Time travel is the concept of moving between different points in time, often instigated by non-trivially topology of space-time, such as a wormhole. DO NOT USE THIS TAG for questions on changes of coordinate systems, changes of time coordinate, or topologically trivial 'twin paradox' settings.

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Is This A Working Time Machine? [duplicate]

picture taken from this video for those who do not like to click on youtube links youtube video - retrocausality through Double Slit & Bose The answer will probably be no, but i am interested ...
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2answers
38 views

Does traveling through a wormhole cause you to go back in time?

Here is a hypothetical scenario: You have 2 planets A and B which are 10 light years apart. If I take a wormhole from A to B and I look at planet A through a telescope it would seem like it is 10 ...
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1answer
147 views

Wormholes and the illusion of time?

I was watching a video on Youtube by Brian Greene, "the illusion of time."http://www.youtube.com/watch?v=j-u1aaltiq4 In that video, he introduces to me the idea of a "brane," or a slice of the ...
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1answer
47 views

Time relativity / paradox [duplicate]

After watching the movie Interstellar, the theory of time relativity / paradox really mind-boggles me. If it is true that gravity controls everything even to the extent of time, then it might as well ...
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1answer
762 views

Is the “Doctor Who” spacetime affected by Hawking's chronology protection mechanism?

Recently, there has been a paper1 (and an accompanying layman-ized white paper2) on "Traversable Achronal Retrograde Domains In Spacetime", TARDIS for short. It proposes a spacetime geometry that ...
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3answers
752 views

Gödel's solutions to Einstein's relativity equations and their consequences

Gödel gave certain solutions to Einstein's relativity equations that involved a rotating universe or something unusual like that; that predicted stable wormholes could exist and therefore time travel, ...
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4answers
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Wormholes & Time Machines - for *experts* in GR/maths

EDIT: Further clarification in the context of answers/comments received to 20 Jan has been appended EDIT: 21 Jan - Response to the Lubos Expansion appended [in progress, not yet complete] EDIT: 23 ...
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1answer
58 views

If a particle travelled in a closed timelike curve, would it look like a virtual particle-antiparticle pair?

In Feynman's single-electron hypothesis, he reaches the conclusion that a particle travelling backwards in time will look like its antiparticle. So if we have a particle travelling a closed time-like ...
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6answers
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Is time travel impossible because it implies total energy in the universe is non-constant over time?

I have always argued with my friends regarding Time Travel that it is impossible. My argument has been that it will destroy the theory that all the energy in the universe is constant since when one ...
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1answer
80 views

Are Asimov's short duration spacetime “jumps” feasible? [closed]

In books of science fiction (Asimov) I saw the fancy idea of a "jump" over a space-time interval, (i.e. at superluminal velocity and for a VERY SHORT time). The result was landing in another region of ...
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2answers
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Does information paradox in the Many Worlds interpretation cause a problem? [closed]

I'm taking a philosophy of time travel class. In one of the lectures, the teacher was discussing problems with the Many Worlds interpretation. He talked about how since anything that can possibly ...
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5answers
286 views

A question about motion and time dilation

I was thinking that if you are in empty space with another person (with no other objects around), and from a distance you see that the other person is approaching you a constant speed, you wouldn't ...
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4answers
335 views

Can causality be violated?

A common justification for prohibiting many unusual phenomena such as faster than light travel is that if they were possible, causality would be violated. Let's define causality as: You cannot ...
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1answer
72 views

What will I see if I travelled to a distant planet in 100 times faster than speed of light and look back? [closed]

Consider this scenario. I enter a space ship at 10:00 AM, it starts to move at a speed 100 times faster than light, I travel for 55 mins. And then slow down to very much less than speed of light and ...
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2answers
99 views

Can you see back in time? [closed]

When you look at the stars, the light that you see is probably hundreds of years old. Which means that you don't know if they still exist. Does all this mean, that if you fly in a speed faster than ...
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2answers
452 views

