#Time_travel is the concept of movement between certain points in time analogous to movement in space.
The idea of time travel is a concept of philosophy and fiction in physics.
The term "#time_machine" denotes to a hypothetical device which was popularized by H.G Well in his novel “The Time Machine”.
The concept of time travel is uncertain but however the forward time travel is extensively observed phenomenon by the framework of the Special relativity and general relativity.
When someone tends to reach the speed of light then their clock runs slowly with respect to the time in earth.
This theory was laid by Sir Albert Einstein in his theory of special relativity. A object can travel forward in time but it had to travel at the speed of light or enough close to it.
But for talking about the possibility of backward time travel, there are possible solutions in general relativity that allow for it, for example a rotating black hole.
In Mahabharata, the story of King Raivata kakudmi he was believed to travel to enough to meet Brahma and after returning to earth he was surprised y the fact that many ages have passed.
There is a story mentioned in the Buddhism, where Kumara Kassapa explains the skeptic Pyasi that time in heaven travel differently than on earth.
Similarly, there’s a Japanese Tale, of “#Urashima_Talo” a young fisherman who travels to an undersea palace. And after three days returning to home he finds himself 300 years in future.
According to Physics:
Few theories according to physics suggest specific times of motion in space that might allow time travel if such geometries are possible.
Physicist discuss the possibility of world lines that form a closed loop in space time that form a closed loop in space time that allow object to return to their own past.
There are known solution to the equation of general relativity that describes space time which contains closed time like curves, such as Gödel space-time, but the possibility is uncertain.
But if we assume a theory, that would allow time travel, but they could introduce the problems of causality for example “#The_Grandfather_Paradox”. What if one was to go back in time and kills one’s own grandfather before one’s father is conceived?
Time travel is theoretically possible in certain general relativity space time geometry but travelling at a speed faster than light such as cosmic strings and transversal wormholes.
But there is a argument of semi-classical gravity suggest when quantum effects are incorporated to general relativity the loop holes may be closed, suggesting fundamental laws of nature prevent time travel.
Gradual shift towards science fiction:
The concept of time travel has been gradually shifted to science fiction. The hypothetical device “Time machine” gradually changed to prolonged sleep as a more familiar way to travel in time.
Samuel Maddens’ Memoirs of twentieth century is a series of letters from British ambassadors to diplomats in the past describing the political and religious conditions of future. The letters were received by the Guardian Angel. As guardian angel was the first time traveler in English literature according to the book “Origins of Futuristic Fiction”.
Time travel is an interesting theory, which can rely on the physics.
But till now we are no so advanced in technology to make a real time travel machine or we can’t even certainly say that someone can travel in time.
The concept of time travel is not new this has been depicted even in the mythology too.
Despite of many uncertainties there are few theories from the theory of special relativity and general relativity which permits the time travelling but still it too has some potential problems.