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."

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.

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.

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.

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.

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

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.

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]

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.

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.

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.

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.

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.

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.

If you were to take a coffee cup, and break it in half, then in half again, and keep carrying on, where would you end up? Could you keep on going forever? Or would you eventually find a set of indivisible building blocks out of which everything is made? Jonathan Butterworth explains the Standard Model theory and how it helps us understand the wo...

Physicist and surfer Garrett Lisi presents a controversial new model of the universe that -- just maybe -- answers all the big questions. If nothing else, it's the most beautiful 8-dimensional model of elementary particles and forces you've ever seen.

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.

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...

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 ...

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...

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

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.

Fascinating talks that seek to unravel some of the most fundamental, yet unexplainable parts of the cosmos.

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.

Physicist Brian Greene explains superstring theory, the idea that minscule strands of energy vibrating in 11 dimensions create every particle and force in the universe.

12 counterintuitive talks to flip your thinking on everything from shoes to aid organizations to the universe.

Is outer space really the silent and lifeless place it's often depicted to be? Perhaps not. Astrophysicist and musician Matt Russo takes us on a journey through the cosmos, revealing the hidden rhythms and harmonies of planetary orbits. The universe is full of music, he says -- we just need to learn how to hear it.

The biggest surprise of discovering the Higgs boson? That there were no surprises. Gian Giudice talks us through a problem in theoretical physics: what if the Higgs field exists in an ultra-dense state that could mean the collapse of all atomic matter? With wit and charm, Giudice outlines a grim fate -- and why we shouldn't start worrying just yet.

Cosmologist Sean Carroll attacks -- in an entertaining and thought-provoking tour through the nature of time and the universe -- a deceptively simple question: Why does time exist at all? The potential answers point to a surprising view of the nature of the universe, and our place in it.