Asteroid strikes get all the coverage, but "Medea Hypothesis" author Peter Ward argues that most of Earth's mass extinctions were caused by lowly bacteria. The culprit, a poison called hydrogen sulfide, may have an interesting application in medicine.

We can't control if we'll die, but we can "occupy death," in the words of Peter Saul, an emergency doctor. He asks us to think about the end of our lives -- and to question the modern model of slow, intubated death in hospital. Two big questions can help you start this tough conversation.

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...

What do you do when your firmly held beliefs turn out not to be true? When Casey Gerald's religion failed him, he searched for something new to believe in -- in business, in government, in philanthropy -- but found only false saviors. In this moving talk, Gerald urges us all to question our beliefs and embrace uncertainty.

To save the achoque -- an exotic (and adorable) salamander found in a lake in northern Mexico -- scientists teamed up with an unexpected research partner: a group of nuns called the Sisters of the Immaculate Health. In this delightful talk, science journalist Victoria Gill shares the story of how this unusual collaboration saved the achoque from...

The founder of Sirius XM satellite radio, Martine Rothblatt now heads up a drug company that makes life-saving medicines for rare diseases (including one drug that saved her own daughter's life). Meanwhile she is working to preserve the consciousness of the woman she loves in a digital file ... and a companion robot. In an onstage conversation w...