How do astronomers measure the distances to galaxies that are millions or even billions of light-years away? I understand that trigonometric parallax can be used to measure distances out to only a couple of hundred light-years away. How do we get from there to the edge of the universe?















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"Astronomers are making tremendous progress in establishing the distance scale of the universe. For the present, however, we often are happy to use the relative distance scale, simply giving the observed redshift of a galaxy or quasar and allowing efforts to translate redshifts into absolute distances in light-years (or kilometers, or whatever) to be part of a controversy that is fun to watch."

Pasachoff suggests that interested readers might want to check out the following references:

Astronomy: From the Earth to the Universe, by Jay M. Pasachoff. Fourth edition. Saunders College Publishing, 1995.

The Farthest Things in the Universe, by Jay M. Pasachoff, Hyron Spinrad, Patrick Osmer and E. S. Cheng. Cambridge University Press, 1994



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How do astronomers measure the distances to galaxies that are millions or even billions of light-years away? I understand that trigonometric parallax can be used to measure distances out to only a couple of hundred light-years away. How do we get from there to the edge of the universe?

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