# Time Travel: Science hopes to change events that have already occurred



## Whitestar (Apr 10, 2007)

Here's an article on the subject of time travel/retrocausality. Its a quite an interesting read:

Ever wish you could reach back in time and change the past? Maybe you'd like to take back an unfortunate voice mail message, or rephrase what you just said to your boss. Or perhaps you've even dreamed of tweaking the outcome of yesterday's lottery to make yourself the winner.

Common sense tells us that influencing the past is impossible -- what's done is done, right? Even if it were possible, think of the mind-bending paradoxes it would create. While tinkering with the past, you might change the circumstances by which your parents met, derailing the key event that led to your birth.

Such are the perils of retrocausality, the idea that the present can affect the past, and the future can affect the present. Strange as it sounds, retrocausality is perfectly permissible within the known laws of nature. It has been debated for decades, mostly in the realm of philosophy and quantum physics. Trouble is, nobody has done the experiment to show it happens in the real world, so the door remains wide open for a demonstration.

It might even happen soon. Researchers are on the verge of experiments that will finally hold retrocausality's feet to the fire by attempting to send a signal to the past. What's more, they need not invoke black holes, wormholes, extra dimensions or other exotic implements of time travel. It should all be doable with the help of a state-of-the-art optics workbench and the bizarre yet familiar tricks of quantum particles. If retrocausality is confirmed -- and that is a huge if -- it would overturn our most cherished notions about the nature of cause and effect and how the universe works.

Dating back to Newton's laws of motion, the equations of physics are generally "time symmetric" -- they work as well for processes running backward through time as forward. The situation got really strange in the early 20th century when Einstein devised his theory of relativity, with its four-dimensional fabric of space-time. In this model, our sense that history is unfolding is an illusion: The past, present and future all exist seamlessly in an unchanging "block" universe.

"If you have the block universe view, the future and the past are not any different, so there's no reason why you can't have causes from the future just as you have causes from the past," says David Miller of the Centre for Time at the University of Sydney in Australia.

With the advent of quantum mechanics in the 1920s, the relative timing of particles and events became even less relevant. "Real temporal order in general, for quantum mechanics, is not important," says Caslav Brukner, a physicist at the University of Vienna, Austria. By the 1940s, researchers were exploring the possibility of time-reversed phenomena. Richard Feynman lent credibility to the idea by proposing that particles such as positrons, the antimatter equivalent of electrons, are simply normal particles traveling backward in time. Feynman later expanded this idea with his mentor, John Wheeler of Princeton University. Together they worked out a theory of electrodynamics based on waves traveling forward and backward in time. Any proof of reverse causality, however, remained elusive.

Fast forward to 1978, when Wheeler proposed a variation on the classic double-slit experiment of quantum mechanics. Send photons through a barrier with two slits in it, and choose whether to detect the photons as waves or particles. If you put up a screen behind the slits, you will get a pattern of light and dark bands, as if each photon travels through both slits and interferes with itself, like a wave. If, on the other hand, you take a snapshot of the slits themselves, you will find each photon passes through one slit or the other: it is forced to pick a path, like a particle. But, Wheeler asked, what if you wait until just after the photon has passed the slits to make your choice? In theory, you could suddenly raise the screen to expose two cameras behind it, one trained on each slit. It would seem that you can affect where the photon went, and whether it behaved like a wave or particle, after the fact.

In 1986, Carroll Alley at the University of Maryland at College Park, found a way to test this idea using a more practical set-up: an interferometer which lets a photon take either one path or two after passing through a beam splitter. Sure enough, the photon's path depended on a choice made after the photon had to "make up its mind." Other groups have confirmed similar results, and at first blush this appears to show the present affecting the past. Most physicists, however, take the view that you can't say which path the photon took before the measurement is made. In other words, still no unambiguous evidence for retrocausality.

That's where John Cramer comes in. In the mid-1980s, working at the University of Washington in Seattle, he proposed the "transactional interpretation" of quantum mechanics, one of many attempts to relate the mathematics of quantum theory to the real world. It says particles interact by sending and receiving physical waves that travel forward and backward through time. In June, at a conference of the American Association for the Advancement of Science, Cramer proposed an experiment that can at last test for this sort of retrocausal influence. It combines the wave-particle effects of double slits with other mysterious quantum properties in an all-out effort to send signals to the past.

