --> 00:36:35,400
are strongly
and intimately associated...
619
00:36:35,443 --> 00:36:37,235
with these volcanic eruptions.
620
00:36:38,404 --> 00:36:40,405
The extinction events
may have happened anyway...
621
00:36:40,448 --> 00:36:43,533
but then this damn meteor
came in...
622
00:36:43,576 --> 00:36:45,035
and really mucked things up.
623
00:36:45,077 --> 00:36:46,578
It was a double whammy.
624
00:36:48,915 --> 00:36:51,249
Becker claims
that volcanism alone...
625
00:36:51,292 --> 00:36:53,877
couldn't have caused
the Permian-Triassic extinction.
626
00:36:53,920 --> 00:36:57,589
And she says she has
even more evidence to prove it.
627
00:36:59,926 --> 00:37:03,553
We have found, I think,
some of the best proxies...
628
00:37:03,596 --> 00:37:06,514
for what we consider
to be impact tracers.
629
00:37:06,557 --> 00:37:10,894
This includes shocked quartz
in multiple locations...
630
00:37:10,937 --> 00:37:15,148
in and around
Australia and Antarctica...
631
00:37:15,191 --> 00:37:18,902
glass that has seen pressures that are far
beyond...
632
00:37:18,945 --> 00:37:21,905
what you can even think
about happening...
633
00:37:21,948 --> 00:37:23,740
geologically speaking,
on the Earth.
634
00:37:24,659 --> 00:37:25,659
This could not
have been mimicked...
635
00:37:25,701 --> 00:37:27,369
by some kind
of volcanic event.
636
00:37:27,411 --> 00:37:31,414
It has to be something that
was produced by an impact event.
637
00:37:33,125 --> 00:37:36,378
And I think that when you have
that kind of direct evidence...
638
00:37:36,420 --> 00:37:38,505
that's as good as it gets
in this business.
639
00:37:41,467 --> 00:37:43,843
The scientific community
is still debating...
640
00:37:43,886 --> 00:37:46,846
whether an asteroid impact
helped trigger...
641
00:37:46,889 --> 00:37:51,142
the Permian-Triassic extinction
250 million years ago.
642
00:37:52,812 --> 00:37:55,230
But space rocks
aren't the only objects...
643
00:37:55,273 --> 00:37:57,232
that can cause cosmic upheaval.
644
00:38:01,821 --> 00:38:06,116
In fact, our own Milky Way galaxy
is currently involved...
645
00:38:06,158 --> 00:38:08,326
in a multiple-galaxy collision.
646
00:38:12,498 --> 00:38:16,793
Imagine you're a galaxy
cruising through space.
647
00:38:16,836 --> 00:38:21,506
The traffic may seem light,
but at any moment...
648
00:38:21,549 --> 00:38:25,093
you could be involved
in a head-on collision.
649
00:38:25,678 --> 00:38:29,973
Cosmic crashes like this
happen all the time...
650
00:38:30,016 --> 00:38:33,018
particularly when galaxies
get too close to one another.
651
00:38:36,772 --> 00:38:39,858
Galaxies have interacted,
they've collided, they've merged...
652
00:38:39,900 --> 00:38:41,651
they've ripped
each other apart...
653
00:38:41,694 --> 00:38:43,403
and it's still going on today.
654
00:38:43,446 --> 00:38:47,365
So galactic collisions have always
been a part of the life of a galaxy...
655
00:38:47,408 --> 00:38:49,075
and they always will be.
656
00:38:52,163 --> 00:38:54,039
Research scientist
Michelle Thaller...
657
00:38:54,081 --> 00:38:57,792
knows how violent
galaxy collisions can be...
658
00:38:57,835 --> 00:39:01,171
especially when they involve
multiple galaxies.
659
00:39:02,923 --> 00:39:06,551
At this very moment,
NASA's Spitzer Space Telescope...
660
00:39:06,594 --> 00:39:09,304
is witnessing
the ultimate pile-up:
661
00:39:09,347 --> 00:39:14,184
Four supermassive galaxies
colliding on a cosmic freeway...
662
00:39:14,226 --> 00:39:17,729
approximately five billion
light-years away from Earth.
663
00:39:20,900 --> 00:39:24,194
They're all coming together now
at millions of miles an hour...
664
00:39:24,236 --> 00:39:25,737
and they will merge together.
