- Home >
- Big Questions >
- Space, Time & Astronomy >
- Is our universe the only one?
"Our universe may be just one element ? one atom, as it were ? in an infinite ensemble: a cosmic archipelago. Each universe starts with its own big bang, acquires a distinctive imprint (and its individual physical laws) as it cools, and traces out its own cosmic cycle. The big bang that triggered our entire universe is, in this grander perspective, an infinitesimal part of an elaborate structure that extends far beyond the range of any telescopes." (Sir Martin Rees, Before the Beginning, 1997).
This relatively recent idea is known as the Multiverse theory, and describes the continuous formation of universes through the collapse of giant stars and the formation of black holes. Beyond the singularity (the point inside the black holes in which all matter disappears) in each black hole a new universe would be possible. Because physical behaviour can't be predicted beyond the point of singularity, the laws of physics as we know them may not exist. For instance, there might be no gravity or electromagnetism. If this were the case, this realm would not be a part of our Universe.
Following this line of thinking, some have speculated that our Universe is one of a set of disconnected universes, collectively called the multiverse. The size of our Universe would be infinitesimal compared to this proposed Multiverse.
Psychologist William James coined the term "multiverse" in 1895, and the possibility of disconnected universes has been debated in theology and philosophy for centuries. Multiverses have been proposed in cosmology, physics, astronomy, psychology and fiction. They have been variously labelled "alternative universes", "quantum universes", "interpenetrating dimensions", "parallel worlds", "alternative realities", "alternative timelines", etc.
Even though fictional characters travel between "parallel universes", the multiverse theory dictates that nothing in one universe could possibly affect another universe - if it did the two would be part of the one universe.
In the multiverse theory, disconnected universes each have their own space and time, their own matter and energy, and their own physical laws. Such physically disconnected universes are different from the metaphysical concept of different planes of consciousness hypothetically connected through the flow of information.
The multiverse theory gets even more complex in the so-called many-worlds hypothesis, which says that a parallel universe is born with every quantum measurement; the universe "forks" into parallel copies, each one corresponding to a different outcome of the quantum measurement.
By definition the idea of the multiverse must remain speculative as no experiment in one universe could reveal the existence or properties of another non-interacting universe.
Further reading
Max Tegmark, Scientific American, The Multiverse Hierarchy, http://arxiv.org/PS_cache/arxiv/pdf/0905/0905.1283v1.pdf
Max Tegmark, Scientific American, "Parallel universes. Not just a staple of science fiction, other universes are a direct implication of cosmological observations." Scientific American, May; 2003, 288(5):40-51, http://space.mit.edu/home/tegmark/PDF/multiverse_sciam.pdf
My So-Called Universe - Arguments for and against an infinite and parallel universes,
http://www.slate.com/id/2087206/nav/navoa/
http://www.bbc.co.uk/science/horizon/2001/parallelunitrans.shtml
Steven Weinberg, 2005, "Living in the Multiverse"
Maurizio Gasperini, Elements of String Cosmology, 2007
Paul Halpern, The Great Beyond, 2005
Baird, Eric (2007). Relativity in Curved Spacetime. Chocolate Tree
Deutsch, Harry, "Relative Identity", The Stanford Encyclopedia of Philosophy (Summer '02), Edward N. Zalta (ed.)
Deutsch, David (45841 1985). Splash. ed. Quantum theory, the Church-Turing principle and the universal quantum computer (Proceedings of the Royal Society of London A 400 ed.). pp. 97-117
http://www.slate.com/id/2087206/
Michael Price's Everett FAQ
The ensemble of universes describable by constructive mathematics by Jürgen Schmidhuber, http://www.idsia.ch/~juergen/computeruniverse.html
Podcast: "Many Worlds in One: The Search for Other Universes", Tufts cosmologist Alex Vilenkin, http://www.thoughtcast.org/casts/the-end-of-our-universe-among-other-timely-topics/
References
http://en.wikipedia.org/wiki/Multiverse
http://www.astronomy.pomona.edu/Projects/moderncosmo/Sean%27s%20mutliverse.html
Martin Rees, Before the Beginning, Helix Books, 1997
