New Model Solves Grandfather Paradox 887
goldfishy writes "If you went back in time and met your teenage parents, you could not split them up and prevent your birth - even if you wanted to, a new quantum model has stated. Researchers speculate that time travel can occur within a kind of feedback loop where backwards movement is possible, but only in a way that is 'complementary' to the present. In theory, you could go back in time and meet your infant father but you could not kill him." From the article: "Quantum behaviour is governed by probabilities. Before something has actually been observed, there are a number of possibilities regarding its state. But once its state has been measured those possibilities shrink to one - uncertainty is eliminated."
Already solved (Score:1, Insightful)
Summary (Score:4, Insightful)
That's great! (Score:5, Insightful)
Go back in time and be able to observe, only... no ability to interact with anyone either... it should be kinda like ghosts... we go back in time and observe and be like ghosts in the sense that we cannot interact and change anything that has already happened but only observe!
Imagine the possibilities of history classes of the future... maybe there are already a lot of ghosts watching us right now... the future students studying history!!
Re:What about... (Score:2, Insightful)
No no no! (Score:5, Insightful)
That's not clear at all. If I went back in time and killed the baby George W Bush, it's like he would disappear in the middle of a speech. Rather the entire course of history branching from that moment would be changed, so that in the "present" no one would ever know GW had existed.
-Alex
Comment removed (Score:2, Insightful)
Re:How? (Score:5, Insightful)
Sci-fi writers have had two main theories for a long time. Either you can go back in time and change things, or you can go back in time and "fulfill" the past you expireinced. Just because you have an influence on the past doesn't mean your influence didn't shape time into the way you remembered it.
Anyone who thinks any differently needs to go back to school.
Yes, because I'm sure these quantum physicists haven't spent any time in school...
what is _wrong_ with this reporter?! (Score:4, Insightful)
So either time travel is not possible, or something is actually acting to prevent any backward movement from changing the present.
So let me get this straight, BBC reporter. Your proof that time can't be changed, is simply that you don't remember it happening?
There are just so many flaws in that reasoning.
First, time changes could be happening everywhere, but perhaps you have not witnessed one. Wait! How about this? How about time changing, and altering your memory at the same time?
What's the matter with you? Do you believe that it is impossible for something to occur, without you being aware of it?
Is this a God complex?
What unmitigated self-importance, BBC reporter!
Now sure, I know this reporter was likely trying to parse some marlaky that they were told, but this has to be the worst use of logic I have seen.
Re:Verifying the Theory (Score:4, Insightful)
Lame! (Score:5, Insightful)
It could be happening all the time and you wouldn't be aware of it (by definition).
Sounds like bad fiction to me.Sounds like the techno-babble "justification" in the bad fiction.And the easiest way to not change it is for time travel to be impossible.If, for example, you knew a picture would be taken, you could reflect light from your body and appear in that picture, thereby altering the future.
So, travelling back in time, you cannot reflect light, and, by the same token, you cannot absorbe light.
And it just moves up from there for all other physical effects. Nothing touched, no air breathed, no light disturbed, nothing.
So, how would you even know you were in the past?
Re:No no no! (Score:3, Insightful)
Basically, if time travel is actually possible, the instant that you travel back in time, you would create a fork in the past; you go back to 1978, and every single event prior to the time that you land in may be the same, but as soon as you land in 1978 you create a version of 1978 where you existed. Getting back to your own future would be really difficult, if not impossible.
The cool thing is, if you kill someone, in that timeline that person completely ceases existing. The problem with this, of course, is that it only affects *that* timeline and any future forks created from that point onwards; it doesn't change the fact that back here, in our timeline, W became the president and launched another Gulf War.
Re:That's great! (Score:5, Insightful)
Douglas Adams figured this out long ago. (Score:2, Insightful)
Douglas Adams, The Restaurant at the End of the Universe
This is another case of science fiction being well ahead of science.
Re:One sperm in a million (Score:1, Insightful)
In a way it's kinda scary, means you don't really have free will when you go back in time, since whatever you do has been done already so the probability of it happening that way is already 1. So really, who's to say the present we're in now isn't already predetermined? Really depends on the nature of time itself. Is time 'flowing' or did it happen all at once and our perception of time is just an illusion after the fact.
