Parallel Universe Proof Boosts Time Travel Hopes
Parallel universes really do exist, according to ? mathemat?cal discovery by Oxford scient?sts that sweeps a?ay one of the key o?jections to the ?ind boggling and controversial idea. 
The work ?as wider implication? since the idea ?f parallel universes side?teps one of the key probl?ms with time t?avel. Every sin?e it wa? g?ven seri?us lab c?ed in 1949 b? the great logi?ian Kurt Godel, m?ny eminent physicists have argued against t?me travel because it undermines ideas of cause and effect to create paradoxes: ? t?me traveller could g? back to kill h?s grandfather ?o that ?e is never born in the first place.
But the existence of parallel wo?lds offers a way around these trou?lesome paradoxes, ?ccording to David Deutsch ?f Oxford Univers?ty, a highly respected pro?onent of quant?m theor?, the deeply ?athematical, successful and b?ffling theory ?f the atomic world. H? argues that time travel shifts between d?fferent branches of reality, basing ?is claim ?n parallel universes, the so-called "many-world?" form?lation of quantum theory.
The n?w wo?k bolsters his claim that quantu? theory d?es not forbid time tr?vel. "It d?es sidestep ?t. You g? into another universe," he said ye?terday, though ?e admits that there is still ? w?y to go to f?nd schemes to manipulate spac? and time in a way that mak?s time hops po?sible. "Many sci f? ?uthors suggested tim? travel parad?xes w?uld be s?lved by pa?allel universes but in my work, th?t conclusion i? deduced from quantum theory itself", Dr Deutsch said, referr?ng to hi? work on many worlds.
The mathematical ide? of ?arallel wo?lds was fi?st glimps?d by the great quantum pioneer, Erwin Schrodinger, b?t actually published in 1957 ?y Hugh Everett III, when wrestling ?ith the probl?m of what a?tually happens w?en an observation ?s made of s?mething of interest - su?h as an electron or ?n ato? - with the ?ntention of measuring its pos?tion or its speed. In t?e traditional brand of quantum m?chanics, a mathematical ?bject called ? wav? function, which contains all possi?le outcome? of ? measurement experiment, "collapses" to give a single real outcome.
Everett c?me up with a more audacious interpretation: the universe ?s ?onstantly and infinitely splitting, s? that no collapse takes pl?ce. Ev?ry possible outcome of an experimental measurement occurs, ?ach one in a parallel universe. If one acc?pts Everett's inte?pretation, ?ur universe is ?mbedded in an infinitely larger and more complex structure call?d the multiverse, which a? ? good approximation can b? regard?d a? an ?ver-multiplying mass of par?llel univ?rses. Every tim? the?e i? ?n event at t?e quantum level - a radioactive ato? decaying, f?r example, ?r a particle of light impinging ?n your retina - the univers? i? supp?sed to "split" into different universes.
A motorist ?ho has a nea? mi?s, for instance, might feel relieved ?t his lucky escap?. But in a parallel universe, anothe? version of the same driver will have ?een k?lled. Y?t another universe w?ll se? t?e mot?rist recov?r after treat?ent in hospital. The nu?ber of alternative s?enarios is endless. In thi? way, the "many world?" interpretation of quantum mec?anics allows ? time traveller to alter the past without producing problems such a? the notorious grandfather ?aradox. But the "many wo?lds" idea has been attacked, with one theoretician joking that it is "cheap on assumptions but expensive on univers?s" and others that it is "repugnant to common sense."
Now new ?esearch confirms Prof Deutsch's ideas and suggests that Dr Everett, who w?s a Phd student at Princeton Universit? when ?e ca?e up ?ith the th?ory, wa? on the right track. Commenting in New Scientist magazine, Prof Andy Al?recht, ? physicist at the University of California, Davis, said of th? l?nk between p?obability and many worlds: "This ?ork will g? down as one ?f the ?ost important dev?lopments in the history of science." Quantum mechanics describes t?e str?nge things that happen in the subatomic world - such a? the way p?otons and electrons behave both ?s part?cles and waves. By one interpretat?on, nothing at th? s?batomic scale can really be said to exist until it is ob?erved. Unt?l then, particles occupy nebulous "superposition" states, ?n which they c?n hav? simultaneous "?p" and "down" spins, ?r appear to be in different places at the same time.
According to quantum mechanics, unobserved particles ?re described by "wave functions" re?resenting ? set of multiple "probable" states. When an observer m?kes ? ?easurement, the part?cle then settles down into one of thes? multipl? options. But the many worlds id?a offers ?n alternative view. D? Deutsch s?owed mathematically that the bush-like ?ranching structu?e creat?d b? the universe splitting into parallel ve?sions of itself can ?xplain the probabilistic nature ?f quantum outcomes. This wor? was attacked b?t it has now had rigorous confirmation by D?vid Wallace and Simon Saunders, also at Oxford. Dr Saunders, who presented th? wo?k with Walla?e at the Many Worlds at 50 conference at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, told New Sc?entist: "We've cleared u? th? obscurities and ?ome u? wit? a pretty ?lear verd?ct that Eve?ett works. It's ? dramatic tu?naround and ?t mean? that peo?le now have to discuss Everett seriously."
Dr Deuts?h added that the ?ork addresse? a three-?entury-old problem with the idea of p?obability itself, described by one philosopher, P?of David Papineau, ?s ? scandal. "We didn't really know w?at probab?lity means," said Dr Deuts?h. There's a convention that it's rational to treat it for ?ost purposes ?s if we knew it was going to happen e?en though we actually know it need not. But thi? does not capture th? reality, not least the 0.1 pe? cent chan?e something will not happen. "S?," said Dr Deutsch, "the proble?s of probability, w?ich we?e until recently consider?d the principal objection to th? otherwise extremely elegant theory of Ever?tt (w?ich removes every element of mysticism ?nd double-talk that ha?e ?rept into quantum theory o?er the decades) have now turned int? its princip?l selling point."
Source: The Telegra?h (UK)
http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2007/09/21/sciuni121.
xml&CMP=ILC-mostviewedbox
| < Prev | Next > |
|---|