Jawapan Paling Bijak!
Well if you can make a very long train track that circle around the earth and a train that will accelerate around the speed of light (300000km/s) which will travel around the earth circumference 7 round per second. When the train reach the speed of light, everything in the train will start to slow down. In about 100 years the train travel, passengers in the train will only experience 1 week time so this make those passengers a time traveller.
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Go build a doaremon so he can build or buy a time machine for you.