Wormholes, time travel, and time dilation

I believe I understand the "wormhole time machine" now, but still have one question regarding what happens if you enter the stationary mouth. A wormhole is created and (of course) has two mouths, $x$ ...
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1answer
87 views

Navigating a Time Machine

Notes: The background for this question is working out details of a sci-fi story. Answers to the effect of "time travel isn't possible" or "FTL isn't possible" are therefore not helpful. I'm looking ...
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0answers
28 views

Are photons travelling in future? Are they lifespan 0 (or close to 0)? [duplicate]

We know that if we are going closer to speed of light, we are travelling in future. Since the photons are travelling at the speed of light, that means that they are travelling into future? Also, if ...
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1answer
65 views

How can time-travel be possible if speed is relative? [duplicate]

I have heard that time-travel is possible...relative to some observer. So, as I understand it, the following example would be accurate: There are two twins- TwinA and TwinB. Both have very accurate ...
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2answers
66 views

De facto superluminal travel?

It seems that the limitation to subluminal travel can be practically circumvented (so to speak...not breaking any physical laws here) if we consider the viewpoint of the traveler, not some outside ...
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2answers
203 views

The Alcubierre drive and closed timelike curves

Under what conditions would it be possible to create closed timelike curves, assuming an Alcubierre drive could exist? Would it be possible to have the latter without the former? See here for ...
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0answers
29 views

Are closed timelike curves generic feature of ANEC-violating stress-energy tensor?

Kip Thorne has shown that in order to create closed timelike curves (CTCs), one needs stress-energy tensor $T^{\mu\nu}$ that violates averaged null energy condition (ANEC). Will $T^{\mu\nu}$ with ...
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0answers
84 views

Thought experiment regarding perpetual motion machines and paradoxes [closed]

A paradox (Ex.: if someone goes back in time to kill their own grandfather, then they won't exist, but then they wouldn't be able to go in time to kill their grandfather, but then they WOULD exist, ...
2
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1answer
50 views

Relativistic Effects Observed with Time Travel

Disclaimer: My domain knowledge on these topics is pretty minimal. I'm a "physics fan". From what I understand about relativity. If there are two identical objects, A and B, and A is stationary and B ...
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1answer
130 views

Problem in Grandfather paradox

I am very confused about a paradox and a recent research on Quantum particles. I have read an article which states that time travel is possible for quantum particles. If it is possible then why does ...
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3answers
1k views

Time travel outside of light cone without causality violation

If one is able to travel into the past but at a spatial distance that puts him outside of his own past light cone would this be considered a causality violating trip? Looking at a Minkoski diagram, it ...
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1answer
80 views

Why could you not travel back in the time before a tipler cylinder is created?

Is it because the lightcones are not tipped all the way over in which the time axis points downwards?
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1answer
136 views

Superluminal travel without time travel

Can superluminal travel or communication be possible without leading to the possibility of closed timelike curves (CTCs) and causality violations? I have seen conflicting opinions regarding this ...
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1answer
119 views

Time travel to the past in binary black hole system

I just saw this YouTube video (only 3 mins long) of Neil deGrasse Tyson explaining what happens when two black holes collide. He says that when the black holes are rotating around each other, there ...
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1answer
405 views

Does time travel violate conservation of mass/energy? [closed]

Imagine I exist at time $t_1$ and my mass is $m$. At time $t_2$ I time travel back to $t_1$. At time $t_1$ there is now a net increase of mass/energy in the universe by $m$. At time $t_3 = t_2 - x$ ...
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3answers
130 views

Can it be considered as time travel?

India is about 8.5 hours ahead of US. If some person starts from India at 9 pm(according to his wrist watch) and reaches US in 2 hours(just assume),at that time his wrist watch will b showing 11 pm ...
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0answers
207 views

Huggins Displacement Theory and Retrocausality

I was looking at the Wikipedia entries on Time Travel and the Grandfather paradox and noticed a paragraph on the so-called Huggins Displacement Theory. I haven't been able to find the source although ...
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2answers
155 views

Is time travel different from time dilation?

