That theory, a concept first proposed by Albert Einstein and often reiterated by British astrophysicist Stephen Hawking, seeks to find a single set of equations that can explain all the fundamental forces in the universe: gravity, electromagnetism, and the strong and weak interactive forces among subnuclear particles.
Subnuclear particles do not interact with one another.
( z1 interact :polarity - :ARG0 ( z2 particle :mod ( z3 subnuclear ) ) :ARG1 z2 )