Nature, said Galileo, is 'a book written in the language of mathematics'. But why should this be? How can mathematics be at the heart of our universe? The great Hungarian physicist and Nobel laureate Eugene Wigner stressed that this 'unreasonable effectiveness' of mathematics at describing the world was a mystery demanding explanation. Here, Max Tegmark, one of the most original cosmologists at work today, takes us on an astonishing journey to solve that mystery. Part-history of the cosmos, part-intellectual adventure, Our Mathematical Universe travels from the Big Bang to the distant future via parallel worlds, across every possible scale - from the sub-atomic to the intergalactic - showing how mathematics provides the answers to our questions about the world. Where do we come from? What makes the universe the way it is? In essence, why are we here? With dazzling clarity, Max Tegmark ponders these deep mysteries and allows us to grasp the most cutting-edge and mind-boggling theories of physics. What he proposes is an elegant and fascinating idea: that our physical world not only is described by mathematics, but that it is mathematics. Astoundingly, we may live in a mathematical universe. Max Tegmark is author or co-author of more than 200 technical papers, twelve of which have been cited more than 500 times. He has featured in dozens of science documentaries, and his work with the SDSS collaboration on galaxy clustering shared the first prize in Science magazine's Breakthrough of the Year: 2003. He holds a Ph.D from the University of California, Berkeley, and is a physics professor at MIT.