NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/sci/fractals/509

Internet Message Format | 1992-12-23 | 2.7 KB

Path: sparky!uunet!gatech!destroyer!cs.ubc.ca!unixg.ubc.ca!unixg.ubc.ca!israel
From: [e-mail] (Robert B. Israel)
Newsgroups: sci.fractals
Subject: Re: Fractal Universe
Date: 23 Dec 92 08:20:54 GMT
Organization: The University of British Columbia
Lines: 45
Message-ID: <[e-mail]>
References: <[e-mail]> <[e-mail]> <hassink.725064011@manning>
NNTP-Posting-Host: unixg.ubc.ca

In <hassink.725064011@manning> [e-mail] (Hassink Brian John) writes:

>[e-mail] (Richard Ottolini) writes:

>>In article <[e-mail]> [e-mail] writes:
>>>Does anybody know somewhat about the term "Fractal Universe"?
>>>I want to obtain references to sci. papers too.


>>It is in Mandelbrot's book on the Fractal Geometry of Nature.
>>The clumping of galaxies appears to be fractal.
>>It is also another way of resolving Olber's paradox that the night sky
>>in a sufficiently old universe should be as bright as the surface of
>>the Sun.


>Well, the earth would have to be equidistant from the sun and other nearby
>stars for this to be true. And if this were the case, all sorts of frightful
>things would happen to us :)

Actually, everything (including the surface of the sun) should be a lot
brighter.  Imagine that the universe was static (not expanding) and homogeneous
on a scale of, say, 10^7 light years.  Then there should be no net flux of
light through a flat surface of this size.  Take six such surfaces forming
a box.  Result: no net flux of light out of the box.   What happens to light
emitted by stars inside the box?  Well, it wanders around until it gets
absorbed.  Anything that's absorbing more energy than it's emitting will heat
up until it's at the same temperature as the ambient light (except for black
holes).  Eventually (and it wouldn't take very long on a cosmic scale, I
think) there won't be anything left that's cool enough to absorb more than
it emits.  It'll all be more or less at the same temperature as the
radiation, which will just continue to heat up as the stars pump out energy.
After a while the stars themselves heat up until they explode or run out
of nuclear fuel.

The point is, there has to be _someplace_ to get rid of all this energy the
stars are putting out.  The usual explanation is that the expansion of the
universe is creating more space to put it in.  Another possibility is that
the universe, with a fractal structure, could have a global matter density
of 0.
--
Robert Israel                            [e-mail]
Department of Mathematics             or [e-mail]
University of British Columbia
Vancouver, BC, Canada V6T 1Y4