What is Time travel: Definition and 344 Discussions

Time travel is the concept of movement between certain points in time, analogous to movement between different points in space by an object or a person, typically with the use of a hypothetical device known as a time machine. Time travel is a widely recognized concept in philosophy and fiction, particularly science fiction. The idea of a time machine was popularized by H. G. Wells' 1895 novel The Time Machine.It is uncertain if time travel to the past is physically possible. Forward time travel, outside the usual sense of the perception of time, is an extensively observed phenomenon and well-understood within the framework of special relativity and general relativity. However, making one body advance or delay more than a few milliseconds compared to another body is not feasible with current technology. As for backward time travel, it is possible to find solutions in general relativity that allow for it, such as a rotating black hole. Traveling to an arbitrary point in spacetime has very limited support in theoretical physics, and is usually connected only with quantum mechanics or wormholes.

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  1. J

    Choosing a Session: A Physicist from the Future Drinks Rum During Q&A

    The premise is straight forward: A physicist from 100 years in the future grants a serious Q&A with physicists of today by issuing tickets whereby the questioners had to choose to attend one of three consecutive one hour sessions, A, B, or C. The physicist from the future tells everyone that he...
  2. P

    B Need help with understanding time travel

    Ridiculous! I know. But as a 9th grader, there are a few things that have been bugging me. I had a conceptualisation of how 'time travel' could work. However, it's based on the presumption ( a very large one at that) that the many-worlds interpretation of quantum mechanics is correct...
  3. Immer Tzaddi

    I Phenomena: Recent + Documented

    This might seem like a rather peculiar observation and question. However, a rather strange physical anomaly was noted about a decade ago. While gazing thorough a living-room window. A flying-insect was seen with a portion of its torso fixed within the pane of glass. It seemed, as if, it...
  4. Sarg

    B The expansion of the Universe and time travel (By a non-scientist)

    Hello I have a question about space. I am no physicist nor student of any kind of science but I'm curious and I've heard some things about the speeding up of the expansion of the universe which got me thinking... If the expansion is accelerating without end and believed to even surpass the...
  5. B

    Is Time Travel Possible with Science?

    I subscribe to this forum because I like science. I think science is the future and I don't know why but I think that time travel is possible with science. I looking article about this subject and this is amazing. I want to learning more about time travel and other science subjects. Thanks for...
  6. jedishrfu

    B Time Travel: Is it Physicsly Possible? | Scientific American

  7. jselms99

    Time Travel: Calculating Velocity for 10 Year Trip

    So at first I thought that the time would be 10 years, and that I’d have to consider the outbound motion as v = .87c and inbound motion as v = -.87c but I’m struggling with addition of the velocities and whether or not this is even the right approach?
  8. ForTheLoveOfPhysics

    Time Travel: Setup & Challenges for Safe & Accurate Travel

    I like time travel for entertainment purposes in books/movies but there’s one fundamental flaw I haven’t seen discussed. Any time travel example without the use of a ‘gate’ or wormhole (Star Gate SG1 for example) focuses on time only. The problem with these is you need to firstly travel in time...
  9. P

    A Time Travel, General Relativity & Information Paradoxes

    General relativity permits some exact solutions that allow for time travel. Some of these exact solutions describe universes that contain closed timlike curves, or world lines that lead back to the same point in spacetime. I wondered if these solutions also permits Causal loops? Such as the one...
  10. Lars Krogh-Stea

    B Energy Conservation w/ Charged Battery Time Travel

    Hi! I want to start with saying that I'm not an expert on these type of problems, but I will be gratefull for some calarifications. I've heard that there's nothing in psysics that says that time travel is impossible. I want to make a case with the time traveling battery. Could be any mass with...
  11. A

    I Time Travel in Newtonian Spacetime: Is it Possible?

    Is time travel possible in Newtonian curved spacetime?
  12. K

    A Could Altering the Past Be Possible with Time Travel?

    If time travel were possible, could someone alter or set up the way they want things to happen before they went back to their desired destination?
  13. M

    B Time Travel: Is It a Meaningless Concept?

    Assumptions: There is no "absolute" time, time is all relative. Taking the twins paradox as an example, both twins measure a different proper time when they re-unite due to each twin taking paths of differing lengths through spacetime. Conclusion: Time Travel itself is a completely...
  14. Zeeshan Ahmad

    I Time travel is a fact or fiction.?

