Time Travel

[Anonymous No.6395855]

Can /sci/ redpill me on Time Travel (infographics, explanations)?

Where is mankind as of today standing on this topic?

[Anonymous No.6395858]

>redpill

[StillRustled No.6395866]

>>6395855
a synopsis:

- if it's possible, it's through closed timelike curves and Novikov self consistency principle holds, see the works of Novikov, Thorne etc.
- it's probably impossible in classical gravity, but there is no general proof (chronology protection). Many think ctcs are ok in quantum gravity at the planck scale, but some mechanism prevents them at macroscopic scales.
- The region of spacetime with ctcs is separated by the region without by a lightlike cauchy horizon. It's possible this horizon is deadly. This also implies you cannot travel to before the building of the time machine.
- there are unclear solution to the EFEs which appear to have global FTL "bubbles" (warp drives) which could be used to make CTCs. However the interpretation of these metrics is unclear (coordinates can lie) and also the stress-energy requirements are very extreme and might place these solutions outside the range of validity of classical GR itself, which would invalidate the whole point.

so: probably impossible, but worth discussing for the interesting questions it spawns in GR and QG.

[Anonymous No.6395881]

>>6395866
thanks!

i read somewhere dark energy is what will keep these closed timeline curves open is that bs? is time travel possible in relation to string theory? also what is EFE and FTL

>please take it easy on me I'm trying to make the transition to /sci/ and it ain't easy

[StillRustled No.6395931]

>>6395881
>i read somewhere dark energy is what will keep these closed timeline curves open is that bs?

it's exotic matter, not dark energy. Exotic matter is a generic word to refer to some hypothetical kind of matter with the required energy-momentum densities (e.g. negative or monstrously large.) Exotic matter might as well not exist.

Dark energy, instead, is real.

Also, you just need to create the region with CTCs; they can't be destroyed, by definition of destroyed! They are loops in spacetime, they don't evolve in time, and have no end.

What you would need is to keep the wormhole open, but that means getting more and more different ctcs. Wormholes are unstable and not traversable as far as we know.

>is time travel possible in relation to string theory?

ST is also a proposal for quantum gravity, and time travel is discussed in the context of QG, so yes, it's relevant; however please note that the reasoning I made above is based on semiclassical arguments that should apply in general to any theory of quantum gravity. So strings shouldn't be able to make timetravel possible at any scale except around planck scale.

>also what is EFE and FTL

the EFEs are the Einstein Field Equations, they are the equation of motion for spacetime. Spacetime is a dynamical entity which "deforms" as time progresses; influenced also by the energy-momentum content. The EFEs tell spacetime how to evolve given a certain matter content.

global FTL means global faster than light travel, that is, going from one event to another before any light pulse. FTL is easily shown equivalent to time travel, meaning that if you could do one, you can do the other.

>please take it easy on me I'm trying to make the transition to /sci/ and it ain't easy

this place is a shithole, I don't recommend it.

[Anonymous No.6395949]

>>6395931
for the same reason why I don't understand why people argue over the internet, I also do not know why people commit such acts of altruism. Thank you.

You sir, are a gentleman and a scholar.

[Anonymous No.6396143]

>redpill

[Anonymous No.6396314]

>>6395855
>redpill
>>>/pol/

[Anonymous No.6396315]

>>6396314
wow thanks bud definitely needed you to bump this thread with such an amazing reply almost 3 hours later

[Anonymous No.6397008]

why are Schwarzschild wormholes one way? which way can you enter past->future or future->past?

[Anonymous No.6397016]

>>6395949

I understand where he's coming from. You become more apathetic to things in general, and altruism is just to kill boredom. As is being malicious. I personally find it more fun to just call OP a dumb cunt.

[StillRustled No.6397416]

>>6397008
they are not one-way. They are zero-way. You can enter from both sides, and you die inside the wormhole. You cannot go through

[Anonymous No.6397445]

>>6397008
.... huh. I don't actually know that. Rephrasing for autists (>>6397416): why do black holes always connect to white holes in Einstein-Rosen bridge theory - why don't they connect to black holes, or white holes to white holes?

>>6397008
They are one-way, but the ends can be at any position, time, orientation, or velocity relative to one another, if I understand correctly. (If momentum is conserved, how do black holes connect to white holes?)

[StillRustled No.6397473]

>>6397445
I am not being autistic, this is the point. There is no such thing as a white hole. A white hole is just a black hole described with a backwards time coordinate. And you can't traverse a wormhole, you can't get into one horizon and get out of the other.

As to why Schwartzschild black holes connect always to a white hole, that is a black hole 'flipped in time', that's just because the math says so, I guess. I also think, but I should check this, that you could so some kind of coordinate change to make it so that the black-white pair becomes a black-black pair. Meaning that there is no difference.

[Anonymous No.6397475]

>>6395855
Look up Steins;Gate.

[Anonymous No.6397627]

>>6397473
Negative time with positive energy is homologous to negative energy with positive time, and afaik there is no reason why negative energy density should be impossible.

There is no confirmed mechanism to exceed the positive energy in the surrounding area, if the Casimir effect counts, and it could destroy the universe, if the inflaton field is erratic, as string theory predicts (and which could still be true without string theory).

>I think, but I should check this, that you could so some kind of coordinate change to make it so that the black-white pair becomes a black-black pair.

