''The Green Futures of Tycho'' is a 1981 young-adult science fiction novel by WilliamSleator.

The main character is Tycho Tithonus, an 11 year-old boy. Each child in his family is named after a famous artist or scientist and their parents expect them to live up to their names. Tycho himself is named after Sleator's younger brother, who in turn, was named after Tycho Brahe, the Danish astronomer. He finds a pocket sized time machine in the family's garden. He immediately uses it to change some things from the past and to visit the future. But as he travels more and more he realizes that he is turning into something horrible and it becomes a race against time to save all of his family and himself.
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!! Contains examples of:

* AttentionWhore: Tamara [[spoiler: later {{Inverted}} after Tycho goes back in time.]]
* AxCrazy: [[spoiler: Future Tycho.]]
* BigBrotherWorship: {{Played with}} Tycho doesn't outright hate his siblings but he in no way worships any of them.
* ColdBloodedTorture: [[spoiler: Future Tycho tries to invoke this on Young Tycho]].
* EarnYourHappyEnding
* MeaningfulName
* FatBastard: Leonardo, most of the time.
* FutureMeScaresMe: Poster boy for this trope.
* JerkAss: Everyone in Tycho's family [[spoiler: before he starts messing with the past]].
** [[spoiler: Tycho later grows into one but he stops it from happening.]]
* LampshadeHanging: Done by [[TheHero Tycho]] himself regarding TimeTravel
--> Tycho: But wait, if you taught me, then who taught you-
--> Older Tycho: Shut up and concentrate.
* MacGuffin: The egg.
* PapaWolf: [[spoiler: The siblings, in a different time line, reveal they were this to Tycho before he went off the deep end.]]
* StableTimeLoop
* TimeTravel