good ol' time travel paradoxes

[timeshifter]

This is a problem I have been pondering for several years now, and I always land at the same point. I just don't know if it is the right point. It's all about time travel.

If I were to go back in time and kill my mother before I was born, what would happen?

I have heard that I will cease to exist, therefore I could not have gone back in time in the first place.

However, if I did not go back in time, does that not imply that I did not kill my mother and I am still alive?

Following the pattern here, does that not also mean that since my intentions would have been the same, I DID go back in time to kill my mother before I was born?

I really hate the ideas behind time travel, but since it is looking more and more realistic, I just wanted to make sure I had the whole deal down flat.

[Grant Nockolds]

I think the unfortunate answer here is that time travel is impossible. I agree completely that the paradoxes exist however this is not the case if we can not travel BACK in time.

The mathematics says we can slow time... almost to a standstill! But it does not say that we can reverse time...

...lets think of time as only what it is - a human measurement. Then there are only three possible time references:
1. infinite past moments
2. the one and only current moment
3. infinite future moments

The laws of mathematics and the slowing of time are all working in the third time reference - the infinite future moments. It is also; perhaps coincidentally but certainly logically that the only part of time that can be changed or affected. Because what was was and what is is...but what will be - well somewhat ironically- only time will tell!!

[PhysBrain]

There has been some research done on the types of time travel scenarios that are possible under general relativity. In this research, they wanted to see if paradoxes would be allowed in these scenarios. What they have found is that, in general, the universe will act to preserve its own self-consistency. That means that it would prevent you from creating a paradox. As we all know, all possible events have a certain probability of occurring at any given instance. Some events are more probable than others, and so they are more likely to happen. What this research has shown is that if one were to try to create a paradox, or otherwise change history to something other than that which has already happened, then certain events which may not normally be very probable suddenly become very probable, and thus more likely to happen.

Examples of this would include the grandfather paradox. If you attempted to go back in time and attempt to kill one of your ancestors, then events would conspire against you, so to speak, to prevent you from accomplishing your objective (ie. the gun would jam, or you end up killing yourself accidently instead).

Naturally, this gets us into a whole nest of hornets relating to whether or not we have free will. One interpretation of this improbable event phenomenon is that we have free will within certain constraints. These constraints are that we have to obey the laws of physics and the self-consistency of the universe is a fundamental part of that. As an example, one could say that we have complete freedom of will when it comes to where we choose to move, except that we cant move through solid objects, or float through the air in defiance of gravity.)

[Grant Nockolds]

Surfing through your link to NASA propulsion program I got the distinct impression that interstellar travel is seemingly insurmountable (for the next few 100 years at least)!

They talked repeatedly about faster than light travel, however i noticed nothing about how a human being is meant to travel at these speeds without being torn apart!!! By what I don't know... gravity?

Can human beings move at the speed of light (if it where possible) and survive?

Once in space is there no G-force to speak of?

Doesn't mass increase with speed to infinite levels at the speed of light?

Here is the link that spawned these questions:

http://www.lerc.nasa.gov/WWW/PAO/html/warp/ideachev.htm

[mikenco]

Hello

I realise this is 5 years late, but hey. This IS a thread about time travel, eh?:D

With the lack of any better theory, I have a new one. "Matter Transfer Theory"

The grand father paradox says that you won't exist if you kill a member of your former bloodline, right?.. not quite.

The only way a time travel device will work is if you recreate your material structure in a previous time. What you'd need to do is create an 'instance' of yourself in your own present and send it where ever you like.

What I mean by 'instance' is everything that you are. Not only your physical makeup, but your neural structure, everything, your memories and concience, everything that makes you what you are.. not just your physical being, but your technical data, your blueprints! Can you create a data source of this magnitude and send it back in time?

Yes?.. hey cool! Send this data back in time to a 'matter reforming device'.

At this point, you will not have added any matter to the new (previous time) venue, but you'll have just reformed yourself from the matter available from the environment at the landing zone. You might leave matter behind or you might just send a 'clone' back in time? Lets assume that your time travel device will 'send' you, not just 'fax' you! If you 'send' yourself, then the resultant matter which would be left behind is not you, just the physical remnants of what you physically were, which is just a complex collection of atoms basically. Yes, you'll die at the 'present' time :rolleyes:

With the balance of matter in order, your new 'instance' will become 'stand alone', you will not be what you 'were', but something new, a time travelled 'perfect copy' (this is key!). You now have a chance to do what you like.. it doesn't matter where you came from, you exist now, that is all that matters. After all, at the moment we 'exist' our forefathers existance is irrelevant even within linear time. You have sent your 'instance' somewhere else. You can now delete your predecessors, it will have no bearing on the new 'instance' that you have now created.

Your new 'instance' (you) will have the DNA of your dearly executed forebears, but because you created something new from the environmental matter available, your future is no longer relevent to the actions of your parents. Your former self MAY be born again.. you may not, depending upon your actions.

IF you kill your grandfather, then the orignal you will not be born, but you have already created a new 'instance' of yourself in the past.. so, your actions will destroy your bloodline, but hey! you are not a part of it anymore!

[snikmij]

I take a raised eyebrow at these stories of time travel as they seem to be unreal.

I posted a question about time measurement and the answers seemed to depend on where one is.

So how time, a human invention, could be expected to exist in the real world seems rather beyond me. Agree that cosmic particles entering earths atmosphere take a long time unless special relativity is used to analyze the speed, but I'm sure the particle doesn't have a time mechanism built into it and its just a physical manifestation of this universe we live in.

Besides, if you had to invent a time machine what co-ordinates would be used? Solar latitude & longitude, earths latitude and longitude, how far the distance according to our time of orbit. Plus our sun is orbiting the galactic centre at approx. 220 km/s (if I'm remembering properly).

Ending slap bang in someones living room in time for christmas celebration could not only wipe out poor old grandfather but the rest of the family as well, either by heart attacks or by the physical manifestation of oneself inside someone, ugh:eek:.

I get the rather dubious impression that to get funding one has to postulate a possible outcome such as, um, I know time travel:cool:. In the old days it was to turn lead into gold, now we may laugh at that, but if an interest was to be pursued than a reason had to be sown to get funding, whether or not the funder actualy got what they wanted:(.