100 Greatest Discoveries (2004) - full transcript

For most of human history, the
only light we knew came from the sky.

By day, the Sun.
By night, an uncountable number of stars.

From the beginning, our ancestors believed that
the Sun and stars were heavenly, out of this world.

And they were right.

We have been watching the
stars for thousands of years.

But until recently, we couldn't see well enough
to understand our connection to the cosmos.

But now, our astronomical
vision has sharpened.

We can see farther and clearer. We can observe
objects that are invisible to human eyes.

Our increasingly improving vision has
allowed us to make great discoveries.

Revealing an astonishing
and wonderful universe.

What follows are 13 of the greatest
discoveries in astronomy.



The Planets Move.

Our first great discovery
happened over centuries.

As the first humans looked
carefully at sky in places like this.

The empty cloudless deserts of the American
southwest, the Middle East, Africa, and South America.

Of these ancient astronomers,
the most important were the Mesopotamians.

They considered the objects in the sky gods.

And built giant towers so they could record the rising
and setting of the Sun, the moon, and the stars.

For more than a thousand years, they
used clay tablets to record what they saw.

To find out more, I paid a visit to
professor of astronomy Owen Gingerich.

Here for example, is one of
these clay tablets. Uh, have a read.

Yeah, uh, these guys,
these people wrote small.

Yes.

Yes, I was perfectly amazed when somebody came into my
office, picked it up and actually started reading it.

So what language is this...



I think this is in Babylonian.

Hundreds of these tablets were unburied.

Among these hundreds of tablets is a tablet
called the Venus tablet of Ammisaduqa.

And this tablet contains the
motion of the planet Venus.

That's the earliest record
we have of a planet moving.

After the Mesopotamians made the first records,
it was the Greeks who took the next step.

Some of the Greek astronomers made a field trip out to
Mesopotamia to find out what had been going on there.

And they seemed to brought
back some systematic records.

So, it ultimately gave the basis for making a
mathematical theory of the motion of the planets.

From their observations...

the Greeks developed the vision of the
solar system that would stand for some 2000 years.

That the planets moved,
revolving around the earth.

It would take our next great discovery
to set the record straight.

The Earth Moves.

The year is 1543.

A seventy-year-old man is dying.
His name Nicolaus Copernicus.

A doctor and a lawyer by trade, but for
nearly 40 years he was also an amateur astronomer.

A pursuit that had let him to challenge one of the
most fundamental and sacred beliefs of his time.

As a young man,
Copernicus had studied the heavens...

and found that the Greek's earth centered system
failed when it came to predicting planetary motion.

He began to wonder if
the earth itself moved.

But, here is Copernicus' idea.

- With the Sun at the center.
- With the Sun at the center.

And now suddenly, all the planets are going
always the same way around they're not stopping.

Copernicus realized that the movements of the planets were
better explained if the Sun were at the center of the solar system.

And the earth circled it
like an ordinary planet.

It was a revolutionary insight.

Despite any evidence that the earth was moving, he
came up with this book, which gives his new theory.

This idea, this book changed the world.

Yes, because it made the earth a planet and it fixed the Sun in the center. If you don't
have that blueprint you don't march ahead to the physics, the physics of the cosmos.

As it happened, the final pages...

which were just these here in the front of
the book came to him on the very day he died.

I suspect, I mean, he was lying there partially paralyzed from a stroke he was
probably just hanging in there until he could make it sure that it was done.

Planetary Orbits are Elliptical.

Everyone from the Greeks to Copernicus assumed
the orbits of the planet had to be circular.

But in 1571, German mathematician Johannes Kepler
shattered that assumption with our next great discovery.

Lacking calculus, Kepler improvised ways to
compute the circular orbit of mars.

The work was tedious.

Kepler wrote that he was almost driven to
madness considering in calculating the matter.

His calculations began to reveal that the accepted
notion of planet moving in circles simply did not work.

Then a new idea came to him.

