Standard Candles - Measuring Cosmic Distances:

Among the various questions we are often asked about, the one that comes to the forefront of the mind deals with how we accurately estimate how distant objects truly are from us. It"s a difficult task all together since humans are inherently incapable of truly grasping how large the distance that separates the sun from Pluto or the Oort cloud is (not to mention our crappy depth perception) -- let alone trying to wrap your mind around the 4.37 light-year gap separating our solar system and its closest neighbors in the Alpha Centauri system. Then, we must contemplate the vastness of the universe outside of our peripheral view.. like, all of the planetary systems across our galaxy at large and of our local group -- a region of space containing more than 54 galaxies. We know that much more exists beyond our local group, which brings us to the point of this article... how exactly are distances measured? Lets take a look:

First up, Cepheid variable stars: http://www.fromquarkstoquasars.com/measuring-cosmic-distances/

Image Credit: NASA/JPL/Cal-tech