Why altering time should be impossible. (in theroy)

[Cernunnos]

If them dying was the reason you made the time machine to go in time and stop them from dying, then yes, there is a paradox, since if they never died you would never have made the time machine.

If time travel already existed through some other means, you could go back and stop them from dying, which created a new time line in which they survive, and the old time line where they died never happens.

[Agrias-Oaks]

There are different theories and even that one is a cheap way to deal with paradoxes.

multiverse isn't really that cheap, the logic makes sense. a cheap theory would be http://en.wikipedia.org/wiki/Novikov...ency_principle

anyways, back to multiverse. level 1 for example, especially makes sense, in short it's saying given infinite space, beyond our cosmological scope, events can duplicate the exact same way as it did on earth, with slight differences, repeated with more slight differences elsewhere in the universe. This is straight math of probability really. it's level 3 that's used in many fictions, the many worlds interpretation, and the one most people associate with multiverse theory.

[Vinni]

I don't think I explained my thoughts on time from the previous post too well.

I don't see time as an actual thing, but as an artificial ''concept'' created by us to explain things. We can go forward in ''time'' just as we are doing right now but we can't ''jump'' forward by skipping 5 minutes for example. You can slow down the rate at which some things can occur but it just doesn't seem like slowing down time, only the rate at which A does action B.

Also I know it's a different kind of topic but time differences in countries? It annoys me that we can't just simply have one universal time used across the globe and it simply gets darker/lighter/whatever at different times for different locations. It's way simpler the way it is but I don't see any actual ''time differences''.

[Agrias-Oaks]

I don't think I explained my thoughts on time from the previous post too well.

I don't see time as an actual thing, but as an artificial ''concept'' created by us to explain things. We can go forward in ''time'' just as we are doing right now but we can't ''jump'' forward by skipping 5 minutes for example. You can slow down the rate at which some things can occur but it just doesn't seem like slowing down time, only the rate at which A does action B.

Also I know it's a different kind of topic but time differences in countries? It annoys me that we can't just simply have one universal time used across the globe and it simply gets darker/lighter/whatever at different times for different locations. It's way simpler the way it is but I don't see any actual ''time differences''.

with time dilation, from the perspective of the person traveling at the speed of light, then coming back to earth, he would've traveled to the future, thus, a form of future time travel. to the traveler's perspective, (example) 1 year would've passed in "time" and arriving back at earth 50 years would've gone by.

[rhorle]

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.

The problem is that paradox only looks at one side of the picture and relies on the notion that the future won't be changed. Of course it will but by changing the future it won't change the fact that you exist in the present. If time travel is possible then that paradox by its very nature can't exist. Does it matter if you erase the future you knew by changing the past? No because you are changing things in your present time.

---------- Post added 2013-02-01 at 03:52 PM ----------

If them dying was the reason you made the time machine to go in time and stop them from dying, then yes, there is a paradox, since if they never died you would never have made the time machine.

But there is no paradox. Because once you travel back in time you are changing the time from the present, and not the future. A new time line can't exist unless you are around to change it. So you'll always have gone back in time no matter what you do. Because what you change about the future can only change if you were the one to change it.

[Vinni]

with time dilation, from the perspective of the person traveling at the speed of light, then coming back to earth, he would've traveled to the future, thus, a form of future time travel. to the traveler's perspective, (example) 1 year would've passed in "time" and arriving back at earth 50 years would've gone by.

See, I think tonnes of people have heard of this but is there any actual proof? Don't get me wrong, I'm not trying to stubborn and shoot it down; it's just that as far as I know anything similar to do with time is only a theory or a concept or something similar. I would genuinely love to see some concrete proof (except from any site where anyone can edit) to prove time is actually ''something''. The going at the speed of light concept just seems like crap if I'm being honestly sceptical because, and remember I'm really ignorant when it comes to physics, it just seems like some ideas based on different concepts that don't necessarily make it true.

