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Science

Time Travel 1191

Posted by michael
from the gladly-pay-you-tuesday-for-a-hamburger-today dept.
Almost Anonymous writes "Ronald Mallett, a physicist at the University of Connecticut, believes he knows how to build a time machine - an actual device that could send something or someone from the future to the past, or vice versa. He plans to have a working mockup this fall. For all those doubters, he assures people that "I'm not a nut"." Uh-huh.
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Time Travel

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  • by sjwt (161428) on Sunday April 07, 2002 @02:44AM (#3297943)

    ----- Original Message -----
    From: "Andrew Yee"
    Newsgroups: sci.space.news
    Sent: Friday, May 18, 2001 1:34 AM
    Subject: Time Twister (Forwarded)

    > New Scientist
    > http://www.newscientist.com
    >
    > Contact:
    > Claire Bowles, claire.bowles@rbi.co.uk, 44-207-331-2751
    >
    > EMBARGOED FOR RELEASE: May 16, 2001, 14:00 EDT US
    >
    > Time Twister
    >
    > Before your children are born, their children could turn up at your door.
    > Michael Brooks discovers how to turn the future into the past
    >
    > RONALD MALLETT thinks he has found a practical way to make a time machine.
    > Mallett isn't mad. None of the known laws of physics forbids time travel,
    > and in theory, shunting matter back and forth through time shouldn't be that
    > difficult.
    >
    > The catch usually comes when you try to make it work in practice. Remember
    > wormholes, those clever little tunnels in space and time that can supposedly
    > be used to travel from one moment to another? On paper, they're a perfectly
    > respectable way to travel back in time. Trouble is, you need a supply of
    > exotic "negative energy" matter to prise your wormhole open.
    >
    > But Mallett, a professor of theoretical physics at Connecticut University,
    > believes he has found a route to the past that uses something much more down
    > to earth: light. Mallett has worked out that a circulating beam of light,
    > slowed to a snail's pace, just might be the vital ingredient for time travel.
    > Not only is the technology within our grasp, Mallett has teamed up with
    > other scientists at Connecticut to work towards building it. "With this
    > device," he says, "time travel may become a practical possibility."
    >
    > It may be hard for us to climb into Mallett's time machine, as slowing light
    > down requires temperatures close to absolute zero. But future, advanced
    > civilisations might work out a way to do it. And they might even come back
    > to tell us how. If it works in the way Mallett believes it might, his device
    > would provide time travellers from the future with their first gateway into
    > our history.
    >
    > Mallett began his journey into the past when he was just ten years old. In
    > 1955, his father died of a heart attack. "For me, the sun rose and set on
    > him. It completely devastated me," Mallett says. But then he came across
    > The Time Machine by H. G. Wells. Even as a child, Mallett knew his father
    > hadn't taken care of himself. Drinking and heavy smoking took a toll on
    > his weak heart, and it gave out at the age of 33. "My notion was that if
    > I could build a time machine, I might be able to warn him about what was
    > going to happen," Mallett says. "That became my guiding light."
    >
    > What started as a childish notion grew into a passionate investigation of
    > everything ever written about time travel. When Mallett studied the work
    > of Einstein -- who died in the same year as his father -- he realised that
    > Wells's novel was right on track: time travel is, in theory at least,
    > achievable.
    >
    > Einstein himself found the notion upsetting, but he had only himself to
    > blame. He showed that the effect we call gravity is a bending of space and
    > time. Anything that has mass or energy distorts the space and the passage
    > of time in its vicinity, a bit like the way the surface of a soft couch is
    > distorted when someone sits on it. Solving Einstein's gravitational field
    > equations tells you just how space-time is distorted by mass and energy.
    >
    > A lump of matter stretches space and time. So, for example, clocks run
    > slower in the gravitational field close to Earth than they do far out in
    > space. And if you set a massive lump spinning, it begins to whip space and
    > time around after it, like a rotating teaspoon dragging the foam on a cup
    > of coffee. The denser and faster-moving the matter, the more strongly it
    > distorts space-time.
    >
    > Take this idea far enough, and you find that time can be twisted so much
    > that instead of running in an infinite line from past to future, it is
    > bent into a ring. Follow this loop around, and you return to a particular
    > moment, just as a walk around the block brings you back to your front door.
    >
    > Theoreticians have found some solutions to Einstein's equations that include
    > these "closed time-like loops" -- physicists' jargon for a time machine. The
    > first to do so was the Austrian-born mathematician Kurt Gsdel, in 1949, but
    > unfortunately his solution required the whole Universe to be rotating --
    > which it's not. Decades later Kip Thorne of Caltech came up with the idea
    > of using wormholes, which link different regions of warped space-time, to
    > provide such loops. Other loops can be made by infinitely long, spinning
    > cylinders -- somewhat hard to come by -- or fast-moving cosmic strings. In
    > the early Universe, these ultra-dense strands of matter may have been as
    > common as dirt, but alas, no longer.
    >
    > Mallett's idea of using light is much less outlandish. "People forget that
    > light, even though it has no mass, causes space to bend," he says. Light
    > that has been reflected or refracted to follow a circular path has
    > particularly strange effects. Last year, Mallett published a paper
    > describing how a circulating beam of laser light would create a vortex in
    > space within its circle (Physics Letters A, vol 269, p 214). Then he had a
    > eureka moment. "I realised that time, as well as space, might be twisted by
    > circulating light beams," Mallett says.
    >
    > To twist time into a loop, Mallett worked out that he would have to add
    > a second light beam, circulating in the opposite direction. Then if you
    > increase the intensity of the light enough, space and time swap roles:
    > inside the circulating light beam, time runs round and round, while what
    > to an outsider looks like time becomes like an ordinary dimension of space.
    > A person walking along in the right direction could actually be walking
    > backwards in time -- as measured outside the circle. So after walking for a
    > while, you could leave the circle and meet yourself before you have entered
    > it (see Diagram, http://www.newscientist.com/ns_images/2291/22911F3 . PG).
