Is there more than one universe? In this visually rich, action-packed talk, Brian Greene shows how the unanswered questions of physics (starting with a big one: What caused the Big Bang?) have led to the theory that our own universe is just one of many in the "multiverse."

In keeping with the theme of TED2008, professor Stephen Hawking asks some Big Questions about our universe -- How did the universe begin? How did life begin? Are we alone? -- and discusses how we might go about answering them.

Is Earth really the only life-sustaining planet? These speakers think there might just be something or someone else out there -- and urge us to keep looking for it.

Imagine a life living among the stars, traversing the universe, interacting with aliens ...

The universe began in a Big Bang nearly fourteen billion years ago, and has been expanding ever since. But how does the universe expand and what is it expanding into? Sajan Saini explains the existing theories around the Big Bang and what, if anything, lies beyond our universe. [TED-Ed Animation by Wooden Plane Productions]

We think of space as a silent place. But physicist Janna Levin says the universe has a soundtrack -- a sonic composition that records some of the most dramatic events in outer space. (Black holes, for instance, bang on spacetime like a drum.) An accessible and mind-expanding soundwalk through the universe.

Find out what sound a black hole makes, if (possible) alien life is blocking star light and other astounding things happening in our galaxy -- and beyond.

It's been a long road to the discovery that Earth is not the center of the Solar System, the Milky Way, or the universe; great thinkers from Aristotle to Bruno have grappled with it for millennia. But if we aren't at the center of the universe, what is? Marjee Chmiel and Trevor Owens discuss where we stand in the (very) big scheme of things. [Di...

Biologist Richard Dawkins makes a case for "thinking the improbable" by looking at how the human frame of reference limits our understanding of the universe.

At Serious Play 2008, astrophysicist George Smoot shows stunning new images from deep-space surveys, and prods us to ponder how the cosmos -- with its giant webs of dark matter and mysterious gaping voids -- got built this way.

Why is there something instead of nothing? In other words: Why does the universe exist (and why are we in it)? Philosopher and writer Jim Holt follows this question toward three possible answers. Or four. Or none.

The atoms around you have existed for billions of years -- and most originated in the flaming, gaseous core of a star. Dennis Wildfogel tells the captivating tale of these atoms' long journeys from the Big Bang to the molecules they form today. [Directed by Pew36 Animation Studios, narrated by Dennis Wildfogel].

For the last 12 years, Carter Emmart has been coordinating the efforts of scientists, artists and programmers to build a complete 3D visualization of our known universe. He demos this stunning tour and explains how it's being shared with facilities around the world.

How did the universe begin -- and how is it expanding? CERN physicist Tom Whyntie shows how cosmologists and particle physicists explore these questions by replicating the heat energy and activity of the first few seconds of our universe from right after the Big Bang. [Directed by Dan Abdo and Jason Patterson, narrated by R.J. Glass].

NASA engineer Bobak Ferdowsi helped the Curiosity rover land on Mars -- and he's curated these talks that deepen our understanding of the world around us.

Beyond our galaxy, there lies much more to be discovered. Learn how we explore the universe with talks that are definitely out of this world.

Zoom into the strange wonder and potential of stars in our universe.

At the Royal Institution in 1991, Richard Dawkins asks us to look at our universe with new eyes. Packed with big questions and illuminating visuals, this memorable journey through the history of life magnifies the splendor of evolution and our place in it.

Blind river dolphins, reclusive lemurs, a parrot as fearless as it is lovelorn ... Douglas Adams' close encounters with these rare and unusual animals reveal that evolution, ever ingenious, can be fickle too -- in a University of California talk that sparkles with his trademark satiric wit.

The shape, contents and future of the universe are all intricately related. We know that it's mostly flat; we know that it's made up of baryonic matter (like stars and planets), but mostly dark matter and dark energy; and we know that it's expanding constantly, so that all stars will eventually burn out into a cold nothingness. Renée Hlozek expa...

We know about our universe's past: the Big Bang theory predicts that all matter, time and space began about 14 billion years ago. And we know about the present: scientists' observations of galaxies tell us that the universe is expanding at an accelerated rate. But what about the future? Do we know how our universe is going to end? Venus Keus exp...

Our universe is strange, wonderful and vast, says astronomer Natasha Hurley-Walker. A spaceship can't carry you into its depths (yet) -- but a radio telescope can. In this mesmerizing talk, Hurley-Walker shows how she probes the mysteries of the universe using special technology that reveals light spectrums we can't see.

The Greeks had a simple and elegant formula for the universe: just earth fire wind and water. Turns out there's more to it than that -- a lot more. Visible matter (and that goes beyond the four Greek elements) comprises only 4% of the universe. CERN scientist James Gillies tells us what accounts for the remaining 96% (dark matter and dark energy...

When and how did the universe begin? A global group of astronomers wants to answer that question by peering as far back in time as a large new telescope will let us see. Wendy Freedman headed the creation of the Giant Magellan Telescope, under construction in South America; at TEDGlobal in Rio, she shares a bold vision of the discoveries about o...

Something massive, with roughly 1,000 times the area of Earth, is blocking the light coming from a distant star known as KIC 8462852, and nobody is quite sure what it is. As astronomer Tabetha Boyajian investigated this perplexing celestial object, a colleague suggested something unusual: Could it be an alien-built megastructure? Such an extraor...

Artist-technologist Honor Harger listens to the weird and wonderful noises of stars and planets and pulsars. In her work, she tracks the radio waves emitted by ancient celestial objects and turns them into sound, including "the oldest song you will ever hear," the sound of cosmic rays left over from the Big Bang.

Big Data is everywhere — even the skies. In an informative talk, astronomer Andrew Connolly shows how large amounts of data are being collected about our universe, recording it in its ever-changing moods. Just how do scientists capture so many images at scale? It starts with a giant telescope ...

Travel across the universe (or is it universes?) to see stunning images of Saturn's rings, hear haunting sounds from distant black holes and catch an infectious sense of wonder about galaxies far, far away.

Gian Giudice is a theoretical physicist who has contributed greatly to our present understanding of particle physics and cosmology.

Dive into the unexplored universe beneath the waves: the beautiful, fragile (and sometimes terrifying) world of the ocean.