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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What the live streaming of a time traveler will look like?

Consider a hypothetical situation: In which a time traveler travels in a spaceplane at close to speed of light circling the earth and I get a live telecast of inside of that plane to my television. ...
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2answers
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If I repeated a quantum measurement, would it be the same? [closed]

I was thinking about the probabilistic nature of quantum mechanics and that if I measured the position of an electron twice in succession, the outcomes would depend on a probability. However, what if ...
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2answers
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Why do relativistic wormholes have to be brought together to make a “time machine”?

In "From wormhole to time machine: Comments on Hawking’s Chronology Protection Conjecture" by Matt Visser (http://arxiv.org/abs/hep-th/9202090), he summarizes how "time machines" may be created from ...
4
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1answer
224 views

Closed timelike curves in the spin-2 gravity formalism

Let's say we take some topologically trivial CTC spacetime, like the Gödel metric: $$ds^2 = -dt^2 - 2e^{\sqrt{2}\Omega y} dt dx - \frac{1}{2}e^{\sqrt{2}\Omega y} dx^2 + dy^2 + dz^2$$ And then I ...
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0answers
24 views

What's the consensus on the block universe? Is time frozen? [duplicate]

What's the consensus view on the block universe? Is time frozen? Do the past and future exist? Was Einstein right when he said, “People like us, who believe in physics, know that the distinction ...
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2answers
154 views

Presentism: doesn't everything exist at the same moment? [closed]

It seems self-evident that everything exist in the Now. Notwithstanding time-dilation and different rates of the passage of time and entropy, doesn't this all still happen in the same universal ...
2
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1answer
61 views

Does Alcubierre drive allow time travel? [closed]

In Alcubierre drive, one can travel apparently faster than the speed of light by "compressing" space in front in the direction of travel. So let's say we have a stationary observer at point A, and an ...
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2answers
68 views

Detection of closed timelike curves (CTC)

I have a question. Are there any methods for detecting CTC? Is there a possibility of designing modern physics experiment in order to confirm / refute the possibility of CTC at any given time in a ...
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0answers
31 views

Can ray of light reflect from another ray? [closed]

Consider three light rays 2 parallel 1 perpendicular and source of the perpendicular ray is in between other two. If ray of light reflect from the other two rays then it must be like standing in front ...
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3answers
118 views

What would happen if you went back in time to get a random number?

For example, you go to a website that generates a random number. You get the number 8. What would happen if you went back in time a few minutes, and repeated the same actions. Would you get the same ...
1
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1answer
260 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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0answers
30 views

What would you see standing on black hole just above the event horizon ? Will you look through past and future of the universe? [duplicate]

I am trying to imagine view from my house window if it was built on the black hole;) .... Of course I am joking. If time near event horizon slows down with respect to rest of the universe. I could ...
0
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1answer
54 views

Effects of FTL travel on time [closed]

The twin paradox explains, using relativity theory, what happens to a person travelling close to the speed of light. When he returns to Earth, he finds his twin brother much older because the ...
4
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3answers
383 views

Time travel in the past

The past weeks I watched some episodes from "Through the Wormhole" with Morgan Freeman. When talking about traveling back in time, they said you can only travel back up to the date when the first ...
12
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7answers
1k views

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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3answers
100 views

Practical time travel: time dilation above the event horizon

Imagine there is a huge black hole with very small gravity gradient so that one doesn't get killed by spaghettification after even nearing the event horizon. Now imagine a very curious creature ...
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1answer
185 views

Can project LISA will bring us closer to time travel? [closed]

After looking at the current discovery of Higgs Boson and the next long term plans of NASA and ESA(European Space Agency), I can't stop myself asking about the possibilities in near future. According ...
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1answer
66 views

Time Travel possibility and Paradoxes of The Past [duplicate]

can one travel back in time and if not so, what laws prevent time travel to the past. this is quite a challenge to understand.
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1answer
96 views

Quantum teleportation + time dilation = time travel? [closed]

Thought of this a while back and thought it was pretty funny, not sure if there's been similar ideas discussed elsewhere. I can think of at least 2 reasons this won't work: 1) As far as I know, ...
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0answers
68 views

A possible proof that time traveling to the past with the aid of a wormhole is impossible?

Suppose a wormhole connects two part of the place where I live. I find myself in a spaceship attached to one side of the hole, and my wife on the other side, so we can see and talk to each other. Now ...
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1answer
114 views

Speed of light or speed of time?

Proxima Centauri is about 4.22 Light Years, so if there is anyone that could see us, the image of us would be 4.22 years old, if we depart at 99.99% the speed of light we would arrive almost instantly ...
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0answers
32 views

Travelling backwards in time - is it possible? [duplicate]

Einstein predicted that gravity bends spacetime such that travelling through time is possible; but only forward in time. According to General Relativity we can travel in the future, but not backwards ...
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4answers
2k views

Height Issues of the Time Traveler [duplicate]

A person from the year 2250 goes back in time. They go back 60 Million years, because they want to observe dinosaurs. Imagine their surprise when they see T-Rex's running around like little ...
3
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1answer
62 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 ...
3
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2answers
156 views

Why time slows only for moving object and not stationary observer? How the “stationary” & “moving” are decided? [duplicate]

Explanation for the questions in the title: According to the the (special theory of) Relativity, if an observer is stationary and sees a fast moving object then time runs faster for the observer ...
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2answers
288 views

Communication back in time?

