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What If? Why Us? Why Now?
by Jesse Emspak


Section 1: Undiscovered Worlds

1.1   Parallel Universes
        by Max Tegmark

1.2   Extraordinary Claims
        by George F. R. Ellis

1.3   The Great Cosmic Roller-Coaster Ride
        by Cliff Burgess and Fernando Quevedo


Section 2: Explorations

2.1   Cracking Open a Window
        by George Musser

2.2   Out of the Darkness
        by Georgi Divali


Section 3: Multiple Dimensions

3.1   Looking for Life in the Multiverse
        by Alejandro Jenkins and Gilad Perez

3.2   Quantum Gravity in Flatland
        by Steven Carlip

3.3   The Universe’s Unseen Dimensions
        by Nima Arkani-Hamed, Savas Dimopolous and Georgi Divali


Section 4: Time and Time Again

4.1   Quantum Physics of Time Travel
        by David Deutsch and Michael Lockwood

4.2   The Myth of the Beginning of Time
        by Gabriele Veneziano

4.3   Been There, Done That
        by George Musser


Section 5: Why We Live Now

5.1   The String Theory Landscape
        by Raphael Bousso and Joseph Polchinski

5.2   Inconstant Constants
        by John D. Barrow and John K. Webb

5.3   The Inflation Debate
        by Paul J. Steinhardt

Possibilities in Parallel: Seeking the Multiverse

Parallel universes are a staple of science fiction, and it's no wonder. However, instead of "what if the South won the Civil War?" cosmologists ask, "what if the constants that make up the fundamental building blocks of physics were different?" Physicists argue that any slight change to the laws of physics would mean a disruption in the evolution of the universe, and thus our existence. With the myriad of factors that had to align for us to exist, it can seem like the laws of physics might seem finely tuned to make our existence possible. Short of a supernatural or divine explanation, one possibility is that our universe isn’t the only one, and that's the idea explored in this eBook.

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