A tale of two distances

There are two basic ways to measure physical distances in cosmology: One based on standard candles and one based on standard rulers. Comparing current data for each method allows us to rule out axion-photon mixing and dust-extinction as the sources of supernova dimming and generally protects the case for cosmic acceleration from attacks based on loss of photons. The combined data constrains the energy densities in a LCDM model to 0.19 < Omega_m < 0.32 and 0.47 < Omega_Lambda < 0.82 (at 2\sigma) without recourse to any further data sets. Future data will improve on these limits and allow us to place constraints on more exotic physics.