What are good time travel theories to use for Science Fiction?

[scy]

Hello! Sorry, I'm not not exactly sure if this post is in the right thread. But I would just like to ask what time travel theory is appropriate, and hopefully much easier to use, for science fiction?

I am planning to write a semi sci-fi short story, and it involves using time travel: to the past, then back to the present, and then also to the future. I want to have some sort of time machine or something that can be built in an underground facility, because it is set in today's present-day world (kind of like Michael Crichton's Timeline), not in some distant futuristic world, like in most popular sci-fi, that uses hyperspace technologies.

I know that it involves ideas in SR and GR, involving FTL travels, and wormholes, and spacetime warps, but I'm not exactly sure how to integrate them well enough technically in the story (I care about details to make it realistic as possible).

I've been reading around, and I've found that a lot of this scenarios, theories, and metrics each have their own problems and "unrealistic" possibilities (CTCs, traversable wormholes and exotic matter, Hawking's chronology protection mechanism, etc.).

Are there also ideas in quantum theory that can be used? I think Crichton used "Quantum Foam" and "Quantum Entanglement" in his novel: A tech-company is trying to build a "3D fax" by using quantum computers to scan and process particle-encoding (and DNA streams for people) to deliver packages, but instead unlocked a wormhole that "delivers" things (and then later people) in Medieval France.

Also, I've read that when he was writing "Contact", Carl Sagan asked Kip Thorne for help in creating a workable wormhole for his novel, and that Thorne actually worked out the maths. So what did Thorne come up with?

So what are good time-travelling theories/concepts? What is the best one to use?

Thanks in advance!

 

[UltrafastPED]

For a layman's view see http://philclubcle.org/papers/Heighway,J19930309.pdf

Or you could read Kip Thorne's book:
https://www.amazon.com/dp/0393312763/?tag=pfamazon01-20

 

[phinds]

So what are good time-travelling theories/concepts? What is the best one to use?

Since there are no time travel concepts that are believed to actually work in the real world, what difference does it make which one you use? Just make the story interesting and wave your hand over the non-existent "science".

 

[Ryan_m_b]

Hypothetically if you make two linked wormholes, move one away at a significant fraction of the speed of light then bought it back you'd have a time machine. This configuration is called a roman ring:
http://en.wikipedia.org/wiki/Roman_ring

Note though that it would only allow you to travel set "distances" in time I.e step into one and come out of the other exactly ten years earlier. So you wouldn't have the type of free roaming time machine you get in other media, I don't think there is even a hypothetical way of achieving this.

Take heed of phinds advice though, so long as your explanation and use of the technology in your book is consistent and clever then you're good.

 

[jackmell]

Why not involve the LHC? Bet no one has done a time-travel story on it yet and after all, it is the most powerful device we have ever created. I mean even I could weave a reasonable time-travel story around it: all the scientist are a buzz slamming Lawrencium and Americium together but somehow the chamber got contaminated with . . . cobalt causing the creation of an entirely new element with very strange properties. The scientist notice . . . I'd write more but got spaghetti to babysit.

 

[Vanadium 50]

Why not involve the LHC? Bet no one has done a time-travel story on it yet

Einstein's Bridge, John Cramer.

 

[jackmell]

Einstein's Bridge, John Cramer.

Thanks, looked it up. Sounds interesting. Better plot than mine. I withdraw my suggestion.

 

[Michaelhall2007]

My advice is create your own. That actualy sounds really rude but that's not my intent. What I mean is create something that just sounds believable.
Yes, lie. But lie early. Thats the trick.
No ones going to Google the method.
Consider this. If you started reading a NEW time travel story and it read "They flipped the switch on the flucks copacitor" (And if wasnt from the BTTF franchise) would you read any further?
I enjoy reading new ideas personaly.

 

[DHF]

Since there are no time travel concepts that are believed to actually work in the real world, what difference does it make which one you use? Just make the story interesting and wave your hand over the non-existent "science".

Very true. One of my favorite examples of this was a Story where the character refused to explain it at all. When asked how the time machine worked she said any explanation she gave would be gibberish since it would reference mathematics and physics that didn't exist yet.

 

[Khashishi]

It's fun to make up theories...

I draw a distinction between coordinate time and the arrow of time. You could perhaps have loops in coordinate time due to CTC, but the arrow of time always points toward higher entropy, and the arrow of time is what drives our perception of time.

So, the existence of a portal to the past will result in the low entropy region "spilling" into the future, and rendering the original path from past into future into a weird equilibrium zone. Consider, we live in 2016 and we wanted to open a portal to 1938. I imagine what would happen is that the 1938 entropy would "spill through" the portal and our original 2016 would "become" 1938, and the original 2017 would "become" 1939, effectively short circuiting the time-line. The original link of time between 1938 and 2016 would have entropy spilling in from both sides and become some sort of equilibrium state stuck in 1938-ness. So you can't actually go into the past via CTC; they just short-circuit the timeline.

One way to get around this is to make the portal very small so only a little bit of entropy will leak through. Perhaps we need to pass the object through a refrigerator to reduce the entropy before sending to the past. I don't know, I'm just making stuff up. But for a macroscopic object iwth memories, it is possibly entangled with everything else in our universe and has a very high entropy as a result.

 

[|Glitch|]

If you want to be unusual, use "imaginary time."

https://en.wikipedia.org/wiki/Imaginary_time