Mirroring in time would do that, but that's not a Lorentz transformation so it's not trivial that doing that is allowed. I'm don't know how the connection works between black and white holes.

If you can connect a black hole to a black hole, however, I see no reason why you couldn't have particles traverse the wormhole anyway (beyond normal wormhole stuff, that is).

[StillRustled No.6397671]

>>6397627

>Negative time with positive energy is homologous to negative energy with positive time, and afaik there is no reason why negative energy density should be impossible.

no, it doesn't work like that. Energy density is not a pseudoscalar, it's the time-time component of a tensor.

>There is no confirmed mechanism to exceed the positive energy in the surrounding area, if the Casimir effect counts, and it could destroy the universe, if the inflaton field is erratic, as string theory predicts (and which could still be true without string theory).

sorry, I can't make sense of this sentence, sintactically. And I don't see how the phenomena mentioned have any relevance.


>Mirroring in time would do that, but that's not a Lorentz transformation so it's not trivial that doing that is allowed. I'm don't know how the connection works between black and white holes.

jesus fucking christ, 1) time reversal WOULD BE a lorentz transformation, and 2) there are no Lorentz transformations in a curved spacetime. This is CRUCIAL. Any diffeomorphism is allowed in GR, it's the gauge symmetry itself.

>If you can connect a black hole to a black hole, however, I see no reason why you couldn't have particles traverse the wormhole anyway (beyond normal wormhole stuff, that is).

Because the wormhole dismantles before they can go through, so there are no timelike (nor lightlike) wordlines going into one mouth and out the other.

[Anonymous No.6397682]

>>6397473
>white hole, that is a black hole 'flipped in time',
but the time reversal of a black hole is a black hole.

[Anonymous No.6397690]

>>6395855
>redpill me

Please don't use that expression.

[Anonymous No.6397695]

>>6395855

an alternative paradigm of time travel exists which depends on the actual architecture of the meta-verse, and our access to it.

"we" will likely never be able to leave this universe, but you could potentially influence others, and "upload", or rather set in motion a type of cronjob sequence onto a superverse which saves or extracts your state, regresses this universe to a previous state and overwrites your or another person's "past self" with your "future self", thus granting you the capability to travel back in time. whether you actually survived that or not is probably unprovable, but the entity that was overwritten is definitely dead.

[StillRustled No.6397721]

>>6397682
a bh and a time-flipped bh have the same metric, but a different time orientation, so they are not the same spacetime (though the same pseudomanifold)

[Anonymous No.6397730]

time doesn't exist. can someone demonstrate time without demonstrating motion?

[Anonymous No.6397754]

>rip open space-time fabric
>climb through tear you created
>end up somewhere else far away
>tear heals itself instantaneously

[Anonymous No.6397785]

>>6397721
not when you include QM

[Anonymous No.6397832]

Isn't time travel impossible.

If you define time travel as 'going into a previous state.'

You can't unbirth someone, you can't undo nuclear decay, you can't unexplode the nuclear bomb.

[Anonymous No.6397843]

>>6397832
I define time travel as "placing an effect before its cause".

[StillRustled No.6397920]

>>6397785
what are you referring to? That was a mathematical statements about spacetimes. What does QM have to do with it?

>>6397832
>>6397843
your personal opinion on the definition is not relevant in science. The definition is the presence of closed time-like curves.

[Anonymous No.6397930]

>>6397920
>what are you referring to? That was a mathematical statements about spacetimes. What does QM have to do with it?
http://arxiv.org/pdf/1401.5761v1.pdf

[StillRustled No.6397998]

>>6397930
OH JESUS CHRIST GODDAMMIT

[Anonymous No.6398041]

>>6397998
why so angry?

[Anonymous No.6398042]

am I banned?

[Anonymous No.6398052]

Isn't nearlightspeed travel a form of time-travel, as time for the traveller is passing slower than time for the rest of the world.

[Anonymous No.6398101]

I think it's theoretically possible to send a photon back in time with a network of lasers shaped like a funnel or something. Honestly I didn't understand it but some dude said it could be done, so it must be true.

[Anonymous No.6398463]

>>6397730
Time is just the measurement of two different states for the same object. There's a video that explains the difference between 2D and 3D as 2D being just one state of 3D that we can observe at any one time, and relates that to the idea of 3D and 4D (the fourth dimension being time) in that we observe in 3D and thus only see one state of the fourth dimension at any one time. Because of that, we can only observe the differences between states, and we measure that difference using the term "time".

[Anonymous No.6399665]

Why would you want to travel in time anyway? By time travel do you ,mean the standard sci-fi stuff like traveling in the past, shit like that? At any rate anything involving time travel is pure speculation and hypothesis based on some scientific grounds, but at this point its just speculation. Technically if we had a method of putting you in perfect cryogenic state and just keeping you safe for 1000 years you would technically travel in the future and you won't even be aware of it.

[Anonymous No.6400447]

>>6395866
>closed timelike curves

BWAHAHAHAHAHAHHAA

http://www.youtube.com/watch?v=NfjsLmya1PI

[Anonymous No.6401816]

>>6400447
Do you even general relativity?

[Anonymous No.6402710]

>>6397475
Who cares what some dumb assistant thinks?

[Anonymous No.6402760]

>>6401816
>Do you even general relativity?

Do you even "Propagation of time is not photon based"?