Kepler realized somehow the Sun had to be driving
the planet in some way he didn't fully understand.

And to get a self-consistent picture, he found
that an ellipse was the path rather than a circle.

With this breakthrough, Kepler devised the first method for accurately
predicting the movement of the planets and stars across the sky.

When his tables predicted the planet
Mercury to pass across the front of the Sun.

And nobody else's tables were close..

That was dramatic proof of
the accuracy of his astronomy.

It linked the motions of the planets solidly to the Sun This was a very important point to
helps stress the idea that the Copernicus's Sun-centered system really had physical significance.

Despite the success of Kepler's theory, many remained skeptical
that the Sun could be the center of the Solar System.

But the final nail in that coffin was about to be driven home by a man who
like Kepler preferred to use observational evidence to form his theories.

And that man was Galileo Galilei.

Jupiter has Moons.

Meet Galileo Galilei, a man determined
to pursue truth no matter where it led.

In the case of our next great discovery, his determination
led him to revolutionize our knowledge of the solar system.

The year is 1609 and Galileo was fascinated
with the new invention called a telescope.

Essentially, that was a toy out of a carnival. When
Galileo heard about it, he went to work, making one.

He perfected it and essentially converted
the toy into a scientific instrument.

Galileo turned his telescope skyward...

and was the first to see
the mountains on the moon.

And the star clusters of the Milky Way.

Then an extraordinary sight.

A group of 4 small bright stars
arranged around the planet Jupiter.

We have the manuscript of
his first week of observations.

And it was wonderful because you see
him gradually coming to the conclusion.

That these little stars are
carried along with Jupiter.

This was the moment of discovery.

Galileo realized that the stars were
actually four moons orbiting Jupiter.

He had the insight that these
moving dots were orbiting a planet.

And I sometime say he invented the satellite, And you say,
wait a minute, they were there, how could he even invent them.

He invented the idea that they
were going around the planet.

Here was proof that Copernicus was
right about the structure of the solar system.

If moons could orbit Jupiter,
then the earth could orbit the Sun.

And Galileo's discovery demonstrated that knowledge in
astronomy can only be advanced by actual observation.

A theory can only be viable
when it's supported by the facts.

Just like our next great discovery.

Halley's Comet.

For centuries, comets had been
considered harbingers of evil.

By the end of the middle ages, a comets
appearance invoked fear and terror.

But the renaissance scientist Edmond Halley, like
Galileo was interested in facts, not superstition.

In 1695, he began searching for records
of ancient and recent comet sightings.

He found 24 comets whose passage across the sky had been recorded
with enough detail to allow him to roughly plot their orbits.

To his surprise, he found that three of the
comets seem to follow the same approximate orbit.

Circling the Sun every 76 years.

On that basis, he figured, ok, this is a comet
that is going to be back in another 76 years.

- He figured out the three comets were actually the same comet.
- The same comet.

Halley was so certain of the comets
orbit that he made a bold prediction.

He said the comet
would return in the year 1758.

- And guess what.
- It was. The comet came back.

Unfortunately, Halley was no
longer alive to savor his discovery.

Since then, Halley's Comet, as it's known, has been greeted
3 more times by excited sky watchers across the globe.

No longer a harbinger of evil, Halley's Comet
became a milestone discovery in the history of astronomy.

Replacing a superstitious belief with the rational
scientific understanding of the physical universe.

Milky Way a Disk of Stars.

In the eighteenth century, William Herschel
was a classically trained musician...

whose love of astronomy led him to give up
music and turn his attention to the heavens.

Thus setting stage for
our next great discovery.

When he discovered the price of a refracting telescope,
which was beyond his means, he decided to make his own.

And he became the most fabulous and
successful telescope builder of that period.

He used his telescope to methodically
survey the sky, cataloging what he saw.

As he was searching the sky, he came across an object that
looked a little bit different, turned out to be a new planet.

Oh, wow, and what planet was that.

That was the next planet
beyond Saturn. The planet Uranus.

