# Time Travel Simulation May Have Solved "Grandfather Paradox"

#### Blackwell Stith

##### See You Space Cowboy ...
Time Travel Simulation May Have Solved "Grandfather Paradox"

Always wanted to go back in time and kill your grandfather? The possible results might not be quite what you expected.

Recent experiments conducted regarding the possibility of time travel could provide a mathematical explanation for the theoretical phenomenon. The study operates using the most basic understanding of the universe, and the conclusion that time travel may be feasible could have profound implications for fundamental physics along with practical applications for quantum cryptography and computing.

The origin of time travel debate lies in the fact that our best physical theories appear to have no restrictions on backwards time traveling. Einstein's theory of relativity, which describes gravity as the warping of spacetime by energy and matter, supports that possibility. An extremely powerful gravitational field, like one generated by a spinning black hole, could warp the fabric of existence in a way that bends spacetime back on itself. This would create a "closed time-like curve" (CTC), a loop that could be traversed to travel back in time.

A model created by theorist David Deutsch in 1991 proposed the paradoxes created by CTCs could be avoided at the quantum scale thanks to the flaky quantum behavior of fundamental particles. Recently, physicist Tim Ralph from the University of Queensland and his PhD student Martin Ringbauer led a team that experimentally simulated Deutsch's model of CTCs for the first time, which tested and confirmed many aspects of the theory. Much of their simulation revolved around investigating how Deutsch's model rationalized the "grandfather paradox", in which someone uses a CTC to travel back through time to murder his or her own grandfather, thus negating his or her own existence.

The solution can be explained like this: Instead of a human being going back to kill the ancestor, imagine a fundamental particle goes back in time to reverse the particle-generating machine that created it. Due to the reversal, the machine emits a particle-the particle-back into the CTC. Deutsch insisted that any particle entering one end of a CTC must emerge at the other end with identical properties. Therefore, a particle emitted by the machine with a probability of one half would enter the CTC and come out the other end to reverse the machine with the same probability value, imbuing itself at creation with a probability of one half of going back to flip the switch.

If the particle were a person, that person would be born with a one-half probability of killing their grandfather, giving their grandfather a one-half probability of escaping demise; a good enough probability to close the loop and escape the paradox.

For more info on Ralph's and Ringbauer's findings, check out their published work in 5 Time Travel Paradoxes That Will Induce Headaches [http://www.nature.com/ncomms/2014/140619/ncomms5145/full/ncomms5145.html].

#### Pyrian

##### Hat Man
Legacy
Interesting. A quantum explanation for Anubis Gates style time-travel: you can totally go back in time and try to kill your grandfather, but you'd never actually succeed.

#### Fasckira

##### Dice Tart

This just caused a bit of brain-ache, as it still seems to allow for the paradox, albeit with a 50% less chance of it occurring?

#### songnar

##### Modulator
And today's migraine fuel, brought to you by Science!

#### DaWaffledude

##### New member
Thought I understood it, then thought about it for too long.

#### DTWolfwood

##### Better than Vash!
The grandfather paradox was always a weird concept to me. Why your grandfather? why does it have to skip a generation? I guess the "Father Paradox" doesn't sound as good?

Doesn't this assume time doesn't branch? or not considering the multiple dimensions theory? Personally i still prefer Hawkin's explanation that backwards time travel is impossible.

Or if it does work the multidimensional theory is more attractive. Any alterations you make to the pass puts you on a different "timeline." It gets rid of the paradoxes altogether. Everyone is happy

#### Pyrian

##### Hat Man
Legacy
DTWolfwood said:
Doesn't this assume time doesn't branch?
Well, yes. There's no paradox in any branching scenario.

DTWolfwood said:
Personally i still prefer Hawkin's explanation that backwards time travel is impossible.
There really isn't any reason to think it's actually possible, given that it would require quite substantial concentrations of negative energy.

#### CardinalPiggles

##### New member
[Insert Dumb and Dumber meme here]

I would love for time travel to become useable in my lifetime. But I'll settle for space travel I guess.

Heck, at this point I'm just hoping for a god damn jetpack that I can buy and use at my own discretion.

#### Jeroenr

##### New member
Noelveiga said:
That's suitably wibbly and wobbly.
don't you mean "timy whimy"?

same joke, nevermind

#### Covarr

##### PS Thanks
So within the confines of a simulation, itself based entirely on a hypothetical ruleset, it's not an issue. Good to know. But this is meaningless unless they can confirm that the experiments parameters are themselves true to life.

P.S. Thanks

#### Sigmund Av Volsung

##### Hella noided
"Mathematical understanding"

I lol'd. That's expecting that Maths is universal and still works at this sort of level. Even then, Maths only deals in absolutes, which usually relates to irrelevancies, such as this one(in this particular field mind, I'm not dismissing the entire discipline).

#### Leemaster777

##### New member

I don't know what surprises me more; the fact that scientists have found a probable answer to the Grandfather paradox, or the fact that I actually understand it.

Science, will I ever stop loving you? I hope for my sake that I do not.

#### Lagslayer

##### New member
*yawn*

Heard this a billion times before. Still sounds stupid.

"You can go back in time, because it's still somehow immune to paradoxes for reasons."

It hasn't progressed at all in decades. It's just the same handful of theories over and over again, until they come up with something stupid like string theory, which makes even less sense. It's time we accepted that black holes just have super gravity, and photons have mass.

#### Crazy Zaul

##### New member
Sounds like just a matter of semantics, not any actual new research or evidence of anything.

#### FalloutJack

##### Bah weep grah nah neep ninny bom
Sounds like an invocation of Shroedinger and Heisenberg to state that one might get away with temporalcide without the negation of personal existence, but it is uncertain how or what happens afterwards.

#### Hairless Mammoth

##### New member
Methinks someone dwelt on an episode of Futurama way too much. Call me when you can prove this. Except you won't, because even if you manage to make a time machine, a mullet-sporting Jean Claude Van Damme will come to arrest you.