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For anyone that watched the "Back to the Future" series, we all know that the movies revolve around accidently changing the future through the past. Indeed changing history is one of Science fictions oldest and most well plot devices. However the way in which time-travel actually changes history can differ wildly. From my own perspective, it seems that changing history often falls into two different sides.

"The Butterfly effect"
And
"History finds a way"

The butterfly effect is usually the one more often used, that even the smallest change in the past can have untold changes to the future. Sometimes this is taken to idiotic extremes, such as in the movie "Sound of thunder, in which accidently stepping on a butterfly during the time of the dinosaurs leads to the end of Humanity.

On the flip side of things is another often used idea, that being "History finds a way" This version to me, seems more 'romantic' as it follows the premise that you can change little stuff in history, but the "big things" will always happen. Assassinating Hitler would just lead to someone else becoming dictator and starting WWII later, saving JFK might lead to him still getting killed later on. Logically this doesn't make too much sense, as it implies a set in stone way of looking at history.

Still between these two ideas, I am curious what others may think of how tampering with history may indeed change it. Would moving a pencil on the desk of some guy horrible alter things? Or would changing events invariably lead to the same outcome?

I tend to think most of history is the result of general social forces rather than individuals, but a charismatic person can change the course or results. For example, I think it would be almost impossible to prevent the United States from utterly consuming the west during the 1800s, no matter who was president. The Spanish-American War might not have happened if Hearst and Pulitzer had not pushed so hard for it, but the disintegration of the Spanish Empire would have happened, war or no war.

I doubt moving pencils will change history, unless reaching down to grab it means the assassins bullet misses it's mark.

Personally, I think that time travel either doesn't change history at all, or doesn't change your history (and instead sticks you in a parallel universe with the consequences of your actions). I'm not aware of any other self-consistent options.

But to refine the question: "what consequences are likely to result from a time traveler's actions" or "what consequences would result from very small changes in historical events?" The answer is "it depends."

Extremely small events should be lost in the noise- moving a pen on my desk doesn't normally alter the routine of my day. Even if it does, it may not alter anyone else's interactions with me, and even if that happens it won't necessarily change the course of their lives. Most small changes would be damped out over the long term, I'd expect.

On the other hand, specific small changes can lead to "for want of a nail" outcomes. The obvious ones revolve around historically famous individuals- what if Alexander the Great had died in a javelin-throwing accident in his youth? Or if Hitler had been run over by an out of control bratwurst wagon in 1908? One more sports training/traffic fatality normally wouldn't change anything, but if it happens to those guys? Who could take their place and cause the same outcomes to occur?

But we can also get great changes by harder to detect cases where something major failed to happen because of a minor change. Something that today's historians may not even be aware of, but that could easily have gone the other way and had greater long term consequences. Perhaps some medieval prince who died in infancy of a random childhood disease would have turned out to be the next Alexander the Great. Perhaps the amiable relationship struck up between two men in the waiting room of their superior's office turned out to change the course of the organization they were a part of, and if one of them had been in a bad mood that day everything would have been different.

It's completely impossible to predict, I'd say. Without prior knowledge of how events are going to unfold (omniscience about the future) we can't guess which minor events will have butterfly consequences and which won't. Any more than we can go back in the past and reliably find the points with butterfly consequences in our own history... which is much better understood than our future.

Simon_Jester wrote:Extremely small events should be lost in the noise- moving a pen on my desk doesn't normally alter the routine of my day. Even if it does, it may not alter anyone else's interactions with me, and even if that happens it won't necessarily change the course of their lives. Most small changes would be damped out over the long term, I'd expect.

On the other hand, specific small changes can lead to "for want of a nail" outcomes. The obvious ones revolve around historically famous individuals- what if Alexander the Great had died in a javelin-throwing accident in his youth? Or if Hitler had been run over by an out of control bratwurst wagon in 1908? One more sports training/traffic fatality normally wouldn't change anything, but if it happens to those guys? Who could take their place and cause the same outcomes to occur?

