Interpreting cosmological observations in a clumpy Universe

In the standard cosmological framework, observations are interpreted as if light propagated through a perfectly homogeneous and isotropic Universe.

However, the typical light beams involved in astronomical observations---such as supernovae---are extremely narrow, and thus probe the Universe at scales where the homogeneity principle should no longer be valid.

In this talk, I will explain how such a small-scale inhomogeneity can affect the propagation of light through the cosmos, and thus the interpretation of our observations.