A newly discovered galactic structure is so large that it means one of our basic assumptions about the nature of the universe could be wrong.
You and I are really, really small. And we're even smaller than we thought we were last month, at least when compared with the size of the largest known item in the universe.
Last week, a team of astronomers based in the U.K. discovered the largest object in all of our observable existence: a celestial structure made up of 73 quasars that is up to 4 billion light years long.
How big is that exactly? Well, it would take tens of thousands of our own Milky Ways -- the big, galactic one, not the one that comes in a wrapper -- to equal the size of Huge-LQG (for Large Quasar Group), as it's become affectionately known.
Feel insignificant yet?
Yes, it does seem like something so inconceivably massive should have been noticed by now, and that's actually the most interesting part of the discovery

The discovery of an astronomical body so large throws doubt upon one of the basic assumptions of the nature of the universe. That notion, known as the cosmological principle, assumes that the little corner of the universe we're able to observe from this particular rock is a reasonable sample of what the rest of the universe must also be like.
But Huge-LQG turns out to be so huge that it makes up a few percentage points of the observable universe on its own. It's a little bit like if we suddenly discovered a 51st state that consists entirely of a single building the size of Iowa.
So not only are we less than the most insignificant of specks in our universe, we apparently don't know nearly as much about that universe as we thought.
http://news.cnet.com/8301-17938_105-57563937-1/the-biggest-thing-in-the-universe-is-really-really-big/