But we can also get great changes by harder to detect cases where something major failed to happen because of a minor change. Something that today's historians may not even be aware of, but that could easily have gone the other way and had greater long term consequences. Perhaps some medieval prince who died in infancy of a random childhood disease would have turned out to be the next Alexander the Great. Perhaps the amiable relationship struck up between two men in the waiting room of their superior's office turned out to change the course of the organization they were a part of, and if one of them had been in a bad mood that day everything would have been different.

It's completely impossible to predict, I'd say. Without prior knowledge of how events are going to unfold (omniscience about the future) we can't guess which minor events will have butterfly consequences and which won't. Any more than we can go back in the past and reliably find the points with butterfly consequences in our own history... which is much better understood than our future.

This. I'd say the course of history is determined by a combination of deterministic forces and stochastic events. The former obviously would be relatively difficult to change, the latter relatively easy.

I also tend to think that, generally, deterministic trends are more important than individuals or specific stochastic events, and the stochastic events form unpredictable eddies within larger deterministic currents. For instance, I suspect in the vast majority of possible worlds the civilization that eventually comes to dominate the Earth would start out in the Old World. On the other hand I also think this is probably an oversimplification, and it's probably possible for stochastic events to have a major shaping effect on the deterministic flows if they're powerful enough.

One thing that has crossed my mind in regards to time travel stories is that in most cases it is only the time traveler themselves that alters the timeline. They seem to assume that humans have no free-will and that during any one 24-hour period that everyone will perform the exact same actions unless a time-traveler somehow changes the stimuli.

I mean, I know I'm not an expert on quantum mechanics and I'm probably mistaken but I've heard than on the sub-atomic scale then random events can happen, little changes that occur at random and kind of effect things on the larger scale.

You would think that if humans had actual free will then a time traveler could go back in time to say... some time before WWI and just stand around on the moon without actually interfering with human events at all. However, during that 'second chance' or second go-though where the time traveler exists then all the humans in the world (and possibly the animals or unfathomable atmospheric phenomenon that determine the weather) would have a second chance to do something else.

Alot of people might do perfectly mundane things like change what they have for lunch, or ask someone out for a date or neglect to ask them for a date, or maybe some married couples might have sex and on the microscopic scale all those little sperm would try to catch the egg and maybe this time then a different sperm and set of chromosones makes contact and a different person is born as a result.

Thus, the earth and human society might actually be made up of primarily non-repeatable events. Going back in time to change one little thing will hardly work because in doing so you are giving billions of other people an opportunity to make their own little changes, even if they themselves don't know it.

So, even without doing anything so rash as shoving Hitler down a flight of stairs, then just stepping into the past creates an alternate universe where nearly everything diverges. In the next generation, then completely different people will be born and they in turn will make different changes, large-scale socioeconomic events will probably undergo similar changes but individuals such as inventors or politicians who can change the world would be different and do different things.


So... I think I'd go with the butterfly effect taken to an absurd level, where traveling to the past in any way results in a completely different time line where everyone has an opportunity to make different choices and those choices in turn result in a veritable mass of butterfly effects than can't be calculated. Things like stock market crashes might not happen due to numerous people randomly deciding to invest in something else. This would result in whole generations of people never being born (due to random events at the cellular level regarding human reproduction) but in turn a whole different generation of people would be born instead and they would make their own decisions. Big socioeconomic events could still take place, but not always in the origional way it was done before. Take Hitler out of the equation and World War II would probably have been averted, or at least it would have been a smaller war that didn't involve genocide. That doesn't mean that the attacks of Imperial Japan might not take place... and who knows, maybe something even weirder and more horrible might have taken place.

But yeah, time and history seem like one of those things that are affected and changed by countless variable and events. And any time-traveler who goes back in time to bet on race horses suddenly discovers that these games of chance are random and that there is no guarantee that you'll win even if you got a cheat-sheet from the future.

