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technically it's more easy to go forward in time than in the past you simply need to travel at fast speed (but really fast : near the speed of light). The more speed you are the more heavy you become and thus you affect not only the space around you but also time.
The most efficient way would be to approach the horizon of a black hole and stay there as much as you want (time will be 10 000 times slower than on earth therefore if you stay let's say 24h --> 27 years would have passed on earth !)
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