Kevin Alloca discusses the four main resons why videos go viral.TEDTalks is a daily video podcast of the best talks and performances from the TED Conference, where the world's leading thinkers and doers give the talk of their lives in 18 minutes. Featured speakers have included Al Gore on climate ch...

Neurologist and author Oliver Sacks brings our attention to Charles Bonnett syndrome -- when visually impaired people experience lucid hallucinations. He describes the experiences of his patients in heartwarming detail and walks us through the biology of this under-reported phenomenon.

In 2014, the world avoided a horrific global outbreak of Ebola, thanks to thousands of selfless health workers — plus, frankly, thanks to some very good luck. In hindsight, we know what we should have done better. So, now's the time, Bill Gates suggests, to put all our good ideas into practice, from