🚀 go-pugleaf

In article <israel.725098854@unixg.ubc.ca> israel@unixg.ubc.ca (Robert B. Israel) writes:
>In <hassink.725064011@manning> hassink@cs.UAlberta.CA (Hassink Brian John) writes:
>>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 :)
>
Even if the nearby stars are more distant from us than the Sun, the night
sky should still be as bright as nearby stars, as long as the universe is
uniform and static, and infinite. The reason for not being so
is of course due to the expansion of the universe and its finiteness
and due to that the universe we see might be fractal.
The expansion red-shifts all light so
they appear dimmer than they should be. The fractal struture (of
dimension 1.2) means there are less stars and galaxies when further away.
Current observations only suggest a fractal up to 100 Mpc.
Therefore the universe is still homogeneous beyond this scale.

>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

The absorption length of star light totally depends on what the intestellar
medium is. It can be larger than 10^7 ly. It is an interesting toy model
of the universe though.
>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                            israel@math.ubc.ca
>Department of Mathematics             or israel@unixg.ubc.ca
>University of British Columbia
>Vancouver, BC, Canada V6T 1Y4

Sheldon Shi, AAC, University of Chicago