The experiment builds on work done in the late 1990s in Anton Zeilinger's lab, when he was at the University of Innsbruck, Austria. Researcher Birgit Dopfer found that photons that were "entangled", or linked by their properties such as momentum, showed the same wave-or-particle behavior as one another. Using a crystal, Dopfer converted one laser beam into two so that photons in one beam were entangled with those in the other, and each pair was matched up by a circuit known as a coincidence detector. One beam passed through a double slit to a photon detector, while the other passed through a lens to a movable detector, which could sense a photon in two different positions.

The movable detector is key, because in one position it effectively images the slits and measures each photon as a particle, while in the other it captures only a wave-like interference pattern. Dopfer showed that measuring a photon as a wave or a particle forced its twin in the other beam to be measured in the same way.

To use this setup to send a signal, it needs to work without a coincidence circuit. Inspired by Raymond Jensen at Notre Dame University, Cramer then proposed passing each beam through a double slit, not only to give the experimenter the choice of measuring photons as waves or particles, but also to help track photon pairs. The double slits should filter out most unentangled photons and either block or let pass both members of an entangled pair, at least in theory. So a photon arriving at one detector should have its twin appear at the other. As before, the way you measure one should affect the other. Jensen suggested that such a setup might let you send a signal from one detector to another instantaneously -- a highly controversial claim, since it would seem to demonstrate faster-than-light travel.

If you can do that, Cramer says, why not push it to be better-than-instantaneous, and try to make the signal arrive before it was sent? His extra twist is to run the photons you choose how to measure through several kilometers of coiled-up fiber-optic cable, thereby delaying them by microseconds. This delay means that the other beam will arrive at its detector before you make your choice. However, since the rules of quantum mechanics are indifferent to the timing of measurements, the state of the other beam should correspond to how you choose to measure the delayed beam. The effect of your choice can be seen, in principle, before you have even made it.

That's the idea anyway. What will the experimenters actually see? Cramer says they could control the movable detector so that it alternates between measuring wave-like and particle-like behavior over time. They could compare that to the pattern from the beam that wasn't delayed and was recorded on a sensor from a digital camera. If this consistently shifts between an interference pattern and a smooth singleparticle pattern a few microseconds before the respective choice is made on the delayed photons, that would support the concept of retrocausality. If not, it would be back to the drawing board.

If the experiment does show evidence for retrocausation, it would open the door to some troubling paradoxes. If you could see the effects of your choice before you make it, could you then make the opposite choice and subvert the laws of nature? Some researchers have suggested retrocausality can occur only in limited circumstances in which not enough information is available for you to contradict the results of an experiment.

Another way to resolve this is to say that even if the present can influence the past, it cannot change it. The fact that your hair is shorter today has as much influence on your going to the barber yesterday as the other way around, yet you can't change that decision. "You wouldn't be able to talk about altering, but you could talk about causing or affecting," says Phil Dowe, an expert on causation at the University of Queensland in Australia. While it would mean we cannot change the past, it also implies that we cannot change the future.

If all that gives you a headache, then consider this: if retrocausality does exist, it says something profound about how the universe works. "It has the potential to solve what is one of the biggest problems in modern physics," says Huw Price, head of Sydney's Centre for Time. It goes back to quantum entanglement and "nonlocality" -- one particle instantaneously affecting another, even from the other side of the galaxy. That doesn't sit well with relativity, which states that nothing can travel faster than light. Still, the latest experiments confirm that one particle can indeed instantaneously affect the other. Physicists argue that no information is transmitted this way: Whether the spin of a particle is up or down, for instance, is random and can't be controlled, and thus relativity is not violated.

Retrocausality offers an alternative explanation. Measuring one entangled particle could send a wave backward through time to the moment at which the pair was created. The signal would not need to move faster than light; it could simply retrace the first particle's path through space-time, arriving back at the spot where the two particles were emitted. There, the wave can interact with the second particle without violating relativity. "Retrocausation is a nice, simple, classical explanation for all this," Dowe says.