Uranus was the first new planet to
be identified in more than 3500 years.

But finding a new planet was nothing
compared to Herschel's larger goal.

He built a powerful twenty foot telescope...

then divided the sky into equal sections, and
began to systematically count the stars in each field.

It was a painstaking, monumental task.

Slowly, Herschel's star count began
to reveal something extraordinary.

The Milky Way was much
larger than anyone knew.

It was a gigantic disk of stars.

Some of its fields were jam-packed. One showed
more than a quarter of a million stars alone.

Other fields, farther away,
were practically empty.

Herschel's discovery was a revelation.

This is a reasonable model of
the Milky Way as we know it now.

But Herschel was only work at an area about this big, is that right -
What Herschel was seeing, was a small range like this, maybe that big.

So it was really a small
part of the entire milky way.

But even that small part significantly
changed the study of astronomy.

Herschel's discovery revealed that our solar system
was just an island in a deep and expansive universe.

General Relativity.

Thanks to the musings of an obscure clerk working in the Swiss patent office, our
next great discovery revealed that the universe is a strange, mysterious place.

That clerk was Albert Einstein.

In the early 19 hundreds, he was puzzled,
along with the rest of the scientific community...

by the orbit of the planet Mercury.

Despite the ability of Newton's laws of gravity to precisely predict the motion of
the planets, the laws failed when it came to correctly predicting Mercury's orbit.

The puzzle had to do
with Mercury's perihelion...

that point in its orbit
where is closest to the Sun.

Every century Mercury's
perihelion advanced slightly.

A change that Newton's
equations could not account for.

In a bold and startling move, young Einstein proposed
his own theory to explain the puzzle of Mercury's orbit...

and in the process developed a theory
that refined Newton's law of gravity.

Michio Kaku is the theoretical physicist
at the City University of New York.

And Newton says that gravity travels
instantaneously throughout space.

And that's why Einstein thought there
was a weakness in Newton's theory.

He wanted a theory that could explain gravity; he wanted a
theory that could explain acceleration, zigzag and circular motion.

There has to be waves, gravity waves. It
takes time for gravity to work its magic.

- To propagate.
- To propagate.

So if the Sun disappears, it will take 8 minutes for us to know
about that fact even gravity travels at the speed of light.

Einstein needed a new picture to explain that and that picture was
curved space that space itself has curved. And that's why objects move.

Einstein believed that his concept of curved space
was responsible for shifting mercury's orbit.

Einstein called his idea the
theory of general relativity.

Imagine a trampoline net and place a bowling
ball in the middle of the trampoline net.

The bowling sinks into the trampoline net.

And now shoot a marble, a marble around the trampoline
net. The marble will orbit, orbit around the bowling ball.

Now, from a distance looking down, Newton would say that there is a force an
instantaneous invisible force pulling the marble down to the bowling ball.

But Einstein would say there's no force,
there's no pull it's just a trampoline net.

And why is the marble orbiting around the bowling
ball Because the trampoline net is pushing the marble.

Therefore why I am sitting on this chair. Not because gravity pulls you
to the ground. it's because space pushes me down toward the planet Earth.

The idea that space itself was warped by
mass was too strange for many to accept.

An approaching solar eclipse gave scientists the perfect
opportunity to put Einstein's new theory to the test.

Photographs were taken of the background
stars before the eclipse and then afterward.

These pictures were then compared
with the photos taken during the eclipse.

The photo show that the positions of the stars in the eclipse photo shifted slightly
inward, bending is the lights from the stars passed the Sun's gravitational field.

Einstein's theory of
general relativity was right.

His great discovery rocked the world.

General relativity strikes deep emotional chord
in anyone who's ever looked at these equations.

These equations are one inch long and they
answer these eternal questions that dogged us...

ever since we first looked into the night sky and
asked ourselves the question what's it all mean.

The Universe is expanding.

General relativity had shown that space was weirder
than anyone could imagine, anyone but Einstein that is.

