Science and technology have powered huge leaps in understanding but our biggest challenges lie ahead.

The science of complexity is perhaps the greatest challenge of all, Astronomer Royal Sir Martin Rees believes.

The biggest conundrum is humanity and how we came to be, he told the Technology, Entertainment and Design (TED) conference in Oxford.

The cosmologist said that in the 21st Century science has changed the world faster than ever before and in many new ways.