  One hundred years after its creator's birth, the Dirac equation stands as the
cornerstone of XXth Century physics. But it is much more, as it carries the
seeds of supersymmetry. Dirac also invented the light-cone, or "front form"
dynamics, which plays a crucial role in string theory and in elucidating the
finiteness of N=4 Yang-Mills theory. The light-cone structure of
eleven-dimensional supergravity (N=8 supergravity in four dimensions) suggests
a group-theoretical interpretation of its divergences. We speculate they could
be compensated by an infinite number of triplets of massless higher spin
fields, each obeying a Dirac-like equation associated with the coset
$F_4/SO(9)$. The divergences are proportional to the trace over a non-compact
structure containing the compact form of $F_4$. Its nature is still unknown,
but it could show the way to $M$-theory.