Well, that's the inevitable result of a parallel-universe model of time travel, I'd say, Rossum.

The other self-consistent theory is what I call the "Law of Conservation of History," in honor of Larry Niven, who published the idea first as a formal theory of time travel, so far as I know*. In this model, you can't change the past because it already happened- whatever you do winds up creating the past that led up to your existence, not altering it. In which case a guy who goes back in time a hundred years, stands on the moon for a while, then leaves, changes nothing... while a guy who goes back in time and tries to kill Hitler simply fails.

*Known as the "Novikov Self-Consistency Principle" elsewhere, because of Novikov's successful plagiarism of the concept in a 1985 philosophy paper.

Personally, in "reality" (such as there can be with a topic like time travel), I subscribe to the idea of a stable time loop. If someone travels back in time, then they were there, in your history. That history can't be changed, they become part of what's already happened, and their actions, whatever they are, are part of what caused history to happen. It's the only way I can really see time travel working...but that's just me It's quite possible that I'm being misled by the description of time as a dimension, so I picture it as a string, like a one-dimensional object. To make one part of it touch itself, the whole thing has to be changed, looping around, and it means that wherever it's touching itself, it's touching itself along its entire length. But I'm not going to go any deeper - time travel makes my head hurt

To go back to the original question, I subscribe to the "history will mend itself" theory, at least in the relatively short term. If (to use the old, worn-out, incredibly obvious example that still always works because everyone knows it) we killed HItler before he joined the Nazis, it would make little difference to whether World War II would have happened. There would still have been the anger and humiliation the Germans felt, there would still have been a Nazi party, though it might have had a different name; and even without Hitler's oratory, it would still have gained power. The war might have taken a different course, but it would still have been fought.

Of course, in the long term, it's hard to see how changes like that could possibly NOT have a difference. Perhaps not to major cultural events, but certainly to the direction of history.

Soooo, overall...I dunno

I agree with Rossum - the smallest effect can change everything - it's physics. History is a red herring - without any direct effect on any "major" historical event, one can totally change the future - as each of us is the result of an event of sensitive nature, easily changed by micro-events - a particular sperm fertilising a particular egg at a specific time, as just one example.

I have long thought that whilst the Novikov principle is logical it has a fatal flaw - no mechanism. Imagine if sent through the time machine 100 men each with a backpack nuke, each with an assignment to destroy a city in the past. By what omnipotent mechanism do they all fail? They can only fail if there is deliberate interference from something.

When the changes you make in history create the future you already had, you will most likely run into the problem that B5B7 mentioned. The time traveler knows what has happened in the future so he should be able to alter stuff.

The problem I have with the 'Butterfly Effect' is that once a someone moves back in time an infinite loop between future and history is created; every time at a certain moment in time the time traveler moves back in time (you can see this in 'Back to the future I around the end where Marty sees himself travel back in time just after he returns in his time)
The Butterfly Effect combined with an infinite loop will instantly cause a cascade of chaos effects that will eventually prevent the time traveler from traveling in time, resetting everything and starting the whole thing over again.

Rather than post a long theory, I'll simply say that Murphy is likely to have much to do with any time traveling. For all that people think they will be affecting by doing so, there would likely be a multitude of other things affected. Butterfly was a good showcase of this, though it could be argued his actions had more impact than what would make sense. Or less. Depends. Hindsight is 20/20?

B5B7 wrote:I agree with Rossum - the smallest effect can change everything - it's physics. History is a red herring - without any direct effect on any "major" historical event, one can totally change the future - as each of us is the result of an event of sensitive nature, easily changed by micro-events - a particular sperm fertilising a particular egg at a specific time, as just one example.

I have long thought that whilst the Novikov principle is logical it has a fatal flaw - no mechanism. Imagine if sent through the time machine 100 men each with a backpack nuke, each with an assignment to destroy a city in the past. By what omnipotent mechanism do they all fail? They can only fail if there is deliberate interference from something.

