Time travel paradox resolved...I think

[shanek]

Re: Re: Re: Re: Re: Time travel paradox resolved...I think

Favourite time-travel story: Bill & Ted's excellent adventure. Back to the future came out at the same time, but the logic was a bit broken. Bill & Ted's future was showing up in their past and all the pieces fit together (as far as I could tell). Also, being a HUGE Dr. Who fan, I totally dug the phone booth idea.

I think BTTF was at least internally consistent. I mean, it's not like anyone actually knows how this stuff would work. For example, Marty McFly going back and inadvertently stopping his parents from meeting. He didn't immediately fade out; the ripple effect slowly took place until the prevention of his birth would have been a certainty. That's why the older kids faded from the photo first; it kept delaying their time of meeting, getting married, and having kids. Had Marty failed, it would have meant that the alternate future Marty stuck around just long enough to prevent them from meeting. I thought that was an interesting way around the paradox.

I think the producer said once that Carl Sagan told him that BTTF was the most accurate time travel movie done to that point. Whether or not that's true I don't know.

 

[shanek]

If time travel is possible, or will ever be possible, then it's already happening, and any consequences of such have already happened. However I'm not aware of any evidence that someone from the future is paying us visits.

Come to think of it, I remember some big-brained theoretical physicist (don't remember the name, sorry) saying that if you build a time machine, you can go backwards in time, but only to the point where you built the machine, because you need the time machine to set up your entry point into the past. So that gets around the question of why aren't we being visited by historians from the future.

 

[DrMatt]

Time travel is a normal part of the quantum world. In the quantum world, particles can travel forward or backward in time.

Accordingly, it would be difficult to categorize this as a paradox. It is real.

On the scale of individual particle-particle collisions.

 

[gnome]

Re: Re: Re: Re: Re: Time travel paradox resolved...I think

Not necessarily (sp?), as long as some other part of the universe is increasing in entropy proportionately.

One of the earliest "Trek" novels, "The Entropy Effect," has this happen exactly. Spock notices that due to someone's constant mucking about in time, that the entropy of the universe is increasing so fast that there's only about a century left.

An idea obviously abandoned by future authors and script writers....

 

[Acrimonious]

The quick and dirty reason I think time travel is not possible:

Everyone is taught that matter is Impenetrable (yes that is the term for it): no two pieces of matter can occupy the same place at the same time.

I draw a simple corollary; no one piece of matter can occupy 2 different places at the same time.

At any point in time, the matter that you are made of only exists in one place at that exact moment.

Going back in time would force that matter to exist in 2 places at once. The matter from the "current" you, winning lotto numbers in hand, and the matter of the "previous" you, a week before the drawing. It's the same matter, but in 2 different places at the exact same time. That's a no can do.

If you want to go back to before you were born, you're still out of luck. The disassociated compounds that would eventually be ingested and formed into you still existed in the universe before they ever got anywhere near your parents.

 

[Mark]

Everyone is taught that matter is Impenetrable (yes that is the term for it): no two pieces of matter can occupy the same place at the same time.

But, according to quantum theory, isn't that EXACTLY what happens in our universe(s)?

 

[Guest]

The quick and dirty reason I think time travel is not possible:

Everyone is taught that matter is Impenetrable (yes that is the term for it): no two pieces of matter can occupy the same place at the same time.

I draw a simple corollary; no one piece of matter can occupy 2 different places at the same time.

Well, there are a lot of problems with that. It's not a corollary, because it isn't proved by arguments already given; it's a rearrangement of a sentence, with no logical grounds for its truth or falsity. It's not a valid logical transformation to just switch the clauses around.

This sort of argument often invokes the Law of Conservation of Matter and Energy more successfully.

 

[slimshady2357]

If time travel is possible, or will ever be possible, then it's already happening, and any consequences of such have already happened. However I'm not aware of any evidence that someone from the future is paying us visits.

Hogwash.

You say 'or ever will be possible'.

Well if time travel is invented and soley used in centuries beyond ours, we wouldn't have any evidence that someone from the future has come paid us visits, because no one would have! You assume that someone with time travel would attempt to change history prior to now, maybe they don't want to.

So there!

Adam

 

[phobos]

You assume that someone with time travel would attempt to change history prior to now, maybe they don't want to.

