Among my favorite mathematical ideas are the seeming-paradoxes -- notions that require a twist and a turn and a leap before one can say "aha." Using a symbol for "nothing" is one of those leap-requiring ideas. I don't remember when I first understood zero, but I have enjoyed watching my children -- and now grandchildren -- grapple with ideas of things that are absent rather than present.
Here, from Hailey Leithauser, is a poem that celebrates the cipher.
0 by Hailey Leithauser
in its complex, ovoid emptiness,
a skillful pundit coined it as a sort
of stopgap doorstop for those
dreamt of. In form completely clever
and discrete—a mirror come unsilvered,
loose watch face without the works,
a hollowed globe
from tip to toe
unbroken, it evades the grappling
hooks of mass, tilts the thin rim of no thing,
remains embryonic sum,
"0" first appeared in Poetry (January 2003). A history of zero may be found here.