While Cramer last week prepared to start a series of experiments leading up to the big test of retrocausality, some researchers expect reverse causality will play an increasingly important role in our understanding of the universe. "I'm going with my gut here," says Avshalom Elitzur, a physicist and philosopher at Bar-Ilan University in Israel, "but I believe that when we finally find the theory we're all looking for, a theory that unifies quantum mechanics and relativity, it will involve retrocausality."

But if it also involves winning yesterday's lottery, Cramer won't be telling. 
Did we reach back to shape the Big Bang?

If retrocausality is real, it might even explain why life exists in the universe -- exactly why the universe is so "finely tuned" for human habitation. Some physicists search for deeper laws to explain this fine-tuning, while others say there are millions of universes, each with different laws, so one universe could quite easily have the right laws by chance and, of course, that's the one we're in.

Paul Davies, a theoretical physicist at the Australian Centre for Astrobiology at Macquarie University in Sydney, suggests another possibility: The universe might actually be able to fine-tune itself. If you assume the laws of physics do not reside outside the physical universe, but rather are part of it, they can only be as precise as can be calculated from the total information content of the universe. The universe's information content is limited by its size, so just after the Big Bang, while the universe was still infinitesimally small, there may have been wiggle room, or imprecision, in the laws of nature.

And room for retrocausality. If it exists, the presence of conscious observers later in history could exert an influence on those first moments, shaping the laws of physics to be favorable for life. This may seem circular: Life exists to make the universe suitable for life. If causality works both forward and backward, however, consistency between the past and the future is all that matters. "It offends our common-sense view of the world, but there's nothing to prevent causal influences from going both ways in time," Davies says. "If the conditions necessary for life are somehow written into the universe at the Big Bang, there must be some sort of two-way link." -- Patrick Barry 

Retrocausality: Can the present affect the past?
Researchers have devised an experiment using laser light to demonstrate a property of quantum mechanics: That pairs of entangled photons show identical properties as either a wave or a particle. By using this knowledge, they hope to demonstrate how to influence an event that has already occurred.

1. A laser beam is directed into a crystal that makes two streams of photons.

2a. One stream of photons travels through a screen with two slits.

2b. The other stream of photons travels through an identical screen with two slits BUT is routed through six miles of fiber-optic cable that delays the light by microseconds.

3a. A detector captures the light and records it as a wave-like or particle-like photon (you don't know which yet).

3b. The delayed light is sensed by a movable detector. If the detector is closer to the lens it's recorded as a wave-like interference pattern. If its farther from the lens it is recorded as a particle.

What is happening here: By choosing to measure the delayed photon as either a wave or particle photon, the experimenter forces the other photon to appear in the same way - because they are entangled - even though it reaches the detector earlier.
Sources: John Cramer, University of Washington; NewScientist, Sept. 2006

And here is the link:

Science hopes to change events that have already occurred

Fascinating, isn't it?


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## Dave (Apr 10, 2007)

This is about the third thread on this. The research was done last year. This thread was the last one on it:
http://www.chronicles-network.com/forum/36529-can-the-present-affect-the-past.html

As I said before, I don't think that is 'Time Travel' at all. That is slowing down one packet information that is linked to another packet, then determining the first from the second before the first arrives. Nothing at all has gone back in time.


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## Pyan (Apr 10, 2007)

And it was envisioned by Bob Shaw in *1968*! There ain't nothing new under the sun.

Slow Glass (Scenedow) by Bob Shaw from Light of Other Days


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## TheMoirae (May 14, 2009)

Just joined this website a little while ago and came across this thread. Cool stuff. Any update on these experiments? I happen to be a believer in the ability to travel back in time to affect the past, but certainly not change it.


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## Ursa major (May 14, 2009)

TheMoirae said:


> I happen to be a believer in the ability to travel back in time to affect the past, but certainly not change it.


 
Unless I've missed something - this, sadly, isn't unknown - I don't think that you can affect something without changing it in some way.


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## AE35Unit (May 14, 2009)

People often say time travel may not be possible now but one day it will be. My answer has always been,if that is true then where are all the tourists?


