Favourite SF paradoxes

[SpaceShip]

I wonder if this thread would have happened at all if I had been able to travel back in time and kill the man who discovered dynamite and the one who was careless enough to tear an atom in two!

[steve12553]

Originally Posted by SpaceShip

I wonder if this thread would have happened at all if I had been able to travel back in time and kill the man who discovered dynamite and the one who was careless enough to tear an atom in two!

Surely one of the two products saved a key ancestor of yours in a way that drew no attension and allowed you to exist to go back to.........
Hence the paradox. People don't keep near adequate notes on everday life.

[Harpo]

Originally Posted by j. d. worthington

I've seen you talk about this idea before, Harpo, and it's an interesting idea... but I have a question: How do you see it working, precisely? I mean, if the machine doesn't move, how do they travel in time? Is it physical travel? Mental travel (and if so, how does that work, since all the indications are that personality, soul, whatever you choose to call it, is an epiphenomena of the brain's functioning ... inseparable from the structure of the brain itself). And do they have any sort of interaction with the time they travel into? What happens to their atoms in the present, and where do the atoms that would comprise their being in that time come from? Etc.....

Today I discovered that Ronald Mallett has the same idea, that time machines themselves actually stay put, the time travelling is done within them.
As for how it works, ask him:
courant.com | On The Long Road To Making Time Travel A Future Reality

[Tau Zero]

Originally Posted by Andrew Hook

Of course, the paradox is: if time travel is possible then where are all the time travellers?

There are two possible answers:

1. Time travel is not possible.

2. Mankind does not survive long enough to develop the technology.

[Andrew Hook]

Has anyone here seen the movie Primer? Quite relevant to this topic I think. I loved it, but it took some time for what was happening to work it's way into my head.

[steve12553]

Originally Posted by Tau Zero

There are two possible answers:

1. Time travel is not possible.

2. Mankind does not survive long enough to develop the technology.

Or natural law forbids interfernce. Or interference does not allow memory of events with 2 results. Or.........

[Tau Zero]

I've always thought that if you're going to time travel, then you have to cross into a parallel universe. In other words, you can't go back in your own time stream, but traveling into the past takes you to a parallel universe where the differences are to slight to notice. In that time stream you can do whatever you want to change their future and when you return, you return to the time stream your left. Whatever you did in the past to the "other" universe has no effect on yours.

In this case there is no paradox. I can go into the past, meet and kill my past self and return to my present. I would still exist, because in my time stream, i never died. In the other universe, i was killed.

[manephelien]

Barring the possibility of going to different parallel universes, I believe that the past is fixed and we'll never be able to go there. The future is another matter, since it hasn't happened yet and there are nearly infinite opportunities. However, I'm not sure anyone'd care to take the risk of going 200 years into the future and find an Earth destroyed by nuclear war or climate change. If we ever build a starship that travels even at a fraction of the speed of light, relativistic time dilation effects will ensure that the people who use them will travel into the future, but that's strictly a one-way trip.

[j. d. worthington]

Originally Posted by manephelien

Barring the possibility of going to different parallel universes, I believe that the past is fixed and we'll never be able to go there. The future is another matter, since it hasn't happened yet and there are nearly infinite opportunities.

Just as a point of argument... are you sure about that last? Have you considered the possibility that the future, too, is a deterministic one, the inevitable outcome of all that has gone before... that it may in fact exist, but we just aren't equipped to see it yet (the time-frame idea)? The other tends to indicate free-will, and I'm not sure that's a valid concept, when one really examines it. Perhaps, with the uncertainties introduced by quantum physics it may be ... but I rather doubt it. Again, it may just be that we are too limited in perspective to be able to tell that whatever choice we make was already predetermined by our biological and social heritage combined with our own personality and the antecedent and circumjacent circumstances.... Something to think about, anyway.

[Mighty mouse]

Are you not just arguing from the point of view of God? a viewpoint which has to be deterministic.
Whether God exists and whether she plays dice or not aside, the universe certainly does play dice according to quantum electrodynamics and unless you are God free will for all intents and purposes therefore exists.
Is free will therefore a relativistic concept?

[ElJayDee]

If time machines are invented, I think it will be a look only device. That is it will be like a telescope you reactivate photons as they were at a particular time and you see what was. You cannot interact with or alter it.

[Paige Turner]

Originally Posted by ElJayDee

If time machines are invented, I think it will be a look only device. That is it will be like a telescope you reactivate photons as they were at a particular time and you see what was. You cannot interact with or alter it.

Or can you? Macroscope by Piers Anthony. Good book, as I recall.

[steve12553]

Check Heisenberg's Uncertainty Theory. If you measure something or view it, you affect it.