"One day not long ago Oppenheimer stalked
up and down his office and divulged some
startling new discoveries about the 15 fundamental
particles of which the universe is made….
… physicists today are wondering if these particles
are themselves actually the final, stark, immutable
and indivisible foundation stones of the universe
that until now they have been thought to be."
—Lincoln Barnett in LIFE magazine,
Oct. 10, 1949, page 122
Fringe Physics —
"… astrophysics limits the number of fundamental particles to 15…."
— Franklin Potter at FQXi.org on Sep. 27, 2009
"I agree there can't be more than 15 fundamental particles."
— Lawrence B. Crowell at FQXi.org on Sep. 29, 2009
Beyond —
There are, at any rate, 15 "final, stark, immutable* and indivisible*
foundation stones" (namely, 15 points ) of the finite projective
space PG(3,2). See Symplectic in this journal.
For related physics, see posts tagged Dirac and Geometry.
* Update of Jan. 21, 2016 — I was carried away by Barnett's
powerful rhetoric. These adjectives are wrong.