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Cosmic Dawn & Cosmic Questions‏

COSMIC QUESTIONS

National Geographic

[To see the graphics and illustrations 
of this exposition on our Cosmos
go to the direction indicated above.  

The following text
is the transcript of that presentation.

In the 20th century the universe 
became a story—a scientific one. 

It had always been seen as static and eternal. 

Then astronomers observed 
other galaxies flying away from ours, 
and Einstein’s general relativity theory 
implied space itself was expanding
—which meant the universe 
had once been denser. 

What had seemed eternal now 
had a beginning and an end. 

But what beginning? 

What end? 

Those questions are still open.

HOW DID OUR UNIVERSE BEGIN?

Some 13.8 billion years ago 
our entire visible universe 
was contained in an 
unimaginably hot, dense point, 
a billionth the size of a nuclear particle. 

Since then it has expanded
—a lot—fighting gravity all the way.

INFLATION

In far less than a nanosecond 
a repulsive energy field inflates space 
to visible size and fills it with a soup 
of subatomic particles called quarks.

AGE: 10ˆ-32 MILLISECONDS
SIZE: INFINITESIMAL TO GOLF BALL

---

EARLY BUILDING BLOCKS

The universe expands, cools. 
Quarks clump into protons and neutrons, 
the building blocks of atomic nuclei. 
Perhaps dark matter forms.

AGE:    .01 MILLISECONDS
SIZE:  0.1-TRILLIONTH PRESENT SIZE

--

FIRST NUCLEI

As the universe continues to cool, 
the lightest nuclei, 
of hydrogen and helium, arise. 

A thick fog of particles blocks all light.


AGE:     .01 TO 200 SECONDS
SIZE:   1-BILLIONTH PRESENT SIZE

---

FIRST ATOMS, FIRST LIGHT

As electrons begin orbiting nuclei, creating atoms, 
the glow from our infant universe is unveiled. 
This light is as far back as our instruments can see.

AGE:    380,000 YEARS
SIZE:    .0009 PRESENT SIZE

--

THE “DARK AGES”

For 300 million years 
this cosmic background radiation 
is the only light. Clumps of matter 
that will become galaxies glow brightest.


AGE:   380,000 TO 300 MILLION YEARS
SIZE:    .0009 TO 0.1 PRESENT SIZE

___


GRAVITY WINS: FIRST STARS

Dense gas clouds collapse under their own gravity
—and that of dark matter—to eventually form galaxies and stars. 
Nuclear fusion lights up the stars.


AGE:   300 MILLION YEARS
SIZE:   0.1 PRESENT SIZE

--

ANTIGRAVITY WINS

After being slowed for billions of years by gravity, 
cosmic expansion accelerates again. 
The culprit: dark energy. Its nature: unclear.


AGE:  10 BILLION YEARS
SIZE:   .77 PRESENT SIZE


TODAY

The universe continues to expand, 
becoming ever less dense. As a result, 
fewer new stars and galaxies are forming.


AGE:     13.8 BILLION YEARS
SIZZE:  PRESENT SIZE


HOW WILL IT END?


Which will win in the end, gravity or antigravity? 

Is the density of matter enough for gravity 
to halt or even reverse cosmic expansion, 
leading to a big crunch? 

It seems unlikely—especially 
given the power of dark energy, 
a kind of antigravity. 

Perhaps the acceleration in expansion 
caused by dark energy will trigger a big rip 
that shreds everything, from galaxies to atoms. 

If not, the universe may expand 
for hundreds of billions of years, 
long after all stars have died.


WHAT IS OUR UNIVERSE MADE OF?

Stars, dust, and gas
—the stuff we can discern—
make up less than 5 percent of the universe. 

Their gravity can’t account 
for how galaxies hold together. 

Scientists figure about 
24 percent of the universe 
is a mysterious dark matter
—perhaps exotic particles 
formed right after inflation. 

The rest is dark energy: 
an unknown energy field 
or property of space 
that counteracts gravity, 
providing an explanation 
for observations that 
the expansion of space 
is accelerating.

The Universe

Dark energy 71.5%
Dark matter 24%
Gas 4%
Planets and stars 0.5%


WHAT IS THE SHAPE OF OUR UNIVERSE?

Einstein discovered 
that a star’s gravity 
curves space around it. 

But is the whole universe curved? 

Might space close up on itself 
like a sphere or curve the other way, 
opening out like a saddle? 

By studying 
cosmic background radiation, 
scientists have found 
that the universe 
is poised between the two: 
just dense enough 
with just enough gravity 
to be almost perfectly flat, 
at least the part we can see. 

What lies beyond we can’t know.


Observable Universe

The universe began 13.8 billion years ago. 

Because it has been expanding ever since, 
the farthest observable edge 
is now 47 billion light-years away.


The Unknown Beyond

What we can’t see. 

The possible shapes are:

Sphere    Saddle     Flat


DO WE LIVE IN A MULTIVERSE?

What came before the big bang? 

Maybe other big bangs. 

The uncertainty principle holds 
that even the vacuum of space 
has quantum energy fluctuations. 

Inflation theory says 
our universe exploded 
from such a fluctuation
—a random event that, odds are, 
had happened many times before. 

Our cosmos may be one
in a sea of others just like ours
—or nothing like ours. 

These other cosmos 
will very likely remain forever 
inaccessible to observation, 
their possibilities limited 
only by our imagination.

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