TIME TRAVEL-Can it be really done? Is it posssible for us to time travel?
Is light essential factor or the dark matter and dark energy?
In theory it is possible to do time travel. There are several possibilities from theoretical point of view. Two aspects are there, travelling to the future and travel back to past. Although many scientists including Stephen Hawking said that travelling to the past is not possible (as there are several paradoxes including "the grand father paradox") that results in some weird phenomena (like in grandfather paradox, if you are allowed to travel back in time and you went to the time of your grandfather's youth and kill him then you are not going to born in the first place in future, thus a contradiction). But travelling to the future is seems possible. There are several ways to do that, thanks to The Theory of Relativity. As Einstein said, time flows at different speeds in different part of the universe, faster in Earth as compared to the near vicinity of a black hole, due to the stronger gravitational pull of the black hole then the Earth. So if you travel near to a black hole and keeping a safe distance and starts revolving around it for few hours and return back to Earth, then you will find the many decades has been passed here, due to the different speed rate of time in the two places, so essentially you are in future (but alas you cannot go back!). Another way is to travel at a very high speed (almost near the speed of light) in a spaceship for few years also take you to the future back on Earth, this is because time slows down in case you speed up. And many more concepts of time travel exists involving Wormhole and others. 

Grandfather paradox
Time travel
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