Funkyderek pritty much wraped it up.
To measure the close galaxies, Cepheid variables are used. To measure the most distant galaxies, the Red Shift is used... the farther away something is, the more its spectrum (as in the rainbow) is shifted toward the red side.
As an example. When you look at the light of hydrogen through a prism, you get the spectrum of hydrogen. Only hydrogen does not have all the colors of the rainbow in it - it only has a few. The colors show up as little lines in the partial rainbow.
If you look at the few colors in hydrogen, you will see them at certain distances between the Red and Blue. When you look at the colors in hydrogen when red shifted, they will all be moved over to the red side of the spectrum.
The more the spectrum is shifted to the red, the farther the galaxy.
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Regarding how the "Six literal creative days" people explain these great distances... I have come across a few who insist that it is all just an optical illusion created by god.
They say the same about the dinosaur bones: god "planted" them to create the illusion of an old earth. Others insist that the fossils are only a few thousand years old saying that fossilization only talks a few years.
I remember a web site where a creation-archeologist showed a picture of a leather cowboy boot with a "fossilized leg" in it. It was interesting, for about two seconds, before I realized that to boot itself was not fossilized. The object in the boot was also not clearly discernable as a leg.