aurant's raisin-bread recipe by baking his own bread over and over again and tasting the final results, astronomers can figure out the expansion of the "raisin bread" universe by generating theoretical models for the relationship between redshift and brightness under different scenarios (in particular, by allowing the Hubble constant to evolve with time in different ways) and throwing away the models that don’t fit the observed data. The results obtained over the past decade very clearly favor models in which the individual galaxies are speeding up—in other words, an accelerating universe.