    >
    > The energy needed to twist time into a loop is enormous, however. Perhaps
    > this wouldn't be a practical time machine after all? But when Mallett took
    > another look at his solutions, he saw that the effect of circulating light
    > depends on its velocity: the slower the light, the stronger the distortion
    > in space-time. Though it seems counter-intuitive, light gains inertia as
    > it is slowed down. "Increasing its inertia increases its energy, and this
    > increases the effect," Mallett says. As luck would have it, slowing light
    > down has just become a practical possibility. Lene Hau of Harvard University
    > has slowed light from the usual 300,000 kilometres per second to just a few
    > metres per second -- and even to a standstill (New Scientist, 27 January,
    > p 4). "Prior to this, I wouldn't have thought time travel this way was a
    > practical possibility," Mallett says. "But the slow light opens up a domain
    > we just haven't had before."
    >
    > To slow light down, Hau uses an ultra-cold bath of atoms known as a
    > Bose-Einstein condensate. "All you need is to have the light circulate in
    > one of these media," Mallett says. "It's a technological problem. I'm not
    > saying it's easy, but we're not talking about exotic technology here; we're
    > not talking about creating wormholes in space."
    >
    > Mallett has already caught the interest of his head of department, William
    > Stwalley, who leads a group of cold-atom researchers. Their first experiment
    > will be designed only to observe the twisting of space, by looking for its
    > effect on the spin of a particle trapped in the light circle. If they can
    > then add a second beam, Mallett believes evidence of time travel will
    > eventually appear. He's not sure how time travel would manifest itself.
    > Perhaps what starts out as a single trapped particle would acquire a
    > partner -- the particle visiting itself from the future.
    >
    > Stwalley is more interested in the practical challenges of the experiment,
    > and remains sceptical about possibilities of time travel. "A time machine
    > certainly seems like a distant improbability at best," he says.
    >
    > Last month, Mallett gave his first talk on the idea at the University of
    > Michigan at the invitation of astrophysicist Fred Adams, who accepts that
    > the theoretical side of Mallett's work stands up to scrutiny. "The reception
    > was cautious and sceptical," Adams admits. "But there were no holes punched
    > in it, either. The solution is probably valid."
    >
    > But even Adams isn't convinced that the experiment will work. That's hardly
    > surprising, as time travel raises disturbing questions. Could you go back
    > and murder your grandparents, making your birth impossible? There may be
    > ways out of this problem (see "Paradox lost" [below]), but most physicists
    > think that any attempt to mess with history should be impossible. The
    > Cambridge astrophysicist Stephen Hawking calls this the "chronology
    > protection conjecture".
    >
    > The general theory of relativity, which Mallett used to work out his theory
    > of time travel, does not take account of quantum mechanics. Could this be
    > the crucial omission that means time machines won't work in the real
    > Universe? Hawking and Thorne say that any time machine would magnify quantum
    > fluctuations in the electromagnetic field, and destroy itself with a beam
    > of intense radiation. But to know for sure, we need a theory of quantum
    > gravity -- a theory that merges quantum theory with relativity.
    >
    > Even Mallett doesn't claim that time travel is definitely within reach.
    > "Whether it will do what I predict is something that one will only know by
    > performing the actual experiment," he says. Then there's the problem of
    > getting on and off the loop of time without destroying it -- or yourself.
    > "I really don't know whether you could use this in the sense of H. G.
    > Wells's time machine," says Mallett.
    >
    > But who knows? In a few years, we may have entered an era when time travel
    > is possible, and all kinds of strange people, things and situations from
    > the future might come to visit. One thing seems certain, though. Even if
    > the Connecticut time machine works, it won't be taking any Yankees back to
    > the court of King Arthur. Mallett's circle of light won't allow anyone to
    > travel back beyond the point where time first formed a closed loop. So it
    > will be impossible to go back to a time before it was set up. "A later
    > person could only travel back to the time when the machine is turned on,"
    > Mallett says. This may explain why we have never been overrun by visitors
    > from the future. It also means that although Mallett might change the
    > Universe, he won't ever achieve his childhood dream. Mallet's father will
    > remain forever beyond his reach.
    >
    >
    > Paradox lost
    >
    > Time travel is littered with paradoxes. The most notorious is the idea of
    > travelling back to the time before your parents were born and killing your
    > grandparents, making it impossible that you would ever exist. And if you
    > didn't exist, you wouldn't be able to travel back, so you wouldn't kill
    > your grandparents, so you would be born after all ... Any influence on the
    > past can lead to self-contradictory logical loops like this.
    >
    > People have dreamed up ways to try to break out of the loop. One is the
    > "consistent histories" approach, which says that you must be somehow
    > forbidden from doing anything that would change the past. However hard you
    > try, something will stop your killing spree. But this is uncomfortably
    > deterministic. In a universe with time travel, should everything be
    > predetermined?
    >
    > Another way out is the "alternative histories" hypothesis. In this idea,
    > you go back to a different history from the one you left. You are free
    > to do anything in this alternate version of history -- killing your
    > grandparents included. It won't change anything in the history where you
    > originated.
    >
    > This has parallels in the "many worlds" interpretation of quantum mechanics,
    > an explanation of how the bizarre quantum laws allow unobserved particles
    > such as atoms and electrons to be in two places at once. Every time an
    > observation forces them to choose one position or another, a new universe
    > is created -- one where they took one position, one where they took the
    > other. So perhaps a time machine would take you into a parallel universe.
    >
    > ###
    >
    > Michael Brooks is a Features Editor at New Scientist
    >
    > New Scientist issue: 19 May 2001
    >
    > PLEASE MENTION NEW SCIENTIST AS THE SOURCE OF THIS STORY AND, IF PUBLISHING
    > ONLINE, PLEASE CARRY A HYPERLINK TO: http://www.newscientist.com
    >
    >
    > --
    > Andrew Yee
    > ayee@nova.astro.utoronto.ca
    >
    >
  • Re:hey... (Score:2, Informative)