To gain a clearer understanding of this strange
universe, astronomers needed more observational data.

And that required larger
more powerful telescopes.

Like the one that led to
our next great discovery.

When the Herschel's had finished
their survey of heavens in the 1830s.

They had cataloged thousands of these beautiful
but hazy objects then called white nebulae.

At the time, no one knew
whether they were part of our galaxy...

or distant island universes
like the Milky Way.

In 1924, astronomer Edwin Hubble was studying the stars in several of these nebulae
using a 100-inch reflected telescope at the Mount Wilson Observatory in California.

The telescope enabled Hubble to estimate that the galaxies were routinely
many hundreds of thousands, even millions of light years away.

Here were objects as huge and populated with stars as our very own
Milky Way galaxy, which is why we today call white nebulae galaxies.

The more Hubble studied these
galaxies, the more he became intrigued.

At the time, scientists knew that a beam of light
from a star appears as a different color on the spectrum.

The color changed according
to the motion of the star.

A shift toward blue end of the spectrum meant
the star was moving closer to the earth.

A red shift meant it was moving away.

The amount of the color shift also
revealed the speed of that movement.

Hubble found when he measured the distance of a galaxy,
its spectrum almost always was shifting to the red.

And something else, the farther
the distance, the greater the red shift.

In other words, the universe was expanding.

It was an astonishing discovery
with profound implications.

Measuring backwards from the expansion, scientists found that the universe appeared
to have a cataclysmic beginning where one of the astronomers labeled the big bang.

Milky Way Emits Radio Waves.

Just three years after Hubble discovered
the expanding universe...

our next great discovery revealed a mysterious object
hidden behind the dust at the center of the Milky Way.

And gave birth to a whole new branch of astronomy,
using wave lengths invisible to the human eye.

In 1930, Karl Jansky was a 25-year-old physicist working
for the bell laboratories in Holmdel, New Jersey.

Jansky's job was to identify the kinds of interference occurring at the 15
meter wave length then used for ship-to-shore and transatlantic communication.

After spending more than a year recording data, Jansky
decided there were three forms of static at this frequency.

The first was clearly produced
in the earth's ionosphere.

The second was caused
by local thunderstorms.

And the third signal was
mysterious, continuous.

It was coming from what
appeared first to be, the Sun.

Each morning, this signal
slowly rose with the Sun.

During the day, it rotated across the sky.

And then it set when the Sun did.

But as time passed, Jansky found that the mysterious
radio signals slowly drifted away from the Sun...

as if it were coming from a
point outside the solar system.

Eventually, Jansky pinpointed this location somewhere
in the region of the constellation Sagittarius.

He believed he had discovered an unknown
interstellar object at the center of the galaxy.

And he was right.

Later astronomers confirmed that Jansky
had discovered a super massive black hole.

Equal in mass to three million Suns.

Perhaps even more significant, he was the first
human to look at the universe using radio astronomy.

A whole new way to study the sky.

It was a landmark discovery.

Jansky has proved that the sky does not merely
sparkle with the gentle glow of star light.

Hidden out there are many strange objects, many light years
away that actually radiate more energy than whole galaxies.

Like quasars and pulsars, dead stars spinning madly with masses
that are so dense that single teaspoon would weigh millions of tons.

Before astronomers could even begin to
understand the life and death of stars.

New telescopes would have to be built that could
look at the sky in many different wave lengths.

Before that could happened though, radio astronomy produced another great discovery,
that, although predicted, was as unexpected by its discoverer as Jansky's has been.

And once again, it happened in
bell lab in Holmdel new jersey.

Cosmic Microwave Background Radiation.

In 1964, bell labs had this spare
20-foot-microwave antenna sitting dormant.

Rather than destroy it, the lab decided
to let the astronomers use it for research.

Two physicists, 31-year-old Arno Penzias and 28-year-old Robert Wilson decided to use the
antenna for measuring the temperature of the gas halo surrounding the Milky Way galaxy.

