2) The Universe is observed to be expanding (so in the
past it was smaller).
The
Steady State Universe tried to get around this by supposing that new galaxies appear out of nowhere to fill the increasing
volume
(no more unreasonable than supposing that the Universe
appeared).
But then the past shouldn’t look different than the
present (on average)
3) The Universe was hot and opaque in the distant
past.
This
is proven by the thermal cosmic background radiation. Only if all space were opaque would all space be filled with thermal
photons (and their current temperature is
reasonable given the expansion factor)
4) A theory which supposes the Universe evolves in this
way can predict how the composition of
the Universe arose from the primordial fireball. These predictions are borne out well by the current observed composition.
It seems
inescapable that the Universe is only 10-20 billion years old (actually about 14
billion) and that it started at a set and knowable point of time.
The moment of Creation is now an empirical fact.