QUESTION = Is time travel possible?? GENERATION = I'm no physicist, but I think the current accepted theories are: 1. Time travel is possible. There's no problem in it. We could send a person into space and back in a year. That's what happens when people "leave the earth." 2. It's theoretically possible. There's no reason to think it isn't. The closest thing we've seen that actually does this is the [Alcubierre drive](_URL_0_), which seems to work on a small scale, but it's not *impossible* either. 3. There's no reason to think it isn't possible. If you're asking "what's the point?" The point is that we don't know what it would be like to travel into the future, and the only way we know what it would be like to travel into the past is if we were able to travel back in time and get out of the gravity well. But that's not possible. And that's the point. There's no reason to think it couldn't be possible, and we're not going to try. RETRIEVAL #0 = Time travel---Carl Sagan once suggested the possibility that time travelers could be here but are disguising their existence or are not recognized as time travelers. Some versions of general relativity suggest that time travel might only be possible in a region of spacetime that is warped a certain way, and hence time travelers would not be able to travel back to earlier regions in spacetime, before this region existed. Stephen Hawking stated that this would explain why the world has not already been overrun by "tourists from the future." Several experiments have been carried out to try to entice future humans, who might invent time travel technology, to come back and demonstrate it to people of the present time. Events such as Perth's Destination Day or MIT's Time Traveler Convention heavily publicized permanent "advertisements" of a meeting time and place for future time travelers to meet. In 1982, a group in Baltimore, Maryland, identifying itself as the Krononauts, hosted an event of this type welcoming visitors from the future. These experiments only stood the possibility of generating a positive result demonstrating the existence of time travel, but have failed so far—no time travelers are known to have attended either event. Some versions of the many-worlds interpretation can be used to suggest that future humans have traveled back in time, but have traveled back to the meeting time and place in a RETRIEVAL #1 = Frequently Asked Questions About Time Travel---Tyler BULLET::::- "Magic" - performed by The Countdown Singers BULLET::::- "The Final Countdown" - performed by Eskimo Disco BULLET::::- "Humans" - performed by Ry Byron & The Gentlemen RETRIEVAL #2 = Time travel---that form closed loops in spacetime, allowing objects to return to their own past. There are known to be solutions to the equations of general relativity that describe spacetimes which contain closed timelike curves, such as Gödel spacetime, but the physical plausibility of these solutions is uncertain. Many in the scientific community believe that backward time travel is highly unlikely. Any theory that would allow time travel would introduce potential problems of causality. The classic example of a problem involving causality is the "grandfather paradox": what if one were to go back in time and kill one's own grandfather before one's father was conceived? Some physicists, such as Novikov and Deutsch, suggested that these sorts of temporal paradoxes can be avoided through the Novikov self-consistency principle or to a variation of the many-worlds interpretation with interacting worlds. Section::::Time travel in physics.:General relativity. Time travel to the past is theoretically possible in certain general relativity spacetime geometries that permit traveling faster than the speed of light, such as cosmic strings, transversable wormholes, and Alcubierre drive. The theory of general relativity does suggest a scientific basis for the possibility of backward time travel in certain unusual scenarios, although arguments from semiclassical gravity suggest that when quantum effects are incorporated into general relativity, these loopholes may be closed. These semiclassical arguments led RETRIEVAL #3 = Time travel---Earth that many ages have passed. The Buddhist Pāli Canon mentions the relativity of time. The Payasi Sutta tells of one of the Buddha's chief disciples, Kumara Kassapa, who explains to the skeptic Payasi that time in the Heavens passes differently than on Earth. The Japanese tale of "Urashima Tarō", first described in the "Nihongi" (720) tells of a young fisherman named Urashima Tarō who visits an undersea palace. After three days, he returns home to his village and finds himself 300 years in the future, where he has been forgotten, his house is in ruins, and his family has died. In