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## Moonbat (May 14, 2009)

> where are all the tourists?


 
Amongst us, acting as everyday citizens. In fact statistically someone you know if from the future!


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## AE35Unit (May 14, 2009)

Moonbat said:


> Amongst us, acting as everyday citizens. In fact statistically someone you know if from the future!



Hmmm some might say you been reading too much sci fi  
Hmmm an interesting aside, do you have to believe in the stuff you read about?


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## Dave (May 14, 2009)

Moonbat said:


> Amongst us, acting as everyday citizens. In fact statistically someone you know if from the future!



Hello Moonbat, I knew I'd once met you somewhere again!

Is this spinning off into a general time travel discussion, because that's fine with me, but I still don't believe that the experiment in the original post proves anything. It is like the Con Trick in the 'The Sting' called the 'Wire'. It is about slowing down Time not reversing it. General Relativity predicts that time can be slowed down or sped up with respect to an observer, I don't think we will ever be able to go back in time.


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## Saeltari (May 14, 2009)

I wouldn't worry about it. There is no paradox, each universe is part of an infinite possibilities and changing what is our past does not change this now it only brings into being another now that was probably already there to begin with.


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## TheMoirae (May 15, 2009)

Ursa major said:


> Unless I've missed something - this, sadly, isn't unknown - I don't think that you can affect something without changing it in some way.


 
Sure you could.  Do we really know for sure why John Wilkes Booth killed JFK?  I propose a stranger met with Booth and suggested to him that it was the right thing to do.  I further propose that this stranger was a time traveler.  Based on the time traveler's argument, Booth decided to kill JFK.  What changed?  Nothing.  But, the time traveler affected the past by convincing Booth to kill JFK.


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## Ursa major (May 15, 2009)

TheMoirae said:


> Do we really know for sure why John Wilkes Booth killed JFK?


 
I'm guessing that it was because killing just the one US President wasn't enough for someone as old (and dead) as him? 



TheMoirae said:


> I propose a stranger met with Booth and suggested to him that it was the right thing to do. I further propose that this stranger was a time traveler. Based on the time traveler's argument, Booth decided to kill JFK. What changed? Nothing. But, the time traveler affected the past by convincing Booth to kill JFK.


 
Now if you're suggesting that this time traveller took Booth from the 19th Century and had him shoot JFK at the same time that Lee Harvey Oswald did - then there would make no difference to JFK (who would still be dead), but might give a different result of the forensic examination (assuming that they fired their guns at the same time and neither missed). There would probably be a better-founded conspiracy theory; who knows what changes this might lead to.


But if you're confusing Booth with Oswald, then there was quite a big change: JFK's death.


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## TheMoirae (May 16, 2009)

Ursa major said:


> I'm guessing that it was because killing just the one US President wasn't enough for someone as old (and dead) as him?
> 
> 
> 
> ...


 
I guess all that time travel has scrambled my brain a little.  The time traveler convinced Oswald to kill JFK.  No change occured, only our understanding of what actually happened.  We thought Oswald acted on his own--in reality, he acted due to the influence of the time traveler.


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## ManTimeForgot (May 16, 2009)

Except for the fact that the influence of this time traveler will be felt elsewhere since Oswald's behavior will/would have change(d) from what it would be like uninfluenced.  It might only be a small change, but a small change is _not_ equal to no change.

Looking at the end result of an event is not the same as no change.  Just because Oswald still ends up killing JFK doesn't mean no change occurred.  Oswald might talk with his wife more and then end up getting into position 1 second later.  I stress might because there is no way to know how time will be effected.

This is why time travel is such a dangerous prospect; I would never advocate its use if the future could be affected by its use.  There are simply too many variables.  What if seeing you (the time traveler) makes someone 1 second late to their job which makes someone not see you in time to stop making a decision which does X which does Y... and so an so forth until you get a bad outcome.  Maybe things improve for the better; maybe they don't.  It would be hubris to assume you could predict all the possible outcomes.