665
00:39:25,780 --> 00:39:30,033
So we found an absolutely
titanic collision of galaxies.
666
00:39:30,076 --> 00:39:32,410
You can think of most galaxy
collisions as being like...
667
00:39:32,453 --> 00:39:34,788
you know, little compact cars
maybe piling up...
668
00:39:34,830 --> 00:39:36,539
a small collision on a highway...
669
00:39:36,582 --> 00:39:39,250
but in this case,
we're seeing maybe, you know...
670
00:39:39,293 --> 00:39:42,754
four eighteen-wheelers
colliding together head-on...
671
00:39:42,797 --> 00:39:45,048
and in the process,
billions of stars...
672
00:39:45,091 --> 00:39:47,550
are being just scattered
away from this galaxy.
673
00:39:50,763 --> 00:39:54,265
This violent collision
is still happening.
674
00:39:54,308 --> 00:39:56,434
When the impact
is finally over...
675
00:39:56,477 --> 00:40:01,272
the four will be jumbled together
to form one beastly galaxy...
676
00:40:01,315 --> 00:40:03,983
ten times the mass
of our Milky Way.
677
00:40:04,860 --> 00:40:08,863
It will be one of the largest galaxies
in the entire universe.
678
00:40:10,783 --> 00:40:14,452
And this is just one of many
multiple-galaxy collisions.
679
00:40:16,122 --> 00:40:17,956
The Milky Way
will eventually merge...
680
00:40:17,998 --> 00:40:21,084
with our neighbor galaxy, Andromeda...
681
00:40:21,127 --> 00:40:23,795
which could prove to be
a spectacular collision.
682
00:40:25,297 --> 00:40:28,466
But right now, our galaxy
is actually colliding...
683
00:40:28,509 --> 00:40:32,804
with two smaller galaxies
which is causing quite a stir.
684
00:40:35,015 --> 00:40:36,349
There's two galaxies right now...
685
00:40:36,392 --> 00:40:38,768
that are actually
relatively small galaxies...
686
00:40:38,811 --> 00:40:41,062
but they're colliding
with the Milky Way right now.
687
00:40:41,105 --> 00:40:42,856
One is called
the Sagittarius dwarf...
688
00:40:42,898 --> 00:40:45,442
because we see it near
the constellation Sagittarius...
689
00:40:45,484 --> 00:40:48,570
and another is called
the Canis Majoris dwarf galaxy.
690
00:40:48,612 --> 00:40:49,946
Now, the second one...
691
00:40:49,989 --> 00:40:52,073
the Canis Majoris dwarf galaxy, is very
interesting...
692
00:40:52,116 --> 00:40:54,159
because it appears
to have been sort of...
693
00:40:54,201 --> 00:40:56,786
drawn into the Milky Way
and ripped apart...
694
00:40:56,829 --> 00:40:59,622
as it orbited around
the center of the Milky Way.
695
00:40:59,665 --> 00:41:02,167
So we can actually see
streams of stars...
696
00:41:02,209 --> 00:41:03,960
all going around together...
697
00:41:04,003 --> 00:41:05,837
that are the remnants
of this poor little galaxy...
698
00:41:05,880 --> 00:41:06,963
that got ripped apart.
699
00:41:08,674 --> 00:41:11,801
Galaxy collisions produce
billions of stars...
700
00:41:12,803 --> 00:41:15,430
but can these stars
also collide?
701
00:41:17,266 --> 00:41:20,727
The space between stars
in our galaxies is absolutely huge.
702
00:41:20,769 --> 00:41:22,562
If the Sun were about the size
of a basketball...
703
00:41:22,605 --> 00:41:24,230
and I'm here in Los Angeles...
704
00:41:24,273 --> 00:41:25,523
then the nearest star...
705
00:41:25,566 --> 00:41:27,817
would be about
the same-sized star in New York.
706
00:41:27,860 --> 00:41:29,903
Imagine a basketball
in New York.
707
00:41:29,945 --> 00:41:31,446
There's so much space
between stars...
708
00:41:31,489 --> 00:41:33,490
the stellar collisions
are so rare.
709
00:41:36,494 --> 00:41:39,162
Although rare,
star collisions can occur...
710
00:41:39,205 --> 00:41:41,873
where stellar objects are
formed in dense clusters.
711
00:41:47,296 --> 00:41:50,840
We've seen examples
where in a cluster of stars...
712
00:41:50,883 --> 00:41:54,844
one star seems to be more
massive than the other ones...
