How far does it stretch? Where does it end... and what lies beyond its star fields... and

streams of galaxies extending as far as telescopes can see?

These questions are beginning to yield to a series of extraordinary new lines of investigation...

and technologies that are letting us to peer into the most distant realms of the cosmos...

But also at the behavior of matter and energy on the smallest of scales.

Remarkably, our growing understanding of this kingdom of the ultra-tiny, inside the nuclei

of atoms, permits us to glimpse the largest vistas of space and time.

In ancient times, most observers saw the stars as a sphere surrounding the earth, often the

home of deities.

The Greeks were the first to see celestial events as phenomena, subject to human investigation...

rather than the fickle whims of the Gods.

One sky-watcher, for example, suggested that meteors are made of materials found on Earth...

and might have even come from the Earth.

Those early astronomers built the foundations of modern science. But they would be shocked

to see the discoveries made by their counterparts today.

The stars and planets that once harbored the gods are now seen as infinitesimal parts of

a vast scaffolding of matter and energy extending far out into space.

Just how far... began to emerge in the 1920s.

Working at the huge new 100-inch Hooker Telescope on California's Mt. Wilson,

astronomer Edwin Hubble, along with his assistant named Milt Humason, analyzed the light of

fuzzy patches of sky... known then as nebulae.

They showed that these were actually distant galaxies far beyond our own.

Hubble and Humason discovered that most of them are moving away from us. The farther

out they looked, the faster they were receding.

This fact, now known as Hubble's law, suggests that there must have been a time when the

matter in all these galaxies was together in one place.

That time... when our universe sprung forth... has come to be called the Big Bang.

How large the cosmos has gotten since then depends on how long its been growing... and

its expansion rate.

Recent precision measurements gathered by the Hubble space telescope and other instruments

have brought a consensus...

That the universe dates back 13.7 billion years.

Its radius, then, is the distance a beam of light would have traveled in that time ...

13.7 billion light years.

That works out to about 1.3 quadrillion kilometers.

In fact, it's even bigger.... Much bigger. How it got so large, so fast, was until recently

a deep mystery.

That the universe could expand had been predicted back in 1917 by Albert Einstein, except that

Einstein himself didn't believe it...

until he saw Hubble and Humason's evidence.

Einstein's general theory of relativity suggested that galaxies could be moving apart because

space itself is expanding.

So when a photon gets blasted out from a distant star, it moves through a cosmic landscape

that is getting larger and larger, increasing the distance it must travel to reach us.

In 1995, the orbiting telescope named for Edwin Hubble began to take the measure of

the universe... by looking for the most distant galaxies it could see.

Taking the expansion of the universe into account, the space telescope found galaxies

that are now almost 46 billion light years away from us in each direction... and almost

92 billion light years from each other.

And that would be the whole universe... according to a straightforward model of the big bang.

But remarkably, that might be a mere speck within the universe as a whole, according

to a dramatic new theory that describes the origins of the cosmos.

It's based on the discovery that energy is constantly welling up from the vacuum of space

in the form of particles of opposite charge... matter and anti-matter.

Back in the 1980s, the physicist Alan Guth proposed that energy fields embedded in the

vacuum of space suddenly tipped into a higher energy state...

causing space and time to literally "inflate"...

...to go from atomic size... to cosmological size within an infinitesimally short time.

As a result, according to one calculation, the universe as a whole...

...would have grown to some ten billion trillion times the size of the observable universe.

That's ten followed by 24 zeroes.

Put another way, the complete universe is to the observable universe... as the observable

universe is... to an atom.

The fury of this period of cosmic inflation helps explain the immense size and smoothness

of the universe.

But to succeed, the theory must also account for how the universe produced what we see

around us... all those stars and galaxies and clusters of galaxies, and ultimately...

us.

Scientists are now seeking to piece together the chain of events that launched our universe

in its earliest moments... by generating what you might call a "little bang."

At the Brookhaven National Lab in New York State, they are blasting gold atoms in opposite

directions down tunnels almost two and a half miles long.

When these atoms reach velocities just short of the speed of light, they are sent into

a violent collision.

A fireball erupts... reaching a temperature exceeding two trillion degrees Centigrade.

As far as we know, the last time anything in our universe was that hot was about a millionth

of a second after its birth.

What interests the scientists is the splatter of subatomic particles... a super-hot soup

of quarks and gluons... particles that gave rise to matter as we know it.

In initial tests, this quark-gluon plasma has shown a crucial property... extremely

low viscosity or resistance to flow. Scientists call this a perfect liquid.

To grasp its importance, we go back to those primordial energy fields that the theory says

spawned the big bang.

The thinking is that those fields contained tiny fluctuations that were blown up to huge

size during inflation.

In the ultra-dense quark-gluon mix, these fluctuations generated pressure waves, or

ripples. As the universe evolved, these ripples led to variations in the density of matter.

Amazingly, the imprint of those primordial ripples is out there today... first seen in

a faint signal discovered accidentally back in the 1960s.

Working for the Bell Telephone Company, physicists Arno Penzias and Robert Wilson had built a

giant horn-shaped antenna.

But wherever they pointed, the contraption picked up excessive noise in the microwave

portion of the electromagnetic spectrum.

That noise turned out to match a prediction made years earlier...

That in the wake of the big bang, the universe was filled with a cloud of extremely hot gas

that scattered all light.

As the universe cooled, the cloud dissipated. Light then shone through.

Over time it shifted... as the universe expanded and cooled... to just the noise signature

detected by Penzias and Wilson. What they'd heard was the echo of the Big Bang.

