We get questions every week about string theory and topics popularized by science fiction. Here's the problem. There's just no evidence. Each of these is based on wonderful and well-formed mathematical equations, or wishful thinking, but they're very hard (if not impossible) to test in the real Universe.

<strong><a href="http://media.libsyn.com/media/astronomycast/AstroCast-070409.mp3">Episode 31: String Theory, Time Travel, White Holes, Warp Speed, Multiple Dimensions, and Before the Big Bang (14.4 MB)</a></strong>

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