Why altering time should be impossible. (in theroy)

[Deleted]

Altering time, history or even small events has been a dream many people have had.
This thread will focus on altering the passed and not the future.

One reason to why altering time, history or even small events should be impossible.

Lets say that I have acquired means of traveling in time, allowing me to change the passed.
Lets now take a senario where i lost a loved one.
So i go back in time and prevent this person for dieing.

This will create a paradox where I never lost this person and have no need to go back in time to save them, thus i dont, and they will stay dead.
This works the same for any other given senario you find your self going back in to alter time, removing the reason for you to go back and change it in the first place.

Another senario that I have thought alot of. I have the means to create a worm hole that will go back in time, i now create one and shoot my self, 1 min back in time. Who killed me? I was killed 1 min before I could pull the trigger, and there for I cannot have killed my self.

ofc If u were to go back and lets say, kill Hitler after the war was over then, at least i belive, that should not alter time in any major way that would make it impossible for you to have the idea to kill him your self


What are your thoughts of these paradoxes that should make it impossible, in theory, to alter history in and major way.


Disclaimer: I'm not a scientist/physicist nor do i have a substantial understanding of how time travel would have any impact at all.( but lets face it, do anyone?)

[Blueobelisk]

You just affected a different timeline by going back in time. The one you came from still has your loved one dead.

And if a you from the future didn't come back to save your loved one for your timeline, that just means you're the first timeline to incite the action.

That by no means is a reason to say altering time is impossible.

[Deleted]

Different timelines my friend.

[Surfd]

Many different theories pop up when you ask these kinds of questions, so "rules" for lack of a better term are usually agreed upon.

A: do You allow the "alternate" timestream theory. Changing an event from Timestream A results in the creation of Timestream B, where the new cause / effect relationship results, while A still remains, with the old cause / effect in place (effectively creating infinite branches for every possible cause / effect outcome).

B: If you invent a time machine, can it allow you to travel back to a point BEFORE the machine was invented? Some theories say time travel might be possible, but only within the existant timeframe of the machine (IE, if I create a time machine in 2010, sit on it for 20 years, and then use it in 2030, i could still only travel to a time period between 2010 and 2030, not to a point before that).

C: paradox, and the nature of cause and effect can also be a tricky one to deal with. Some time travel theories actually allow for an Effect to be it's own Cause (crazy, I know, but it works (I think there was a bit of that in the Terminator Movies, because some of Skynet was actually built using the parts from the Original T100 robot that was destroyed in the first movie). Others actually avoid paradox by allowing for the possibility that a time travel "loop" may already be a pre-determined outcome of an expected event (I think the movie Looper was loosely based around this).

Of course, If you assume the single timestream model and allow for alterations to "stick", then time-alterations in the past could quite easily occur, because once the alteration has been made, from that point on, the remaining cause / effect reactions proceed as normal and the rest of the "future" from the point of change becomes reality, regardless of if that new reality would result in removing the originator of the change.

[Nychris]

For you to be able to go back in time at any given moment of that "past" this means that every single second has it's own timeline plus that time has to go in a circle or keeps starting over and over again from that "start".
Say you want to go back in time to the first second of this planet , that second has to exist somehow.

And who exactly said that a "wormhole" of some kind has time altering activity stop watching startrek or in what fantasy can you compress "time" for it to be flexble and if possible any action you do in the past it will create a new timeline

[Temp name]

There are multiple theories of how time works. Some say it's a stream (the theory OP is working from), others more of an ocean where time goes in all directions, every little choice causes it's own timeline to be created and so on.
The way I see it, if someone was to change time, we wouldn't know. We'd have always heard the "alternate" way it would've happened. Just my view on it ofcourse.

[checking facts]

what if you go back in time, save your loved one, than go to your past self and tell him that on X day he has to go back in time and save his loved one?

[Deleted]

What are your thoughts of these paradoxes that should make it impossible, in theory, to alter history in and major way.

Your paradoxes can be avoided if each change in the timeline creates a new universe. This is compatible with the idea of multiple dimensions and time being non-linear.

