The discussion centers on the nature of time and space before the Big Bang, referencing the Hartle-Hawking no boundary proposal and the implications of general relativity (GR). Participants assert that according to standard cosmological models, time and space did not exist prior to the Big Bang, making the question of "what was there before" nonsensical. The conversation also touches on the Borde-Guth-Vilenkin theorem, which suggests that inflationary models cannot extend infinitely into the past, and the need for a theory of quantum gravity to address these cosmological questions.
PREREQUISITESAstronomers, physicists, cosmologists, and anyone interested in the fundamental questions of the universe's origins and the nature of time and space.
This sounds a lot like the Big Bounce.pines-demon said:I do not know if this has been brought out. There is this theory of Janus universes (as in Janus the god with two heads). Where basically from point ##t=0##, going forward in time gives a universe and rewinding back gives another universe. Similar to putting many gas particles in the corner of a box, you go forward in time the gas fills the box, you inverse the speed of all particles, the gas fills the box too.
I understand that he is referring to,DaveC426913 said:This sounds a lot like the Big Bounce.