Why do we think time paradoxes exist?

The oft quoted example of

"I got back in time to before i was born and kill my mother, therefore I could never have been born, therefore i couldnt go back and kill my mother"

I'm wondering why there would even be this sequence of events? Who's to say that, as soon as I kill my mother, I would disappear because I was never born? As a pattern of atoms and molecules at a point in spacetime, why should I be linked to another point in spacetime just because I was there briefly? Why can I not (as a block of matter) be inserted into a location in spacetime and proceed from there? My actions have consequences for my future from that point, but who is to say that any of them are breaking changes that will affect me right there and then? At the moment I kill my mother, she is destined never to have me as a child, but why would that affect my presence in the timeline at that moment? I think i'd still be there, the date would be 1979, I'd be 27 years old rather than -1 years old. I'd die 27 years earlier relative to the rest of the world. I would rewrite a future such that I never have the sibling that I left behind when i travelled back, but so what..? Why does all that mean that I would never be born and hence I'd vanish from that spacetimeline? I'm there!

Does this question make sense?

A kid kicks a football into your garden overnight. All you know, in the morning, is that a new object (block of matter) has appeared in a proximal location in spacetime. It might influence your future, it might not. Now suppose it came from the future, it appeared overnight, as though kicked there, but actually it was put there by some alien with the power to move through time. What's the difference?

I want to know why we're obsessed with this need to explain how "time" will right itself and iron out paradoxes instantaneously - is it that we arrogantly believe the course of travel through spacetime is the only one that exists and hence deviations from it are automatically restored?

 

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Time paradoxes are just for people who don't have anything better to do with their time and energy .....and who wish to indulge in useless, senseless speculation on something that we'll probably never know.

Baron Max

 

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... It's a good question. The fundamental meaning of the word "Paradox" in the first place dictates that anything described as being such simply can't exist in the first place - therefore, why worry about what can't, in practice, actually happen to begin with?

By it's own essential nature a paradox simply can't exist in reality, full stop.

Granted, most peoples principal objections towards the notion of Time Travel actually being possible at all, in that essential sense of being able to nip back and forth sort of fashion popular fiction makes familiar, arise in the first place based wholly on the notion that the actual physical act of Time Travelling, in various forms, fundamentally transgresses the more usual perception of Causality - ie, Cause leading to Effect - and transpose it with essential turning the notion of that clearly on its head and therefore, as a consequence, giving rise to a given set of circumstances all logic and reason would dictate simply nonsensical...

Nevertheless, it is in thinking around such perceptual, logical problems - time paradoxes - by which the fundamental notion of Time Travel itself has managed to evolve from simply being a narrative device originally used to make a late 19th Century work of romantic fiction work to a conceptual problem even heavyweight physicists and mathematicians aren't all that adversed to seriously pondering - even if it is just currently as a hobby.

Objections, which essentially Time Paradoxes actually are, fundamentally help
in the process of thinking a problem through - therefore raising these sorts of problems and thinking about them actually serve an actually utilitarian purpose, even though as such remain, in essence, a complete nonsense to begin with.

 

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A personal pet theory to how the universe came into being would suggest the universe exists because of such a paradox existing. I gather (without knowing any more than hearing of a quotation, please feel free to correct or research) that Hawking touched upon this while suggesting there was "no singularity".

A theory you could look at is that if someone was to invent a time machine right now, that machine and the universe they are in is a "Multiworld state" but only from their Observational perspective. Any traveling they do with the machine and changes they make will be within layers of there Multiworlds state.

If they go back in time and create a difference between the Multiverse they knew and the universe they are now in, there will be a paradox of matter being displaced in relationship to Absolute Universal Positioning. This causes yet more hypothesis on the outcome, Do the universes now occupy separate sets of coordinate? (Is the once one object now two completely different objects?) or is the same matter co-locational between multiple universe even though the objects Absolute Universal Position is now altered between the universes?.

