Astronomers have discovered the largest known structure in the universe, a clump of active galactic cores that stretch 4 billion light-years from end to end. The structure is a light quasar group (LQG), a collection of extremely luminous Galactic Nulcei powered by supermassive central black holes.
So that’s cool and everything, but maybe some of you would be interested to know why this is a significant find? Beyond just its record-setting bigness.
Since Einstein, physicists have accepted something called the Cosmological Principle, which states that the universe looks the same everywhere if you view it on a large enough scale. You might find some weird shit over here, and some other freaky shit over there, but if you pull back the camera far enough, you’ll find that same weird and/or freaky shit cropping up over and over again in a fairly regular distribution. This is because the universe is (probably) infinite in size and (we are pretty darn sure) has, and has always had, the same forces acting on it everywhere.
So why is this new LQG so radical? (It stands for ‘Large Quasar Group,’ btw, not ‘Light Quasar Group.’)
Well, let’s try to comprehend the scale we’re dealing with. A ‘megaparsec,’ written Mpc, is about 3.2 million light years long. The Milky Way is about 0.03 Mpc across (or 100,000 light years). The distance between our galaxy and Andromeda, our closest galactic neighbor, is 0.75 Mpc, or 2.5 million light years. LQGs are usually about 200 Mpc across. Assuming a logarithmic distribution of weird shit outliers (if you don’t know how logarithmic distribution curves work, don’t worry about it), cosmologists predicted that nothing in the universe should be more than 370 Mpc across.
This new LQG is 1200 Mpc long. That’s four billion light years. Four BILLION LIGHT YEARS. Just to travel from one side to the other of this one thing. I mean for fuck’s sake, the universe is only about 14 billion years old! How many of these things could there be?
Right now it looks like the Cosmological Principle might be out the window, unless physicists can find some way to make the existence of this new LQG work with the math (and boy, are they trying). And that’s totally baffling. It would mean—well, we don’t have any idea what it would mean. That the universe isn’t essentially uniform? That some ‘special’ physics apply/applied in some places but not in others? That Something Happened that is totally outside our current ability to understand or quantify stuff happening?
By the way, no one lives there. The radiation from so many quasars would sterilize rock.
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