What happened next is one of the most
exciting discoveries in modern astronomy.

- Hello bill.
- Doc. Wilson.

And I came to bell labs to get the story
first-hand from Robert Wilson himself.

Two of us, Arno Penzias and I, had
just come to bell lab from graduate school.

And we were going to measure
radiation from the Milky Way.

And that's where this antenna really fit in because
we could reject the radiation from the earth.

And what was left is
what's coming from the sky.

We're only getting about two
degrees from the earth's atmosphere.

Maybe pick up one degree
from the walls of this thing.

But, when we first turned it on, it was
about twice that about seven degrees.

And this wasn't right. Something from
the earth must be in our instrumentation.

We of course are on a hill here and overlooked New
York City. We had the ideal instrument for checking on that though...

We merely turned down the horizon, scanned
the horizon and lo and behold, nothing particular extra.

There was a pair of pigeon that lived here, and of
course it was covered with light pigeon droppings.

So, we thought well, maybe the pigeon
droppings are doing more than we think.

Arno and I got up in here and we
cleaned all the pigeon droppings out.

- You got to get rid of pigeons.
- What had you do with pigeons.

Fist, we put them in the company mail and sent them as far as we could which was Whippany,
New Jersey, to a pigeon fans there who said these are junk pigeons and let them go.

- A couple of days they were back.
- 40 miles away and they came back.

So then our technician
brought out a shot gun.

And how did that work...

I wasn't here and I didn't see. But
basically it didn't solve our problem.

We still had an extra
three or four degrees.

We were really beginning to be perplexed. Because we
believed in physics, it's coming from somewhere.

We can calculate what the horn
was doing except for this excess noise.

At the time that Penzias and Wilson detected the radio static
there were two competing theories about the origin of the universe.

There was the big bang theory which
Hubble's expanding universe supported.

And there was the steady state theory, which proposed that
universe is timeless with no beginning or end, expanding forever.

When a friend heard what
Penzias and Wilson had found...

he suggested they get in touch with some cosmologists at
Princeton University who were advocates of the big bang theory.

They believed that the big bang would have left a faint thermal afterglow in the
universe, traces of heat from the roar of the bang itself, detectable across the entire sky.

And they were about to conduct research
in hopes of measuring that afterglow.

We invited them over. They came over and looked at what we had done and
immediately agreed that we had measured what they were setting out to do.

So what does your discovery mean.

It means that we live
in a big bang universe.

And we are seeing the radiation from three
hundred thousand years after the big bang.

Many cases when there is a paradigm shift of science,
it takes a generation before people really accept it.

But in this case, I think
the world was ready for it.

Human societies have always
worried about where they came from.

There are religious stories in every civilization that has
ever been found. And I think we have the definitive answer...

that we came out of a big bang.

Gamma Ray Bursts.

The coming of the space age ushered in a golden
age of astronomy that is still going on today.

That golden age began strangely enough, not in space,
but was the turning point in cold war relations.

That also contributed to
our next great discovery.

In the nineteen sixties, despite a nuclear-test-ban-treaty The Soviet
Union refused to allowed on-site inspectors at its nuclear facilities.

As a result, the US opted to monitor the soviets by developing an orbital satellite
system capable of detecting gamma rays burst produced by nuclear explosions.

Because the satellites detectors
looked up as well as down.

Scientists decided to use them to see if
supernovae produced gamma rays when they exploded.

Between 1969 and 1972, they detected evidence of 16 short gamma
ray bursts, scattering across the sky. There was just one problem.

None of the burst correlated with
any of the known supernova events.

And the mystery deepened.

Over the next two decades, astronomers detected
an average of one gamma ray burst a day.

But each burst happened so quickly that it was over
before astronomers could get a telescope aimed at it.

Finally, astronomers began to solve the puzzle with the help of
the BeppoSAX space telescope, which was designed specifically...

to detect the short burst of gamma and X-rays
and precisely pinpoint their locations.

