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We do not exist in the universe will never change. On the contrary, the principal contradiction in it, from the previous state of extreme temperature and density. About 14 million years ago, all the "things" to make up for ourselves, our planet, all the stars and galaxies were crammed far smaller than the size of a single hydrogen atom, or even small proton, and the core. The extension of the extreme state of the universe is the Big Bang describes the evolution of the universe and then the final accounts of the origin of stars, galaxies, planets and intelligent life.           The Primordial Question     Could the Universe have created itself? What an absurd idea! Did the Universe even have a beginning? That question, too, has an absurd ring. If there was a beginning, what came before? Wasn't that part of the Universe too? Or has the Universe always existed, begging the question of it own origin?   Whatever the answers to these questions, modern astrophysics makes one thing clear: our Universe hasn't existed forever unchanged. Rather, it's evolved from an earlier state of extreme temperature and density. Some 14 billion years ago, all the "stuff" that makes up ourselves, our planet Earth, and all the stars and galaxies was crammed into a volume far smaller than a single hydrogen atom or even the tiny proton at its core. The expansion of that extreme state is the Big Bang that describes the Universe's subsequent evolution and ultimately accounts for the origin of stars, galaxies, planets, and intelligent life.   What came before the Big Bang? What created that early, extreme state? We're back to the primordial question: Did the Universe have a beginning, or has it always existed—albeit an existence marked by evolutionary change?   To some cosmologists—scientists who concern themselves with the origin and evolution of the Universe—the start of the Big Bang marks the start of time itself. For them, it makes no sense to ask what came before because the concept of "before" is meaningless if there's no such thing as time. Others have envisioned an ever existing Universe that undergoes a series of oscillations. Each begins with a Big Bang and subsequent expansion—the phase we are now in—then eventually contracts toward a Big Crunch of extreme density and temperature that starts another cycle.   ...Surely, "The Universe" encompasses all that there is… But not according to Stanford University cosmologist Andrei Linde. For the Russian-born Linde, our Universe is but one small branch of possibly infinite Multiverse. What we think of as the Big Bang origin and evolution of the Universe is, to Linde, simply the "budding" and subsequent expansion of a new branch from pre-existing cosmos. That branch is our Universe. Other branches are different universes, each of which has had its own big bang and its own evolutionary scenario. Remarkably, each universe may even have its own laws of physics. The budding that produces a new universe may result in mutations from the laws that govern the parent branch. Together, all these interconnected universes form the Multiverse or, in Linde's more dynamic phrasing, the "self-replicating inflationary universe." Our own universe may someday spawn new buds that become entire universes; in fact, it may already have done so. It might not even take much effort to initiate such a bud. Cosmologist Alan Guth of MIT has suggested that with an ounce of material, crushed to high enough density, you might start a new universe right in your own garage! Perhaps we and our whole Universe are just the results of someone's experimentation in another branch of the Multiverse.   Linde's Multiverse provides yet another answer to the question of the Universe's origin. Our Universe, according to Linde, clearly had a beginning in the budding event that was the start of our Big Bang. But that budding occurred from one branch of a Multiverse that may have existed forever... The self-replicating Multiverse in some ways resembles a biological system. It's forever spawning new buds—"baby universes"—some of which grow to become full-blown universes like our own, which then produce their own babies. Others are stillborn, withering to collapse before they've had a chance to evolve complex structure and intelligent life. Universes come and go, so there are multiple beginnings. Creation isn't a one-time story. But the Multiverse persists forever, and, despite the birth and demise of individual universes, the large-scale picture may remain unchanged for eternity.         — Richard Wolfson, Simply Einstein: Relativity Demystified                 Indexes/12