We discussed Week 3 of “Philosophy and the Sciences: Introduction to the Philosophy of Physical Sciences” the course from Edinburgh University.  We spent much of the time trying to understand Cosmology by going through the NASA primer at https://map.gsfc.nasa.gov/universe/  together, as we found Alasdair Richmond difficult to follow.  This was very fruitful, particularly when augmented by reading from Thomas Hertog’s book “On the Origin of Time” on Hawking’s later thoughts, which Dave and I really rated and recommended.  It is difficult to take on board that our universe was once allegedly millimetres in size (or was it - before spacetime emerged?); that it was unimaginably hot such that fundamental particles could not form and photons could not escape; that the matter we can detect is just 4% of the universe - not that much beside the 25% dark matter that holds the galaxies together and the 71%dark energy that drives the continuing expansion of the universe.  But it was then not so strange to go through the objections and cautions from the philosophy of science.  It is not possible to falsify these theories by experiment, because the one universe we have is by definition all there is.  That said, observations that alternative theories cannot encompass must be incorrect.  There may be other explanations and theories, some that meet Thomas Kuhn's five basic criteria that define a good theory: accuracy, consistency, scope, simplicity, and fruitfulness, and the existence of alternative feasible theories (the course offers modification of Newtonian dynamics) exemplifies underdetermination.