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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."
What exactly makes this "a structure"? All linked gravitationally or what?
Using one as a reference point for the other in four-dimensional space makes little sense to me.
It's being used as a reference distance.
systemd is Roko's Basilisk.
Based on the map in the linked article, it appears that this Quasar has an angular diameter of about 10 degrees. The moon is about 0.5 degrees. So if the magnitude was high enough to be visible, this structure would be the size of a constellation. Of course, if it was that bright, it would have fried most of the observable universe.
Have gnu, will travel.
Consider all the entities [stars, galaxies, or whatnot] in your study as points in 3-space. The descriptive length of the data is the total number of bits that describes the location of all points in your study.
If all points are random and evenly distributed, then the total number of bits required is (number of points)x(number of bits for 1 location).
Suppose you notice a clumping of points. Is this a structure or random variation?
Rework your data description as follows: for any point, use the first bit to determine whether a point is a member of the clump or not, and subsequent bits to complete the description, depending on whether the point is in the clump.
For this description, the total number of bits required is 1x(total number of points) + (number of points in clump)x(number of bits for location relative to clump) + (number of points not in clump)x(number of bits for general location).
If the 2nd description is shorter than the 1st description, then by Occam's razor the second description is more likely correct.
In fact, the number of bits directly tells the probability that the 2nd description is correct: if the 2nd description requires 10 fewer bits (total) than the 1st, then the 2nd description is more likely to be correct by a factor of 1024. Alternately, there is a 1/1024 chance that the 2nd description is *not* the correct description of the data.
If you have lots of data, it's not unusual for a descriptive length to be thousands of bits shorter than the baseline description; meaning, that it's virtually certain that the new description is correct and that the new structure does not arise from random variation.
I haven't seen the data, but I assume that describing all galaxies in the universe using the newly described "clump" as a categorical structure gives a smaller descriptive entropy than describing all galaxies without the extra category of "clump".
Wouldn't it be interesting if we could see the same structure in a different direction! Then we would know we could see to the end of the universe.
Curious question for you physicists or arm-chair physicists, does this have any implications for inflation? I've read here and there that inflation would be problematic if there were large structures in the universe, because nothing would have had time to propagate the distance in the time required to be compatible with inflation, so does this bump up against that limit or break it?
"...I think the Microsoft hatred is a disease." - Linus Torvalds
Okay, what I meant was: what has a single quasar got to do with all this? It was not an appropriate image to use in this context.
Andromeda is perpendicular to the visible sky from Earth. This new collection of galaxies is parallel to the visible sky from Earth.
The concept of parallel makes no sense when referring the the "visible sky" which is roughly a half sphere, and a half sphere that varies according to one's position on the earth. The geocentric model of the universe has fallen into disfavor recently. You may want to consider some more modern conceptual models.
Sig Battery depleted. Reverting to safe mode.
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".
With a redshift of 1.3 this quasar group is probably close to the edge of the observable universe. What we see is from a time maybe some million years after the big bang. But at this time the universe was much smaller, so these quasars were much closer together than they are now. They are flying away from us since then into slightly different directions, and flying away from each other.
What I think this means is: We can not calculate the size of this group from the angular diameter and its distance, it has nothing to do with reality. The angular diameter comes from different directions that the individual quasars are flying away from us, not from actually being this large. We can only see this quasar group as it was billion years ago, and at that time it was much smaller. We don't know what it looks like now. Also our perception of the form of this group would be distorted if the directions that its components are flying is not just caused by a homogeneous expansion of the universe.
If you look at something that is very far away, you may see 'structures' that look like they are associated, but in fact it just looks that way to you, and some parts of it may be a lot closer than others. A good example of this is the so called constellations, which civilizations in the past identified as animal shapes, but in reality the stars forming them were in no way related, and once astronomers were able to detirmine the actual distance to some of the stars they found that some were much further away.
How far away (and long ago) is this 'group' of quasars? maybe its so far away (and long ago) that the universe hasn't expanded much, and we are seeing most of it.
Maybe our line of sight is being distorted by the gravity of the black holes involved.
Maybe its part of a giant sign (being constructed by the Magrateans) that says "This way to MilliWays"
I need to get some sleep.
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.
What force? That's the difficult question here, and the problem with your argument (an argument from ignorance). Of the four fundamental forces in nature, gravity has the longest range. But, structures larger than a supercluster are too large for gravity, because the metric expansion of the universe is a stronger "force" at that scale or larger, and necessarily tears apart any larger structures. That implies larger structures must have formed in process of the Big Bang.
The only known mechanism for creating large cosmic structures, baryon acoustic oscillations, is based on gravity. It tends to produce voids of 490 million light-years or smaller. The trouble is that you run out of possible fundamental forces when explaining the formation of larger structures. You literally need new physics to construct an object ten times larger than the limit given by known physics.
By the way, the size of the observable universe is 46.6 Mly, since the universe has expanded since then; the age of light and the current distance of its emitter are not interchangeable at cosmic distances.
If the "sameness" holds, presumably this pattern of clustered quasars should have similar relations in other parts of the sky.
(IANAPh)
My understanding of the concept of cosmological sameness is that you pick any patch of sky and the contents should be more or less the same- the same material content, the same patterns (or lack of patterns), etc. If there are corners of the universe which are substantially different from other corners, then that implies that our theories governing the early universe (which should produce a nice even, lumpless modern universe) aren't correct.
This observation implies that 1/20th of the universe is substantially different from the other 19/20ths. That's a lot of lumpiness. Unless further observations show that the rest of the universe contains similar arrangements, then early-universe theories would need to explain how 5% of the universe came to be different to the rest.