GALAXIES ARE FIXED; SPACE IS INCREASING...
Well, the "Big Bang" according to a theory of 1916,
by Einstein's theory of General Relativity, as worked out in more
detail by Friedman and others later on, the " Big Bang"
is not an expansion of matter into empty space. Every cosmologist,
every experimental scientist who is working this field uses the
same paradigm, the same picture. It is that the Big Bang is an
expansion of space, with the matter not moving. In fact the
math reflects this when you learn General Relativity and you do
this mathematically, these galaxies are fixed. They don't move;
they have fixed coordinates, and the expansion that takes place
is that even though they are not moving more space is appearing
between them. It is called the metric, the metric tensor is what
changes in General Relativity, and space is increasing between
these objects whose coordinates are not moving.
Sometimes this is illustrated in some of the elementary books
by having students imagine you are blowing up a balloon and you
have dots on the balloon and as you blow up the balloon the dots
get further apart from each other. That is actually an excellent
model. The trouble with it is that most students imagine that
the three dimensional space is space and that the galaxies are
somehow on this surface. What was really meant by that is to
imagine a two dimensional space, the surface, which is the entire
universe. This two dimensional surface is the universe, there
is no three dimensions, and that the size of the balloon is getting
bigger. In other words, the universe may be finite and if it
is the geometry is very similar to that of a balloon, at least
the three dimensional geometry in the sense that if you go out
that way and go far enough you come back to the same spot.
In the "Big Bang" what is happening is that space is
increasing, not that the objects are moving. Now this gives a
lot of people trouble to have space increasing. Another analogy
that is often made is I can stand here and you can stand there
and the distance it takes for me to get from me to you is a certain
amount. Someone can dig a hole between us, a ditch, and now it
is a longer distance as measured along the ground to get from
me to you. That is, even if we don't move the amount of distance
between us can change. The trouble is that the student says "yeah,
yeah, but that is only because you are not a bird, you can't fly,
you go down the ditch and up again." But the space between
us actually does increase, if you are confined to that surface.
In general relativity theory the same thing happens. If we don't
move, then a black hole is placed in between us, the distance
between us is vastly increases. To get from me to you it would
have to go way down into that space. It is a huge amount of space
crowded in around the black hole. It is not so bad if I go around
it but if I go through it, it is a very long distance. Space
is a flexible tangible thing in modern physics.
Now I talk about teaching this to kids. When I was six, I was
sort of mystified by this idea that space was so fixed, I mean
the distances between things seemed to change every year. The
hills got smaller, the apartment buildings got smaller. By the
time I was ten, there were no longer giants around, well that's
cause I had grown up. Everything was relative to me. I had
to be taught that space was fixed and that I was growing.