Current observation of Atomic probability waveforms would suggest that a single object could exist in multiple locations at the same time. This ties in with previously written theory of non-locality and Relativity.

Afterall to create an entirely separate universe from a paradox would involve generating as much energy as the universe contains, which would more than likely mimic the creation of the Big Bang if Causality is drawn into the picture.

As previously suggested in other posts, The Big Bang to me was more of a "Big Number Crunch" in regards to Causality, Where all universal probabilities to where matter would eventually exist was calculated for a considerable time. You could even suggest that Causality calculations still continue to take place within Stars and planetary thermal dynamics.

All that in turn is expressed to attempt to point out that time manipulation itself isn't ruled out by physics, however probably dictated to by law. (Last thing we'd need is "time terrorism")

Utter nonsense, Such theories and discussion are now looked towards when talking about Quantum Computing, Parallel Processing and Quantum theory. Usually to try and give a visual aid in the representation of whats actually going on in those subjects.

 

I used to be interested in Time Paradoxes. I'm not any more. Because now I understand Time. You have no "freedom of movement" in time. People think of time as a length and call it a dimension, but it isn't a Dimension like the dimensions of space. You can't move through it. Two clocks can have different time experience, but they collide at the same time no matter what their faces say. When you understand what I do, you will be horrified at the number of "serious" physicists talking about time travel.

 

I am glad that you understand time; Farsight; you ideas may well be right. However some oher people are still confused, and for those people I thought I might tabulate some of the options concerning time travel and paradoxes, and see how the difficulties might be resolved.

Farsight suggests that timetravel is impossible, and so causality is preserved. This is certainly possible, and may even be the most likely pssibility. I have heard this option called the 'Boring Physics Conjecture'; none of the exotic methods of reverseal of causality can be made to work, and so there is no time travel. Another formulation of this idea is the Chronology Protection Conjecture; despite the existence of several exotic non-classical processes in Quantum theory, something in the universe always intervenes to prevent the creation of a time machine. In theory this might take the form of a kind of impassible event horizon called a Cauchy Horizon.

A second and different form of solution to the problem of temporal paradox is so-called Novikov Self-Consistency. In this solution time travel into the past is possible, but once in the past, you can only perform actions which have already happened. So if you attempt to kill your mother (or, as is more usual in these paradoxes, your grandfather, hence the general term grandfather paradox) you will fail. Not only that, your failed attempt to kill your ancestor would be a part of history, and would be consistent with the state of the universe when you first set off back in time on your failed mission. You could repeat this attempt innumerable times, and if self-consistency is correct, then you will always fail, and always act in a way consistent with known history.

Other solutions to the time travel paradox problem involve the many-worlds or parallel universe concept or concepts. In one variant of this concept, you might go back in time, kill your ancestor, and change history; this creates a new parallel world, i which events are different from the world which you started out from. In particular, sice your ancestor is dead, you youself will never be born in that particular world; but the original world you came from still exists, although you would not be able to go there by travelling through time in the forward direction. You could perhaps go back in time to a period before the death of your ancestor, and hence before the branching of the parallell worlds; ut time travel in a many-worlds scenario is always tricky, and you could get hopelessly lost among the possible worlds. This is the situation if timelines can be parallel, but are immutable.

Alternately you could go back in time, change history and prevent your own birth; the whole branch of history where you were born would cease to exist, but you yourself would continue to exist as a relic of that former timeline. You would become an acausal event, with no origin in the existing world if this chain of events were possible. In this scenariio the timeline is mutable, that is, it can be rewritten.

More detail on these possibilities can be found here
http://en.wikipedia.org/wiki/Time_travel

 

What a good post, eburacum, thanks.