    In my search about time travel for Is it possible or just a fictional thing as many of our estimed scientists and researchers have theoreticalize the time travel some how possible I have found some interesting information and articles regarding the the possibility of time travel and enlisting...
  15. A

    B Time travel in the quantum world

    hi users, I'm a new member of the forum. My question is about time travel in the quantum world. I am aware of the enormous limitations, but my topic is about individual particles and their ability to travel through time, is that possible for them? My question comes from a speech by an important...
  16. K

    Spacetime for non-scientists

    Summary:: Sci-Fi author looking for science advisor Hi everyone :) I have just completed the first draft of a novel and am looking for someone to review the science and confirm I'm not wildly off base, misunderstanding, or otherwise talking out of my ass before I begin the edits for the...
  17. MikeandSuch

    How to get away with killing your great grandfather with time travel

    So picture this, its 2500 and you want to time travel back to 2300 to kill your great grandfather, this obviously creates a paradox wherein you prevent yourself from being born right? Well why don't you use your year 2500 technology to create a clone of your grandfather to replace him after (or...
  18. slimak

    B Time Travel Possibility with Two Black Holes Orbiting Each Other

    The reason why I think it could happen is that spacetime is being curved really extremely in black holes and when you draw a chart of spacetime near and in black hole , you can see that time axis is being bend towards the center of black hole and that thing is happening from all sides of the...
  19. Omega0

    Paradox for time travel to the past solved?

    Hello, I am currently reading "The first Fifteen Lifes of Harry August" from Catherine Webb and really like it so far. I did not even read the half or so but there was an interesting idea I would like to discuss about. As far as I understand Harry August does return after dying to the same...
  20. M

    B Backwards Time Travel: Can We Influence Our Casual Past?

    I've got a good conceptual understanding of relativity (not maths based,) but the one thing which I can't quite get my head around is being able to influcence my casual past. I can picture being able to leave my light cone with faster than light travel, but not to the point where I could go...
  21. Shubh Goel

    B Time Travel Equation for Case B

    For case B- Conditions: 1. The observer was observing since the time they were in contact. 2. There are only 2 directions for motion: back and forward. 3. Relative velocity is not equal to zero. 4. Bodies are moving away from each other Time difference = t Relative velocity = v Distance between...
  22. Benjamin_harsh

    B What's the exact point about time travel?

    It shows theory of time machine proved, what's the exact point that stopping our scientists to create time machine in reality?
  23. bland

    I Could many worlds be a solution to time travel paradoxes?

    And also an answer to 'where are the future time travellers?'. Let's say hypothetically that in the future time travel into the past is invented. To me many worlds looks like metaphysics, but it appears to be taken seriously by physicists, therefore, what if after traveling backwards in time as...
  24. jefals

    B Time Travel: How Does a Fast Electron Experience Sunrise?

    An electron in my gold tooth travels somewhat over half the speed of light. I don't know the math, but let's say I age 10 years for every 1 year for the electron. Suppose we had a way where that electron could trigger a counter each time it "experienced" sunrise. (Let's don't get into how the...
  25. pinball1970

    Time travel using laser technology

    Professor Ron Mallett is claiming that time travel is possible using lasers. I've put this in general for a reason (I was considering putting this in the sci fi section) Article here https://www.cnn.com/travel/article/time-travel-ron-mallett-scn/index.html What I would like to ask is regarding...
  26. FireAP

    Time Travel -- The Flash or Avengers:Endgame?

    Summary:: Which form of time travel would be considered more close to reality: The Flash or Avengers:Endgame? Which form of time travel would be considered more close to reality: The Flash or Avengers:Endgame?
  27. D

    I Time travel to the Andromeda Galaxy

    Hi, I recently learned that if you can travel at the speed of light, or nearly, you can reach the Andromeda Galaxy within 30 years, due to time dilation and bypassing 2.5 million years on Earth. Is this true?
  28. K

    I Max Time Travel Date: Can We Enjoy Moments From the Past?

    Even if we manage to travel back in time, according to relativity, we could never travel to a moment before we started our journey, right? So in particular I could not enjoy some moments again with a relative that passed away, say 10 years ago?
  29. A

    A Exploring Time Travel Teleportation: Computer Bytes & Radio Signals

    Time travel teleportation can be achieved in small scale experiment in millisecond. Using a computer byte in radio signals. I look forward for comments.
  30. BobbaD

    I Can Particles Defy Time by Reaching Below Absolute Zero?

    Could a particle be sent back in time on it's world line? Time is defined by events, but at absolute zero, there is no movement or vibration of a particle - does not time cease to pass then at absolute zero for the particle? If the particle was somehow brought below absolute zero, could it be...
  31. A

    What do you think of this FTL/time travel engine?

    So, I have this idea for the FTL engine for artistic purposes and I wanted to ask if anybody could point out it's flaws. I would greatly appreciate if you were willing to discuss them further. It is just a rough summary, so if you want me to disclose more details, ask away. The idea is as...
  32. B

    B Quantum eraser and time travel

    i don't understand, how does quantum eraser not imply time travel? i firmly don't believe in retrocausality, but it really does seem to imply it . can someone please explain in layman terms? in here paul davies says observers now can "constrain" the past, does this mean our perception of...
  33. mollwollfumble

    I Connection between entropy and time travel?

    My background is that I'm an applied mathematician and engineer, self-taught in GR and QFT. It's an old idea, in some dozen or so SciFi books. But I'm looking for a mathematical framework for handling it. The second law of thermodynamics, that entropy always increases in a closed system, can be...
  34. benorin

    B How do physicists know that the past is immutable?