Obviously, they fail because they are literally doomed to fail, since it never happened. Otherwise they'd be a paradox, which is likely impossible.

There are three schools of thought on how time travel could affect the timeline. Technically four if you consider time travel to be impossible.

1. Resistant/immutable timeline. No matter what you do, you won't make any difference, your plans will fail, that gun will misfire, the bomb will fizzle, and the only changes will have relatively minor repercussions if any. Judgment Day is inevitable.
2. Mutable timeline. Make a change? Sure, but now Biff Tannen is a crime lord in 1985. Sure hope you can go back and fix it, but now you and your girlfriend will break up and your children will never exist and I won't get to buy a hoverboard in five years. Way to go, McFly. (Also, Judgment Day is still inevitable but now it comes with shittier sequels.)
3. Branching timeline. Going back in time makes a new timeline, sure... but the old timeline keeps moving ahead anyway. Then you get some dumbass who presses the wrong button in Engineering and suddenly there are another 285,000 Enterprises hailing you.

Current school of thought in physics is that time travel is impossible... essentially for the same reason that FTL is impossible in this universe. If you can travel faster than the speed of light then you can change history. I still can't quite wrap my head around the reasons why, unfortunately, but that's what the people who are smarter than me say.

B5B7 wrote:I agree with Rossum - the smallest effect can change everything - it's physics. History is a red herring - without any direct effect on any "major" historical event, one can totally change the future - as each of us is the result of an event of sensitive nature, easily changed by micro-events - a particular sperm fertilising a particular egg at a specific time, as just one example.

I have long thought that whilst the Novikov principle is logical it has a fatal flaw - no mechanism. Imagine if sent through the time machine 100 men each with a backpack nuke, each with an assignment to destroy a city in the past. By what omnipotent mechanism do they all fail? They can only fail if there is deliberate interference from something.

It's not that there would be a mechanism to make it fail, it's just that they already did fail in the past before you sent them back. So the guy on the way to London gets knocked over by a donkey cart, the man going to Paris trips and falls into the Seine, where the weight of the nuke pulls him down, the one on his way to Berlin gets caught up in a Nazi rally and turns out to be Jewish, the person targeting Madrid accidentally goes back 65 million years instead of 65 years and gets eaten by a T. Rex, etc. The only one who gets it sort-of-right is the man who was supposed to be targeting Moscow, only he lands way off course...in Tunguska.

This doesn't happen because of some omnipotent mechanism making it happen. Nothing has actually changed, except that after these men have been sent back, we know that they tried and failed. If they'd succeeded, we'd know about it already.

As always, IMO

In fairness to Ray Bradbury, in his original story the squished butterfly did not lead to the extinction of humanity, but merely some superficial changes in fashion and a different outcome in an election, many millions of years later. Wel, come to think of it, maybe the extinction-of-humanity bit is more believeable...

...somehow I prefer the third way: an alteration to a 'past' event creates a diverging time-line in which events proceed from the alteration, while the 'original' timeline proceeds to advance just as it would have, without interference.

I'm a fan of extremely small things can be changed. Of course it all depends on what sort of scale you're talking about. After all, most* time travel stories still have planets, stars and galaxies moving the same way they did before. The position of some organic scum on some of the planets may be a little different. The memories of some entities with brains evolved to hunt bananas and avoid lions may be a little confused. But so what? That's small scale.

*Mr Baxter, for example is an exception.

Five points.

1. There seems to be some discussion, so I'll let the thread live. However,
   1. time travel is entirely fictional; it has never been observed (except maybe for some weird quantum effect that falls through the time*energy > hbar crack), and it only exists in reputable scientific discourse as a mathematical curiosity in some solutions of general relativity; and
   2. discussion in this thread is either "history will change thus-and-such" or "here is how a timeline might react to time travel", neither of which is suited to SLAM.
2. Let me rephrase the OP to avoid speculation about time travel:

   Given an arbitrary change at some point in time, how sensitive is the progression of history to the degree and the location of the change?

