Redshift and Hubble's Law For very far objects (beyond about 1 billion light-years) none of the above methods work. Scientists must move from direct observation to using observations in conjunction with a theory. The theory used to determine these very great distances in the universe is based on the discovery by Edwin Hubble that the universe is expanding.
Well that's a redshift, redshift If the star is moving away By reading Doppler Shifts of all we see in the skies (clusters of galaxies, near and far) We get the big picture and a big surprise (redshifts going, redshifts going) The Universe is growing and expanding away (galaxies are speeding, speeding away) But maybe gravity will shrink it back ...
For more than ten years astronomers studied the expansion of the universe by measuring the redshift and brightness of distant supernovae. By 1998, enough information had been gathered to lead scientists to the startling discovery that the expansion of the universe is not slowing but accelerating.