Re:You insensitive clod! (Score:4, Insightful)
Re:No no no! (Score:3, Insightful)
What makes you think that you weren't there?
Re:That's great! (Score:2, Insightful)
Even if the change is small enough to not affect you going back in time at the exact same moment, you will still act differently the next time you go back in time, onward and onward until you aren't able to travel back anymore due to circumstance.
This theory is moronic. Just because a human can't perceive a change doesn't mean there isn't one. And one small change ripples through everything around it. This quantum crap seems more like voodoo science every time I hear about it.
Re:That's great! (Score:3, Insightful)
Sure you could. It would just make a branch of the timeline.
In one branch, someone killed you.
In the other branch, no one killed you.
The fork would be at the point before doing the killing. I just hope you know how to get back to the branch that you belonged in.
Re:What about parallel and multi-universes? (Score:4, Insightful)
Or...Does it allow me to 'land' back in time *only* where my landing does not affect anything in the future. Where would that be? Wouldn't my biological struture have influence on just about any environment?
Re:That's great! (Score:2, Insightful)
I could be wrong, but isn't it realistically impossible to observe a reaction without changing the outcome in some way? This was the idea behind Schrödinger's cat.
Just as it's impossible to get the exact temperature of a cup of hot tea - the calorimeter has to absorb some heat to work - it would be impossible for the light to be absorbed into the students' eyes. Assuming time is infinite, the number of time-travelling students occupying our time approaches a fraction of infinity (still infinity); at which point all the light would have been absorbed. Since that hasn't happened, the students must be akin to deaf, blind, comatose, senseless mutes.
Ergo - students of the distant future will be no different than students of today. QED and get off my lawn!
Re:You insensitive clod! (Score:4, Insightful)
So? (Score:3, Insightful)
There's no stopping it or slowing down of time, in the traditional sense. However, it might be possible (with the help of absolute zero) to stop all things in the area of the absolute zero. This would be akin to stopping time, as nothing could be happening within that area.
Unbaking a cake or uncracking an egg is a good example of going back in time. Hey, if you can take a fully-baked cake, reverse the steps, and make it back into cake-mix-egg-and-milk-inna-bowl, that's good enough time travel for me.
Re:This is just a cop-out (Score:3, Insightful)
There are numerous problems with your "proof". Here are some assumptions that you gloss over:
- You assume that t automatically progresses from -10 to 0, with all other values in tact. That is, you assume that if father is dead at t=-10, then father will be dead at t=0. Pretty wild assumption, considering that you assume just the opposite is true (that if father is dead at t-10, it's possible for father to be alive at t-11). It's a much more logical assumption that if father's state can change from dead to alive going in the negative direction (from t=-10 to t=-11), then father's state can also change from dead to alive in the positive direction (from t=-10 to t=0).
- You assume that it is impossible for father to be dead at t=0 and father to also be alive at t=0. Since parallel universes and probabilistic realities are two hotly debated ideas (by people smarter than you), I'd say that this assumption cannot be relied upon.
You can't just apply math where you want to, and gloss over these huge assumptions. Nice try, though.
- A/C #12345
Re:Novikov? (Score:3, Insightful)
You speak of "if I measured the position of an electron, then at the moment I measured it
Or do you propose that a electron only has the property of "having been measured" when a certain sort of thing "measures" it? That seems pretty odd - does the momentum space function of an electron only become uniform when *you* measure its position? Perhaps only when measured by a physicist who has published? Perhaps only when measured by a cat?
why isn't that view more popular? (Score:2, Insightful)
When I was taking undergraduate quantum mechanics (about 8 years ago), I recall feeling elated when I ran across a single paragraph in the textbook that referred to the possibility that one day someone might develop a non statistical theory for the workings of the sub quantum world.
It probably would be pure fantasy since there's no way such a theory could ever be tested (right?), but I was happy to see that it was at least acknowledged that the statistics are just a tool and not a philosophical statement about what the universe is.