713
00:41:54,887 --> 00:41:57,847
younger than the other ones,
and spinning much faster...
714
00:41:57,890 --> 00:41:59,682
than the other stars
that it was born with.
715
00:42:01,852 --> 00:42:04,604
These young stars are called
blue stragglers.
716
00:42:06,732 --> 00:42:09,400
They occur in unusually
dense groups of stars...
717
00:42:09,443 --> 00:42:11,277
called globular clusters.
718
00:42:13,739 --> 00:42:15,281
These are called
blue stragglers...
719
00:42:15,324 --> 00:42:16,324
because they seem
to be younger.
720
00:42:16,367 --> 00:42:20,161
They're aging less quickly
than the other stars of the clusters.
721
00:42:20,204 --> 00:42:22,747
So it's very possible
that these are caused...
722
00:42:22,790 --> 00:42:25,041
when two stars
actually merge together.
723
00:42:25,084 --> 00:42:26,668
As these stars
approached each other...
724
00:42:26,710 --> 00:42:28,711
they spun each other up
with their gravity...
725
00:42:28,754 --> 00:42:32,382
and so you get this very
fast-rotating, large, bright star.
726
00:42:36,387 --> 00:42:40,098
And star collisions are
not mild galactic fender-benders.
727
00:42:41,350 --> 00:42:43,643
They can be quite destructive.
728
00:42:45,187 --> 00:42:46,854
They would sort of loop
closer and closer together...
729
00:42:46,897 --> 00:42:48,439
going faster and faster.
730
00:42:48,482 --> 00:42:50,567
They'd probably get
to many hundreds of thousands...
731
00:42:50,609 --> 00:42:52,569
if not millions of miles an hour.
732
00:42:52,611 --> 00:42:54,320
And they'd begin to rip
bits of each other off...
733
00:42:54,363 --> 00:42:55,863
as they came
close to each other.
734
00:42:55,906 --> 00:42:57,657
So a stellar collision could be...
735
00:42:57,700 --> 00:42:59,826
an extremely dramatic,
violent thing to watch.
736
00:43:02,162 --> 00:43:06,040
Eventually, if the mass transfer
happens enough over enough time...
737
00:43:06,083 --> 00:43:08,042
the orbits will shrink...
738
00:43:08,085 --> 00:43:10,420
and those two stars will get
closer and closer together...
739
00:43:10,462 --> 00:43:11,963
and they could
eventually merge...
740
00:43:12,006 --> 00:43:14,549
forming either
one single giant star...
741
00:43:14,592 --> 00:43:18,595
or eventually collapsing into,
say, a neutron star or a black hole.
742
00:43:21,307 --> 00:43:23,433
Whether they're star
and galaxy mergers...
743
00:43:24,977 --> 00:43:27,145
or asteroid and comet impacts...
744
00:43:28,647 --> 00:43:31,274
cosmic collisions
will continue to happen...
745
00:43:31,317 --> 00:43:33,776
as long as the universe exists.
746
00:43:35,070 --> 00:43:38,406
By gaining knowledge about
these uncontrollable events...
747
00:43:38,449 --> 00:43:40,450
we can reach
a better understanding...
748
00:43:40,492 --> 00:43:46,831
about the origins of the universe,
and possibly predict its future.
749
00:43:50,085 --> 00:43:52,253
Cosmic collisions
have been a major factor...
750
00:43:52,296 --> 00:43:54,631
shaping the evolution
and history of the planet.
751
00:43:54,673 --> 00:43:56,716
Earth wouldn't be here
without them.
752
00:43:56,759 --> 00:44:00,011
The chemicals that life needs
to get started with...
753
00:44:00,054 --> 00:44:03,056
came out as a result
of these impact processes.
754
00:44:03,807 --> 00:44:06,684
This has actually been
a very important factor...
755
00:44:06,727 --> 00:44:08,436
in the history of life
on this planet.
756
00:44:08,479 --> 00:44:10,313
Cosmic collisions
are responsible...
757
00:44:10,356 --> 00:44:12,732
for things as varied
as asteroid impacts...
758
00:44:14,568 --> 00:44:18,237
galaxy mergers,
formation of giant stars.
759
00:44:19,323 --> 00:44:20,948
They're obviously key
to our understanding...
760
00:44:20,991 --> 00:44:23,034
of the phenomena
in the universe.
65089
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