I just wanted to know whether time dilation is different from time travel or not. Personally I believe both are different. If they are the same things I just wanted to know why. According to me time ...
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1answer
392 views

2 Time Dimensions [duplicate]

Our universe has 4 dimensions, 3 spacial and 1 temporal. We can add another spacial dimension and use math to explore it. I cannot think of any reason why we cannot add add another temporal ...
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2answers
325 views

Could fast vibrations cause us to travel forward in time

Assuming it's possible to vibrate a human at near light speed without harming him, would a few minutes of this from his point of view be much longer from a stationary observer's point of view? In ...
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3answers
365 views

Is my grandmother alive for some alien who is located on some place and is moving with some speed?

(I am science fiction writer. I had a goal in my novel to argue that time travel to past will not be available even in future. I asked here how to argue that. I collected answers and analyzed them and ...
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7answers
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Is time travel possible? Is it possible to go back in time?

I read somewhere that according to relativity, black holes and other space related stuff it is possible to jump into past. Is it possible for anything to go back in time either continuously or by ...
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1answer
157 views

Did physicists solve the grandfather paradox? [duplicate]

Now, physicists are trying to send information backward in time. But, why are physicists almost sure that this would happen and why are they so confident about it? Did physicists solve the grandfather ...
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1answer
240 views

Does the concept of a wormhole violate the law of mass-energy conservation?

If my understanding of wormholes is correct, anything that moves into a wormhole can be transported from one region of space-time to another. Consider a situation where an object of mass $m$ in space ...
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1answer
357 views

Time travel, is it possible? [duplicate]

I see there are many questions with this title, but this one is different, so please give it due thought: Is time travel possible? If so, Can we go both forwards and backwards in time? Paradox: I ...
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6answers
1k views

How to argue that time travel to past would not be possible even in future?

I am a science fiction writer. I know how to time travel to the future (using black hole or speed). But I need to argue in my novel that time travel to the past might not be possible. Is there a way ...
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3answers
373 views

Is travel to the distant future possible without massive energy expenditure?

Well-known physics establishes that, compared to some reference frame (I'll denote as "stationary" here), one can do several things to start at rest, end at rest, and experience less time than objects ...
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2answers
417 views

Time travel and entropy

I saw a post on reddit regarding immortality and how it would never be possible due to entropy. That said, assuming time travel was possible, would it not be possible to never reach this state of ...
5
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2answers
294 views

Is this closed time-like curve in a Godel universe a “circle”?

Would the observer moving along the circle in this Godel space-time diagram feel fictitious forces as though he is accelerating along a circular path or would he simply arrive at an earlier point in ...
8
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1answer
374 views

Energy balance of closed timelike curves in Gödel's universe

I recently read Palle Yourgrau's book "A World Without Time" about Gödel's contribution to the nature of time in general relativity. Gödel published his discovery of closed timelike curves in 1949. ...
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0answers
46 views

What happens with time at the speed of light? [duplicate]

Say that by some means you could become massless, and therefore travel at the speed of light. I understand that the closer you get to the speed of light, the slower time appears to the person ...
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1answer
137 views

Time relative to pressure? [closed]

We all know the effects of speed on time, and we have a formula for that, but I have a hunch, that time also is relative to pressure, and that by increasing the pressure on matter, in fact time will ...
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4answers
1k views

Is time travel possible? [duplicate]

Time travel -- often featured in movies, books, or facetiously in conversation. There are also theories treating time as simply another dimension, which to the layperson might imply forward and ...
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1answer
266 views

Strings and QFT: particles moving backward in time?

New question: In string theory and QFT, do particles travel back in time? Not related to antimatter: Do they travel back and forth in time in reality or are these just interpretations of mathematical ...
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3answers
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How does Time traveling work in practice?

There are multiple theories about time traveling. One is "proven": The time slows down according to your speed. The satellites in space are traveling faster than us, thus their clocks slows down a ...