On December fourteenth 1997, BeppoSAX located a gamma ray burst, leading to
the first photographs ever taken of a burst in wave lengths other than gamma.

To their astonishment, astronomers discovered that burst
took place in a galaxy twelve billion light years away.

Making it one of the universes
most powerful explosions.

Since then, dozens of other gamma rays bursts have been
similarly documented. All just as powerful and far away.

As for what it all means the discovery of gamma ray burst have once again show
us that hidden out there behind the veil of the earth's atmosphere are objects...

that are not only strange and hard to fathom, black
holes, pulsars, quasars. But they're lethal too.

Gamma ray bursts are now considered the possible
cause of past extinction events on earth.

The scientist sir Arthur
Eddington once noted that.

Not only is the universe stranger than we
imagine. It is stranger than we can imagine.

He could be talking about the gamma ray burst, the
expanding universe or the theory of general relativity.

And it also happened to be a perfect
description of our next discovery.

Planets Orbiting Other Stars.

Once it would been been impossible for astronomers to imagine
discovering other solar systems with planets like our own.

But today, astronomers can imagine thanks to powerful space and ground-based telescopes
like the one here in the Lick Observatory in the Mount Hamilton California...

where Geoff Marcy is
hunting for new planets.

How do you go about finding
a planet around a star.

Well, it's very easy. We watch the star to see if it wobbles
in response to the planet, yanking on it gravitationally.

- Very easy.
- Very easy...

- you just need one of these.
- That's right. This is the 3-meter lick observatory telescope.

By definition, planets don't produce their own energy, they shine of course by the
reflected light. But planet are about a billionth as bright as their host star.

So you can't really see them even with the Hubble you
need a trick and that is what we use with this telescope.

The Doppler effect is our trick. We measure the wobble of the star
by the changing light waves that come from the star as the star wobbles.

The search for extra-terrestrial planetary systems
gained momentum in the early nineteen nineties.

When a polish astronomer
made a surprising discovery.

There was a wonderful discovery by Alex Wolszczan of a system of three planets orbiting a
pulsar and the way he found them was quiet exciting. He watched the pulses coming from the pulsar.

And the arrival of those pulses changes
as the pulsars approaches and recedes us.

These are hideous stars. Pulsars have ultraviolet x-rays and gamma rays
coming off them. They are the bizarre end products of a supernova explosion.

And despite that bizarre environment, here
we have earth-size planets going around it.

If there are earth-size planet go around pulsars you can
bet there are earth-size planets around other stars.

There are earth-size
planets around pulsars.

Earth-size and even
moon-sized among the three.

- He detected them.
- Detected them by this wobble of the pulsars.

- That's just the coolest thing in the world.
- it's unbelievable.

Since Wolszczan's discovery Marcy and other astronomers
have found more than one hundred thirty extra-solar planets.

We thought we would never find even one planet and we found the world's
only triple planet system and quadruple planet system with this telescope.

So, these are big planets though - These are planets the
size of our Jupiter, Saturn and smallest Neptune sized.

Oh, little Neptune - So it's quite exciting that they are finding planets
of Jupiter sized. But even those a few times bigger than the earth.

While, no Earth-like planets have
yet been found. The search continues.

How do you pick a star as a candidate.

We indeed try to choose stars that are more or less like our Sun some more
massive some less massive, or sort of middle age or older so they've settled down.

What you want for an earth like planet to make it habitable is that temperature
has to be just right. Not so cold, the water's locked up in the ice.

Not so hot, that the water's evaporated into steam.

But a planet just the right distance from its star so that the temperature is just
right for liquid water over billions of years to let Darwinian evolution do its thing.

- Sound like Goldilocks and her porridge.
- That's right. You don't want it to be too hot or too cold.

Suppose you have a telescope, a gizmo, a device,
sensitive enough to find an earth-like planet.

Would you point at some of the stars you
already identified as having planets.

Absolutely, the Jupiters and Saturns we are finding are the
signposts the benchmarks of system that might harbor earths...

and especially if there's a Jupiter far enough from the host star. That
leaves room for an earth in the habitable zone to be orbiting that star.

