Suppose that Cepheids did not exist and there were no other standard candle technique that worked at the same distances. Which statement would be true?
We would not be able to measure the distances of distant galaxies. (Cepheids provide a key link in the cosmic distance chain. Cepheids are used to measure the distances of nearby galaxies in which white dwarf supernovae have been detected, which allows us to determine the luminosities of these supernovae. White dwarf supernovae, in turn, allow us to calibrate Hubble's law. Therefore, without Cepheids, we would not be able to use either white dwarf supernovae or Hubble's law, and we would be unable to measure the distances of distant galaxies. )