Far out cosmology: can't explain the Big Bang (Introduction)

by David Turell , Tuesday, January 04, 2022, 20:07 (1052 days ago) @ David Turell

Another review:

https://www.sciencealert.com/how-did-the-big-bang-explode-out-of-nothing-this-could-be-...

"...let's take a look at how "material" – physical matter – first came about. If we are aiming to explain the origins of stable matter made of atoms or molecules, there was certainly none of that around at the Big Bang – nor for hundreds of thousands of years afterwards.

"We do in fact have a pretty detailed understanding of how the first atoms formed out of simpler particles once conditions cooled down enough for complex matter to be stable, and how these atoms were later fused into heavier elements inside stars. But that understanding doesn't address the question of whether something came from nothing.

"So let's think further back. The first long-lived matter particles of any kind were protons and neutrons, which together make up the atomic nucleus. These came into existence around one ten-thousandth of a second after the Big Bang.

***

"The philosopher David Albert has memorably criticized accounts of the Big Bang which promise to get something from nothing in this way.

"Suppose we ask: where did spacetime itself arise from? Then we can go on turning the clock yet further back, into the truly ancient "Planck epoch" – a period so early in the Universe's history that our best theories of physics break down.

"This era occurred only one ten-millionth of a trillionth of a trillionth of a trillionth of a second after the Big Bang. At this point, space and time themselves became subject to quantum fluctuations.

"Physicists ordinarily work separately with quantum mechanics, which rules the microworld of particles, and with general relativity, which applies on large, cosmic scales. But to truly understand the Planck epoch, we need a complete theory of quantum gravity, merging the two.

***

"To truly answer the question of how something could arise from nothing, we would need to explain the quantum state of the entire Universe at the beginning of the Planck epoch.

"All attempts to do this remain highly speculative. Some of them appeal to supernatural forces like a designer. But other candidate explanations remain within the realm of physics – such as a multiverse, which contains an infinite number of parallel universes, or cyclical models of the Universe, being born and reborn again.

"The 2020 Nobel Prize-winning physicist Roger Penrose has proposed one intriguing but controversial model for a cyclical Universe dubbed "conformal cyclic cosmology".

***

"Conformal cyclic cosmology offers some detailed, albeit speculative, answers to the question of where our Big Bang came from. But even if Penrose's vision is vindicated by the future progress of cosmology, we might think that we still wouldn't have answered a deeper philosophical question – a question about where physical reality itself came from.

How did the whole system of cycles come about? Then we finally end up with the pure question of why there is something rather than nothing – one of the biggest questions of metaphysics.

***

"Endless new cycles are key to Penrose's own vision. But there is a natural way to convert conformal cyclic cosmology from a multi-cycle to a one-cycle form. Then physical reality consists in a single cycling around through the Big Bang to a maximally empty state in the far future – and then around again to the very same Big Bang, giving rise to the very same universe all over again.

"This latter possibility is consistent with another interpretation of quantum mechanics, dubbed the many-worlds interpretation. The many-worlds interpretation tells us that each time we measure a system that is in superposition, this measurement doesn't randomly select a state. Instead, the measurement result we see is just one possibility – the one that plays out in our own Universe."

Comment: lots of discussion going nowhere. We either really have something from nothing or we are back to Einstein looking for something eternal, but that is not an answer. What is first cause?