If I was in the far future facing down the heat death of the Universe, and I had a time machine, I know what I'd do. Start shipping hot matter from the Big Bang, and run a heat engine between that and the cold, dead cosmos of the ultimate future. Whoopee - usable energy! Of course this totally undermines the universe from the word go, but what else are you going to do, in the end?

 

[Oso]

Hogwash.

You say 'or ever will be possible'.

Well if time travel is invented and soley used in centuries beyond ours, we wouldn't have any evidence that someone from the future has come paid us visits, because no one would have!

I quote from sundog's link: (thanks sundog, a good laymans discussion)

In fact, Stephen Hawking once suggested that the absence of tourists from the future constitutes a strong argument against the existence of time travel.

Perhaps my statement was a little stronger but I'll accept Stephen Hawking's qualified support.

Well bye for now, gotta head offshore. Be back in a couple of weeks (I hope).

 

[slimshady2357]

I quote from sundog's link: (thanks sundog, a good laymans discussion)
Perhaps my statement was a little stronger but I'll accept Stephen Hawking's qualified support.

In fact, Stephen Hawking once suggested that the absence of tourists from the future constitutes a strong argument against the existence of time travel.

Well bye for now, gotta head offshore. Be back in a couple of weeks (I hope).

bah! All that proves is that you and Hawking were equally short sighted on this matter!

Good luck offshore and hopefully we'll see you soon.

Adam

 

[Psi Baba]

but what else are you going to do, in the end?

Build a restaurant!

 

[Keneke]

I partially agree with Acrimonious, and shall add my own observations.

Time, as I heard it described once, is merely the measurable quality between states of an object. This point in time is later than 5 minutes ago because of the fundamental changes in position, energy state, etc. of every piece of matter in existence.

Now then, this may present problem with time travel. Going backwards in time is not only a reversal of entropy, but also a rearranging of existence exactly as it was.

The reason the "no-further-back-than-inception" theory works is because of this theory. The theory operates like this: Take a wormhole through space. Have one end (A) stationary, have the other end (B) moving as fast as light, or near that. This means that local conditions at B, using relativity, are almost stopped in time *when observed by A*. Theoretically, a person could fly into A in the year 3030 and emerge from B in a little over 3000, if the B exit from the wormhole had been circling at the speed of light for 30 years.

So, that's that. I don't really believe in the possibility of true time travel, because to do so you would have to re-form the position and energy state of every atom in the universe at whatever time you wanted to go to. This, of course, is excluding the infinte universes theory, but I ain't touching that with a ten foot pole.

 

[Mark]

This, of course, is excluding the infinte universes theory, but I ain't touching that with a ten foot pole.

You can't touch it anyway; I believe quantum mechanics tells us that nothing can ever really touch anything.

 

[Guest]

This, of course, is excluding the infinte universes theory, but I ain't touching that with a ten foot pole.

You can't touch it anyway; I believe quantum mechanics tells us that nothing can ever really touch anything.

Oh good, now I can stop washing my hands after I pee.

 

[Mark]

Oh good, now I can stop washing my hands after I pee.

I respect your decision, but am going to decline any attempt to shake on it.

 

[rwald]

If anyone is seriously concerned about the future-tourism argument, I can tell the example which proves it to be fallacious. But I get the impression that you guys are saying it as a joke.

My thoughts are that if time travel is possible, than either there is no free will, or (more likely) we live in a quantum multiverse (MWI). I tend to believe the latter more, but since all time machines suggested so far are effectively impossible to build, we will likely never know.

Oh well. It sure would have given a whole new meaning to that song, "I'm my own grandpa."

 

[Kimpatsu]

My thoughts are that if time travel is possible, than either there is no free will...

This is the block universe theory. Everything in the universe has already happened somewhere, such as the incident of your birth is 30 light years away from Earth 30 years after you were born, so paradoxes are impossible. The flip side, however, is that free will is therefore also impossible.

 

[rwald]

Exactly. However, quantum uncertainty makes the block universe look extremely unlikely, to say the least. That's why I hold to the many worlds interpretation (MWI).

 

[Kimpatsu]

Exactly. However, quantum uncertainty makes the block universe look extremely unlikely, to say the least. That's why I hold to the many worlds interpretation (MWI).

Absolutely right. So do I, actually, but I thought I'd throw in the block universe theory just to stir the pot. Personally, though, I find Hugh Everett's multiverse theories to be quite persuasive.
Best,