Dark Energy, $H_0$ and Weak Gravity Conjecture
  We point out that the physics at the extreme IR---cosmology---might provide
tests of the physics of the extreme UV---the Weak Gravity Conjecture. The
current discrepancies in the determination of $H_0$ may hint at a modification
of $\Lambda$CDM. An extension which may fit better comprises of an early
contribution to dark energy which `decays' into relativistic matter. On the
other hand the discourse on WGC to date suggests that fields which support
cosmic acceleration may produce relativistic matter after they traverse a
$\sim$ Planckian distance in field space. We explain how this offers a simple
realization of the requisite cosmic phenomenology. Thus if the resolution of
$H_0$ discrepancies is really early dark energy that ends with a shower of
relativistic matter and the current ideas on WGC are indicative, this may be a
rare opportunity to link the two extreme limits of quantum field theory.