MTF


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## Urlik (May 16, 2009)

look at the Lee Harvey Oswald case a little differently (why do assassins have 3 part names? John Wilkes Booth, Mark David Chapman).
in our timeline, JFK has been assassinated so there is no need to go back and convince LHO to pull the trigger. from our point of view, he already has.
so suppose we go back to convince him not to kill JFK, will Kennedy be alive or will the real gunman be on the grassy knoll all along?

changing an event is like moving a stone in a river. it will cause a few ripples locally but the river will continue to flow along its course pretty much unchanged


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## Dave (May 16, 2009)

Urlik said:


> why do assassins have 3 part names?


OMG! I have two forenames. In the future I will be sent back as an assassin!

But seriously, very small events can and often do have far reaching consequences.


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## TheMoirae (May 16, 2009)

Urlik said:


> look at the Lee Harvey Oswald case a little differently (why do assassins have 3 part names? John Wilkes Booth, Mark David Chapman).
> in our timeline, JFK has been assassinated so there is no need to go back and convince LHO to pull the trigger. from our point of view, he already has.
> so suppose we go back to convince him not to kill JFK, will Kennedy be alive or will the real gunman be on the grassy knoll all along?
> 
> changing an event is like moving a stone in a river. it will cause a few ripples locally but the river will continue to flow along its course pretty much unchanged


 
You are all sort of missing the point.  An event in time only happens once--therefore, it cannot be changed.  It is as simple as that.  Did Oswald kill JFK because he was simply cranky that day, because he felt hate toward JFK, because he thought killing JFK would somehow end the world, or because a time traveller convinced him it was the right thing to do?  I have no idea, but one possibility is that a time traveller convinced him (if, it is actually possible to travel back in time).  If that is, indeed, the case, then the time traveller affected the past by taking part in Oswald's decision.  But, the time traveller did not change the past because it simply cannot be changed.  Oswald killed JFK and did so through a certain course of actions and decisions and this sequence happens once and only once.  Read "Time Machines" by Paul J Nahin if you'd like a very clear explanation of this concept (and my book if you'd like a nice fictional tale of this concept in play).


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## Urlik (May 17, 2009)

TheMoirae said:


> You are all sort of missing the point. An event in time only happens once--therefore, it cannot be changed. It is as simple as that.


 
you missed the point as well as that is basically what I said.
rather than going back to convince Oswald to kill JFK (which wouldn't be changing the past as from our point of view he did and so doesn't need convincing) our time traveller goes back to stop Oswald and, as the conspiracy theorists believe, Oswald doesn't take a rifle to the book repository but there is a gunman on the grassy knoll.
Oswald gets falsly accussed of the assassination and is subsequently shot by Ruby and nothing has really changed.

move a pebble in a stream and you'll cause ripples but the stream will flow on with no significant change.

go back to prehistoric times and kill the first fish to crawl out of the sea and develope rudimentary lungs and nothing will change.
1 fish doing that wouldn't be enough for evolution to work.
it was many fish doing this either to avoid predators or find other sources of food that caused land animals to evolve. 
many would have died every day anyway, so our time traveller killing one more would have zero long term consequences


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## ManTimeForgot (May 23, 2009)

That is hubris Urlik.  No long term consequences?!!!  How the hell would you know?  How do you know that because that person stopped Oswald by taking him to a bar and talk him down that Jackie didn't talk to Jane about Fred who didn't marry her who didn't have david as a kid who was the great great grandsire of the reincarnation of Einstein who invents inverse quantonium physics and devises the solution to world peace?


You Don't!  That's why time travel is so mind-bogglingly dangerous.  And that whole stone in the stream metaphor is wrong in its inception too.  Its more like throwing multiple stones in succession into a stream with a weak flow.  Throw those stones in the right order and their cumulative ripple effect can create eddies or whirlpools or even reverse the flow for a limited period of time.  Sure throw those stones in at random and in all likelihood you don't change much of anything, but throw them in in such a way as to make their effects support each other (mathematics is a cruel but exacting mistress) and you can make all sorts of alterations.


