Cosmic Voyage

Things around us aren't always what they seem.

In the everyday world, we use a simple scale, ourselves ...

to know what's small and what's large.

But what about the worlds that lie beyond?

What is truly large and truly small?

To explore, to observe ...

to understand the wider world we call the universe:

This is one of the great human adventures.

As we look out at the distant horizon, we may ask ourselves ...

what is our true place in the universe?

We are all travellers ...

on an unending voyage of discovery.

More than 25 centuries ago, among the Greek Islands ...

here at the vibrant crossroads of Africa, Asia and Europe ...

philosophers devised rational theories about the world around them.

The wondrous waves and foams of nature, they said ...

could be understood.

One Greek thinker suggested that the Earth moved around the sun.

Another taught that everything, the work of man and nature ...

was made of particles too small to see.

Others estimated the sizes of the Earth and the moon ...

and the distances between them, and reasoned ...

both were spheres.

But it would be centuries before we had the tools to extend our vision ...

and confirm the wisdom of these early thinkers.

In the meantime ...

people around the world gazed on the stars and gave them names.

Most assumed the Earth was the centre of an unchanging universe.

Two thousand years passed ...

before a revolutionary breakthrough was made by a mathematics professor ...

in the ancient, maritime republic of Venice.

In 1609, Galileo Galilei ...

demonstrated an instrument that would soon be called a telescope.

From the tallest bell towers ...

he showed the device could spot approaching ships ...

hours before their sails were visible to the naked eye.

Later, when he aimed his telescope at the night sky ...

Galileo discovered that the moon was a world of mountains.

Jupiter had its own moons ...

and the Milky Way was a band of countless stars.

Our own cosmic voyage begins here ...

in the centre of Galileo's Venice, St. Mark's Square.

Since the universe is a big place, we could easily get lost ...

so we'll need signposts to give us a sense of scale.

The acrobats' ring is one meter wide.

The crowd is ten times wider, ten meters across.

Larger by one power of ten.

Now, with every step, every ring ...

we travel ten times farther from Venice ...

and our view of the universe is ten times wider.

The 100-meter ring surrounds St. Mark's ...

and 1,000 meters, one kilometre, the city's centre.

As our speed increases, four steps, four powers of ten ...

reveal all the islands of Venice, the Adriatic Sea and Northern Italy.

Six steps take in Europe from Germany across to the Balkans.

And soon, we can see the entire planet.

Our home in space.

Eight steps on our outward journey ...

eight powers of ten, and we pass the farthest reaches of human travel:

The moon.

If we visualize the paths that the nine planets take ...

in their orbits around the sun ...

at 13 steps from St. Mark's Square ...

the entire solar system comes into view.

And with 15 steps, 15 powers of ten ...

we can see our sun is just another star.

From here on, our voyage will be measured in light-years.

The distance light travels in an entire year.

Only now do we fly past our nearest neighbour stars ...

almost five light-years away.

The same journey at the speed of today's spacecraft ...

would last 100,000 years.

As we cross the perpetual night ...

our voyage takes us up and out of our sun's neighbourhood ...

near the edge of a great pinwheel of stars.

The Milky Way is actually a spiral galaxy ...

and our own sun is just one of a hundred billion stars in it.

At this immense scale, 23 powers of ten ...

each shining light we see is not a star ...

but an entire galaxy composed of countless stars.

Astronomers have discovered galaxies are flying away from one another.

The universe is expanding.

Our own galaxy, and all the others ...

form clusters and super-clusters of stupendous size ...

hundreds of millions of light-years across.

And here, about 15 billion light-years from Venice ...

we approach the outer limits of the visible universe.

What lies beyond this cosmic horizon, we cannot see ...

and do not know.

While Galileo's telescope allowed us to take an outward voyage ...

another innovation, here in the Dutch town of Delft ...

would lead us on an inward journey of discovery.

Over three centuries ago ...

Anton van Leeuwenhoek perfected the early microscope ...

and used it to study droplets from the waterways of Holland.

Come on, over here.

As students today make their own discoveries ...

imagine the moment when van Leeuwenhoek ...

peered through his more powerful instrument ...

and discovered a living kingdom in a drop of water.

This busy world of single-cell paramecia ...

is only one millimetre across.

Three powers of ten smaller than a meter.

The microscope allows us to continue our journey to the realm of the very small.

As we move into the cell nucleus ...

each new ring now reveals a world ...

ten times smaller in diameter than the last.

Deep within the nucleus ...

we come upon truly remarkable constructions.

Long, spiralling molecules of DNA.

DNA holds the chemical codes ...

for the reproduction of most organisms on the planet.

Whether they're paramecia, people or petunias.

Voyaging on, we see that molecules ...

are made of even smaller parts called atoms.

The tiny world of the common atom is very strange indeed.

Its six electrons seem to swarm everywhere at once.

Now our voyage takes us through a void ...

that appears as vast as the space between the stars.

Ahead lies the atomic nucleus.

So fantastically small ...

that if the whole atom were the size of this theatre ...

its nucleus would be like a speck of dust.

Yet the nucleus contains almost all of the atom's mass ...

packed into particles called protons ...

and neutrons.

And these, in turn, are made of smaller, more mysterious things called quarks.

Exploring this ...

the inner frontier of the universe ...

physicists wonder if quarks might contain ...

even tinier building blocks of matter.

Scientists are investigating this mystery in an underground tunnel near Chicago ...

home of the giant Fermilab particle accelerator ...

designed to create conditions like those after the birth of our universe.

Millions of protons and antiprotons ...

race through these pipes in opposite directions ...

nearly at the speed of light. A kind of sub-atomic demolition derby.