Time travel is a situation in which we can travel to any place in the universe in the least amount of time; to do that, we must travel at the speed of light. Time travel is, therefore, the concept of movement between a few points at a time, corresponding to the movement between different points in space by an object or person using an imaginary device commonly known as a time machine.
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History of the concept of time travel
Time travel is a widely recognized concept in philosophy and fiction, popular only among scientists before 1895. But then, in 1895, the idea of the time machine was first introduced in H.G. Wells’ novel “The Time Machine,” which made it popular with the general public.
Time travel mentioned in Mahabharata
The Mahabharata mentions the story of King Kakudami, who travels to Heaven to meet the creator Brahma, and when he returns to Earth, he is surprised to find that many eras have passed on Earth.
Buddhist time travel
The relativity of time is mentioned in the Buddhist Pali canon. For example, Payasi Sutta tells of Kumara Kaspa, one of the principal disciples of the Buddha, who explains to skeptics Payasi that time in Heaven passes differently than on Earth.
Time travel, according to a Japanese story.
The Japanese story “Urashima Taro” also describes time travel, in which a young fisherman named Urashima Taro goes to a palace under the sea. After three days, when he returns to his village home, he finds himself in the future 300 years ahead; 300 years have passed in his village, where he has been forgotten, his house is in ruins, and his family has died.
Time travel by a Jew
In the Jewish tradition, the first century BC scholar “Honi ha-Magel” has been said to have been asleep for seventy years. When he returns home upon waking, he does not find anyone he knows. When he tells people he has been sleeping for seventy years; no one believes his claims about who he is.
Time travel, according to physics.
Developed in 1905, the particular theory of relativity suggests that time passes at different rates for those who are growing relative to each other – although the effect only becomes more considerable when you travel at the speed of light.
Special and general relativity suggests that suitable spacetime geometries or specific types of motion in space may allow time and future travel.
Many people in the scientific community believe that the chances of traveling past time are meager. It also states that any theory allowing time travel will also give rise to possible problems. A modern example of a problem associated with this is the “grandfather paradox.” Does the grandfather paradox say that what if someone travels to a time when he kills his grandfather before his father is born?
Some physicists, such as Novikov and Deutsch, have suggested that these types of temporal contradictions can be avoided through the Novikov self-consistency theory or a change of the many-worlds interpretation.
General relativity
General relativity states that if a person returns to Earth after traveling at the speed of light in a spacecraft, only a few years will pass on the spaceship, but many years must have passed on Earth. This is known as the “twins paradox.” Because a traveler will find himself much younger than his twin after making such a journey.
Time travel in the past has theoretically been possible in general relativity and some spacetime geometries, which allow it to travel at the speed of light, such as cosmic strings, transversal wormholes, and Alcubierre drive.
The theory of general relativity suggests a scientific basis for the possibility of past-time travel in some unusual scenarios. However, semiclassical gravity arguments suggest that these flaws may be closed when quantum effects are included in general relativity. These semiquantitative arguments prompted Stephen Hawking to formulate chronological conservation hypotheses, stating that the fundamental laws of nature prevent time travel. Still, physicists have yet to get into quantum mechanics and the theory of quantum gravity to join general Without this, one cannot make definitive decisions on relativity in a fully integrated approach.
Different spacetime geometries
The theory of general relativity describes the universe under a system of field equations that determine the distance function of metric or spacetime. Exact solutions to these equations exist, including closed time-like curves, which are world lines that intersect. Due to world lines, some point in the future is also in its past, which can be described as time travel. Such a solution was first proposed by Kurt Gödel, a solution known as the Gödel metric, but his (and others) solution requires the physical characteristics of the universe, which does not seem to be the case, such as lack of rotation and Hubble expansion. Whether general relativity decreases like closed time for all relative conditions is still being researched.
Wormholes
Wormholes are an imaginary warped spacetime allowed by Einstein’s field equations of general relativity. Some scientists believe that time travel is possible using a traversable wormhole.
Anyone wanting to glimpse the future has only one problem – to come back. This would mean traveling faster than light – and this is not possible. But in general, relativity can be found in Einstein’s theory of gravitation which unites space and time as “spacetime,” which decreases in the presence of mass. This allows for the possibility of a wormhole – a kind of tunnel through spacetime that connects otherwise very distant parts of the universe.
If the “mouth” of the wormhole is moving relative to each other, crossing the bridge between different points in space will also take a passenger to a different point in the time in which they started the time travel.
However, it would still be impossible to go back and forth from the point at which the wormhole would have formed, limiting travel options somewhat – explaining why we had not yet encountered any visitors from the future.
If a natural wormhole was formed in the Big Bang, it might be possible to travel to a limited number of past and distant universe points.
Quantum physics
More limited still, theoretical work by Kip Thorne of Caltech, using partial integration of general relativity with quantum physics, suggests that any wormhole that allows time travel collapses as soon as it is created. That is, the wormhole does not last long.
Grandfather paradox
However, Thorne resolved a prominent issue that could arise due to time travel (within the range of general relativity). “grandfather paradox” involves going back in time and killing one’s own or one’s grandfather before accidentally or intentionally imagining their father – that is, stopping one’s birth, thereby it becomes impossible to eradicate the grandfather going back in time. Thorne found that no initial condition creates this type of contradiction for a point mass crossing a wormhole.
Conclusion
Time travel is the idea of going back to the past or in the future in the future. Time travel is not yet possible in the modern era, but it is used extensively in fictional stories.
Sources
- Black Holes, Wormholes and Time Travel, a Royal Society Lecture
- Time Travel and Modern Physics at the Stanford Encyclopedia of Philosophy
- Time Travel at the Internet Encyclopedia of Philosophy
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