Plus the whole "stream" metaphor seriously downplays just how dangerous even "one stone" could be in the metaphor.  Throw even one stone in the stream and somewhere far down the stream a milliliter of water less than what would normally be able to be absorbed by a plant is allowed to be absorbed.  That plant then goes on to die later during the dry season as it was already going to be on the edge of survival anyway.  That plant in this metaphor is some human in the future of humanity (where the future is down stream).  The problem with this is how important is this plant?  Well for earth's ecosystem not very.  But when it comes to the future of humanity *How in the bloody hell are we supposed to know how important one random single life is going to be?!!!*

The butterfly effect is _NOT_ a joke.

MTF


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## Interference (May 23, 2009)

(Calm down, MTF  )

No single event in history is of any importance whatsoever except to the people/creatures directly affected.  Our history can be changed in any number of ways without fundamentally affecting the course of Universal history.  We can only make a difference to each other.

That said, is it right to meddle with the past?

This is an ecumenical question 

If human existence has any purpose whatever, it may perhaps be to make this, truly, the best of all possible worlds.  Just as a writer will edit his manuscript, even rewriting entire chapters, to produce the best manuscript he possibly can, I see no reason why, once time manipulation has been perfected, we shouldn't do our damnedest to tinker about with history until we have achieved Utopia.

Is it happening now?

Why, yes, absolutely and categorically, time manipulation is happening every second of every aeon.  Why don't we notice it?  Because our lives are too short and insignificant to matter in the long-run.


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## Ursa major (May 23, 2009)

There's at least one flaw in that argument, Interference: us. (Well, the rest of you, anyway. ) Humans are far from perfect, making mistakes with their lives and those of others; and that's just in real time. Giving ourselves the power to muck about with history? Utopia is the last thing we'd get. And that's if those doing the work have the highest moral values - a moral compass, of you like - which some of them won't.

And if you still need to be convinced, just imagine what would happen if a company like EDS or Capita won the contract to create this utopia. One can just imagine how many aeons these projects would be behind time if all eternity was available for their implementation. (That's what PFI means, by the way: Perfect Future Impossible.)





Note: If you don't know what PFI is, with respect to the UK economy (why does that word seem so wrong on this context), think yourself lucky.


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## Interference (May 23, 2009)

At least, Ursa, only humanity will be affected.  The Universe and even the planet will outlive any and all of our shenanigans and emerge fundamentally (think infinite, think eternal) undamaged.

Richard Dawkins contends that whether there is a God or not, the world would still be as we know it now.  I suspect that whether Time Manipulation occurs or not, pretty much the same thing can be said.

(of course, if I may extend the writiing/editing analogy a little further, the point you have raised would not be unlike the American sit-com method of sit-com writing, where decisions are made in script meetings - and we all know the wonders that this system can produce )


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## dustinzgirl (May 23, 2009)

Here's a scary thought. What if we have already changed history, and this was the best possible outcome? What if the original true line was Nazi's taking over the world, or Stalin, or any other more terrible combination of events? What if the Vietnam war was a better outcome than say, global nuclear holocaust?


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## Interference (May 23, 2009)

Such thoughts help me sleep nights, Dusty


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## dustinzgirl (May 23, 2009)

Interference said:


> Such thoughts help me sleep nights, Dusty



This should keep you up then:

If there really are parallel dimensions and/or timelines, and time is linear and not circular (although I lean towards the infinity perspective) and in our world this is the best possible outcome, that would mean several things:

First, the fabrics of time/space reality are not as thick as we would hope.
Secondly, other worlds with Nazi monsters would also have the same technology (basing on the heroic theory of invention, or in an alternate timeline, the anti-heroic theory of invention, which would actually still be the heroic theory of invention depending on their social constructs of heroism).
Thirdly, if this was the best possible outcome, don't you think we are pretty much screwed as humans? 
Fourthly, how long until the Stalin-Nazi-Monster-NukeMutants get through the already thinning fabrics of time/space, and what might they carry with them?

I just wrote like, eight books in four sentences. I should totally get a Pulitzer. Or putzier. Whatever.


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## Interference (May 23, 2009)

Then, next time around, the situation will reverse.


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## dustinzgirl (May 23, 2009)

Interference said:


> Then, next time around, the situation will reverse.