On the wikipedia page for time travel, it mentions that Robert Forward said (theoretically, unknown since we don't have a working theory of quantum gravity) that if a heavy nucleus was subjected to an ...
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2answers
165 views

Can multiple timelines exist according to theoretical physics? [closed]

Multiple timelines is not a reality yet (as of 2016's science and technology), but exists only in Marvel/DC universe. It is something that is used to explain the paradox of time-travel. If you go back ...
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3answers
252 views

How can the past, the present and the future coexist at the same time? [closed]

We all heard it many times, the theory of Time suggest it is parallel rather than being linear. This leaves the door opened for alternate realities and well, immortality. However, even after reading ...
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2answers
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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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6answers
167 views

Wouldn't backwards time travel break the law of conservation of mass? [closed]

We know from the law of conservation of mass that the amount of mass in the universe is constant. Suppose there were a way for a person to travel backwards in time. Let's call this mass $m_t$ for some ...
3
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1answer
80 views

Kerr spacetime and Carter time machine

In the Boyer-Lindquist-Block III (inside the inner event horizon) exists the so-called Carter time machine. There we can show that for every two points $p,q$ there exists a future-pointing timelike ...
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8answers
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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
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Traveling through time, reaching the past - POSSIBLE? [closed]

I was obsessed in studying the "faith" and I've made several great discoveries. I don't want to publish anything yet, but I have a semi-proven (proven partially) / theories / so I am curious on bones. ...
2
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1answer
286 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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1answer
118 views

Time Travel: Is it Possible to return to an earlier time? [duplicate]

(Please note: I've seen some other questions asked like the one I myself am asking, I realize that I am indeed late to the party, but I am genuinely curious and none of the previous answers have ...
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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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0answers
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Traveling to the future is possible, but not to the past? [duplicate]

I understand how going to the future is possible: If you go really fast, time around you slows down for observers. But is it true that time traveling into the past isn't even theoretically possible?
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2answers
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Backwards in time?

A “Universe Today” article titled “Galaxies Are Moving Away From Us Faster than the Speed of Light” prompted the following question, which the author of the article was unable to answer: “Would such ...
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1answer
100 views

Tomorrowland movie and tachyons? [duplicate]

Would be possible if tachyonic existed to send info to the past or see the future? since the tachyons according to special relativity could travel to the past? i have searched in wikipedia and the ...
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3answers
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Is it possible to produce gravitational waves artificially?

Why don't they make a ball with irregularities, say the size of a tennis ball, then spin it very rapidly, so it would produce gravitational waves like a spinning star with irregularities on it? Is ...
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1answer
95 views

Is this a good argument against time travel? [closed]

Two fermions in two different points of space cannot be made to exist in the same point of space. It follows then that two fermions in two different times cannot be made to exist in the same time. ...
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3answers
115 views

At what rate would I travel back in time at $2c$? [closed]

I was thinking about Einstein's equations and the solutions using imaginary mass and imaginary time. How fast would I have to travel over $c$ to be traveling back in time at minus one meter per ...
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1answer
300 views

Certain doubts regarding the movie 'Interstellar' [closed]

In the movie, or rather a scientific fiction, Interstellar, we saw in the last part, that the actor falls into the black hole, travels in time, which is a dimension inside the black hole, and then, ...
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1answer
79 views

Traveling Back in Time at the End of the Universe [closed]

I apologize if this question may seem fantastical. Since the heat death of universe is said to be inevitable, is it possible to travel back in time to a younger universe when the time comes? Is that ...
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3answers
2k views

Impossibility of time travel due to energy conservation?

I just watched the movie Terminator Genisys (It wasn't as bad as people say) and started pondering time travel. While pontificating and stretching my limited remembrance of AP Physics, science ...
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2answers
174 views

Why are so many time-travel paradoxes assuming that the future is still valid? [closed]

It's a bit hard for me to explain what I mean by "the future is still valid", but bear with me. And I hope I'm not asking something incredibly stupid ;) I'll refer to my version of time travel as ...
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2answers
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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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Compactly generated vs. compactly constructed causality violating region?

I am currently trying to grasp the nuance between a compactly generated future Cauchy horizon (as per Hawking's chronological protection conjecture) and a compactly constructed causality violating ...
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2answers
42 views

Is there a time difference for people traveling at different speeds during a long period of time?

I'm just throwing this out there for discussion/answering: If person A sat in a chair all his life, in a house on earth (let's say 100 years), and person B flew around in earth's atmosphere at let's ...