   This removes the time travel element and instead focuses on the chaotic nature of history, which is I think what the OP was trying to get at.
3. There's another school of thought, which is that: if time travel were to occur, nothing would change, because the events in the past already happened. (See, e.g., The Time Traveler's Wife by NIffenegger.)
4. For an example of the difference an individual can make on history, consider Genghis Khan: what are the chances that the Mongols would have exerted nearly the influence they did had Khan not been able to unify Mongolia and sweep Asia? This is an example of an essentially random event (extremely strong leader) creating significant changes in history.
5. I'm moving this to OT. If the discussion suits it, Thanas, Stas, and Shep might permit it in History.

B5B7 wrote:I have long thought that whilst the Novikov principle is logical it has a fatal flaw - no mechanism. Imagine if sent through the time machine 100 men each with a backpack nuke, each with an assignment to destroy a city in the past. By what omnipotent mechanism do they all fail?

Easy: the project fails before the first time traveler is sent back. The Novikov principle doesn't state that a time traveler attempting to change history will fail--it states that he already has. It's logically necessary that your 100 men with backpack nukes fail one way or another, because we know for a fact that 100 cities were never destroyed with nuclear weapons.

Of course, if you follow that logic, it's not a huge leap to "time travel is physically impossible". It's dramatically uninteresting, but it's the only solution that doesn't require an infinity of universes appearing out of nowhere, paradoxes, or a stack of coincidences to thwart time travelers intent on changing history. It also explains why we're not overrun with time tourists.

Surlethe wrote:Let me rephrase the OP to avoid speculation about time travel:

Given an arbitrary change at some point in time, how sensitive is the progression of history to the degree and the location of the change?

This removes the time travel element and instead focuses on the chaotic nature of history, which is I think what the OP was trying to get at.

There's another school of thought, which is that: if time travel were to occur, nothing would change, because the events in the past already happened. (See, e.g., The Time Traveler's Wife by NIffenegger.)

Hence Niven's Law of Conservation of History is proposed: if time travel were to occur, nothing would change. Of course, that applies only to the specific case of time travel, not to counterfactuals in general.

For example, if I send a time-traveling medic back to Persia in 323 BC to save Alexander the Great from whatever illness/poisoning took him out, and Niven's Law applies, the time traveller fails, Alexander dies, and anything the medic does either has no effect recorded in the history we know, or causes only effects recorded in the history we know.

But this does not make the question "what would have happened had Alexander not died?" less meaningful; it just removes the possibility of using time travel as a mechanism for bringing about counterfactuals.

Simon_Jester wrote:For example, if I send a time-traveling medic back to Persia in 323 BC to save Alexander the Great from whatever illness/poisoning took him out, and Niven's Law applies, the time traveller fails, Alexander dies, and anything the medic does either has no effect recorded in the history we know, or causes only effects recorded in the history we know.

Something like the medic having a mild, undetectable case of the common cold that he wasn't even aware of because of (mumbojumboantibodies/nanites/whatever) that made him perfectly healthy, but he met a perfectly healthy Alexander, told him that he was in danger and he (the medic) was there to help heal him; Alexander believes the medic and spends time with the medic, only to contract the medic's undetected cold; the medic, being largely equipped to deal with physical trauma and the sort of diseases that exist in his day and age, is helpless to stop Alexander the Great from dying of the friggin' common cold, which is unknown in Alexander's day and he has no antibody defenses against it; then the medic is either recalled, escapes back to his own time, or Alexander's men blame him, slay the medic, and seal the medic and all his gear in a tomb that nobody ever, ever found?

That's the conservation of history argument at work, if I am understanding it correctly.

But this does not make the question "what would have happened had Alexander not died?" less meaningful; it just removes the possibility of using time travel as a mechanism for bringing about counterfactuals.