    by $uperjay (263648) <jstorrie@ualb[ ]a.ca ['ert' in gap]> on Sunday April 07, 2002 @03:04AM (#3298053) Homepage
    It's because in some theories of time travel, you get younger as you go back. This (sort of) gets around the meeting-yourself problem, as well as not horribly screwing up thermodynamics, because it conserves the amount of matter and energy in the universe (by not making duplicates of you). This has a few implications, if it is true:
    • You and your time machine had better stay put for a while, or you'll end up moving to where you were at the target time when you timetravel.
    • You'd better hope that your time machine is younger than you, or you might time travel to before you were born - and there's not a heck of a lot you can do when you're just a sperm and an egg!
    • You probably won't remember anything, because your brain will return to its prior state when you travel back in time. Bad!
    • Should you go back in time and then scuttle your time machine or otherwise prevent yourself from time-traveling back, icky bad stuff will happen!
    • Finally, since you and everything around you will be exactly as it was at the target time, you probably won't change anything at all - because you won't even know you've gone back in time!
    All these effects, in sum, make time travel pretty useless. S'not a great theory in my boat, actually.
  • by doooras (543177) on Sunday April 07, 2002 @03:04AM (#3298054)
    like Gott [amazon.com]. Great book. Superstrings and all...
  • by rob-fu (564277) on Sunday April 07, 2002 @03:42AM (#3298181)
    There's an interesting article at Howstuffworks here [howstuffworks.com] that discusses how time travel works.

    It discusses some interesting points as to why time travel wouldn't work, including the grandfather paradox, the notion of parallel universes, etc.
  • by gTsiros (205624) on Sunday April 07, 2002 @03:46AM (#3298187)
    ...but only at sub-atomic levels. (i am a physicist)
  • by wagnerer (53943) on Sunday April 07, 2002 @04:48AM (#3298328)
    Pauli exclusion principle.
  • Facts and Theories (Score:5, Informative)

    by sterno (16320) on Sunday April 07, 2002 @05:08AM (#3298391) Homepage
    Fact: Knowledge or information based on real occurrences

    Theory: A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomenon

    You cannot base a fact on a theory, but rather it's the other way around, basing a theory on a fact. Superstring theory is just that, a theory We have, at this point, no practical way to determine the results of time travel since we have no way to time travel (with the possible exception of sitting here and waiting a while).

