Cosmologic philosophy: Egnor on Big Bang, etc. (Introduction)

by David Turell , Thursday, September 23, 2021, 15:49 (1157 days ago) @ David Turell

George Ellis steps in:

https://iai.tv/articles/the-philosophical-problems-of-cosmology-auid-1883?_auid=2020

We can say nothing about what existed before the start of the universe, if it did have a start. The point is that if there is a beginning to the Universe, it is a start not just of space and time but of physics itself, for all the laws of physics are formulated as laws that apply within spacetime. The concept of “before the beginning” does not even make sense, for there was no “before” then – indeed there was not even a “then” then! A number of attempts to generate physical theories to account for the creation of the universe are pure speculation: the idea of physics laws holding then and being able to create the universe is not a coherent idea. Such theories always rely on some form or other of assumption of ordinary physics already pre-existing, except for Stephen Hawking’s ingenious “no boundary” idea, where the universe initially had 4 spatial dimensions (and hence no time), which changed to three space dimensions and one time dimension and started expanding. However, this depends on a particular quantum gravity theory (the Wheeler-de Witt equation) which is ill-formulated and untested, and we have no definitive way to test if it is correct or not. We have reached the boundaries of science, assuming as always that “science” relates to testable theories.

What is the origin of the arrow of time? What is the origin of the arrow of time that dominates everyday life given that the basic physics equations relevant for everyday life are time symmetric? It is usually accepted that this is due to special initial conditions at the start of the universe: it started off in a very special smooth state, which is a priori highly improbable. That then raises the issue of why such special initial conditions should exist. Many people assume that inflation solves this issue by smoothing out the universe by the end of inflation, but Penrose convincingly argues that this is not the case when one takes gravitational entropy into account. Inflation assumes substantial smoothness to start with, as this underlies the thermodynamic assumptions built into that theory. That is Penrose’s motivation for his Conformal Cyclic Cosmology, which has its own problems as mentioned above. Until we have a convincing theory of the origin of the universe, it seems we will just have to take a special starting geometry as a contingent condition (it could have been otherwise)

Comment: Please note Ellis is a major authority and he is a believer in God, not noticeable here in how he presents issues. An enormous discussion from which I picked one point.