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. jedishrfu

    Strange Time Travel Stories on Ars Technica

    https://arstechnica.com/the-multiverse/2017/07/read-some-seriously-strange-time-travel-stories-from-sci-fis-modern-masters/
  2. infinitebubble

    I Photon Sphere and time travel around a Black Hole?

    Reading the post below on event horizon of a black hole (BH) got me thinking about the photon sphere of the BH. We all know light will travel around this photon sphere and how light from a source would completely travel back to it's source if one could see it real time, we all know this from...
  3. SD das

    I GR -- about spacetime and time travel

    if GR is correct about spacetime (expanding of space) then i think time travel in back (back to the past) is impossible... suppose before 2 billion years ago (from now) the total space (volume) of universe was "X" so, it's clear that the space (volume) of the present universe must be greater...
  4. S

    Butterfly Effect: How much can you do before change occurs?

    I didn't know where to put this, but sci-fi seemed fitting: Just a hypothetical regarding the Butterfly Effect that's been puzzling me, if anyone has any insight... How much could you do in the past before your very presence started affecting history? For fun, let’s say you wake up 12 years...
  5. T

    B A Possible Challenge To Chronology Protection Conjecture?

    Correct me if I am wrong, but my basic understanding of how the Chronology Protection Conjecture (CPC) would work is that, as virtual particles created from the quantum fields of the vacuum would traverse a wormhole and arrive in the past, they would then travel back into the wormhole alongside...
  6. hsdrop

    Time travel as a way of move across the cosmos

    Hello everyone, I have been trying to learn as much physics as my little brain can handle in my off time. I have to say this forum has made a world of difference helping me do so. I would like to throw a concept out there at the risk of being told that it's nonsense and fringe science...
  7. J

    B If something stands absolutely still in the space can it time travel?

    I have a question. If something stands absolutely still in the space can it time travel?? I mean can it fall out of this universe? I am not a Physicist and forgive me for my mistakes in English.(I am foreigner) Just a question.
  8. B

    B What is the appropriate time/matter model for the universe?

    We see it frequently stated that in the subatomic/quantum world, there is no reason that the arrow of time points in only one direction, that either direction for particles is equally valid and workable. (If I am mis-stating this let me know.) But what is the model of the universe that is...
  9. V

    I Can someone explain this? (bootstrap paradox)

    Hey! I am going to do a presentation about the bootstrap paradox in a few weeks and I need some help. I understand what the bootstrap paradox is but I need some help to sum up the theory so that i becomes easy (or at least easier) to understand. If you have any examples or facts that's fun...
  10. Dheer Parikh

    B Exploring Spacetime: Can We Time Travel?

    Correct me if I am wrong and pls answer to my question .The 4th dimension is also known as SPACETIME.Does it mean that if we if are able to understand it and if we apply it,we can travel space and time?If Yes then, will we be able to construct TIME MACHINE and travel through time?and also...
  11. S

    I Time travel thought experiment

    Not sure where the best place to post this is, but here it goes. Imagine you were sent back in time, far enough back when a lot of the now known scientific laws, rules equations etc, haven't been discovered yet. You're someone who is intelligible with many scientific fields, and you have...
  12. micromass

    Who Would You Meet in a Time Travel Conversation?

    Assume you are given the following unique chance. You get to meet three people of your choosing (literally anybody) from the past or present. When meeting this person, you get to have a one hour conversation with the person. Assume language is not a problem. You cannot alter the course of...
  13. whitsona

    Objections to Previous Time Traveler's Conventions Needed

    I run a Maker group for teens at the Pensacola MESS Hall. They have decided to host a time-traveler's convention along the lines of the one hosted at MIT and by Stephen Hawking. The planning committee is looking to improve on previous design flaws in the other conventions. (Dr. Who raised a...
  14. S

    I Noticing CTC's / time travel in a Godel space-time

    I have been working with the Godel solution to the Einstein field equations which is known to contain closed time-like curves. The metric I am using is the following: ds2 = dt2/(2ω2) + (exdzdt)/ω2 + (e2xdz2)/(4ω2) - dx2/(2ω2) - dy2/(2ω2) This is sign convention (+ - - -) Now from what I've...
  15. micromass

    History Survive and Get Rich/Famous/Powerful in History: Time Travel Test

    Assume that you are being sent back in time. You can choose the exact time period, but it has to be more than 200 years ago. You cannot bring anything with you. How would you use your current knowledge in order to survive? Would you be able to get rich/famous/powerful? Note: you cannot learn...
  16. doodlendrawmn

    Time travel -- Back to the Future

    Hello, My friends and I have had about a 3 month dicussion going regarding time travel.We have to get this right. Its also something they have been debating on their podcast. The question or argument is. In the movie "Back to The Future" Marty goes back in time from 1985 to 1955.which after...
  17. Cameron MacGillivray

    B Time travel with tachyons cause infinite dilemma?

