🚀 go-pugleaf

The standard line is this:
   The Universe is expanding.  It isn't just that galaxies are moving
   away from each other, but rather the fabric of the Universe is
   expanding.

In what way does it make sense to say the entire Universe is expanding?
One must have something to measure against.  The literature I've seen
is silent on this, but I think the default must be:

   1.  Assume the speed of light, gravitational constant, etc. are constant.
       Then if it takes longer for light to reach you, gravity has less
       effect, etc., then the universe is expanding.

This seems plausible, but I see two alternatives which should be 
indistinguishable:

   2.  Assume the Universe isn't expanding, but the speed of light,
       gravitational constant, etc., are decreasing in such a way that
       light takes longer, gravity has less effect, etc.

   3.  Assume the Universe isn't expanding, the speed of light and the
       gravitational constant are constant, but that time is speeding
       up (in the sense that it takes longer for gravity to accelerate
       an object, etc).  This has the same affect as (2), but provides
       a more elegant way to scale all the constants in the same way.

Is there any evidence which proves 1 over 2 or 3?