Science Fair Project Encyclopedia
The idea that the universe that we can observe is only part of the whole physical reality led to the definition of 'multiverse', the set of multiple possible universes.
The term "multiverse" was coined in December 1960, by Andy Nimmo , then vice chairman of the British Interplanetary Society, Scottish Branch, for a talk to the branch on the many-worlds interpretation of quantum physics which had been published in 1957. This was given in February 1961, and the word with its original definition, "an apparent universe, a multiplicity of which, go to make up the whole universe" was then first used. This was because, at the time, the definition of the word 'universe' was "All that there is" and etymologically one cannot have "Alls that there is". "Uni" means one, and "multi" means many, so this meaning allowed for many multiverses.
The word was then used both correctly and incorrectly at various times in scientific and science fiction circles for several years. Then in the late 1960s science fiction author Michael Moorcock interpreted the word in a novel. After reading this novel, David Deutsch used the term "multiverse" in a scientific work as the totality of all possible universes throughout time, including our observable universe—the opposite of its previous definition. Other scientists, not being etymologists, then picked up and adopted the popular redefinition of the word.
Scientific theories related to quantum physics
Many world interpretation of quantum physics
A multiverse of a somewhat different kind has been envisaged within the 11-dimensional extension of string theory known as M-theory. In M-theory our universe and others are created by collisions between membranes in an 11-dimensional space. Unlike the universes in the "quantum multiverse", these universes can have completely different laws of physics—anything may be possible.
Scientific theories related to the Big Bang
The formation of our universe from a "bubble" of a multiverse was proposed by Linde and fits well with the widely accepted theory of inflation.
According to some quantum loop gravity theorists, the Big Bang was merely the beginning of a period of expansion that followed a period of contraction. In this view, one could talk of a Big Crunch followed by a Big Bang, or more simply, a Big bounce.
Another theory was proposed by M J Murcott in 1989. Murcott bases his theory on the assumption that space is infinite; that is, that one can travel forever in any direction and always continue to reach new points. Another of his assumptions relies on the theory that at some stage in the past matter was distributed fairly evenly across space, and later condensed to form objects dense enough to become the source for a big bang. However, in this situation we would expect that rather than there being only a single big bang, matter would condense in a number of places separated by astronomical distances, forming a network or lattice of big bangs all exploding and then contracting like a network of beating hearts or the atoms in a crystal. Thus, rather than having a single big bang and a single universe, there would be a collection of universes, or a multiverse.
This is Murcott's multiverse theory, but it has little scientific support at this time, due to its inherent difficulty in verification. However, there are some observable differences that may be visible if the multiverse theory is accurate. The most noticeable would be a gravitational force pulling on the edge of our universe, which wouldn't have a large effect on the day to day world but would have two subtle effects: for one, the amount of matter required to prevent an immediate collapse of the universe in on itself would be considerably reduced, and so our universe would contain less matter than predicted by about 90%; some observations give weight to this argument. The other, more controversial piece of evidence would predict that matter on the edge of our universe does not slow down but instead actually accelerates as it is pulled towards other universes; some observations also support this theory.
Philosophical theories related to the origin of life
The concept of other universes has been proposed by philosophers to explain why our universe seems to be fine-tuned for life as we know it.
The concept of the multiverse figures prominently in many science fiction and fantasy novels. For some it serves primarily as a plot device, a means to put characters into an unfamiliar situation, or a framework that usually lies in the background for continuity purposes. For others it is a major theme and focus of the work. It is sometimes used as the basis for exploring "what if" scenarios, such as in Alternative history (fiction) stories.
Among the more famous fictional "multiverses" is that of Michael Moorcock. On developing his concept of the multiverse, Moorcock was developing his "Eternal Champion" stories at around the time Everett was developing his theory. Moorcock first used the term in print in the 1962 novel The Blood-Red Game. In the same year, the original Eternal Champion novella was published in Science Fantasy Magazine. On the influence of Everett's work, he says:
- It was an idea in the air, as most of these are, and I would have come across a reference to it in New Scientist (one of my best friends was then editor) ... [or] physicist friends would have been talking about it. ... Sometimes what happens is that you are imagining these things in the context of fiction while the physicists and mathematicians are imagining them in terms of science. I suspect it is the romantic imagination working, as it often does, perfectly efficiently in both the arts and the sciences.
The science fiction TV series Sliders was founded upon the idea of an infinite number of "alternate" Earths, with each Earth existing in a different and separate universe. At the beginning of each episode the protagonists would "slide" to a new universe, each different from their own in some way, trying to get back to their own.
Michael Crichton also delved into the possibility of travel between other realities in the multiverse in his novel Timeline, and the device is fundamental to the Philip Pullman trilogy His Dark Materials.
H._Beam_Piper, the author of the Paratime series, wrote several stories dealing with alternate realities based on points of divergence far in the past. The stories are usually written from the perspective of a law-enforcement outfit from a parallel reality which is charged to protect the secret of temporal transposition.
The popular comic book publishers Marvel Comics and DC Comics each have their own fictional multiverses that exist within the framework of their separate continuities. See Multiverse (DC Comics) and Multiverse (Marvel Comics) for more about these multiverses.
Douglas Adams, author of the Hitchhiker's Guide to the Galaxy series, delves into the concept in the last book, Mostly Harmless, where it is stated that Earth (and everything else in the universe) exists in multiple places along a fictional extra axis in the four dimensions as we know them, one of probability.
The Dungeons & Dragons role-playing game has a thoroughly developed system of planes of existence. A popular campaign setting for the game, Planescape, centres around travelling between these planes. Ravenloft, a gothic horror setting for Dungeons & Dragons, is based entirely in a single demiplane
An episode of the original Star Trek series entitled "Mirror, Mirror" introduced an "alternate" version of the Star Trek universe where the main characters were barbaric and evil. Subsequent novels and episodes revisited this universe. Other Star Trek stories have dealt with changes in history, but imply only a singular timeline, rather than a multiverse of alternate timelines.
A large number of fantasy stories involve a character being suddenly transported from one world or universe (often from our own Earth) into another universe. Notable stories of this sort include the Thomas Covenant stories of Stephen R. Donaldson, the Guardians of the Flame series by Joel Rosenberg, and the Narnia series by C. S. Lewis. In Lewis' The Magician's Nephew, the Wood between Worlds was a vast "linking room" with only three worlds explored by Lewis himself.
- Preprint of David Deutsch's paper The Structure of the Multiverse
- Michael Price's Everett FAQ
- Many Worlds & Parallel Universes — additional background information
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