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[darius]

realistic timetravel

What about wormhole time travel? As far as i remember it allows (theoretically) to travel back in time but not before wormhole was constructed.

The problem is, wormholes aren't realistic. Outside of possible quantum froth behaviour (which is so small that if it was scaled up to the point where it would be of an observable size, an atom scaled by the same amount would be larger than the observable universe), wormholes are generally accepted as requiring either a type of matter that has no theoretical or observed reason to exist, crossing a literal point of no return (with the other end also being inside such an event horizon) or otherwise requiring manipulations of spacetime that beggar the imagination.

They were saying similar stuff about 1ghz cpu: It is impossible, no materials could work at this frequency, etc etc...
I know that is it is veryyyy far fetched. Hell we even don't know for sure (100%) if black holes exist (we will when we will go near one). But i hope that at least one of these is possible: negative mass mater, charged rotating black holes, mass effect like matter, tachyons and few others i don't remember from times i was looking into this stuff

[Osmosis Jones]

The objections to processor clock speeds were engineering ones, not violations of physical laws.

Also, for the other methods: negative mass matter has never been observed. Even if it did exist, it would experience a negative gravitic force; e.g. it would be repelled from our positive mass galaxies, meaning we'd never encounter it.

Tachyons are purely theoretical constructs. I haven't heard of mass effect matter, but I assume that is too.

Charged rotating blackholes, assuming our modelling of the singularity is even valid, require crossing the event horizon. So yes, you could probably go back in time, but I hope you like that black hole, because that is where you'd be staying.

Infinitely long, infinitely dense rotating cylinders (which is another method that mathematically holds) are bollocks for obvious reasons.

...and so on and so forth.

[darius]

Don't forget that laws as we know it are made by humans, humans sometimes makes errors. Well maybe then we have unified field theory that is accepted by everyone then i could rest easy and say there is no room for time travel.

And about

Charged rotating blackholes, assuming our modelling of the singularity is even valid, require crossing the event horizon. So yes, you could probably go back in time, but I hope you like that black hole, because that is where you'd be staying.

I'm not so sure of my expertise but AFAK thats the main diffrence between non rotating and rotating black holes. this is the pic i remember, but it is purely theoretical.

As for

negative mass matter has never been observed. Even if it did exist, it would experience a negative gravitic force; e.g. it would be repelled from our positive mass galaxies, meaning we'd never encounter it.

Antimatter was also not observed, due to matter antimatter annihilation. But maybe in far future we could make some? Even if we never encounter it. Oh and now i see another little problem... Putting negative mass matter into the black hole

[Starver]

I've been involved in discussions of RL time-travel, recently, and on forums not primarily DF-facing, so I won't go into that.  But for a game-perspective.

Time travel back to a prior (possibly specially 'placemarked', with accompanying save-data issues) point of time could be treated as "New Branch of causality, future not necessarily determined by passage of old branch".  Some things (characters accompanying a wagon) could be the same if no on-screen or off-screen events act differently in the various randomness/player-interaction levels.  Obviously if one's "one back in time" character killed one of them, then it would be different.

As for self-on-self interactions, maybe the Handwavium-powered time machine/magical device can only send matter back to where that matter was originally (give or take), overlaying experience and (soon to be invalidated) memories upon the person's original body, so that in the new branch there is still the same character, but with knowledge (and body mass/scars) strength.  The 'original' character still resides in the original branch, leading up to the point of return, but is inaccessible to this older character's experience.  It's all different.  You can't wander around and then meet up with the previous branch's character at the place he built his castle.

Travel back beyond the lifetime of the character may either be not allowed or would produce one (from 'nothing') fully capable of killing any number of identifiable ancestors without phasing out his or her own existence, as he/she is born of the original (now not going to happen) timeline, not of the one he or she is helping to form afresh, within which there may or may not be a person that is their younger self.  And if that younger self does arise, then they're a game-controlled 'zombie', and need not (the excuse being that traveler-self has changed the environmental influences?) follow anything like the same path in life as the traveler followed to reach the point of departure.

This is not how I see 'RL' time travel happening (I have this "static tapestry of time" idea in mind, which requires a meta-existence and entire-history overview to ensure this is stable), and is more of a standard lazy-style fictional fudge than anything fully consistent, but it would be a viable solution for game stability with a time-travel option.  IYSWIM

[Osmosis Jones]

Antimatter has been observed, can be made on a regular basis (albeit for a huge energy cost), and in truth it really isn't that spectacular. Just imagine a hydrogen atom with the charge of the electron and the proton swapped; BAM anti-hydrogen.

Also, reading that page on which the image was posted, it isn't actually clear on whether or not the event horizon is re-traversable, and the only reference I have is the word of my physics lecturer, I can't definatively rebut that. That said, there are other problems with that model, which are addressed in the attached quotes from said page.

Spoiler (click to show/hide)

Penrose diagrams for rotating and/or electrically charged black holes reveal "inner event horizons" (lying in the future) and vertically oriented singularities, which open up what is known as a "time-like wormhole" allowing passage into future universes.

