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View Full Version : Good news, universe not a fractal; WHY is this good news?



Buttercup
2012-Aug-23, 05:08 PM
From Twitter:
Good news! Universe not a fractal, study finds - Fox News

Yep, totally ignorant on this -- that's why I ask.

Why is this "good news"?

Shaula
2012-Aug-23, 06:26 PM
The maths is easier :D

Buttercup
2012-Aug-23, 07:59 PM
The maths is easier :D

Well I'm rotten at math :doh: so...I need a "regular" answer. :)

tusenfem
2012-Aug-23, 08:56 PM
FOX news tells you it is good, and FOX news is always right ........

Ara Pacis
2012-Aug-23, 09:07 PM
FOX news tells you it is good, and FOX news is always right ........

This is why homophonics is problematic.

Re: OP, perhaps it means that not everything repeats itself on larger scales, which I think would mean it doesn't have the problems of infinite regress or recursion (or less so), suggesting that there's a real limit and perhaps some absolutes.

Strange
2012-Aug-23, 09:34 PM
From: http://www.theverge.com/2012/8/23/3262329/universe-fractal-homogeneous-wigglez-dark-energy-survey

The finding means that astronomers are justified in measuring average quantities over large spatial volumes — there’s no hidden lumpiness messing up the math. This is good news, since a fractal structure at large scales would mean that "Einstein’s equations are being wrongly applied, and our understanding of things like dark energy could be deeply flawed," says the paper’s lead author, Morag Scrimgeour

What a great name. (And a nice photo of a vegetable in the article.)

Jeff Root
2012-Aug-23, 10:57 PM
Discovering that the Universe *does* have a fractal structure
would be too freaky for me to handle. It would be like finding
out that money grows on trees in back of the US Treasury.
(I've been in front of it-- no trees there.)

-- Jeff, in Minneapolis

Selfsim
2012-Aug-24, 12:22 AM
The distribution of galaxy clusters has a measured fractal dimension of ~2 (from the SDSS 2005 Survey), from a scale of 0.1 Mpc/h up to at least 20 Mpc/h. At larger scales, the dimension decreases less rapidly, until about 70 Mpc/h above which, it then flattens out up to about 100 Mpc/h.

This means that up to the galaxy cluster scale level, the measured universe has a fractal pattern.

Various theoretical models (invoking dark matter distributions) have been developed, in order to explain this pattern. Some involve different distributions of matter density profiles such as the cosmological N body models of dark matter, in which the formation of structure is driven primarily by gravity. "Halo models" are used to explain certain sampling biases, where the distribution of dark matter is described by a set of "halos", to which formation probabilities for different kinds of objects, are then attributed. This is in turn, is used to produce correlations with the measurements. These correlations however, tend to be very weak, and are not particularly convincing, which is a key area of investigation, having major implications on matter/dark matter interplay, when it comes to structure formation.

At the largest scales however, the appearance of structure seems to be homogenous (thus supporting the key working Cosmological Principle assumption).

It seems that this article reports on the most recent WiggleZ Dark Energy Survey, which provides yet more assurances of the correlation between the gravity driven models, and what we measure at the biggest scales.

Regards

PlutonianEmpire
2012-Aug-24, 01:13 AM
Discovering that the Universe *does* have a fractal structure
would be too freaky for me to handle. It would be like finding
out that money grows on trees in back of the US Treasury.
(I've been in front of it-- no trees there.)

-- Jeff, in Minneapolis
Why? What would be bad about having a fractal structure?

And don't go about dropping even more hints or such. :p

I can't get hints even if my life absolutely depended on it. :o

Selfsim
2012-Aug-24, 04:06 AM
Discovering that the Universe *does* have a fractal structure would be too freaky for me to handle. How do you feel about living in a galaxy cluster which is fractal down to 0.1 Mpc/h, then ?

Even more intriguing: How do you feel about having a fractal shaped brain and lung surface ?

Where's the 'freakiness', Jeff ?
It would seem to be more 'freaky' not to be part of some larger fractal (??)

I'm fascinated to understand more about why you have this view ...

primummobile
2012-Aug-25, 01:34 PM
I think the 'freakiness' is that you could zoom out forever and still see the same thing.

Jeff Root
2012-Aug-25, 02:08 PM
That's essentially it.

I don't have any problem at all with a limited degree of
"fractalness". I took "fractal" to mean that the distribution
of matter follows the same pattern from some level on up.
It makes sense that there would be a degree of fractalness
on all levels, but I wouldn't expect it to be the dominant
character of the distribution: I wouldn't expect it to be
"fractal".

Brains and lungs are not fractal over more than a few
iterations (three or four?), and only very roughly so over
that range. You'd have no trouble discerning which level
you were looking at from the appearance. Similar with
distribution of matter in the Universe. It can't really be
fractal. Just somewhat fractal-like.

-- Jeff, in Minneapolis

Ara Pacis
2012-Aug-26, 04:49 AM
Maybe it's because it sounds like an expletive. The Universe is Fract!