* Redshift: When light from a distant galaxy travels towards us, it gets stretched out due to the expansion of space itself. This stretching makes the light appear redder, hence the term "redshift". The more distant a galaxy is, the more its light is redshifted.
* Expansion: The fact that *all* distant galaxies are redshifted means they are all moving away from us. This is consistent with the Big Bang theory, which postulates that the universe began in a hot, dense state and has been expanding ever since.
* Analogy: Imagine a balloon with dots drawn on it. As you inflate the balloon, the dots move further apart from each other. The dots themselves aren't moving, but the fabric of the balloon (representing space) is expanding, carrying the dots along with it.
Therefore, the redshift of galaxies provides strong evidence for the Big Bang theory and its prediction of an expanding universe.