[Anastacy]

All this "timeline" crap is just science fiction, at best.

All time is is a measurement...a measurement of motion, mostly. To "go back in time," you'd have to reverse ALL motion that occurred between the "time" you want to go to, and the "time" you're currently at. This would include such great feats as spinning planets backwards and some-such stuff.

[Sykol]

Let's say, for example, your wife is killed. You spend decades creating a time machine to go back and save her. Future-You comes back to a minute before she's supposed to die, and prevents the death from happening. Up until the point she's saved from that original death, Future-You exists and has purpose. The moment she's out of harm's way, Future-You ceases to be, since there's no longer any reason for you to exist. However, that only means that Future-You changes, and only after the point where you altered time to save her. As long as she's going to die, you build the time machine and save her. Once she's safe, you don't.

At least, that's how I'd see it happening using the idea that there is only one timeline.

[Dezerte]

Commonly knows as the "Grandfather paradox".

[Deleted]

I don't think those paradoxes exist.

Reasons
If you go back in time, what happens with the current time that you lived in? Will it dissapear, will you undo it? Because if you undo it, and you're the only one who is unaffected by it, then there will be no paradoxes. You will still be there, the universe won't care how you were born or how you came to be, because it only knows you're there.

Let's say you stop yourself from being born, then nothing would happen because old you and new you would be 2 separate entities. Those atoms holding you together will be dissociated from the other you. And now let's say you send an atom back in time. If those paradoxes exist, then that will too affect that single atom.

But not only that, if the Many Worlds theory is true, then there would be no paradoxes because there will be new universes popping up ALL THE TIME, because the universes are disconnected from each other.

[Reeve]

Time dilation is a means of altering time, and is a real thing. The closer you get to light speed relative to everything else, the more the speed of time for everything else seems to speed up. So if you could get in a spacecraft in a stable orbit around say a black hole, moving near light speed, you could watch centuries or millennia on Earth go by.

[Deleted]

Time dilation is a means of altering time, and is a real thing. The closer you get to light speed relative to everything else, the more the speed of time for everything else seems to speed up. So if you could get in a spacecraft in a stable orbit around say a black hole, moving near light speed, you could watch centuries or millennia on Earth go by.

You're totally right, but I think the OP means altering time as in, going back and changing things.

[Reeve]

You're totally right, but I think the OP means altering time as in, going back and changing things.

I know, but the title was vaguely worded and encompasses what I mentioned, so I thought I'd point it out.

[Alexpower3]

People assume that time is a strict progression of cause to effect, but *actually* from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff. In theory.

[Deleted]

some great comments, I did consider alternate universes/time lines, that do idd change things.

---------- Post added 2013-02-01 at 05:16 PM ----------

People assume that time is a strict progression of cause to effect, but *actually* from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff. In theory.

doctor who <3

[Netherspark]

Using the OP's example it would be impossible to intentionally change history, but it could be un-intentionally changed without creating either a paradox or causality loop.

Anyway, even if time travel were possible I believe it should be prohibited under pain of death; It's far too dangerous.

[Deleted]

Let's say, for example, your wife is killed. You spend decades creating a time machine to go back and save her. Future-You comes back to a minute before she's supposed to die, and prevents the death from happening. Up until the point she's saved from that original death, Future-You exists and has purpose. The moment she's out of harm's way, Future-You ceases to be, since there's no longer any reason for you to exist. However, that only means that Future-You changes, and only after the point where you altered time to save her. As long as she's going to die, you build the time machine and save her. Once she's safe, you don't.

At least, that's how I'd see it happening using the idea that there is only one timeline.

I like your idea

[Loxxie]

Using the OP's example it would be impossible to intentionally change history, but it could be un-intentionally changed without creating either a paradox or causality loop.

I fully agree with this. If there is but one timeline and not several, going back in time to change something and changing it would remove the need to go back in time in the first place thus you wouldn't go back to change it.

However, if you say made a timemachine that sent you to a random timeperiod where you have no intentions of changing anything or going there in the first place, you could change anything as you would be going there anyway, in the future that is.