Jewish tradition, the 1st-century BC scholar Honi ha-M'agel is said to have fallen asleep and slept for seventy years. When waking up he returned home but found none of the people he knew, and no one believed his claims of who he was. Section::::History of the time travel concept.:Shift to science fiction. Early science fiction stories feature characters who sleep for years and awaken in a changed society, or are transported to the past through supernatural means. Among them "L'An 2440, rêve s'il en fût jamais" (1770) by Louis-Sébastien Mercier, "Rip Van Winkle" (1819) by Washington Irving, "Looking Backward" (1888) by Edward RETRIEVAL #4 = Time travel claims and urban legends---company AMF. Section::::Travellers.:Paul Dienach. In 1921, Paul Amadeus Dienach, a Swiss-Austrian teacher, fell into a coma for a year. When he woke up, he began writing a diary that he kept secret until he contacted one of his students, Georgios Papachatzis, to translate it and keep it secret. In his writings, he claims to have awakened in the body of a man, Andrew Northman, in the year 3906 AD. According to the author, when awakened in the future, people realized that it was not Northman, and told him the events during the future period. Section::::Technology. Section::::Technology.:The Chronovisor. Chronovisor was the name given to a machine that was said to be capable of viewing past and future events. Its existence was alleged by Father François Brune, author of several books on paranormal phenomena and religion. In his 2002 book "The Vatican’s New Mystery" he claimed that the device had been built by the Italian priest and scientist Father Pellegrino Maria Ernetti. While Father Ernetti was a real person, the existence (much less the functionality) of the chronovisor has never been confirmed. Section::::Technology.:Iranian time machine. In April 2013, the Iranian RETRIEVAL #5 = Grandfather paradox---of the time traveller have no effect outside of their own personal experience, as depicted in Alfred Bester's short story "The Men Who Murdered Mohammed". Section::::Philosophical analysis. Even without knowing whether time travel to the past is physically possible, it is possible to show using modal logic that changing the past results in a logical contradiction. If it is necessarily true that the past happened in a certain way, then it is false and impossible for the past to have occurred in any other way. A time traveller would not be able to change the past from the way it "is", they would only act in a way that is already consistent with what "necessarily" happened. Consideration of the grandfather paradox has led some to the idea that time travel is by its very nature paradoxical and therefore logically impossible. For example, the philosopher Bradley Dowden made this sort of argument in the textbook "Logical Reasoning", arguing that the possibility of creating a contradiction rules out time travel to the past entirely. However, some philosophers and scientists believe that time travel into the past need not be logically impossible provided that there is no possibility of changing the past, as suggested, for example, by the Novikov self-consistency principle. Bradley Dowden himself revised the view above after being convinced of this in an exchange with the philosopher Norman Swartz. Section::::General relativity. RETRIEVAL #6 = Time travel---in these stories. The earliest work about backwards time travel is uncertain. Samuel Madden's "Memoirs of the Twentieth Century" (1733) is a series of letters from British ambassadors in 1997 and 1998 to diplomats in the past, conveying the political and religious conditions of the future. Because the narrator receives these letters from his guardian angel, Paul Alkon suggests in his book "Origins of Futuristic Fiction" that "the first time-traveler in English literature is a guardian angel." Madden does not explain how the angel obtains these documents, but Alkon asserts that Madden "deserves recognition as the first to toy with the rich idea of time-travel in the form of an artifact sent backward from the future to be discovered in the present." In the science fiction anthology "Far Boundaries" (1951), editor August Derleth claims that an early short story about time travel is "Missing One's Coach: An Anachronism", written for the "Dublin Literary Magazine" by an anonymous author in 1838. While the narrator waits under a tree for a coach to take him out of Newcastle, he is transported back in time over a thousand years. He encounters the Venerable Bede in a monastery and explains to him the developments of the coming centuries. However, the story never makes it clear whether these events are real or a dream. Another early work about time travel is "The Forebears of Kalimeros