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Title: New model 'permits time travel'
Source:
bbc
URL Source: http://news.bbc.co.uk/go/pr/fr/-/2/hi/scie...ure/4097258.stm
Published: Jun 18, 2005
Author: By Julianna Kettlewell
Post Date: 2005-06-18 08:12:30 by gengis gandhi
Keywords: permits, travel, model
Views: 173
Comments: 4
BBC NEWS New model 'permits time travel' By Julianna Kettlewell BBC News science reporter If you went back in time and met your teenage parents, you could not split them up and prevent your birth - even if you wanted to, a new quantum model has stated. Researchers speculate that time travel can occur within a kind of feedback loop where backwards movement is possible, but only in a way that is "complementary" to the present. In other words, you can pop back in time and have a look around, but you cannot do anything that will alter the present you left behind. The new model, which uses the laws of quantum mechanics, gets rid of the famous paradox surrounding time travel. Paradox explained Although the laws of physics seem to permit temporal gymnastics, the concept is laden with uncomfortable contradictions. The main headache stems from the idea that if you went back in time you could, theoretically, do something to change the present; and that possibility messes up the whole theory of time travel. Clearly, the present never is changed by mischievous time-travellers: people don't suddenly fade into the ether because a rerun of events has prevented their births - that much is obvious. You go back to kill your father, but you'd arrive after he'd left the room, you wouldn't find him, or you'd change your mind Professor Dan Greenberger, City University, New York So either time travel is not possible, or something is actually acting to prevent any backward movement from changing the present. For most of us, the former option might seem most likely, but Einstein's general theory of relativity leads some physicists to suspect the latter. According to Einstein, space-time can curve back on itself, theoretically allowing travellers to double back and meet younger versions of themselves. And now a team of physicists from the US and Austria says this situation can only be the case if there are physical constraints acting to protect the present from changes in the past. Weird laws The researchers say these constraints exist because of the weird laws of quantum mechanics even though, traditionally, they don't account for a backwards movement in time. Quantum behaviour is governed by probabilities. Before something has actually been observed, there are a number of possibilities regarding its state. But once its state has been measured those possibilities shrink to one - uncertainty is eliminated. So, if you know the present, you cannot change it. If, for example, you know your father is alive today, the laws of the quantum universe state that there is no possibility of him being killed in the past. It is as if, in some strange way, the present takes account of all the possible routes back into the past and, because your father is certainly alive, none of the routes back can possibly lead to his death. "Quantum mechanics distinguishes between something that might happen and something that did happen," Professor Dan Greenberger, of the City University of New York, US, told the BBC News website. "If we don't know your father is alive right now - if there is only a 90% chance that he is alive right now, then there is a chance that you can go back and kill him. "But if you know he is alive, there is no chance you can kill him." In other words, even if you take a trip back in time with the specific intention of killing your father, so long as you know he is happily sitting in his chair when you leave him in the present, you can be sure that something will prevent you from murdering him in the past. It is as if it has already happened. "You go back to kill your father, but you'd arrive after he'd left the room, you wouldn't find him, or you'd change your mind," said Professor Greenberger. "You wouldn't be able to kill him because the very fact that he is alive today is going to conspire against you so that you'll never end up taking that path leads you to killing him." Story from BBC NEWS: http://news.bbc.co.uk/go/pr/fr/-/2/hi/scie...ure/4097258.stm Published: 2005/06/17 10:03:47 GMT
Poster Comment: the Philadelphia experimaent guys claim the USN did time travel back in the 40's and later at Montauk Point in the 80's. I've wondered if ancient accounts of 'gods' were not necessarily from the stars, but from the future, as our 'defenders' try to manipulate the time string for 'national security' purposes. according to lore, in the 80's there was a big problem at Montauk where they had to go back to the forties and smash up the generator there. who knows? but those internet nuts have been talking about time travel for a while, now, here it is in the news as 'possible'... since the tech we have is always decades behind what's available, it makes one wonder.
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#1. To: gengis gandhi (#0)
My Microwave is a time machine that takes my leftovers back to the time they were hot.
 | So many morons, so few bullets. |
#2. To: gengis gandhi, TommyTheMadArtist (#1)
In the meantime, it makes for good novels. My Microwave is a time machine that takes my leftovers back to the time they were hot.since the tech we have is always decades behind what's available, it makes one wonder.
LOL!
"Somebody sends me a blue dress and some DNA, I'll have an investigation" Porter Goss, regarding Valerie Plame leak, October 2003 [The Herald Tribune]
Vietnam Rag
#3. To: gengis gandhi (#0)
I'd be more inclined to believe the multiple universe theory of time travel than this one.
#4. To: orangedog (#3)
ever read The Holographic Universe. Pretty good.
Whenever people ask me, 'hey, you know what you should do? I always say 'What? Buy a monkey?'
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