Now that's an interesting thought. If time/space is continuous and therefore cyclic (since a straight line in a round universe can't go on forever, although maybe in another universe it could), and then there would be a certain point along the cycle of infinity where the end and beginning meet up, what would happen? The big bang, perhaps? Did our universe, as we know it, begin because another universe met its end/begin time/space point, and explode, and our physical universe, as long-lived as we think it is, is just a tiny point of explosion or expansion on a massive scale of time/space?


These are the things I think about when I'm supposed to be sleeping. Although right now I'm supposed to be cleaning. Ah, procrastination, how I love thee.


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## Urlik (May 23, 2009)

MTF, yes you can argue that a small change can have a large effect, but time/history doesn't work like that.
there isn't one single causal chain of events that flows through time.

go back to the Devonian time and kill that first fish to crawl onto the mud flats.
would that be the end of life as we know it?
no, there wasn't just 1 fish. there had to be loads of them or they couldn't have bred and, over many generations, evolved into land creatures.
ok let's use a different example.
how different would life today be if Einstein was removed from our history before he got to work on relativity?
it probably wouldn't be much different except there wouldn't be the posters of Albert sticking his tongue out. 
other mathematicians and physicists (like Hendrik Lorentz or Henri Poincaré or Hermann Minkowski) would have worked it out.
remove James Watt from history and we would still have had steam engines.
history isn't a single causal chain.
you can't point to a single event in history as the single cause.
the assassination of Franz Ferdinand wasn't the single cause of WWI. it may have been the trigger but all the major powers in Europe were preparing for the war from at least as early as 1906 and the major alliances were in place by 1907. if Ferdinand hadn't been assassinated, something else would have sparked the conflict because it wasn't one single event that led up to it


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## Dave (May 23, 2009)

Urlik - there is something in your arguments but not as you present them.

There was not "loads" of fish surviving on the mudflats, but just one with a dominant gene that was able to reproduce because the others died. That is not to say that the same mutation would not re-occur again, but it might occur in a different species of fish, and so lead to completely different kinds of amphibians. You must have heard of the parallel evolution of marsupials and placentals where surprisingly similar animals have often emerged in two or three of the separated continents. So, something like man might have evolved but it would not be exactly the same, (we might have ancestors who were horses!)

With scientific discoveries again it is true that one cannot consider the development of any particular piece of the modern world in isolation. There was a BBC series called _Connections_ in which James Burke examined this and as Wikipedia says about it: "Rather, the entire gestalt of the modern world is the result of a web of interconnected events, each one consisting of a person or group acting for reasons of their own (e.g., profit, curiosity, religious) motivations with no concept of the final, modern result of what either their or their contemporaries' actions finally led to."

So, you are correct that if Einstein had not developed his theories of Relativity, or James Watt his engine, then it would be left to someone else, and that the time was just right for someone to do those things. However, the events would still unfold in a slightly different way, and however small that difference was to begin with, it would still make a huge change because of that "Butterfly Effect" already mentioned and more properly termed *Chaos Theory*.

Exactly the same would apply to your third example. The European Powers had been preparing for War for all kinds of reasons, and Navies and Armaments had been built up from the turn of the Century. However, the behaviour of dynamical systems is extremely sensitive to the initial conditions set, and very small changes in initial conditions lead to wide differences in the final outcomes. This sensitivity over the initial conditions manifests itself as an exponential growth of the perturbations. A World War would surely have taken place, but other than that, you cannot predict any outcome.



dustinzgirl said:


> What if the original true line was Nazi's taking over the world...


PK Dick's _Man in the High Castle_.

Speaking of cycles, just as Communism in the Soviet Union collapsed, I'm quite sure that, had the Nazis won the Second World War, by the present time the Super State that resulted would now have fallen apart and Nationalism been replaced by something less extreme. Hitler would probably have been assassinated shortly after they won the war. Jews, Gypsies and homosexuals would have continued to have been exterminated until those criminally insane he had in positions of power were removed. We would however, have scheduled Rocketship flights traveling from Europe to North America.


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## Interference (May 24, 2009)

If the original question is to do with history, then all you've said is perfectly valid, Dave.  If to do with Time, on the other hand, then history becomes irrelevant and swallowed up by eternity.  Time is bigger than our brief experience of it.


