### Re: Does our solar system contradict the ''Big Bang Theory''?

Date: Tue Nov 24 18:04:18 1998
Posted By: John Dreher, Staff Astronomer, SETI Institute
Area of science: Astronomy
ID: 911783062.As
Message:

An interesting question that has several aspects.

Let's deal with the
easiest one first.  In a big, complicated system, like the Universe,
the motions can become quite complex.  Just look at the swirls
when you mix milk into coffee for a microcosmic example.  The swirls
go every-which-way.  Similarly, the "random" motions of the stars
and gasses will result in both large and small eddies that will
mask any underlying angular momentum left over from the Big Bang.
You would need to add up all the little pluses and minuses due
to these eddies on "small" scales (like our solar system, or
even our whole galaxy) before you could find out anything
about the underlying "universal" angular momentum distribution.
No one has done this yet (it wouldn't be easy!).

Another, very
interesting question is this: when an object spins, what is it
spinning with respect to?  The standard example is a pail
of water in an elevator.  Without looking outside, the fact
that the water sits down in the bottom of the pail tells you that
either 1) you are in a gravtitational field, such as that of the
Earth, or 2) you are accelerating in the "up" direction.  Turns
out that there is NO WAY to distinguish these two explanations,
and the theory of General Relativity basically says that they are,
in FACT exactly the same thing, despite appearances.

Going back to the pail:  If you now spin the pail, you will
observe the water starting
to spin as the pail drags on it, and then that the surface of the water
will rise up at the edges of the pail.  So you can tell, just from
soemthing you can see INSIDE the elevator, that the pail is spinning, just
from the shape of the surface of the water.  Suppose we spin the whole
elevator.  Although it would not be obvious, then, that the pail was
spinning, since the pail, and the elevator, and you would all be moving
together, yet you could still see the curved surface of the water, and
deduce that the elevator was spinning -- without having to look outside.
But how can that be?  What is the connection between the outside world and
the pail?  There is a mystery here.  A famous conjecture was made by
Mach, that if you could spin the ENTIRE UNIVERSE around the pail, rather
than spinning the pail, the surface of the water would behave in the
same way.  But it is demonstrably NOT true that just spinning some of the
local stuff will do it.  Is this conjecture true?  If it were, what
does it say about the connection between something local, like the angular
momentum of the water in the pail, and the rest of the universe?  The
relevance is this: what does it mean to even SAY that the entire Universe
is spinning?  With respect to what?

Finally, the "standard" models of the Big Bang have a total angular
momentum of zero.  We use these models because they are the simplest.  It
is possible to make "twisted" models with non-zero angular momentum, but
they are harder to deal with.  I don't think there are any very stringent
observational limits, however, on the total angular momentum of the
universe.  These days, it is very "fashionable" to use a variant of the
standard Big Bang model called "inflation."  I have no idea if "inflation"
would force the angular momentum of the universe towards zero or not.  But
then I am of the opinion that we just don't have enough data to have much
assurance that ANY of our basic cosmological theories is really correct.  I
anticipate that over the next couple of decades, however, we will get
enough new information from new observatories on the ground and in space,
that these cosomological theories can be put to the test.  Should be
exciting!

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