Guest: Simon Singh.

The Big Bang model of the universe offers an elegant explanation of everything we see in the night sky, making it one of the greatest achievements of the human intellect and spirit. Even more wonderful, says science writer Simon Singh, it can be understood by everyone. Join us today on Focus as we talk with Singh about how scientist arrived at this remarkable theory.

Guests: Nigel Boston and Simon Singh.

Public key crypography is a system for maintaining privacy in communications that has allowed the information age to flower. Until recently, the true story of its invention was kept secret by the British government. Today on Focus, we're joined by journalist Simon Singh and expert Nigel Boston to hear the full story.