1) This does not describe a typical black hole created from the collapse of a star (which cuts off the past-oriented "white hole" geometry and other universe). Such wormholes would only be possible if a "past singularity" (such as a remnant of the original Big Bang singularity that remained compact) continued erupting into the universe as time went on.

2) The radiation of orbiting, highly blue-shifted light rays surrounding a black hole (called a "blue sheet") would make it impossible for anyone to pass through, and in fact might create another kind of singularity outside the hole!
 

I also apologise to the OP for going off topic. What can I say, I love a good debate :p

[darius]

Antimatter has been observed, can be made on a regular basis (albeit for a huge energy cost), and in truth it really isn't that spectacular. Just imagine a hydrogen atom with the charge of the electron and the proton swapped; BAM anti-hydrogen.

I'm sorry i wrote not what i wanted. Supposed to be more like this:

Antimatter was also not observed, due to matter antimatter annihilation.<end of antimatter example>Applying to negative mass: maybe in far future we could make some? Even if we never encounter it. Oh and now i see another little problem... Putting negative mass matter into the black hole

I also apologise to the OP for going off topic. What can I say, I love a good debate :p

me too  
That being said I have no further arguments for discussion. Only thing I fear that nobody will read/discuss my proposal for implementing time travel few posts before. 

[Cruxador]

That being said I have no further arguments for discussion. Only thing I fear that nobody will read/discuss my proposal for implementing time travel few posts before. 

The post two above yours proposes the same method. The post one above yours refutes it. A method which would work was proposed by the OP. I clarified it later in the thread, since people were ignoring it and suggesting things which couldn't work or did not apply. Rather than being sad that no one is replying to you, perhaps you would be better served by reading the thread and ascertaining why your response does not merit a response?

[darius]

And the first part of my post gives an example how it could work ( instead of using 564GB).
Op did suggest a method to implement time travel, but i think it's not time travel at all it's just "let's play world at year X". Although i have nothing against it and fully support this idea, i have suggested alternatives. Few more possible then other.

As for "two post above" it only talks about size and saving the world every day. Not sure what you meant. Sorry if i wasn't clear.

[Zironic]

Scientist from past says the speed of sound is unsurmountable

Scientist from the present says the speed of light is the limit

Scientist from the future says to buy Google.

[Cruxador]

And the first part of my post gives an example how it could work ( instead of using 564GB).
Op did suggest a method to implement time travel, but i think it's not time travel at all it's just "let's play world at year X". Although i have nothing against it and fully support this idea, i have suggested alternatives. Few more possible then other.

As for "two post above" it only talks about size and saving the world every day. Not sure what you meant. Sorry if i wasn't clear.

The only difference between your post and that one is that you suggest auto-deleting save states. Other than that, it's identical.
Playing the world at year X is essentially what time travel is. The only distinction is a persistent character. All other information is associated with worldgen histories.

[nenjin]

I'm imagining loading up DF....

Seeing an option called God mode....

And seeing 400 entries for a 400 year old world. Now I'm imaging picking year 152...12th Moonstone...stabbing the Inn Keeper in the face....hitting save....waiting 45 seconds...

Then being back at the main menu. Then reloading and seeing the same 400 entires and having no idea how I actually impacted history.

That's how I see this ending up working practically. It's not really impossible...I just don't think it would be as streamlined or interesting as people think it should be. I think the idea of hitting Shift+T, punching in some numbers and only waiting 30 seconds for the game to figure things out is pretty unrealistic. The only realistic way, I think, involves a lot of unpacking and repacking of data. That takes time and usually doesn't lend itself to being done in game. 

[Cruxador]

I'm imagining loading up DF....

Seeing an option called God mode....

And seeing 400 entries for a 400 year old world. Now I'm imaging picking year 152...12th Moonstone...stabbing the Inn Keeper in the face....hitting save....waiting 45 seconds...

Then being back at the main menu. Then reloading and seeing the same 400 entires and having no idea how I actually impacted history.

That's how I see this ending up working practically. It's not really impossible...I just don't think it would be as streamlined or interesting as people think it should be. I think the idea of hitting Shift+T, punching in some numbers and only waiting 30 seconds for the game to figure things out is pretty unrealistic. The only realistic way, I think, involves a lot of unpacking and repacking of data. That takes time and usually doesn't lend itself to being done in game. 

I'm not sure anyone proposed being entirely detached from time. The following is approximately what the first suggestion would boil down to:

You start up DF, see an option labeled God Mode. You select whatever character options there happen to be, and among them, you choose time as a sphere of influence. Now, if you need to, you can move around in time. Perhaps this ability requires the construction of some sort of time portal, perhaps not. You can go into the past (loadtimes ~30 seconds) or the future (several minutes, depending on how far) by any amount you choose. Of course, this ability is of limited usefulness - anything you do in the past affects the future in unpredictable ways (because you restart worldgen when going forward).