I guess the "boring physics" camp is where events mark time, not the other way around. Which means time is counting, so time travel is as ridiculous as trip down the set of integers. Things move, events occur, but you can't do negative movement, you can't un-event an event. What I find surprising is the extent to which people are locked into the "time is a length" concept that's been burned into their brains. They just can't break out of it. So they talk up this tottering tower of paradoxes and parallel worlds, and dismiss the simple obvious explanation as metaphysics, or pseudoscience, or crackpot. It's amazing to see from this side of the fence.

 

Just sounds like another "language" paradox to me.

 

I think it is, valich. The trouble is, people use language to think. I've explained time, and people still struggle. See thread:

http://www.sciforums.com/showthread.php?t=59521

 

Time travel is impossible, so all of these paradox's are hot air.

 

All I can say is, if time travel was real, I would already have cranked up my time machine and gone back and stopped this deja vu thread.

 

LOL! It will take a lot of energy to fold space time enough to bring the future or past closer. It would probably take 1,000 times the mass of the sun. The sun is big but not big enough to draw the earth close enough instantenously for us to be in the past... when the sun first started for example. So you get an idea what I mean by the tremendous amount of energy needed to time travel instantenously. Bad news: if the universe is not contracting but expanding, it may mean there is no amuount of mass in our universe big enough to bend all space-time, we may have to harness them and concentrate them, which is getting borderline scifiction. However the sun is 93,000,000 miles from Earth, probably out of range for any real fold. Let me know if I make sense...

 

Even if it was possible some hollywood aspects of it is wrong. Like when you die in one time frame you may be alive in the other. In the movie Dejavu, the leading actor died only for his present day living self to witness his death. This is impossible. When you bend space-time you fold all immidiate available dimensions, so all events usually lead to only one single point, including the present. Basically, you can't be in more than space at the same time. Unless of cause there are alternate universes, which is bordering into the unknown...but not entirely inconsistent with QM, but since when has QM been consistent

 

Forward Ho

You all may want to consider that we are all time travelers - into the future at our own particular RATES. We can't go backwards acording to everything I have read. The rate of time (the counting of events as we are used to) is based on relative velocities, acceleration, aka gravity etc. Take an airplane ride and when you land you absolutely will be some billionths of a second younger than your friend on the ground. Since we can only travel into (someones) future, no paradoxes can exist. On another matter, particle physics deal with particles from the past as in the Feynman Diagrams. Also, good reading is John Cramer's (Un. Washington) Transactional Intrepretation which deals with "enabling" particles coming from the past. This deals with John Bell's and Alain Aspects Action at a distance work. There is a scary connectivity in the universe that suggests the universe is weirder than we can imagine, at least in todays age.

 

Cramer is supposedly looking into practical methods of achieving backwards causality; see this story about his work;
http://www.msnbc.msn.com/id/15817394/page/2/

What Cramer calls a 'bilking paradox' is basically Novikov consistency; it should be impossible to set up an experiment where a paradox is created. The events of the past must be consistent with the present, even if causality is reversed.

 

Thud. Thud. Thud.

That's me banging my head on my desk.

 

paradoxes don't really exist. we all have subconscious perspectives of how the universe operates. when we conceive of a concept that defies or conflicts with this perspective, we call it a paradox. but in actuality, neither our perspective nor our concepts are reality.

so, in essence, whatever is possible is possible and we won't know till it occurs.

 

Paradoxes DO exist. For instance a Jet breaking the sound barrier is just one instance of a real world paradox.

You could then take that further to suggest that with ever increasing speed in telecommunications we generate yet more paradoxes everyday. Considering the first message systems relied on runners with messages, then visual signals like Semaphore, beacons or smoke, later still came the use of Cabled morse (telegraphs) which evolved to voice communication and eventually radio transmission removing the need of cable. With computers the transfer of data is in greater excess and no longer just dots and dashes.

Every iteration of this telecommunication revolution has and will cause paradoxes in regards to how things were once done are done even faster.

 

Im confused on how a jet breaking the sound barrier is a paradox?

 

Consider it like this, If you travel fast enough you could stop and hear yourself approaching.