    I was watching a Science Channel show on time travel (though I don't recall the title) and in this show (I hope I get this right from memory, correct me if need be) they stated without proof that 'if something happened in the past is must have always have happened that way', and when they posit...
  35. Elon303

    Exploring Time Travel Possibilities in YA Fiction

    Hi I'm currently writing a YA novel where the protagonist needs to leave Earth to save his mother. Meanwhile, the protagonist's mother is back on earth. I would prefer if he could be back "instantly". Superluminal traveling is possible in this story. If the protagonists travels at...
  36. RandyD123

    B Time Travel into the Future: What Would Be the Reason?

    Although we can't technically do this currently, what if we could? What would be a reason to send a person on a mission into the future? If Bob travels at near the speed of light from Earth for let's say 5 years and then returns to see Alice. Alice has, and in fact the entire population of Earth...
  37. E

    Reporting my own post to bring this to the attention of a moderator.

    Does anybody have any references where Einstein speaks about Time Machines? From collected sources I found, he strongly rejected the idea of Time Machine but through his theory implied that time travel may be possible if wormholes existed. Something needs to be infinitely fast to do this? Have...
  38. LYCON

    I Exploring Time Travel: Is It Possible?

    How can we travel back and forth in time? And is it really possible?
  39. K

    B Is airspeed irrelevant in determining airplane travel time?

    I've seen across the internet the explanations of why (ignorind wind) the time an airplane takes to travel from one place to another on Earth is the same regardless of its direction of flight. The explanations usually rely on using reference frames. But I thought of one that I think is more...
  40. slow

    B Can time travel affect cell phone communication?

    Hi. Perhaps it falls into a fallacy similar to the attempt to deny the Second Principle of Thermodynamics, misrepresenting the statistical and probabilistic interpretation. I will also expose what causes me curiosity. My cell phone and the base of the service communicate with each other because...
  41. TheQuestionGuy14

    Question about Sci Fi Time Travel

    Hey. I know I asked questions about time travel before, but I'm just really interested in it. So, you know the phrase 'Future events cannot effect past events'. Well, in certain movies (eg. Groundhog Day) time keeps resetting, so future events don't effect past events in this scenario. So...
  42. stevendaryl

    I Using Black Holes to Time Travel Into the Future

    This is a possible science-fiction scenario, and I'm wondering if it is scientifically plausible. If someone wanted to take a one-way trip into future, say 1000 years from now, then SR gives you a possible way to do it without dying of old age: Just hop in a rocket ship, accelerate to nearly...
  43. BTA

    Why would aliens come here? (resurrected)

    I asked myself this question today, found that exact question asked here (February 10, 2005)... and I could not say anything, not even a squeak. Well, boil that dustmote! "Why would aliens come here?" I ask and the voices in my head speak. We are far from the galactic center of an average...
  44. TheQuestionGuy14

    Could Time Travel In Fiction be applied to real life?

    I've watched a lot of time travel movies, most are just pure sci-fi. Bht some movies use parallel universes to explain the time travel in the plot. Here's where my question comes in: Say if time travel ever was invented, but it created parallel universes when people went back. Would this mean...
  45. Jacinta

    Can aeroplanes be technically used as time travel machines?

    So I'm currently on holidays somewhere, and it's one hour ahead of where i live. Since i went on the areoplane and landed to a new country where the time is an hour ahead, this also means i technically landed into the future, right?
  46. G

    I Verifying claims about backwards time travel

    Now to be brief about this, I found this article at forbes (not to say that forbes is somehow a even remotely scientific journal) So I understand the part about traveling to the future when a person reaches near the speed of light (as a physical object could not reach the very speedlimit itself)...
  47. A

    B Einstein's theory of relativity and time travel

    Hey so from my understanding of Einsteins theory of relativity the closer you travel to the speed of light the slower time is for you, is that right? if it is right does that give to reason that there could be a critical speed past the speed of light for which time for the object traveling at...
  48. A

    A Question About Time Travel & Aging

    Let's assume time travel is possible and we are travelling. We jumped to a TARDIS sort of machine in August 26, 2017 and go to August 26, 2000 then lived there for 4 years until August 26, 2004. So when we come back to August 26, 2017 would we be 4 years older or be the same age we were before...
  49. A

    B Does Time Travel Affect Aging?

    Let's assume time travel is possible and we are travelling. We jumped to a TARDIS sort of machine in August 26, 2017 and go to August 26, 2000 then lived there for 4 years until August 26, 2004. So when we come back to August 26, 2017 would we be 4 years older or be the same age we were before...
  50. A

    B Is Time Travel Possible? Exploring the Speed of Light and the Nature of Time

    I just wanted to share this idea with other people who may be interested: I watched a PBS Space Time episode about the speed of light more accurately described as the speed of causality. And I Submit! That "time" is simply a interaction between atoms. And though an interaction can be...