Observable universe Reference Libraries

Image Caption: The Hubble Extreme Deep Field (XDF) was completed in September 2012 and shows the farthest galaxies ever photographed by humans. Each speck of light in the photo is an individual galaxy, some of them as old as 13.2 billion years; the observable universe is estimated to contain more than 200 billion galaxies. Credit: NASA/Wikipedia What is Cosmology? I once commented to an...