Answer: timetravel

AnswerCrossword Clue
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Sci-fi premise

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The grandfather paradox implies that it's impossible

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Revisiting the past?

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"Doctor Who" subject
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Subject of an H.G. Wells novel
TIMETRAVELSci-fi subject
TIMETRAVELMake history, in a way
TIMETRAVEL"Back to the Future" feature
TIMETRAVEL"Back to the Future" subject
TIMETRAVEL"Back to the Future" theme
TIMETRAVELFamiliar science-fiction theme.
TIMETRAVELNot live in the present?