Unless, of course, you use "time travel to the past actually takes you to a parallel universe." In which case, your time traveler/time traveling party can save Alexander's life then fast forward to the aproximate equavilent of the time in which they left in their universe in order to see what changes it had? It's an interesting premise, great for fiction and role-playing and one I personally favor... But we'd have no way of knowing.

Hell, for all we know, our existance is one of those universes. Maybe Hitler was supposed to die in the bunker bomb plot, and that random nazi who knocked on Claus von Stauffenberg's door, thus preventing him from adding the second explosive charge to his bag, was the time traveller or recieved the impetus to knock on the door by the time traveller, thus prolonging Hitler's life and possibly preventing the conspirators from taking control of Nazi Germany?

For fiction, I prefer the butterfly effect. If some one went back in time and stopped this board from existing, a minuscule change in the grand scheme of things, how many different people would be affected by the change? The time you are spending right now reading this post would now be spent doing something else, which would result in a completely different chain of events in your day which would cause any one you interact with to make changes, which cause anyone they interact with to make changes, which causes anyone they interact with to make changes... etc. and so on and so fourth. It is the most logical version, unless alternate timelines is a plot device you are using in your fiction.

Also the idea that history is infallible, unchangeable etc. and will always unfold the way it was meant to is retarded as it implies some grand scheme that has been designed. I'm pretty sure that is just another way of saying "a wizardGod did it."

But what happens if you go back in time and kill yourself? Well that is the 10 Million Dollar Question. Do you cease to exist? Obviously not, because if you killed yourself before you went back in time, you couldn't be there killing yourself now could you? This is why, clearly, time travel backwards is impossible. But it is a fun fucking mind bender for stories and imagination.

B5B7 wrote:I have long thought that whilst the Novikov principle is logical it has a fatal flaw - no mechanism. Imagine if sent through the time machine 100 men each with a backpack nuke, each with an assignment to destroy a city in the past. By what omnipotent mechanism do they all fail?

By whatever mechanism prevented them when it came down to it in the past. It doesn't require some sort of "active" participation on behalf of the universe or god or whatever, just that it's factual that Paris never got nuked in its history.

As for mechanisms, well, that's pretty easy. What if you can go back in time to the same relative point in time and space? Uh oh, the planet was at a different spot in its orbit, the galaxy was spinning at a different position back then, the galaxy itself was in a different place, so on and soforth. So maybe there's like 8 backpack nuke suicide commandos just floating forever in the void. Or maybe the process cooks/freezes them. Whatever.

Hav wrote:Also the idea that history is infallible, unchangeable etc. and will always unfold the way it was meant to is retarded as it implies some grand scheme that has been designed. I'm pretty sure that is just another way of saying "a wizardGod did it."

Nah, it would just mean that the universe is deterministic, and that consequences are perfectly predictable. It would be no different than you trying to change what you just said, the direction of time wouldn't make a substantial difference on cause and effect.

But what happens if you go back in time and kill yourself? Well that is the 10 Million Dollar Question. Do you cease to exist? Obviously not, because if you killed yourself before you went back in time, you couldn't be there killing yourself now could you? This is why, clearly, time travel backwards is impossible. But it is a fun fucking mind bender for stories and imagination.

If you went back in time and killed yourself, you didn't go back in time, therefore you didn't kill you, you killed someone else, or you were unable to kill.

Yeah, that's the point of various limitations on historical change. Paradoxes can't exist, so anything that would cause one obviously fails. Of course this is probably a very low level thing (ie, it's just impossible to walk around in 1955 and pick up your mum) than the way nerds view it (that the final act fails due to 'magic').

It may still be possible to change things (or more possible) the further away from 'you' they are, particularly unintentionally.

It's pretty obviously impossible to kill yourself in the past without proposing some kind of 'speed of propagation' silliness.

Nazi Germany proves time travel can never exist -- because if time travel did exist -- there would be so many assassination attempts on Hitler backed with future weaponry, etc, because while the technology behind time travel could be tightly controlled in the first few centuries after it's invention, eventually, it would proliferate enough until even very low tier organizations would have access to it.

