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.

learn more… | top users | synonyms

-2
votes
0answers
40 views

Time travel, could it destroy the Universe? [on hold]

One Universe, One mass. In order for "Mass" to be created, (not matter, not energy, but MASS) a creation point where new mass is Incorporated must exist. No "creation" point has ever been observed. ...
-5
votes
0answers
58 views

Energy manipulation [closed]

Haha, I don't want to offend anybody, but I want to make a superhero that can control all forms of energy. From what I've heard you can do a lot like, manipulate time and space, open blackholes, ...
10
votes
6answers
438 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 ...
0
votes
1answer
68 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 ...
1
vote
2answers
53 views

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 ...
1
vote
1answer
55 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 ...
-3
votes
2answers
88 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 ...
5
votes
2answers
283 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, $x$ ...
-1
votes
1answer
79 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 ...
0
votes
0answers
23 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 ...
0
votes
1answer
58 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 ...
1
vote
2answers
61 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 ...
3
votes
0answers
24 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 ...
1
vote
0answers
61 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, ...
1
vote
2answers
162 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 ...
2
votes
1answer
47 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 ...
0
votes
1answer
119 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 ...
2
votes
4answers
220 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 ...
9
votes
3answers
957 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 ...
0
votes
1answer
72 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?
1
vote
1answer
106 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 ...
1
vote
1answer
96 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 ...
0
votes
1answer
236 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 $t_3 = t_2 - x$ ...
1
vote
5answers
222 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 ...
-3
votes
3answers
116 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 ...
2
votes
0answers
158 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 ...
0
votes
2answers
112 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 ...
1
vote
1answer
307 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 ...
4
votes
2answers
203 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 ...
6
votes
3answers
314 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 ...
0
votes
1answer
151 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 ...
12
votes
0answers
691 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 ...
2
votes
1answer
204 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 ...
16
votes
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 ...
5
votes
2answers
277 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 ...
0
votes
1answer
336 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 ...
0
votes
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 ...
-3
votes
1answer
118 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 ...
0
votes
1answer
231 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 ...
0
votes
0answers
30 views

Possibility of Time Travel? [duplicate]

Is time travel still considered as a possibility? What does the newer theories like string theory, M theory, etc. say about it.
1
vote
0answers
123 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 ...
0
votes
1answer
579 views

Faster than the speed of light and future travel [closed]

I had read somewhere that if a person attains twice the speed of light, he can actually reach the future. But since the world belongs to one time and space, how will it change for one particular ...
4
votes
2answers
275 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 ...
15
votes
3answers
6k views

How does faster than light travel violate causality?

Let's say I have two planets that are one hundred thousand lightyears away from each other. I and my immortal friend on the other planet want to communicate, with a strong laser and a tachyon ...
-1
votes
1answer
106 views

Grandfather Paradox [closed]

This question related to the Grandfather Paradox. Assume that time travel to the past is a reality. What experiment/test could the time traveler perform in order to determine if he is in his own ...
0
votes
2answers
86 views

If airplanes' highest speed depends directly on the air it is moving through and not the ground,

If airplanes' highest speed depends directly on the air it is moving through and not the ground, does it mean we can build a time machine if only the air moves near the speed of light?
5
votes
2answers
255 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 ...
1
vote
2answers
1k views

Does Stephen Hawking not believe in Negative movement? [duplicate]

Possible Duplicate: Is it possible to go back in time? Is time travel possible? According to Stephen Hawking, time travel to the future is not only possible but proven, however time ...
0
votes
4answers
132 views

Messing with the past: Endless loop, or alternate timelines? [closed]

Let's take the following scenario: A person finds a time machine. He uses it to travel to the past, and kills his grandparents. Now because of this, his parents are never born, they do not ...
-4
votes
1answer
166 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 ...