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Parallel Universe Proof Boosts Time Travel Hopes


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Parallel universe proof boosts time travel hopes


Last Updated: 3:01pm BST 21/09/2007


Science fiction looks closer to becoming science fact, reports Roger Highfield


Parallel universes really do exist, according to a mathematical discovery by Oxford scientists that sweeps away one of the key objections to the mind boggling and controversial idea.


Time travellers: David Tennant as Doctor Who with Billie Piper as Rose

Time travellers: David Tennant as Doctor Who with Billie Piper as Rose


The work has wider implications since the idea of parallel universes sidesteps one of the key problems with time travel. Every since it was given serious lab cred in 1949 by the great logician Kurt Godel, many eminent physicists have argued against time travel because it undermines ideas of cause and effect to create paradoxes: a time traveller could go back to kill his grandfather so that he is never born in the first place.


But the existence of parallel worlds offers a way around these troublesome paradoxes, according to David Deutsch of Oxford University, a highly respected proponent of quantum theory, the deeply mathematical, successful and baffling theory of the atomic world.


He argues that time travel shifts between different branches of reality, basing his claim on parallel universes, the so-called "many-worlds" formulation of quantum theory.


The new work bolsters his claim that quantum theory does not forbid time travel. "It does sidestep it. You go into another universe," he said yesterday, though he admits that there is still a way to go to find schemes to manipulate space and time in a way that makes time hops possible.



"Many sci fi authors suggested time travel paradoxes would be solved by parallel universes but in my work, that conclusion is deduced from quantum theory itself", Dr Deutsch said, referring to his work on many worlds.


The mathematical idea of parallel worlds was first glimpsed by the great quantum pioneer, Erwin Schrodinger, but actually published in 1957 by Hugh Everett III, when wrestling with the problem of what actually happens when an observation is made of something of interest - such as an electron or an atom - with the intention of measuring its position or its speed.


In the traditional brand of quantum mechanics, a mathematical object called a wave function, which contains all possible outcomes of a measurement experiment, "collapses" to give a single real outcome.


Everett came up with a more audacious interpretation: the universe is constantly and infinitely splitting, so that no collapse takes place. Every possible outcome of an experimental measurement occurs, each one in a parallel universe.


If one accepts Everett's interpretation, our universe is embedded in an infinitely larger and more complex structure called the multiverse, which as a good approximation can be regarded as an ever-multiplying mass of parallel universes.


Every time there is an event at the quantum level - a radioactive atom decaying, for example, or a particle of light impinging on your retina - the universe is supposed to "split" into different universes.


A motorist who has a near miss, for instance, might feel relieved at his lucky escape. But in a parallel universe, another version of the same driver will have been killed. Yet another universe will see the motorist recover after treatment in hospital. The number of alternative scenarios is endless.


In this way, the "many worlds" interpretation of quantum mechanics allows a time traveller to alter the past without producing problems such as the notorious grandfather paradox.


But the "many worlds" idea has been attacked, with one theoretician joking that it is "cheap on assumptions but expensive on universes" and others that it is "repugnant to common sense."


Now new research confirms Prof Deutsch's ideas and suggests that Dr Everett, who was a Phd student at Princeton University when he came up with the theory, was on the right track.


Commenting in New Scientist magazine, Prof Andy Albrecht, a physicist at the University of California, Davis, said of the link between probability and many worlds: "This work will go down as one of the most important developments in the history of science."


Quantum mechanics describes the strange things that happen in the subatomic world - such as the way photons and electrons behave both as particles and waves. By one interpretation, nothing at the subatomic scale can really be said to exist until it is observed.


Until then, particles occupy nebulous "superposition" states, in which they can have simultaneous "up" and "down" spins, or appear to be in different places at the same time.


According to quantum mechanics, unobserved particles are described by "wave functions" representing a set of multiple "probable" states. When an observer makes a measurement, the particle then settles down into one of these multiple options.


But the many worlds idea offers an alternative view. Dr Deutsch showed mathematically that the bush-like branching structure created by the universe splitting into parallel versions of itself can explain the probabilistic nature of quantum outcomes. This work was attacked but it has now had rigorous confirmation by David Wallace and Simon Saunders, also at Oxford.


Dr Saunders, who presented the work with Wallace at the Many Worlds at 50 conference at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, told New Scientist: "We've cleared up the obscurities and come up with a pretty clear verdict that Everett works. It's a dramatic turnaround and it means that people now have to discuss Everett seriously."


Dr Deutsch added that the work addresses a three-century-old problem with the idea of probability itself, described by one philosopher, Prof David Papineau, as a scandal. "We didn't really know what probability means," said Dr Deutsch.


There's a convention that it's rational to treat it for most purposes as if we knew it was going to happen even though we actually know it need not. But this does not capture the reality, not least the 0.1 per cent chance something will not happen.


"So," said Dr Deutsch, "the problems of probability, which were until recently considered the principal objection to the otherwise extremely elegant theory of Everett (which removes every element of mysticism and double-talk that have crept into quantum theory over the decades) have now turned into its principal selling point."

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Very cool and interesting stuff! Star Trek is coming true! The episode of TNG where Worf shifts between different quantum realities could actually happen, and of course it will a few centuries from now. Glory! :)


I would like to visit the reality where I am the Benevolent and Fabulously Wealthy Lord of the Universe and kill that Jeff and assume his identity. :grin:

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I'll take the Mr. Spock position on this one...interesting.

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There is the problem of breaching the finite time loop horizion without a massive discharge of radiation wiping out most macro matter with it...

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To call it many options, or other worlds, or other universes or whatever is misleading and forms the wrong picture in one's head. It's a continuity, when observed as a function of the next higher dimension. As a function of the 4th dimension, what we commonly call time, we appear as we do....bipedal creatures confined in our skin and 3D space. When observed from the 5th dimension, we would appear as winding worms, with a zygote at the head end and our dead rotting corpse at the tail end. Of course the entire universe would be a 4th dimensional entity going through its own thing, can't even imagine what that would look like in 5 dimensional awareness......



You can create alternate timelines by moving through the 5th dimension, but you can "create" ones that never existed (not possible in your current timeline from whatever 5th D vantage point [in 3D space what we call a 'place', in 4D space what we call a 'moment' or 'situation'] you're regarding the 4th D space) by moving through the 6th dimension.




Does that make any sense or just sound completely insane?





My guess is that time travel won't look anything like the common sci fi portrayal of it. It might actually come in the form of psychology and understanding the nature of awareness. Time travel might come in the form of a mind expansion experiment.

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1 meter in 1 dimensional space is 1 meter

1 meter in 2 D space is 1 m2

1 meter in 3D space is 1m*1m*1m

1 meter in time is.......how long?



If you could raise your awareness to the 5th dimension somehow, and measure a meter of the 4th dimension, what would the conversion be? 1 meter = how many seconds, minutes, hours.....



And if we traveled through time at a varying rate or at a constant rate, how would we know the difference? If the universe slows down or speeds up, our awareness slows down or speeds up with it.

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The only analogy I can come up with is arguing about how many angels can fit onto the head of a pin.....


Yes, I believe this discussion (the original article) is just as hypothetical and unproductive.

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