And even the parallel universe theory thrown around doesn't work -- there would be shitloads of alternate universes in which Hitler was a cat person and had a cat instead of Blondi, etc....and the time travellers from THOSE universes would eventually by statistics end up in ours...

Except to us, those events haven't happened yet.

And why would hypothetical future time travelling cultures give a fuck about Hitler? Do we give a fuck about Atilla the Hun?

Oh wait, you think time travellers are all YOU! Your hilarious misunderstanding of paralell timelines is really mindblowing.

The CORRECT statement is that time travel is impossible because otherwise history would be full of time travellers... but even that falls down because arguably a) it hasn't happened yet or b) those guys were later repaired by other time travellers. It's pretty childishly simple to see that the current history is either immutable or is the end-state of all time travel ever; after the Time War clearly the 'keep Hitler alive' guys beat the 'kill Hitler' guys.

ShadowDragon8685 wrote:

Simon_Jester wrote:For example, if I send a time-traveling medic back to Persia in 323 BC to save Alexander the Great from whatever illness/poisoning took him out, and Niven's Law applies, the time traveller fails, Alexander dies, and anything the medic does either has no effect recorded in the history we know, or causes only effects recorded in the history we know.

Something like the medic having a mild, undetectable case of the common cold that he wasn't even aware of because of (mumbojumboantibodies/nanites/whatever) that made him perfectly healthy, but he met a perfectly healthy Alexander, told him that he was in danger and he (the medic) was there to help heal him; Alexander believes the medic and spends time with the medic, only to contract the medic's undetected cold; the medic, being largely equipped to deal with physical trauma and the sort of diseases that exist in his day and age, is helpless to stop Alexander the Great from dying of the friggin' common cold, which is unknown in Alexander's day and he has no antibody defenses against it; then the medic is either recalled, escapes back to his own time, or Alexander's men blame him, slay the medic, and seal the medic and all his gear in a tomb that nobody ever, ever found?

That's the conservation of history argument at work, if I am understanding it correctly.

...Kind of. I mean, that's an imaginable way for it to work. But it would be way less dumb for it to work in a lot of other ways.

Like, say, the medic never arriving. Or not finding Alexander. Or getting his head bashed in by a random bandit before he reaches Alexander. Or getting laughed out of Alexander's court. Or the time machine doesn't work. Or any of a wide range of less batshit crazy outcomes.

But you do have the basic concept down, yes.

Unless, of course, you use "time travel to the past actually takes you to a parallel universe." In which case, your time traveler/time traveling party can save Alexander's life then fast forward to the aproximate equavilent of the time in which they left in their universe in order to see what changes it had? It's an interesting premise, great for fiction and role-playing and one I personally favor... But we'd have no way of knowing.

...No. The idea is that your arrival (and subsequent actions) spawn a completely new set of parallel universes that have nothing to do with any others that exist. You visit your own past. You create a parallel universe, in which what you did happens instead of what really happens. Whether you can ever go 'home' to your own history or not is an open question, but if you do, you won't have managed to change your own past, the one you read in the history books as a child.

Hell, for all we know, our existance is one of those universes. Maybe Hitler was supposed to die in the bunker bomb plot, and that random nazi who knocked on Claus von Stauffenberg's door, thus preventing him from adding the second explosive charge to his bag, was the time traveller or recieved the impetus to knock on the door by the time traveller, thus prolonging Hitler's life and possibly preventing the conspirators from taking control of Nazi Germany?

OK. Now this you got right.

Havok wrote:Also the idea that history is infallible, unchangeable etc. and will always unfold the way it was meant to is retarded as it implies some grand scheme that has been designed. I'm pretty sure that is just another way of saying "a wizardGod did it."

It's not about "meant to be." It's about "Look, I know damn well you didn't kill yourself in 1995, because if you had then we wouldn't be here talking about it."