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Time travel is a concept that has long fascinated humanity – whether it is Merlin experiencing time backwards, or religious traditions like Mohammed's trip to Jerusalem and ascent to heaven, returning before a glass knocked over had spilt its contents. A discussion of time travel should begin with a statement that humans are in fact always traveling in time – in a linear fashion, from the present to the immediate future, inexorably, until death. Time travel in fiction and thought experiments is usually meant to describe a different sort of time travel, forward at greatly accelerated rate, forward far beyond reasonable human life span, backwards to a previous time, or any travel back to the present after a time trip.
Often nowadays it is a plot device used in science fiction and many movies & TV shows to set a character in a particular time not his/her own, and explore the possible ramifications of the character's interaction with the people and technology of that time - a spin on the "country bumpkin comes to the big city" plot (or vice versa). It evolved to explore ideas of change, and reactions to it, and also to explore the ideas of a parallel universes or alternate history where some little event took place or didn't take place, but causes large changes in the future.
Famous fictional time machines include the DeLorean sports car from the Back to the Future movie trilogy, the TARDIS from the long-running British science fiction televisionDoctor Who''. Photo credit: Paul Hayes. Science fiction is perhaps the most eclectic and certainly one of the most varied of all the genres of fiction. Such is its appeal that it is not surprising it has been a popular element of television drama since it series Doctor WhoDoctor Who is a British science fiction television series, produced by the BBC and concerning the adventures of a mysterious time travelling adventurer known only as The Doctor . It is also the title of a 1996 television movie featuring the same character and the titular time machineThe Time Machine is a novel by H. Wells, first published in 1895, later made into two films of the same name. This book is generally credited with the introduction of time travel using a time machine. The Book Wells had considered the notion of time trave of H. G. Wells's novel. Wells's novel is meant to predict the likely future of humanity itself, starting with world wars and ending with humans reverting back to a Garden of Eden existence, with a terrifying twist.
In physicsPhysics (from the Greek, physikos , "natural", and physis , "Nature") is the science of Nature in the broadest sense. Physicists study the behavior and properties of matter in a wide variety of contexts, ranging from the sub-microscopic particles from whi, the " thought experimentIn philosophy, physics, and other fields, a thought experiment (from the German Gedankenexperiment is an attempt to solve a problem using the power of human imagination. These experiments are used to attempt to understand something about the universe." of time travel has been often used to examine the consequences of physical theories such as special relativitySpecial relativity (SR or the special theory of relativity is the physical theory published in 1905 by Albert Einstein. It replaced Newtonian notions of space and time, and incorporated electromagnetism as represented by Maxwell's equations. The theory is, general relativityGeneral relativity (GR or general relativity theory (GRT is the theory of gravitation published by Albert Einstein in 1915. The conceptual core of general relativity, from which its other consequences largely follow, is the Principle of Equivalence which and quantum mechanics. There is no experimental evidence of time travel, and it is not even well understood whether (let alone how) the current physical theories permit any kind of time travel.
