The Universe

Male narrator: In the beginning, there was darkness,

and then, bang,

giving birth to an endless expanding existence

of time, space, and matter.

Every day, new discoveries are unlocking the mysterious,

the mind-blowing, the deadly secrets

of a place we call The Universe .

Ohart a daring course with comets,

the cosmic time travelers of the skies.

- These mysterious objects have been agents of change.

They've been agents of destruction.

Narrator: Discover why these celestial bodies

carry secrets from our past

and cast doom over our future.

- If it's getting into our on-ramp,

we need to worry about it.

- There's very little we can do

other than sending a giant bomb toward them

and trying to deflect them.

Narrator: Brace yourself as we rendezvous

with the frozen intruders from the great beyond

on an epic journey to "Ride the Oomet."

The.Universe.S07E06.DVDRip.XviD-FFNDVD English SRT Subtitles - UF (v1.00)

They appear out of nowhere,

gliding slowly across the nighttime sky

and then disappearing from sight.

Throughout human history, ancient cultures

believed these celestial intruders

carried special powers from the gods,

mystical messengers of life and death.

Scientists like to think

that comets are fairly mysterious objects,

because we know that they're very old.

They're like frozen time capsules

from when our solar system was first formed.

- Oomets are a bit of show-offs.

They come into the night sky unannounced, unpredicted.

In the Middle Ages, they were thought to be fireballs

thrown at a sinful Earth

from the right hand of an avenging god.

And so they've always been feared or seen as mysterious.

Narrator: We're going to hitch a ride

on a bold, uncharted journey through the secret life

of our solar system's comets.

Our daring quest begins 4.5 billion years ago,

as our futuristic spacecraft time-travels

back to the birth of our solar system.

We zigzag through a maelstrom of debris

to catch our first glimpse of comets,

the wayward rocks that didn't meld into planets.

- Oomets are basically dirty snowballs

or icy dirtballs.

They consist of rocks and dust and dirt

held together by ices-

water ice, ammonia, methane, carbon dioxide, dry ice.

That's sort of like the glue

that holds all these little pebbles

and particles of dust together.

Narrator: The heart of these cosmic icebergs is the nucleus,

or central core, which averages in size

from a half mile wide to as big as a modern city.

- One of the things we've learned

by flying close by and observing the nuclei of comets

is that they're these strange

sort of compacted conglomerates of ice and rock.

They're not uniform.

They're not perfectly mixed.

They're quite chunky and oddly shaped.

The nuclei of comets are...

very fragile entities.

If you had a chunk,

you could probably break it easily in your hands.

Narrator: Up close,

comets look like bland chunks of charcoal

rather than supersized snowballs.

They don't even remotely resemble

the glowing orbs we see in our pitch-black skies.

- We think that most comets are extremely dark

on their surfaces, that the surfaces are covered

with something kind of like barbecue soot,

this really dark, black material

that makes them very difficult to see.

Narrator: While their asteroid cousins

share similar properties, such as rock and metal,

scientists suspect that comets were born farther out,

near the gas giant planets,

where it's much colder,

so they possess more ices and volatile elements.

About 3.8 billion years ago,

many of these icy bodies were whisked away

to the Kuiper belt, a frigid neighborhood

just beyond the outermost planet, Neptune.

- Icy objects in the Kuiper belt probably formed

closer in toward the Sun, where the giant planets are,

but then gravitational interactions

with those giant planets made those icy objects

migrate outward.

Narrator: Our spacecraft navigates

through this dark, disklike region,

which is almost 2 billion miles wide

and is estimated to hold over 6 billion comets.

We eventually touch down

on the surface of one of these icy boulders.

- Landing on a comet would be a pretty tricky affair.

So you could kind of imagine dirty snow

that's covered with exhaust,

and if you step on it,

in places, you can punch through

to places where there's more fresh material underneath it.

Narrator: The Kuiper belt objects

appear to have fairly stable orbits,

so they won't be that much fun to ride.

We lift off in search of a comet

that will cut a more exciting path

through our solar system.

We navigate farther out

to a sparsely populated region called the scattered disc,

which is home to icy bodies with long, elliptical orbits.

The slightest disturbance can send these unstable objects

careening into the inner solar system,

where they become known as short-period comets,

those which orbit the Sun every 20 to 200 years.

The scattered disc region

is thought to be the primary source

of the short-period comets.

They are kicked into the inner solar system

either by interacting with Neptune

or possibly passing stars.

Narrator: Our spacecraft witnesses

Neptune's gravitational influence at work,

dislodging a comet out of the scattered disc.

This comet would be too dangerous to land on,

so we'll track alongside it

on its transformational flight through our solar system.

- So what would happen if it was on a journey toward the Sun?

Well, it would start off looking like a dark asteroid.

Nothing much is happening.

It doesn't have an atmosphere around it.

- As you start to travel toward the inner solar system,

get up to Jupiter or even closer to the Sun,

the comet would start to become active.

- The warmth from the Sun starts to heat up the comet,

and all the frozen material that's trapped on the inside

starts to convert from ice into gaseous material,

and so these gas jets can actually punch through

the crust of the comet and form jets.

As these jets flow away from the surface,

they can start to pull dust and rocks with them,

and this forms a kind of hazy atmosphere

around the comet's nucleus.

We call this the coma.

Narrator: As it zooms by Earth,

the coma of a comet can grow to be larger

than the diameter of our Sun.

Solar radiation eventually pushes this cosmic halo

behind the nucleus, forming two bright tails:

One of dust and the other of gas.

- There will be a tail growing and growing and growing,

and you would eventually become engulfed

in just a really rocky, icy, particle-filled environment.

It would be very difficult on your spacecraft

because it'd be like flying through a blizzard.

Narrator: Some tails can stretch for 100 million miles,

more than the distance between the Sun and the Earth,

as it travels towards our home star.

It's one of the most spectacular spectacles of our solar system.

- Today we're going to see what happens

when we take a comet

that's been in the cold, dark, icy outer reaches

of the solar system,

and we're going to send it inward towards its perihelion,

or the point of closest approach to the Sun.

Now, dry ice is frozen carbon dioxide,

and this is a very common constituent of comets.

Let's see what happens.

When we take this piece of dry ice,

and we drop it into the warm water,

the dry ice starts to sublimate.

That means it converts directly from a solid, frozen state

into a gaseous state.

And as the water starts to warm up

certain parts of the dry ice first,

you can start to see that little jets kind of form on it,

and this forms a hazy atmosphere called a coma.

You can see that the little chips of dry ice

are constantly changing as they sublimate away.

Sometimes they speed up.

Sometimes they slow down.

So if this was a comet,

you can get the idea that, as the comet approaches the Sun,

and the volatiles start to vaporize,

this can actually change the comet's rotational state

and even its orbit.

Narrator: Oomets are brightest and fastest

when they're closest to the Sun.

The searing heat and immense gravity of our mother star

can accelerate a comet's speed

to nearly 2 million miles per hour.

- The speed increases a lot, and it whips around the Sun,

so it goes zoom, like that,