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.

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.

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]

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].

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.

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.

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.

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.

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

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.

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

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.

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.

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...

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.

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.

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 ...

Physicist Patricia Burchat sheds light on two basic ingredients of our universe: dark matter and dark energy. Comprising 96% of the universe between them, they can't be directly measured, but their influence is immense.

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

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...

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...

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

Dimitar Sasselov works on uniting the physical and life sciences in the hunt for answers to the question of how life began.

The universe is incredibly old, astoundingly vast and populated by trillions of planets -- so where are all the aliens? Astronomer Stephen Webb has an explanation: we're alone in the universe. In a mind-expanding talk, he spells out the remarkable barriers a planet would need to clear in order to host an extraterrestrial civilization -- and make...