What made you go looking
for planets on other stars.

Oh, I remember when I was a young kid, I thought to
myself, I wonder if there are other earths out there...

and if so of any are habitable and then is there life
on those planets, and in particular intelligent life.

We humans I think in general would
love to know are we alone in the universe.

Are there other planets like earth?
Habitable planets?

Are there other creatures out there that think
and dream and indeed are searching for us.

In the end, I think we humans are trying to find our
roots out there chemically and biologically among the stars.

The Universe is Accelerating.

As the universe expanded following the big bang logic dictated that the gravitational
attraction of all matter should pull at that expanding material and cause the expansion to slow.

But how much was the universe slowing down.

In the nineteen nineties, the Hubble space telescope
made it possible for teams of scientists to answer the question...

by studying the brightness of light from a special
type of exploding star called a type 1A supernova.

I paid a visit to the Lawrence Berkeley
National Laboratory in San Francisco.

And met with astrophysicist Saul Perlmutter
who headed up the supernova cosmology project.

So, what did you find out.

So, we started to make a measurement to try to find how
much the universe in its sustention is slowing down.

When we first saw the data, You say well, that's
kind of funny, looks the universe isn't slowing down.

But we're also in the midst of doing all these checks, and calculations
and confirmations I'm sure once we get all the numbers, you'll check out and figure out...

- that the effect will go away and change the signs somewhere that will fix.
- There are minus signs. Signs are like that.

You check each step of the process. Little by little you get the point
we start you know this effect isn't going way. This is the right answer.

It really looks like the
universe is actually speeding up.

So, why is this so important.

This acceleration of the universe doesn't fit at all.

We understand, pretty well the all forces of our universe and...all the objects of our universe..

and this is the first time we come cross
something that we wouldn't have predicted.

Now, we are having the fun to try to figure out what does this all
mean, And if you come with me, I will show you what we are doing about it.

Why is it accelerating.

Oh, that's the question, we are all dying to know the answer, and when we think
about this if you have a energy of this odd sort that would pervade all space.

It can actually speed up the universe
when gravity is trying to slow it down.

And we are calling it dark energy, just
reflecting the fact we don't know what it is.

it's a mystery; - it's completely
mysterious, bizarre We've no idea what it is.

We wanted studies to figure
out what could dark energy be like.

We want to do now is get data that could
help pull apart the different answers.

So, where are you going to get that data.

The big picture goal that we're after is a project that
you see you around you here which is a satellite project.

The design here we called SNAP which
is short for supernova acceleration probe.

This would be a new space telescope with a very very
big field of view.

So instead of looking through a little key hole of the universe, you'll be
looking through a big picture window of the universe.

So let me show you what we are working on that we think might help us get
at why the universe is accelerating, what this dark energy really is.

Here we have SNAP that we are
hoping to be launched just in the future.

This one goes out to a
location out past the moon.

From that vantage point, you can measure
the expansion history with such detail that...

we could actually see the little changes
when it goes to deceleration to acceleration.

Back when the universe was really dense and close together
Gravity is more important, it slows the expansion down.

As it is kept expanding though even it went slower it lossed out and gravity became
less important than the dark energy which took over and started to accelerate expansion...

And we are after exactly how that change-over occurred that would tell us about
what different possible theories could be right to explain dark energy.

- Always expanding, always speeding up.
- Exactly.

It's an issue of did it slow
down then suddenly bird...

or did it slow down and come
to a wobble and then take off.

What was that transition like.

Just like the ancient astronomers modern scientists have
discovered something about the cosmos that we cannot yet explain.

It will up to observers and theorists to figure
out what's going on in our expanding universe.

For this, only new ideas
and better instruments.

No matter whether this mystery will be
solves soon or far in the future...

It could be certain of one thing. We will keep watching
the skies, to understand our place in the cosmos.

We will continue to explore,
understand and discover.