Time travel, as described by most science fiction writers, would allow a person to journey anywhere into the past or the future. According to the fantasy version of time travel, if we created a time machine tomorrow, we would have the power to travel back to the time of the dinosaurs or explore what the distant future holds for humankind. Similarly, some fiction writers claim, if an advanced civilization designed a time machine many millennia from now, they would be able to venture back to our time and share with us the knowledge that took them thousands of years to develop. Yet no members of this future civilization have arrived, leading experts on the subject as notable as the physicist Steven Hawking to wonder "If time travel is possible, then where are all the time travelers?"
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