The long-running series in which readers answer other readers’ questions on subjects ranging from trivial flights of fancy to profound scientific and philosophical concepts

Must what goes up always come down? Sadia, via email

Send new questions to nq@theguardian.com.

I like Douglas Adams’ idea of flying: to throw yourself at the ground and miss. LMCollis

Yes. Although sometimes it can be: fall back to ground and miss, which we call “being in orbit”. HaveYouFedTheFish