Launch! Another one from my 9 year old.
It is the same noise the elastic bands that launch their nuclear missiles make
It can be a very Hubble-ing experience. These jokes may not be funny for you, but they are Fermi.
Echosystems. From my 9 year-old.
3, duh. (My ex's 9 year old little sister told me this joke, and followed is up with: "and YOU'RE the math guy!" >< Burned.)