Brian Greene's excellent series examining string theory and modern physics.

The universe began with a massive expansion, billions and billions of years ago, and it continues to expand with every passing second. The idea that the universe, and man's very existence, began with a ''Big Bang'' is no longer a topic of debate among most scientists--it is essentially taken as fact. How has man come to this ...

Scientists now believe there may really be a parallel universe - in fact, there may be an infinite number of parallel universes, and we just happen to live in one of them. These other universes contain space, time and strange forms of exotic matter. Some of them may even contain you, in a slightly different form. Astonishingly, scientists ...

Al-Khalili discovers that there might be parallel universes in which different versions of us exist, and finds out that empty space isn’t empty at all, but seething with activity. Part 1 Part 2