Slashdot Mirror
Astronomers Discover a Group of Quasars 4 Billion Light Years Across
New submitter mal0rd writes "NewScientist reports a 'collection of galaxies that is a whopping four billion light years long is the biggest cosmic structure ever seen. The group is roughly one-twentieth the diameter of the observable universe – big enough to challenge a principle dating back to Einstein, that, on large scales, the universe looks the same in every direction.' For reference, Andromeda is only 2.5 million light years away."
All this observation really implies is that the true and full size of the universe is much larger than what has been documented so far.
Currently, we can observe a bubble of space around us to a radius of about 13.5 billion light years. That's as far as we can see. This may well be analogous to being at the center of a water balloon, submerged in a swimming pool of much greater volume.
We can currently see to the inner surface of that balloon, but the far greater mass of water outside of it remains hidden for now to our instrumentation.
Complex systems will always tend to appear homogenous, given enough subjective distance.
Fun fact: The rotational period of the Milky Way is approximately 200-250 million years.
The universe we currently observe is approximately 13.5 billion years old --- there is no way a spiral of such definition could form after only 50-odd rotations, and yet still be so topographically distinct from other such bodies.
That's simply not enough time.
2c
Years later, a doctor will tell me that I have an I.Q. of 48, and am what some people call "mentally retarded".
When Einstein said it looked the same in every direction, what he meant was that it's all governed by the same laws.
Actually it's more than that, it's also about the distribution of matter and energy on a large scale. It's assumed that matter is homogenous throughout the universe, homogenous literally means "no lumps" (above a certain size defined as "local" in your post). It's like an ideal gas, at the microscopic level you have all sorts of random "pressure" (kinetic energy of the individual atoms), at the macroscopic level there is just one pressure that is the same no matter what part of the gas you measure. This is because the macroscopic measurements are an average of all the individual microscopic pressures, the central limit theorem of statistics says that that the average of a big enough sample from a large population will always be very close to the real population average.
In other words the reason it's "odd" is that statistics says the observation can't be brushed aside as a fluke, if the distribution of quasars is lumpy then either the basic assumption of large scale homogeneity is wrong, or the observation is flawed. The OP's stupid question is by far the most insightful thing I've read about it so far, how are they defining the word "structure".
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.