We speak with Brian Greene. He's a theoretical physicist at Columbia University. He's best known for his work on string theory. And in his new book, he argues that our universe probably isn't the only one and that there may actually be an infinite number of parallel universes. His new book is called The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos.

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PART THREE

Multiverse - Brian Greene

We started this segment with a clip from the famous Star Trek episode called Mirror Mirror, he's a ruthless, evil version of Spock in a parallel universe where Captain Kirk and other crew members of the Starship Enterprise find themselves after a glitch with their teleporter.

Parallel universes have fueled lots of wild musings among science fiction fans, philosophers and, well, stoners... The striking thing now is that - increasingly - high-powered scientists are pouring their brain power into probing whether the reality of the cosmos is not so much a "uni" verse but, really, a multiverse.

Brian Greene is a theoretical physicist at Columbia University. He's the author of The Elegant Universe, and his new book is The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos. He joined us in our Toronto studio.

Related Links:

• Expanding Horizons by Timothy Ferris - New York Times Book Review
• Greene, With Curiosity by Deborah Solomon - NYT
• Is speculation in multiverses as immoral as speculation in subprime mortgages? by John Horgan - Scientific American

Last Word - Amira Magdy

We gave the last word today to Egyptian pharmacist, Amira Magdy. The 22 year old helped treat the wounded during the mass protests that toppled Egyptian President Hosni Mubarak.

And when we spoke to her yesterday, she was at the Egyptian-Libyan border preparing to head into Libya with a group of Egyptian doctors and pharmacists to help the wounded there. As you've heard, mobile networks in Libya have been shut down so we don't know where Amira is now, but we aired what she told us yesterday on a very shaky phone line.

Other segments from today's show:

• Libya Protests
• TransCanada Pipeline