Start a journey through Cosmos

 CARL SAGAN: The cosmos is all there is or ever was, or ever will be.

A generation ago, the astronomer Carl Sagan stood here and launched hundreds of millions of us on a great adventure that the exploration of the universe revealed by science.

It's time to get going again.

We're about to begin a journey that will take us from the infinitesimal to the infinite, from the dawn of time to the distant future. We'll explore galaxies and suns and worlds, surf the gravity waves of space-time, encounter beings that live in fire and ice, explore the planets of stars that never die, and discover atoms as massive as suns and universes smaller than atoms.

Cosmos is also a story about us. It's the saga of how wandering bands of hunters and gatherers found their way to the stars. One adventure with many heroes.

To make this journey, we'll need imagination. But imagination alone is not enough because the reality of nature is far more wondrous than anything we can imagine. This adventure is made possible by generations of searchers strictly adhering to a simple set of rules..., test ideas by experiment and observation, build on those ideas that pass the test, reject the ones that fail, follow the evidence wherever it leads and question everything. Accept these terms, and the cosmos is yours.

Now come with me.

If we're going to be venturing out into the farthest reaches of the cosmos, we need to know our cosmic address, and Earth is the first line of that address. We're leaving the Earth, the only home we've ever known, for the farthest reaches of the cosmos.

Our nearest neighbour, the Moon, has no sky, no ocean, and no life. Just the scars of cosmic impacts.

Our star powers the wind and the waves and all the life on the surface of our world. The Sun holds all the worlds of the solar system in its gravitational embrace, starting with Mercury.

 

Cloud-covered Venus, where the runaway greenhouse effect has turned it into a kind of hell.

Mars is a world with as much land as Earth itself. A belt of rocky asteroids circles the Sun between the orbits of Mars and Jupiter.

 

With its four giant moons and dozens of smaller ones, Jupiter is like its own little solar system. It has more mass than all the other planets combined. Jupiter's Great Red Spot, a hurricane three times the size of our whole planet, that’s been raging for centuries.

 

The crown jewel of our solar system, Saturn, is ringed by freeways of countless orbiting and slowly tumbling snowballs. Every snowball, a little moon.

Uranus and Neptune, the outermost planets, were unknown to the ancients and only discovered after the invention of the telescope.

Beyond the outermost planet, there's a swarm of tens of thousands of frozen worlds. And Pluto is one of them.

 

Of all our spacecraft, this is the one that's travelled farthest from home, Voyager 1. She bears a message to a billion years from now, something of who we were, how we felt and the music we made. The deeper waters of this vast cosmic ocean and their numberless worlds lie ahead.

 

From out here, the Sun may look like just another star. But it still exerts its gravitational hold on a trillion frozen comets, leftovers from the formation of the solar system nearly five billion years ago. It's called the Oort Cloud.

No one has ever seen it before, nor could they, because each one of these little worlds is as far from its nearest neighbour as Earth is from Saturn. This enormous cloud of comets encloses the solar system, which is the second line of our cosmic address.

 We've only been able to detect the planets of other stars for a few decades, but we already know that planets are plentiful, they outnumber the stars. Almost all of them will be very different from Earth, and hostile to life as we know it.

But what do we know about life? We've met only one kind so far. Earthlife.

 

Human eyes see only a sliver of the light that shines in the cosmos. But science gives us the power to see what our senses cannot. Infrared is the kind of light made visible by night-vision goggles. Throw an infrared sensor across the darkness... Rogue planet. A world without a sun. Our galaxy has billions of them, adrift in perpetual night. They're orphans, cast away from their mother stars during the chaotic birth of their native star systems. Rogue planets are molten at the core but frozen at the surface. There may be oceans of liquid water in the zone between those extremes. Who knows what might be swimming there?

 

This is what the Milky Way looks like in infrared. Every single dot, not just the bright ones, is a star. 

How many stars?

How many worlds?

How many ways of being alive?

Where are we in this picture?

See that trailing outer arm? 

That's where we live about 30,000 light-years from the centre. The Milky Way Galaxy is the next line of our cosmic address. We're now a hundred thousand light-years from home. It would take light, the fastest thing there is a hundred thousand years to reach us from Earth.

 

This is the Great Spiral in Andromeda, the galaxy next door. We call our two giant galaxies and a smattering of smaller ones the "local group."

Can't even find our home galaxy from out here. It's just one of the thousands in the Virgo Supercluster. On this scale, all the objects we see, including the tiniest dots, are galaxies. Each galaxy contains billions of suns and countless worlds.

Yet, the entire Virgo Supercluster itself forms but a tiny part of our universe. This is the cosmos on the grandest scale we know, a network of a hundred billion galaxies. It's the last line of our cosmic address for now.

Observable universe?!

What does that mean?

Even for us, in our Imagination, there's a limit to how far we can see in space-time. It's our cosmic horizon. Beyond that horizon lie parts of the universe that are too far away. There hasn't been enough time in the 13.8 billion-year history of the universe for their light to have reached us. 

Many of us suspect that all of this all the worlds, stars, galaxies and clusters in our observable universe are but one tiny bubble in an infinite ocean of other universes, a multiverse. Universe upon universe. Worlds without end.

 

Feeling a little small?

Well, in the context of the cosmos, we are small. We may just be little guys living on a speck of dust, afloat in a staggering immensity, but we don't think small.

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This is just only the start of our journey. So please stay with us and come with us to explore the Cosmos.

Thank you.