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## Urlik (May 24, 2009)

Dave 


> There was not "loads" of fish surviving on the mudflats, but just one with a dominant gene that was able to reproduce because the others died.


 
when I said loads, I meant loads of the same species (and probably from the same generation as they would have all developed the same variation, amongst others, at the same time during formation in the egg) made use of this to escape predation or to find new sources of food or a less hostile environment and survived.
it would have been miraculous if there was just the one "grandfather" fish that abandoned the seas and went to live a solitary life on dry land to have established a breeding population.
due to the way that chaperone proteins work, changes in environment during development can allow the proteins that were normally forced to fold a certain way to express their variation. those variations that are beneficial to survival produce offspring that are better adapted to compete in that environment, but it isn't just the one, so to go back and kill just one Devonian fish would have no real effect as it would be an insignificant number compared to the others of that new species lost to predation or the ones that lived long enough to breed.



> So, you are correct that if Einstein had not developed his theories of Relativity, or James Watt his engine, then it would be left to someone else, and that the time was just right for someone to do those things. However, the events would still unfold in a slightly different way, and however small that difference was to begin with, it would still make a huge change because of that "Butterfly Effect" already mentioned and more properly termed *Chaos Theory*.


 
there would be changes in detail in the short term, but in the long run things would end up pretty much the same



> A World War would surely have taken place, but other than that, you cannot predict any outcome.


but it would have been the same alliances fighting against each other using the same weapons and tactics. the changes in armaments and tactics would have followed similar lines as they did and the local ripples in history would be flattened out after a few years.



> Speaking of cycles, just as Communism in the Soviet Union collapsed, I'm quite sure that, had the Nazis won the Second World War, by the present time the Super State that resulted would now have fallen apart and Nationalism been replaced by something less extreme. Hitler would probably have been assassinated shortly after they won the war. Jews, Gypsies and homosexuals would have continued to have been exterminated until those criminally insane he had in positions of power were removed. We would however, have scheduled Rocketship flights traveling from Europe to North America.


 
I like the example but have to disagree with the rocket ships.
if we would have had them in those circumstances we would have now.
the same people who were working on rockets in Germany continued their work in the US after the war but they didn't give us trans atlantic rockets so they probably wouldn't have in the changed history.

probably because conventional aircraft proved to be more economical to run, were less dangerous on take off and landing and didn't subject the passengers to high G force on take off.

here's a slightly different way of looking at it and I'll use a big and emotive butterfly for it and my appologies to anyone offended by this as that is not my intention

if the events of 9/11 had not happened, what would be significantly different in your life today? 
the war in Iraq would probably have still happened (GWB would still have wanted to finish the job his daddy started)
a few laws would have been different but those that were implemented would probably still have been implemented (instead of a war on terror as an excuse there would have been a different reason like gangster rappers or some other easily targetted group that scares the average voter)
details change but not as much as we would like to think (especially as many of our beloved SF books rely on the butterfly effect being more dramatic) 

the butterfly effect may tip the balance, but the balance has to be almost at the point of no return to tip


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## ManTimeForgot (May 25, 2009)

Urlik said:


> the butterfly effect may tip the balance, but the balance has to be almost at the point of no return to tip




It's good that you recognize this, but you don't seem to understand it's full consequence.  Exactly how do we know when something is on the "point of no return?"  What method is there to use to measure or determine how "close a call" something was?  Trial and Error is the only thing I can think of that can be used to measure and human perception/determination is only so good.  Mucking around with history just to find out if something horrible will happen doesn't sound like a good idea does it?

Here again we are in a position of ignorance.  We know absolutely nothing about what percentage of contribution all things were towards the success or failure of certain events.  Perhaps if Hitler's chef had made him a more satisfying meal on one day he would have been in a better mood and not chosen to back stab Russia for oil.  Perhaps if someone had been in a bar on September 10th, 1938 then many years later Hitler's chef would have made such a meal.

The short of this is: until we change history we have no basis for comparison.  History unfolded exactly as it did, and without a basis for comparison we have no way of knowing how any change would unfold to its fullest extent.

MTF


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