Is the universe we see – stars, moons, planets, clusters of galaxies – a small, accidental tip of an infinite cosmic iceberg? During the epoch of inflation, thought to have been triggered by the phase transition that marked the end of the grand unification at approximately 10^−36 seconds after the Big Bang, the accelerating expansion of space was far more dramatic than in today’s universe. Inflation lasted for only 10^-32 seconds, but the universe expanded at an absolutely staggering rate, increasing in size by a factor of 10^26. During this period, no objects – even two elementary particles – remained close enough to one another for long enough to interact.Small Piece of Space Formed Our Universe
“Objects separated by the width of an atom at the beginning of inflation,” notes Dan Hooper, Senior Scientist and the Head of the Theoretical Astrophysics Group at the Fermi National Accelerator Laboratory, in At the Edge of Time, “were trillions of miles apart from one another by the time it was over—only a minuscule fraction of a second later. So utterly complete was this act of sequestration, that these regions became more than merely distant. Inflation left them in entirely different universes. A small piece of the space that emerged from inflation went on to form our universe, while other pieces were stretched into newly formed universes, populating a greater multiverse of disconnected worlds.”
Leads to a Multiverse
“It’s hard to build models of inflation that don’t lead to a multiverse,” observed MIT physicist Alan Guth who developed the idea. Cosmic inflation and the nascent inflationary universe passed through a phase of exponential expansion soon after the Big Bang, driven by a positive vacuum energy density. “It’s not impossible, so I think there’s still certainly research that needs to be done. But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking the idea of a multiverse seriously.”
What Exists Beyond the Edge?
Perhaps we will never know what exists beyond the “edge” of our spherical observable universe, but there’s a variation of the multiverse theory in which the multiple universes are not separate entities. Instead, they are isolated, non-interacting pockets of space within one continuous fabric of space-time—”like multiple ships at sea” says Neil deGrasse Tyson, “far enough away from one another so that their circular horizons do not intersect yet they all share the same body of water.”
Although we may never directly detect the multiverse, scientists can still test different types of inflation models. Inflation models that predict the existence of the multiverse also predict certain observable signatures, such as primordial gravitational waves emanating from the rapid acceleration of matter. Astronomers are currently searching for the imprints of such primordial gravitational waves, the detection of which would be key evidence not only for inflation, but the flavor of inflation that created a multiverse.
There is every reason to suspect that in some fraction of these universes, matter and energy could take on forms that are the same or at least similar to those we find in our world—such as atoms and light with the same underlying laws of physics and many of the chemical species that we find in our Solar System.
Alien Worlds with Unknown Forces –The Hidden Multiverse
Yet some regions within the multiverse are likely to be alien worlds with unknown forces and new forms of matter along with more – or fewer – than three dimensions of space. Worlds may be utterly unlike anything we can imagine, says Hooper.
Russian physicist Alexander Antonov speculates that beyond our universe may exist a “hidden multiverse” of parallel universes. Antonov’s paper, Hypothesis of the Hidden Multiverse Explains Dark Matter and Dark Energy, states: “Analysis of WMAP and Planck spacecraft data has proved that we live in an invisible Multiverse, referred to as hidden, that has a quaternion structure. It explains the reason for the mutual invisibility of parallel universes contained in the hidden Multiverse. It is shown that the hidden Multiverse includes most likely twenty parallel universes from different dimensions, six of which are adjacent to our universe. Besides, edges of the hidden Multiverse are connected to other (from one to four) Multiverses, which are observable neither by electromagnetic nor by gravitational manifestations.”
“The Multiverse described contains four matter-antimatter pairs, annihilation of which is prevented by relative spatial position of the universes. The experimental proof of existence of the hidden Multiverse is explained to be the phenomenon of dark matter and dark energy that correspond to other invisible parallel universes, except ours, included in the hidden Multiverse.”
Perhaps, in another universe, another you is wondering if Antonov’s multiverse theory is true.
[Editor’s Note: Regarding dark matter and dark energy, I don’t think we should speculate about how that relates to inflation and the multiverse – they are very different physical processes and time/length scales.]