Deuterium Dioxide!

How to destroy a galaxy...

Q: What is Deuterium Dioxide?
A: It's heavy water!

Q: No really, what is it?
A: It's an isotope of hydrogen combined with oxygen

Q: Ok.... so what is it used for?
A: It's used as a moderator (slows down the neutrons) in a nuclear reactor

Q: And what are these pictures?
A: Ah, it's frozen deuterium dioxide (sinks in normal water)
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