  These lectures on the cosmological constant problem were prepared for the X
Mexican School on Gravitation and Mathematical Physics. The problem itself is
explained in detail, emphasising the importance of radiative instability and
the need to repeatedly fine tune as we change our effective description.
Weinberg's no go theorem is worked through in detail. I review a number of
proposals including Linde's universe multiplication, Coleman's wormholes, the
fat graviton, and SLED, to name a few. Large distance modifications of gravity
are also discussed, with causality considerations pointing towards a global
modification as being the most sensible option. The global nature of the
cosmological constant problem is also emphasized, and as a result, the
sequestering scenario is reviewed in some detail, demonstrating the
cancellation of the Standard Model vacuum energy through a global modification
of General Relativity.
