What We Cannot Know: Explorations at the Edge of Knowledge

by Marcus du Sautoy

The Big Bang singularity is a state of very low entropy. As the universe evolves, entropy increases – how can we move seamlessly into the next aeon and reset the entropy? This is why Penrose was unhappy that Hawking conceded the bet about black holes. In Penrose’s view, black holes are the mechanism for resetting entropy. All the entropy entering a black hole is lost or subtracted from the whole system, so that by the end of the aeon we are at low entropy again, because all the information has been lost in the plethora of black holes that populate the universe. This sets up the conditions for the next Big Bang. Even if the theory is correct, how can we ever dig back into the period that preceded our own Big Bang to test this or other theories? Is ‘before the Big Bang’ a no-go area? Penrose thinks not. Given that the two landscapes must match up, things that happened in the previous aeon should impact on our own. He believes that the bumping together of black holes towards the closing stages of the last aeon will have caused gravitational ripples that passed into our aeon. He compares it to a pond into which many pebbles have been thrown. Once the black holes or pebbles have disappeared, we will have a pattern of ripples that results from these interacting expanding circles. Penrose believes that this is something that we could look for in the cosmic microwave background radiation, the radiation left over after the Big Bang that started our universe. Although the fluctuatio...

Just for notes: penrose. multiple aeons, crossovers and singularities.