[Templar 331]

"Going forward is not the problem. Going back, that's what screws the pooch."

Farscape - Unrealized Realities. Best way to explain time travel.

[Grumash]

Psh, I alter time with my mage every three minutes

[Frozenbeef]

what if time is constant and once something happens it doesn't happen again under any circumstances and is impossible to go back or repeat any event.

[Vorondil]

Meh, I was expecting some sort of mindblowing theory: but this is like the basic reasoning why "time-travelling" isn't possible

[Fugus]

There are lots of possible explanations of resolving this.

The one I honestly wouldn't be surprised with is just the thought of Time itself just not having some huge amount of error correction built into it such that when you jump out of your time, you cease to really be apart of time and are pretty much just riding the flow again where you jump back in.

Think of it this way, you go back in time and kill your grandfather, you personally do not cease to exist or anything. You can live out your life back in that time or if you want you can go back to the time you came from but when you get there, as far as everyone is concerned you are just some stranger from out of town as your father was never born and neither were you.

It also has the side effect of you never being able to go see yourself in the future. You jumped 10 years into the future, you will not see yourself as from everyone else's perspective you just disappeared 10 years ago and were never seen from again. Even if you returned to the present, any future jump you had will still be a future where you disappeared from it the moment you left.

It allows for the paradox's as time itself just doesn't error correct them out or care and it is honestly one of the simplest solutions that doesn't rely on some major other imaginary things we don't see and can't prove yet. The truth of how it is handled, I don't think we will honestly have that answer till we honestly get far enough to try it.

[Spl4sh3r]

There are four different theories about time traveling. First is your theory that it creates a paradox. The second theory is that if something happens causing us to go back in time, then the thing said person that went back is about to do has already happened once. Think Harry Potter on this one. The third theory is that you go back to another universe that anything you do doesn't effect your future, however this causes there to be two of you. Then the fourth is similar as the third, but with the changes that if there are two you in one universe the one that was already there disappears and you take his place (seeing as you are going into his universe and not the otherway around).

[Mear]

I like the whole different timelines theory. But i can be abit bias from Steins;Gate and other some other things :>

[Migas11]

Go watch Dr. Who. You'll get it

[Kurioxan]

with time dilation, from the perspective of the person traveling at the speed of light, then coming back to earth, he would've traveled to the future, thus, a form of future time travel. to the traveler's perspective, (example) 1 year would've passed in "time" and arriving back at earth 50 years would've gone by.

That is true theoretically but it is still, in my view, a tad of a jump to call that time travel, the effects of high speed and gravitational distortion will slow down entropy within, all the persons processes will move at a severely slowed rate, if you call that time travel then you have to call cryogenic preservation time travel, since it removes energy from the system and slows down entropy, same principle different mechanisms.

[Cernunnos]

Go watch Dr. Who. You'll get it

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The Doctor will fix it.

[Vinni]

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The Doctor will fix it.

One of my favourite moments!

[Reeve]

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The Doctor will fix it.

David Tenant rocks, and clearly understands this stuff better than the OP.

[Valort]

While altering the past is a lovely wish/dream for many people
I could only hope people would, instead, learn from the past, so they wouldn't do the same mistakes over and over again.

Sadly, humanity has a way of ignoring the past and hitting their big toe on the same bed post every night.

[Reganom]

See, I think tonnes of people have heard of this but is there any actual proof? Don't get me wrong, I'm not trying to stubborn and shoot it down; it's just that as far as I know anything similar to do with time is only a theory or a concept or something similar. I would genuinely love to see some concrete proof (except from any site where anyone can edit) to prove time is actually ''something''. The going at the speed of light concept just seems like crap if I'm being honestly sceptical because, and remember I'm really ignorant when it comes to physics, it just seems like some ideas based on different concepts that don't necessarily make it true.

Compensating for time dilation is used every day with GPS satellites.