This image shows the smooth contours of the light recorded by the Bell team. Scientists

would have to look closer... to find the imprint of cosmic inflation.

The Space Shuttle Discovery lifted the Hubble Space Telescope into orbit on April 24, 1990...

in one of the most important scientific milestones our time.

Another launch, arguably just as important, took place five months earlier.

This was the Cosmic Observation Background Explorer, COBE for short, was sent up to take

a harder look at the microwave radiation discovered by Penzias and Wilson.

The results came out two and a half years later. The early universe contained a pattern

of hot and cold spots.

One COBE scientist called it the fingerprint of creation... for it showed the origin of

the universe we see around us today... smooth on a large scale, but with significant clumps...

...from which gravity would form gas clouds, then stars, and galaxies.

With this cosmic template in hand, astronomers set out to discover how the patterns and the

dimensions of the universe evolved over time.

In an age of computer controlled telescopes and automated observing, astronomers could

now launch huge international collaborations with the goal of mapping a large fraction

of the universe in three dimensions.

At Apache Point in New Mexico, the Sloan Digital Sky Survey set the standard for mass production

astronomy.

A series of steel plates are drilled with holes that exactly match the location of galaxies

in the night sky.

After plugging fiber optic sensors into the holes, the plates capture the light of hundreds

of galaxies per night, and that light determines their distances from Earth.

Another survey is named the 2 Micron All Sky Survey, or 2Mass, after the frequency of infrared

light its detectors are tuned to capture.

Here, these data go out to a region 60 million light years across. You can see the local

group of galaxies, dominated by Andromeda and the Milky Way in the center. This is our

neighborhood.

Jump further out to a region about 200 million light years across.

Our galactic neighborhood merges into the densely packed Virgo Supercluster... which

is the nearest intergalactic city.

Stepping out to a region over 320 million light years across, you can see the full breadth

of our local region of the universe.

Galaxies line up in walls and arcs... that bound an array of sparsely-populated voids...

the rural cosmic countryside.

Moving out with the data... this region is over 650 million light years across...

Then almost two billion...

3.2 billion...

And finally out to a region 6.5 billion light years from end to end: the cosmic continent.

In the middle of it all, our galaxy, so immense from our Earthly perspective, is less than

a speck.

The 2mass study, the Sloan Digital Sky Survey, and the 2 Degree Field in Australia have extended

our maps to a quarter of the way back to the beginning of the universe.

They have laid out a grand cosmic roadmap... and gravitational routes.

Now COBE's successor, the Wilkinson Microwave Anisotropy Probe, or "WMAP", was ready to

scan the early universe for the fine-scale origins of this cosmic atlas.

WMAP was launched beyond any interference from Earth... to a position balanced between

the Earth and the Sun.

There, for two years, its detectors took in the pristine light of deep space.

This is what WMAP saw... a pattern consistent with the filaments and voids that had evolved

in the universe at large... and with the tiny-scale structures sketched by inflation at the very

birth of the cosmos.

Scientists at Brookhaven National Lab in the U.S. and the new Large Hadron Collider in

Europe will be probing ultra high-energy collisions in the coming years to tease out more details

of the early universe.

Others are poring over the WMAP data for evidence of its true dimensions.

One group looked for repeating patterns that could be evidence of pressure waves that might

have ricocheted through the hot gas of early times.

They saw none...which implies that the universe had grown so large during inflation that such

waves could not cross it.

Then they did the math... the entire universe has a minimum diameter of 156 billion light

years... not quite twice the size of everything out there that we can see: the "observable"

universe.

What is its maximum size... and what's beyond that?

We will never know for sure what lies beyond our visual horizon... but astronomers are

turning up some surprising hints... in the universe they can see.

To ancient observers, the universe was made of five classical elements... Earth, Water,

Air, Fire...

and a fifth: Quintessence... or space.

Aristotle believed the stars, unchanging and incorruptible, were made of this fifth element.

Today, we are finding that space, in fact, has a character of its own.

Astronomers have calculated the gravitational pull needed to bind stars as they orbit a

galaxy... or galaxies as they orbit a cluster of galaxies.

They have found that there is simply nowhere near enough visible matter there to hold these

structures together.

The missing ingredient, its identity still unknown, they call: Dark Matter.

In supercomputer simulations of cosmic evolution, dark matter is added in to supply the gravitational

tug needed to form the web pattern of filaments and walls;

voids and dense clusters we see in the universe at large.

But something else appears to be happening on these large scales.

Astronomers have been making refined measurements of the cosmic expansion rate with a new type

of distance marker.

They wanted to know if gravity was slowing down the pace at which the universe is spreading

out.

But what they've found comes as a shock:

The markers they use, type IA supernovae, are thought to burn at uniform intensities

throughout the universe.

By measuring changes in the brightness of these so-called standard candles at various

distances, the researchers have been hunting for changes in the rate at which the Cosmos

is expanding.

They have shown that while local regions or the universe are drawing together, the universe

as a whole is not only expanding, it's accelerating outward!

The culprit is thought to be energy welling up from the vacuum of space... similar to

what occurred in the early moments of the Big Bang, causing cosmic inflation.

Now it's happening in minute quantities across vast regions.

Over time, this so-called "Dark Energy" has grown to an astonishing three-fourths of all

the matter and energy in the universe.

With data like this pointing to an underlying dynamic within our universe, some scientists

have suggested its part of an even larger cosmic dynamic... much broader and deeper

than we've ever thought.