Time Travel

[BertiWooster]

Does the ' Grandfather paradox ' mean that the the theory of time travel is likely to remain just that - a theory ?

Without looking it up , I recall it goes something like this - If you went back in time and killed your
Grandfather , then you wouldn't have a father - which means that you wouldn't have been born , in order to go back in time , to kill your Grandfather .

[ABerrant]

We all travel through time: it is just that we have no control over it and travel in one direction.

[jake-the-peg]

Not necessarilly.

There is nothing that fundamentally bars travelling backwards in time although there are a number of paradoxes like the Grandfather one.

Killing your own Grandfather is counter intuitive but there are a lot of things that are counter intuitive. It kind of breaks off an island of causality - that may be possible - just hard to imagine in the same way that many Quantum effects are

You also have to understand the real nature of the so called "Butterfly effect" this comes from what has been known as Chaos theory. The name comes from the idea that the flap of a butterfly's wings in New York can trigger a tornado in London.

Many systems are very sensitive to initial conditions, your presence in a past time would trigger so many subtle changes that history would change rapidly. Basically things don't come out the same way twice - go back with the lottery results you're likely to be disappointed.

However the biggest paradox is the possibility that I might travel forwards in time find a new discoverand travel back to explain it to it's inventor. ( I think this was hinted at in one of the Terminator films ) This is effectively new information coming from nowhere - much harder to live with.

If anybody is interested in the details of time travel I can recommend this video lecture by Paul Davies of Imperial college London. The Vega Trust hasit on-line here:

http://vega.org.uk/video/programme/61

Similarly

[R1Geezer]

The more obvious reason that time travel backwards will never be possible is that bookmakers exist..

[jake-the-peg]

H now Geezer that's a really interesting question!

Like I say anyone who travells back in time with a lottery ticket is likely to be in for a shock!

Don't think bookmakers would continue to take bets on boxing matches though

Not sure about football etc. I'd guess that if you re-ran many you'd get quite different games - don't know how much the game would change.

I'm not much into watching sport - How much luck do you think is involved in the final outcome? - bets on the time of the first goal and the scorer would still be good

[dustypuss]

I would love to tell you what going to happen tomorrow but I sworn by the other of time travelers not to .

[R1Geezer]

I assume jake you are refering to the split time line theory, ie if I know the result of a sporting even and travel back in time I would be travelling back but in an alternative universe where possibly the outcome was different, yes i can see how that would be necessary to avoid the grandfather paradox if indeed temporal displacement is possible. Ok just off for brunch at the restuarant at the end of the universe!

[TTG]

If you stayed in that time, you would just prevent another "you" from being born.

[jake-the-peg]

Well yes and no.

That's one "get out" but you can brazen it out too.

Imagine I go back and kill my own Grandfather.

I return to my own time - I do not exist in that time so I cannot meet myself my existance starts at a single point. To an outside observer *at that time* it seems as if I just appear.

To explain my existance you have to follow my time line from the "begining".

Yes it's surreal and doesn't make sense but is it any more difficult to accept than an electron going through two slits at the same time? or quantum entanglement? (EPR paradox)

Time dilation blew everybody's minds a centurary ago - I'd be cautious about predicting what may and may not turn out to be the case where time is involved

[BertiWooster]

I guess only time will tell as to whether or not the theory becomes reality