From: julian@fraser.sfu.ca (Julian Shillcock)
Subject: Re: Are we privileged observers?
Keywords: universe,earth, paradox
Organization: Simon Fraser University, Burnaby, B.C., Canada
Date: Sun, 16 Aug 1992 21:29:10 GMT

kring@efes.physik.uni-kl.de (Thomas Kettenring) writes:

>Julian Shillcock writes:
>>["I-want-a-scientific-reason-for-my-beliefs" preliminary deleted]
>>Anyway the argument is: We can only observe those parts of the universe
>>where the light has had time to reach us. If we assume a finite age
>>of say 15 billion years or so then there is a "horizon" at 15 billion
>>light years distant from us beyond which we cannot observe any events.

>Yes, it's there (I think).

>>Now, dp the laws of physics as we know them here hold beyond this horizon?
>>[consequences deleted]

>This looks like a meaningless question if this horizon is the singulary it
>should be.  Analogous question:  do the laws of physics as we know them here
>hold north of the North Pole?

>There is no place "north of the North Pole", and there is no place "beyond
>this horizon".

JCS rsponds:
No, there is no singularity at this horizon, it only has reference to 
where we are in the universe. A being living closer to the horizon would not see
any difference, it is just that region in the universe that WE (on Earth)
cannot see. SO the question is not meaningless as there is plenty of
universe beyond this horizon, its light has not reached us yet.

>>We seem to need a meta-physics to tell us where the laws of physics hold.
>>It is made even worse if the laws themselves change in time as we then
>>have no idea what happens even in the parts of the universe we can observe.

>Huh?  If we can observe them, we can look there if the laws of physics hold.

No you can't, becuse you do not know how to interpret the observations.
An example: Suppose you measure the spectral shift of starlight, and find
it has a red-shift. Is this because the light is from a receeding source
or it is having to escape a strong gravitational field, or perhaps 
some unknown mechanism? We have to make a "uniformity" assumption
in order to interpret our observations. Another example: suppose
Newton's constant (G = 6.67 .10**-11 N.m**2/Kg**2 actually depends
on position so that it has a different value a few million light years
away? How can we discover this? Well, you can measure the period of
a double star and see if the accepted value of G works. But then you
need the masses to do this and how so you calculate them? You have to
assume a value for G, so you end up with a circular calculation.

We usually make the minimalist aasumption that the laws of physics
are the same everywhere for all observers, but this is an untestable
assumption within physics: rather it is the basis on which we do physics.
It is a matter of faith where the laws of physics apply ( hence my
statement about needing a meta-physics, ie, a more abstract theory 
that says where the current theories are valid).

The point of this post is to show that as far as we are concerned we
do occupy a privileged position in the universe. It is not privileged
in being a special space (there may be aliens who have a happy life
on a planet around another star and this argument would apply 
also to them), but it is privileged in that it restricts what WE can
do HERE and how we observe anythin elsewhere. Because of where we are
there are things we cannot observe and we REALLY do not know what happens
there: no theory of science can tell us, so we make assumptions (the
laws of physics do hold but we can't test them). Of course, why do
we care about such regions? Well, apart from the obvious scientific
response that they are there and we should think about them, they might
be relevant in changing the way we think about the world.
.
>>(Alsom if the universe is infinite then how come we are still here?)

>If trees are green then how come there are so many programming languages
>around?

>(That is, I couldn't find the point of your last question)

Oh, this was to preept someone who responds that there is no horizon
because the universe is infinite. Then we would have light from infinity 
coming towards us and there would be no paradox. But if the universe
is infinite we should have all died out long ago, unless there is  
some supernatural means of pumping energy into an infinite universe that
is constantly using it up

Hope that explains my position. I get irritated with people who 
bluster that we do not occupy a privileged place in the universe.
The sun is an ordinary star, etc, etc. As far as we know WE (the Earth
that is not humans) are the ONLY place with life. Period. Until we find 
evidence otherwise we should not build our science on "might-bes":
there are a hell of a lot of things that might be true in the universe,
but science is not science fiction.
Science explains what we can observe not what we cannot.          
(And please don't bring  up the probabilty arguments for life on other
planets, for all we know the universe might have to be as big as it is
just to get one successful living biosphere. You cannot get a probability
from one sample point).

Your privileged servant

julian