.. _birch:

Now imagine in the 1960's Fred's idea of the continuous arrival of new
matter arriving in our visible universe, at exactly the rate required
to balance the observed expansion.

What would that universe look like?

This is the view Rourke provides.  He uses *de Sitter Space*, in which
pairs of geodesics eventually separate exponentially, in both forwards
and backwards time.

It is a natural first model for a universe, one with constant
curvature.  New galaxies are constantly arriving in our backwards
light cone, and do so highly redshifted as gamma-ray bursts.  It is
not new matter, spontaneously created, it has existed a very long
time, but has only just now entered our visible universe.  We will see
it until the end of time.

What if the waves we are seeing are not drammatic in-spirals of black
holes, but are the result of the same modulation of gravitational
waves generated by the central black holes of galaxies?

Earlier in the year I submitted a proposal to this conference in
Glasgow about general relativity and gravitational waves :ref:`birch`.



   Is there anything else?  Colin Rourke, on light.

   The CMB and gravitational waves should be in equilibrium due to the
   Rees-Sciama effect?

After submitting the talk, I realised the subject was a little more
complex than I had hoped, requiring not just de Sitter Space, but also
the model of galaxy evolution outlined in Rourke's work, where
galaxies are characterised by the size of their central black holes.

The release of data from the Dark Energy Spectroscopic Instrument
has provided ideal data to help determine the split between
cosmological and intrinsic redshift.

The key idea is that smaller black holes exhibit intrinsic redshift,
with light coming from close to the black hole.  As the central black
hole and galaxy grow the redshift diminishes and is negligble in a
full size galaxy.

The talk was not accepted, which was somewhat of a relief.  It has
taken me some time to understand what is going on with galaxy spectra.

I had also made the submission before I heard the very sad news that
Colin Rourke had passed away.

I decided I would still attend the conference, as it gave an ideal
opportunity to get the latest information on gravitational wave
observations and next generation detectors.  I was not disappointed.

.. automodule:: gotu.birch
    :members: