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  #51  
Old 12-06-2018, 06:04 PM
dtilque dtilque is online now
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Originally Posted by Quimby View Post
I have it on good authority that someone stepped on a butterfly hunting a Dinosaur and that's how Trump won in this timeline.
Damnit, someone find that person and stop them. But why was the butterfly hunting the dinosaur? Were butterflies that ferocious in the Cretaceous that they hunted down and killed dinos?

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Originally Posted by cmyk View Post
Whatever else, if we went back and killed Hitler when he was a baby, we might all still be enjoying the aesthetic design of the swastika, and Hipsters the world over might all be sporting toothbrush mustaches.
That last is probably reason enough not to prevent WWII. Sorry Jews, we're not undoing the Holocaust this year.
  #52  
Old 12-06-2018, 06:39 PM
Taber Taber is offline
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I agree generally with JAQ, but I would add that although technology might be similar, every movie, song, novel, and artwork would be different. And that would feel like a very different society. I think over time, that would cause the cultural differences to pile up more and more.
Rereading your OP, I think you are right that time travel would cause more people to be born to different people. I think I was responding to the general case of butterfly effect causing amplified changes as time goes on whereas I think the changes of the butterfly effect will tend to converge back to normal as time goes on. To be fair, I think a few others were responding in the same manner.
  #53  
Old 12-06-2018, 06:46 PM
Taber Taber is offline
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Originally Posted by Just Asking Questions View Post
I think people confuse the general and the specific.

Killing Hitler might still lead to a reality where WWII happened, nuclear weapons were invented, General relativity was theorized, the cold war happened, and some buffoon was elected President in 2016.

But everyone will be different. Different people will have lived and died. Time travel to 1920 kill Hitler and return and it is near 100% that no one will ever have heard of you. Your parents will have never met. Your office and job might be there, but no one you know will be working there.
If this is aimed at me, earlier posts addressed the general case, including your own about how we might not have nuclear weapons and have jobs like mystellogist. I do not feel it was off topic.
  #54  
Old 12-07-2018, 09:56 AM
Just Asking Questions Just Asking Questions is offline
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If this is aimed at me, earlier posts addressed the general case, including your own about how we might not have nuclear weapons and have jobs like mystellogist. I do not feel it was off topic.
Not directly at you, sorry. I just wanted to clarify that if time tracks back to what is "normal", with all the major events happening more or less the same, all the people will still be different. Like, we'd still have a buffoon narcissistic President, but it wouldn't be trump.
  #55  
Old 12-07-2018, 12:52 PM
msmith537 msmith537 is offline
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I don't believe in the idea of a Clockwork Universe. If a time traveler were to go back to a particular date, I think it has the effect of restarting the timeline from that date, and all events that follow may be different based on natural randomness of action.
Timeline for who?

My problem with "time travel" speculation is that it never really answers the question that if one can visit any point on the timeline as if they were traveling to another city or country, what makes "right now" any more or less significant than any other point in time?

To put it another way, why would the timeline restart for everyone in 2018 just because some traveler went back to 1942?
  #56  
Old 12-07-2018, 02:04 PM
Pábitel Pábitel is offline
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Unless we’re the other world, the world he arrived in.
In which case we would know about time travel, but we don't, so it isn't.
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  #57  
Old 12-07-2018, 02:10 PM
Just Asking Questions Just Asking Questions is offline
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Originally Posted by msmith537 View Post
Timeline for who?

My problem with "time travel" speculation is that it never really answers the question that if one can visit any point on the timeline as if they were traveling to another city or country, what makes "right now" any more or less significant than any other point in time?

To put it another way, why would the timeline restart for everyone in 2018 just because some traveler went back to 1942?
If I may attempt this:

Assume a deterministic universe (free will is possible. Closed time loops (I travel in time, kill my grandfather but unknowingly sleep with my grandmother and fathering my own dad, then when I return nothing has actually changed except my knowledge is increased about my own origin).

The second a time traveler steps into the past, that past is now changed from what it was. Before time travel existed, what is known as the original timeline progressed as we all remember it here and now. But I invent a time machine and go back to 1942. By doing anything at all, I have changed the original timeline. Even if the affect was minuscule I have made a difference. Average people may not notice if I spit at the South Pole and left, but the Universe knows. And it has an effect.

For the duration of my trip, the universe had more mass. Technically, it had duplicate mass. All the mass in me and my time machine already existed in the universe, and was already somewhere there in 1942. As I breathe in and out, and slough off skin cells, and dust falls on me, some atoms get left behind, and some atoms come back to the future with me.

These atoms that weren't there before, and those atoms that should have been there, will interact with other atoms in tiny ways, but tiny changes add up. This is the butterfly effect. The CO2 I breathe out bumps some air which causes even bigger changes until whammo giant lizards roam 2018 and donuts fall from the sky like rain. More or less.

Now, to your question: "why would the timeline restart for everyone in 2018 just because some traveler went back to 1942?" The answer is, the timeline didn't restart in 2018, the timeline restarted the instant my time machine arrived. Everything that was in the original timeline between 1942 and the present all of a sudden "never happened". It's gone, or more precisely, it never was there to begin with. The universe now "runs" along a different path. That path can be very similar, even indistinguishable to a hypothetical observer "outside of time", but it IS different. And even worse, it can never be recreated! It is gone forever. The new timeline has replaced it.

And it doesn't matter if in the new timeline I never get born, or invent time travel. After returning to 2018, I still exist. But I have no connection to the new timeline. I was not born in it. None of the atoms in my body or time machine came from it. Even if the new timeline is close enough to the original that my parents met, fell in love, married, had a kid with my same name who invented a time machine, he's not me!

This is the crux of the problem of changing the past. You also change everything, from that point until the end of the universe! That's a lot of power.

Familiar pop culture examples in the next post.
  #58  
Old 12-07-2018, 02:39 PM
Just Asking Questions Just Asking Questions is offline
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Back to the Future (original).

When Doc Brown sends Marty back, starting from when he runs over old man Peabody's pine trees and culminating when he leaves as the lightning strikes the clocktower, everything in the future that he goes back to is different. He has no connection to that universe at all!

Note: the Marty we know has loser parents and no car. When he returns his parents are hip and cool and successful, and he has a new truck. Despite him apparently being indistinguishable from new Marty, he isn't new Marty. And these are not his parents. Someday, someone's going to notice, because he won't know crucial details from the changed universe. Original Marty is lucky his parents didn't move to a new house, because he'd be literally lost. Marty is from outside the universe of the end of the movie.

Not only that, you should ask yourself, what happened to new Marty? Marty who grew up with new parents, which a cool girlfriend and a new truck, is...gone! Where did he go?

Let's say that he was a better driver (he has a truck and all) and simply goes back to 1955, looks around and comes back. He is the rightful heir, as it were, to the life original Marty is usurping. And he's going to want it back. But, why hasn't he returned? More on that in a bit.

Look at the movie closely - when Marty is in Courthouse Square in the beginning of the movie and gets the "Save the Clocktower!" flyer, you can see that the ledge under the clock is not broken. When Marty returns, the ledge is clearly broken. He is in the new timeline.

When Doc is shot by the Libyans (at Twin Pines Mall), he is quite clearly not wearing a bullet proof vest. When Marty returns to Lone Pine Mall, Doc is wearing the vest. This is the new timeline.

So Marty traveling to 1955 has completely "poofed" his entire history out of existence, and replaced it with the new, mostly-indistinguishable but still different, timeline of the end of the movie. It is gone, and cannot be recovered.

But what of new Marty?

He traveled to the 1955 that he grew up from. The one where his parents were manipulated into eventually marrying by the influence of the stranger "Calvin Klein", who showed up for a week and then disappeared, never to be heard from again. During all of new Marty's childhood, the clocktower ledge was broken.

If new Marty had driven out to the location of his house, he would have found a Delorean under some bushes, which would have been quite perplexing, to say the least. Had he gone to school and checked out his parents, there is a great chance he would have met original Marty, aka Calvin.

But did he? Who knows, because his story ends. Maybe new Doc's time calculations were not as good (he cut corners, because he already knew time travel worked, so he never double checked the math, let's say), and he went...no where. It would explain one important thing.

And that is, why didn't new Marty also create a new timeline? His mere presence in 1955 should have "never happened" his own timeline and replaced it with a new one. And original marty's timeline, and the timeline we see at the end of the movie, both would have been "never happened" away and replaced with the new timeline created by new Marty in 1955. That is, if he made it.

Sad to say, I think new Marty died outside of time. Or accidentally got sent to the year 11995555, where his impact on the timeline would only go forward from that point. And with no plutonium, he is doomed to live out the rest of his (now short) life in the ruined wasteland that Earth had become.

Last edited by Just Asking Questions; 12-07-2018 at 02:40 PM.
  #59  
Old 12-07-2018, 02:53 PM
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Originally Posted by Just Asking Questions View Post
Back to the Future (original).

When Doc Brown sends Marty back, starting from when he runs over old man Peabody's pine trees and culminating when he leaves as the lightning strikes the clocktower, everything in the future that he goes back to is different. He has no connection to that universe at all!

Note: the Marty we know has loser parents and no car. When he returns his parents are hip and cool and successful, and he has a new truck. Despite him apparently being indistinguishable from new Marty, he isn't new Marty. And these are not his parents. Someday, someone's going to notice, because he won't know crucial details from the changed universe. Original Marty is lucky his parents didn't move to a new house, because he'd be literally lost. Marty is from outside the universe of the end of the movie.

Not only that, you should ask yourself, what happened to new Marty? Marty who grew up with new parents, which a cool girlfriend and a new truck, is...gone! Where did he go?

Let's say that he was a better driver (he has a truck and all) and simply goes back to 1955, looks around and comes back. He is the rightful heir, as it were, to the life original Marty is usurping. And he's going to want it back. But, why hasn't he returned? More on that in a bit.

Look at the movie closely - when Marty is in Courthouse Square in the beginning of the movie and gets the "Save the Clocktower!" flyer, you can see that the ledge under the clock is not broken. When Marty returns, the ledge is clearly broken. He is in the new timeline.

When Doc is shot by the Libyans (at Twin Pines Mall), he is quite clearly not wearing a bullet proof vest. When Marty returns to Lone Pine Mall, Doc is wearing the vest. This is the new timeline.

So Marty traveling to 1955 has completely "poofed" his entire history out of existence, and replaced it with the new, mostly-indistinguishable but still different, timeline of the end of the movie. It is gone, and cannot be recovered.

But what of new Marty?

He traveled to the 1955 that he grew up from. The one where his parents were manipulated into eventually marrying by the influence of the stranger "Calvin Klein", who showed up for a week and then disappeared, never to be heard from again. During all of new Marty's childhood, the clocktower ledge was broken.

If new Marty had driven out to the location of his house, he would have found a Delorean under some bushes, which would have been quite perplexing, to say the least. Had he gone to school and checked out his parents, there is a great chance he would have met original Marty, aka Calvin.

But did he? Who knows, because his story ends. Maybe new Doc's time calculations were not as good (he cut corners, because he already knew time travel worked, so he never double checked the math, let's say), and he went...no where. It would explain one important thing.

And that is, why didn't new Marty also create a new timeline? His mere presence in 1955 should have "never happened" his own timeline and replaced it with a new one. And original marty's timeline, and the timeline we see at the end of the movie, both would have been "never happened" away and replaced with the new timeline created by new Marty in 1955. That is, if he made it.

Sad to say, I think new Marty died outside of time. Or accidentally got sent to the year 11995555, where his impact on the timeline would only go forward from that point. And with no plutonium, he is doomed to live out the rest of his (now short) life in the ruined wasteland that Earth had become.
We see “new” Marty jump back to 1955 in the parking lot of Lone Pines Mall.
  #60  
Old 12-07-2018, 02:56 PM
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We see “new” Marty jump back to 1955 in the parking lot of Lone Pines Mall.
Yes, but where did he go? And more importantly, why didn't he come back?
  #61  
Old 12-07-2018, 03:15 PM
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Originally Posted by Just Asking Questions View Post
Yes, but where did he go? And more importantly, why didn't he come back?
Maybe he creates a new timeline/universe, and so on.
  #62  
Old 12-07-2018, 10:31 PM
msmith537 msmith537 is offline
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If I may attempt this:
My question is more fundamental. Why is 12/7/2018 considered "right now" for me? As opposed to some event that happened a week, month or year ago? Where did last week/month/year "go" that I can travel back to it?
  #63  
Old 12-08-2018, 01:25 AM
DPRK DPRK is offline
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My question is more fundamental. Why is 12/7/2018 considered "right now" for me? As opposed to some event that happened a week, month or year ago? Where did last week/month/year "go" that I can travel back to it?
Right; it makes no obvious sense how a time-traveller "first" starts out in 1985 and "later" appears in 1955 (remembering what hasn't happened yet!)
  #64  
Old 12-08-2018, 02:48 AM
as_u_wish as_u_wish is offline
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I vaguely remember a series of science fiction stories (Poul Anderson? Time Patrol?) with the premise that the universe strongly resists any changes brought about by time travel. I think it starts with a man being recruited by the patrol at the moment he is shot by his wife. "You're about to die, why not join the Time Patrol." He decides to join up with the secret intent of going back and preventing his own death. He repeatedly fails. (I think in the final effort, just as he's rejoicing at defeating his wife, sipping champagne on the roof, a meteorite kills him.)

Another version has the molecules in the past being fixed (so that rain drops are as fixed in place and solid as concrete), so when the time traveler goes back he is immediately killed because there is no "space" for him to enter, it's "solid".

These have the opposite premise of this thread. Here we seem to be assuming safe entry such that a minor change would have a large impact. These stories assume that great efforts would be required.
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  #65  
Old 12-08-2018, 10:29 AM
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As I see it, the creation of a new timeline has at least four possible mechanisms.

1/ You go back in time from your own 'present day', change the past and thereby also change the future (and your own 'present day'); this destroys your old timeline and you cannot ever go back to an unaltered 'present day'. That is gone, and everyone in it never existed. Congratulations! You are a mass murderer!

2/ You go back in time and create a new timeline, and also your old timeline continues to exist. I call this the single branching timeline scenario. Creating a branching timeline (in this mechanism) can only be caused by time travelling meddlers, so it is a rare event. Using the right technology you might be able to skip between the two branches, but these are the only two possibilities in the universe (even if they are very different).

3/ You go back in time and create a new timeline; because this is part of a multiple- or many-worlds scenario, every decision you ever make (or anyone makes) creates a new timeline, so the fact that you have created a new timeline is a trivial event. Your alternate timeline is only one among countless zillions of alternates out there. Using the right technology you might be able to skip between the alternates, but the single alternate timeline you created is not qualitatively different to any of the others, even if it is entirely different to your original 'present day'.

4/ You go back and change time, but somehow, with no plausible explanation, the changes you have made 'revert to the norm' and the future ends up looking identical to your original 'present day'. I can't see any possible way that this could happen, but it does have the advantage that it is 'self-consistent' without resorting to multiple timelines, and so it may be the real deal.

I should also mention the fifth option, which is (I believe) favoured by many physicists and philosophers and which solves many problems associated with time travel paradoxes; Novikov Consistency, which simply states that you can't change the past, even if you have access to a time machine. If you go back in time you are going back to a time which has always had you in it, so sneezing or displacing air molecules won't have any effect, because you have always been there to displace them.
https://en.wikipedia.org/wiki/Noviko...ency_principle
  #66  
Old 12-08-2018, 12:58 PM
SlackerInc SlackerInc is offline
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That Novikov thing is trippy, and I’m glad you introduced me to the concept; but ultimately I think it’s too cute by half.
  #67  
Old 12-08-2018, 02:53 PM
Annie-Xmas Annie-Xmas is offline
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Stephen King's novel 11/22/1963 is the story of a man who discovers a wormhole to the past and tries to prevent the Kennedy assassin. He find out the past does not want to changed, and when he finally succeeds, the future is changed for the worst (isn't it almost always). He has to go back to the past and set things right.

There was also an episode of the new Twilight Zone and a man goes back in time and kills the baby Adolph Hitler. The baby's father is so worried the death will make his already wacky wife go totally bonkers, so he goes out and buys a gypsy's baby to replace the dead one. And guess who the gypsy's baby will grow up to be?

Time travel and changing the past is an interesting hobby, but I hope we never find out what happens for real.

Last edited by Annie-Xmas; 12-08-2018 at 02:54 PM.
  #68  
Old 12-08-2018, 05:14 PM
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Speaking of baby Hitler: You (and only you) are given a once in a lifetime chance to time-travel back to the Hitler home while Adolph’s mother, Klara is breastfeeding her baby. If you accept the trip, you’d pop into the kitchen adjacent to the sitting room containing mother and baby. No one else is in the house. You can’t bring anything with you—you’re naked (but, the Hitler kitchen is well-supplied with cutlery, etc.). You’re allotted 5 minutes in the house before you are zapped back to present day. No one will know your identity (past or present), whether you kill baby Adolph or not.

What do you do?

That’s a tough question. I’d have no problem killing adult Adolph in order to (hopefully) prevent ~6+million innocent people from being tortured and exterminated.

But, a cute little baby? A baby thus far innocent of whatever twisted nature/nurture/psychological aberration that ultimately turns older Hitler into a monster? And killing him in front of his, so far as I know, innocent mother? I just don’t know what I’d do. That would be an ethical dilemma, for sure.

Now, if I walked into the sitting room and baby Adolph was sporting his Charlie Chaplin mustache and mother Hitler was giving him the Nazi salute—my decision would be easier.

What about you?
  #69  
Old 12-08-2018, 10:11 PM
msmith537 msmith537 is offline
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Originally Posted by Annie-Xmas View Post
Stephen King's novel 11/22/1963 is the story of a man who discovers a wormhole to the past and tries to prevent the Kennedy assassin. He find out the past does not want to changed, and when he finally succeeds, the future is changed for the worst (isn't it almost always). He has to go back to the past and set things right..
Sounds like the episode of Red Dwarf where the crew accidently prevents the Kennedy assassination and convince JFK to act as the "grassy knoll" gunman and kill his other self.
  #70  
Old 12-09-2018, 03:32 AM
SlackerInc SlackerInc is offline
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Tibby: I don’t think I could kill a baby, not even baby Adolf.
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