When plants grow, they don't destroy the atoms that make up water (and carbon dioxide), they build new cells using them. Those cells break down when they die because the process that was supplying them with energy for homeostasis has ended. When the cells break down, those atoms are still there. If something eats them and there's water inside, they pee it out. It's always still there, somewhere.

If it's one of your biggest wishes isn't it worth the hassle? Besides, even if you study to be an astronaut and don't make it, you'll still have a strong science background to fall back on and have a career that's still pretty related to space.

The hobbit is literally FOR children. I was also not captured by the first chapter. Not to say there's anything wrong with liking it, but I enjoyed Lord Of The Rings much more.