    Hi. I am a 13 years old and interested in particle science. I was reading on tachyons and how you could hypothetically send them as signals back in time (not that I'm saying we will manage anytime soon or ever). It got me think about it and I realized something. I'm sure somebody has heard about...
  18. calikazam

    What background would a time machine inventor need?

    I'm writing a story that involves a two-person team inventing and building a time machine. Essentially, Character #1 is the "big idea" type (comes up with the theory) and Character #2 does the more practical, detail work (creating and fine tuning the machine itself). If this were to happen in...
  19. Dakota

    Time Travel to Future: Is There a Minimum Speed?

    Theoretically you can travel back in time by moving faster than the speed of light, or the universal speed limit. Is there a minimum speed? 0. But with gravity you would be moving, so if you move against gravity relative to yourself you are moving. So if there was a place in the universe free of...
  20. S

    Time Travel Theory: Exploring Particle Entanglement

    So I was writing a short story and I came up with this scenario. Please pardon my Arrogance, but my theory uses several theories. I do have some sort of knowledge in Physics but here it goes. Could you, hypothetically transfer information in the form of gravitational waves between two entangled...
  21. N

    I Why teleportation, time travel, virtual reality haven't happened yet?

    (I apologize beforehand if I'm asking such an 'amateur' question , I admit that I'm not a physics student / physicist nor scientist / science student ,.. but , as just a 'normal ordinary' person, at least I am very interested in these things ,. and how I deeply wish Humanity / Mankind can 'leap...
  22. N

    Theoretical Time Travel: Explaining the Possibility

    I am writing a novel about time travel and don't quite understand the theoretical science behind it. If I understand correctly, Einstein's General Relativity theory opened up the door for the possibility of time travel even though he dismissed the idea as impractical. Einstein proved...
  23. DuckAmuck

    Does Past Exist? Conway's Game of Life & Time Travel

    I'm not exactly sure where to put this question, so admins feel free to move it. I have been reading about Conway's game of life, and learned about the halting problem. Basically, you can reach states in the game that are irreversible. Basically, the conditions at any point in time, in general...
  24. writer

    I Time dilation time travel for novel - I need a calculation

    Hi! I've written a novel in which my main character travels through time (into the future) 18 years. While the concept of time travel is necessary to the plot, the details are not. Meaning, the book isn't sci-fi, but contains elements that wouldn't normally exist in a contemporary novel, so...
  25. J

    Question about time travel to the past

    Good day to you all, I have been reading Stephen Hawking's book "A Briefer History of Time" (yes, I'm a novice ;)) and I need some verification on if my understanding is correct regarding his theory/conclusion saying that if one travels faster-than-light, he would be able to travel into the...
  26. nomadreid

    Conservation of mass-energy in time travel

    In Kip Thorne’s “Black Holes and Time Machines”, he outlines objections to using traversable wormholes, if they existed, as time machines, the main one being (roughly) that radiation could also time travel, and mount up to destroy the wormhole. But isn’t another objection the conservation of...
  27. Jaami M.

    Are light and time somehow intertwined?

    I'm wondering if time and light(entire spectrum) can only coexist simotanuously. When we look out into the cosmos and see stars they can be many light years away. Because it takes time for light to travel. That may have not been relevant. But what I'm saying is... Time is manipulated by the...
  28. GhostLoveScore

    Creating mass from nothing with time travel

    So I had one idea. Let's say that you have a cube, it's mass is 1kg and you travel forward in time 10 years and bring it back. Now you have two cubes. Then you go forward again, this time 10 years - 1 Planck time into future. Then bring that cube back again. You can repeat this infinite number...
  29. Madpoet626

    Time Travel & Unanswered Questions

    I asked myself, "what did I have for breakfast tomorrow morning", my answer, " I don't know, haven't ate breakfast tomorrow yet", so, how can forward time travel be at all possible if future events have not happened yet?
  30. T

    Can Time Travel Paradoxes be Expressed as Equations? A Scientific Inquiry

    I'm working on a Time Travel novel. Need to know if anyone can express the paradoxes as equations.
  31. TachyonRSC

    B Time Travel - Does It Create a New Dimension?

    Hello and first of all I would like to say that I appreciate your work here since I am new to this forum. So here it goes. I was wondering for a long time. Someone travels back in time somehow and let's say he goes 1000 years back. He knows the future and he makes an action to change it. Our...
  32. Invutil

    Time Travel & Gravitational Time Dilation Function

    If you square both sides of the gravitational time dilation function for non-rotating spherical bodies, do you not get a "time travel function" that allows you to travel back in time with a massive enough body like a black hole?
  33. nsaspook

    Is the Old Sock Laundromat a Hidden Time Travel Hub?