    While I tend to think superstring theory, from what I understand of it, makes sense, lets not go suggesting that it is in any way a fact. Hopefully in time we will find enough facts to suggest whether it is the correct theory or not.
  • Re:hey... (Score:3, Informative)

    by PhuCknuT (1703) on Sunday April 07, 2002 @07:52AM (#3298690) Homepage
    Until someone has a real working model, this isn't really proof, but the reason that they say you can't go back to before the time machine was built, is that you need a time machine at both ends of the connection. If time travel requires wormholes, and opening one requires a machine at both ends, then it becomes obvious why you can't go back to before the machines exist.
  • Re:Hey Doc (Score:1, Informative)

    by Anonymous Coward on Sunday April 07, 2002 @01:38PM (#3299738)
    Not to mention the 1.21 Gigawatts of Electricity!

    No, that was 1.2 Jiggawatts.
  • -pedantic (Score:2, Informative)

    by Iffy Bonzoolie (1621) <iffy&xarble,org> on Sunday April 07, 2002 @02:22PM (#3299919) Journal
    In line at Back to the Future: The Ride at Universal Studios Hollywood they said 1.2 Jigowatts...

    -If
  • Re:Waves of light (Score:2, Informative)

    by kaiidth (104315) on Sunday April 07, 2002 @02:52PM (#3300025)
    Incidentally, here's the actual paper, the one referred to from the guy's own web site [uconn.edu] (minimal), published in Phys. Lett. A... Gravitational Field of Circulating Light Beams [bio.msu.ru].

    Beware; it's a little drier than the Boston Globe would like to make it...

    I say the actual paper; in fact, this particular paper naturally doesn't make any suggestions of the "Hey, look, this research gives me a way to go back in time and save my father from the evils of cigarettes" type - if it did, it would never have made it into any serious journals. Mallett mentions two papers on his site, one on Bose-Einstein condensation and dark matter, one on this...

    He has done other work - this [esc.edu] , for example, not to mention work on Hawking radiation and probably a bunch of other stuff. His newest one is apparently "Gravitational Perturbations of a Radiating Spacetime" [lanl.gov], which looks relevant, not to mention full of terrifying maths. "The principal aim of our study is to understand how gravitational waves are scattered by a background radiating spacetime".
  • Disappointing (Score:2, Informative)

    by Christopher Danforth (571838) on Sunday April 07, 2002 @05:16PM (#3300647)
    Its too bad the Boston Globe article was the only one posted in this story. It does not go into any detail on his actual ideas. I suggest reading:
    USA Today [usatoday.com]
    ABC News [abc.net.au]
    Mallett's Personal Homepage [uconn.edu]
  • Re:hey... (Score:2, Informative)

    by DavidTC (10147) <slas45dxsvadiv.v ... x.com minus berr> on Sunday April 07, 2002 @08:15PM (#3301255) Homepage
    You need a machine when traveling in the past at both ends because almost all theories work by creating 'closed loops' in time, where you walk from A and to B, five minutes earlier. This is usually done by serious distorting time, by seriously distorting space.

    When walking this path though space that's so distorted you're moving backwards in time, you will eventually reach the point the time machine was built. You won't be able to walk the distorted path anymore, as the distortion will no longer exist past that point.

    A rotating black hole needs to exist at all points in time along the path you're following, or you can't go past that point.

    Or you can use a wormhole, but that doesn't work like Stargate, you have to create both ends of it. The only way to time travel using it is to stick one end of it on a spaceship and travel with it near the speed of light, then bring it back, so the ends exit at near the same point in space but in different points in time. (Aka, the twins paradox, but this time it can cause a real paradox.) There you don't even get to pick your destination, you can only walk back and forth between two 'fixed' times, seperated by a fixed difference. It would be a 'time bridge' connecting two different time.

    You could exit the 'past' exit and walk back in the 'future' exit and end up further back, but eventually you'll end up on a ship going near the speed of light, with the 'future' exit back on earth, and have no choice but to re-enter the 'past' exit, or hang around on the ship for a bit waiting to get back to earth so you can enter the 'future' exit and relive the exact same trip, but with more company this time.

    Even if you figured out some way of moving one end though time faster than the other yet keep it on earth, you still would eventually get to the point that the ends were .0001 seconds apart, and you couldn't travel between them that fast. (Especially with all the other people from the past and future trying the exact same stunt. It's the ultimate First Post!)

    The invention in the article seems to be based on 'black holes', or at least the optical illision of one. You can't send anything back past the point that the machine is powered up, as past that point the neutron will just follow a normal path though space and time, not the specially distorted one.

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