The art of building a smooth cosmic distance ladder in a perturbed universe

Understand

How does a smooth cosmic distance ladder emerge from observations made from a single location in a lumpy Universe? Distances to Type Ia supernovae in the Hubble flow are anchored on local distance measurements to sources that are very nearby.

• We described how this configuration could be built in a perturbed universe where lumpiness is described as small perturbations on top of a flat Friedmann-Lema{\i}tre Robertson-Walker spacetime.
• We show that there is a non-negligible modification (about 11\%) to the background Friedmann-Lema{\i}tre Robertson-Walker area distance due to the presence of inhomogeneities in the immediate neighbourhood of an observer.
• We find that the modification is sourced by the electric part of the Weyl tensor indicating a tidal deformation of the local spacetime of the observer.