    I'd like to hear another explanation.
  34. RadPhi

    Exploring the Science of Sound: 432Hz, Just Intonation, and Cymatics

    No question. Just an intro. Hello. I'm the founder of a sound lab, experimenting with 432Hz, just intonation and cymatics. Pondering the nuances of F=1/t.
  35. H

    Hypothetical Shape of a Spacetime and Time Travel

    Disclaimer: I am an aeronautical engineer with a background in fluids. My knowledge of cosmology only extends to articles and things I read before I go to sleep. So, here is my question: I have though about time travel, as many other people have. Currently we think it may not be possible, as it...
  36. S

    Are time machines possible? (serious)

    Hello. I have read a little about time machines and going back in time, and whether that is considered possible according to modern physics. [mentor's note - some additional text not relevant to the physical question has been removed]
  37. SpanishOmelette

    Riddle Me This: Vibrating at Light Speed & Time Travel

    Riddle me this. If it was possible to vibrate at near the speed of light, would that still create the effect of time passing faster for you but your surrounding passing through time at the same rate? Just wondering. I am aware that A) Time travel backwards would not function, due to the...
  38. Auliter

    Time Travel Possibility: Scottish Scientists Slow Light Speed?

    I've recently read a report about a group of Scottish scientists have managed to slow down the speed of light, not in a certain condition but through a special mask and the particles of light can be forever slowed down. Does that means the speed we need to achieve to make time travel is slower...
  39. Suraj M

    What are the energy implications of time travel into the future?

    I'm new to all these concepts so sorry if i make any mistake in advance ! I watched a video on Nat Geo a few months ago it was about time travel into the future which is quite possible. They talked of building a track that goes around the earth. A train would go around the Earth at a very high...
  40. N

    Time Travel to the Past: CTC or Wormhole?

    In theory, is time travel to the past possible by traveling completely around the loop of the CTC (where it would seem future links with its own past) or is a wormhole the only way to time travel by way of short cutting the CTC.
  41. S

    Time Travel: Why Only to CTC's Creation?

    In theorized travel to the past -- in particular with a closed timelike curve (CTC), why is it possible to only go back in time to the point at which the CTC was created? Questions related to this would be: 1) Can space curve into a CTC if it was not originally in a CTC? 2) How can we be sure...
  42. J

    Black Holes & Time Travel: Wild Speculation

    This is wild speculation but wild speculation is fun; Do micro black holes bend space and time like their bigger siblings? Could you then use the curvature of time of such a micro black hole and a radio transmitter to send a message back through time? Regards, JDM
  43. Moriarty

    Time travel thought experiment game

    My SO showed me this on reddit and we had fun with it. If you were sent back to the early 19th century naked and alone how would you convince someone that you were from the future and not crazy? No tricks allowed (meaning you can't pull a raygun from your colon). Let's hear it.
  44. S

    Time Travel & Theory of Relativity for HS Students

    Hey guys I have an issue I was wondering if you could help me with. There was a book in my high school library about the theory of relativity and time travel. I'm trying to find it again but the fact that I don't have a title for it is making things difficult. (For the record I'm long graduated...
  45. AdityaDev

    Exploring the Time Travel Paradox: What Happens When You Meet Your Future Self?

    I was thinking about time travel...this is what i came up with ----> lets say person A (age 20,year 2014) travel to the year 2024 and meets himself (A2, age 30).lets say a kills his future A (i.e A2) and travels back in time (which i know is not possible but then). Now A is back in 2014.After 10...
  46. Eagle9

    Time Travel: Does General Relativity Allow It?

    Of course, I know that time travel is still a science fiction, but I have heard that General Relativity allows this to happen. [reminder of post removed by moderators, as it follows from a false premise]
  47. A

    Time Travel and Multiple universes hypothesis

    The Multiple universes hypothesis states that there are infinite number of universes, collectively known as the "multiverse". If a person is about to travel back in time, he will create his own parallel universe upon arrival in the past. So if he kills "his" grandfather, a paradox would not...
  48. J

    FTL, avoiding time travel issues?

    After reading about everything I can find on the subject while researching for a story, I've come to the conclusion that wormholes (or "jump" drives or gates) are the only potential "class" of FTL mechanisms which are even remotely (not a problem for fiction) plausible while also not opening the...
  49. T

    Can a book from the future save a woman's life in the past?

    An immortal woman who is about to go back in time is mailed a book from an unknown address. Inside the book reveals explicit instructions on how not to die while in the past leading up to the present day. The book is written by her future self and mailed to herself by her future self who is now...
  50. G

    Travelling to the edge of the Universe, 4th Dimensional Time Travel

    There is no edge of the Universe. Alright, I kinda realize this, I'm not a layman. However, nobody addresses what would happen if you traveled far enough. There's only a limited amount of matter out there and going off the theory that the volume of our Universe is finite, there's 'an edge'...
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