# Can the present affect the past?



## Urien (Mar 18, 2007)

Discussion and experiments on sending messages back, a short distance/time/both? 

Intriguing stuff. 

Science hopes to change events that have already occurred


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## mosaix (Mar 18, 2007)

I liked this bit:

_If all that gives you a headache,

_I followed it so far but I don't pretend to understand most of it. I find it easier if there are some diagrams.

Fascinating stuff AVS.


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## chrispenycate (Mar 18, 2007)

We discussed this in
http://www.chronicles-network.com/f...-experiment-may-prove-the-possibility-of.html
and I'm still not convinced that it's any further than a thought experiment - have they even tried the "at the same time" experiment? Can a laser (a cascade effect) be made to deliver individual photons? can an optical splitter divde a stream of these photons into two, while getting quantum entanglement between the wavicules? Does not  the fact of determining whether the "early" beam - non not even a beam, since if we have enough photons to form a beam we know we'll get interference effects, even if their behaving like particles - early _stream_ is reacting as a wave or a particle (assuming that there is actually a difference rather than merely a conceptual difficulty on thr behalf of the theorists) be enough of an "observer" phenomenon to collapse the vector before the later one could react?
Even if I didn't suspect that the difference betwwen a "wave" photon and a "particle" photon was a conceptual problem rather than something that can trully be measured, there are too many "well, it ought to work like this if…" conditions in that article.


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## Dave (Mar 19, 2007)

I remember that thread. When I read the detail on the experiement it didn't seem to me that anything was travelling back in time at all, rather it was delaying some packet of information behind, in the same way that you can do 'The Wire' confidence trick as demonstated in the Paul Newman/ Robert Redford film _The Sting_.

The faster information packet already knew the outcome of the delayed information packet, but it isn't time travel, just a big con!


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## Admiral Ryouhei (Mar 20, 2007)

If we went back in the future to change the past, the changes are already manifest and cannot be changed from the path they've taken except in an alternate probability (divergant time-stream)

basically, if you went into the past to kill hitler, you'd probably get killed trying or reach him at his moment of suicide, so it wouldn't matter if you killed him then or not

and if you found yourself in a position in which to change a major course of events, something would happen to prevent the change, or you'd get a psychic premonition of what the change would be and decide better of it

or your change would simply have no effect and someone or something (alien impersonators preserving the time stream) would replace what was removed or changed

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IF you did effect a change that altered the course of events, you would have to be unaffected and go back and perform the same actions and changes that changed the future, or this time-stream would be caught in a paradox loop and would cease to exist after the history changed, spring into being as it went back to normal again and you went back and repeated the loop again

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however I find the all things that have happened in the past, whether by nature or future fouling, are how they are and cannot be changed, but someone will go back, if they do, to change something in the past and ensure that the past remains as it is

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is time imutable? I don't know

if it is then there has to be something there to protect against meddling or we might not be here because someone would have come from the future to change the past for good or ill and done something to destroy existance as we know it

personally I'm not worried


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## Interference (Aug 27, 2007)

Time is mutable.  Mess it up all you like, the only thing it's likely to affect is a whole bunch of humans who were making a mess of their own lives, anyway.  The Universe is _certainly not_ going to suffer much if Hitler wins the war or whatever.  So go on, morons.  **** around with time as well, why don't you?  Just don't hurt the dolphins.


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## gully_foyle (Aug 27, 2007)

One wonders what sort of applications can be found for sending photons microseconds back into the past. But then, cathode rays probably looked pretty useless once upon a time.


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